Venus or Mars for terraforming and colonisation?

[halfeye]

In the extremophiles thread Rater202 wrote:


I mean, we woulnd't know till we tried, but if we're gonna terraform something it'd be best to do Mars becuase it's relatively similar to Earth, more or less, just with less liquid water and oxygen and a lot colder.

There are certain lichens that might be able to handle mars, but honestly tossing those about in various parts of the martian surface would be more of an investment than a...

Like, I imagine that colonies would be very tight-run ship and stuff with contained buildings and eventually domes. spreading lichens and stuff to photosynthesize is much more a case of "leave this alone to see if it does anything and then maybe in a couple hundred years it will have spread enough that there will be breathable levels of oxygen in the atmosphere."

I imagine that colonies on venus are a pipedream.

...

But mars colonization is perhaps a topic for another thread.

It's relatively easy to block sunlight from a planet, we'll probably do it here within a century, because it will be cheaper than stopping polluting, personally I'm very much in favour of stopping polluting, but I don't think it's going to happen.

Once that's a known technique, applying it to Venus will be relatively trivial. Without the excessive temperature Venus is a much more attractive proposition than Mars is, there is an atmosphere that plants will love. Lack of water may be a thing but there are comets, and most of Earths water is not that useful, not that exporting it would make sense.

[Peelee]

Moon.

Unless you have a way to add planetary mass, the amount of atmosphere is just as important as the composition of the atmosphere, and if we're out of luck anyway on that front, may as well try closer to home.

[halfeye]

Moon.

Unless you have a way to add planetary mass, the amount of atmosphere is just as important as the composition of the atmosphere, and if we're out of luck anyway on that front, may as well try closer to home.

Oh yeah, Moon first for me (though I don't think terraforming is a go at this point), I'm just saying after that, for me it's Venus.

[factotum]

It's relatively easy to block sunlight from a planet

It is? How would you go about it, then? I don't think adding stuff into the atmosphere of Venus is going to be productive--the existing clouds already block something like 95% of solar radiation from reaching the ground, the reason it's so ruddy hot is because they block even more of the heat from leaving again. Putting something in between Venus and the Sun to block the sunlight seems like it would be a massive undertaking, because the object would have to be at least as big as the planet to provide a sufficiently large shadow and would also need to be able to manoeuvre to keep it in direct line between planet and star.

No, I agree with Rater on this--Mars is a far more tempting target for terraforming, because *adding* atmosphere is a lot easier than taking it away. Crash a few ice asteroids onto Mars to provide the source material and you're golden.

[warty goblin]

I don't really get the point of terraforming another planet. The expenses are catastrophic, the number of people's lives improved is few to none, and the timescales are way beyond anything we have any reason to think human planning can operate at. I mean hell, we as a species are at best barely capable of not messing up the climate of the planet we live on within the next century because doing so would be somewhat more expensive right now. This does not fill me with confidence that plans with runtimes in the hundreds to thousands of years are remotely in our capacity.

It seems like a solution in search of a problem, except the solution itself is a giant nest of incredibly hard problems.

[halfeye]

It is? How would you go about it, then? I don't think adding stuff into the atmosphere of Venus is going to be productive--the existing clouds already block something like 95% of solar radiation from reaching the ground, the reason it's so ruddy hot is because they block even more of the heat from leaving again. Putting something in between Venus and the Sun to block the sunlight seems like it would be a massive undertaking, because the object would have to be at least as big as the planet to provide a sufficiently large shadow and would also need to be able to manoeuvre to keep it in direct line between planet and star.

Not in the atmosphere. The object has to be big in at least two dimensions, but that doesn't mean it has to be big in the third, so it doesn't need to be massive. What I'm thinking of is a solar sail, more or less a parachute. There is a Lagrange point in between any planet and the sun, fly about around that and you are where you need to be.


I don't really get the point of terraforming another planet. The expenses are catastrophic, the number of people's lives improved is few to none, and the timescales are way beyond anything we have any reason to think human planning can operate at. I mean hell, we as a species are at best barely capable of not messing up the climate of the planet we live on within the next century because doing so would be somewhat more expensive right now. This does not fill me with confidence that plans with runtimes in the hundreds to thousands of years are remotely in our capacity.

It seems like a solution in search of a problem, except the solution itself is a giant nest of incredibly hard problems.

I think on the whole I agree, once we are up, there's not that much reason to come down again. However, if we are going to do it, then I think Venus is better than Mars.

[Yora]

Mine answer is a bit of a smartass answer, but also deals with the more fundamental question: It's neither.

The only way for humans to permanently live anywhere that isn't Earth is rotating space stations.

Mars and the Moon have very weak gravity that would cause severe long term health issues in adults, and no halfway ethical researchers would even contemplate the effects on developing children. The Moon will have to play a very important role as an industrial site, but neither place will be able to support a long-term population because of the gravity issue.
Theoretically, floating cities high in the atmosphere of Venus are thinkable, but since the atmosphere is not breathable, they still would have to be fully sealed. Simply putting them in space would be much easier. There are no practical benefits to make a space station hover in the atmosphere of Venus, except as a research post to study the atmosphere of Venus.

To make Venus anything that could be tolerable by humans would require removing over 90% of its atmosphere. I don't see any way how that could ever be accomplished.

If people really have to insist to live in a place that isn't Earth, space stations are better to planetary colonies in every way. You'd need all the same equipment that you'd need on another planet, but if you leave the thing in space instead of setting it down on a surface, you get a lot of benefits.

Planetary colonization has stopped being science fiction many decades ago. Now it is simply a nostalgic fantasy.

[Mastikator]

The upper atmosphere of Venus is not too hot and not too acidic so a "cloud city" could potentially work. The effort of terraforming Venus is astronomic beyond astronomic. A solar blocker may reduce the sunlight but that just makes it colder, not more habitable. Life needs sunlight to do the photosynthesis that we all depend on. Same is true for Earth. Continue to pollute and the pollutants build up indefinitely, space solar panels or not it inevitably lead to total ecological collapse along with total the end of civilization.

Some stragglers will remain though, humans are tough.

[halfeye]

The upper atmosphere of Venus is not too hot and not too acidic so a "cloud city" could potentially work. The effort of terraforming Venus is astronomic beyond astronomic. A solar blocker may reduce the sunlight but that just makes it colder, not more habitable. Life needs sunlight to do the photosynthesis that we all depend on. Same is true for Earth. Continue to pollute and the pollutants build up indefinitely, space solar panels or not it inevitably lead to total ecological collapse along with total the end of civilization.

Some stragglers will remain though, humans are tough.

Rats and cockroaches are tougher. Keeping them out of space will be tricky, on Earth they will just win, if it all goes bad.

[Tvtyrant]

Rats and cockroaches are tougher. Keeping them out of space will be tricky, on Earth they will just win, if it all goes bad.

The distant future will just be rats, crocodiles and cockroaches fighting for control of a dying Earth under a sullen red sun. And a sea full of benthic animals that don't notice anything changing haha.

[Fat Rooster]

For colonisation, Mars. For terraforming, Venus, for one simple reason; you need to. It would be perfectly possible to exploit the resources of Mars without a large scale terraforming effort, so why would we? At some point it may become worthwhile to spend the millennia or more required to terraform Venus (even if you remove all solar heating the ground will take an absurdly long time to cool, and even with artificial assistance weathering is going to take a long time to reabsorb all that CO2), but it is way off even being seriously considered. Sure you can do a cloud city, but why would you? You are severely restricted on what elements you have access to, particularly hydrogen. That makes getting off it again nearly impossible. A major consideration is that any colony will be highly dependent on Earth for a very long time, so needs to have something worth trading. I don't see what that is for Venus until the surface is accessible. Even then, the cost of getting it back from Venus will be prohibitive due to the high gravity and scarcity of hydrogen. Exploitation of Venus needs multiple game changing technologies to be viable.

I'm getting more convinced by a the viability of a Martian colony, mostly because it once had running water. That means gold deposits should exist that can give investors some return fairly quickly. Asteroids can have as much mineral wealth, but if it is not concentrated then retrieving it will be harder. Additionally an asteroid expedition will probably need almost everything taken with you, while Mars has carbon and nitrogen in abundance, while hydrogen is accessible with some effort. A Martian colony can expand rapidly on it's own, unlike most other places. It then works as a better base for further exploration, having less of a gravity well to escape.

An alternative worth considering (if you can deal with the radiation levels) is a Jovian colony system. Near the sun you are stuck with either being at the bottom of a giant gravity well, or no hydrogen (or both in the case of Venus). Further out you are typically energy starved. Io is the exception though. Instead of getting energy from the sun, it has massive energy availability because of tidal forces on it, while being close enough to Europa for volatiles to be available relatively easily. The volcanism on Io also probably drives significant fractionalisation of minerals, potentially making exploitation easier than on most moons (though not anywhere that had had running liquid at some point). You would probably still need some nuclear energy on Europa to split water into rocket fuel, but most of the industry can take place on Io. Fancy moving to Hell?

The Saturn system offers Titan, which has potential. It has good light element access, and good energy availability from strong prevailing winds. Very easy to escape as well, because we can already build jet engines capable of getting within touching distance of orbital speeds there. Fans of space planes should go here first. Lack of metal or rock might prove a problem though, unless you can build everything out of plastic. Life will struggle without additional nutrients. I couldn't find any information on whether there is any exposed rock or not, but I would guess not.

The ice giants might prove extremely useful if we really need helium. Nuclear powered aircraft bases that supply craft that use nuclear hydrogen engines to escape are probably the easiest* source of helium in the solar system, requiring nothing radical to work. A base on a moon of Uranus for managing the operation is the first option that really offers something that not even earth can offer. Like Saturn, it would need heavily artificially supported, but helium is one of the few elements that has no substitute. It may be justified.

* It isn't easy by any stretch, particularly docking a vehicle able to enter from orbit to another vehicle optimised for slow flight in an atmosphere. You almost certainly want the base to be a fixed wing aircraft from a reliability standpoint (though a hot air balloon might be doable), so it will probably be moving. I guess you could do a rocket hover with a hook setup. To make matters worse, even with nuclear hydrogen engines the escape system probably needs to be multi staged, so you will need to re-catch the booster every launch too!

[halfeye]

That means gold deposits should exist that can give investors some return fairly quickly.

Gold is not valuable enough to pay for the rocket fuel to get off Earth to go find it. Diamonds wouldn't be either, rocket fuel is really expensive. We're not going to find anything in space that's worth bringing back to Earth. What is worth having is the room. We can expand forever (or almost) out there.

[Mechalich]

Gold is not valuable enough to pay for the rocket fuel to get off Earth to go find it. Diamonds wouldn't be either, rocket fuel is really expensive. We're not going to find anything in space that's worth bringing back to Earth. What is worth having is the room. We can expand forever (or almost) out there.

Not exactly.

First rocket fuel is not necessarily expensive, it's rocket propellant that's the problem. Fuel powers the rocket, propellant gets thrown out the back as reaction mass to actually make it move. In a chemical rocket these are the same thing, but in essentially all other forms of rocketry they are separate. Nuclear fuel is in fact quite compact, durable, and potentially inexpensive under the right production conditions (variations on different forms of nuclear fuel and its production gets complicated).

Propellant is energetically expensive to haul around due to the tyranny of the rocket equation, but there are ways around this, particularly the utilization of in situ resources. In the case of asteroid mining, for instance, most asteroids have a fairly high water content and water - once accelerated by nuclear reactors - makes a fine propellant, so you can potentially construct engines on the asteroid using the asteroid itself to launch material back to wherever you want it to go.

Consequently there are conditions under which asteroid mining for certain resources does become economically viable, but they depend heavily on the specific constraints and the presence or absence of attendant technologies like space elevators.

More generally room, in terms of physical space, is probably not necessary. Even leaving aside the possibility of uploaded human existence, the need for space is driven by population growth. While the human population is currently engaged in rapid expansion, the growth rate has been falling since the late 1960s and is in active decline in almost all post demographic transition countries (at least in terms of native births, several nations, such as Canada, continued to experience population growth driven primarily by immigration). Even in a high estimate growth scenario, where the currently population of Earth doubles by some point in the 2100s, physical space would not be the strained resource (food and fresh water probably would be, but going into space doesn't alleviate those issues).

The real reason for space colonization is based on risk mitigation and extremely long-term habitability projections. the first is centered around the idea that as long as humans are stuck on one planet we remain vulnerable to an extinction level event wiping out the entire species. Settlement of even a small number of other locations would mitigate some of these threats - such as asteroid strike or lethal pandemic - though some of the really big ones require colonizing other solar systems (supernovae, gamma rays bursts etc.). The second is based on the by now fairly well established understanding that ongoing changes in solar luminosity will render the Earth uninhabitable in about a billion years when the oceans boil away. That's awfully far down the road though an honestly not something I feel needs be worried about for the present epoch.

[Nifft]

Mine answer is a bit of a smartass answer, but also deals with the more fundamental question: It's neither.

The only way for humans to permanently live anywhere that isn't Earth is rotating space stations.

Mars and the Moon have very weak gravity that would cause severe long term health issues in adults, and no halfway ethical researchers would even contemplate the effects on developing children. The Moon will have to play a very important role as an industrial site, but neither place will be able to support a long-term population because of the gravity issue.
Theoretically, floating cities high in the atmosphere of Venus are thinkable, but since the atmosphere is not breathable, they still would have to be fully sealed. Simply putting them in space would be much easier. There are no practical benefits to make a space station hover in the atmosphere of Venus, except as a research post to study the atmosphere of Venus.

To make Venus anything that could be tolerable by humans would require removing over 90% of its atmosphere. I don't see any way how that could ever be accomplished.

If people really have to insist to live in a place that isn't Earth, space stations are better to planetary colonies in every way. You'd need all the same equipment that you'd need on another planet, but if you leave the thing in space instead of setting it down on a surface, you get a lot of benefits.

Planetary colonization has stopped being science fiction many decades ago. Now it is simply a nostalgic fantasy.

Yeah.

Putting a colony on Mars seems pretty reasonable, as long as it's small enough to not bankrupt its supporters.

A wonderfully hilarious thing might be that we end up with practical, sustainable space habitats specifically because we need something profitable and productive to support some random madman's Mars colony.

[Bohandas]

How about the moon. We haven't even colobized the moon yet. Let's do that before jumping straight to Mars.

[Bohandas]

Gold is not valuable enough to pay for the rocket fuel to get off Earth to go find it. Diamonds wouldn't be either, rocket fuel is really expensive. We're not going to find anything in space that's worth bringing back to Earth. What is worth having is the room. We can expand forever (or almost) out there.
Luckily you woukdn't have to get off Earth, you'd just have to get off Mars, which has lighter gravity. You could drop it off without landing.


Mine answer is a bit of a smartass answer, but also deals with the more fundamental question: It's neither.

The only way for humans to permanently live anywhere that isn't Earth is rotating space stations.

Mars and the Moon have very weak gravity that would cause severe long term health issues in adults, and no halfway ethical researchers would even contemplate the effects on developing children. The Moon will have to play a very important role as an industrial site, but neither place will be able to support a long-term population because of the gravity issue.
Theoretically, floating cities high in the atmosphere of Venus are thinkable, but since the atmosphere is not breathable, they still would have to be fully sealed. Simply putting them in space would be much easier. There are no practical benefits to make a space station hover in the atmosphere of Venus, except as a research post to study the atmosphere of Venus.

To make Venus anything that could be tolerable by humans would require removing over 90% of its atmosphere. I don't see any way how that could ever be accomplished.

If people really have to insist to live in a place that isn't Earth, space stations are better to planetary colonies in every way. You'd need all the same equipment that you'd need on another planet, but if you leave the thing in space instead of setting it down on a surface, you get a lot of benefits.

Planetary colonization has stopped being science fiction many decades ago. Now it is simply a nostalgic fantasy.

Anybody who's willing to live in a space station isn't going to leave Earth in the first place. They're gonna stay on earth and build more and more cramped cities (or maybe live in submarines).

And where do you intend to get the resources to build and maintain these space stations anyway? You can't mine anything on a space station. You're either gonna have to get the resources from a planet, or you're going to have to go to the asteroid belt, which is basically made out of Kessler syndrome

[Nifft]

Rats and cockroaches are tougher. Keeping them out of space will be tricky, on Earth they will just win, if it all goes bad. The answer is space cats.


https://i.imgur.com/rh1Cq2g.jpg

They protect against all manner of pest.



Anybody who's willing to live in a space station isn't going to leave Earth in the first place. They're gonna stay on earth and build more and more cramped cities (or maybe live in submarines).
I'd live in an orbital habitat.


And where do you intend to get the resources to build and maintain these space stations anyway? You can't mine anything on a space station. You're either gonna have to get the resources from a planet, or you're going to have to go to the asteroid belt, which is basically made out of Kessler syndrome
Build them on the moon.

Then get a big old net and go Kessler fishing.

This works on Earth satellite debris and planetary rings and asteroid belts.

[Mastikator]

Then get a big old net and go Kessler fishing.

This works on Earth satellite debris and planetary rings and asteroid belts.

