Low-cost orbit manoeuvres for minisatellites using novel resistojet thrusters

Electric propulsion using resistojets operating at low power (similar to 100 W) and using liquid propellants have re-emerged as attractive propulsion options for small satellites. Compared to low-power pulsed plasma thrusters (PPT), the resistojet achieves 50 times the increase in thrust (similar to 1-50 mN), which is necessary to overcome drag at solar maximum for small satellites in high drag obits (similar to 200 km). Two resistojet thrusters have been developed at the Surrey Space Centre (SSC), which utilize a packed bed of silicon carbide (SiC) particles for the heat exchanger. A thermodynamic model has been developed to study and optimize the thruster design and a series of practical performance tests with both nitrous oxide and water as propellants has been completed at the USAF Research Lab (Edwards AFB) using the NASA-JPL inverted pendulum thrust stand. Endurance tests (similar to 300 h duration) were conducted to determine possible lifetime limitations or failure modes. The results are very encouraging and resistojet thrusters are now proposed as options for future USAF and SSC minisatellite missions. This paper describes the complete resistojet system, test results for the USAF Mighty Sat II. I and its flight performance, its performance and integration on the UoSAT-12 minisatellite and its launch in April 1999 where this novel technique was demonstrated for the first time in low Earth orbit on 26 July 1999.