What do you guys think of orbital colonies?

[MonkeySage]

I was thinking, if we could get even one colony out, what might that lead to? How would we do it?

To be clear, I'm not talking about colonizing a planet; planetary colonization means terraforming and all that long haul stuff.

[Wilko]

Actually i think orbital colonies would be a necessary step in terraforming.

- Build an "Orbital Colony".

- Move it to the planet to be Colonized.

- Park it in orbit.

- Live there While you do the terraforming / setup the on the ground colony.

But honestly there are a lot of issues to be worked out before this could be feasible, you would need to get a LOT of material into orbit, any kind of permanent living arrangement in space is going to need gravity and won't get away with the cramped living spaces you see on things like the ISS, you need to find a self sustaining solution for the Oxygen / Food / Water issues... and even then you need to start mining the asteroid belt or something to get raw materials to keep the station repaired...

Personally I see it starting with business, something like asteroid mining being setup with a rotation of staff not unlike oil rigs and the like on earth 6 months on 6 off.

[ace rooster]

Actually i think orbital colonies would be a necessary step in terraforming.

- Build an "Orbital Colony".

- Move it to the planet to be Colonized.

- Park it in orbit.

- Live there While you do the terraforming / setup the on the ground colony.

But honestly there are a lot of issues to be worked out before this could be feasible, you would need to get a LOT of material into orbit, any kind of permanent living arrangement in space is going to need gravity and won't get away with the cramped living spaces you see on things like the ISS, you need to find a self sustaining solution for the Oxygen / Food / Water issues... and even then you need to start mining the asteroid belt or something to get raw materials to keep the station repaired...

Personally I see it starting with business, something like asteroid mining being setup with a rotation of staff not unlike oil rigs and the like on earth 6 months on 6 off.

Actually the issues you raise are the reason I think orbital colonies are more feasible than surface ones. Getting stuff into orbit is prohibitively expensive, but if you are mining asteroids you sidestep that entirely. In particular conditions can be much less cramped once materials are cheap. Manufacturing is often much easier in microgravity, and if you need gravity for a process you can put the assembly in a centrefuge, which can be tuned to requirements. Large machines (including centrefuges) can be much simpler if they don't have to support their own weight. On top of making your life more difficult by insisting on a surface, you also make exporting much more difficult. Unless you are looking for something very specific and valuable, I don't see much reason for surface colonies.


Personally I fully expect to see an orbital semiconductor foundery in my lifetime. Whether it will have a permenent staff or not remains to be seen.

[factotum]

I'm not so sure that an orbital colony in orbit around Earth makes much sense. It would have to be *much* higher than the ISS in order to avoid the problems of atmospheric drag (you can't attach a small rocket to a giant colony and expect it to do much) and would thus need a lot more energy to get it up there. Conversely, if you're building it out of recycled asteroid material, you have to expend vast amounts of energy to get the stuff down into low Earth orbit! You couldn't even use a proper orbital colony for zero-gee manufacturing, because, as already pointed out, a colony where people are staying for more than a few months would have to have gravity of some sort.

A colony further out into the Solar System, say in the asteroid belt? That would be a far more reasonable proposition--if you're spending months travelling between the inner and outer solar system, having a habitable port of call along the way that doesn't require you to enter and exit a gravity well would be a fine thing indeed.

[Douglas]

A colony in Earth orbit could be useful for research and zero-g manufacturing. And yes, even a "proper colony" with Earth-level local gravity could be used for zero-g manufacturing because it would be trivial to design it with different gravity in different sections. Whether it would be worth the cost depends a lot on how valuable the advantages of zero g are for manufacturing, which I lack the specialized knowledge to meaningfully speculate on.

A colony in orbit around some other planet has greater research potential but less Earth-relevant manufacturing utility, but could also provide an anchor point to organize terraforming efforts around. I'm not sure an orbital base would actually be better than a ground one for terraforming, though.

An asteroid base, oriented towards mining, strikes me as likely the highest value idea so far. You'd need to find the right asteroids to target, but a lot of the densest elements have the overwhelming majority of their Earth-based presence in the mantle or core, simply because their density made them sink. That effect should not apply to asteroids, and a few giant deposits of gold and other rare high-number elements could make the cost of bringing them back to Earth's gravity well worth it. And once that basic infrastructure is in place, having a source for more basic materials that's already out of any big gravity wells would become valuable.

[Kato]

Actually the issues you raise are the reason I think orbital colonies are more feasible than surface ones. Getting stuff into orbit is prohibitively expensive, but if you are mining asteroids you sidestep that entirely.

If by "sidestep entirely" you mean "you will have a few pieces of stuff you can use if you get lucky" :smalltongue: I mean, sure, using asteroids instead of hauling everything up is a great idea but you won't find everything in asteroids. Unless there are a bunch of plastic and/or oil asteroids up there nobody told me about. And a bunch of other things not commonly found in space.

So, in general, space colonie are a great idea, imo much more feasible than any kind of terraforming I've heard about so far, but it brings a long a huge load of problems. Building stuff in space is easier(-ish) because no gravity but you still need materials, tools, workers (or at least robots), you need radiation shielding, you will need at some point artificial gravity (which is not that hard I guess but still). I'm not saying it can't be done but right now it would be really stretching our abilities to its limits and there's just not enough merit. Give it a few decades and maybe we will get a great idea how to make some thing(s) easier.

[Douglas]

If by "sidestep entirely" you mean "you will have a few pieces of stuff you can use if you get lucky" :smalltongue: I mean, sure, using asteroids instead of hauling everything up is a great idea but you won't find everything in asteroids. Unless there are a bunch of plastic and/or oil asteroids up there nobody told me about. And a bunch of other things not commonly found in space.
Yeah, anything with an organic origin is going to be scarce or nonexistent in asteroids, but there's a lot of elements, and maybe even minerals, that they should be relatively rich in.


So, in general, space colonie are a great idea, imo much more feasible than any kind of terraforming I've heard about so far, but it brings a long a huge load of problems. Building stuff in space is easier(-ish) because no gravity but you still need materials, tools, workers (or at least robots), you need radiation shielding, you will need at some point artificial gravity (which is not that hard I guess but still). I'm not saying it can't be done but right now it would be really stretching our abilities to its limits and there's just not enough merit. Give it a few decades and maybe we will get a great idea how to make some thing(s) easier.
Radiation shielding is definitely going to be a major issue. Most people have no idea just how much Earth's magnetic field and atmosphere do to protect us all, but it's a lot.

[HandofShadows]

Yeah, anything with an organic origin is going to be scarce or nonexistent in asteroids, but there's a lot of elements, and maybe even minerals, that they should be relatively rich in.

Well they have found organic molecules in comets. Also they are a source of water.



Radiation shielding is definitely going to be a major issue. Most people have no idea just how much Earth's magnetic field and atmosphere do to protect us all, but it's a lot.

This is a huge problem. Unless you have very good particle shielding, space colonies will be in for insurmountable problems in the long term. (cancer, infertility and premature aging.) You have that maybe they would be worth something for zero G manufacturing and resource reclamation. Getting stuff from deep space to colony doesn't take huge amounts of energy. But doing it safely will be the big problem.

[Yora]

I think space habitats are the only form of extraterrestrial settlement we're going to see in the forseeable future. (Pending 10%+ light speed engines.)
Main reason is gravity. Human bodies need the right amount of gravity to function and especially to develop. Health conditions for prolonged stays on Mars or any moons would be terrible. The only thing in the solar system with comparable gravity is Venus, and surface conditions make anything but floating sky cities impossible. However, through rotation you can create an even 1G force towards the floor inside a space habitat without any fancy physics or engineering. The only obstacle is getting the building material up into space as they would have to be pretty big.
But once you have the first few done, you could use them as factory sites to create the building materials for more stations from asteroid mining. Iron and ice (for water and oxygen) are plenty in many asteroids. The iron processing machines could perhaps be cooled with ice and the steam then vented into space so that the station won't overheat.

The beauty of it all is that it does not require any purely hypothetical discoveries in physics or fictional technologies, or take several centuries to implement. The only reason we're not started with it yet is money. (And lack of a reason for people to leave Earth.)

[GuesssWho]

I honestly feel like we should fix things here on Earth before we start living in space. Otherwise we'll just become a horde of locusts, using up whole worlds.

[Winter_Wolf]

I honestly feel like we should fix things here on Earth before we start living in space. Otherwise we'll just become a horde of locusts, using up whole worlds.

I find it easier to believe that humanity could pull off locust hordes before even getting close to fixing Earth problems. Per the gist of another thread I was reading, the reason we aren't finding other life in the universe might just be that they're all hiding because humans are so freaking terrifying. I find the thought incredibly amusing.

[Brother Oni]

I find it easier to believe that humanity could pull off locust hordes before even getting close to fixing Earth problems. Per the gist of another thread I was reading, the reason we aren't finding other life in the universe might just be that they're all hiding because humans are so freaking terrifying. I find the thought incredibly amusing.

There's a whole genre of fiction based on that concept, although it's typically called "Humanity **** Yeah!" on the internet. The oldest one I know of is 'Victory Unintentional' by Asimov, which is a fun little short story.

Another short story I like is about humanity exploring space but finding nothing, until they eventually come across an alien space ship, which promptly flees from the humans. After a few bumpy first contacts where we get outclassed, the various alien races think we're an easy target with our technology level and backcalculate our ships' trajectories then immediately nope out of the idea of attacking and looting Earth.
Apparently Earth is located in the middle of a giant space Bermuda Triangle, which invariable sends all who enter insane after a while. Humans however appear to be immune to the effect for some reason (or maybe we're just crazy to begin with) and after a while, humanity takes up the role of galactic boogeyman and settle down to (mostly) peaceful contacts, although they do keep their reputation up by having a few too many spikes, skulls and scary colour schemes on their clothing and ships.

[Grinner]

I find it easier to believe that humanity could pull off locust hordes before even getting close to fixing Earth problems.

Meh. Shouldn't be difficult with a little genetic engineering. :smalltongue: Amp up serotonin production so that they remain in swarming phase and maybe add some transgenic immunity to pesticides.

[georgie_leech]

There's a whole genre of fiction based on that concept, although it's typically called "Humanity **** Yeah!" on the internet. The oldest one I know of is 'Victory Unintentional' by Asimov, which is a fun little short story.

Another short story I like is about humanity exploring space but finding nothing, until they eventually come across an alien space ship, which promptly flees from the humans. After a few bumpy first contacts where we get outclassed, the various alien races think we're an easy target with our technology level and backcalculate our ships' trajectories then immediately nope out of the idea of attacking and looting Earth.
Apparently Earth is located in the middle of a giant space Bermuda Triangle, which invariable sends all who enter insane after a while. Humans however appear to be immune to the effect for some reason (or maybe we're just crazy to begin with) and after a while, humanity takes up the role of galactic boogeyman and settle down to (mostly) peaceful contacts, although they do keep their reputation up by having a few too many spikes, skulls and scary colour schemes on their clothing and ships.

What I loved about that how story was that Humanity's reaction to finding about this was "sure, why not? It keeps the meanies away." :smallbiggrin:

[factotum]

Another short story I like is about humanity exploring space but finding nothing, until they eventually come across an alien space ship, which promptly flees from the humans.

I recall one where the first human interstellar exploration craft runs into a bunch of aliens who welcome them aboard and tell them a story, about a race who were so brilliant and so dangerous that they'd had to be genocided by the other races thousands of years earlier. The twist in the tale is obviously that this race were humans, and the crew of the ship get killed at the end--the aliens don't manage to find Earth, though.

[HandofShadows]

I recall the story "Danger Human (http://www.baenebooks.com/chapters/0743471741/0743471741___1.htm)" where some aliens kidnap a human to figure out why they are supposed to be so dangerous. (The Earth has a label on saying "Danger Human" but no real explanation of why).

[Brother Oni]

I recall the story "Danger Human (http://www.baenebooks.com/chapters/0743471741/0743471741___1.htm)" where some aliens kidnap a human to figure out why they are supposed to be so dangerous. (The Earth has a label on saying "Danger Human" but no real explanation of why).

I find it highly entertaining that humanity among the stars runs the whole gamut from 'fabled space monster' (With Friends Like These by Alan Dean Foster is another good one) to 'newcomer race but respectable if we can control our tendencies' (the vast majority) to 'Mostly Harmless (https://en.wikipedia.org/wiki/The_Hitchhiker%27s_Guide_to_the_Galaxy)'.

[Storm_Of_Snow]

I was thinking, if we could get even one colony out, what might that lead to? How would we do it?

To be clear, I'm not talking about colonizing a planet; planetary colonization means terraforming and all that long haul stuff.
More like finding something close enough to Earth-like that your investment is as small as possible - a sealed base would only be if absolutely necessary (eg, the mineral resources mined from the planet would pay for it many times over, you need a base in that particular system for military, scientific or infrastructural reasons, and so on), and terraforming would really be nothing more that showing off that you can do it.

With one orbital colony, chances are you'd have enough infrastructure in orbit to be able to build more, and then you'd likely get different habitats specialising in industries (breaking down captured asteroids and refining the ores, growing crops and so on), with the possibility that some could be sent off to orbit other bodies. The problem is getting enough mass into orbit to build the first colony, which probably needs something like a beanstalk or some other way of making it cheaper.

[Swordsmith]

I think a lunar colony makes more sense than an orbital colony at the moment.

We would have access to a LOT of raw materials relatively cheaply if we could use stuff just lying around on the ground near us, we'd have a huge gravity generator handy that would require no moving parts to operate, unlike centripetal methods. We'd have access to a lot of shielding material just by digging our habitat into holes.

Sure, there are lots of materials we don't have an easy way to extract from lunar rock/soil, but we can't get those out of the vacuum of space either, we have to bring those along to both destinations. If we can get say 90%* of what we need from lunar materials (in terms of sheer mass, that is) then we're probably a lot better off with that than building something of our own in earth orbit or at a Lagrange point, despite having to build some sort of landing device instead of just docking.