Wouldn't it be safer just to find a couple of asteroids and mine, smelt and build the stuff we need from them rather than create a Kessler Syndrome machine?

[Nifft]

Wouldn't it be safer just to find a couple of asteroids and mine, smelt and build the stuff we need from them rather than create a Kessler Syndrome machine?
Who talked about creating a Kessler Syndrome machine?

The poster I quoted seems to think the asteroid belt is already like that.

If you disagree with him, quote him (not me).

[akma]

It would be Mars before Venus, because we are much closer to building space stations on Mars then on Venus, and the hold on Mars would gradually increase (If humanity would ever colonize space).



It's relatively easy to block sunlight from a planet, we'll probably do it here within a century, because it will be cheaper than stopping polluting, personally I'm very much in favour of stopping polluting, but I don't think it's going to happen.

It is much cheaper to just have a house with good air conditioners, or moving to a different city. Even from country leaders perspective it is easier to improve current infrastructure, and even more easy to just ignore the issue.



More generally room, in terms of physical space, is probably not necessary. Even leaving aside the possibility of uploaded human existence, the need for space is driven by population growth. While the human population is currently engaged in rapid expansion, the growth rate has been falling since the late 1960s and is in active decline in almost all post demographic transition countries (at least in terms of native births, several nations, such as Canada, continued to experience population growth driven primarily by immigration). Even in a high estimate growth scenario, where the currently population of Earth doubles by some point in the 2100s, physical space would not be the strained resource (food and fresh water probably would be, but going into space doesn't alleviate those issues).

I don't think population growth would slow down greatly in the long term; some religions and cultures have a strong emphasis on procreation, so they'll just be a bigger percent of the population. Some leave those groups, but I don't think that would compensate for their growth rate.

[Eldan]

Two birds one stone: hollow out asteroids, pressurize, use as habitats. REfine asteroid material to build more structures. Use water asteroids to create oxygen and rocket fuel.

[Fat Rooster]

Gold is not valuable enough to pay for the rocket fuel to get off Earth to go find it. Diamonds wouldn't be either, rocket fuel is really expensive. We're not going to find anything in space that's worth bringing back to Earth. What is worth having is the room. We can expand forever (or almost) out there.

I don't know who is selling you rocket fuel, but they are ripping you off! :smalltongue: Elon Musk is on the record saying that the most expensive consumable on a falcon 9 is the helium used to back fill the tanks, and I would guess followed by the igniter fluid. Hydrogen can get expensive because it is such a pain to condense, but you don't have to put anything expensive through a rocket. Rocket fuels can get expensive because rockets are typically used in areas where expense is worth it. If a missile costs $100,000 already, paying $10,000 for propellant that gets 10% more performance than the $10 one makes sense.

The expensive bit of a launch is the disposable rocket, not inherent to the propellant. Most of the propellant is extracted cheaply from air! We would need to be able to bring back ~1/25000th of the mass of gold to pay for methane, and if we get to the point that that is the most expensive part of a launch then we are down to at least 12500kg of methane invested for each single kg of gold return. That is doable on Mars, particularly if the return equipment can be fabricated there.

Some asteroids do have water, but it is quite rare inside the snow line. Enough for people to a point, but not really enough to harvest propellant usefully. For wet asteroids you really are talking about trojans. At that point you might as well be in the Jovian vicinity, as it has everything. Being able to slingshot around Jupiter even makes getting things home easier. Also, how do you mine in micro gravity? Materials do not naturally collect on a surface. You cannot vacuum materials you break off up. Applying pressure with tools will make you just float away (requiring propellant), and getting an anchor requires is the same problem smaller. Things we take for granted here do not apply when harvesting asteroids. In contrast, Mars has everything earth has (and no oxygen, making welding easier!), just less of it. Mars would not require new techniques like asteroids do.

[Fat Rooster]

Anybody who's willing to live in a space station isn't going to leave Earth in the first place. They're gonna stay on earth and build more and more cramped cities (or maybe live in submarines).

There is precedent for it on earth in the highland clearances. At some point many people are not going to be able to afford to stay on earth (if we put appropriate value on our jewel of a planet), and it will be more economic to ship them off somewhere. They will have little choice in the matter. Once an alternative exists to staying here people will be forced out. Not a pleasant thought, but I think it will happen.


How about the moon. We haven't even colobized the moon yet. Let's do that before jumping straight to Mars.
No carbon on the moon, or nitrogen. That means that it's growth will always be dependent on imports. A lunar outpost will be a major stepping stone and tech proving ground for a Martian colony, but it will always be an outpost, rather than a true colony.


Wouldn't it be safer just to find a couple of asteroids and mine, smelt and build the stuff we need from them rather than create a Kessler Syndrome machine?
Getting between asteroids is hard. Without a planet to abuse the Oberth effect of you are talking about solar orbital speeds in regards to the delta-v requirements, and those make getting off earth look easy. Being able to use ion thrusters helps, but energy requirements to move any sort of bulk get prohibitive, especially if you are out beyond the snow line where solar power is weak.

[warmachine]

Mars. Things can survive the lack of melting surface temperature and lack of crushing atmospheric pressure. Plus you get to see the Sun, rather than some depressing twilight. That doesn't apply for floating cities above the clouds for Venus but the view would be nothing but white cloud.

[Peelee]

No carbon on the moon, or nitrogen. That means that it's growth will always be dependent on imports. A lunar outpost will be a major stepping stone and tech proving ground for a Martian colony, but it will always be an outpost, rather than a true colony.

Psh. There's gobloads of oxygen, which means we can just strip off some protons and make our own carbon and nitrogen. The Sovereign Moon ruled by the Great dragon Peelee says "hi."

[Aeson]

At some point many people are not going to be able to afford to stay on earth (if we put appropriate value on our jewel of a planet), and it will be more economic to ship them off somewhere.
Don't be ridiculous; even if we're just talking about 0.1% annual population growth that's still upwards of 7 million people to ship off planet every year at present-day population numbers, and if the planetary population keeps growing that's only going to go up. If being able to afford to live on Earth becomes a problem, we'll "solve" it the way humans have always "solved" such things: poverty, homelessness, social unrest, crime, and perhaps war, revolution, and societal collapse.

[Bohandas]

There's also the enormous ecological appeal of moving everyone off of Earth to consider

http://m.quickmeme.com/img/1d/1d85353e6b3891ee996be77eb4a4f8b2b9338e40f3daa413c8 0361c08d8bec3d.jpg

[Lord Torath]

In semi-related news:

Happy Martian New Year (https://www.syfy.com/syfywire/happy-martian-new-year)!

[LibraryOgre]

This conversation has me playing TerraGenesis again. Gonna beat Mars, then try to beat Venus, both as the Gaians.

[halfeye]

It is much cheaper to just have a house with good air conditioners, or moving to a different city. Even from country leaders perspective it is easier to improve current infrastructure, and even more easy to just ignore the issue.

Some major cities (London, New York, Chicago, Venice, Rome, Rio etc.) are due to go under, that's got to be billions or maybe even trillions of pounds or dollars of property flooded (skyscraper offices rather than housing, though the housing will flood too). I think people will start looking at spending millions before that happens.


The expensive bit of a launch is the disposable rocket, not inherent to the propellant. Most of the propellant is extracted cheaply from air! We would need to be able to bring back ~1/25000th of the mass of gold to pay for methane, and if we get to the point that that is the most expensive part of a launch then we are down to at least 12500kg of methane invested for each single kg of gold return. That is doable on Mars, particularly if the return equipment can be fabricated there.

Vetinari was right when he implied that everyone having tons of gold wouldn't mean everyone would be rich. It's pretty, and its resistance to corrosion is useful, but the main cause of its value is its rarity, the more you bring to Earth, the lower its value will fall, the same applies to anything which is mainly valued for rarity.

[Tvtyrant]

Some major cities (London, New York, Chicago, Venice, Rome, Rio etc.) are due to go under, that's got to be billions or maybe even trillions of pounds or dollars of property flooded (skyscraper offices rather than housing, though the housing will flood too). I think people will start looking at spending millions before that happens.



Vetinari was right when he implied that everyone having tons of gold wouldn't mean everyone would be rich. It's pretty, and its resistance to corrosion is useful, but the main cause of its value is its rarity, the more you bring to Earth, the lower its value will fall, the same applies to anything which is mainly valued for rarity.

There are lots of things you could bring that would be worth it though. Lithium and uranium are both used up by processing and relatively rare; bringing a few tons of lithium to Earth would literally cause a revolution in technology as batteries went from $20K to $2K.

[Nifft]

Some major cities (London, New York, Chicago, Venice, Rome, Rio etc.) are due to go under, that's got to be billions or maybe even trillions of pounds or dollars of property flooded (skyscraper offices rather than housing, though the housing will flood too). I think people will start looking at spending millions before that happens.

Property values are dropping already thanks to COVID-19.

Might be significantly easier than we'd thought to evacuate the immediate coasts in a timely manner.

[InvisibleBison]

bringing a few tons of lithium to Earth would literally cause a revolution in technology as batteries went from $20K to $2K.

Even with the most generous definition of few, it would take more than a few tons of lithium to produce this effect: in 2020, the global lithium production was 58,800 tons (https://www.mining.com/global-lithium-demand-expected-to-double-by-2024/).

[halfeye]

Property values are dropping already thanks to COVID-19.

They'll go up again if it ends though, and how much anyway? it would have to be 1% of the pre-covid value before moving out and rebuilding made sense.


Might be significantly easier than we'd thought to evacuate the immediate coasts in a timely manner.

It's not just the coasts, it's anywhere below the new sea level that the water can get to. Some coasts are cliffs, they'll be safe if they're higher than high tide.

[Tvtyrant]

Even with the most generous definition of few, it would take more than a few tons of lithium to produce this effect: in 2020, the global lithium production was 58,800 tons (https://www.mining.com/global-lithium-demand-expected-to-double-by-2024/).

Fair enough. It's still the most likely space-mining material. 58,000 tons is a tiny amount, less then the daily amount of iron produced for instance. The demand is also rising faster then the supply; if space can increase production by more then a marginal amount space colonization will be worth it (and also possibly be instrumental in fighting climate change.)

[halfeye]

Fair enough. It's still the most likely space-mining material. 58,000 tons is a tiny amount, less then the daily amount of iron produced for instance. The demand is also rising faster then the supply; if space can increase production by more then a marginal amount space colonization will be worth it (and also possibly be instrumental in fighting climate change.)

It's a tiny amount on Earth. The amount of ore you would need to process to get hold of that will be bigger. According to Wikipedia, it occurs in ores in which 10% Lithium is high. It seems that between sea water and ores there's plenty on Earh, it's just difficult to get it out of the mixtures.

[Yora]

I believe that concentrations in asteroids are assumed to be considerably higher. Metals on Earth generally had billions of years to oxidize, get crushed to powder, and be mixed up with other sediments before being spread over large areas by errosion.
Not really sure about how asteroids form, but there are many cases of meteorites that are really just giant lumps of iron and nickel. Before the iron age and the techniques to extract elemental iron from iron oxides, iron objects in Europe were made from meteorites that landed in oxygen poor swamps where they were safe from rusting into powder.
I think asteroid ores would generally be of considerably higher purity than those in the Earth's crust.

[LibraryOgre]

This conversation has me playing TerraGenesis again. Gonna beat Mars, then try to beat Venus, both as the Gaians.

Beat both. Now, I'm trying to terraform Mercury.

[Fat Rooster]

Vetinari was right when he implied that everyone having tons of gold wouldn't mean everyone would be rich. It's pretty, and its resistance to corrosion is useful, but the main cause of its value is its rarity, the more you bring to Earth, the lower its value will fall, the same applies to anything which is mainly valued for rarity.

Gold should not be more abundant on Mars than Earth (largely unproven assumption, but I can argue why I believe it if required) and Mars is much smaller than Earth. There is no reason to believe that Mars has enough gold reserves to crash the price. Assuming we can recover a couple of hundred tons that would mean returns in the billions range. That may be enough for a viable colony if the Starship works out as hoped. That wouldn't need any 'hopes of humanity' type blue sky thinking; it would just work as far as investors are concerned. That's what we need for a colony to be really viable. It is much harder to charge people for their impact on Earth when there is no alternative (which may make going to Mars the lesser of two negative options), but if a colony can be built based on things people will pay for, it works.

The other platinum group metals fall into this thinking too, and are arguably more useful.


There are lots of things you could bring that would be worth it though. Lithium and uranium are both used up by processing and not relatively rare; bringing a few tons of lithium to Earth would literally cause a revolution in technology as batteries went from $20K to $2K.

Both lithium and uranium are processing bound, rather than deposit bound. Good lithium deposits do exist, but even without them the price is capped by the price to recover it from sea water. Uranium is also not particularly expensive, relative to it's processing. Even if we used up all the uranium on earth, thorium is a viable substitute, and far more abundant. We would invest in thorium tech before bringing in more raw uranium from elsewhere.


I believe that concentrations in asteroids are assumed to be considerably higher. Metals on Earth generally had billions of years to oxidize, get crushed to powder, and be mixed up with other sediments before being spread over large areas by errosion.
Not really sure about how asteroids form, but there are many cases of meteorites that are really just giant lumps of iron and nickel. Before the iron age and the techniques to extract elemental iron from iron oxides, iron objects in Europe were made from meteorites that landed in oxygen poor swamps where they were safe from rusting into powder.
I think asteroid ores would generally be of considerably higher purity than those in the Earth's crust.

Initially, asteroids form from stuff coalescing. They would largely reflect the abundances cosmically, with a bias based on volatility depending on formation region. Then they form into planetoids, which are molten, and differentiate. Then those planetoids hit each other hard enough to break, or at least pass close enough to break up. M type asteroids are believed to be the remains of the core of planetoids.
Basically, we do not assume that asteroids formed in different compositions than planets. For late asteroids the difference is that the interior minerals may be present, or other concentrating mechanisms may have occurred in it's history. Lithium is not expected to concentrate anywhere other than salt flats.
Either way, are we expecting 1kg of asteroid lithium to be easier to access than 2,000 tons of sea water? Even if we find native lithium (highly unlikely, given it would react before anything else), we might be best ignoring it!

Ironically, we mostly consider oxidation state of elements with regard to how it affects volatility. Hydrogen is only accessible because it is usually oxidised to water. Even carbon is limited by it's volatility with oxygen (after hydrogen fails to make it volatile). Changing oxidation state is just a question of energy, and that is usually not your limiting resource, given how much energy it costs to transport materials between planets. Rusted to powder in a good place is far better than a pile of ingots in a bad one. It just takes that much energy to move stuff between planets.


I would love to say that it was worthwhile going looking for a whole host of different resources, but it actually isn't. Gold and the platinum group metals are the only ones that make economic sense with the current setup (and I'm glad they at least do). Unless we really put our money where our mouth is with regard to saving earth and pay to move people off it (they will not be willing; bankrupt people generally aren't), we will destroy it until it is worth moving. I do not like that outcome.

[halfeye]

Gold should not be more abundant on Mars than Earth (largely unproven assumption, but I can argue why I believe it if required) and Mars is much smaller than Earth. There is no reason to believe that Mars has enough gold reserves to crash the price.

I'm told that 99.9% of Earth's gold is in its molten core, the core of Mars is frozen, so maybe it could be mined.


The other platinum group metals fall into this thinking too, and are arguably more useful.

They would have to be found, there was a gold rush in California, because this stuff isn't spread thinly everywhere.


Rusted to powder in a good place is far better than a pile of ingots in a bad one. It just takes that much energy to move stuff between planets.

This is exactly what I'm saying about gold.


Unless we really put our money where our mouth is with regard to saving earth and pay to move people off it (they will not be willing; bankrupt people generally aren't), we will destroy it until it is worth moving. I do not like that outcome.

Moving people off Earth is generally speaking not going to happen. I think that there will be more people off Earth than on it in 10,000 years, possibly as little as 1,000 years, but the number of people who will have left Earth for space in that time will be millions at most, probably only single digit thousands (supposing we don't discover free anti-gravity, which we almost certainly won't). There are much cheaper but much worse ways to get rid of excess people.

[factotum]

I'm told that 99.9% of Earth's gold is in its molten core, the core of Mars is frozen, so maybe it could be mined.

Even if that's true (I have no idea if it is or not), digging a hole more than 3000km deep is a ridiculously major undertaking even with no geological issues to worry about. For comparison, the deepest hole we've ever dug here on Earth is a mere 12km deep or so. Not to mention, to dig this pit on Mars we have to build a bunch of construction equipment that can't rely on combustion engines, ship them forty million kilometres, land them softly enough on the planet to not break them and only then can you start work.

Gold is valuable, no question about that, but it's nowhere near valuable enough to make an operation like that financially viable. Especially since, once you've found your mother lode of gold in the Martian core, the price of gold suddenly nosedives because the availability of it has gone *way* up.

[Nifft]

Even if that's true (I have no idea if it is or not), digging a hole more than 3000km deep is a ridiculously major undertaking even with no geological issues to worry about. For comparison, the deepest hole we've ever dug here on Earth is a mere 12km deep or so. Not to mention, to dig this pit on Mars we have to build a bunch of construction equipment that can't rely on combustion engines, ship them forty million kilometres, land them softly enough on the planet to not break them and only then can you start work.

