Apollo LM-derived projects

publiusr said:
Having propellants that don't need ISRU to get you back home are considered bugs, not features--today.
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Pretty much because making your own propellant is the LEAST of the things you need to do in order to go back into space in any sustainable way. Keep in mind that you not only have to haul the propellant to 'get back' you then have to haul more propellant just to get that propellant to the destination in the first place.

There are a lot of good arguments about not complicating "things" in order to just get back to the Moon and just shipping propellant "outward" as you go instead of ISRU right off the bat. But at some point you're going to have to tackle cryogenic propellant transfer and eventually local production if you are going to stay for any length of time so also arguments for the sooner, the better.

Randy
 
RanulfC said:
There are a lot of good arguments about not complicating "things" in order to just get back to the Moon and just shipping propellant "outward" as you go instead of ISRU right off the bat. But at some point you're going to have to tackle cryogenic propellant transfer and eventually local production if you are going to stay for any length of time so also arguments for the sooner, the better.
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For the past year or so I've been working on a project that has included some assessment of ISRU. People who have not worked on this stuff don't understand just how much more development work needs to be done. All the work done to date has mostly been focused on proof of concept at small scale. In other words, can you take CO2 out of the Martian atmosphere and turn it into something useful? Can you process some lunar dirt to get some useful materials (like O2) out of it? But right now, that has been done with tiny amounts of material. Even when the answer is "yes," there's a huge amount of work that remains to demonstrate that it can be scaled up. The experiment that went to Mars on the Perseverance rover is incredibly small scale.

There are a lot of questions that have to be answered in scaling something like this up. One of the biggest ones is how much energy does it take and what will supply that energy? If you need many thousands of kilowatts to run the production plant, you may not be able to produce that kind of energy. And the energy is needed not only for the production process itself, but for the mining (something has to scoop up or ingest the raw materials) as well as storage on the back end. So the question about power is how much power is needed for all stages of production.

Another question that is easily skipped over by just about everybody on the outside is that when people talk about "volatiles" on the Moon, we don't actually know what form those volatiles are. If it is crushed ice underneath a few inches of lunar dust, that would be great. But what if the volatiles are baked into glass particles from the initial cometary impacts? Now you have to figure out the energy needed to melt ice (which is actually a lot of energy), vs the energy needed to melt glass (which is a lot lot more energy).

I know a guy who taught an engineering class and one of the problems he gave to his students was to calculate the amount of energy needed to convert one cubic meter of water ice into hydrogen and oxygen. You can now ask an AI to do that, so I did so and got this answer: "It takes approximately 130 to 140 gigajoules of energy to convert one cubic meter of water ice to hydrogen and oxygen, with the bulk of the energy used for the electrolysis process itself, and a smaller amount needed to melt the ice first."

ISRU is a tough problem.
 
blackstar said:
"It takes approximately 130 to 140 gigajoules of energy to convert one cubic meter of water ice to hydrogen and oxygen, with the bulk of the energy used for the electrolysis process itself, and a smaller amount needed to melt the ice first."
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and how much if process the regolith for Oxygen ?
the AI answer:
The energy required to process lunar regolith for oxygen production is estimated to be approximately
87.5 megajoules (MJ) per kilogram of liquid oxygen (LOX) produced, using methods like hydrogen reduction of ilmenite.
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Google say
The regolith mass can reach up to 840 to 1,920 kg per cubic meter (0.84 to 1.92 g/cm³).
One cubic meter of lunar regolith contains approximately 630 kilograms of oxygen rest are minerals
 
blackstar said:
For the past year or so I've been working on a project that has included some assessment of ISRU. People who have not worked on this stuff don't understand just how much more development work needs to be done.
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I have been saying similar for quite a while and I know the tech is nowhere near ready, hence why I support the "propellant-forward" until it gets near enough :)
One of the main reasons I suspect it's been over-hyped is the standard method (Zubrin-et-al) for making methane from hydrogen, (not water which is a common mistake) which, yes is a bit 'easier' for storage but you need that "seed" and far to many people simply "assume" the rest of the "ISRU" methods are just as easy.

