Liquid-propellant engine and method of use

A rocket engine system comprising:

• one or more rocket engines comprising a combustion chamber and a nozzle;
• a turbine powering an electric generator via a power source;
• an electric motor configured to power an oxidizer pump and a fuel pump;
• a power management system electrically and communicatively connected to said electric generator, said electric motor, a computing device, and a plurality of valves;
• said computing device comprising a processor, data storage, and user interface;
• said power management system configured to direct and control power to and from said turbine, said electric generator, and said electric motor;
• said power management system further configured to control output of said oxidizer pump and said fuel pump via said plurality of valves, and said power management system further configured to monitor a temperature of said electric motor and a status of said electric generator;
• and
• said computing device configured to automatically operate said power management system to optimize efficiency of power output by said one or more rocket engines.