The down side is we'd have to climb back out of Luna's gravity well to get home, but since the vast bulk of the materials we'd transport there we'd be happily leaving there, I don't know that that's a huge problem either.

If we want to build an orbital habitat, it would probably make sense to use lunar materials for construction, since it's much easier to get that out of the gravity well than it is to lift it from earth. A colony and mining operation would be a good start for that project.

Asteroids are an attractive alternative, but A) they don't come with significant gravity, B) I don't know how the cost of shifting them into a suitable orbit would be C) I'm concerned about the possibility of an accident or sabotage resulting in an extinction event for Earth. Plus, D) they're really kind of a crapshoot, while we can do a lot of preliminary exploration of Luna to find suitable resources much more cheaply and easily.

* I have no idea what % of needed materials would actually be found on Luna. But I'm betting it's really high, if we work on the idea of using lunar rock as construction materials and mining metals and making glass to form more critical components.

[halfeye]

I like the idea, but they need to be stable. LEO isn't stable, there's too much dangerous trash, and enough atmosphere that orbits naturally decay in years or less.

Near lunar is probably good, but if near why not on the Moon? There probably ought to be at least one habitat in orbit around the Moon, but there ought to be a relatively big base on it as well.

Apparently some people in NASA want to dump the ISS, I don't like that idea, it has a motor (it would have crashed to Earth before now without), it should be moved to wherever a spacestation is wanted, it'd be slow, but it has a lot of facilities and materials that could be used. Possibly anything in lunar space would need more radiation shielding than the ISS has, but it has a lot of refined metal and electronics in it, and just throwing that away when it's rare up there would be silly IMHO. I didn't like Skylab crashing, and this would be equally wasteful and shortsighted.

[Flickerdart]

Apparently some people in NASA want to dump the ISS, I don't like that idea, it has a motor (it would have crashed to Earth before now without), it should be moved to wherever a spacestation is wanted, it'd be slow, but it has a lot of facilities and materials that could be used.
The ISS is getting dumped for the same reason Mir got dumped - it's getting old and funding is not going to be around forever. Because it's modular, the plan is to reuse the useful components on other space stations and drop all the obsolete stuff into the ocean.

[Spojaz]

Near lunar is probably good, but if near why not on the Moon? There probably ought to be at least one habitat in orbit around the Moon, but there ought to be a relatively big base on it as well.

The moon is a bad place. It has all the challenges of an orbital station, (low gravity atrophy, no atmosphere, solar and deep space radiation, micrometeorites etc.) and a few of its own. Day and night last for 15 days each, meaning you have to spend a lot of energy constantly oscillating from heating to cooling.

There is also lunar regolith (https://en.wikipedia.org/wiki/Adverse_health_effects_from_lunar_dust_exposure), the "moon dust". The particles of which are sharp and tiny enough to reach the brain, are electrically charged to levitate during the day, and contain chemicals that become poisonous and corrosive when in contact with moisture. NASA ranked "dust" as the biggest challenge to a mars mission in 2005, and mars's dust is partially mitigated by its atmosphere. Regolith is also dense but unstable in the low gravity, so to build something permanent you would have to dig the supports to bedrock.

The moon is only good for anything when you still have your feet on the Earth.

[ace rooster]

I think a lunar colony makes more sense than an orbital colony at the moment.

We would have access to a LOT of raw materials relatively cheaply if we could use stuff just lying around on the ground near us, we'd have a huge gravity generator handy that would require no moving parts to operate, unlike centripetal methods. We'd have access to a lot of shielding material just by digging our habitat into holes.

Sure, there are lots of materials we don't have an easy way to extract from lunar rock/soil, but we can't get those out of the vacuum of space either, we have to bring those along to both destinations. If we can get say 90%* of what we need from lunar materials (in terms of sheer mass, that is) then we're probably a lot better off with that than building something of our own in earth orbit or at a Lagrange point, despite having to build some sort of landing device instead of just docking.

The down side is we'd have to climb back out of Luna's gravity well to get home, but since the vast bulk of the materials we'd transport there we'd be happily leaving there, I don't know that that's a huge problem either.

If we want to build an orbital habitat, it would probably make sense to use lunar materials for construction, since it's much easier to get that out of the gravity well than it is to lift it from earth. A colony and mining operation would be a good start for that project.

Asteroids are an attractive alternative, but A) they don't come with significant gravity, B) I don't know how the cost of shifting them into a suitable orbit would be C) I'm concerned about the possibility of an accident or sabotage resulting in an extinction event for Earth. Plus, D) they're really kind of a crapshoot, while we can do a lot of preliminary exploration of Luna to find suitable resources much more cheaply and easily.

* I have no idea what % of needed materials would actually be found on Luna. But I'm betting it's really high, if we work on the idea of using lunar rock as construction materials and mining metals and making glass to form more critical components.

A lunar colony has one massive 'if', and that is whether long term survival at lunar gravity is feasible. A centrefuge buried on the moon could be possible, but would require massive excavations, and would be considerably complicated by the existing lunar gravity. I suppose everyone could carry around a quarter ton with them at all times, so it is not insurmountable, but it could significantly complicate life.

It also has power complications that orbital colonies do not have. Solar panels are very effective and very consistent in free space (with some consideration of position) where they can maintain perfect orientation and are never in shadow. On the moon they would get less than a third of the sunlight and for 15 days at a time they would produce no power at all. You run into some of the same difficulties that renewables have on earth in terms or duty cycles and storage, only because of the longer 'day' the storage becomes much more problematic.

Most elements would be available on the moon, but nitrogen is almost entirely absent. Nitrogen would require transfer of material from much further afield anyway, and you will generally be able to find higher grade ore for most things on asteroids. If shielding is a major concern, there is the possibility of keeping the living sections of the colony in the shadow of a large asteroid. Robotic prospectors would not be particularly expensive if they are being manufactured in space.

Mostly I think that a colony will exist for some reason, such as manufacturing, and then the habitation will be a secondary concern. The power considerations alone make staying in space far more tempting for manufacturers.

[factotum]

Apparently some people in NASA want to dump the ISS, I don't like that idea, it has a motor (it would have crashed to Earth before now without), it should be moved to wherever a spacestation is wanted, it'd be slow

Firstly, the ISS does not have a motor. They use the engines of the supply rockets to boost its orbit when that's required. Secondly, the thing masses more than four hundred tonnes--moving it *anywhere* other than LEO would require huge amounts of fuel. (To give you a comparison, the dry mass of the entire Saturn V stack that put men on the Moon was around half the ISS--the other 2,800-odd tonnes was all fuel required to get a relatively small payload to lunar orbit, and an even smaller one back to Earth).

[LibraryOgre]

I think that, as we start to move further out into the solar system, we're likely to establish semi-permanent stations at L1 and L2, and eventually L3, L4, and L5.

[gomipile]

Firstly, the ISS does not have a motor. They use the engines of the supply rockets to boost its orbit when that's required. Secondly, the thing masses more than four hundred tonnes--moving it *anywhere* other than LEO would require huge amounts of fuel.

With a close to 50km/s exhaust velocity, the newer ion engines could get the ISS to pretty much anywhere in the Earth-Moon system with less than 3 Falcon Heavy loads full of xenon. (The delta-v calculations say just 1 Falcon Heavy's worth, but I'm being pessimistic on the dry mass of tanks, valves, etc.)

I wouldn't want to use the current ISS at L5, etc., but getting it to a stable orbit just a bit further above the outer atmosphere would be considerably easier.

[factotum]

With a close to 50km/s exhaust velocity, the newer ion engines could get the ISS to pretty much anywhere in the Earth-Moon system with less than 3 Falcon Heavy loads full of xenon.

And how many years would it take to perform such a manoeuvre when you have at most a couple of newtons of thrust and 420 tonnes to push with it? For that matter, would that little thrust even be able to overcome the atmospheric drag at the altitude the ISS orbits at?

[ace rooster]

And how many years would it take to perform such a manoeuvre when you have at most a couple of newtons of thrust and 420 tonnes to push with it? For that matter, would that little thrust even be able to overcome the atmospheric drag at the altitude the ISS orbits at?

By my numbers 10N of force will produce a delta v of 2km/s on 500 tons in about 3 years. It's the old pushing against a ship from the pier trick. Not fast, but not so slow as to be unfeasible.

My quick google did not find any solid numbers for the drag on the space station, but I did find one piece that said that reboosts happend roughly monthly, and another that gave the delta v for a reboost at just over 2m/s, so I think the drag amounts to less than one newton.

[AgentPaper]

By my numbers 10N of force will produce a delta v of 2km/s on 500 tons in about 3 years. It's the old pushing against a ship from the pier trick. Not fast, but not so slow as to be unfeasible.

My quick google did not find any solid numbers for the drag on the space station, but I did find one piece that said that reboosts happend roughly monthly, and another that gave the delta v for a reboost at just over 2m/s, so I think the drag amounts to less than one newton.

You can't thrust 100% of the time, though, with a burn that slow. The further away you are from periapsis (the lowest point in your orbit), the less efficient you are, thus the more fuel you need to burn. In reality you could burn for maybe 10% of the time, and less and less as your orbit becomes more elliptical and you spend more time slowly dropping back down to periapsis. I'm not about to do the numbers but this would turn 3 years into 30+ at least, probably much more.

And of course, during those many years you would need to be maintaining the various electronics and repairing damaged parts, so you need a crew which needs to be replaced from time to time which gets more and more expensive and difficult as your obit becomes larger.

No, moving the ISS to even high orbit like this is not really practical. Moving it to the moon or even further is basically impossible. You would need much more powerful engines, which means more weight, more fuel, more launches, more money, and less time spent doing actually useful things like going to Mars.

[halfeye]

You can't thrust 100% of the time, though, with a burn that slow. The further away you are from periapsis (the lowest point in your orbit), the less efficient you are, thus the more fuel you need to burn. In reality you could burn for maybe 10% of the time, and less and less as your orbit becomes more elliptical and you spend more time slowly dropping back down to periapsis. I'm not about to do the numbers but this would turn 3 years into 30+ at least, probably much more.

And of course, during those many years you would need to be maintaining the various electronics and repairing damaged parts, so you need a crew which needs to be replaced from time to time which gets more and more expensive and difficult as your obit becomes larger.

No, moving the ISS to even high orbit like this is not really practical. Moving it to the moon or even further is basically impossible. You would need much more powerful engines, which means more weight, more fuel, more launches, more money, and less time spent doing actually useful things

A light sail would probably do it.


like going to Mars.

Lol: :smallbiggrin:

Mars is dead, cold and probably always will be. Venus could be cooled, but heating Mars and making it big enough to hold an atmosphere are two independent very long term (thousand year?) projects.

[AgentPaper]

A light sail would probably do it.

That...wouldn't work for a truly massive number of reasons.


Lol: :smallbiggrin:

Mars is dead, cold and probably always will be. Venus could be cooled, but heating Mars and making it big enough to hold an atmosphere are two independent very long term (thousand year?) projects.

Ok, in order:

1) I didn't say that we should colonize Mars, just go there. Which is very much possible and would be very useful, not just from what we discover by being there but what we figure out and build in order to get there.

2) "Cooling" Venus would be a task of staggering proportions. Much more difficult than terraforming Mars.

3) Terraforming Mars would take a long time, hundreds or even thousands of years sure, but it is possible and doesn't involve making it "bigger". It can already hold an atmosphere almost as well as Earth can, it's just that "almost as well" means it lost it a few billion years before Earth is going to. If we pump more gas into the air there (there's plenty of material on Mars to do so), it will slowly bleed off, but on the scale of billions of years.

4) We don't need to terraform Mars to colonize it. We can build structures that we can live in, grow food in, and we can do useful stuff like mine and manufacture and whatever else the Mars colonists decide they want to do.

[ace rooster]

You can't thrust 100% of the time, though, with a burn that slow. The further away you are from periapsis (the lowest point in your orbit), the less efficient you are, thus the more fuel you need to burn. In reality you could burn for maybe 10% of the time, and less and less as your orbit becomes more elliptical and you spend more time slowly dropping back down to periapsis. I'm not about to do the numbers but this would turn 3 years into 30+ at least, probably much more.

Well if you are only going to use your engines 10% of the time things are obviously going to take longer. You are applying a flight profile that is appropriate for rockets with low specific impulse, which are very powerful, so that the limiting factor is fuel. In this case it makes sense to use the profile that uses absolute minimal fuel, with a saving of 20% being huge. Ion rockets have very different limitations. A constant energy increasing burn would be less efficient, (not sure of the numbers, but I would be surprised if it is more than 30%) but given that the limiting factor is power, this is the constraint we need to be concerned about.


And of course, during those many years you would need to be maintaining the various electronics and repairing damaged parts, so you need a crew which needs to be replaced from time to time which gets more and more expensive and difficult as your obit becomes larger.

No, moving the ISS to even high orbit like this is not really practical. Moving it to the moon or even further is basically impossible. You would need much more powerful engines, which means more weight, more fuel, more launches, more money, and less time spent doing actually useful things like going to Mars.
It is not worth doing; it is in the orbit it is in for good reasons, but it is far from impossible.

[factotum]

4) We don't need to terraform Mars to colonize it. We can build structures that we can live in, grow food in, and we can do useful stuff like mine and manufacture and whatever else the Mars colonists decide they want to do.

Probably the best thing to do if we wanted to colonise Mars would be to have the colonies underground--you get a nice rock shield protecting you against asteroids and other stuff the thin Martian atmosphere won't stop, and digging out a large cave would be considerably easier than building a large, airtight above-ground structure.

[halfeye]

Probably the best thing to do if we wanted to colonise Mars would be to have the colonies underground--you get a nice rock shield protecting you against asteroids and other stuff the thin Martian atmosphere won't stop, and digging out a large cave would be considerably easier than building a large, airtight above-ground structure.
That applies equally to the Moon.


That...wouldn't work for a truly massive number of reasons.

Name one.


Ok, in order:

1) I didn't say that we should colonize Mars, just go there.

Land and return, like Apollo did with the Moon? I don't think that would be useful.


Which is very much possible and would be very useful, not just from what we discover by being there but what we figure out and build in order to get there.