Gold is valuable, no question about that, but it's nowhere near valuable enough to make an operation like that financially viable. Especially since, once you've found your mother lode of gold in the Martian core, the price of gold suddenly nosedives because the availability of it has gone *way* up.

What you do is you land something on Mars at sufficient velocity to disperse the huge gravity-sink into smaller, more easily managed chunks.

Then you could even get aspirational space-habitat dwellers like myself to "colonize" the place.

[Yora]

When the Earth was completely molten, all the heavier elements would have sunken to the bottom and all the lighter elements to the top. Which is why the rock on the surface is mostly silicon oxide and aluminium oxide. The core is only "mostly iron" because iron is extremely abundant in the universe. The center of the iron core should have a smaller core of heavy metals.
All the metal we have on the surface now are from asteroid impacts after the crust had solidified, preventing them from sinking down.

The same should be true for all planets, but even when they are tectonically inactive, the pressures at the core would be tremendous. Even if you could bore a drill that far down, it would be impossible to keep the hole from getting squeezed shut immediately. Elements in the cores of planets are inaccessible in any plausible way.

[Fat Rooster]

I'm told that 99.9% of Earth's gold is in its molten core, the core of Mars is frozen, so maybe it could be mined.

That would... Wait... (Frantically googles martian core temperature)... 1500K. That would be extremely difficult, but might just be possible.



Even if that's true (I have no idea if it is or not), digging a hole more than 3000km deep is a ridiculously major undertaking even with no geological issues to worry about. For comparison, the deepest hole we've ever dug here on Earth is a mere 12km deep or so. Not to mention, to dig this pit on Mars we have to build a bunch of construction equipment that can't rely on combustion engines, ship them forty million kilometres, land them softly enough on the planet to not break them and only then can you start work.

Gold is valuable, no question about that, but it's nowhere near valuable enough to make an operation like that financially viable. Especially since, once you've found your mother lode of gold in the Martian core, the price of gold suddenly nosedives because the availability of it has gone *way* up.

The difficulty with deep drilling is temperature. With a well designed drilling fluid you don't have pressure differential problems, but it is still pretty hot. We are not going to be mining the core any time soon, but it is surprisingly feasible without breaking physics (though closer to oil drilling than normal mining). That is a completely different question than whether we can make a Martian colony viable in the near term though.

As for a colony being financially viable, you can run the numbers. An extra 100 tons of gold would not crash the price, and even if it drops a bit you would still be talking ~$5billion. The question is whether you can set up a colony that can recover that much gold for $5billion. Don't get me wrong, that is 2 orders of magnitude better value than current space projects expect, but the starship may be able to deliver that level of performance. To crash the price you would need to be bringing back comparable amounts to what we have recovered from Earth, and there is simply not that much easily accessable gold on Mars. Mars will have had to have found something else to do in the mean time, but given it has everything required to be self sustaining, trade is only required for 'beer money'. We just need to justify the setting up of a self sustaining colony. It does not need to be reliant on gold money for ever, unlike asteroid mining.

The phrase 'motherload' is from gold prospecting because large deposits near the surface that are extremely easy to recover do exist. A gold recovery effort can literally consist of a guy with a shovel and a pan, and even on Mars you would not need vastly more complicated equipment. That is an ideal industry for a fledgling colony (and why it drove migrations historically). Gold is not currently valuable enough to justify it, but beats out the alternatives by a mile and is not nearly as far off being economic as you seem to think.

Edit: Oh, right. You were talking about core mining with regards to gold justifying it. Got to agree, I don't see why we would ever need that much gold. If you are even considering it though you are probably more interested in the catalytic elements though, and will already have the infrastructure set up to deal with them. Gold is only really relevant as the fastest return on investment from colonisation requiring very little infrastructure (and hence a small colony) to make work.


When the Earth was completely molten, all the heavier elements would have sunken to the bottom and all the lighter elements to the top. Which is why the rock on the surface is mostly silicon oxide and aluminium oxide. The core is only "mostly iron" because iron is extremely abundant in the universe. The center of the iron core should have a smaller core of heavy metals.
All the metal we have on the surface now are from asteroid impacts after the crust had solidified, preventing them from sinking down.

The same should be true for all planets, but even when they are tectonically inactive, the pressures at the core would be tremendous. Even if you could bore a drill that far down, it would be impossible to keep the hole from getting squeezed shut immediately. Elements in the cores of planets are inaccessible in any plausible way.

Not quite. There is quite a lot of chemistry that means elements do not differentiate like that. See the Goldschmidt classification (https://en.wikipedia.org/wiki/Goldschmidt_classification). There is no lump of gold at the middle of the iron, it is spread fairly evenly throughout it. Nearer the surface there are many interesting mechanisms that separate different elements, but I am unaware of any suggestion that there are such processes going on in the core. If there had been we should be some highly enriched meteorites that we just don't see.


Frankly if we are going to be doing any core drilling, Mercury would be much more tempting. The core is closer (half to one third the distance) and cooler, and the gravity is slightly weaker. Surviving there might be more challenging, as you would be reliant on imported carbon and nitrogen, but the energy availability might help with viability.

[factotum]

Frankly if we are going to be doing any core drilling, Mercury would be much more tempting. The core is closer (half to one third the distance) and cooler, and the gravity is slightly weaker. Surviving there might be more challenging, as you would be reliant on imported carbon and nitrogen, but the energy availability might help with viability.

Wouldn't we be better off just finding an asteroid that used to be from somewhere in the deep levels of a planet and mining that instead? Far easier than any sort of planetary core extraction.

[Fat Rooster]

Wouldn't we be better off just finding an asteroid that used to be from somewhere in the deep levels of a planet and mining that instead? Far easier than any sort of planetary core extraction.

Oh yeah. I was sort of taking it as a given that we have exhausted all the even remotely easily accessible supplies in the solar system before moving on to breaking up the planets*. You don't start core harvesting if you just need a little of something. This is type ~1.3 civilisation type stuff. Much higher and we would just be stripping off the entire mantle before using all the core (far simpler than working underneath a collapsing mantle. Much lower and there is no point. I was just amazed that the physics of it works at all (the Martian core is cool enough that a drill could be created without resorting to unobtanium, though it is obviously extremely difficult)!

Interestingly, you run into a similar 'why colonise?' problem again around that time. What will push us to leave our nice cushty solar system while we can still dismantle Mercury? Will the paltry resources that sit on the surfaces on planets and asteroids be able to justify colonisation while the Mercury core drill can recover the same stuff (no way you can send a 'full' rig to a fledgling colony, and it would take too long to bring returns anyway)?

* Removing any significant portion of the core while it is still inside is probably going to cause issues. You would have to go quite far before things go full Krypton, and the risk is that the Mantle gets destabilised and suddenly turns over, flooding the crust with fresh lava, rather than exploding, but it might get messy if you are doing it at scale. The energies we are talking about are relevant even when talking about the temperature of the bulk of a planet, and only having a single point at the surface for cooling limits things. Far easier to strip mine if you want that much material, and only harvest the core when you get there. That gives you the whole planet surface area for cooling, avoiding energy concentration.


Edit: Oh, and I just thought of a reason a type 1.3 civilisation might want quite so much gold: It has great x-ray properties, which might make it an important dopant in drive propellant and fuel. Let's say you have a 100 million degree plasma core, and you need to transfer that energy into your reaction mass in a way that gets it's temperature up to the million degrees range. You could do that by harvesting the energy and then putting it in with other equipment, but any inefficiencies would mean you would need to get rid of a vast amount of waste heat, and you are not putting enough propellant through to dump it into that. You would be limited to low thrust or efficiency by cooling considerations. An alternative is to rely on direct x-ray heat transfer, and gold is great for boosting the absorption and emission. Gold would help a lot with that.

[Lord Torath]

The difficulty with deep drilling is temperature. With a well designed drilling fluid you don't have pressure differential problems, but it is still pretty hot. We are not going to be mining the core any time soon, but it is surprisingly feasible without breaking physics (though closer to oil drilling than normal mining). That is a completely different question than whether we can make a Martian colony viable in the near term though.The problem with deep drilling on Earth is temperature. On other similarly-sized planets with frozen cores, the plasticity of the planet is the problem. You know how we can't build a space elevator from the surface because all the materials we currently have will collapse under their own weight? The extreme pressures as you approach the core of Mars will make it impossible to keep your bore hole open.

[Fat Rooster]

The problem with deep drilling on Earth is temperature. On other similarly-sized planets with frozen cores, the plasticity of the planet is the problem. You know how we can't build a space elevator from the surface because all the materials we currently have will collapse under their own weight? The extreme pressures as you approach the core of Mars will make it impossible to keep your bore hole open.

I reiterate: With a well designed Drilling fluid hydrostatic pressure can be eliminated as a problem. You tailor the fluid to be similar density to the surrounding material and have pressure bulkheads with pumping stations periodically. You will need them anyway to keep flow up, but they can also correct the differences that will build up as you go deeper. At each point the pressure within the borehole can be maintained at the same level as outside, up to a tolerance that does not depend on depth, say a couple of dozen bar. That is not enough to make rock behave plastically, and can go either direction anyway.

Potentially you could put positive pressure inside the borehole to the point that you are actually using it to expand your borehole, relying on that plasticity to cause material to move out of the way, rather than be cleared out the top. If your drilling fluid is 30kg per cubic meter denser than the surrounding material, every kilometre would add 1 bar to the overpressure inside the borehole. Put a spike on the front and 'apply percussive pressure spikes' (hit it with a hammer), and the internal pressure can do most of the work. Essentially your borehole is sinking on it's own, with a little help to overcome the remaining rigidity.


What might be a problem is any remaining movement in the mantle, deflecting your borehole and breaking it over time. Mars and Mercury are pretty much done with their convection I think though, so that shouldn't be a problem there.

[Radar]

Putting the reasonability of colonizing Mars, I want to drop an article concerning the sustainability of a colony. As it turns out, bacteria could grow in Mars-like conditions if the proportion between N2 and CO2 could be changed. Since the total pressure could still be equal to the typical Mars atmosphere, this is not that big of a technical problem. The article in question (https://www.frontiersin.org/articles/10.3389/fmicb.2021.611798/full).

[Fat Rooster]

Putting the reasonability of colonizing Mars, I want to drop an article concerning the sustainability of a colony. As it turns out, bacteria could grow in Mars-like conditions if the proportion between N2 and CO2 could be changed. Since the total pressure could still be equal to the typical Mars atmosphere, this is not that big of a technical problem. The article in question (https://www.frontiersin.org/articles/10.3389/fmicb.2021.611798/full).

Nice, though you should note they are not talking about Martian pressures, just low pressures. We would still need a pressure vessel for this. Still a big deal, as a 1/10th atmosphere requires 1/10th of the structural strength that a full atmosphere does, but you are still 20x away from Martian pressure. Party balloon material can hold about 1 bar for reference, meaning you could inflate a dome 3m across using the same material that would give us a 30cm balloon (though obviously a 100x more of it). Being able to bring a 3m dome for the mass of a bag of party balloons would be a big deal. That is probably the pressure range you would want to use anyway, as it gives you inflatable structures that are entirely tensile without being very heavy. It might make more sense to use .3 bar, as that would allow people to operate with just breathing gear, but if it is not requiring frequent work and needs an EVA to get to anyway why let people be a consideration. Probably safer not to let people in without a suit anyway, as it would also allow us much better safety margins, and better protections. If something goes wrong you can vent the gas, rather than risk the structure getting damaged. Can't do that if there might be a person in there.

One of the early production facilities probably wants to be polythene, for building new facilities (probably polytunnels, rather than domes. Avoids needing to fabricate double curves to a large extent). They would probably need to import dopants for quite a long time, but if you are just importing additives rather than bulk material you can expand much more cheaply than bringing everything in.

Incidentally, I lol-ed at the section talking about the viability of feeding other micro-organisms the mass produced. It jumped out at me as one of those translation things where they compare what is in the paper to what actually happened:

"We then tested the viability of feeding other micro-organisms" = "Our sample then went mouldy"

With more reading it sounds like this was more deliberate than that, but made me laugh anyway.

[halfeye]

For mining I would go to the asteroids, there are enough small ones that anything we want is probably within reach without a silly gravity well to climb out of afterwards, though I still think it probably isn't worth it to bring stuff back to Earth, but it will be worth it not to have to lift stuff (particularly metals) to Earth orbit.

I still think it's going to be easier in the long run to get Venus to Earth standard than Mars. For a start the mass is nearly perfect as it is. Plants love CO2. There would need to be water, but there's hydrogen in H2SO4, and we have sulphur loving bacteria.

The current temperature is a problem, but the pressure really isn't, it's that high about 3000 ft below the surface of the sea, and we know there's all sorts of life down there, the Marianas Trench is over ten times that deep and there's life there. When the plants have eaten most of the CO2, most of that pressure will be gone and we can live there ourselves if we want, but finding plants that could live there now, if the temperature was right, won't be difficult.


The pressure of seawater at a depth of 33 feet equals one atmosphere. The absolute pressure at 33 feet depth in sea water is the sum of atmospheric and hydrostatic pressure for that depth, and is 66 fsw, or two atmospheres absolute. For every additional 33 feet of depth, another atmosphere of pressure accumulates.

https://en.wikipedia.org/wiki/Metre_sea_water

[factotum]

It's getting green plants to live in the 500C hellhole that is Venus' surface that's the real problem there, as you acknowledge. Unless we can devise some sort of algal bloom that can float in the upper atmosphere, where temperatures and pressures are more bearable--although then you have the issue that CO2 is a fairly dense gas and will tend to stay low down even as you convert the upper atmosphere, so you'd probably still have the surface level hellhole to contend with even once your magic algae had done their job.

[Yora]

To make Venus habitable, the first step is to create a giant system of pipes and pumps that siphons off 99% of the atmosphere and blows it into the sun or somewhere else where it's not going to just be pulled back to Venus.
Once air pressure at the surface is down to 1 or 2 bars, we can start thinking about regulating temperature and making the air breathable.

[Forum Explorer]

To make Venus habitable, the first step is to create a giant system of pipes and pumps that siphons off 99% of the atmosphere and blows it into the sun or somewhere else where it's not going to just be pulled back to Venus.
Once air pressure at the surface is down to 1 or 2 bars, we can start thinking about regulating temperature and making the air breathable.

I remember reading somewhere that it's possible to strip or change Venus' atmosphere by bombarding it with asteroids of sufficient size. Of course, that involves moving an asteroid the size of the moon around which has it's own problems. Like I think you need to have invented some sort of anti-matter engine to get enough energy to move objects that size.

[Nifft]

I remember reading somewhere that it's possible to strip or change Venus' atmosphere by bombarding it with asteroids of sufficient size. Of course, that involves moving an asteroid the size of the moon around which has it's own problems. Like I think you need to have invented some sort of anti-matter engine to get enough energy to move objects that size.

If the asteroid is made of rocket-fuel -- for example, water -- then you wouldn't need anti-matter to accelerate it sufficiently.

I remember reading a proposal to dump half the water of Europa on Venus, and the other half (along with all the non-water mass) onto Mars, minus whatever water would be used as fuel.

[halfeye]

To make Venus habitable, the first step is to create a giant system of pipes and pumps that siphons off 99% of the atmosphere and blows it into the sun or somewhere else where it's not going to just be pulled back to Venus.
Once air pressure at the surface is down to 1 or 2 bars, we can start thinking about regulating temperature and making the air breathable.

I strongly disagree. Most of the pressure is due to CO2. Plants convert CO2 to sugars.

In my view, the main problem is the temperature. We need to check there isn't anybody alive down there, but if there isn't, blocking all the sunlight ought to do the job inside a couple of hundred years or maybe much less.

[Radar]

To make Venus habitable, the first step is to create a giant system of pipes and pumps that siphons off 99% of the atmosphere and blows it into the sun or somewhere else where it's not going to just be pulled back to Venus.
Once air pressure at the surface is down to 1 or 2 bars, we can start thinking about regulating temperature and making the air breathable.
Those things are interconnected as lower temperature would also result in a condensation of a lot of the heavy substances. Since Venus conditions are a result of a runaway greenhouse effect, tipping the scales in the other direction could potentially have an inverse effect, but it would require action on a properly massive scale. If we can go wild, I would ponder on obscuring the Sun with a miniature Dyson swarm. It would not even have to completely cut off the light to give results. It is still more fiction than science though.

[Forum Explorer]

If the asteroid is made of rocket-fuel -- for example, water -- then you wouldn't need anti-matter to accelerate it sufficiently.

I remember reading a proposal to dump half the water of Europa on Venus, and the other half (along with all the non-water mass) onto Mars, minus whatever water would be used as fuel.

Or just frozen hydrongen. That would react with the Carbon Dioxide to create water and lower the amount of CO2 that way. So basically throwing a giant frozen moon at Venus would be a good first step. The blast would simultaneously remove some atmosphere while also providing a source of hydrogen needed to convert even more of the atmosphere into something else.