blackstar said:
All the work done to date has mostly been focused on proof of concept at small scale. In other words, can you take CO2 out of the Martian atmosphere and turn it into something useful? Can you process some lunar dirt to get some useful materials (like O2) out of it? But right now, that has been done with tiny amounts of material. Even when the answer is "yes," there's a huge amount of work that remains to demonstrate that it can be scaled up. The experiment that went to Mars on the Perseverance rover is incredibly small scale.
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But it showed it's "possible" which is all the hype needed... Unfortunately :(

blackstar said:
There are a lot of questions that have to be answered in scaling something like this up. One of the biggest ones is how much energy does it take and what will supply that energy? If you need many thousands of kilowatts to run the production plant, you may not be able to produce that kind of energy. And the energy is needed not only for the production process itself, but for the mining (something has to scoop up or ingest the raw materials) as well as storage on the back end. So the question about power is how much power is needed for all stages of production.
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Kerbal Power Program! More Power! :)

blackstar said:
Another question that is easily skipped over by just about everybody on the outside is that when people talk about "volatiles" on the Moon, we don't actually know what form those volatiles are. If it is crushed ice underneath a few inches of lunar dust, that would be great. But what if the volatiles are baked into glass particles from the initial cometary impacts? Now you have to figure out the energy needed to melt ice (which is actually a lot of energy), vs the energy needed to melt glass (which is a lot lot more energy).
Click to expand...

Hmmm, so just melt the Moon? We'll get right on that :)

blackstar said:
I know a guy who taught an engineering class and one of the problems he gave to his students was to calculate the amount of energy needed to convert one cubic meter of water ice into hydrogen and oxygen. You can now ask an AI to do that, so I did so and got this answer: "It takes approximately 130 to 140 gigajoules of energy to convert one cubic meter of water ice to hydrogen and oxygen, with the bulk of the energy used for the electrolysis process itself, and a smaller amount needed to melt the ice first."
Click to expand...

Well let's keep in mind that many of us come to "space" because someone who taught a college class asked his students to envision colonies OTHER than on planets :)
(One of the biggest things I miss about the old L5 Society was it was actually much more grounded in "reality" and having to deal with it to get where we wanted to go rather than depending on the government or clueless billionaires to do everything)

blackstar said:
ISRU is a tough problem.
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Yep and the fact that space is intrinsically hostile to us does not make it any easier and neither does hand-waving the issues away as "simple engineering". :rolleyes:

Thanks

Randy
 
RanulfC said:
One of the main reasons I suspect it's been over-hyped is the standard method (Zubrin-et-al) for making methane from hydrogen, (not water which is a common mistake) which, yes is a bit 'easier' for storage but you need that "seed" and far to many people simply "assume" the rest of the "ISRU" methods are just as easy.
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He has long been one of the worst culprits, with a tendency of glibly responding to any criticism of his ideas with some "simple" solution rather than doing the math and identifying a path to solving the problem. I've seen his glib responses to things like bone density loss among astronauts ("simply spin the spacecraft for artificial gravity"), radiation hazards ("simply send smokers"), and propellant production ("simply ISRU"). I remember decades ago hearing him talk about Mars Direct and say that it was going to be easy to do the ISRU because it would be powered by a nuclear reactor and we had already built one in 1964, ignoring all the details about both that program and the difference in environments.

If we expect people to spend lots of time on planetary surfaces, and if we buy into the concept of a spacefaring civilization, then of course ISRU is necessary. But nobody should assume that it's easy, or that we are even close to doing it. Just be honest about that.
 
I've read that in the past Zubrin has poo-pooed and badmouthed the VASIMR concept, I got the impression he was talking out of his arse.
 
The new war of the currents, I remember that article.

The smoking bit I agreed with. I never smoked, but since I am a hermit…if I “augered in” on Mars, there would be no Mercury housewife ringing her hands—nothing but cheers from half the folks here. I wouldn’t have it any other way.

The ISRU deal? No thanks.

Was it Granlund that did the cartoon of “The Good Zubrin Fairy” making 5.7 km/sec vanish? A classic.
 

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