If we do anything, we get those benefits from trying. The Moon is easier, we've been there already and we know we can get off it again, Mars has enough atmosphere and gravity to make getting up again much more difficult than it would be from the Moon, but not the right sort of either to make living there permanently possible.


2) "Cooling" Venus would be a task of staggering proportions. Much more difficult than terraforming Mars.

Considering that terraforming Mars would entail quadrupling its mass, and terraforming Venus wouldn't require changing its mass at all, you're simply mistaken about that.


3) Terraforming Mars would take a long time, hundreds or even thousands of years sure, but it is possible and doesn't involve making it "bigger". It can already hold an atmosphere almost as well as Earth can, it's just that "almost as well" means it lost it a few billion years before Earth is going to. If we pump more gas into the air there (there's plenty of material on Mars to do so), it will slowly bleed off, but on the scale of billions of years.

You are guessing. I'm guessing that the time span for Mars to lose an Earth type atmosphere, due to its low gravity would be tens of years, hundreds at best.


4) We don't need to terraform Mars to colonize it. We can build structures that we can live in, grow food in, and we can do useful stuff like mine and manufacture and whatever else the Mars colonists decide they want to do.

Sure we could. We could do all of that on the Moon, easier, cheaper, with some chance of getting help there in time in an emergency.

[georgie_leech]

Considering that terraforming Mars would entail quadrupling its mass, and terraforming Venus wouldn't require changing its mass at all, you're simply mistaken about that.

What makes you think that terraforming requires the planet to be the same size? :smallconfused:

[halfeye]

What makes you think that terraforming requires the planet to be the same size? :smallconfused:
Terraform == Earth-form, like Earth. One of Earth's major features is its mass and gravity.

[Grey_Wolf_c]

Terraform == Earth-form, like Earth. One of Earth's major features is its mass and gravity.

Speaking as someone that agrees with you that it would probably be easier to establish a colony in Venus than in Mars, I nevertheless have to say: you are literally the first person I have ever seen using such reductionist definition of terraforming.

"Terraforming (literally, "Earth-shaping") of a planet, moon, or other body is the hypothetical process of deliberately modifying its atmosphere, temperature, surface topography or ecology to be similar to the environment of Earth to make it habitable by Earth-like life." (from wikipedia; other dictionaries easily reachable through google agree)

Nothing in that definition requires increasing gravity to 1g, only make the planet habitable. Mars' 0.4g is already habitable. The toxic dust, freezing temperatures, no breathable air, lack of magnetosphere, etc are not, and therefore terraforming Mars would have to concentrate on those, not on modifying its mass.

Grey Wolf

[Emperordaniel]

Terraform == Earth-form, like Earth. One of Earth's major features is its mass and gravity.

In the looser definition, "terraform" could be taken to mean making it habitable enough for humans that they don't need to put on an EVA suit every time they want to go outside. :smalltongue:

And I'm pretty sure Mars doesn't lose atmosphere that fast. Faster than Earth, yes, but not so fast that it would be uninhabitable again within a century of being given an Earth-like atmosphere.

[AgentPaper]

Name one.

A solar sail only produces thrust in one direction: away from the sun. If you opened one up in orbit, you'd end up going nowhere because your thrust would cancel out over the course of each trip around the earth. You would need to open it on one side, then close it before you came around to the other side, and do that again and again every time you orbit around the earth. Deploying a solar sail at all is already a fairly difficult challenge, getting one that can deploy and re-pack itself every hour and a half for years is non-trivial, to say the least. Especially since to get the ISS anywhere in any reasonable amount of time, it's going to need to be big.


Land and return, like Apollo did with the Moon? I don't think that would be useful.

Many people disagree. There is a lot of science that we can't do without having people there.

Also, it wouldn't quite be a simple land and return. Due to how orbital mechanics work, they would be there for at least half a year while they wait for Mars and the Earth to line up again for their return trip. An example of how it could work is Mars Direct (https://en.wikipedia.org/wiki/Mars_Direct).


If we do anything, we get those benefits from trying. The Moon is easier, we've been there already and we know we can get off it again, Mars has enough atmosphere and gravity to make getting up again much more difficult than it would be from the Moon, but not the right sort of either to make living there permanently possible.

We might learn by building a base on the Moon, but a simple land and return wouldn't teach us much. We've already done that, many times.


Considering that terraforming Mars would entail quadrupling its mass, and terraforming Venus wouldn't require changing its mass at all, you're simply mistaken about that.

You are guessing. I'm guessing that the time span for Mars to lose an Earth type atmosphere, due to its low gravity would be tens of years, hundreds at best.

I don't have to guess. Plenty of people have done the analysis for Mars (https://en.wikipedia.org/wiki/Terraforming_of_Mars) and Venus (https://en.wikipedia.org/wiki/Terraforming_of_Venus), and as it turns out, it may be much easier to terraform Mars than it might seem. There's already plenty of material there to make an atmosphere, it's just too cold so it's all frozen. And we have a lot of experience and expertise when it comes to warming up planets. All you'd need to do is set up a few factories to churn out the most powerful greenhouse gasses we know about, and you could get Mars warm enough to melt the ice within a few thousand years, easily. Much less, if you're willing to ramp up production enough.


Sure we could. We could do all of that on the Moon, easier, cheaper, with some chance of getting help there in time in an emergency.

Easier to get there, perhaps, but not easier to stay there. Aside from the problems of dust (which are much worse on the Moon compared to Mars), there's also the problem of raw materials. Mars' atmosphere may be thin, but it's there, and it has lots of ice water as well, which you can drill for if you land in the right spot. With some fairly simple chemical processes, you can transform the nitrogen and carbon dioxide in the air and the frozen water into oxygen, methane for fuel (makes it easier to get back since you don't need to bring all your fuel with you), and even fertilizer for growing plants.

[halfeye]

And I'm pretty sure Mars doesn't lose atmosphere that fast. Faster than Earth, yes, but not so fast that it would be uninhabitable again within a century of being given an Earth-like atmosphere.
Pretty sure is not really enough.

At exactly 20 degrees centigrade, the speed of an oxygen molecule is above escape velocity for Mars. Temperature is an average, so what that means is over half the oxygen molecules are above escape velocity. That's a recipe for disaster. How often do we dump more oxygen in, where do we find it, how do we avoid hitting our stuff with the lumps when they land?


A solar sail only produces thrust in one direction: away from the sun. If you opened one up in orbit, you'd end up going nowhere because your thrust would cancel out over the course of each trip around the earth. You would need to open it on one side, then close it before you came around to the other side, and do that again and again every time you orbit around the earth. Deploying a solar sail at all is already a fairly difficult challenge, getting one that can deploy and re-pack itself every hour and a half for years is non-trivial, to say the least. Especially since to get the ISS anywhere in any reasonable amount of time, it's going to need to be big.
There's a technique called tacking. It means you get lift in a direction other than directly away from the sun. Yeah, it's not entirely simple, but it can almost certainly be done.




Many people disagree. There is a lot of science that we can't do without having people there.

Also, it wouldn't quite be a simple land and return. Due to how orbital mechanics work, they would be there for at least half a year while they wait for Mars and the Earth to line up again for their return trip.

Earth year? Mars year? That's a lot of canned water, air and veggies.


We might learn by building a base on the Moon, but a simple land and return wouldn't teach us much. We've already done that, many times.
Yeah, we need a base on the moon.

[AgentPaper]

Pretty sure is not really enough.

At exactly 20 degrees centigrade, the speed of an oxygen molecule is above escape velocity for Mars. Temperature is an average, so what that means is over half the oxygen molecules are above escape velocity. That's a recipe for disaster. How often do we dump more oxygen in, where do we find it, how do we avoid hitting our stuff with the lumps when they land?

That's called Jeans escape (https://en.wikipedia.org/wiki/Atmospheric_escape#Thermal_escape_mechanisms), but it doesn't mean that half of the atmosphere is going to blow off right away. Your particle also needs to be in the right spot, and 20C at surface level doesn't mean 20C at high atmosphere. Some will get out regardless, and they do even on earth, but it is a slow process even with a relatively small planet like Mars.


There's a technique called tacking. It means you get lift in a direction other than directly away from the sun. Yeah, it's not entirely simple, but it can almost certainly be done.

Solar sails are not wind sails. They're more like big parachutes.


Earth year? Mars year? That's a lot of canned water, air and veggies.

I remembered wrong, it's about 18 months before they make the return. You do have to pack food along, but air can be recycled, as can water. You could also create more water and oxygen if need be (mars has all the resources you need to do so), but for the relatively short duration of the stay, that probably isn't necessary. Various plans have also called for the growing of more food on Mars, though I think most serious plans call for that more as an experiment, at least for the first few missions, rather than as something to rely on for survival.

I think you really need to take a moment to actually look this stuff up before making all these assertions. Even just a cursory read through the wikipedia pages on most of the stuff you've been saying proves you wrong very quickly.

[weaseldust]

At exactly 20 degrees centigrade, the speed of an oxygen molecule is above escape velocity for Mars. Temperature is an average, so what that means is over half the oxygen molecules are above escape velocity. That's a recipe for disaster.

It's not as bad as it sounds because half the molecules will have a velocity pointing towards the ground and, more importantly, almost all of the molecules will have a lot of other molecules in the way. For instance, if you stripped off the Earth's atmosphere and then released an oxygen molecule at the Earth's surface with the average velocity it would have at 300K, it should end up with an altitude over 1000km, but we can observe that very few molecules on Earth actually make it to that height because of the rest of the atmosphere getting in the way.

[factotum]

Pretty sure is not really enough.

There is evidence that there was once running water on Mars--evidence that it ran for long enough to carve out canyons and the like. That simply couldn't have happened if whatever atmosphere Mars had four billion years ago blew away in a century, like you're proposing. Also, as already pointed out, even if 20C is the temperature at ground level, it isn't likely to be that at altitude. As an example, the temperature above Venus' cloud tops is actually below freezing, because temperature of a planet is partly down to its albedo (reflectiveness) and the clouds reflect a great a deal of the sun's heat back out into space. It's unlikely the temperature gradient would be quite so extreme on a terraformed Mars, but it's going to be there. Plus the planet is further from the Sun than we are and thus the atmosphere-stripping effect of the solar wind will be much less.

[halfeye]

Even just a cursory read through the wikipedia pages on most of the stuff you've been saying proves you wrong very quickly.
Wikipedia is not reliable. I like it and use it, but it's a first look, not definitive.

[halfeye]

It's not as bad as it sounds because half the molecules will have a velocity pointing towards the ground and, more importantly, almost all of the molecules will have a lot of other molecules in the way. For instance, if you stripped off the Earth's atmosphere and then released an oxygen molecule at the Earth's surface with the average velocity it would have at 300K, it should end up with an altitude over 1000km, but we can observe that very few molecules on Earth actually make it to that height because of the rest of the atmosphere getting in the way.

That's why I don't say it will immediately go, but give it tens or hundreds of years. CO2 is heavy, and will push the O2 above itself. The atmosphere of Earth does not get steadily cooler as you head upwards, near and in space there's very little gas indeed, but what there is is very hot.


There is evidence that there was once running water on Mars--evidence that it ran for long enough to carve out canyons and the like. That simply couldn't have happened if whatever atmosphere Mars had four billion years ago blew away in a century, like you're proposing. Also, as already pointed out, even if 20C is the temperature at ground level, it isn't likely to be that at altitude. As an example, the temperature above Venus' cloud tops is actually below freezing, because temperature of a planet is partly down to its albedo (reflectiveness) and the clouds reflect a great a deal of the sun's heat back out into space. It's unlikely the temperature gradient would be quite so extreme on a terraformed Mars, but it's going to be there. Plus the planet is further from the Sun than we are and thus the atmosphere-stripping effect of the solar wind will be much less.
There is some evidence that there is still water on Mars in very strong salt solutions that run when they are warmed sufficiently. That might be what made those canyons, or maybe it was liquid Methane or something (I am not a chemist, so I don't know what oil type stuff would work for that).


Speaking as someone that agrees with you that it would probably be easier to establish a colony in Venus than in Mars, I nevertheless have to say: you are literally the first person I have ever seen using such reductionist definition of terraforming.

I was probably over-simplifying.


"Terraforming (literally, "Earth-shaping") of a planet, moon, or other body is the hypothetical process of deliberately modifying its atmosphere, temperature, surface topography or ecology to be similar to the environment of Earth to make it habitable by Earth-like life." (from wikipedia; other dictionaries easily reachable through google agree)

Nothing in that definition requires increasing gravity to 1g, only make the planet habitable. Mars' 0.4g is already habitable. The toxic dust, freezing temperatures, no breathable air, lack of magnetosphere, etc are not, and therefore terraforming Mars would have to concentrate on those, not on modifying its mass.

Grey Wolf

Continuously losing the oxygen and water from the atmosphere would be a problem, so long as it is unstable and needs constant/continual refreshing, it's not terraformed to my way of thinking.

[georgie_leech]

Continuously losing the oxygen and water from the atmosphere would be a problem, so long as it is unstable and needs constant/continual refreshing, it's not terraformed to my way of thinking.

Earth loses water and oxygen from the atmosphere over time. The question isn't whether it happens, it's how long it takes for a significant amount to be lost.

[halfeye]

Earth loses water and oxygen from the atmosphere over time. The question isn't whether it happens, it's how long it takes for a significant amount to be lost.

Yeah, but in net is there really a loss on Earth? There's some lost but there's some gained (from meteors and the tails of comets), is there really an ongoing loss that will become critical before the sun goes bye-bye?

[Dodom]

I've read (Science&Vie, one of 2013's editions) that Earth's atmosphere should be able to accommodate life for another 100 million years, because carbon dioxide is gradually absorbed into limestone, forming calcium carbonate. 100 million years is the estimate of when carbon dioxide pressure won't be enough to feed plants. So, what gases are lost in spaces are not as significant as the ones being chemically captured by the planet itself.
I imagine the same issue could happen on Mars, but worse: there hasn't been a significant gas pressure on it for a long time, are there metals waiting to oxidise and lime hungering for CO2?

