If you could setup a permanent base on the moon....

[Peelee]

The point about oxidiser does raise a question, which is: what oxidiser are you most likely to be able to find on the Moon?

The lunar landscape is high in oxygen content, IIRC. The trick it to get it out of the rocks.

[Rockphed]

Plus,you get to call yourself a space lawyer. Which is just awesome.

Do space lawyers get to wear space suits while in court?

[Peelee]

Do space lawyers get to wear space suits while in court?

No, but they look stellar anyway.

[Tvtyrant]

No, but they look stellar anyway.

Their fashion is straight out of Cosmo :/

[Rakaydos]

It's been said that the moon is easier to reach and return from in case of emergency, but that mars is a safer place to BE, less likely to have an emergency that requires going home in the first place. A measurable atmosphere is huge when it comes to any potential habitation over long term, as radiation protection, meteor protection, and as a source to replace essential light elements that leak out of the habitat for any number of critical and non critical reasons. In addition, a 24 hour, 40 minute day is within the human ability to absorb without jetlag, making natural human diurnal cycles a possibility.

[Fat Rooster]

Hydrogen loses quite badly in terms of bulk, though--they didn't use LH2 in the first stage of the Saturn V, where efficiency gains would likely have mattered the most in terms of total fuel usage, because the required fuel tank would have simply been too big. The point about oxidiser does raise a question, which is: what oxidiser are you most likely to be able to find on the Moon? I don't think we actually have an answer for that. If oxygen is in short supply, but nitrogen and hydrogen are relatively plentiful, then hydrazine becomes a much better option for your rocket fuel than LH2--it might be slightly less efficient, but because it's available in much larger quantities it offsets that. I don't think we'll have a final answer for that until we actually have a moon base set up where people can do mining operations to find out what's beneath the surface, which brings us back to a reason for building the thing in the first place!

Bulk is a problem if you are pulling something through a thick atmosphere (unless you are aerobraking, where it actually helps), but once you are in space it isn't a problem. Hydrogen is certainly not ideal for first stages for that reason, but the geometric progression of staging actually means that a large upper stage is less of a problem. Instead of tapering down, the upper stages are just lower density (Some stability issues may occur, but are manageable). Performance improvements percolate down, so a 25% mass reduction on the upper stages will mean a 25% mass reduction in the lower stages, no matter what they burn, so you get most bang for your buck making the upper stages high performance (hence why you see a kerosene first stage on the Saturn 5, and inefficient solid fuel rockets for launch).

As for what oxidiser you will find on the moon, there is pretty much just oxygen, and oxygen is everywhere. Rocks are basically metal oxides, with the occasional sulphur or halogen thrown in. Water for hydrogen is available out of sunlight, but in sunlight you are extremely limited. Trace amounts of chlorine and fluorine are available, but are quire rare so we probably don't want to rely on them initially. Using fluorine engines in close proximity to earth is also a bit like throwing fridges into the upper atmosphere; The ozone implications are pretty messy. Might be worth using for landing on other planets though, as it does perform a little better than oxygen. Extremely hard to justify the complexity involved in that though, as hydrogen is lamb's milk next to handling fluorine. You could maybe use perchlorates, but their performance isn't great outside ammonium, and that needs nitrogen. Nitrogen and carbon are almost non existent because they are too volatile (as oxides), so even if you really wanted to use nitric acid or dinitrogen tetroxide it probably isn't possible. Hydrogen peroxide might be possible, but is far lower performance than hydrogen with oxygen and needs valuable hydrogen. Same goes for sulphuric acid.

The only thing that comes to mind that might radically change the numbers is if we find permanganate salts, as those can be turned into oxygen extremely easily. There is some evidence that they exist on Mars. We would still probably want to work with liquid oxygen though because the manganese is dead weight, and given how much reduced iron we already know about I would think finding oxidising salts unlikely.

The Universe is a big place, and anything is possible, but I can't think of a situation where you would end up with nitrogen but no oxygen. Where you get ammonia ices you can also expect water ice, and where there is enough gravity to keep nitrogen gas it will hold onto oxide rocks even better.

[halfeye]

It's been said that the moon is easier to reach and return from in case of emergency, but that mars is a safer place to BE, less likely to have an emergency that requires going home in the first place. A measurable atmosphere is huge when it comes to any potential habitation over long term, as radiation protection, meteor protection, and as a source to replace essential light elements that leak out of the habitat for any number of critical and non critical reasons. In addition, a 24 hour, 40 minute day is within the human ability to absorb without jetlag, making natural human diurnal cycles a possibility.

Mars is not that much safer than the Moon. You can't go out of doors on Mars without an airsupply, what atmosphere there is is poisonous, and it's really thin. The Moon doesn't have an atmosphere, so it's not poisonous.

[Rakaydos]

Mars is not that much safer than the Moon. You can't go out of doors on Mars without an airsupply, what atmosphere there is is poisonous, and it's really thin. The Moon doesn't have an atmosphere, so it's not poisonous.

That's not an effective difference, because the safety equipment isn't significantly different. But if you get an air leak on the moon, you have to ship in a replacement from Earth. If you get an air leak on Mars, you're already filtering the atmosphere for the fuel plant, so you patched the hole and replenished the air.

