How is cryogenic fuel & oxidizer kept at cryogenic temperatures in rockets? I am mostly interested in the first stage of launch vehicles rather than something like a Centaur that keeps hydrolox cold for a long time. So how does something like a Falcon 9 first stage mitigate boil-off? Does one have an isolated tank that has a rate of boil-off that is slow enough that by the time the first stage has expended all of its fuel boil off isn't a concern or is there some complicated active glycol jacketing?
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$\begingroup$ Boil off is kind of beneficial after lift off because it generates gas that fills the empty tank space left by the consumed fuel and equalizes tank pressure. $\endgroup$– user3528438Commented Apr 24, 2020 at 17:55
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This answer helps to explain it--you just accept the boiloff for the short time before the propellant is consumed, and Falcon 9 has to be fueled immediately before launch. But Saiboogu didn't really mention that cryogenic tanks are insulated. That's discussed a bit here in a NASA forum. Delta IV, Space Shuttle external tank, and Ariane V are examples. Cork is a popular material. It's more important for liquid hydrogen since that has such a low boiling point. I don't think the Atlas V liquid oxygen tank is insulated; at least I can't find anything that says it is.
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1$\begingroup$ there's more about "rocket cork" here: Why would rocket bodies use specifically ablative coatings to reduce boil-off of cryogenic propellants? Is ablation important for this? $\endgroup$– uhohCommented Apr 25, 2020 at 1:13