Another question: if one had the resources to import or produce the million tons of air needed to give Mars an atosphere, what would the ground level pressure be? The lower gravity would require a much taller column of air to reach the same pressure, would that require an atmosphere that reaches further than gravity can retain it?

[weaseldust]

That's why I don't say it will immediately go, but give it tens or hundreds of years. CO2 is heavy, and will push the O2 above itself. The atmosphere of Earth does not get steadily cooler as you head upwards, near and in space there's very little gas indeed, but what there is is very hot.

I'm not sure where the comment about temperature at high altitudes comes from, because I didn't say anything about it. Also, the CO2 will not push the O2 anywhere for the same reason that it doesn't on Earth - gases diffuse into one another fairly quickly. (I'm talking about timescales longer than a few minutes. In the very short term, CO2 can form a blanket against the ground that keeps out oxygen, but it quickly diffuses away. The distribution of gases in the Earth's atmosphere is pretty uniform.)

Having checked, it's not even true that the average speed of an O2 molecule in an Earth-like atmosphere is greater than Mars' escape velocity. It's about 10 times smaller. (The average KE is about 6.3x10^-21 J. The mass is about 5.3x10^-26 kg. That gives a speed just under 500m/s.) I looked about and this link (http://astro.physics.uiowa.edu/~srs/2952_10/Lec24.pdf) (PDF) claims that Mars shouldn't suffer from thermal losses any greater than Titan.

[Tvtyrant]

The thing about the moon is it has millions of times more space than we do on Earth, because it has no water table or internal heat to prevent miles deep shafts from being built. Depending on the effects of its gravity on humans, we may find that hydroponic farming colonies buried in the depths of the moon are our best option, especially as it prevents cosmic rays.

[factotum]

Another question: if one had the resources to import or produce the million tons of air needed to give Mars an atosphere, what would the ground level pressure be? The lower gravity would require a much taller column of air to reach the same pressure, would that require an atmosphere that reaches further than gravity can retain it?

Make the atmosphere composition different and this is not an issue. Venus's atmosphere doesn't extend any further out than Earth's does, and the planet's gravity is slightly lower than ours, but that doesn't prevent Venus having a surface pressure of 90 atmospheres--because its atmosphere consists mostly of denser gases like carbon dioxide. (Obviously you wouldn't want to use carbon dioxide on a terraformed Mars because having too high a concentration of that causes major problems in humans, up to and including death, but I'm sure there are plenty of dense biologically inert gasses which could be used).

[halfeye]

I'm not sure where the comment about temperature at high altitudes comes from, because I didn't say anything about it.
I was replying to the thread, if I quoted you in particular then the first part of my comment would have been based on that, but toward the end I would have been talking about generalities.


Also, the CO2 will not push the O2 anywhere for the same reason that it doesn't on Earth - gases diffuse into one another fairly quickly. (I'm talking about timescales longer than a few minutes. In the very short term, CO2 can form a blanket against the ground that keeps out oxygen, but it quickly diffuses away. The distribution of gases in the Earth's atmosphere is pretty uniform.)

It takes a little longer than a few minutes. People have been gased by CO2 outpourings from volcanos and for some reason that I don't quite remember, some lakes.


Having checked, it's not even true that the average speed of an O2 molecule in an Earth-like atmosphere is greater than Mars' escape velocity. It's about 10 times smaller. (The average KE is about 6.3x10^-21 J. The mass is about 5.3x10^-26 kg. That gives a speed just under 500m/s.)

Wikipedia tells me that the escape velocity of Mars is 5.027 km/s versus Earth's escape velocity of 11.186 km/s, I'm not great at googling, I so far haven't found a link for the speed of O2 or water.


I looked about and this link (http://astro.physics.uiowa.edu/~srs/2952_10/Lec24.pdf) (PDF) claims that Mars shouldn't suffer from thermal losses any greater than Titan.
Yeah, that's for CO2 though, which I wouldn't expect to leave.

[georgie_leech]

Yeah, but in net is there really a loss on Earth? There's some lost but there's some gained (from meteors and the tails of comets), is there really an ongoing loss that will become critical before the sun goes bye-bye?

No, but worrying about that time frame is already ludicrous. If an atmosphere is solid for even a thousand years, that's plenty on it's own, as 1000 years was the difference between us figuring out the scientific method was a good idea and us debating on methods for colonising other planets, curing blindness, growing organs, and other things that would have been considered miracles at the time. And for the record, Mars doesn't lose atmosphere at such a rate that it would vanish in a thousand years in the first place, otherwise it wouldn't have what it has now.

[Ravens_cry]

I think the best place for a free space colony would be near an asteroid. If it's the right size, you could even have the station around or even in it. That way, you have an easy source of resources without having to get them trucked in, which always has the danger of being disrupted or delayed. In orbit, I could see stations for refuelling, though I don't know how manned they'd be, since adding manned capability adds a lot of complexity. Still, we're able to set up fuel stations in orbit supplied by lower delta-v sources, or, even better, orbital construction supplied from such sources, it opens up the solar system in a whole new way.

[AgentPaper]

I think the best place for a free space colony would be near an asteroid. If it's the right size, you could even have the station around or even in it. That way, you have an easy source of resources without having to get them trucked in, which always has the danger of being disrupted or delayed. In orbit, I could see stations for refuelling, though I don't know how manned they'd be, since adding manned capability adds a lot of complexity. Still, we're able to set up fuel stations in orbit supplied by lower delta-v sources, or, even better, orbital construction supplied from such sources, it opens up the solar system in a whole new way.

Mining an asteroid by building a base on it is something I expect to see pretty soon*. If it isn't too big (or too small), you could even spin it up to generate some gravity for your base, with the extra benefit of making it easier to get material out of your mines once you break it loose.

*By which I mean, in my lifetime.

[Storm_Of_Snow]

Mining an asteroid by building a base on it is something I expect to see pretty soon*. If it isn't too big (or too small), you could even spin it up to generate some gravity for your base, with the extra benefit of making it easier to get material out of your mines once you break it loose.

*By which I mean, in my lifetime.
All spinning the asteroid would do is give any given spot on it's surface night and day - gravity will be generated by the mass of the asteroid anyway, but will be too low to be useful (Ceres' surface gravity is about 3% that of Earth).

Unless you're expecting everyone to walk on the ceiling of your base, of course. :smallwink:

[AgentPaper]

All spinning the asteroid would do is give any given spot on it's surface night and day - gravity will be generated by the mass of the asteroid anyway, but will be too low to be useful (Ceres' surface gravity is about 3% that of Earth).

Unless you're expecting everyone to walk on the ceiling of your base, of course. :smallwink:

Unless the asteroid is truly massive, the natural gravity won't amount to much. By spin, I meant fast enough that you'd have artificial gravity from the centripetal force. Maybe not enough to get 1g on the surface of the asteroid, but enough to help mined rocks fall out of the asteroid, and then actual 1g on the miner's habitat out on a tether.

[Storm_Of_Snow]

Unless the asteroid is truly massive, the natural gravity won't amount to much.

As I'd already pointed out... :smallwink:



By spin, I meant fast enough that you'd have artificial gravity from the centripetal force. Maybe not enough to get 1g on the surface of the asteroid, but enough to help mined rocks fall out of the asteroid, and then actual 1g on the miner's habitat out on a tether.


Which basically means you'd have to dig down along the axis of rotation into the centre of mass of the asteroid and completely clear it out while maintaining the asteroids centre of mass to give you your pit head, otherwise it'll wobble (possibly so much that you couldn't land on it), and hope that the asteroid is one contiguous body rather than a collection of smaller chunks loosely held together, so that it won't break up when you start to spin it, attach your tether to the surface on a completely different location to where you're digging down, with a big enough anchor dug under the surface (and hope it doesn't pull out), and have some way of adjusting the rotational velocity as you mine out the asteroid so that you maintain your desired force at the pit head, and shipped in all the infrastructure you'd need to get the mined ore and spoil out against the force that you're generating - at least as far as where your tether is dug in, at which point you need to make sure they follow the tether rather than just being shot out at a random angle (which could mean your habitat crashes into it on the next rotation).

By the time you've done all that, you could probably have broken the asteroid up into chunks small enough to be taken on board your mining platform, processed them, shipped everything to where it's going and gone on to the next asteroid, and all for a significant amount less in cost - in fact, most of your miners can probably be remote controlled drones, operated from the mining platform, which would have it's own spin habitat.

The only reason to do anything like that is if you're building a habitat inside the asteroid.

[ace rooster]

Mining an asteroid by building a base on it is something I expect to see pretty soon*. If it isn't too big (or too small), you could even spin it up to generate some gravity for your base, with the extra benefit of making it easier to get material out of your mines once you break it loose.

*By which I mean, in my lifetime.

You might think that having a force outward would make extracting materials easier, but I think this is wrong. Even ignoring the effects that will make objects not travel in 'straight' lines (for some definition of straight), or catastrophic failure modes you introduce, you will still need large forces to control large objects. Simpler is for their to be no 'gravity' at all, meaning that even very large loads can be handled with modest forces.

An analogy is comparing a heavy rail car at the top of a hill to one on a flat track. You could say that the slope helps you get the car to the bottom, but in practice the flat track makes controlling it so much easier that this is preferable.

[AgentPaper]

You might think that having a force outward would make extracting materials easier, but I think this is wrong. Even ignoring the effects that will make objects not travel in 'straight' lines (for some definition of straight), or catastrophic failure modes you introduce, you will still need large forces to control large objects. Simpler is for their to be no 'gravity' at all, meaning that even very large loads can be handled with modest forces.

An analogy is comparing a heavy rail car at the top of a hill to one on a flat track. You could say that the slope helps you get the car to the bottom, but in practice the flat track makes controlling it so much easier that this is preferable.

Yeah, probably true, combined with the point above about it being harder to dock and collect the resources. I guess cooler in my head than in practice, haha.

[factotum]

Even ignoring the effects that will make objects not travel in 'straight' lines (for some definition of straight)

If you drop an object off the edge of a spinning asteroid then it will totally travel in a straight line, so not sure what you mean by this? Unless you're talking about objects that you throw around *inside* the spinning habitat, which would definitely follow some strange paths (cricket or baseball in one of these things would be...interesting, to say the least).

[halfeye]

I think the best place for a free space colony would be near an asteroid. If it's the right size, you could even have the station around or even in it. That way, you have an easy source of resources without having to get them trucked in, which always has the danger of being disrupted or delayed. In orbit, I could see stations for refuelling, though I don't know how manned they'd be, since adding manned capability adds a lot of complexity. Still, we're able to set up fuel stations in orbit supplied by lower delta-v sources, or, even better, orbital construction supplied from such sources, it opens up the solar system in a whole new way.

Ceres being ice will be nice to mine for water, the risk will be pressure building up, but so long as that is vented, you should be able to get nice strong tunnels in it.


If you drop an object off the edge of a spinning asteroid then it will totally travel in a straight line, so not sure what you mean by this? Unless you're talking about objects that you throw around *inside* the spinning habitat, which would definitely follow some strange paths (cricket or baseball in one of these things would be...interesting, to say the least).

No, inside the paths are still straight lines, they just look odd because the asteroid is moving.


No, but worrying about that time frame is already ludicrous. If an atmosphere is solid for even a thousand years, that's plenty on it's own, as 1000 years was the difference between us figuring out the scientific method was a good idea and us debating on methods for colonising other planets, curing blindness, growing organs, and other things that would have been considered miracles at the time.

A thousand years being time till total oxygen or water depletion would mean that habitability for humans would be about 500 years. That's a "people all die" deadline. Colonists sometimes have to start from a "We're back in the stone age with no way of writing stuff down" situation, 500 years from there to spaceflight is a tough ask.


And for the record, Mars doesn't lose atmosphere at such a rate that it would vanish in a thousand years in the first place, otherwise it wouldn't have what it has now.

What it has now is mainly CO2 which is a heavy molecule, that won't get away in billions of years, and it hasn't. It may be that oxygen and water are also heavy enough to stay, in which case it's very curious that they haven't, but CO2 is known to be heavy enough that it can't leave.

[georgie_leech]

A thousand years being time till total oxygen or water depletion would mean that habitability for humans would be about 500 years. That's a "people all die" deadline. Colonists sometimes have to start from a "We're back in the stone age with no way of writing stuff down" situation, 500 years from there to spaceflight is a tough ask.

That's... no, that isn't how colonization works. They don't suddenly lose all technology when they move to Mars, and even in the event of some weird disaster frying their computers or something, they're not on the other side of the galaxy, they're within shipping distance of earth. In no situation is a time limit ever placed on them that the atmosphere is relevant for.


What it has now is mainly CO2 which is a heavy molecule, that won't get away in billions of years, and it hasn't. It may be that oxygen and water are also heavy enough to stay, in which case it's very curious that they haven't, but CO2 is known to be heavy enough that it can't leave.

O2 in particular is also somewhat heavy, at about 32g/Mol compared to carbon dioxide at about 44g/Mol. That is not enough of a difference to account for a rapid loss of all oxygen when we have direct evidence (it's still there!) of the carbon dioxide lingering for billions of years. The timescale for atmospheres being stripped of appreciable amounts of gasses is in the millions of years. How long do you think it takes?

[Tev]

Orbital colonies is neat idea, tourism alone will make them real much sooner than large Mars/Moon colonies. Cooling them down is problematic though.

Mars' surface is pretty neat for colonies, but pretty useless for anything else. And it's quite far (esp. in terms of time, but also delta-v), and while much better than almost all other places outside Earth, it's still much worse than Earth. Colonization will happen, but s-l-o-w-l-y.

Moon is worthless as a colony, manufacturing or research outpost, or any other permanent kind of thing. The more you know about space the more you wonder why does the moon-first crowd imagine it's a good destination.
But it IS very close (at least as time goes, delta-v proximity isn't great), nobody will care about anything you do there (planetary protection will slow down (especially Mars) colonization a lot), and when space economy gets going it might be (after massive investments) best source of material.

