Electric feed systems for liquid-propellant rockets

Liquid-propellant rocket feed systems based on electric pumps are compared with the more classical pressure-gas and turbopump systems. The design parameters entering in the definition of the system mass are highlighted, and a careful choice of the figures of merit is performed, in particular for the electric motors and batteries. Indeed, recent developments, taking into account new electric motors based on rare earth permanent magnets (neodymium-iron-boron) , and different lithium-based cells, show that the specific mass of the electric-pump system can be reduced to such an extent to make the proposed system competitive not only with the pressure-gas system but also with the turbopump one, at least for some applications such as small launchers and upper stage rockets. Further, electric motor and battery cell technologies currently under development could extend the proposed feed system convenience. Critical points related to electric-pump systems are also discussed.