Water on the moon

[neutron starr]

i saw this on the daily show last night looks good for a fuel source if we had a polywell for electrolosis.

http://www.nasa.gov/mission_pages/Mini- ... osits.html

[CaptainBeowulf]

600 million metric tons - nice amount. But still, once we get ourselves settled on an area and using resources, we can run through them fast. Water has three major uses:

1. Hydrogen and oxygen for high-performance conventional rocket fuel
2. Liquid water for hydroponics, drinking, and washing
3. Oxygen extracted from the water for breathing (although you need a lot of nitrogen to mix with it as pure oxygen becomes toxic for humans after breathing it for a bit)

What we really need to make before we go out there is a well developed plan of how to use all that water effectively - burning it all for fuel over several decades wouldn't be the best long-term approach.

Any power source can of course be used for electrolysis - a fission nuke based on a submarine design adapted for zero-g/low-g function would do fine as well.

[blaisepascal]

600 million metric tons - nice amount. But still, once we get ourselves settled on an area and using resources, we can run through them fast. Water has three major uses:

1. Hydrogen and oxygen for high-performance conventional rocket fuel
2. Liquid water for hydroponics, drinking, and washing
3. Oxygen extracted from the water for breathing (although you need a lot of nitrogen to mix with it as pure oxygen becomes toxic for humans after breathing it for a bit)

Properly done, 2. and 3. wouldn't "use up" water as it could be recycled. Hydroponics would convert water and CO2 into O2 and food, and we would convert O2 and food to water and CO2.

I'm also of the belief that as long as the partial pressure of O2 is about 4-5psi, it doesn't matter what the rest of the inert mix, or what pressure it is. Really deep divers use He as a mix gas to get really high pressures with less risk of nitrogen narcosis, and I'm pretty sure the astronauts use close to pure O2 at 5psi for EVAs.

What we really need to make before we go out there is a well developed plan of how to use all that water effectively - burning it all for fuel over several decades wouldn't be the best long-term approach.

How do you burn water for fuel? With chlorine trifluoride?

[Aero]

How do you burn water for fuel? With chlorine trifluoride?

By striping off the hydrogen and blasting it out the back end of your spacecraft.That leaves you with 500 million tons of pure oxygen.

[MirariNefas]

I'm also of the belief that as long as the partial pressure of O2 is about 4-5psi, it doesn't matter what the rest of the inert mix, or what pressure it is. Really deep divers use He as a mix gas to get really high pressures with less risk of nitrogen narcosis, and I'm pretty sure the astronauts use close to pure O2 at 5psi for EVAs.

Total pressure might matter a little over the long term, though it can at least get as low as, say, whatever the Tibetans deal with up there on the roof of the world. I'm sure there's been some long term animal studies on lower pressures, so I bet someone knows just how much we can get away with.

It matters more in ways not directly related to health, I think. It matters for suits because the pressure stiffens joints. It matters for the habitat when you have to slowly equalize to suit pressure, especially if you're jumping into an emergency suit during a blowout. It also matters for structural integrity, to prevent that blowout. Lots of reasons to go with a relatively low pressure.

[MSimon]

I'm also of the belief that as long as the partial pressure of O2 is about 4-5psi, it doesn't matter what the rest of the inert mix, or what pressure it is. Really deep divers use He as a mix gas to get really high pressures with less risk of nitrogen narcosis, and I'm pretty sure the astronauts use close to pure O2 at 5psi for EVAs.

Total pressure might matter a little over the long term, though it can at least get as low as, say, whatever the Tibetans deal with up there on the roof of the world. I'm sure there's been some long term animal studies on lower pressures, so I bet someone knows just how much we can get away with.

It matters more in ways not directly related to health, I think. It matters for suits because the pressure stiffens joints. It matters for the habitat when you have to slowly equalize to suit pressure, especially if you're jumping into an emergency suit during a blowout. It also matters for structural integrity, to prevent that blowout. Lots of reasons to go with a relatively low pressure.

