Wikipedia:Reference desk/Archives/Science/2021 October 11

= October 11 =

Suspicious entry in List of S-phrases
Is "S38/2: In case of insufficient ventilation wear suitable respiratory equipment and stay away from children" real? It seems a bit like a joke to me because of the "children" part. It was added here. Ariel. (talk) 02:48, 11 October 2021 (UTC) Edit: It seems like a combination of S38 and S2, and I think it's a joke. S8/10 also seems like a joke. Anyone have a proper, authoritative list? Ariel. (talk) 02:51, 11 October 2021 (UTC)
 * S phrases are now long obsolete, and I and perhaps others are gradually replacing them with H and P phrases in Wikipedia articles. However in the case of this list, those entries do not match sources, and I have removed them. I agree with you that they were jokes. You can see authoritative list here: https://web.archive.org/web/20090205124908/https://eur-lex.europa.eu/LexUriServ/site/en/oj/2006/l_363/l_36320061220en02410343.pdf Graeme Bartlett (talk) 04:54, 11 October 2021 (UTC)

Reusable crew capsules
How come the Dragon and Starliner capsules are reusable, but not older designs like Apollo and Soyuz? What technologies or difficulties made it unfeasible for earlier space capsule designs to be reusable in contrast to winged designs like the Space Shuttle?  Naruto love hinata 5 (talk · contributions) 05:35, 11 October 2021 (UTC)
 * They have ablative heat shields and are not reusable. The STS used new technology for its ceramic tiles. But there was one catastrophic failure in a damaged/missing tile. Sleigh (talk) 06:17, 11 October 2021 (UTC)
 * You might want to tell SpaceX Dragon is not reusable, as they've reused them many times already. But yes, the heat shield gets replaced. Fgf10 (talk) 07:48, 11 October 2021 (UTC)
 * For earlier reusable systems see the proposed Space Transportation System, which directly led to the Space Shuttle program. The Space Shuttle orbiter used the Space Shuttle thermal protection system for re-entry. Alansplodge (talk) 11:03, 11 October 2021 (UTC)
 * The links do not explain why reusability was not an option with earlier capsule designs such as Mercury/Gemini/Apollo. I'm aware that one Gemini capsule did fly to space twice (with the first flight being part of the Gemini test program and the second as the test flight for the Manned Orbiting Laboratory) and other examples are mentioned in this Scott Manley video, but none of these capsules flew with crew onboard and in any case reuse wasn't the norm for space capsules back then.  Naruto love hinata 5 (talk · contributions) 11:10, 11 October 2021 (UTC)
 * If you've ever seen any of these capsules in museums, they look sufficiently battered that trying to re-use one does not seem very safe. ←Baseball Bugs What's up, Doc? carrots→ 13:33, 11 October 2021 (UTC)
 * They certainly look rough, but to the untrained eye, they don't look any worse than recovered SpaceX dragon capsules.
 * ApLundell (talk) 01:01, 12 October 2021 (UTC)


 * The "difficulties" were that we had not yet figured out the techniques to make such capsules reusable, or to make the materials necessary for this to be possible. Science, by its nature, advances: that's part of the point of it. {The poster formerly known as 87.81.230.195} 90.205.224.83 (talk) 20:58, 11 October 2021 (UTC)
 * Right, but what were the unresolved dificulties? We already know they were difficult. And also unresolved. ApLundell (talk) 01:01, 12 October 2021 (UTC)
 * As noted already, the biggest issues with the single-use capsules was the heat shields to allow the capsule to survive re-entry. Earlier capsules, like Apollo, Gemini, Mercury, etc.  used ablative heat shields, they dissipated the heat destructively (which is to say, they destroyed themselves as they dissipated the heat) and the heat shield is the biggest engineering difficulty, both in terms of time and cost.  The earlier capsules were cheaper to manufacture fresh than to refurbish.  The biggest advance of the reusable crafts like the space shuttle was the introduction of modular, non-ablative heat shields; they used a combination of tiles and "blankets", and the shields themselves could be re-used many times, as well as the fact that individual tiles and blankets can be replaced rather than having to replace the whole shield, makes it MUCH more cost-effective to have a re-usable space ship given the advances in heat-shielding technology.  We have an entire article on the Space Shuttle thermal protection system.  -- Jayron 32 18:01, 12 October 2021 (UTC)
 * It also should be noted that with the early capsules, it was not known how well the capsules would survive re-entry and splash-down. Making the trip survivable once is a much smaller risk that making the trip survivable a bunch of times.  Given that the early years of the space race were trying to get things done in an efficient manner, building a bunch of capsules (like 10-12) all at once, and then using them one at a time is much more time efficient (and safer!) than building one capsule, letting it land, refurbishing it, and hoping it works a bunch of times.  Generally, by the time the first mission-ready capsule was flown, all of the others were already built, and only required some adjustments and tweaks (based on data from the early missions).  In other words, perhaps they could have built only one capsule and used it a bunch of times, but it is safer and faster to build a bunch at once and then use them.  -- Jayron 32 18:13, 12 October 2021 (UTC)
 * And they were probably glad they did it that way, after Grissom's capsule sank to the bottom of the ocean. ←Baseball Bugs What's up, Doc? carrots→ 20:24, 12 October 2021 (UTC)
 * He nearly established the "Highest plus Deepest" record later taken (presumably) by Richard Garriott (though strictly I suppose you have to survive both). I wonder if we have (or should have) an article on this record? Presumably a mountaineering submariner might have been one of the earlier holders. {The poster formerly known as 87.81.230.195} 90.193.128.221 (talk) 21:52, 12 October 2021 (UTC)
 * I think Auguste Piccard deserves more honour there. He set both a highest and deepest record (although I don't know whether he still held his highest record when setting the deepest record). PiusImpavidus (talk) 07:41, 13 October 2021 (UTC)
 * Garriott's record is – reportedly, citation needed – for his recording a sci-fi flick at extreme height/depth, which he did both in low Earth orbit (about 420 km up) and at the bottom of the Mariana Trench (about 11 km down). AFAIK Piccard never shot a science-fiction film at any level. --Lambiam 20:15, 13 October 2021 (UTC)
 * Those were the specific circumstances, but I was only thinking about the more general "altitude and depth" aspect. {The poster formerly known as 87.81.230.195} 90.193.128.151 (talk) 17:59, 14 October 2021 (UTC)