Killer app for orbital colonies is human reproduction and growth - if it turns out you need close to 1g for children Mars is out. If it turns out 0.4g is enough Mars might win big time . . .

Best thing is, we live in an age where all of this is close to becoming reality - there's little doubt that we will have something somewhere before year 2100.

Btw terraforming Mars needs quadrupling its mass? Oh man, that's a good one :D

[halfeye]

That's... no, that isn't how colonization works. They don't suddenly lose all technology when they move to Mars, and even in the event of some weird disaster frying their computers or something, they're not on the other side of the galaxy, they're within shipping distance of earth. In no situation is a time limit ever placed on them that the atmosphere is relevant for.

You don't read much science fiction then. I don't say it's what will necessarily happen, but it's a worst case that ought to be at the very least thought about.


O2 in particular is also somewhat heavy, at about 32g/Mol compared to carbon dioxide at about 44g/Mol. That is not enough of a difference to account for a rapid loss of all oxygen when we have direct evidence (it's still there!) of the carbon dioxide lingering for billions of years. The timescale for atmospheres being stripped of appreciable amounts of gasses is in the millions of years. How long do you think it takes?

I don't know, I'm being told that the speed of O2 at 20 degrees centigrade is below Mars' escape velocity. In which case, where did it all go? I'm not seeing any speed for O2 or water being given on the web, which may be down to my search skills. If the speed of water and O2 is above the escape velocity of Mars, I'd expect them to go fairly quickly.

[Tev]

I'm being told that the speed of O2 at 20 degrees centigrade is below Mars' escape velocity. In which case, where did it all go?

(Missing magnetosphere + lower mass) * geologic timescales.

I agree that terraforming Mars is insanely difficult (better colonize Moon lol), but it's quite doable if you're willing to wait thousand or two years.

[halfeye]

Orbital colonies is neat idea, tourism alone will make them real much sooner than large Mars/Moon colonies. Cooling them down is problematic though.

I didn't hear cooling the ISS was an issue. I like the idea, ish, but LEO is too low.


Mars' surface is pretty neat for colonies, but pretty useless for anything else. And it's quite far (esp. in terms of time, but also delta-v), and while much better than almost all other place outside Earth, it's still much worse than Earth. Colonization will happen, but s-l-o-w-l-y.

Slowly enough for safety is probably not at all for a long while.


Moon is worthless as a colony, manufacturing or research outpost, or any other permanent kind of thing. The more you know about space the more you wonder why does the moon-first crowd imagine it's a good destination.
But it IS very close (at least as time goes, delta-v proximity isn't great), nobody will care about anything you do there (planetary protection will slow down (especially Mars) colonization a lot), and when space economy gets going it might be (after massive investments) best source of material.

The moon is a stepping stone. The far end of the easiest bridge. A hallfway house. It is probably a good base for telescopes. Mainly though, it's a lot easier to get to other places from there than from Earth.


Killer app for orbital colonies is human reproduction and growth - if it turns out you need close to 1g for children Mars is out. If it turns out 0.4g is enough Mars might win big time . . .

Reproduction is the important thing. Mars isn't close enough for that to matter if a colony can't be completely self sufficient.


Best thing is, we live in an age where all of this is close to becoming reality - there's little doubt that we will have something somewhere before year 2100.

In 1969 we thought that about 2000, it didn't happen, it still isn't happening, that's 45 years, there's less than twice that time to 2100, so good luck with that, you'll need it.


Btw terraforming Mars needs quadrupling its mass? Oh man, that's a good one :D

That was mainly based on the gravity not being enough to hold oxygen and water. If that's not the case, then it changes, but I still think Venus at 82% earthmass is better than Mars at 11%.

[Emperordaniel]

I don't know, I'm being told that the speed of O2 at 20 degrees centigrade is below Mars' escape velocity. In which case, where did it all go? I'm not seeing any speed for O2 or water being given on the web, which may be down to my search skills. If the speed of water and O2 is above the escape velocity of Mars, I'd expect them to go fairly quickly.

If I understand correctly, in order to have a significant O2 presence for any extended time period, you require an active biosphere - plants in particular. If any hypothetical life on Mars never developed to the point where the planet could turn "green", even for a little while, it's quite possible that any O2 Mars has had has long since joined the oxides which make up most of the planet's surface and atmosphere.

[Sith_Happens]

I don't know, I'm being told that the speed of O2 at 20 degrees centigrade is below Mars' escape velocity. In which case, where did it all go?

Into compounds in the soil, hence why the planet's red.

[Flickerdart]

The moon is a stepping stone. The far end of the easiest bridge. A hallfway house. It is probably a good base for telescopes. Mainly though, it's a lot easier to get to other places from there than from Earth.
It's much harder to get to anywhere from the moon than from Earth orbit, or moon orbit. Falling into a gravity well for no good reason does nobody any favours.

[Spojaz]

The moon is a stepping stone. The far end of the easiest bridge. A hallfway house. It is probably a good base for telescopes. Mainly though, it's a lot easier to get to other places from there than from Earth.

The moon is much worse than space for telescopes for several reasons of rotation, thermal distortion and having to do a lunar landing for maintenance. The biggest hurdle to telescopes on the moon however, is the electrically levitating dust "exosphere" that can distort or block images and even etch the glass of the lenses. Moon dust is the worst. During Apollo 11, the moon dust ate through the seals of the sample boxes before the samples got back to earth.

The far shore is made of flying, poisonous nano-particles, but the bridge is pretty nice. We should stay on the bridge.

[Tev]

I didn't hear cooling the ISS was an issue.
It's already major engineering issue, and ISS is designed for what, 9 people? Now imagine 100 people colony . . . or 10 000. Nuclear reactors are hard and heavy in orbit, because of immense mass of radiators. Industrial processes usually produce quite a bit of waste heat . . . square cube law is painful when you can only radiate heat away.
It's not a showstopper, but it sure makes Mars look so much better.


Slowly enough for safety is probably not at all for a long while.
Quite possible. But I think Musk is crazy & capable enough. We shall see.


The moon is a stepping stone. The far end of the easiest bridge. A hallfway house.
Stepping stone to where? It's too unique so tech developed there won't help you much. Maybe for perfecting life support systems, but you can do it in LEO tourist outposts so much more easily . . . and landing/departure delta-v is nontrivial.


Reproduction is the important thing. Mars isn't close enough for that to matter if a colony can't be completely self sufficient.
You don't need completely self sufficient colonies . . . and actually Mars is in ok distance for already reproducing colony. Initial setup is hampered the most by delta-t.


In 1969 we thought that about 2000, it didn't happen, it still isn't happening, that's 45 years, there's less than twice that time to 2100, so good luck with that, you'll need it.
Now that's pointless pessimism.


That was mainly based on the gravity not being enough to hold oxygen and water. If that's not the case, then it changes, but I still think Venus at 82% earthmass is better than Mars at 11%.
Venus' clouds are very interesting place. Harvesting material will be hard, it's quite far and it's questionable how much can you safely scale cloud cities . . . but yeah I think it's the wildcard in the new space colony (snail) race. Venus needs its Musk.

[georgie_leech]

You don't read much science fiction then. I don't say it's what will necessarily happen, but it's a worst case that ought to be at the very least thought about.

Science fiction wherein Interstellar distances need to be taken into account, not the distance to Mars. If some terrible thing happened that caused martian colony tech to fail, they don't have a time limit of 500 years or whatever to get back to space travel tech levels, they just have to wait a few years at most where Earth sends more ships out to help fix things. And that's at current space travel tech levels, mind you. If we're positing technology sufficient to make terraforming possible (for however long), then it makes no sense for Earth to go "Oh what a shame, they had a good run, best of luck to them re-developing space travel" in the event of disaster.

[factotum]

That was mainly based on the gravity not being enough to hold oxygen and water. If that's not the case, then it changes, but I still think Venus at 82% earthmass is better than Mars at 11%.

Don't forget that Mars being smaller actually works to your advantage there--it means its surface gravity is 0.376g, not 0.11g.

[halfeye]

Science fiction wherein Interstellar distances need to be taken into account, not the distance to Mars.

There was one short story where people were on Mars, then the people back home blew the old place up. That was written before we knew Mars isn't and wasn't livable out in the open without radical terraforming.


If some terrible thing happened that caused martian colony tech to fail, they don't have a time limit of 500 years or whatever to get back to space travel tech levels, they just have to wait a few years at most where Earth sends more ships out to help fix things. And that's at current space travel tech levels, mind you.

One of the points of colonisation is to make a total disaster here survivable by those who aren't here. Anywhere that's dependent on here still being here for survival isn't that backup.


If we're positing technology sufficient to make terraforming possible (for however long), then it makes no sense for Earth to go "Oh what a shame, they had a good run, best of luck to them re-developing space travel" in the event of disaster.

If a politician gets a bee in their bonnet about taxes, you can't bet on space getting money that year if next year might theoretically be soon enough. Skylab crashed in part through lack of funds, it would have been a big asset to the ISS if it had stayed up.

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

[Tev]

d
If a politician gets a bee in their bonnet about taxes, you can't bet on space getting money that year if next year might theoretically be soon enough. Skylab crashed in part through lack of funds, it would have been a big asset to the ISS if it had stayed up.

That's just wrong . . .

1) Obviously big difference between abandoning colony of 10,000-10,000,000 people and crashing empty can in space.

2) Skylab crashed because of delay in shuttle program, whose problems were in big part due to design, driven by crazy requirements. Nasa budget was downsizing from "money is not an issue" to some realistic one. You can't really use "Skylab crashed in part through lack of funds" as a point to prove anything.

3) Keeping Skylab in orbit for thirty years (so it would be "big asset to ISS") would definitely hurt US space program. Space environment is not friendly & LEO orbits aren't particularly great for keeping something there for a long time -> it would have cost a lot of money to keep it up and functional (for 30 years lol), especially as it was first design iteration (btw how would that be of use for ISS?). Look at ISS budget.

Skylab's deorbit was kind of premature, but US space program is imo more frequently hamstrung by too much clinging to the past than the other way around (see SLS).

[HandofShadows]

It's already major engineering issue, and ISS is designed for what, 9 people? Now imagine 100 people colony . . . or 10 000. Nuclear reactors are hard and heavy in orbit, because of immense mass of radiators. Industrial processes usually produce quite a bit of waste heat . . . square cube law is painful when you can only radiate heat away.
It's not a showstopper, but it sure makes Mars look so much better.


Why would you need a nuclear reactor when you have all that free solar power? The efficiency of solar panels as gone up a very large amount in the past few years and all indication are the trend will continue.

[Swordsmith]

I agree that part of the point of self sustaining colonies off the planet is that we might lose the planet.

It's hard for me to imagine, though, a disaster big enough that life on a mars colony continues to be possible and yet they've lost the ability to write things down. Humans are really really good at finding ways to write things down, we've been doing it for thousands of years... and prior to that we were also really really really good at telling stories that our kids could tell their kids.

It's not impossible, but you need to come up with a way to kill or render permanently moronic every adult or even child over the age of... what, 5? For SF or gaming purposes, we can probably come up with dozens of ways to make it happen. But in terms of things to worry about it's pretty low on the list.

[HandofShadows]

Swordsmith did you know that the Greeks lost the ability to read and write at least once? (Linear A/B) Loss of tech, knowledge and even advanced civilization has happened a number of times to humanity. :smallfrown: Just look at what the loss of the Library of Alexandria cost. We would be hundreds of years ahead of where we are now if it had survived.

[Storm_Of_Snow]

Why would you need a nuclear reactor when you have all that free solar power? The efficiency of solar panels as gone up a very large amount in the past few years and all indication are the trend will continue.

If you only stay at roughly the same distance from the sun as Earth is, solar's probably all you need. If you want to go further out, sooner or later you'll get to the point where solar panels can't supply enough power and you will need something else.

[RCgothic]

Solar panel area requirement vs habitable volume is a square cube relation. It's probably not feasible to power a very large orbital colony on solar power alone.

Nuclear reactors can at least scale with volume.

But cooling will be a very serious issue. Radiators will probably be the limiting factor. Note that having solar panels does not negate your need for radiators.

It's all about getting some starter industry into orbit so that we can stop hauling things up out of our gravity well. Ideally the only earth-orbit cargo should be humans.

[factotum]

Why would you need a nuclear reactor when you have all that free solar power? The efficiency of solar panels as gone up a very large amount in the past few years and all indication are the trend will continue.

You still need a huge amount of solar panels to generate enough power for a lot of people. For instance, the vast solar panels on the ISS produce a total power output of about 130kW of power, but a proper space colony with, say, a thousand residents would need orders of magnitude more power than that.

[DigoDragon]

I don't see large-scale orbital colonies catching on. You have to keep sending supplies and space inside one is a premium. I see them more befitting the role of a gas station between planetary bases.

A base on the moon and Mars is easier to make self-sustaining because you have some of the building materials right there. The water can be extracted for drinking, converting into breathable air, fuel, and mixing with pulverized rock to make cement for building the base. Digging caverns under the surface for the base gives it a natural defense against solar radiation, helps with insulation against the cold, and can be made large for starting a hydroponic farm. When the technology becomes available, the moon has helium-3 for powering fusion reactors.

[Emperordaniel]

If you only stay at roughly the same distance from the sun as Earth is, solar's probably all you need. If you want to go further out, sooner or later you'll get to the point where solar panels can't supply enough power and you will need something else.People are already looking into using solar panels on probes visiting planets as far away as Uranus (http://www.lpi.usra.edu/opag/march09/presentations/hofstadter.pdf), and we currently have a solar-powered spacecraft - Juno - well on its way to Jupiter, so we are getting to the point where soon, RTGs will mainly be used for places where solar power either cuts out for long periods of time (the lunar surface), can experience sudden, unpredictable interruptions (the Martian surface), or is practically impossible (anywhere on Venus or Titan).


You still need a huge amount of solar panels to generate enough power for a lot of people. For instance, the vast solar panels on the ISS produce a total power output of about 130kW of power, but a proper space colony with, say, a thousand residents would need orders of magnitude more power than that.The ISS solar panels are around 10 years old, space-based solar power tech has come a way since then. You'd still need a lot of solar panels, but not as many as you'd need ten+ years ago.

