On: NASA lays out how SpaceX will refuel Starships in low-Earth orbit

[avmich]

Thanks. I'd assume the boil-off should be insignificant, in a sense, or - alternatively - some active cooling systems can be used, they don't need to be big or complex.

[JumpCrisscross → avmich]

> I'd assume the boil-off should be insignificant

It should be, but we haven't done it yet [1].

> active cooling systems can be used, they don't need to be big or complex

Cooling in space is always complicated given the only way to dump heat is radiating (or dumping into ejected mass, i.e. boil off).

[1] https://en.wikipedia.org/wiki/Orbital_propellant_depot#Heavy...

[avmich → JumpCrisscross]

> It should be, but we haven't done it yet [1].

Yes, but there were some calculations for this - http://astronautix.com/n/n1blocksr.html - which hints on boiling off to be manageable for large stages.

[withinboredom → avmich]

You’ve got to put that heat somewhere… and space being a vacuum means there’s no where to put it.

[avmich → withinboredom]

Space radiators, I believe, are still having some space to evolve, particularly liquid droplet radiators.

[withinboredom → avmich]

And, where, pray, does that liquid come from ... in space? It also seems like a terrible idea to leave little ice particles flying around at hundreds of km/h...

[avmich → withinboredom]

You'd think that, but on Mir space station that kind of radiator showed some good results, and the liquid was gathered back with negligible losses.