4 ms·

Methane is supposed to be abundant on some planets and moons. Would there be enough light available to turn it into rocket fuel for trips back?

ekianjo 4y ago
Not sure . the amount of sunlight you get decreases with radius^3 and already at mars it gets quite low. Any planet beyond is probably not going to cut it.
- zbrozek 4y ago
  r^2, right? It'd be ~r^3 if vacuum represented significant path loss to light at the kinds of ranges we're talking about.
  - ncmncm 4y ago
    Right. But solar insolation at Mars is, indeed, low, just by the r^2 phenomenon. 40%, IIRC. But you should be able to use perovskite panels and not worry about them getting wet, oxidized, or hot. Those can operate at up to 40% efficiency, gaining back the difference. And, they are very light. You ought to be able to keep dust off electrostatically. Not that anybody will ever live on Mars, or need methane there.
MobiusHorizons 4y ago
Methane is already a viable rocket fuel. I don’t think it would make sense to convert to methanol first.
- perihelions 4y ago
  Methanol is actually one of the oldest liquid rocket fuels, dating to WW2. https://en.wikipedia.org/wiki/C-Stoff https://en.wikipedia.org/wiki/C-Stoff I don't think it's a very good rocket fuel (it's already partly oxidized, for a start). Clark's Ignition says Nazi wartime shortages were the reason for its addition to C-Stoff -- I'll quote page 13: - "But peroxide is not only a monopropellant, it's also a pretty good oxidizer. And Walter worked out a fuel for it that he called "C-Stoff." (The peroxide itself was called "T-Stoff.") Hydrazine hydrate, N2H4-H2O ignited spontaneously when it came in contact with peroxide (Walter was probably the first propellant man to discover such a phenomenon) and C-Stoff consisted of 30 percent hydrazine hydrate, 57 of methanol, and 13 of water, plus thirty milligrams per liter of copper as potassium cuprocyanide, to act as an ignition and combustion catalyst. The reason for the methanol and the water was the fact that hydrazine hydrate was hard to come by — so hard, in fact, that by the end of the war its percentage in C-Stoff was down to fifteen."

ekianjo 4y ago

Not sure . the amount of sunlight you get decreases with radius^3 and already at mars it gets quite low. Any planet beyond is probably not going to cut it.

zbrozek 4y ago
r^2, right? It'd be ~r^3 if vacuum represented significant path loss to light at the kinds of ranges we're talking about.
- ncmncm 4y ago
  Right. But solar insolation at Mars is, indeed, low, just by the r^2 phenomenon. 40%, IIRC. But you should be able to use perovskite panels and not worry about them getting wet, oxidized, or hot. Those can operate at up to 40% efficiency, gaining back the difference. And, they are very light. You ought to be able to keep dust off electrostatically. Not that anybody will ever live on Mars, or need methane there.

MobiusHorizons 4y ago

Methane is already a viable rocket fuel. I don’t think it would make sense to convert to methanol first.

perihelions 4y ago
Methanol is actually one of the oldest liquid rocket fuels, dating to WW2. https://en.wikipedia.org/wiki/C-Stoff https://en.wikipedia.org/wiki/C-Stoff I don't think it's a very good rocket fuel (it's already partly oxidized, for a start). Clark's Ignition says Nazi wartime shortages were the reason for its addition to C-Stoff -- I'll quote page 13: - "But peroxide is not only a monopropellant, it's also a pretty good oxidizer. And Walter worked out a fuel for it that he called "C-Stoff." (The peroxide itself was called "T-Stoff.") Hydrazine hydrate, N2H4-H2O ignited spontaneously when it came in contact with peroxide (Walter was probably the first propellant man to discover such a phenomenon) and C-Stoff consisted of 30 percent hydrazine hydrate, 57 of methanol, and 13 of water, plus thirty milligrams per liter of copper as potassium cuprocyanide, to act as an ignition and combustion catalyst. The reason for the methanol and the water was the fact that hydrazine hydrate was hard to come by — so hard, in fact, that by the end of the war its percentage in C-Stoff was down to fifteen."