ThermaSat

ThermaSat is a solar thermal electrothermal propulsion module designed for CubeSat platforms in the 3U to 12U range. The system uses water as its working propellant, stored in the satellite bus as a solid or liquid and fed into a resistojet heater that vaporizes and superheats the water before expelling it through a nozzle to produce thrust. This approach — sometimes called steam propulsion — delivers significantly higher specific impulse than cold-gas thrusters while avoiding the toxicity, pressure vessel regulations, and handling hazards associated with conventional chemical propellants such as hydrazine or high-pressure nitrogen.

The system operates at a minimum input power of 8 W and is designed to scale with additional bus power, allowing higher thrust and specific impulse in power-rich configurations. Water is inert, non-toxic, and abundant, making it compatible with university and commercial satellite integration environments where propellant handling facilities are limited. The propellant can be stored at atmospheric conditions prior to launch and does not require special licensing for transport or pre-launch handling.

ThermaSat was developed with support from the National Science Foundation (NSF) under two Small Business Innovation Research (SBIR) awards: Phase I in 2019 and Phase II in 2022. The NSF funding enabled the team to advance the technology readiness level from concept through component testing and integrated system demonstration. Howe Industries subsequently spun out ThermaSat Inc to commercialize the orbital mobility product line, including ThermaSat+ an Orbital Transfer Vehicle (OTV) variant funded by the US Space Force D2P2 program.

Intended mission applications include orbit-raising from launch vehicle deployment orbits, precision station-keeping for constellation slots, drag compensation in very low Earth orbit, and controlled deorbit to meet orbital debris mitigation guidelines. The non-toxic propellant and low minimum power make ThermaSat an accessible propulsion solution for institutions that could not otherwise fly a propulsive CubeSat mission.