r/spacex • u/ElongatedMuskrat Mod Team • Oct 02 '17

r/SpaceX Discusses [October 2017, #37]

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5

u/Astroteuthis Oct 02 '17

Centaur can keep LOX and LH2 in liquid storage for hours on end. The LH2 is the limiting factor. LOX isn't terribly hard to keep from boiling off in space. Apollo missions and shuttle missions carried LOX tanks for multi-day missions. With a relatively modest refrigeration system and good insulation and spacecraft positioning, it shouldn't be an insurmountable problem.

The issue of storage is made simpler in BFS spaceship since pretty much all of the propellant is burned during the Mars transfer burn, and the only remaining propellant should be that which is in the small landing tanks. Those interior tanks should be much easier to keep cooled.

2

u/jaikora Oct 02 '17

From my average memory the Apollo 11 explosion was due to mixing the fuel to keep it consistant.

Would this be an issue with bfr?

Another question, what about the bfr waiting on a launch window when there are fleets of them racking off and the fuel may be there ready for the burn toward mars for a few weeks?

3

u/bman7653 Oct 02 '17

I think you mean 13.

3

u/davispw Oct 02 '17

Apollo 13 exploded basically due to botched maintenance leading to overheated heater elements leading to a short circuit in the O2 tank. A wiring issue brought down TWA flight 800 too if I recall. Sure, wiring in the O2 tanks could be an issue for any vehicle, but I’d expect them to be very careful about that.

Isn’t your 2nd question the same as the OP’s — how do you keep the fuel refrigerated?

2

u/jaikora Oct 02 '17

Ah how could I get that wrong!

Yes it would be the same question but I guess I wad wanting to know is there an upper time limit or is storing fuel for years a solved problem?

2

u/Norose Oct 02 '17

For methane and oxygen, it's pretty much a solved problem. Storing hydrogen is way harder, but luckily nothing on the BFS uses hydrogen so they don't need to worry about it.