[HandofShadows]

The ISS solar panels are around 10 years old, space-based solar power tech has come a way since then. You'd still need a lot of solar panels, but not as many as you'd need ten+ years ago.

The tech and design is certainly older than that.

[RCgothic]

I'm still not buying the solar panel power. The theoretical limit for a single layer is around 30%. Efficiency increases with thickness, but this also comes with a mass penalty. I think the theoretical efficiency limit for infinitely many layers is about 86%.

To power a city of 100,000 people takes about 200MW (possibly not including industry). Solar power is 1000W/m. Assuming a wildly optimistic 50% and a high enough orbit for minimal solar interruption, you'd need a 1km x 400m solar array. That's longer than the burj Khalifa and wider than London's Shard. It would be ridiculously fragile, difficult to maintain, and difficult to protect from debris.

Nuclear reactors of almost that capacity have been fitted to submarines. Yes, they're heavy. They'd probably have to be manufactured in space. But they'd be far less maintenance intensive, and the shielding requirements in space are not as difficult.

The ISS cells are about 14% efficient for comparison.

[DigoDragon]

To power a city of 100,000 people takes about 200MW (possibly not including industry). Solar power is 1000W/m. Assuming a wildly optimistic 50% and a high enough orbit for minimal solar interruption, you'd need a 1km x 400m solar array. That's longer than the burj Khalifa and wider than London's Shard. It would be ridiculously fragile, difficult to maintain, and difficult to protect from debris.

Considering how junk-filled Earth orbits are, something that big is going to be a headache to move around (http://arstechnica.com/science/2013/07/how-nasa-steers-the-international-space-station-around-space-junk/). :smalleek:

I'm also skeptical of the feasibility of large-scale solar power for space. While the tech is getting more efficient, so is the efficiency of RTGs (https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator), which have long lifespans and low maintenance requirements. They are also designed to be very safe (capable of surviving a launch accident or reentry). Such devices would be great for powering communications and sensors on off-Earth bases, and recharging surface vehicles in unlit parts of other worlds.

[Emperordaniel]

I'm still not buying the solar panel power. The theoretical limit for a single layer is around 30%. Efficiency increases with thickness, but this also comes with a mass penalty. I think the theoretical efficiency limit for infinitely many layers is about 86%.

To power a city of 100,000 people takes about 200MW (possibly not including industry). Solar power is 1000W/m. Assuming a wildly optimistic 50% and a high enough orbit for minimal solar interruption, you'd need a 1km x 400m solar array. That's longer than the burj Khalifa and wider than London's Shard. It would be ridiculously fragile, difficult to maintain, and difficult to protect from debris.

Nuclear reactors of almost that capacity have been fitted to submarines. Yes, they're heavy. They'd probably have to be manufactured in space. But they'd be far less maintenance intensive, and the shielding requirements in space are not as difficult.

The ISS cells are about 14% efficient for comparison.

If you have an orbital station large enough to support a 100,000-person population, I don't see why you'd need a single solar array to power everything - just put smaller arrays all over the station, which when added up comes to the required solar panel area, plus some extra "just in case".

After all, the ISS - with its 32,333-cubic-foot internal pressurized volume - only supports an average of six crew (for four months; the ISS isn't self-supporting, which an orbital colony would probably need to be to some extent, thus increasing the required internal volume). Extrapolating from that for a population of 100,000 would give us a minimum internal pressurized volume of 538,883,333 cubic feet, equivalent to nearly 17,000 Boeing 747s. That's a lot of surface area to work with, even as an absolute minimum.

[Tev]

I don't see large-scale orbital colonies catching on. You have to keep sending supplies and space inside one is a premium. I see them more befitting the role of a gas station between planetary bases.

A base on the moon and Mars is easier to make self-sustaining because you have some of the building materials right there. The water can be extracted for drinking, converting into breathable air, fuel, and mixing with pulverized rock to make cement for building the base. Digging caverns under the surface for the base gives it a natural defense against solar radiation, helps with insulation against the cold, and can be made large for starting a hydroponic farm. When the technology becomes available, the moon has helium-3 for powering fusion reactors.

Good logic, bad assumptions.

1) "sending supplies" is not that difficult, raw materials are plentiful (asteroids are everywhere and weigh much more than you imagine + Moon is potentially supercheap source), transporting is getting cheaper and cheaper if you don't care about time (ion propulsion ftw) and processing materials into something useful might be easier in orbit than on Earth . . . if you manage to handle cooling. But that's completely different issue.

2) Building materials - see above

3)

Digging caverns ..., helps with insulation against the cold
It might help with cooling, but scaling is questionable. Cold will never be an issue in space. Maybe on Mars, but then you'll just celebrate arrival of your brand new Westinghouse reactor.
Also space in space ( :smallbiggrin: ) is actually limited by mass. And that is being solved as we speak. And I don't mean just SpaceX / other companies' reusability plans, but also inflatables.

4)

the moon has helium-3 for powering fusion reactors.
Assuming we will have usable helium-3 reactors. Pretty big and futuristic assumption, especially for in-space applications . . . I'd rather count with solar / nuclear.

edit: dumb typos

[RCgothic]

If you have an orbital station large enough to support a 100,000-person population, I don't see why you'd need a single solar array to power everything - just put smaller arrays all over the station, which when added up comes to the required solar panel area, plus some extra "just in case".

After all, the ISS - with its 32,333-cubic-foot internal pressurized volume - only supports an average of six crew (for four months; the ISS isn't self-supporting, which an orbital colony would probably need to be to some extent, thus increasing the required internal volume). Extrapolating from that for a population of 100,000 would give us a minimum internal pressurized volume of 538,883,333 cubic feet, equivalent to nearly 17,000 Boeing 747s. That's a lot of surface area to work with, even as an absolute minimum.

It doesn't matter what shape it is or where you put it, it's still the same area to maintain.

If that volume were a cube, that would have a sunside area of about .06sqkm, over six times smaller than the required area. There are also reasons you'd want to revolve the colony, increasing the panels you'd need if you were fixing them to the hull.

[Flickerdart]

In regards to using the moon for something, we can use its thorium to power liquid fluoride thorium reactors, which are already a thing. Mining it from the moon and delivering it to an orbiting habitat is much more effective than mining it on Earth and doing the same thing with a larger gravity well. Although there could be thorium in asteroids, too.

[halfeye]

btw how would that be of use for ISS?

Skylab was huge. It contained a lot of pressurised space that could have been used for habitation. That's probably the main loss, the instruments and electronics would have been very old by now. The ISS is bigger in terms of length, width and amount of solar panels, but the enclosed volume of Skylab was much bigger, combined they'd have been much better.


I agree that part of the point of self sustaining colonies off the planet is that we might lose the planet.

It's hard for me to imagine, though, a disaster big enough that life on a mars colony continues to be possible and yet they've lost the ability to write things down. Humans are really really good at finding ways to write things down, we've been doing it for thousands of years... and prior to that we were also really really really good at telling stories that our kids could tell their kids.

It's not impossible, but you need to come up with a way to kill or render permanently moronic every adult or even child over the age of... what, 5? For SF or gaming purposes, we can probably come up with dozens of ways to make it happen. But in terms of things to worry about it's pretty low on the list.

The thing is not that people would forget how to write, but that they'd need to make their own paper, and that gets tricky without established farming etc. Sure you don't need it as long as the tech holds up, but tech will eventually fail, and your supplies of shipped in paper will run out... The thing is you probably have to start in the stone age and work your way up through bronze, iron, steel, gunpowder, steam, petrol (gasolene), flight, before you can get back to space.

[Flickerdart]

Skylab was huge. It contained a lot of pressurised space that could have been used for habitation. That's probably the main loss, the instruments and electronics would have been very old by now. The ISS is bigger in terms of length, width and amount of solar panels, but the enclosed volume of Skylab was much bigger, combined they'd have been much better.
I was not aware that habitation space was a particularly sticky point for the ISS. It seems like connecting Skylab's ancient module to the rest of the ISS (both physically and digitally) would be way more trouble than just launching a habitation module of the appropriate size.

[DigoDragon]

1) "sending supplies" is not that difficult, raw materials are plentiful (asteroids are everywhere and weigh much more than you imagine + Moon is potentially supercheap source), transporting is getting cheaper and cheaper if you don't care about time (ion propulsion ftw) and processing materials into something useful might be easier in orbit than on Earth . . . if you manage to handle cooling. But that's completely different issue.

Organic supplies are where the difficulties come up. Building an orbital colony requires that we supply it with water, air, and soil from somewhere to start up a farming project. However, water is plentiful on other moons and planets. The soil on these moons and planets can be worked and made usable by adding the missing nutrients. Rather than bring these things to an orbital colony, it would be more efficient to build the colony where these materials already exist. Less mass to ship around.

And with the raw building materials already there, they can expand the colony more readily as well.



It might help with cooling, but scaling is questionable. Cold will never be an issue in space. Maybe on Mars, but then you'll just celebrate arrival of your brand new Westinghouse reactor.
Also space in space ( :smallbiggrin: ) is actually limited by mass. And that is being solved as we speak. And I don't mean just SpaceX / other companies' reusability plans, but also inflatables.

Continuing on my comment above about efficiency-- it takes energy/resources to keep an orbital colony in orbit (such as rocket propellant and gyros). If you build on a moon/planet, you don't need to steadily keep sending up new gyros and rocket propellant for the colony (or the materials to make them at the colony). Instead the energy/materials can be used for other things.



Assuming we will have usable helium-3 reactors. Pretty big and futuristic assumption, especially for in-space applications . . . I'd rather count with solar / nuclear.

Not a far-future technology though. We may succeed at a working reactor within 20-30 years.

[Ravens_cry]

For complexities sake, solar thermal could provide a good chunk of power with simple self expandability (aluminium mined from the lunar regolith will provide an excellent mirror, and 3d printing and sintering could provide the moving parts for the turbines.), especially if they're set up in areas at the lunar poles with almost 100% sunlight. You could set up vacuum capacitors in the open ground to store electricity, or use tanks of salt water to store the heat for times of darkness.

[ace rooster]

Solar panel area requirement vs habitable volume is a square cube relation. It's probably not feasible to power a very large orbital colony on solar power alone.

Nuclear reactors can at least scale with volume.

But cooling will be a very serious issue. Radiators will probably be the limiting factor. Note that having solar panels does not negate your need for radiators.


Cooling scales with area, and nuclear reactors are tied to cooling. Even if we only consider a colony and the power used in habitation areas we get that the area to volume ratio is very bounded. In particular, every joule generated is spent somewhere in the colony, and the colony must be kept cool. We can do some heat pumping to increase the temperature of the radiators that cool the colony, but we can't expect them to be able to operate above about 400K (already way higher than room temperature). At this temperature they would be radiating at 1.5kW per square meter. A more reasonable 250K radiator temperature (avoiding heat pumps) would radiate at about 230W per square meter, which is convienently about the same power as the solar panel on the other side of it is putting out :smallcool:.

Incidently, how much power do you think we need? If we were to build a 10km per side solar array it would provide 10GW at a conservative estimate. That is a sixth of the peak power use of the entire UK (which is considerably larger than 10km per side :smalltongue:), and more than it is easy to use. It is not as if space is a particularly limiting factor, and if you are harvesting materials that can be used for pressure vessels (ice being a fun one, due to also acting as shielding) then there is no reason to keep things particularly compact.

This is part of the reason I expect a semiconductor foundery in particular in space. Any further exploitation of space would be made considerably easier and cheaper if solar panels could be manufactured in space rather than having to be shipped. Highly specialised satelites could still be manufactured on earth, with the heavy power systems installed in orbit.



With regards to supplies on other planets, nitrogen is the main concern, being almost non existent on both the moon and mars. Nitrogen is critical for habitation, so these two are unsuitable without additional support.

[Ravens_cry]

Certainly help, though I think we'll see ISRU based solar thermal first.

[factotum]

Skylab was huge. It contained a lot of pressurised space that could have been used for habitation. That's probably the main loss, the instruments and electronics would have been very old by now. The ISS is bigger in terms of length, width and amount of solar panels, but the enclosed volume of Skylab was much bigger, combined they'd have been much better.

Er...where do you get that idea from? The pressurised volume of Skylab was a smidgeon under 320 cubic metres. ISS's pressurised volume is nearly three times that.

[halfeye]

I was not aware that habitation space was a particularly sticky point for the ISS. It seems like connecting Skylab's ancient module to the rest of the ISS (both physically and digitally) would be way more trouble than just launching a habitation module of the appropriate size.
I'm not saying that there was not enough room on the ISS for the people they had, obviously, there has to have been minimally enough.

what people don't seem to realise is how big skylab was. It was the whole third stage of a Saturn 5, the Saturn five was very big.


Er...where do you get that idea from? The pressurised volume of Skylab was a smidgeon under 320 cubic metres. ISS's pressurised volume is nearly three times that.

That's odd. I know how big the exterior of skylab was from the size of the model of the Saturn 5 I had as a kid. I presumed the interior filled the thing. If that's not so, I want to know what it was full of.

Hm, looks as if the ISS has grown a lot since I last took much notice of the details. All the more reason not to ditch this one.

[Ravens_cry]

I think the idea of it being so big is because it was one major module and that had the whole width of the Saturn V S-IVb third stage, which was quite a bit wider than any of the ISS modules.

[DavidSh]

Wikipedia gives the dimensions of the S-IVB third stage as
length = 17.8m
diameter = 6.6m

for a volume (length * pi * (diameter/2)^2) = 609 m^3.

The pressurized volume of Skylab was about 320 m^3, a little over half that.

The rest looks like it was the waste tank, the airlock module, including nitrogen and oxygen tanks, and the instrument unit. (See http://history.nasa.gov/diagrams/skylab.html)

[Ravens_cry]

Wikipedia gives the dimensions of the S-IVB third stage as
length = 17.8m
diameter = 6.6m

for a volume (length * pi * (diameter/2)^2) = 609 m^3.

