After seeing all the Starship failures, having something with a membrane keep things in place seems like an obvious solution. Has it been considered or tested - or do we simply lack a material that is elastic at the (cryogenic) temperatures required? What would it theoretically take? What subjects would you need to study to develop such a material?
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1$\begingroup$ A similar idea is using moving diaphragms for the tank ends. No image link but this Youtube video shows an example (link is to point in video where diagram is shown). $\endgroup$– Alex HajnalCommented Apr 21, 2021 at 8:44
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1$\begingroup$ @BenCrowell I presume that's a reference to the various Starship prototypes. SN1, SN2, ... $\endgroup$– Alex HajnalCommented Apr 21, 2021 at 18:46
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1$\begingroup$ @BenCrowell ...with SN standing for Serial Number. $\endgroup$– Alex HajnalCommented Apr 21, 2021 at 18:54
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They do!
Many propellant tank, especially those required to work in zero-g environments, do use just such a bladder-inside-a-tank for the fuel. Typically monopropellants for thrusters.
It completely removes the requirement for Ullage of the propellants, but adds complexity, cost, mass and failure modes.
Additionally, flexible bags are a bit hard to make at deep cryogenic temperatures.
Additionally, flexible bags that can contain 200 tons of cryogenic liquid sloshing around under 5 g of acceleration are.... simply impossible to manufacture.
I don't think we will ever have the technology to make a soft bag that can hold 1000tonnes (200 tonnes under 5g) of cryogenic liquid that is sloshing around.
For interest: take a peek at this. Work on developing a bladder that is cryogenic compatible. But max size very much small.
https://www.geekwire.com/2020/ancient-art-origami-provides-pathway-building-better-tank-rocket-fuel/
answered Apr 20, 2021 at 20:24
CuteKItty_pleaseStopBArkingCuteKItty_pleaseStopBArking
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$\begingroup$ It's worth noting that the ones that operate long term aren't cryogenic fuels, so... $\endgroup$– PearsonArtPhoto ♦Commented Apr 20, 2021 at 20:32
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2$\begingroup$ Do any boosters use these? $\endgroup$ Commented Apr 20, 2021 at 21:08
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$\begingroup$ @OrganicMarble From the first link: "Our bladder tanks are used on the 400 N Attitude and Orbital Control System (AOCS) of all versions of Ariane 5 and in the VEGA 200 N Roll and Attitude Control System (RACS)." $\endgroup$ Commented Apr 21, 2021 at 8:05
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2$\begingroup$ Those are RCS systems. Not the booster tankage. $\endgroup$ Commented Apr 21, 2021 at 11:09
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