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In gas generator cycle small portion of the fuel and oxidzier is burned in the preburner to drive centrifugal pumps feeding the main combustion chamber. But how is the fuel/oxidizer fed into the preburner, surely it has to be done against very high pressure? Logically, you would need an infinite series of turbopumps. Also, how is the pressure turned into the rotational kimetic energy? Are turbines similiar to jet engine's used?

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  • $\begingroup$ A gas generator extension attachted to the preburner similar to a solid fuel rocket may be used to start the turbine driving the turbopumps. Yes turbines are used to drive the pumps. $\endgroup$ – Uwe Jun 21 '18 at 21:06
  • $\begingroup$ OM, yes, and space.stackexchange.com/a/15303/20766 $\endgroup$ – Rob Jun 22 '18 at 2:11
  • $\begingroup$ As far as I know, the turbine in a gas generator cycle engine's turbopump is driven by gas from a gas generator, not a preburner. Preburners are used in staged combustion cycle engines where the turbine exhaust is burned again in the main combustion chamber. The exhaust from a gas generator cycle engine's turbine is not burned again. $\endgroup$ – user8269 Jul 5 '19 at 22:19