Liquid propellant rocket engine cycles partially using electric turbopump

Studies on electric turbopumps for liquid rocket engines have recently increased. However, it has not been used in large-scale engines for heavy launch vehicles because the mass of power electronic devices, such as batteries and motors, has become too large. This paper proposes partial electric rocket engine cycles, in which all propellants are pressurized by conventional gas-turbine-driven turbopumps; however, an additional electric pump is used only to increase the pressure of the turbine inlet flow. It was found that the turbine flow rate was reduced and the total specific impulse increased using a reasonable sized electric turbopump for engines based on the expander bleed cycle. As a result, the launch capacity of a launch vehicle increases, even when accepting the extra mass of the electric turbopump system. The design feasibility of the electric turbopump was discussed, and it was concluded that such an electric pump system is feasible for upper-stage rocket engines using the current level of power electronics devices.