[Lord Torath]

Or just frozen hydrongen. That would react with the Carbon Dioxide to create water and lower the amount of CO2 that way. So basically throwing a giant frozen moon at Venus would be a good first step. The blast would simultaneously remove some atmosphere while also providing a source of hydrogen needed to convert even more of the atmosphere into something else.It will also dump a truly staggering amount of kinetic energy at the planet, which will relatively rapidly be converted to heat.

[Forum Explorer]

It will also dump a truly staggering amount of kinetic energy at the planet, which will relatively rapidly be converted to heat.

I'm pretty sure that'll be small potatoes compared to the heat we have to shed in the first place.

[factotum]

Or just frozen hydrongen. That would react with the Carbon Dioxide to create water and lower the amount of CO2 that way.

Getting just carbon and water out of that reaction seems extremely unlikely. You'd probably end up with complex carbohydrates, so maybe you'd cover the surface of the planet with a crust of sugar!

[Nifft]

I'm pretty sure that'll be small potatoes compared to the heat we have to shed in the first place.

One small potato at sufficient velocity could vaporize the Earth.


Getting just carbon and water out of that reaction seems extremely unlikely. You'd probably end up with complex carbohydrates, so maybe you'd cover the surface of the planet with a crust of sugar!

Don't tell Galactus that we have a frosted planet.

[Forum Explorer]

Getting just carbon and water out of that reaction seems extremely unlikely. You'd probably end up with complex carbohydrates, so maybe you'd cover the surface of the planet with a crust of sugar!

Sure, there'd be a bunch of byproducts, that's not really a bad thing when the goal is to remove as much CO2 as possible from the atmosphere. I think one of the proposals suggested getting a bunch of minerals launched into Venus as well to cause other reactions.


One small potato at sufficient velocity could vaporize the Earth.


Not really. Even at lightspeed, it would only cause a massive fusion explosion. Which might wipe out a city if you're unlucky, but that doesn't matter one whit to the Earth as a whole.

Now admittedly, I'm talking about throwing an entire moon's worth of matter, which is a lot more massive than a potato. But on the other hand, there's no reason to even try and get it to a percent of lightspeed. Furthermore we don't really care about any damage done. So long as we remove enough CO2 for heat to actually begin dissipating, any added heat is ultimately irrelevant.

[Radar]

Incidentally, I lol-ed at the section talking about the viability of feeding other micro-organisms the mass produced. It jumped out at me as one of those translation things where they compare what is in the paper to what actually happened:

"We then tested the viability of feeding other micro-organisms" = "Our sample then went mouldy"

With more reading it sounds like this was more deliberate than that, but made me laugh anyway.
Upon rereading it reminded me of how to translate standard academic paper phrases (http://phdcomics.com/comics/archive.php?comicid=405). :smallsmile:

[Eldan]

Don't forget "At this stage, the sample size was reduced" means, at least in botanical research "And then one of my student assistants kicked over one of the pots while watering and spilled everything".

[Yora]

I strongly disagree. Most of the pressure is due to CO2. Plants convert CO2 to sugars.
So the solution is somehow cover the entire planet in a 50 meter thick layer of sugar.

[factotum]

Not really. Even at lightspeed, it would only cause a massive fusion explosion. Which might wipe out a city if you're unlucky, but that doesn't matter one whit to the Earth as a whole.


If you actually did manage to get a potato to lightspeed (breaking a number of laws of physics to do so) then it would literally have infinite kinetic energy and would entirely destroy the Earth--and the rest of the universe as well, but let's not worry too much about that part. Assuming you actually mean some "arbitrarily close to lightspeed" value then you're still wrong, because you can literally keep adding kinetic energy to make the thing get closer and closer to lightspeed without any upper limit. If youure just thinking "Well, it's 1/2 m * v ^2 and we know m and v, so..." then you're forgetting mass dilation, which means the mass of the potato increases the closer to lightspeed it gets.

[Peelee]

If you actually did manage to get a potato to lightspeed (breaking a number of laws of physics to do so) then it would literally have infinite kinetic energy

The Prandtl-Glauert singularity says "hi".

Seriously, no matter how good the math is, it seems arrogant to assume we know with absolute certainty how effects with lightspeed work, considering we know a photon goes that fast and how much we don't know about photons, at the very least.

Now, I'm not about to start arguing that it's possible for a particle with mass to reach or Einstein was wrong or anything, but I'm perfectly willing to entertain thought experiments of what, by all of our understanding, should be impossible and ignoring the "well you can't" aspects for the sake of the thought experiment.

[Rydiro]

If you actually did manage to get a potato to lightspeed (breaking a number of laws of physics to do so) then it would literally have infinite kinetic energy and would entirely destroy the Earth--and the rest of the universe as well, but let's not worry too much about that part. Assuming you actually mean some "arbitrarily close to lightspeed" value then you're still wrong, because you can literally keep adding kinetic energy to make the thing get closer and closer to lightspeed without any upper limit. If youure just thinking "Well, it's 1/2 m * v ^2 and we know m and v, so..." then you're forgetting mass dilation, which means the mass of the potato increases the closer to lightspeed it gets.
Would a superfast potato have enough (relative) time to interact with regular matter in a meaningful way?
Wouldnt its atoms just move unhindered through the Earth? Subatomic space is mostly empty. Before meaningful forces could act, most particles would be past each other.
Shooting a bullet at a paper sheet doesn't disintegrate the whole papersheet. It just punches holes where it hits.

[Yora]

Of course you can always ignore well known and proven laws of physics for hypothetical scenarios. But doing any calculations with equations you know to be wrong to compare results doesn't provide any insights into anything.
If you throw out some fundamental assumptions, you need to throw out everything and the outcome is simply fantasy.

[factotum]

considering we know a photon goes that fast and how much we don't know about photons, at the very least.


Yeah, but one critical thing we *do* know about photons is that they don't have mass, so it's not comparable to Forum Explorer's potato.

[Peelee]

Yeah, but one critical thing we *do* know about photons is that they don't have mass, so it's not comparable to Forum Explorer's potato.

A mere triviality, fixed by two simple lines: Consider a massless potato moving at the speed of light. The rest is left as an exercise for the reader.

I'm a physicist!

[Radar]

If you actually did manage to get a potato to lightspeed (breaking a number of laws of physics to do so) then it would literally have infinite kinetic energy and would entirely destroy the Earth--and the rest of the universe as well, but let's not worry too much about that part. Assuming you actually mean some "arbitrarily close to lightspeed" value then you're still wrong, because you can literally keep adding kinetic energy to make the thing get closer and closer to lightspeed without any upper limit. If youure just thinking "Well, it's 1/2 m * v ^2 and we know m and v, so..." then you're forgetting mass dilation, which means the mass of the potato increases the closer to lightspeed it gets.
I thought that as high velocity projectiles very often leave a clean, narrow hole and do not deposit all that much energy - as there is no time for it to propagate any further than the direct path of the projectile - it would not destroy the whole planet. However, there was a What if? (https://what-if.xkcd.com/20/) article dedicated to such a problem but with a much larger impactor. The point is that with enough nines after the dot you can reduce the Earth to a rapidly expanding gas cloud.


The Prandtl-Glauert singularity says "hi".

Seriously, no matter how good the math is, it seems arrogant to assume we know with absolute certainty how effects with lightspeed work, considering we know a photon goes that fast and how much we don't know about photons, at the very least.

Now, I'm not about to start arguing that it's possible for a particle with mass to reach or Einstein was wrong or anything, but I'm perfectly willing to entertain thought experiments of what, by all of our understanding, should be impossible and ignoring the "well you can't" aspects for the sake of the thought experiment.
Actually, we know pretty well, how matter behaves at high relativistic speeds as we commonly accelerate protons or heavy ions to very significant fractions of c. For example LHC accelerates protons to 0.999999991c.

[Peelee]

Actually, we know pretty well, how matter behaves at high relativistic speeds as we commonly accelerate protons or heavy ions to very significant fractions of c. For example LHC accelerates protons to 0.999999991c.

That last 0.000000001 is the real trick, isn't it?

For reals, though, that's pretty awesome. I knew we got to somewhere like 0.000something Kelvin up in Canada, but didn't know how close to c we've gotten.

[Mastikator]

The Prandtl-Glauert singularity says "hi".

Seriously, no matter how good the math is, it seems arrogant to assume we know with absolute certainty how effects with lightspeed work, considering we know a photon goes that fast and how much we don't know about photons, at the very least.

Now, I'm not about to start arguing that it's possible for a particle with mass to reach or Einstein was wrong or anything, but I'm perfectly willing to entertain thought experiments of what, by all of our understanding, should be impossible and ignoring the "well you can't" aspects for the sake of the thought experiment.

Iron atom nucluei with 99.9999999999% of the speed of light crash into the earth all the time. We know a bit about what happens, sometimes they go right through the entire planet. Sometimes they crash into an atom somewhere along the way and scatter into many high energy particles.
If we could accelerate an entire potato to the same speed and direct it at the Earth it would be devastating for all life on the surface.

[halfeye]

So the solution is somehow cover the entire planet in a 50 meter thick layer of sugar.

A 100 metre thick layer of plant matter, yeah. Eventually, peat and then coal. The point is carbon isn't a gas, it's oxides are, separate out the oxygen, lots of carbon. There's probably something to be done with all the oxygen, maybe burn rocks?

[Tvtyrant]

The radiation hitting Venus is double what Earth gets. I don't know that an Earth atmosphere would be sufficient to protect human life there.

[halfeye]

The radiation hitting Venus is double what Earth gets. I don't know that an Earth atmosphere would be sufficient to protect human life there.

I'm sort of thinking leave some of the sun-shield in place. I don't know that much about the non-solar radiation.

The goldilocks zone is where water is liquid. We're currently pretty near the cold end of that, Venus is probably near the hot end or outside it, we'd be uncomfortable at 90 degrees C, but at the thermal vents there is life at that temperature, and if we got the temperature down below that once, we could probably keep it down. Mars is always going to be cold.

[Forum Explorer]

If you actually did manage to get a potato to lightspeed (breaking a number of laws of physics to do so) then it would literally have infinite kinetic energy and would entirely destroy the Earth--and the rest of the universe as well, but let's not worry too much about that part. Assuming you actually mean some "arbitrarily close to lightspeed" value then you're still wrong, because you can literally keep adding kinetic energy to make the thing get closer and closer to lightspeed without any upper limit. If youure just thinking "Well, it's 1/2 m * v ^2 and we know m and v, so..." then you're forgetting mass dilation, which means the mass of the potato increases the closer to lightspeed it gets.

Right, I didn't literally mean lightspeed because of the whole impossibility of it. I'll also admit that I drastically underestimated how much energy is gained going from 0.9c to 0.9999c.

However, it's completely irrelevant to the discussion and my idea in the first place. There's no reason to accelerate an object that fast when bombarding Venus. It would be a waste of energy to do so and it would make terraforming Venus harder.


Yeah, but one critical thing we *do* know about photons is that they don't have mass, so it's not comparable to Forum Explorer's potato.

It's not my potato! I didn't bring up the concept in the first place.

[halfeye]

Right, I didn't literally mean lightspeed because of the whole impossibility of it.

However, you did literally write "lightspeed".

[Radar]

Right, I didn't literally mean lightspeed because of the whole impossibility of it. I'll also admit that I drastically underestimated how much energy is gained going from 0.9c to 0.9999c.

However, it's completely irrelevant to the discussion and my idea in the first place. There's no reason to accelerate an object that fast when bombarding Venus. It would be a waste of energy to do so and it would make terraforming Venus harder.
True, we do not need such ludicrous speeds (https://www.youtube.com/watch?v=ygE01sOhzz0).


It's not my potato!
It seems that this potato got pretty hot from traveling so fast. :smallwink:

[Peelee]

It's not my potato! I didn't bring up the concept in the first place.

We can call it Peelee's Potato if you'd like.

Also,i got fifty bucks for whoever can get a concept called "Peelee's Potato" published into a major reputable physics textbook.

[Battleship789]

We do know a bit about how relativistic particle collisions impact humans due to an accident in the Soviet Union (https://en.wikipedia.org/wiki/Anatoli_Bugorski).

[The Random NPC]

This seems relevant. (https://what-if.xkcd.com/1/)

[wumpus]

So the solution is somehow cover the entire planet in a 50 meter thick layer of sugar.

Just how different is that from topsoil? I'd expect part of that "layer of carbs" to be forest and undergrowth, but soil would have to make up a large part of it.

Venus is presumably far easier to terraform: you already have plenty of materials life needs to build an Earth-like plantet (in the clouds, the surface can wait until the clouds change a lot). Just expect it to take centuries or longer.

[Yora]

The problem with turning most of the atmosphere into biomass is that we first would have to reduce the temperature down from over 400 degrees. Cellulose and hydrocarbons ignite at those temperatures, and any kinds of plants to turn CO2 into cellulose require liquid water. Not to mention proteins which break down at a measly 40 degrees.

While there are extremophile microbes on Earth, the extreme temperatures they can survive in are in the range of 80 to 120 degrees. And they still require liquid water.

Populating Venus with life to make it habitable for life doesn't work.

I don't know if machines are plausible that use solar power to convert CO2 and local minerals into a compound that is stable up to 500 degrees. But it would be incredibly slow.

[Forum Explorer]

The problem with turning most of the atmosphere into biomass is that we first would have to reduce the temperature down from over 400 degrees. Celulose and hydrocarbons ignite at those temperatures, and any kinds of plants to turn CO2 into celulose require liquid water. Not to mention proteins which break down at a measly 40 degrees.

While there are extremophile microbes on Earth, the extreme temperatures they can survive in are in the range of 80 to 120 degrees. And they still require liquid water.

Populating Venus with life to make it habitable for life doesn't work.

I don't know if machines are plausible that use solar power to convert CO2 and local minerals into a compound that is stable up to 500 degrees. But it would be incredibly slow.

That's why the plan isn't to convert it to biomass, not right away anyways. Adding hydrogen causes a chemical reaction which results in graphite and water. It takes a lot of heat to create this reaction, but Venus is hot enough for the reaction to happen naturally. This will reduce the amount of CO2 in the atmosphere, allowing the planet to begin to cool. The reaction itself should also cool things down, though I'm not 100% positive that it is a endothermic reaction.

The only thing you need to do for this to work is to throw an entire ice moon at Venus. Preferably Hydrogen around an Iron core.

[Yora]

Part 2, in which I provide arguments for the opposing opinion:

One issue I was thinking of was that even if you could turn the CO2 into stable solid molecules to fall to the surface until the CO2 levels are down to 415 parts per million, there would barely be any atmosphere left with the measly 3.5% of Nitrogen that Venus has. So I did the math. I couldn't really find out how I get from ppm to Gt to calculate the exact amounts, but even assuming atmospheric gasses weigh about the same, it became immediately obvious that it doesn't matter.

Even if N2 on Earth is 781 parts per thousand and on Venus only 25 parts per thousand, the fact that Venus has a much more massive atmosphere means that there's about four times as many Nitrogen on Venus than there is on Earth. Even if the weights of the gases are pretty unequal, it still should come out as "a lot more".

The total amount of noble gases seems to be roughly comparable.

Sulfur dioxide is 1 ppm on Earth and 150 ppm on Venus. Again, ignoring that gases have different weights, that still comes out as 10,000 times as much of the stuff on Venus as on Earth. SO2 reflects solar energy instead of trapping it. And I believe it is significantly more effective in that regard than CO2. So you probably could get away with much higher concentrations of CO2 than on Earth.
That is, if you don't mind all the moisture in the air being sulfuric acid. And air pressure would still be something like 4 times higher than on Earth. But hey, it's a start.

[Forum Explorer]

Part 2, in which I provide arguments for the opposing opinion:

One issue I was thinking of was that even if you could turn the CO2 into stable solid molecules to fall to the surface until the CO2 levels are down to 415 parts per million, there would barely be any atmosphere left with the measly 3.5% of Nitrogen that Venus has. So I did the math. I couldn't really find out how I get from ppm to Gt to calculate the exact amounts, but even assuming atmospheric gasses weigh about the same, it became immediately obvious that it doesn't matter.

Even if N2 on Earth is 781 parts per thousand and on Venus only 25 parts per thousand, the fact that Venus has a much more massive atmosphere means that there's about four times as many Nitrogen on Venus than there is on Earth. Even if the weights of the gases are pretty unequal, it still should come out as "a lot more".

The total amount of noble gases seems to be roughly comparable.

Sulfur dioxide is 1 ppm on Earth and 150 ppm on Venus. Again, ignoring that gases have different weights, that still comes out as 10,000 times as much of the stuff on Venus as on Earth. SO2 reflects solar energy instead of trapping it. And I believe it is significantly more effective in that regard than CO2. So you probably could get away with much higher concentrations of CO2 than on Earth.
That is, if you don't mind all the moisture in the air being sulfuric acid. And air pressure would still be something like 4 times higher than on Earth. But hey, it's a start.

