who designed a bipropellant rocket engine with liquid hydrogen and gas-generator cycle?
(AND spaceflight.rocket_engine_designer (JOIN spaceflight.rocket_engine_designer.rocket_engines (AND (JOIN (R spaceflight.rocket_engine_cycle.rocket_engines) m.04qqvv) (JOIN (R spaceflight.rocket_engine_fuel.rocket_engines) m.0g0nz))))