# What percent of fuel is consumed in powering the turbopumps? [closed]

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?

• 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. – Manu H Jan 26 at 14:33
• 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. – Ilmari Karonen Jan 26 at 20:22