The maintenance of RPM in turbo pumps for liquid rocket engines is primarily controlled by regulating the flow of fuel and oxidizer. For the RS-25 Space Shuttle Main Engine, exhaust gas drives the pumps, with a valve used to throttle the exhaust flow. In contrast, electric pump-fed engines, such as Rocket Lab's Rutherford engine, utilize a different mechanism for RPM control. The complexity of throttleable turbine-fed systems arises from the potential for negative feedback, especially in staged combustion engines.
PREREQUISITESAerospace engineers, propulsion system designers, and students of rocket technology will benefit from this discussion on maintaining and controlling turbo pump RPM in liquid rocket engines.