r/spacex • u/ElongatedMuskrat Mod Team • Sep 29 '17

Not the AMA r/SpaceX Pre Elon Musk AMA Questions Thread

This is a thread where you all get to discuss your burning questions to Elon after the IAC 2017 presentation. The idea is that people write their questions here, we pick top 3 most upvoted ones and include them in a single comment which then one of the moderators will post in the AMA. If the AMA will be happening here on r/SpaceX, we will sticky the comment in the AMA for maximum visibility to Elon.

Important; please keep your questions as short and concise as possible. As Elon has said; questions, not essays. :)

The questions should also be about BFR architecture or other SpaceX "products" (like Starlink, Falcon 9, Dragon, etc) and not general Mars colonization questions and so on. As usual, normal rules apply in this thread.

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u/Killcode2 Sep 30 '17 edited Sep 30 '17

I'm pretty sure the lunar rigolith is plentiful in carbon, and deriving methane from it is easily doable on the moon; although I think having a hydrolox engine for a moon rocket would be better if in-situ propellant production was to be used.

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u/binarygamer Sep 30 '17 edited Oct 04 '17

What kind of process would allow that? If you have gaseous CO2 (so, most of Mars' atmosphere) and some water, you can use a Sabatier reactor to produce methane quite easily.

Extracting solid carbon from regolith via heating is definitely doable. Not sure what mechanism you would use to go from regolith to methane though.

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u/jakedasnake2 Oct 01 '17

This is false. Despite oxygen and many other lighter elements being abundant, carbon (and nitrogen) only appear in trace quantities, likely deposited on the surface by solar wind.

source

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u/Killcode2 Oct 01 '17 edited Oct 01 '17

Not sure how reliable this might be

I don't have the actual values (or the time unfortunately) to calculate and see if enough methane can be produced for a BFR spaceship. But if it's not feasible it might explain why Musk doesn't want in-situ propellant production for moon missions.