It does get complicated and messy after step 1. I mean, the water you are creating via the reaction in question becomes water vapor, which is a more powerful greenhouse gas than CO2. But it's also a lot more reflective than CO2, so it can also lower the heat coming in. But also also, the water vapor does contribute to the weight of the atmosphere. But it is actually lighter than CO2, so it would still go down. And thankfully that would help dilute the sulfuric acid, though I'm not sure by how much.

But yeah, it's a start. There are likely a bunch of other steps needed to actually get Venus to living condition. Still, I do think it's easier than Mars. Because I just don't think it's easier to add that much atmosphere to Mars. I mean, you might be able to set up a colony on Mars pretty easily, particularly if you did deep into the mantle.

The core of Mars is a lot colder than ours right? So you could dig much deeper than you can on Earth which would help with dealing with gravity, duststorms, and space debris.

[Fat Rooster]

You don't need to convert the CO2 to oxygen and carbon, and you actually don't really want to. What you want to do is cool the crust enough that the rock can weather. The reason there is so much CO2 is that rocks that would be carbonate at reasonable temperatures break into carbon dioxide and oxide rocks at higher temperatures. Even if you were able to split all the carbon dioxide you would still be left with ~70 bar atmosphere of pure oxygen, which isn't much better (and good luck managing any coal fires that break out). To call it terraformed you need to react the carbon dioxide with rock instead, which requires you to cool the whole planet crust down first. The same process gets rid of the SO2.

Doing this is hard. Even with no sunlight at all the surface would stay hot for an absurd length of time so a sun shade of some form would be the easy part. Getting the atmosphere to stop behaving like a blanket is not easy. There might be a way though. The first step would be to seed the clouds to cause much larger droplet size than normal in the sulphuric acid clouds. You might even have to artificially capture large quantities of sulphuric acid and drop it through a pipe, so droplet size is in the cm range. The goal is to cause a massive storm in a single location, using the sulphuric acid as both a pump and heat exchanger. The deeper down you can deliver the sulphuric acid the more powerful the convection you drive, hence wanting large droplet size. Once you can start to get some sulphuric acid all the way down to the ground it will start to react with rock to form sulphates, slowly pulling the SO2 out of the atmosphere. You don't need to cool down the whole crust to do this. Ideally you want to localise rainfall over a single area that you cool down first as a sink for sulphur. If you can get rid of the sulphur dioxide the greenhouse effect is not nearly so extreme, and you can then continue the storm cooling with water. If you choose your location right to start with you might be able to keep the majority of the water on the planet in the same area constantly powering your storm. That means that water vapour will not be a significant greenhouse gas everywhere, but would still drive a powerful convective heat transfer.

Hitting it with a couple of large icy comets might be an idea, because the more liquid phase components to the atmosphere the faster it can cool down, and I can't find one of those that doesn't need hydrogen. 10 comets the size of Haley's comet would ~double the amount of hydrogen available, so those are viable numbers. Regular bombardment with comets throwing dust into the upper atmosphere could even be how you shade from the sun. The life of a terraformer would be interesting, to say the least. You would be constantly living in the heart of a storm on a planet that people are deliberately throwing things at!

Even if you do manage to get the surface cool, the timescales and amount of work to get all the carbon dioxide to weather is extreme. You would need to turn the entire surface into gravel to a depth in the tens to hundreds of meters if you want it to go at any pace. Fracking type techniques might work, but cooling subsurface rock is much harder too.

If you do all that, you should be left with a liveable planet. It should even be stable, because I think it is the hydrogen that caused the runaway in the first place. As long as you can get it cool enough that carbon and sulphur stay in rocks you should be fine.

[factotum]

Even if you were able to split all the carbon dioxide you would still be left with ~70 bar atmosphere of pure oxygen, which isn't much better (and good luck managing any coal fires that break out).

I don't know if this is at all practical, but couldn't you react the atmospheric oxygen with iron (sourced from asteroids again) to form iron oxide? AFAIK all iron oxides have very high melting points and would thus all be solid even at Venus' current temperatures, so if you can somehow split the CO2 into its constituents and then reduce the oxygen by reacting it with the iron, it might be possible to achieve a good result.

I have absolutely no idea just how much iron you'd need to do this, though!

[Forum Explorer]

You don't need to convert the CO2 to oxygen and carbon, and you actually don't really want to. What you want to do is cool the crust enough that the rock can weather. The reason there is so much CO2 is that rocks that would be carbonate at reasonable temperatures break into carbon dioxide and oxide rocks at higher temperatures. Even if you were able to split all the carbon dioxide you would still be left with ~70 bar atmosphere of pure oxygen, which isn't much better (and good luck managing any coal fires that break out). To call it terraformed you need to react the carbon dioxide with rock instead, which requires you to cool the whole planet crust down first. The same process gets rid of the SO2.

Doing this is hard. Even with no sunlight at all the surface would stay hot for an absurd length of time so a sun shade of some form would be the easy part. Getting the atmosphere to stop behaving like a blanket is not easy. There might be a way though. The first step would be to seed the clouds to cause much larger droplet size than normal in the sulphuric acid clouds. You might even have to artificially capture large quantities of sulphuric acid and drop it through a pipe, so droplet size is in the cm range. The goal is to cause a massive storm in a single location, using the sulphuric acid as both a pump and heat exchanger. The deeper down you can deliver the sulphuric acid the more powerful the convection you drive, hence wanting large droplet size. Once you can start to get some sulphuric acid all the way down to the ground it will start to react with rock to form sulphates, slowly pulling the SO2 out of the atmosphere. You don't need to cool down the whole crust to do this. Ideally you want to localise rainfall over a single area that you cool down first as a sink for sulphur. If you can get rid of the sulphur dioxide the greenhouse effect is not nearly so extreme, and you can then continue the storm cooling with water. If you choose your location right to start with you might be able to keep the majority of the water on the planet in the same area constantly powering your storm. That means that water vapour will not be a significant greenhouse gas everywhere, but would still drive a powerful convective heat transfer.

Hitting it with a couple of large icy comets might be an idea, because the more liquid phase components to the atmosphere the faster it can cool down, and I can't find one of those that doesn't need hydrogen. 10 comets the size of Haley's comet would ~double the amount of hydrogen available, so those are viable numbers. Regular bombardment with comets throwing dust into the upper atmosphere could even be how you shade from the sun. The life of a terraformer would be interesting, to say the least. You would be constantly living in the heart of a storm on a planet that people are deliberately throwing things at!

Even if you do manage to get the surface cool, the timescales and amount of work to get all the carbon dioxide to weather is extreme. You would need to turn the entire surface into gravel to a depth in the tens to hundreds of meters if you want it to go at any pace. Fracking type techniques might work, but cooling subsurface rock is much harder too.

If you do all that, you should be left with a liveable planet. It should even be stable, because I think it is the hydrogen that caused the runaway in the first place. As long as you can get it cool enough that carbon and sulphur stay in rocks you should be fine.

Small quibble, not breaking CO2 into O2 and Carbon, but changing it to H2O and Graphite. Also Venus lacks hydrogen. There may be a bunch stored underneath the crust, but as far as I know, that's theoretical. But hydrogen certainly isn't to blame for the runaway greenhouse effect in the first place.


I don't know if this is at all practical, but couldn't you react the atmospheric oxygen with iron (sourced from asteroids again) to form iron oxide? AFAIK all iron oxides have very high melting points and would thus all be solid even at Venus' current temperatures, so if you can somehow split the CO2 into its constituents and then reduce the oxygen by reacting it with the iron, it might be possible to achieve a good result.

I have absolutely no idea just how much iron you'd need to do this, though!

Yes you could! Asteroids are a good source of this (bombarding the planet actually can blow away approximately 0.001% of the atmosphere at a time) and can reduce the atmosphere at the same time. Alternatively, Mercury has a ton of iron you can access.

[Fat Rooster]

Small quibble, not breaking CO2 into O2 and Carbon, but changing it to H2O and Graphite. Also Venus lacks hydrogen. There may be a bunch stored underneath the crust, but as far as I know, that's theoretical. But hydrogen certainly isn't to blame for the runaway greenhouse effect in the first place.

Sorry, where are you getting the hydrogen to make water from? There is enough to be used catalytically, but not as a reactant (20ppm water). Even hitting it with a lot of quite major comets isn't going to provide it with enough hydrogen for that.

How do you believe the thermal runaway happened if you don't think hydrogen played an important part? Carbonate and sulphate rocks don't decompose until they get to several hundred degrees, so it wasn't carbon dioxide or sulphur dioxide that set it off. Methane or other hydrocarbons could do it, but no mechanism is known that would continue to produce vast quantities above 200' and they still require hydrogen. The only believable theory I've seen has water oceans that boiled off, with water vapour driving it until the rock started to outgas. The hydrogen required for that ocean is no longer there, so it couldn't happen again (though it could happen here, if we screw up really badly).

I should clarify, when I say hydrogen I don't just mean molecular hydrogen. I mean all hydrogen, whether it is in water, sulphuric acid, methane, or anything else.


Yes you could! Asteroids are a good source of this (bombarding the planet actually can blow away approximately 0.001% of the atmosphere at a time) and can reduce the atmosphere at the same time. Alternatively, Mercury has a ton of iron you can access.

Not enough. 1kg of iron can lock up about ~300g of oxygen, which comes from ~400g of CO2. You would need a larger mass of iron than Ceres, and M type asteroids are not common. We could probably find a better use for ones that do exist too.

As for getting Iron from Mercury, the energy requirements are actually higher than simply striping off the atmosphere and accelerating it above escape velocity. There is no point bothering with chemistry at those energy levels, or anything fancy. You can just brute force remove the excess atmosphere.

[Forum Explorer]

Sorry, where are you getting the hydrogen to make water from? There is enough to be used catalytically, but not as a reactant (20ppm water). Even hitting it with a lot of quite major comets isn't going to provide it with enough hydrogen for that.

How do you believe the thermal runaway happened if you don't think hydrogen played an important part? Carbonate and sulphate rocks don't decompose until they get to several hundred degrees, so it wasn't carbon dioxide or sulphur dioxide that set it off. Methane or other hydrocarbons could do it, but no mechanism is known that would continue to produce vast quantities above 200' and they still require hydrogen. The only believable theory I've seen has water oceans that boiled off, with water vapour driving it until the rock started to outgas. The hydrogen required for that ocean is no longer there, so it couldn't happen again (though it could happen here, if we screw up really badly).

I should clarify, when I say hydrogen I don't just mean molecular hydrogen. I mean all hydrogen, whether it is in water, sulphuric acid, methane, or anything else.


Not enough. 1kg of iron can lock up about ~300g of oxygen, which comes from ~400g of CO2. You would need a larger mass of iron than Ceres, and M type asteroids are not common. We could probably find a better use for ones that do exist too.

As for getting Iron from Mercury, the energy requirements are actually higher than simply striping off the atmosphere and accelerating it above escape velocity. There is no point bothering with chemistry at those energy levels, or anything fancy. You can just brute force remove the excess atmosphere.

That's right, I had forgotten that it was theorized that Venus used to have a bunch of hydrogen in its atmosphere that was slowly stripped away by the sun.

I haven't been using throw an ice moon as an exaggeration. I think it would take pretty much that much matter to make a difference. I mean, I'm pretty sure you'd need to throw dozens of Oumuamuas in order to get enough hydrogen. Theoretically these could be found in the Oorts cloud. Alternatively you could slowly mine hydrogen from a gas giant and build your own Oumuamuas to launch.

You could also throw Mimas or Lapetus at Venus, though those are mostly frozen water, and I'm not sure if just dumping a bunch of water on Venus would be all that useful.

Speaking of brute force, if you hit Venus with something big enough to create a moon from the impact (like what happened with Earth) would that moon have an atmosphere of its own?

[Yora]

I have absolutely no idea just how much iron you'd need to do this, though!

Even if the chemistry works out, I think it's the whole scale of the required operation that I think makes the entire idea unfeasible.
Given that human civilization only had 12,000 years so far and Earth should remain habitable for humans for another 500,000,000 years, saying with certainty that something will never be done seems rationally unsound.
But even in a best case scenario where all the required asteroids and comets can be collected and dumped onto Venus, how long will it take for all the chemical reactions to convert all of the atmosphere? A thousand years? Ten thousand years? I find it hard to believe that a massively expensive project would be run for hundreds of years so that someone will benefit from it thousands of years in the future. For something with very marginal benefit, as a civilization that has the technology and resources for such an undertaking should have no problems with maining human habitats in space.

(And for people who feel they need to figure out how humanity will survive in half a billion years, space habitats have the advantage of being possible to move into any orbit around the sun that has the optimal intensity of solar radiation. Even when it's a white dwarf. Space cities are both the short and long term solution. :smallwink:)

[halfeye]

Even if the chemistry works out, I think it's the whole scale of the required operation that I think makes the entire idea unfeasible.
Given that human civilization only had 12,000 years so far and Earth should remain habitable for humans for another 500,000,000 years, saying with certainty that something will never be done seems rationally unsound.
But even in a best case scenario where all the required asteroids and comets can be collected and dumped onto Venus, how long will it take for all the chemical reactions to convert all of the atmosphere? A thousand years? Ten thousand years? I find it hard to believe that a massively expensive project would be run for hundreds of years so that someone will benefit from it thousands of years in the future. For something with very marginal benefit, as a civilization that has the technology and resources for such an undertaking should have no problems with maining human habitats in space.

(And for people who feel they need to figure out how humanity will survive in half a billion years, space habitats have the advantage of being possible to move into any orbit around the sun that has the optimal intensity of solar radiation. Even when it's a white dwarf. Space cities are both the short and long term solution. :smallwink:)

I like space habitats a lot, I think they are the long term solution for people. My personal preference would be to put the tigers, aardvarks and penguins etc. on Venus and never let humans down there at all, because humans are going to take all the land and most of the sea on Earth.

Reducing the temperature will mean putting some solar sails between Venus and the Sun, we'll do that for Earth first, to stop global warming sinking the coastal cities, but once that's cheap (and really it will be, solar sails are thin and should be cheap to make) it'll be the obvious thing to do to use them for Venus. Bacteria can double their population in a couple of hours, if the environment suits them, Venus with an earthlike temperature should suit some of them fine.

Water will be necessary, but most of Earth's water is in the seas, we really don't need that much for land life at all, though seas would be nice.

[factotum]

I like space habitats a lot, I think they are the long term solution for people.

There are advantages to building on planets, though. You get gravity for free, and if there's any sort of decent atmosphere you also get free protection from small and medium sized rocks, not to mention quite a bit of hard radiation. You can also dig underground tunnels to get even more protection from stray rocks and the like. Doesn't apply so much to Venus because of the heat and the acid in the atmosphere, but would definitely be some advantages to living on Mars.

[Radar]

Reducing the temperature will mean putting some solar sails between Venus and the Sun, we'll do that for Earth first, to stop global warming sinking the coastal cities, but once that's cheap (and really it will be, solar sails are thin and should be cheap to make) it'll be the obvious thing to do to use them for Venus. Bacteria can double their population in a couple of hours, if the environment suits them, Venus with an earthlike temperature should suit some of them fine.
Using gigantic nightshade to cool down Earth might be a last resort at some point, but I would not use it, if there are alternatives. Less sunlight on Earth would have far reaching consequences for the climate and plant life.


Water will be necessary, but most of Earth's water is in the seas, we really don't need that much for land life at all, though seas would be nice.
Without oceans the water circulation would be very different. There might be no rain or natural rivers and that would make cultivating any plant life that much more difficult. A self-sustaining ecosystem based on Earth would most likely require vast oceans.

[Yora]

There are advantages to building on planets, though. You get gravity for free, and if there's any sort of decent atmosphere you also get free protection from small and medium sized rocks, not to mention quite a bit of hard radiation. You can also dig underground tunnels to get even more protection from stray rocks and the like. Doesn't apply so much to Venus because of the heat and the acid in the atmosphere, but would definitely be some advantages to living on Mars.

The problem with planetary gravity is that you can't adjust it. On Venus, you have 91% Earth Gravity, which I guess the human body probably could adjust to. For Mars and Mercury it's only 38%, which I seriously doubt is enough for the healthy development of bones, circulatory system, and nervous system in children. Next one is Io with a measly 18% and from there it's only downhill.
Which is why I think that everything but Venus can be ruled out for permanent habitation right from the start. (Doing 6 month tours in shipyards and fuel production facilities on the Moon is a totally different story. No children and elderly there, though.)

If we had a planet with the size of Venus and the surface conditions of Mars, I'd say permanent colonization would absolutely be doable, possibly within the next 100 years.
But as it is, we only have two possible candidates in the solar system and both of them happen to have two huge, but completely different dealbreakers.

Simulated gravity in rotating space habitats can be adjusted to whatever strength you want, provided the whole thing is big enough. (100m radius seems to roughly be where tidal forces on head and feet become small enough to not cause disorientation, which is why we haven't build anything like it yet.) And the cool thing about weightless objects in a vacuum is that once you get them spinning, they will keep spinning forever without any energy input. Which makes that approach actually quite cheap, compared to building the habitat in the first place.

