The question What happens when supercritical fuel tanks deplete below critical point? suggests some possible scenarios when the pressure of a tank is in danger of dropping below the supercritical point in temperature or pressure:
- Do rockets not use the remaining contents?
- Do they just use up the remaining contents without halting given the acceleration of the vehicle would make location of liquid and gaseous sections predictable?
- Heat the contents so it stay supercritical until mostly empty?
The currently accepted answer thoroughly documents how the Space Shuttle procedures invoke a redline so that the H2 and O2 reactant tanks for electrical power always remained supercritical and never became sloshable liquid+gas mixture.
The O2 and H2 tanks had quantity "redlines" defined - operation of the tank heaters below those quantities could cause the heaters to overheat. The redlines were 2.5 % in the H2 tanks, 6.5 % in the O2 tanks.
So I'd like to ask if there are any examples where a tank of something in a spacecraft was allowed to drop below supercritical and change into a mixture of liquid plus gas that then had the potential to slosh, and if it had some mechanism for handling said slosh potential.
Question: Are there examples of a spacecraft designed for transitions from supercritical to liquid+gas mixtures?
This could happen in tanks where contents are cryogenic and then warm up over time to become supercritical then depleted to drop below supercritical, or tanks initially charged as supercritical then depleted, or any other imaginable scenario.
This answer discusses transitions a bit.