Ammonia Micro-Resistojet Propulsion System for CubeSats

Busek proposes to develop a flight prototype micro resistojet (MRJ) propulsion system for CubeSat satellites. Ammonia has been chosen as the propellant because it is self-pressurizing, relatively high density, and is well suited as a cold gas propellant for propulsive attitude and control system. The MRJ system will be base-lined at 5 Watts with options up to 15 Watts total power, 5 milliNewton thrust and predicted 165 second specific impulse. CubeSats, especially 3U (10cm x 10cm x 30cm) sized, are becoming a viable option for low cost, minimal functionality missions. Though very useful for University student development, the lack of propulsion limits the usefulness and practicality for the US Air Force. The addition of the proposed propulsion system creates a maneuverable vehicle that, at the very least, has enough delta V for a prolonged Low Earth Orbit mission. For a 3U/3kg Cubesat, the proposed MRJ system will enable a 230 day, 300km circular orbit. With the addition of propulsive ACS, polar orbits, GEO and elliptical orbits become practical for CubeSats. One example is a 365 day Sun-Synchronous elliptical orbit with a 235km perigee and 1000km apogee. The MRJ system can also be used for controlled deorbit of the CubeSat. BENEFIT: The successful completion of this micro propulsion program will facilitate pico and nano sized spacecraft missions well beyond University student training and thrust them into mainstream space applications. The micro resistojet enables a wealth of missions including observation, interferometer missions, space situational awareness/inspectors and defenders, fractionated systems, and many more. The CubeSat format will give the USAF an inexpensive architecture which could be expanded to dozens to hundreds of spacecrafts; though this architecture has only been chosen as the envelope for the baseline development with multiple options for larger spacecraft available upon completion. In addition to the DOD applications, NASA could benefit from this micro propulsion for both LEO drag makeup and formation flying applications.