And some really good reasons not to go with pure O2 - like fire risk.

http://en.wikipedia.org/wiki/Apollo_1

Although that was O2 at 16 psi. Not sure that 4 - 5 psi will make a lot of difference. Other than reducing the inventory of "free" oxygen.

[Skipjack]

Yupp, Apollo 1 tought us a lesson...
Though, I dont think the nitrogen will be such a huge problem. Once you have it up there it would never really go away (or only very little of it). I dont think that hydroponics allone would be sufficient to guarantee a steady oxygen supply. That would be assuming a 100% efficient conversion rate both ways. Plus large greenhouses do need quite a bit of energy by themselves. A technical solution to split the CO2 back into oxygen and carbon would IMHO still be necessary in addition to this. The energy for that would also have to come from somewhere.
With a polywell that would not be a problem.
Fuel would be a very different issue though and that is where I see the biggest potential. Also, with a polywell you would only need the hydrogen. You superheat it and eject it out the back (like a nuclear thermal rocket engine). As Aero said, that leaves you with tons of pure oxygen, for whatever use.

[taniwha]

One perfectly good use for the oxygen: reaction mass. At the same specific impulse in an ion engine, oxygen (single electron removal) requires 1/16th the current as hydrogen to produce the same thrust, though the drive voltage will need to be 16 times that of hydrogen. (603kA, 187kV vs 9.6MA, 11.7kV for 0.1kg/s@1500km/s (112.5GW)). I'd much rather supply the voltage than the current.

Better yet, you can get oxygen from the lunar regolith, no need to waste that precious water. As CaptainBeowulf pointed out, once we start using it, 600Mt won't seem to be all that much after all. Only problem is, storage can be a bitch (LOX is highly reactive).

[Giorgio]

One perfectly good use for the oxygen: reaction mass. At the same specific impulse in an ion engine, oxygen (single electron removal) requires 1/16th the current as hydrogen to produce the same thrust, though the drive voltage will need to be 16 times that of hydrogen. (603kA, 187kV vs 9.6MA, 11.7kV for 0.1kg/s@1500km/s (112.5GW)). I'd much rather supply the voltage than the current.

Better yet, you can get oxygen from the lunar regolith, no need to waste that precious water. As CaptainBeowulf pointed out, once we start using it, 600Mt won't seem to be all that much after all. Only problem is, storage can be a bitch (LOX is highly reactive).

True, 600Million Tons are not that much, but if we will have that kind of powerful space engines (112,5 MW) the easiest thing will probably be to send something to collect some of those icy rocks that are orbiting in the asteroids belt.
That will solve any supply issues.

[taniwha]

Take a closer look. That's GW, not MW. Even more power . 120MW won't get you anywhere all that fast (though it will get you far if you are very patient, so long as you're already in orbit). However, even with only 120MW, no need to collect space icebergs: that much power should do a nice job of Lunar O2 production.

That said, the icebergs will still be collected, but for other purposes (deep space re-massing (reaction mass is not fuel: fuel goes into the reactor, reaction mass goes into the engines)), colonization (yeah, I read and enjoyed "Heart of the Comet"), mining...

[Giorgio]

Typing mistake, I should learn to read back before pressing the post button

[taniwha]

Ok (I'm prone to both reading and typing mistakes, so it could have been either).

[pfrit]

One of the most important uses for water on the moon will be sheilding. Few things can beat it for both radiation sheilding and meteroric sheilding. And thermal sheilding for that matter. Don't think of a lunar base as a big bubble on the surface. Think about a bunker underneath as much ice as possible. Dig a big hole and build your base at the bottom. Fill in with liquid water. Wait for it to freeze. move in.

[MirariNefas]

Better seal that stuff in or you'll lose it all come day.

[MSimon]

Better seal that stuff in or you'll lose it all come day.

If the hole is deep enough in the right place you won't lose much. After all there is water on the moon.