Question for the Rocket Scientists

[USMCmech]

I have often wondered this question.

Any liquid fuel rocket requires extreamly high capacity fuel pumps, I rember hearing that the Shuttles fuel pumps can empty a swiming pool in 30 seconds.

What powers these pumps?

[NickH]

They use several pumps for both fuel and oxidiser, operated by gas turbines.

Wikipedia has a good article with lots of pictures.

[USMCmech]

Yeah, but how does a gas turbine work above the atomsphere?

Do they use LOX?

[NickH]

Yes. There are low pressure and high pressure pumps for both fuel and oxidiser.

The low pressure pumps are run by turbines driven by a small amount of the oxygen or hydrogen flow from their respective high pressure pumps, which then mostly ends up in the combustion chamber. The high pressure pump is driven by a turbine running from a preburner.

This is actually how the thrust from the engine is controlled. Valves control flow of oxygen and hydrogen to the preburners, which affects the speed of the turbine and hence the fuel/oxidiser pressure from the high pressure pumps into the main combustion chamber.

[meritflyer]

I knew that..

[jetman]

Originally Posted by USMCmech

Yeah, but how does a gas turbine work above the atomsphere?

Do they use LOX?

The ratio O/H to drive the pumps is less than 1: 1 When it reaches the main injector it is mix with the rest of the O. Ratio for final combustion is 6:1
The APU uses hydrazine for propelent.