Wikipedia:Reference desk/Archives/Science/2023 April 5

= April 5 =

Space X Rocket Fuel
Could someone please tell me how Space-X produces their rocket fuel? I assume the liquid oxygen is produced by electrolysis, is it possible to do this using solar power? and how is the methane produced? Thanks 49.177.70.210 (talk) 07:40, 5 April 2023 (UTC)


 * See liquid rocket propellant, liquid oxygen, and methane for production methods. I doubt very much they would produce their own fuel. Why not just buy it on the open market? I suppose it would be possible using solar power but that would be a painfully slow process. Shantavira|feed me 08:26, 5 April 2023 (UTC)


 * There are several ways to produce oxygen, but for high purity in industrial quantity, it's done by distillation of air. Methane is produced by distillation of natural gas. The pumps to run the distillation process require electricity, which could come from renewable sources. For some other common rocket fuels: RP-1 (a kind of kerosene) is distilled from crude oil, LH2 (liquid hydrogen) is normally produced by a reaction of steam with methane. Hypergolics and solids require some more complex chemistry. All these fuels are produced in bulk by chemical companies. Buying those fuels off the shelf is much cheaper for the space companies than producing it themselves.
 * SpaceX likes talking about making rocket fuel on Mars. There, they would use a reaction of carbon dioxide with water to produce both methane and oxygen. But that's just talk; they aren't anywhere close to a return mission to Mars. Crewed Mars mission have been twenty years into the future for decades. PiusImpavidus (talk) 09:30, 5 April 2023 (UTC)


 * Industrial quantities of liquid oxygen are generally produced by fractional distillation of air; see air separation.
 * And yes, SpaceX seems to source their liquid oxygen on the open market rather than making their own. There was some substantial coverage in 2021 raising concerns about potential shortages, because so much liquid oxygen was being consumed for medical purposes. TenOfAllTrades(talk) 12:24, 5 April 2023 (UTC)
 * Anything that can be done using electricity can be done with electricity produced from solar power. The economics are a different matter. WP:WHAAOE: Power-to-gas includes power-to-H2 and power-to-methane. -- 47.155.46.15 (talk) 06:24, 6 April 2023 (UTC)
 * See also: Sabatier reaction nagualdesign 17:11, 9 April 2023 (UTC)

Can I buy reverse invisible pens?
Not invisible molecules that become visible with UV or heat but visible molecules that become invisible with one of those things (perhaps breaking up to pieces that like to evaporate?). For semi-permanently marking expensive paper i.e. an atlas still being able to unmark and reuse up to preferably 10+ cycles before the process would naked eye affect it much. For example a pen with ink at least 102 or 103 times less UV-resistant than any common poster ink or book paper. Sagittarian Milky Way (talk) 20:12, 5 April 2023 (UTC)
 * Nautical charts are quite expensive and are regularly marked up in 2B pencil and then erased. Is this the sort of thing you were meaning? Martin of Sheffield (talk) 20:59, 5 April 2023 (UTC)
 * I remember most of the original blue ink for ocean coming off an eraser-sized strip of childhood book before the ballpoint ink did (though a 2B or HB pencil wouldn't have needed as much rubbing). How do I tell in advance about how many times a particular book or map can be erased before it looks bad? Sagittarian Milky Way (talk) 21:47, 5 April 2023 (UTC)
 * I would try using a fixative spray before marking with pencil. 136.56.52.157 (talk) 21:56, 5 April 2023 (UTC)
 * Don't use HB (a "normal" pencil) or you will leave a permanent impression. FYI, it is not uncommon for skippers to ban anything other than 2B being anywhere near the chart table (and that especially includes biros).  It only takes someone plotting a fix in a hurry, or at night, or in bad weather with the wrong implement to ruin a chart. Martin of Sheffield (talk) 22:26, 5 April 2023 (UTC)
 * See Erasermate. 2601:646:9882:46E0:3053:CD03:BA5:3522 (talk) 07:05, 6 April 2023 (UTC)
 * 2B or not 2B, there's no question. Go away, ye swab. Clarityfiend (talk) 08:08, 6 April 2023 (UTC)
 * :-) Martin of Sheffield (talk) 09:18, 6 April 2023 (UTC)
 * Or see "" and there is also FriXion brand pens, or look up "heat erase pen". Graeme Bartlett (talk) 07:09, 6 April 2023 (UTC)
 * Are you asking about disappearing ink? -- Jayron 32 10:49, 6 April 2023 (UTC)
 * The lye one obviously wouldn't work cause even if repeatedly getting your paper above 10.5 pH just to see your notes doesn't permanently wrinkle the paper or something you couldn't erase one set of marks and write another. Lightly marking with the darker than usual 2B pencil seems safer. Sagittarian Milky Way (talk) 13:45, 6 April 2023 (UTC)