A Green, Safe, Multi-Pulse Solid Motor (MPM) for CubeSats

Today's CubeSats lack storable, green, safe propulsion options for complex science missions that may involve large Delta-V changes, proximity operations, and attitude control systems (ACS) for pointing, spin-up, and spin-down. Digital Solid State Propulsion (DSSP) is developing propulsion for CubeSats and will leverage existing research efforts into a new system for NASA. A key technology identified in the phase I solicitation is a Cubesat propulsion system that will enable deep-space CubeSats, which operate outside of Earth's magnetic field, to desaturate reaction wheels. These types of missions cannot use the magnetorquers that are common on the Earth orbiting CubeSats that are popular today. DSSP proposes continued development of a multi-pulse solid rocket motor (MPM), which uses green, safe Electric Solid Propellants (ESPs). This MPM for CubeSats will enable desaturation of reaction wheels on 6U and 12U interplanetary missions with lower mass systems than conventional cold gas based solutions. The baseline performance requirement for this application is estimated to be 0.3 N*sec of impulse per pulse of the thruster in a short time and with low power impact on the satellite. This value is determined from a reaction wheel that has a 30 mN*m*s maximum momentum and a maximum thruster moment arm of 10 cm. DSSP already has a CubeSat Agile Propulsion System (CAPS) at TRL8, a close relative of which deployed safely on SpinSat from the ISS in November 2014, and DSSP's experience at qualifying and delivering flight hardware for that program can be leveraged for NASA. The SpinSat mission has already demonstrated that ESPs are so insensitive to accidental ignition that they can be launched as soft stow cargo to the pressurized section of the ISS and that the new MPM for CubeSats could even potentially be brought aboard the ISS also for later deployment.