I’m not sure I would say the exhaust is wasted just because it doesn’t go into the main combustion chamber. The exhaust of the turbo fuel pump on one Saturn V

I’m not sure I would say the exhaust is wasted just because it doesn’t go into the main combustion chamber. The exhaust of the turbo fuel pump on one Saturn V F-1 engine provides more thrust than an F-16 in afterburner. The Raptor is the first operational Full Flow Staged Combustion rocket engine. https://en.m.wikipedia.org/wiki/Staged_combustion_cycle#Full-flow_staged_combustion_cycle https://en.m.wikipedia.org/wiki/Staged_combustion_cycle#Full...