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The RD-170 consumes 5,300 lbs of fuel per second, including oxidizer. The turbopump produces 230,000 hp. If one assumes that roughly 1 lb of fuel is required to generate 1 lb of thrust (obviously this varies considerably), not including oxidizer. Assuming an oxidizer to fuel ratio of 3, then 3% of total fuel is used to power the turbopump. I realize there are more variables involved, but to get a rough guess, what would be the best path forward to estimate this number?

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  • $\begingroup$ I fail to understand if you are asking about specific impulse during startup phase (as you seem to speak of consume fuel vs thrust) or the amount of fuel consumed during startup phase vs total of fuel consumed during power flight. You should clarify that point. $\endgroup$ – Manu H Jan 26 at 14:33
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    $\begingroup$ Hi, user27128, and welcome to Stack Exchange. Could you please edit your question to clarify what you're trying to ask? The way I read it, it seems to be something like "if the turbopumps could be magically driven without burning any fuel, how much less fuel and oxidizer would the RD-170 consume?" — which kind of ignores the fact that the RD-170 engine uses a staged combustion cycle where the combustion products and excess oxidizer used to drive the turbopumps are eventually fed into the main combustion chamber and out the nozzle anyway. $\endgroup$ – Ilmari Karonen Jan 26 at 20:22
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Your question is a bit confusing because of your use of "fuel" to sometimes mean "fuel" and sometimes mean "propellants". Based on my interpretation of the question here is an answer.

The RD-170 consumes ~2400 kg/s of propellant. ~1800 kg/s of this propellant flows through the preburner of which ~33 kg/s is fuel (RP-1) and ~1767 kg/s is oxidizer (O2). The RP-1 is combusted in an excess of O2.

"If one assumes that roughly 1 lb of fuel is required to generate 1 lb of thrust" that would be a terrible engine. The RD-170 produces ~7900 kN vacuum thrust while consuming ~1729 kg/s of O2 and ~665 kg/s of RP-1.

  • The preburner fuel (RP-1) flow of ~33 kg/s is ~5% of the inlet fuel (RP-1) flow.
  • The total preburner propellant flow of ~1800 kg/s is ~75% of the total inlet propellant flow.

Source: Cycles for Earth-to-Orbit Propulsion by Manski and Levack

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