Injector design and test for a high power electrodeless plasma thruster

Abstract: The HPEP (High Performance Electric Propulsion) thruster is expected to be the outcomecof an innovative project initiated by the Swedish Space Corporation. It combines the concept of a 10 kW electrodeless plasma thruster designed by the Elwing Company and the ADN based monopropellant LMP-103S developed by ECAPS and used in the HPGP thrusters of the Prisma Satellites. Using a chemically energetic propellant in an EP thruster will allow mass and cost reduction by providing two propulsion systems sharing the same tank. This thruster will be suitable for the apogee raising manoeuvre of geostationary satellites; it will allow to carry more transponders and to obtain a better return on investment than with a classical apogee kick motor. This Master Thesis focuses on the design and test of the injector that will thermally decompose the liquid LMP-103S so it can enter in the plasma chamber in a gaseous state. The heating power required by the injector is calculated, which leads to a final design composed by a cartridge heater of 400 W inserted in a stainless steel cylinder. The liquid flows through seven other holes drilled around the heater. This injector is tested at both atmospheric and low pressure with deionized water. Results regarding the power required to vaporize water confirm the theoretical estimation. Steam flow without any liquid droplets is achieved in steady state at low pressure with a maximum temperature on the surface of the injector between 230°C and260°C.