[factotum]

Thing is, though, we've never actually studied what the long-term effects are of living in simulated gravity via rotation environments. Until we *do* have such a thing (whenever we get round to building it), we can't say for sure that the "fake" gravity in a rotating station would be better for us than lower gravity on a planet.

[Fat Rooster]

Thing is, though, we've never actually studied what the long-term effects are of living in simulated gravity via rotation environments. Until we *do* have such a thing (whenever we get round to building it), we can't say for sure that the "fake" gravity in a rotating station would be better for us than lower gravity on a planet.

If they turn out to be different the physicists are going to be even more interested than the biologists. That would break relativity. People not having significant issue with 1G centrifuges is one of the few possibilities that even the most conservative test programs would take on trust (getting 1G centrifuges right so they don't break is a far bigger concern).

It is certainly true that we have never studied 'sub G' properly. We know things go wrong at 0G, and work well at 1G, but we really have no idea how large life will behave at .1G or .3G. Impossible to study on earth, hard to study in space. All we have are theories at this point. We can be pretty sure it will be far harder to adjust to Earth from Mars than the other way around, but that doesn't say anything about the viability of life on Mars, with or without therapies (exercises, drugs, diet, whatever is required). Studying it in space would require a whole new station; one that is structural (ISS is flimsy enough that one of it's tiny accelerations almost shook it apart (https://www.nbcnews.com/id/wbna28998876)). That means heavier and more expensive. There are other hurdles too, though some have been overcome. The new dragon could probably manage to dock at a spinning hub, but berthing is sort of out of the question. All the designs that include a rotating seal are probably no-go, so docking ports have to be rotating too. Solar panels could maybe be static, as a transformer can be integrated into a bearing just fine, but radiators are much harder. Many of them probably need to be on the rotor.

Such a station would have micro-G regions in the hub, but it would largely be unsuitable for studying micro-G effects. You could have it attached to another station that wasn't spinning, but getting between them would require either another 'craft' (could be more like a lift than a craft, but it would essentially have to undock from one, match spin with the other, then dock). It gets complicated.

[Radar]

If they turn out to be different the physicists are going to be even more interested than the biologists. That would break relativity. People not having significant issue with 1G centrifuges is one of the few possibilities that even the most conservative test programs would take on trust (getting 1G centrifuges right so they don't break is a far bigger concern).

It is certainly true that we have never studied 'sub G' properly. We know things go wrong at 0G, and work well at 1G, but we really have no idea how large life will behave at .1G or .3G. Impossible to study on earth, hard to study in space. All we have are theories at this point. We can be pretty sure it will be far harder to adjust to Earth from Mars than the other way around, but that doesn't say anything about the viability of life on Mars, with or without therapies (exercises, drugs, diet, whatever is required). Studying it in space would require a whole new station; one that is structural (ISS is flimsy enough that one of it's tiny accelerations almost shook it apart (https://www.nbcnews.com/id/wbna28998876)). That means heavier and more expensive. There are other hurdles too, though some have been overcome. The new dragon could probably manage to dock at a spinning hub, but berthing is sort of out of the question. All the designs that include a rotating seal are probably no-go, so docking ports have to be rotating too. Solar panels could maybe be static, as a transformer can be integrated into a bearing just fine, but radiators are much harder. Many of them probably need to be on the rotor.

Such a station would have micro-G regions in the hub, but it would largely be unsuitable for studying micro-G effects. You could have it attached to another station that wasn't spinning, but getting between them would require either another 'craft' (could be more like a lift than a craft, but it would essentially have to undock from one, match spin with the other, then dock). It gets complicated.
Depending on the size of the spinning habitat, Coriolis effect might also be important, but I doubt it will do anything that people did not experience on ships for centuries.

[factotum]

If they turn out to be different the physicists are going to be even more interested than the biologists. That would break relativity.

Why? All relativity states is that it's not possible to distinguish between standing on a planet in a 1G gravity field and accelerating in a straight line at a constant 1G. If you're going in a constant rotary motion then the vector of your acceleration is constantly changing, so it's not the same situation.

[Tyndmyr]

Would a superfast potato have enough (relative) time to interact with regular matter in a meaningful way?
Wouldnt its atoms just move unhindered through the Earth? Subatomic space is mostly empty. Before meaningful forces could act, most particles would be past each other.
Shooting a bullet at a paper sheet doesn't disintegrate the whole papersheet. It just punches holes where it hits.

Ballistics begins to work oddly as you approach the speed of light. Even at relatively small fractions of it(getting anything of any decent size accelerated to that speed is hard), you start seeing density and size dominate over speed.

Given objects of equal density, you'll generally only get penetration equal to the projectile's length.

A potato not being particularly dense, it would be unlikely to penetrate very deep into the earth no matter how fast its going, and would instead essentially detonate. Assuming an earth with an atmosphere, this'll probably happen there, as despite the vastly lower density of the atmosphere, there's enough of it to stop the potato long before it gets to ground.

This'd result in a pretty impressive boom as all that energy gets converted to light, heat and sound. This would still probably be pretty bad for any unfortunate souls actually on the rock we're popping potatoes at.

I'm honestly not sure how this would work for specifically *at* light speed, but this approximation should work as you approach light speed, so it probably won't change dramatically by going a little bit faster. A potato is only so tough, after all.

[erikun]

I'll throw my hat into the "Why not a space station?" group.

At this point, Mars does not have an appreciable atmosphere, and does not have an appreciable magnetic field to protect such an atmosphere (not to mention land-bound residents) from solar winds. Plus, there is not a large amount of gravity on the planet, certainly less than is believed healthy for living humans. Combine this with the length of the journey, and it seems like any habitation on Mars would involve figuring out how to produce an acceptable atmosphere and interstellar protection for an extended journey, just to end up in a location which also needs to produce an acceptable atmosphere and interstellar protection for an extended stay. At that point, I'm not sure why there is a desire to place oneself onto a planet - with the whole difficulty of propulsion and getting back off again - instead of just making the travel vehicle itself the thing with the atmosphere and the protection and the whole habitation thing going on. Certainly, docking two spacecraft would be easier to work out than attempting to land/leave a planet repeatedly.

I can certainly understand a corporation or organization's greater interest in planetary habitation: there's a lot more valuable stuff on Mars than a random chunk of rock in the asteroid belt, if only because they can just set up one base in one location (Marsside landing pad) to establish transport routes. But I'm not sure how living on Mars would be superior for the people there than just living on a ship out in space. People have mentioned digging under the surface for protection from solar radiation, but rock not being completely-impermeable just means putting nearly as much work into sealing the rock faces underground as it would sealing a structure above ground. Plus, it wouldn't help any with any sort of mining work for resources on the planet itself.

[Tyndmyr]

Why? All relativity states is that it's not possible to distinguish between standing on a planet in a 1G gravity field and accelerating in a straight line at a constant 1G. If you're going in a constant rotary motion then the vector of your acceleration is constantly changing, so it's not the same situation.

You get a couple of interesting effects inside of a massive centifruge.

For one thing, depending on how big it is, there might be a noticeably different rotational speed between your head and your feet. That might be a little weird.

Certainly the effective gravity would vary far more rapidly than it does on earth. If you live in a two story house, upstairs might feel noticeably different than downstairs. Likewise, a ball thrown in the air would probably experience significant gravity variance, and would probably fly differently than we'd expect on earth.

If you have no structure in that space, and instead it's just open air, well, you might get some interesting wind forces. Certainly they'd be very different than earth weather patterns, but given a large enough of a structure, you *would* have weather. After all, extremely large buildings on earth do. To the best of my knowledge, nobody's built a centrifuge big enough to mess with this.

I don't see any showstoppers in here, but I would expect there to be a lot of little oddities cropping up in the first testbed.

[Forum Explorer]

The problem with planetary gravity is that you can't adjust it. On Venus, you have 91% Earth Gravity, which I guess the human body probably could adjust to. For Mars and Mercury it's only 38%, which I seriously doubt is enough for the healthy development of bones, circulatory system, and nervous system in children. Next one is Io with a measly 18% and from there it's only downhill.
Which is why I think that everything but Venus can be ruled out for permanent habitation right from the start. (Doing 6 month tours in shipyards and fuel production facilities on the Moon is a totally different story. No children and elderly there, though.)

If we had a planet with the size of Venus and the surface conditions of Mars, I'd say permanent colonization would absolutely be doable, possibly within the next 100 years.
But as it is, we only have two possible candidates in the solar system and both of them happen to have two huge, but completely different dealbreakers.

Simulated gravity in rotating space habitats can be adjusted to whatever strength you want, provided the whole thing is big enough. (100m radius seems to roughly be where tidal forces on head and feet become small enough to not cause disorientation, which is why we haven't build anything like it yet.) And the cool thing about weightless objects in a vacuum is that once you get them spinning, they will keep spinning forever without any energy input. Which makes that approach actually quite cheap, compared to building the habitat in the first place.

I'm curious, how deep would you have to dig on Mars to experience a higher level of gravity? It would go up as you got deeper wouldn't it?


I'll throw my hat into the "Why not a space station?" group.

At this point, Mars does not have an appreciable atmosphere, and does not have an appreciable magnetic field to protect such an atmosphere (not to mention land-bound residents) from solar winds. Plus, there is not a large amount of gravity on the planet, certainly less than is believed healthy for living humans. Combine this with the length of the journey, and it seems like any habitation on Mars would involve figuring out how to produce an acceptable atmosphere and interstellar protection for an extended journey, just to end up in a location which also needs to produce an acceptable atmosphere and interstellar protection for an extended stay. At that point, I'm not sure why there is a desire to place oneself onto a planet - with the whole difficulty of propulsion and getting back off again - instead of just making the travel vehicle itself the thing with the atmosphere and the protection and the whole habitation thing going on. Certainly, docking two spacecraft would be easier to work out than attempting to land/leave a planet repeatedly.

I can certainly understand a corporation or organization's greater interest in planetary habitation: there's a lot more valuable stuff on Mars than a random chunk of rock in the asteroid belt, if only because they can just set up one base in one location (Marsside landing pad) to establish transport routes. But I'm not sure how living on Mars would be superior for the people there than just living on a ship out in space. People have mentioned digging under the surface for protection from solar radiation, but rock not being completely-impermeable just means putting nearly as much work into sealing the rock faces underground as it would sealing a structure above ground. Plus, it wouldn't help any with any sort of mining work for resources on the planet itself.

A space station has the problems of no durability, and effectively being stuck in a submarine for your entire life. There a huge host of psychological problems that comes from that, which would be hard to manage. Not to mention a space station is basically human only, and cannot be allowed to break down at all, ever.

[Tyndmyr]

I'm curious, how deep would you have to dig on Mars to experience a higher level of gravity? It would go up as you got deeper wouldn't it?

You'd have to dig a lot in order to experience any significant change, and it wouldn't really solve this for you. If you dug all the way to the core, the mass would be roughly evenly distributed around you, so you'd experience almost no gravity.

Digging does help with radiation shielding, though.


A space station has the problems of no durability, and effectively being stuck in a submarine for your entire life. There a huge host of psychological problems that comes from that, which would be hard to manage. Not to mention a space station is basically human only, and cannot be allowed to break down at all, ever.

Those are unfortunately also problems on planets. It's a question of if you prefer hard vacuum outside or abrasive dust.

[Forum Explorer]

You'd have to dig a lot in order to experience any significant change, and it wouldn't really solve this for you. If you dug all the way to the core, the mass would be roughly evenly distributed around you, so you'd experience almost no gravity.

Digging does help with radiation shielding, though.



Those are unfortunately also problems on planets. It's a question of if you prefer hard vacuum outside or abrasive dust.

Wait really? I thought being surrounded by all that mass would effectively put the pressure of the entire planet on you.


Well yes. That's my problem with terraforming Mars. You aren't really. You're just putting a space station on Mars' surface. Venus, the end goal is to have a planet you can take a walk on.

[Yora]

I'm curious, how deep would you have to dig on Mars to experience a higher level of gravity? It would go up as you got deeper wouldn't it?

I did take a little look around on that topic, and all the sources seem to conclude that on a body of uniform density, gravity actually decreases as you go below the surface. As you descend down, there is less Earth beneath you to pull you down, but you keep getting more and more Earth above you that pulls you up. At the very core, you would be pulled into all directions equally and be completely weightless.

The Earth is of course not homogeneous and of uniform density, and the heavy metal core much denser than the silicon oxide and aluminium oxide that makes up the crust. So as you do get closer to the metal core, you actually get somewhat of an increase in gravity. But according to this graph (https://en.wikipedia.org/wiki/File:EarthGravityPREM.jpg) the increase is very small. Gravity goes from 9.8 m/s² to maybe 10.8 m/s², at an incredible depth of 3,000 km.
I don't know about the composition of Mars, but if the effects there are similar, you'd have to go hundreds of km down to get from 0.18g to maybe 0.22g. It would be negligible, and also practically impossible.


A space station has the problems of no durability, and effectively being stuck in a submarine for your entire life. There a huge host of psychological problems that comes from that, which would be hard to manage. Not to mention a space station is basically human only, and cannot be allowed to break down at all, ever.

The same problems apply to a planetary station as well. Unless you can turn the planet into a copy of Earth. Which is the premise of this thread, but probably way too optimistic even if terraforming gets actually attempted at a large scale.
Yes, objects in space can be hit by flying debris that can cause catastrophic damage. But even in Low Earth Orbit, which is already full of high speed junk, I've only heard of that happening once.
Impacts by tiny fragments on a large station might punch a hole into some walls, but the overall structural damage would be limited. Larger pieces that could cause significant destruction are much easier to spot from large distances out in space, and since the station would be in space, it would only take a slight push to get it out of the way.
A real concern, but something I consider very much manageable by a civilization that can build cities in space.

[erikun]

A space station has the problems of no durability, and effectively being stuck in a submarine for your entire life. There a huge host of psychological problems that comes from that, which would be hard to manage. Not to mention a space station is basically human only, and cannot be allowed to break down at all, ever.
To add to what others have said: Living space on Mars would have the same restrictions as living space in a permanent extraterrestrial location. A person on Mars would be stuck living inside a bunch of submarine-like tubes just to provide habitable space. And if the Mars station can expand outwards to accommodate more living space while not leaving itself open to getting hit by a stray meteorite, then I'm not sure why a space station could not.

[Tyndmyr]

Wait really? I thought being surrounded by all that mass would effectively put the pressure of the entire planet on you.

Yeah, gravity in different directions effectively cancels out.*

For instance, if you are directly between the moon and the earth, there's a point where the gravity of the two cancels(much closer to the moon), and you'll experience zero g. This is one type of Langrage point.

There may be some slight variations, because gravity in practice is never exactly even, so there may be local areas where you can get marginally higher gravity than what Mars normally has, but this would be a very small effect, it's not going to be noticeable on a human level.

*in most cases. If the gradient is extremely high, such as while falling into a black hole, there are...severe effects. Mostly this won't matter on a planetary scale, though, and can be ignored.


Well yes. That's my problem with terraforming Mars. You aren't really. You're just putting a space station on Mars' surface. Venus, the end goal is to have a planet you can take a walk on.

Assuming such terraforming is possible, that would be cool, but it is probably not an easier problem than building a reliable space station. We've actually built space stations, scaling those up to bigger and better ones is a far smaller jump than going to planet scale terraforming.

Honestly, we haven't even gotten down management of earth's greenhouse effect. If we can't handle that, Venus's seems like hard mode.

[erikun]

Assuming such terraforming is possible, that would be cool, but it is probably not an easier problem than building a reliable space station. We've actually built space stations, scaling those up to bigger and better ones is a far smaller jump than going to planet scale terraforming.
Our current space stations actually reside within the Earth's magnetosphere, meaning that they are protected from a large amount of cosmic radiation.* This means that, if you were to take the ISS up into deep space, nobody on board would end up surviving - certainly not for the entire month-long journey to Mars. We definitely have some other concerns to work out before even long-term visitation well away from the Earth is reasonable.

* Wikipedia (https://en.wikipedia.org/wiki/International_Space_Station#Crew_health_and_safety )

[Tyndmyr]

Indeed.

And still, problems of such a magnitude are tiny in comparison to fixing an entire world such as Venus.

The effort required to nudge climate even a degree or two lower on a planetary scale is truly immense. Difficult to contemplate doing successfully even on the planet we're currently on. Even stopping the warming is a pretty big challenge, let alone reversing it.

[halfeye]

Ballistics begins to work oddly as you approach the speed of light. Even at relatively small fractions of it(getting anything of any decent size accelerated to that speed is hard), you start seeing density and size dominate over speed.

This has to be wrong. The mass rises as an object nears the speed of light and time dilates. This makes the velocity more important not less.


Given objects of equal density, you'll generally only get penetration equal to the projectile's length.

That works for sabot rounds, but not apparently for rail guns, if they could make them.


A potato not being particularly dense, it would be unlikely to penetrate very deep into the earth no matter how fast its going, and would instead essentially detonate. Assuming an earth with an atmosphere, this'll probably happen there, as despite the vastly lower density of the atmosphere, there's enough of it to stop the potato long before it gets to ground.

