Electric space propulsion at the Institute of Space Systems Stuttgart: from low-power to high-power for nuclear electric propulsion applications

Abstract Future deep-space exploration missions require propulsion systems that exceed the performance capabilities of conventional chemical propulsion technologies. In particular, missions demanding high total velocity increment together with acceptable propellant mass fractions motivate the development of advanced electric propulsion systems (EPSs) and nuclear-powered spacecraft architectures. This paper provides an overview of the fundamentals of space propulsion with emphasis on EPSs, nuclear electric propulsion (NEP), and nuclear thermal propulsion. Different mission and transfer strategies are discussed together with the fundamental trade-off between propellant efficiency, transfer duration, and thrust generation. The importance of high exhaust velocity propulsion systems for deep-space exploration is highlighted using the Tsiolkovsky rocket equation and typical mission requirements. Furthermore, the paper reviews EPSs developed at the Institute of Space Systems ( IRS ) Stuttgart over more than three decades of research activities. The investigated propulsion concepts include electrothermal arcjets, steady-state self-field and applied-field magnetoplasmadynamic thrusters, pulsed plasma thrusters, and advanced hybrid and electrodeless propulsion concepts. Experimental performance characteristics ranging from low-power CubeSat propulsion systems up to high-power thrusters in the 100 kW class are summarized. The latter are high-power EPSs that are capable to be applied for the high velocity increment missions mentioned previously. In addition, the vacuum plasma wind tunnel facilities and experimental infrastructure used for thruster characterization under representative space conditions are presented. Finally, recent and ongoing research activities related to nuclear-powered spacecraft with German academic participation are discussed, demonstrating the contribution of the IRS to the development and experimental investigation of advanced EPSs for future NEP missions.