[Fat Rooster]

That's not an effective difference, because the safety equipment isn't significantly different. But if you get an air leak on the moon, you have to ship in a replacement from Earth. If you get an air leak on Mars, you're already filtering the atmosphere for the fuel plant, so you patched the hole and replenished the air.

Seconding this, sort of. A Lunar colony will always be entirely dependent on earth for carbon and nitrogen, and those can be lost very easily in gas leaks. Both are basically deserts, with hydrogen being non-trivial, so losing water could be a problem on both. Both want to be harvesting water fairly rapidly though. At any one time most of your nitrogen, carbon, and hydrogen will be tied up in non volatiles, so that even a sudden total decompression event should not lose you the majority of them. Worst case scenario you want to be producing ISRU oxygen on both, so switching to 100% oxygen atmospheres is viable short term. ie; imminent death is avoided in both cases. If you can react fast enough, water will mostly freeze in vacuum, so should be salvageable, at least enough for a few days. Your supplies should be fairly robust in both cases, except for food. Food production collapse could be a major problem. The difference is that on the Moon the people are just forced home, while people would actually starve on Mars.

Meteorites and radiation definitely require more consideration on the moon, but I think the problems you will get will be similar in magnitude to those that arise from not having the same medical facilities available. You will be talking optimisation problems rather than viability in both cases I think. Constructing pressure vessels is going to be the hard bit next to putting foil and a water tank around it. Both will need radiation protection anyway, so the extra protection required on a moon base is not substantially more difficult. Life on the moon will certainly be affected more by solar flare events, because the atmosphere on Mars is enough to deal with the low energy radiation. A bunker will be required for storms.

By far the biggest problem for the moon in my mind is the long nights. A small moon colony would be far more dependent on energy storage or transfer. Lose energy and you don't have for up to 15 days, and that can be lethal. Energy storage failing isn't much of a problem, because redundancy is easy to build and it should be relatively easy to fix. A power line hundreds of kilometres from anywhere taking a impact might cause severe problems though, as it is less likely to be redundant and harder to fix.

Landing pad design is far easier on Mars, as putting it far enough away avoids all problems. The tenuous atmosphere is enough to slow dust over short distances. On the Moon distance isn't enough. If grit is sprayed at 500mph by rocket exhaust at the pad it will keep going that speed till it hits something, up to 30km away... Not great for your solar panels. Incidently, this is another reason I don't see earth based landers (such as starship) being common in the medium term for the moon. The whole tall with engine on the bottom puts the engine low to the ground, needing long legs to minimise ground disruption. Non vacuum optimised engines or even higher pressure engines produce much higher exhaust density, which should increase spray velocity. Entirely non atmospheric landers can have gigantic engine bells, that would never fit in any fairing, mounted high on the sides. They can have long spindly legs with no compromises for earth landings.


The big difference is if Earth becomes uninhabitable, or unreachable. If Kessler syndrome hits badly enough that all colonies are isolated then Mars can thrive, while the Moon has to be very careful and cannot grow due to finite nitrogen and carbon. If it is dangerous to even try to aerobrake at earth then even getting nitrogen from Mars is difficult. This requires extreme Kessler syndrome though, as sending cargo to save dozens is only not going to be worth it if there is very low chance of it making it through even once. That scenario would not last long though, as Kessler syndrome that severe turns into a ring system pretty fast. Once the debris have become rings you can just go round them if your are going to the moon. As another aside; a ring system is a pretty good defence against further Kessler syndrome, so giving the Earth a ring system might be something we end up doing on purpose at some point. Use Lasers to maintain gaps in the rings at specific altitudes and accurately controlled satellites can stay safe while uncontrolled debris will interact with the rings pretty fast.

In the 'Earth is dead' scenario getting supplies from Mars should be doable. The extra energy available over Mars should make semiconductor manufacturing easier on the Moon, and they are light enough to transport. It might end up as a staging post for outer solar system exploration, as my gut feeling is that it would be easier to get materials from the Moon to Jupiter than from Mars's moons. Not run the numbers for a direct transfer, but a Venus assist transfer is definitely easier, and cargo will probably want to go that way.

[Wardog]

Nuclear is better than on earth for disposal of waste. You can designate a nice crater and just catapult stuff in.

Do you want to blast the Moon across the galaxy? Because that's how you blast the Moon across the galaxy.

Actually, I suspect you'd find gold isn't worth enough to ferry from the moon, and oil certainly isn't. Platinum, if you didn't find too much and crash the market might be, and diamonds and sapphires might be if we weren't already making them.

Plus, there are already so many diamonds on Earth that the diamond industry has to stockpile them so they don't crash the market. On the other hand, the (gem) diamond market is already so screwy and driven by status rather than normal suppy and demand, that it might not be that surprising if De Beers started mining Moon Diamonds just so they can sell them to bazillionairs for vastly more than is reasonable.

[Vizzerdrix]

The real money to be made with the moon, is in harvesting its cheese.

[Lord Torath]

The real money to be made with the moon, is in harvesting its cheese.

Everyone knows the moon's made of cheese...