The pressurized volume of Skylab was about 320 m^3, a little over half that.

The rest looks like it was the waste tank, the airlock module, including nitrogen and oxygen tanks, and the instrument unit. (See http://history.nasa.gov/diagrams/skylab.html)
It must have been amazing going from Apollo, which was already quite a bit roomier than the 'worn' spacecraft of Gemini and Mercury*, and then moving into the comparatively palatial Skylab.
*Fun fact: Gemini had less room per pilot than Mercury. And Borman and Lovell both spent 13 days and 18 and a half hours in it in flight!

[Tev]

Skylab WAS big. ISS modules were constrained by the shuttle's payload bay width and Proton fairing, so it is a bit cramped. Free space of course comes at a cost, like less instrumentation slots, and keeping Skylab alive for all that time would be extremely expensive, but it was excellent at least in this metric.

Space on ISS however isn't valued that much, otherwise NASA would press on with inflatable tech / more modules / throwing money at Russians so they finish their modules.


Organic supplies are where the difficulties come up.

Nope:

water
Non issue, there are icy bodies even among near-Earth objects, and some water is like everywhere? I would really like a citation saying there is NOT ****ton of water floating in space.

Also, recycling.


air
Recyclable, and you can get oxygen from water that's not particularly rare.


soil
https://en.wikipedia.org/wiki/Aeroponics
https://en.wikipedia.org/wiki/Hydroponics

There's really no trouble with farming in orbital colonies


The soil on these moons and planets can be worked and made usable by adding the missing nutrients.
. . . and removing all those toxic compounds. It looks great in the movie, but in reality it's questionable whether it's useful to use Mars soil for farming. Moon soil is obviously terrible for growing edible things.


Less mass to ship around.

Actually that's major problem of gravity wells - shipping mass in/out is grossly inefficient. Unless you want to make another totally closed loop colony (unreal within two centuries) you WILL ship mass around. Now how efficiently do you want to do it?


it takes energy/resources to keep an orbital colony in orbit
Umm, no? You don't need to make every colony in LEO, and even there it's not that expensive . . . 500km circular orbits decay in century or two.


Not a far-future technology though. We may succeed at a working reactor within 20-30 years.

It's funny how you bring up several "issues" with orbital colonies, and then claim we might get working fusion reactor in 30 years. We had several topics about major issues of those . . .


With regards to supplies on other planets, nitrogen is the main concern, being almost non existent on both the moon and mars. Nitrogen is critical for habitation, so these two are unsuitable without additional support.
Nitrogen is another abundant element in solar system, any source about its scarcity anywhere?

I might do more research about availability of essential elements later, but I would guess oxygen, nitrogen and hydrogen will be accessible in most places . . . if there would be problem with something it might be phosphorus.

[Flickerdart]

I'm not saying that there was not enough room on the ISS for the people they had, obviously, there has to have been minimally enough.

what people don't seem to realise is how big skylab was. It was the whole third stage of a Saturn 5, the Saturn five was very big.
Sure, but...so what? Unless there is a use for all that space, it's pointless. Except the added installation, upkeep, and maintenance costs make it worse than pointless.

Hell, according to Wikipedia, the pressurized volume of Skylab was a mere third of what the ISS has, so it isn't even all that big.

[Storm_Of_Snow]

It doesn't matter what shape it is or where you put it, it's still the same area to maintain.

If that volume were a cube, that would have a sunside area of about .06sqkm, over six times smaller than the required area. There are also reasons you'd want to revolve the colony, increasing the panels you'd need if you were fixing them to the hull.
You also need radiators for thermal regulation, armour against impactors, windows, all the other external mounted equipment (comms gear, external repair remotes and so on), plus you'll have the odd door here and there to get things in and out - not all of which can just be on the shadow-side of the habitat.

One way around it would be to put your panels on spars coming from a non-moving point that the habitat rotates around/from and craft dock to/in, rather than stuck on the hull of the habitat.

It probably also depends on where you are in system - if you're orbiting a planet rather than being in orbit around the sun, the constant charge/discharge cycles will eventually kill any batteries you use (the ones on the ISS last about 6 1/2 years). After that, you'd need to consider intended power consumption and the relative cost of producing that from solar cells or a reactor.

Recycling wastes - once there's multiple habitats, I could see at least one of them being a dedicated sewage treatment plant, taking shipments from the other habitats, processing it, then shipping the resultant material out to farming habitats to put onto the crops as fertilizer.

[Swordsmith]

Recycling wastes - once there's multiple habitats, I could see at least one of them being a dedicated sewage treatment plant, taking shipments from the other habitats, processing it, then shipping the resultant material out to farming habitats to put onto the crops as fertilizer.

Wow won't that be a job. Orbital sewage plant worker. Makes Quark look downright... oh wait, that job might be even more fun, Orbital Honeywagon Pilot!

[halfeye]

Sure, but...so what? Unless there is a use for all that space, it's pointless. Except the added installation, upkeep, and maintenance costs make it worse than pointless.

Hell, according to Wikipedia, the pressurized volume of Skylab was a mere third of what the ISS has, so it isn't even all that big.

Yeah, I was thinking that the ISS was smaller than it apparently now is. Still, I think in Skylab all that space was one room, don't know that for sure, and the astronauts had individual coffins to sleep in, but it's a lot of habitable space to just dump, it's not as if we're that short of aluminium down here. The replacement costs would be bigger than the maintenance costs I would expect. I really hate that aspects of NASA now want to dump the ISS in a few years.

[Flickerdart]

Yeah, I was thinking that the ISS was smaller than it apparently now is. Still, I think in Skylab all that space was one room, don't know that for sure, and the astronauts had individual coffins to sleep in, but it's a lot of habitable space to just dump, it's not as if we're that short of aluminium down here. The replacement costs would be bigger than the maintenance costs I would expect.
Really, you think that it will be cheaper to maintain a huge piece of junk in orbit for 20 years (with regular missions to refuel, resupply, and repair it), then refit it with docking systems that are compatible with the brand spanking new ISS while still in space, gut its electronics and life support entirely so they can be refitted with modern ones also while in space, then pilot the whole thing over to where the new station is being built and plug it in?

Incidentally, the inflation-adjusted habitation cost of Skylab is $20 million dollars per man-day, while the ISS's cost is a mere $7.5 million (http://www.thespacereview.com/article/1579/1), so it would be more expensive to do this even without the massive upkeep and refitting costs.

NASA pays big bucks to people who look at the stuff NASA has and decide what to do with it. They have a much better perspective than internet dudes. Personally, I trust NASA.


I really hate that aspects of NASA now want to dump the ISS in a few years.
The ISS always had a "best before" date. In 2028 when Boeing's new contract to service the ISS expires, the station will be 30 years old (with some of the older components from the Mir-2 project designed as early as 1976). Why do you want a 30 year old space station? Roskosmos has the right idea - salvage the instruments that are still useful, nail them to a new station, and dump the rest.

[Douglas]

dump the rest.
Preferably in a way that doesn't leave them further cluttering up Earth orbit.

[Emperordaniel]

Preferably in a way that doesn't leave them further cluttering up Earth orbit.

The traditional way for dumping space station debris is to let it re-enter/deliberately de-orbit it over the Pacific. Skylab just mis-aimed a little. :smalltongue:

[ace rooster]

Nitrogen is another abundant element in solar system, any source about its scarcity anywhere?

I might do more research about availability of essential elements later, but I would guess oxygen, nitrogen and hydrogen will be accessible in most places . . . if there would be problem with something it might be phosphorus.

Sure, lunar (http://www.lunarpedia.org/index.php?title=Nitrogen) is definately difficult, unless there are ammonia ices at the poles. This may be the case, but it is not a given. Mars is easier than I thought, as it does have some in it's atmosphere (https://en.wikipedia.org/wiki/Atmosphere_of_Mars). This is considerably more than I was realising, but having to process roughly two olympic swimming pools of atmosphere for every kilo of nitrogen will be one of the larger challenges I would think.

The reason nitrogen is an issue in the inner solar system is that it is very volitile. Nitrogen containing minerals that are not biologically created are rare as hens teeth, so that it will boil off any objects close to the sun that are not good at holding an atmosphere. The protoplanets that became the rocky planets for example would have had very little, with the planets getting volitiles from later icy comets. If we look at the composition of the earth (https://en.wikipedia.org/wiki/Earth#Chemical_composition) for example, we see that nitrogen does not feature at all, despite being very abundant in the universe. We only consider it common because the earth has an atmosphere. Does that answer your question?

I would think non volitile elements would be generally easy to come by on large objects, especially the light ones. If the objects has ever been hot enough to melt then you would get some enrichment of the surface with lighter elements, such as phosporus. You may not get very high concentrations, but you don't need nearly as much of these anyway.

[halfeye]

Really, you think that it will be cheaper to maintain a huge piece of junk in orbit for 20 years (with regular missions to refuel, resupply, and repair it), then refit it with docking systems that are compatible with the brand spanking new ISS while still in space, gut its electronics and life support entirely so they can be refitted with modern ones also while in space, then pilot the whole thing over to where the new station is being built and plug it in?
I think you build one hatch on the new system (maybe with an extension tube) to match with the old one. You refurbish just enough to keep it going. We don't yet have any capacity for smelting ore in space, yet we keep throwing metal away. Granted, we don't have any tech for recycling metal up there either, but making is a stage after refining, so it's not as if it's an alternative.


Incidentally, the inflation-adjusted habitation cost of Skylab is $20 million dollars per man-day, while the ISS's cost is a mere $7.5 million (http://www.thespacereview.com/article/1579/1), so it would be more expensive to do this even without the massive upkeep and refitting costs.
Yeah, but that includes the original fabrication costs and all the liftoff costs, keeping it up would have cost fuel, and transport costs for fuel, and it could have been used in the mean time.


NASA pays big bucks to people who look at the stuff NASA has and decide what to do with it. They have a much better perspective than internet dudes. Personally, I trust NASA.

Yeah, it pays big bucks, and those people have an interest in continuing to be paid. This isn't necessarily a good basis for trusting them.


The ISS always had a "best before" date. In 2028 when Boeing's new contract to service the ISS expires, the station will be 30 years old (with some of the older components from the Mir-2 project designed as early as 1976). Why do you want a 30 year old space station? Roskosmos has the right idea - salvage the instruments that are still useful, nail them to a new station, and dump the rest.

The cost of getting grams of metal to orbit is huge. Dumping tons for no reason isn't sensible in the long term.

[factotum]

Skylab just mis-aimed a little. :smalltongue:

Mainly because it wasn't aimed at all...it crashed because atmospheric drag in LEO slowed it sufficiently to bring it out of orbit, and NASA didn't send up any rockets to help boost it because they were too busy building the Shuttle.

Anyway, re-using old space stations is not really a great move. They have an awful lot of hardware on board that has to keep running just to keep the people inside alive, and that hardware is both prone to wearing out and extremely difficult to replace in situ. Any prospective orbital colony would have the same issues, so would need a steady supply of raw materials and an on-board manufacturing facility to be able to replace worn out components.

[weaseldust]

With respect to power generation: you can always generate your power away from the colony, in whichever locations are most convenient, and then beam it to the colony with massive lasers. You would need several generators, though, because, whether a colony is in orbit or on a planetary surface, it won't always have line of sight to the generator.


In some ways, the economics of extraterrestrial colonies is more interesting and problematic than the engineering. It's worth noting that it's historically rare for people to form colonies in inhospitable places on Earth. (Exceptions are scientific bases and certain religious communities.) Colonies were normally set up in places that could already be cultivated and were livable for humans without requiring a massive engineering project to be undertaken first.

I suppose ocean-going ships were a somewhat significant engineering project at first, but they were designed for other purposes than just making colonisation possible and, once colonists got off the boat, they could set about farming and so on without any prior investment. Some ancient irrigation projects were massive feats of engineering that made certain areas more livable, but they tended to be in places where people had already settled and were used to allow the land to support larger populations.

The point is that you don't see people creating large settlements in the desert or on the tops of mountains just because they can. There has to be some incentive to be there. Large settlements in that kind of place are rare and don't attract general settlers, only specialists. E.g. there are forts and monasteries on the tops of mountains, but you don't see large towns growing up around them, only the minimum population necessary to support the soldiers/monks.

I'm thinking that, in a civilian colony, rather than a military or scientific outpost, colonists would probably have to buy into the colony and then get a certain amount of living space, access to utilities, and so on. The cost would probably be quite steep, so you'd have to either just want to be in space enough to be willing to pay for it (which makes sense for a holiday resort, but not as the basis for large-scale settlement) or you'd have to have a way of making the money back, with interest, from living in space. And for you to be better off in space than on Earth, there would have to be economic opportunities in space that didn't exist on Earth. What would those be? Perhaps some kind of manufacturing that is only possible in 0g conditions? (This is ignoring the political system of the colony because discussion of that might fall foul of the rules of the forum.)

[Flickerdart]

Yeah, it pays big bucks, and those people have an interest in continuing to be paid. This isn't necessarily a good basis for trusting them.
Alright, you got me. NASA is actually just a conspiracy to funnel government funding into the pockets of nerds. Only internet randos know the best way to forge ahead in space!

[Sith_Happens]

Alright, you got me. NASA is actually just a conspiracy to funnel government funding into the pockets of nerds reverse-engineer Decepticons.

Fixed that for you.:smallwink:

[LibraryOgre]

In some ways, the economics of extraterrestrial colonies is more interesting and problematic than the engineering. It's worth noting that it's historically rare for people to form colonies in inhospitable places on Earth. (Exceptions are scientific bases and certain religious communities.) Colonies were normally set up in places that could already be cultivated and were livable for humans without requiring a massive engineering project to be undertaken first.
...
The point is that you don't see people creating large settlements in the desert or on the tops of mountains just because they can. There has to be some incentive to be there. Large settlements in that kind of place are rare and don't attract general settlers, only specialists. E.g. there are forts and monasteries on the tops of mountains, but you don't see large towns growing up around them, only the minimum population necessary to support the soldiers/monks.