This is mistaken, the time for the potato to evaporate goes down as it's speed rises, but the distance it travels in that time goes up. At a high enough speed (probably something impossible like 0.9999c) it goes all the way through the Earth, what comes out the other side is a plasma, but it does come out and there's a big exit wound before the Earth flies appart. It's almost certainly not going to happen, big lumps of matter don't generally go that fast and if they did anything they hit would destroy them. I certainly don't want it to happen, but I'm pretty sure that's how things go relatively speaking.


This'd result in a pretty impressive boom as all that energy gets converted to light, heat and sound. This would still probably be pretty bad for any unfortunate souls actually on the rock we're popping potatoes at.

I'm honestly not sure how this would work for specifically *at* light speed, but this approximation should work as you approach light speed, so it probably won't change dramatically by going a little bit faster. A potato is only so tough, after all.

Light speed for matter is effectively impossible, but in theory at least we can work out what happens arbitrarily close to c.

[Fat Rooster]

Why? All relativity states is that it's not possible to distinguish between standing on a planet in a 1G gravity field and accelerating in a straight line at a constant 1G. If you're going in a constant rotary motion then the vector of your acceleration is constantly changing, so it's not the same situation.
There are some weird effects that come about from the rotating reference frame, but even for a small centrifuge they will be dwarfed by the forces put on your body from moving around, or even just standing differently. It is sort of comparable to being on a boat in high seas, and as far as I am aware nobody has noticed any physiological effects from that. You might expect similar symptoms while people adjust, but the differences in terms of magnitude or character of forces on parts of you are far smaller than what we already experience day to day. If lying down doesn't completely screw with your digestive system then it is extremely unlikely a tiny Coriolis force will.

I'll throw my hat into the "Why not a space station?" group.

Lack of local elements, or lack of local energy. Nitrogen is critical for a colony to grow, but is very rare inside the frost line (and even near it). Outside the frost line sunlight is dim, making energy scarce. After that, you lack geology. Geology isn't just stuff; it is also processes, some of which are extremely useful. The rare earth metals are not the rarest ones, they are the ones that do not have concentrating processes, and hence have no high quality ores. Without geology there is no reason to expect any ores, just a mish mash of everything. M type asteroids are the exception, but they lack all the elements required for a colony, and will always be a mining outpost entirely dependent on imports. Between the Oberth effect and aerobraking it is not even much easier to get materials between asteroids than from the surfaces of planets.

The question "why not" is also not really the one you want to ask. If we take it as a given that we are shipping people off earth, and looking for somewhere to put them, then it is a relevant question, but it is not a given that we set up a colony. Even if it was, the question would be about finding somewhere with everything needed, and no asteroids exist that have everything. We need a positive reason to set up a colony, and space station colonies don't really have one, while also being perpetually dependent on imported materials. That is not good. A Martian colony also struggles to find positive reasons (closest I can find is that gold might provide some returns, discussed earlier), but can at least be self sustaining after a while and even expand.

[Yora]

Honestly, we haven't even gotten down management of earth's greenhouse effect. If we can't handle that, Venus's seems like hard mode.

The whole concept of terraforming comes out of the mid 20th century that the exponential growth in the understanding of physics and the development of technology in the preceding one hundred year would continue forever.
It's at home in the same place that brought us Faster Than Light Travel, Dyson Spheres, the Kardachev Scale, and interstellar empires with thousands of planets inhabited by trillions of people. (Also our current economic and financial model.)
Smart educated people in the 50s and 60s might actually have believed these things. And it ended up in science fiction of that period to become staples of our cultural "space fantasy". It's a modern mythology that keeps being perpetuated not because our growing understanding of the subject makes them more likely, but because we want to belief that this fantasy world of our childhood will be real one day.
But the assumption that the industrialization and resulting population growth seen in their lifetimes and the lifetimes of their grandparents is not a temporary aberration, but an eternal exponential trend is really quite misguided.

While I see permanent human populations on space habitats as technicall doable, I don't see them actually becoming a thing within any time span tha could reasonably be called a "prediction". With the Earth still having half a billion years of complex life on the surface (it's roughly halway through this stage now), it's impossible to say if something will never happen.
But as actual predictions and extrapolations go for the next few centuries, I think asteroid mining and lunar shipyards (for building and fueling mining ships) will be all we'll get. And maybe some research stations on Mars and Europa as we have in the Antarctic.

[Tyndmyr]

This has to be wrong. The mass rises as an object nears the speed of light and time dilates. This makes the velocity more important not less.

In terms of potential energy, not in terms of penetration. As you exceed structural cohesiveness, things start behaving as liquids. This even happens in explosives, where metal becomes essentially liquid due to the energies involved.

The potato's just not going to stay together.


That works for sabot rounds, but not apparently for rail guns, if they could make them.

Rail guns exist, the US navy has even had one mounted on a ship for some time. However, projectile physics work the same regardless of how you accelerate the projectile to that speed.

For things where a lot of penetration is desired, you generally use an extremely dense core for this reason. Tungsten, DU. High speed, dense core, longer round, those are the hallmarks of extremely high penetration weapons.

Honestly, even those materials wouldn't cope well with impacts at a substantial fraction of light speed, but a potato would do a good deal worse.

As for Yora's post...I agree. The grandiose sci fi ideas of the 50s and 60s are turning out to be a good deal harder than they were considered at the time. That said, I'll be quite happy to see us putting humans anywhere beyond earth's orbit, even if it's a relatively small scientific research station. Progress is progress, after all.

[Radar]

Ballistics begins to work oddly as you approach the speed of light. Even at relatively small fractions of it(getting anything of any decent size accelerated to that speed is hard), you start seeing density and size dominate over speed.

Given objects of equal density, you'll generally only get penetration equal to the projectile's length.

A potato not being particularly dense, it would be unlikely to penetrate very deep into the earth no matter how fast its going, and would instead essentially detonate. Assuming an earth with an atmosphere, this'll probably happen there, as despite the vastly lower density of the atmosphere, there's enough of it to stop the potato long before it gets to ground.

This'd result in a pretty impressive boom as all that energy gets converted to light, heat and sound. This would still probably be pretty bad for any unfortunate souls actually on the rock we're popping potatoes at.

I'm honestly not sure how this would work for specifically *at* light speed, but this approximation should work as you approach light speed, so it probably won't change dramatically by going a little bit faster. A potato is only so tough, after all.
Actually those penetration estimations do not work properly at relativistic speeds as they assume that objects cannot phase into each other. If you fling anything fast enough, the atomic forces will not be enough to keep the potato and the ground separate. So relativistic projectiles would penetrate the target deeper than it would be estimated from the Newtonian model (he was actually the one, who gave this simple estimation of penetration depth based on densities and length of the bullet).

[halfeye]

The potato's just not going to stay together.

It's not, but it will exist for a time, and in that time, due to its extreme speed, it will travel a very long way.


Rail guns exist, the US navy has even had one mounted on a ship for some time. However, projectile physics work the same regardless of how you accelerate the projectile to that speed.

Projectiles do work the same given the same speed. Sabot rounds are much slower than rail gun rounds would be. Last I knew rail guns were still experimental, if they aren't being fitted as standard in new vessels, I'd say they're still in the prototype stage of development.


For things where a lot of penetration is desired, you generally use an extremely dense core for this reason. Tungsten, DU. High speed, dense core, longer round, those are the hallmarks of extremely high penetration weapons.

That's tanks, but it wasn't WW1/2 battleships, they achieved penetration with very heavy shells, long yes, but wide too.

[factotum]

The potato's just not going to stay together.


I'm not sure that actually matters when every molecule in the potato is travelling fast enough to cause instant fusion with anything it hits, TBH. Plus, you said it yourself, the kinetic energy of the potato has to go *somewhere*, and since you can keep adding kinetic energy to the potato without upper limit (it just gets closer and closer to lightspeed as you do), something's gotta happen if, for example, you lob a potato with kinetic energy equivalent to the gravitational binding energy of the Earth into the planet.

[Forum Explorer]

Yeah, gravity in different directions effectively cancels out.*

For instance, if you are directly between the moon and the earth, there's a point where the gravity of the two cancels(much closer to the moon), and you'll experience zero g. This is one type of Langrage point.

There may be some slight variations, because gravity in practice is never exactly even, so there may be local areas where you can get marginally higher gravity than what Mars normally has, but this would be a very small effect, it's not going to be noticeable on a human level.

*in most cases. If the gradient is extremely high, such as while falling into a black hole, there are...severe effects. Mostly this won't matter on a planetary scale, though, and can be ignored.



Assuming such terraforming is possible, that would be cool, but it is probably not an easier problem than building a reliable space station. We've actually built space stations, scaling those up to bigger and better ones is a far smaller jump than going to planet scale terraforming.

Honestly, we haven't even gotten down management of earth's greenhouse effect. If we can't handle that, Venus's seems like hard mode.

Weird and fascinating. Pretty cool little factoid there.



Indeed.

And still, problems of such a magnitude are tiny in comparison to fixing an entire world such as Venus.

The effort required to nudge climate even a degree or two lower on a planetary scale is truly immense. Difficult to contemplate doing successfully even on the planet we're currently on. Even stopping the warming is a pretty big challenge, let alone reversing it.

Terraforming is weird because in a very real way, it's actually easier than doing minute adjustments to an already existing planet. Like, we can't cool Earth by bombarding it with asteroids, because that would be much much worse than the problem in the first place. And you don't need to worry about introducing something that'll take over the ecosystem because getting anything to live on the other planet is a pretty big success.

Though the other big thing is terraforming very much is still a dream. We are lacking in key technologies to even make it possible, and by the time we figure those out, terraforming may be pointless. While global warming is a very real and relevant threat that we can do something about today.

[Lord Torath]

Wait really? I thought being surrounded by all that mass would effectively put the pressure of the entire planet on you. Pressure is different from gravity. Pressure is from all the stuff above and around you being pulled down by gravity. At Earth's center of mass there is no gravity, but there is extreme pressure.

[Forum Explorer]

Pressure is different from gravity. Pressure is from all the stuff above and around you being pulled down by gravity. At Earth's center of mass there is no gravity, but there is extreme pressure.

Which is one of those things that makes perfect sense but still takes a few moments to wrap my head around.


And to bring it back to what got us on this subject: If you dig down, you experience more pressure, not gravity. A force acting against you can effectively act as an artificial gravity, kinda like how spinning a space station doesn't actually create gravity but the centrifugal force of the motion acts on your body like gravity would.

So how far down would you need to dig on Mars to have the pressure act to bolster the gravity you are experiencing?

[Aeson]

So how far down would you need to dig on Mars to have the pressure act to bolster the gravity you are experiencing?
Fluid pressure doesn't work like that; unless you're dealing with a very high pressure gradient, the net effect is essentially neutral - the fluid pushing "down" on you is also pushing "down" on the fluid around you, which causes the fluid around you to push "up" (and "in") on you and essentially cancel out the pressure pushing "down." The pressure is trying to squeeze you into a smaller you-shaped box, not alter your position in the fluid column.

If you are dealing with a very high pressure gradient, then the effect you would expect to see is that the parts of your body lower in the fluid column will be compressed, forcing your blood into the parts of your body higher in the fluid column, i.e. the pressure would be working against gravity; this is essentially how a g-suit works. Most likely, this would not be particularly beneficial to your long-term well-being; it certainly would not work to boost the apparent gravity of the planet to something closer to a standard gravity. If the pressure gradient is sufficiently extreme, you might even be able to "float" at a given level in the fluid column... but if you're in an environment with a pressure gradient that extreme, you're probably dead.

[Lord Torath]

If you are dealing with a very high pressure gradient, then the effect you would expect to see is that the parts of your body lower in the fluid column will be compressed, forcing your blood into the parts of your body higher in the fluid column, i.e. the pressure would be working against gravity; this is essentially how a g-suit works. Most likely, this would not be particularly beneficial to your long-term well-being; it certainly would not work to boost the apparent gravity of the planet to something closer to a standard gravity. If the pressure gradient is sufficiently extreme, you might even be able to "float" at a given level in the fluid column... but if you're in an environment with a pressure gradient that extreme, you're probably dead.A few examples: the pressure of 100 km of air1 = 10 m water = 760 mm liquid mercury (very roughly). The denser the liquid, the steeper the pressure differential. If you could stand in a vat or pool of mercury, your feet would experience roughly 2 atmospheres of pressure more than your head would. You can't though, as mercury is about 13 times denser than your body is2.

1. I should clarify that this is 100 km of air on Earth, where the air gets more diffuse as you go up it. Half that air pressure comes form the first 5.5 km of air.
2. I suppose someone could put you in a tube with just enough room for your body, put a lid on it, and then fill it full of mercury. The buoyant force would jam you pretty hard against the lid, though.

[Rakaydos]

Anecdotally, the Apollo astronauts who went to the surface of the moon had less bone and muscle deterioration than the ones that stayed in the command module- enough less to suggest there was actually some recovery from the trip out while they were down there. This suggests that even very low planetary gravities are better for human physiology than NO effective gravity.

A low orbit spin gravity station like the proposed Voyager Station (Formerly Von Braun Station) is easy to reach, but there is nothing THERE- everything has to be imported and/or recycled.

Mars surface is easier to reach than the lunar surface, thanks to aerobraking in even the thin martian atmosphere. It's easier to survive on mars with the right equipment and local resources, if things dont go horribly wrong. It's easier to ESCAPE the moon if things DO go horribly wrong.

As for Venus surface terraforming, the biggest problem is planetary rotation. Even the MOON has a faster day/night cycle (1 full day every month) than the surface of venus. (about 2 months of day and 2 months of night) You can imagine what that would mean for anything that would be living outdoors if you managed to solve all the other insolvable problems of terraforming venus.

Venus cloud cities are much more promising- due to atmospheric superrotation, the habitable band of the venus atmosphere has about 24 hours of day and 24 hours of night. And a breathable air mix is a lifting gas on venus. resources would have to be filtered from the air, which makes solids difficult to get, but energy would be plentiful. But it's not an approach we have much experience with.

[Yora]

Anecdotally, the Apollo astronauts who went to the surface of the moon had less bone and muscle deterioration than the ones that stayed in the command module- enough less to suggest there was actually some recovery from the trip out while they were down there. This suggests that even very low planetary gravities are better for human physiology than NO effective gravity.

They were in space for only 8 days. I didn't think the effect would be detectable that quickly.

[Nifft]

Anecdotally, the Apollo astronauts who went to the surface of the moon had less bone and muscle deterioration than the ones that stayed in the command module- enough less to suggest there was actually some recovery from the trip out while they were down there. This suggests that even very low planetary gravities are better for human physiology than NO effective gravity.

Or that being depressed about not actually walking on the moon makes your muscle deterioration worse.

[Tyndmyr]

As for the potato thing, I suppose I am picking nits a bit. We certainly agree that it would be a very bad thing for the planet regardless, and it is a touch off topic. Back to settlement!


Anecdotally, the Apollo astronauts who went to the surface of the moon had less bone and muscle deterioration than the ones that stayed in the command module- enough less to suggest there was actually some recovery from the trip out while they were down there. This suggests that even very low planetary gravities are better for human physiology than NO effective gravity.

A low orbit spin gravity station like the proposed Voyager Station (Formerly Von Braun Station) is easy to reach, but there is nothing THERE- everything has to be imported and/or recycled.

The big issue is, well, the gravity well. The rocket equation is brutally hard on lift, and getting mass to space stations is already expensive enough. Getting material to say, Mars or Venus is ludicrously expensive. Even Musk is optimistically projecting $4bil for a minimally manned exploration trip to Mars. That's far short of what's needed for actual settlement.

By contrast, launch prices for a Falcon 9 into LEO are now sub-$3k/lb. That isn't cheap, certainly, but if you want stuff, being able to ship a lot more is amazingly helpful.

And then, once it's built, you can go from the station to elsewhere far more cheaply than you can from the surface of a planet. Going back down into a gravity well makes it really hard to move onward from there.

[Yora]

I'm always amazed at the difference in size between the vehicle that took astronauts to the moon, and the vehicle that got them back from the moon.

[Fat Rooster]

The big issue is, well, the gravity well. The rocket equation is brutally hard on lift, and getting mass to space stations is already expensive enough. Getting material to say, Mars or Venus is ludicrously expensive. Even Musk is optimistically projecting $4bil for a minimally manned exploration trip to Mars. That's far short of what's needed for actual settlement.

By contrast, launch prices for a Falcon 9 into LEO are now sub-$3k/lb. That isn't cheap, certainly, but if you want stuff, being able to ship a lot more is amazingly helpful.

And then, once it's built, you can go from the station to elsewhere far more cheaply than you can from the surface of a planet. Going back down into a gravity well makes it really hard to move onward from there.

The thing about a trip to Mars is that a visit isn't much easier than a settlement. You can go to the moon with just a fortnight of supplies, but even just getting to Mars will mean you need systems which don't rely on consumables. That $4 bil already includes robotic ISRU of water in the plan (for propellant, but easily diverted to other uses), and to get the CO2 for methane you need to be processing the atmosphere, so you will already be producing nitrogen as a by-product. Compact processes exist that can turn methane into ethylene (https://siluria.com/Technology/Oxidative_Coupling_of_Methane), and from there you can begin polythene part production using 3d printing as well as more specialised processes (material for polytunnels). The extra equipment required to become entirely self sufficient is a small percentage of the equipment already required just to survive and get home.

A metal industry is slightly harder, but one of the advantages of using stainless steel is that it can easily be recycled. Lets say you land 3 vehicles. You only need 1 of those to get home, so cutting up the other two for parts makes sense. Even without additional industry that is 200 tons of high quality raw materials. That should be enough to bootstrap a foundry.

If you can visit for $4 bil I would estimate you could probably establish a basic settlement for $6 bil. For $8 bil* you could do it relatively safely, taking enough supplies with you to ensure the crew don't starve before the next window to come home. Water and air recycling are a required risk even for a visit, and the robotic ISRU should have your return propellant ready before you even set off, meaning you can be confident of your ability to create methane (especially if you have a man** with a spanner on site).

The other thing you are neglecting is the increased cost of a rotating station. If it is rotating it needs to be structural, and that means heavy. All that material has to be brought from somewhere, probably a gravity well. You are then building your structures out of extra material that you have brought out of a gravity well rather than just building in the gravity well. Sure, it will suck to get people on and off it, but how many times do you reckon you can fly a person up and down before it becomes less efficient that flying up their entire house? If it is actually meant as a colony most people will not be moving particularly frequently, so ease of construction dominates over ease of movement.

* All these numbers are highly optimistic, but I think the ratios are about right.
**Or woman. Person with a spanner doesn't have the same ring to it though.

[Tyndmyr]

Well, there's a few things that pose problems for settlement. First off, lifespan. Pretty much everything has a finite lifespan, and while redundancy is always attempted in spaceflight, the longer the trip, the more you need.

Second, a genuine settlement isn't just a few people waiting for death. You need enough people to have kids that aren't wholly inbred, and keep the population goin'. We're not sure exactly what the minimal population is for humans, but perhaps 100-200 would be a decent bet, and more gives you more genetic diversity in case of accident. Certainly the number is a good deal higher than the couple people going to visit it(I believe the current tenative plan is six).

Rotating doesn't have to actually be heavy. You can separate pods with a cable and spin 'em, at the simplest. You've only got to worry about tensile strength, and cables are pretty good at that.

And of course, fairly few of the goods needed by a settlement are available locally. A few raw materials, perhaps. Even there, the selection is fairly limited, and things like fumes matter inside an enclosed environment.

Consider that even food isn't the sort of thing that the ISS is self sufficient on. You're gonna have to feed these folks, probably for a long time.

Comms to orbit are also a lot faster and more stable than comms to mars/venus.

You could put a station nearly double the size of the ISS into orbit given current launch costs for the price of that one time visit to mars.

Compared to colonizing mars? You could have a space station that looks like something from wild science fiction.

For reference, the ISS can hold a permanent crew of 6, plus a few visitors, and is approximately the equivalent of a 6,000 square foot house.

[Nifft]

As for the potato thing, I suppose I am picking nits a bit. We certainly agree that it would be a very bad thing for the planet regardless, and it is a touch off topic. Back to settlement!
You're not really picking nits.

The assertion was: "one potato at sufficient velocity could vaporize the Earth", and trying to find flaws in how it got that velocity isn't attacking the thing which I actually said -- I had never given you any implementation details on how it got to that velocity, after all.



The big issue is, well, the gravity well. The rocket equation is brutally hard on lift

The key thing here is to launch from higher in the well.

I'm honestly not sure why we keep building launchpads at sea level* instead of on the top of a mountain. We have access to a significant number of mountains, and we could find quite a few more with international cooperation.

But for Mars, I think the gravity well sweet-spot is the Moon.

We'd want to establish a moon base or several, process regolith and moon-rocks into a railgun-type launch system, forge hefty station parts and then launch them to an orbit where they could be easily assembled, and build the chonky radiation-resistant system-ship hulls out there instead of on the Earth.

Some of this could probably be done by robots which are launched from Earth, but hopefully we'll get a breeding population of humans up there too.



*) Well, other than the politics of throwing money at specific states, but I don't like that reason.

[Tyndmyr]

You're not really picking nits.

The assertion was: "one potato at sufficient velocity could vaporize the Earth", and trying to find flaws in how it got that velocity isn't attacking the thing which I actually said -- I had never given you any implementation details on how it got to that velocity, after all.

The implementation is definitely the challenging part for sure. But hey, fun concept at any rate.


The key thing here is to launch from higher in the well.

I'm honestly not sure why we keep building launchpads at sea level* instead of on the top of a mountain. We have access to a significant number of mountains, and we could find quite a few more with international cooperation.

That would help quite significantly. Unfortunately, the Earth's geography is unsuited for it.

Essentially, to get into orbit, you gotta fly up out of the atmosphere, then pile on a ton of sideways speed to hit orbital velocity. Rotate a sphere, and the edge will be moving at a higher speed than any other part.

That's why everyone attempts to launch as close to their equator as other factors reasonably allow, and the US launches from Florida. More of that rotational speed to start. Height helps in that it decreases the atmospheric climb, but we have a tragic shortage of mountains along the equator, and that factor is huge.


But for Mars, I think the gravity well sweet-spot is the Moon.

We'd want to establish a moon base or several, process regolith and moon-rocks into a railgun-type launch system, forge hefty station parts and then launch them to an orbit where they could be easily assembled, and build the chonky radiation-resistant system-ship hulls out there instead of on the Earth.

Escaping from the Moon isn't *that* bad. The gravity is quite light, and there's really no atmosphere. It's still non-trivial, but it's 20-odd percent of the escape velocity from earth.

Unfortunately, the regolith is very poor in most materials. There's quite a lack of water, which gets used in an immense amount of processes, for instance. There's no atmosphere, so any of the lighter gasses are pretty inaccessible as well. Even stuff like Carbon, readily accessible on earth, pretty scarce there. This makes fabrication of rockets from local materials extremely challenging.

On top of that, the dust is highly abrasive, which might create a lot of problems for a launch site. Every rocket taking off would tend to sandblast the launch site.

Doesn't mean that a lunar base isn't worthwhile at all...for what we can use from there, harvesting locally may be cheaper to truck out to orbit than lugging it up from earth, particularly if things like a railgun launcher can be made to work in the environment. But probably more likely to be a mining station than a launch facility.

[Yora]

I believe most proposals for moon manufacturing assume a supply of material from asteroids.

I'm really not an expert on these things, but I think it should be possible to have rockets and launch pads that channel all the exhaust and debris away from the rocket.

The whole idea behind building spacecraft on the moon, or at least transfer heavy vehicle parts from the surface into orbit around the moon, is that the energy requirement is much lower per kg of payload, which means the rockets that go from the moon into space and then beyond can be much smaller and less powerful.

1: Send parts for the processing of asteroid ore and the construction of lunar launch rocket to the moon.
2: Assemble a rocket factory on the moon.
3: Push metal-rich asteroids to land on the moon.
4: Build rockets for travel throughout the solar system on the moon.
5: Send the rocket into orbit around Earth,
6: Lift only crew, supplies, and advanced electronics from Earth to the waiting rocket.
(7: Profit)

In theory, with sufficiently advanced and efficient rocket factories and fuel refineries on the moon, the costs for getting space ships into space becomes much smaller.
A Saturn V had a fueled up weight of 3000 tons, of which only 50 tons were actually going to the moon. We can build better rockets now, but the energy requirements remain largely the same and we still don't have anything massively better than RP1,
I don't feel confident with plugging in numbers into the rocket equation, but it would be interesting to see how much of the most efficient fuel on the hypothetically most efficient rockets would be needed to get say 10 tons from both the Earth and the Moon into orbit. Looking at a Saturn V and a Lunar Module, I suspect the difference is mind-boggling.

[halfeye]

Looking at a Saturn V and a Lunar Module, I suspect the difference is mind-boggling.

Saturn 5 was huge, but the mass a Saturn 5 put into orbit was pretty excessive too. The whole third stage of a Saturn 5 went to orbit, full of propellant, to get the astronauts to the Moon relatively quickly.

[Tyndmyr]

I believe most proposals for moon manufacturing assume a supply of material from asteroids.

Astroid mining would be inordinately useful, but sending it back down into any gravity well represents an efficiency loss if you're using it for spaceflight.

Earth is a deeper well than the moon, certainly, but both require quite a lot of propellant just to get back up to orbit, a cost that an orbital station doesn't incur.


I'm really not an expert on these things, but I think it should be possible to have rockets and launch pads that channel all the exhaust and debris away from the rocket.

Mostly, certainly, but it tends to sandblast the station itself. Whatever systems you have, to include exaust management systems, are going to take some brutal wear and tear.


I don't feel confident with plugging in numbers into the rocket equation, but it would be interesting to see how much of the most efficient fuel on the hypothetically most efficient rockets would be needed to get say 10 tons from both the Earth and the Moon into orbit. Looking at a Saturn V and a Lunar Module, I suspect the difference is mind-boggling.

A given rocket can lift approximately 6 times as much payload from the moon as from earth into orbit. Earth LEO is usually used as a rough standard.

For comparison, the Saturn V can lift 260,000 lbs to Earth LEO, whereas the Falcon Heavy can lift only 141,000. The latter is *far* cheaper, though, so it represents a massive cost savings.

The current ISS is only about 925,00 lbs, though. So, from a payload perspective, we most certainly could build a larger one at present, and at a higher orbit than the ISS is at(it's quite low).

Rough ballpark, every Falcon launch could lift roughly enough station mass to support one additional permanent crew member. There have been over a hundred launches so far. We could certainly aim higher.

[factotum]

I think if you were planning on building a permanent inhabited station in orbit (e.g. one on which you expect people to actually live their lives on) then you'd want to have it quite a bit higher than the ISS, which has to have its orbit boosted every couple of months due to atmospheric drag--a problem that just gets worse the larger the mass of the station, because you need more fuel to make the boost burns.

[Tyndmyr]

I think if you were planning on building a permanent inhabited station in orbit (e.g. one on which you expect people to actually live their lives on) then you'd want to have it quite a bit higher than the ISS, which has to have its orbit boosted every couple of months due to atmospheric drag--a problem that just gets worse the larger the mass of the station, because you need more fuel to make the boost burns.

Once you've gotten big enough to solve the shielding problem, definitely. I suspect shielding is the main reason for the current altitude.

Just having lots and lots of mass for the periphery would help with that a great deal. Big ol' water tanks and such. They sort of double as armor for micrometeorite strikes too. If you go big, you have to store a lot of stuff somewhere, you might as well stash it where it provides useful shielding.

That said, building at roughly the ISS altitude and boosting it later isn't a showstopper. Drag should scale roughly on the cross section of the station, not on density. Assuming you're building in 3 dimensions, the square cube law works in your favor, and drag scales much more slowly than mass.

[halfeye]

Once you've gotten big enough to solve the shielding problem, definitely. I suspect shielding is the main reason for the current altitude.

Just having lots and lots of mass for the periphery would help with that a great deal. Big ol' water tanks and such. They sort of double as armor for micrometeorite strikes too. If you go big, you have to store a lot of stuff somewhere, you might as well stash it where it provides useful shielding.

That said, building at roughly the ISS altitude and boosting it later isn't a showstopper. Drag should scale roughly on the cross section of the station, not on density. Assuming you're building in 3 dimensions, the square cube law works in your favor, and drag scales much more slowly than mass.

The mass though is exactly the thing that resists acceleration to a higher orbit.

[Nifft]

ISS should have big wings, set far below it in the atmosphere, like an orbital hydrofoil.

[LibraryOgre]

ISS should have big wings, set far below it in the atmosphere, like an orbital hydrofoil.

I agree, 100%. (https://youtu.be/h3HLM9NHRHg)

[Tyndmyr]

I have no idea if that's practical or not, but it sounds seriously awesome. Reason enough right there, I think.

[Lord Torath]

It's really not. Practical, I mean.

Wings trade thrust for lift and drag. The lift would keep the station steady at a given velocity, but the drag would rapidly diminish that velocity, thus reducing the lift. The wing would start descending farther into the atmosphere, further increasing the drag, and eventually the entire station would be pulled down into the atmosphere. To avoid that, you'd need a constant source of thrust to overcome the drag force.

Plus, the air is really thin up there, so at orbital speed, the wings would be supersonic. Dragging a shock wave along with you is a great way of converting velocity into waste heat, which just requires even more energy poured into your thrusters. It's much more economical to occasionally burn some fuel to boost the ISS into a slightly higher orbit than to constantly burn it to maintain the same average orbit.

[factotum]

Plus, the air is really thin up there, so at orbital speed, the wings would be supersonic.

From what I remember, part of the definition for what makes "space" (usually outside America the Kármán line at 100km altitude) is that a typical aircraft would have to be travelling so fast there for its wings to generate enough lift to keep it aloft that it would be at orbital velocity anyway.

[Tvtyrant]

Astroid mining would be inordinately useful, but sending it back down into any gravity well represents an efficiency loss if you're using it for spaceflight.

Earth is a deeper well than the moon, certainly, but both require quite a lot of propellant just to get back up to orbit, a cost that an orbital station doesn't incur.



Mostly, certainly, but it tends to sandblast the station itself. Whatever systems you have, to include exaust management systems, are going to take some brutal wear and tear.



A given rocket can lift approximately 6 times as much payload from the moon as from earth into orbit. Earth LEO is usually used as a rough standard.

For comparison, the Saturn V can lift 260,000 lbs to Earth LEO, whereas the Falcon Heavy can lift only 141,000. The latter is *far* cheaper, though, so it represents a massive cost savings.

The current ISS is only about 925,00 lbs, though. So, from a payload perspective, we most certainly could build a larger one at present, and at a higher orbit than the ISS is at(it's quite low).

Rough ballpark, every Falcon launch could lift roughly enough station mass to support one additional permanent crew member. There have been over a hundred launches so far. We could certainly aim higher.

I think the major argument is you can actually make a space elevator on the moon without it tearing apart, or getting shot by rogue missiles.

[halfeye]

I think the major argument is you can actually make a space elevator on the moon without it tearing apart, or getting shot by rogue missiles.

I sort of like the idea of a space elevator on the Moon, but. The thing about space elevators is they have to be near the equator. All of the water that we know of at the Moon is at the poles, it's a long way from the poles to the equator, even on the Moon, it's further on Mars (where I think the known water is also near the poles).

[Lord Torath]

For anyone who's interested, Blue Origin is going to try spinning up some centrifugal gravity in orbit: NASA and Blue Origin upgrading New Shepard spacecraft for artificial gravity (https://www.syfy.com/syfywire/nasa-and-blue-origin-upgrade-new-shepard-for-artificial-gravity).

All sorts of opportunities for testing the effects of spun-up low gravity (1/6 G).

[Yora]

I think it sounds like it's more about getting a capsule to really high suborbital altitude and then having it spin while it's dropping back to Earth, before it has to start breaking.
Using a sub-orbital rocket instead of a ridiculously tall crane.

[sihnfahl]

I think it sounds like it's more about getting a capsule to really high suborbital altitude and then having it spin while it's dropping back to Earth, before it has to start breaking.
Which makes sense, as it's utilizing its RCS to start the spin. Limited fuel means they'll do everything to ensure the rocket and its payload return to earth. So spinning in a deliberately quickly decaying orbit....

[halfeye]

Which makes sense, as it's utilizing its RCS to start the spin. Limited fuel means they'll do everything to ensure the rocket and its payload return to earth. So spinning in a deliberately quickly decaying orbit....

It's not in any sense an orbit. What that thing does is take people straight up to the edge of space, and drops straight back down again. It doesn't get anywhere near orbital speeds, which would require serious and expensive heat shielding, which it doesn't have, because it doesn't need them, because it doesn't go that fast. It's a cheap and nasty "almost there", except that it isn't really almost there at all.

[Tyndmyr]

For anyone who's interested, Blue Origin is going to try spinning up some centrifugal gravity in orbit: NASA and Blue Origin upgrading New Shepard spacecraft for artificial gravity (https://www.syfy.com/syfywire/nasa-and-blue-origin-upgrade-new-shepard-for-artificial-gravity).

All sorts of opportunities for testing the effects of spun-up low gravity (1/6 G).

Oooh, thanks for sharing! It's not a full on station, but hey, experiments make sense. I'll definitely keep an eye out for any interesting findings.

[LibraryOgre]

I think, Mars for colonisation and Venus for terraforming.

I realize it is a bad idea for any number of reasons, but I've long wondered about developing an extremeophile bacteria that could survive Venus's upper atmosphere and start to use photosynthesis to convert Venus's atmosphere.

[halfeye]

I realize it is a bad idea for any number of reasons, but I've long wondered about developing an extremeophile bacteria that could survive Venus's upper atmosphere and start to use photosynthesis to convert Venus's atmosphere.

Hopefully, it's a matter of finding rather than developing because I don't think we can do that yet. A lichen might be good if it exists, but it would need to break off daughters rather than grow, because growing would take it down.