As often, it comes down to money. We do have an example of colonies set up, on Earth, in relatively inhospitable places for resource extraction: They're called deep-sea oil rigs. Sure, they're supplied from home instead of attempting to grow their own, but that's because it's more economical to send a ship out to them than to have them try to grow what they need. Another case, you might look at Greenland, as settled from Iceland... fairly inhospitable, but better political climate for the first settlers than Iceland and Norway, at the time, and survivable with luck, work, and technological advantage.

[Tev]

RE: economy of space colonies -
Comparisons to "inhospitable" places on Earth have one big problem - their potential is at best comparable to other places on Earth.
Space has very cheap energy and extremely abundant mineral resources, which will be easier to mine with growing industry. Mining on Earth will only get more expensive. So economic potential of any place on the Earth is in the long term dwarfed by potential of space economy.

And for really long term there is not just "mankind survival" issue, but also defense one: populated gravity wells are by definition super-easy target for kinetic bombardment, while orbital colonies with comparable population are harder to wipe out with even hundred times more projectiles. Also it's kind of hard to fight that way from surface of Earth (or any planet for that matter), so orbital colonies will have huge advantage over surface ones.

So moving to space on scale of millenia is inevitable. Only question is whether (and if not now then when) are we ready for it.


Great stuff

Thanks, it does answer a lot of my questions :smallsmile:


We don't yet have any capacity for smelting ore in space, yet we keep throwing metal away.

You are ignoring the issue of material degradatinon, which is very fast in LEO conditions.


Alright, you got me. NASA is actually just a conspiracy to funnel government funding into the pockets of nerds. Only internet randos know the best way to forge ahead in space!

Be careful with that, according to many space enthusiasts SLS is just a jobs program for few senators' districts. And it sure seems designed in weirdly (http://www.nasaspaceflight.com/2016/01/ksc-meeting-sls-scrambling-manifest-plan/) expensive (http://www.nasaspaceflight.com/2016/01/nasa-defends-restart-rs-25-production/) way.

[halfeye]

You are ignoring the issue of material degradatinon, which is very fast in LEO conditions.

Yes I am, because metals are elements or alloys of elements, they don't degrade into anything else.

[AgentPaper]

Yes I am, because metals are elements or alloys of elements, they don't degrade into anything else.

They are degraded by micrometeorite impacts, though.

[DavidSh]

Also, metals may react with the atomic oxygen in the environment of low earth orbit. Sort of like rust.
I quote NASA on the results from the Long Duration Exposure Facility experiments.

Metals are higly variable in their response to the LEO environment. Gold and platinum are nonreactive. Osmium forms a volatile oxide and is rapidly eroded under exposure to atomic oxygen. Silver, which forms a nonprotective oxide, is rapidly eroded. Other metals (Al, Cu, Ga, Ge, Ir, Mo, Ni, Ti, and Sn) show some level of reaction unless protected. Contamination is a major contributor to exposure effects on metal surfaces. Absorptance is significantly greater for bare aluminum than for chromic-anodized aluminum. Emittance is significantly less for aluminum than for chromic-snodized aluminum. The surface properties of both bare aluminum and chromic-anodized aluminum are little changed by exposure to LEO environmental conditions. Magnesium in aluminum alloys is preferentially oxidized relative to aluminum. An oxide coating forms on exposure of copper to atomic oxygen that impedes further oxidation. The oxide coating adversely affects the optical properties of copper. Copper without surface protection may be used for extended periods of time in aplications where thermal management and optical performance requirements are not critical.

In summary, effects of exposure on metals ranged from essentially no effect, to surface color changes due to contamination deposits, to some degradation due to oxidation, to extreme damage and loss of material under atomic oxygen exposure. The changes to the metals are essentially due to surface or near-surface effects. For materials which form non-passivating oxides, the damage can be extensive over time.

This doesn't indicate that oxidation is a problem for the usual structural materials, though.

I add that NASA's web pages on the LDEF, http://setas-www.larc.nasa.gov/LDEF/index.html, is a site worth looking at.

[halfeye]

They are degraded by micrometeorite impacts, though.
They would be, but how often do those happen?

The Moon is apparently covered in impact craters, but it's billions of years old, it has had a lot of time to pick up those scars, and there is no weather to remove them.

I'm not aware of the ISS being punctured so far, or any other spacecraft taking damage that was definitively caused by a meteoroid.


Also, metals may react with the atomic oxygen in the environment of low earth orbit. Sort of like rust.
I quote NASA on the results from the Long Duration Exposure Facility experiments.


This doesn't indicate that oxidation is a problem for the usual structural materials, though.

I add that NASA's web pages on the LDEF, http://setas-www.larc.nasa.gov/LDEF/index.html, is a site worth looking at.

That's interesting, but it wouldn't prevent moving the ISS to a higher orbit, where that would be less of a factor, and it doesn't sound as if it's a big factor now.

That website is horrible for me, a stripy grey white ground with white text on it that completely disappears in the white strips, and the text is formatted so it's either too small to read, or all off the right side of the screen with no scroll bar to use to get at it. If you're the maintainer, this is with Firefox in Win 7.

[hamishspence]

I'm not aware of the ISS being punctured so far, or any other spacecraft taking damage that was definitively caused by a meteoroid.

It happens - but it tends to be space junk rather than rock:

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

[Tev]

They would be, but how often do those happen?

The Moon is apparently covered in impact craters, but it's billions of years old, it has had a lot of time to pick up those scars, and there is no weather to remove them.

I'm not aware of the ISS being punctured so far, or any other spacecraft taking damage that was definitively caused by a meteoroid.

Err it really is not that simple.

1) micro/nano meteorites are actually not that rare, there are tiny craters spread over ISS
2) it's not single source of damage, biggest ones are IIRC temperature differences and radiation. Micrometeorites and atomic oxygen aren't helping either.
3) It seems like you have no idea about degradation of materials in LEO, for example from very quick google search see degradation of Kapton: http://www.chemistry.illinois.edu/research/materials/seminar_abstracts/documents/AbadeerAbstract.pdf

Reboost of ISS to higher orbit:
1) expensive
2) little or rather negative benefit - unless you're keeping it functional (super expensive) you just have nice piece of space junk that's huge debris hazard especially as it ceases to have capability of dodging debris clouds
3) Van Allen belts - good luck boosting iss with its fragile structure (ergo small thrust and long time spent there) through those.

NASA is sometimes stupidly directed (have I mentioned SLS? Also Constellation), but unless you have very good understanding of the problem you should listen to what they say . . . and they say it's not really good idea to keep it in orbit after 2028.

[Emperordaniel]

We have at least one example of a (partially-)functioning satellite being effectively outright disabled by a micrometeorite - ESA's Olympus-1 telecomm satellite (https://en.wikipedia.org/wiki/Olympus-1).

On the subject of preserving the ISS, I'll quote someone from a different forum (http://forum.kerbalspaceprogram.com/index.php?/topic/130021-letting-the-iss-burn-upwhy/&do=findComment&comment=2364530):

The ISS has a shelf life which is determined by: solar panels, structural fatigue, seals, filters, fluids, insulation, paint, etc... and also obsolescence. It needs to be actively controlled, which costs money. If you turn off the environmental control, bacteria, fungus, and mold will take over, rendering it uninhabitable. If you turn off MMOD avoidance, it will eventually get hit and break up. If you turn off attitude control, it will start tumbling. It might settle down into a gravity gradient, but drag and gravity will pull and push it around, causing stress on the structure. If you power it down, it will be only a matter of time before it vents its atmosphere, leaks, and breaks up up. Without maintenance, paint and insulation will flake off a create a cloud of debris around it.

Basically, once it's turned off, there will be no fixing it or bringing it back to life. It's dead.

[Storm_Of_Snow]

Well, you could potentially add other modules, then retire the older ones as they reach their design life, maybe removing components that are still usable so you don't have to ship more mass into orbit, before attaching a small thruster pack, sealing the airlock doors and and detaching them for disposal by re-entry.

[halfeye]

Err it really is not that simple.
It never is :smallyuk:


1) micro/nano meteorites are actually not that rare, there are tiny craters spread over ISS
2) it's not single source of damage, biggest ones are IIRC temperature differences and radiation. Micrometeorites and atomic oxygen aren't helping either.
3) It seems like you have no idea about degradation of materials in LEO, for example from very quick google search see degradation of Kapton: http://www.chemistry.illinois.edu/research/materials/seminar_abstracts/documents/AbadeerAbstract.pdf

1 ISS is a chunk of metals and stuff, small holes on it don't make a big difference to its mass.
2 Since there seems to be a fear of radiation at higher levels, I'm not suggesting using ISS as a habitat, it could perhap be used for pressurised storage, or maybe not.
3 The degradation of kapton seems to be a particularly severe case, presumably they've stopped using that stuff if the colour matters.


Reboost of ISS to higher orbit:
1) expensive
2) little or rather negative benefit - unless you're keeping it functional (super expensive) you just have nice piece of space junk that's huge debris hazard especially as it ceases to have capability of dodging debris clouds
3) Van Allen belts - good luck boosting iss with its fragile structure (ergo small thrust and long time spent there) through those.

NASA is sometimes stupidly directed (have I mentioned SLS? Also Constellation), but unless you have very good understanding of the problem you should listen to what they say . . . and they say it's not really good idea to keep it in orbit after 2028.

1 Compared to getting the same mass to cis-lunar space from the ground, not even close.
2 So long as it's relatively speaking stationary, it shouldn't be a problem. It will be a nice piece of junk, that can be recycled, when it's finished being used. Throwing it in landfill would be a tremendous waste of resources, and up there, reuse and recycling are going to mean a lot more than they will ever mean down here.
3 Magnetic fields? slow should be better, less induced current yes?

The ISS is not only a NASA project, there's a Mir in there, and some other non-USA gear too.

[factotum]

The ISS is not only a NASA project, there's a Mir in there, and some other non-USA gear too.

While it's entirely true that there are Russian modules on the ISS, none of them was part of Mir. That particular station was de-orbited in 2001.

[AgentPaper]

Halfeye, melting down and reusing the ISS would not be cheaper than simply re-launching its mass back up in a few decades. Even ignoring the fact that launch costs are going down (radically, if musk has anything to do with it), it would take an orbital factory larger than the ISS to melt down the ISS, filter out impurities, and then re-forge the steel into usable pieces. And that's if you only go to the steel, and not the other valuable materials. And then you need to turn that raw steel into something useful, which takes even more new materials and construction in space. A simple metal can is no use to anyone without radiation shielding, insulation, probably windows and electronics hookups, etc. Look how long it takes to put together anISS module on earth, where we have easy access to everything, then imagine trying to do that in space, where you can't go get a spare tool if yours breaks. And of course this can't be done by robots either, so you need to send up housing and crew replacements.

If you're going to go through that much trouble, you're going to want to gather more material than just the ISS. You're going to want an asteroid to mine, and make something that would be impossible to send up in one piece, like the core structure of a large ring station or the hull of a large habitat. And you're going to want to do it for a long time, not just as long as it takes to chew through the ISS.

Seriously, NASA is not full of idiots. They make mistakes or go the wrong direction sometimes (coughspaceshuttlecough) but they are not stupid. If you're going to accuse them of being stupid like this, it'd be nice if you would do at least the bare minimum research (Google/Wikipedia) before making big and confident statements like this.

[Sith_Happens]

3 [Van Allen belts are] Magnetic fields?

No, they're altitude bands full of ionizing radiation.

[Emperordaniel]

No, they're altitude bands full of ionizing radiation.

The lunar Apollo missions basically got lucky by going through the thinner part of the belts really fast - neither of which would apply to a hypothetical ISS-boosting mission.

[halfeye]

While it's entirely true that there are Russian modules on the ISS, none of them was part of Mir. That particular station was de-orbited in 2001.
More waste. :smallfrown:

Looks like politics to me, so I'll say no more here.

[Flickerdart]

More waste. :smallfrown:
Bro, read up on Mir. That station was on fire practically around the clock. Being inside it was literally a death wish.

[AgentPaper]

More waste. :smallfrown:

Looks like politics to me, so I'll say no more here.

It's not politics, it's economics. Keeping the ISS around is simply not worth the effort to do so (once it stops being operational). If anything, I would expect politicians to try and keep it up there far longer than it's useful to do so, out of some misguided desire to get more use out of their significant investment, or to use it as a symbol of progress and international unity.

Regardless, it was NASA who decided that deorbiting the ISS was a better option than trying to preserve it by kicking it up to a higher orbit. In fact, the latter was their original idea, until a committee specifically created to look at this issue figured out that deorbiting was the better option. And nobody loves the ISS more than NASA.

I'll also note that none of this is going to happen in the near future. It has yet to be decided what will be done with the ISS, and it'll be up there until at least 2028, barring some kind of disaster. These plans are for what happens IF the ISS becomes non-functional, not when. I wouldn't be surprised if the ISS continues for much, much longer, being continuously added to and eventually removing and de-orbiting specific sections (after harvesting anything useful) that are too out-of-date or have been damaged somehow.

[Ravens_cry]

While it's entirely true that there are Russian modules on the ISS, none of them was part of Mir. That particular station was de-orbited in 2001.
What halfeye means is the Russian modules were originally meant for a planned Mir 2.

[halfeye]

What halfeye means is the Russian modules were originally meant for a planned Mir 2.

I wish I did, I was just ignorant.


It's not politics, it's economics.


On 28 March 2015, Russian sources announced that Roscosmos and NASA had agreed to collaborate on the development of a replacement for the current ISS.[24][25] NASA later issued a guarded statement expressing thanks for Russia's interest in future cooperation in space exploration, but fell short of confirming the Russian announcement.

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

I think the cold war is threatening to resurface, and that's politics. Urgh. :smallyuk: :smallannoyed:

[georgie_leech]

I wish I did, I was just ignorant.





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

I think the cold war is threatening to resurface, and that's politics. Urgh. :smallyuk: :smallannoyed:

If it were politics preventing NASA and the Russians from cooperating, that would be an incentive to keep the ISS around longer rather than needing to rebuild a new one to replace it on their own :smalltongue: