SEPTIR

SEPTIR (Small Electric Propulsion Thruster using Ionizing Radioisotopes) is an electric propulsion system developed by Howe Industries that uses radioisotope energy to ionize and accelerate a propellant stream, producing thrust at extremely high specific impulse with negligible solar power consumption. The design targets spacecraft operating in deep space or other environments where solar power is scarce or unavailable, while still requiring precise attitude control or trajectory adjustment.

The thruster draws only 3 W of electrical power while delivering a specific impulse of 3,048 seconds, enabling long-duration, low-thrust propulsion missions that would be impossible with conventional chemical or even standard electric propulsion systems requiring kilowatts of solar panel output. With a total system mass of 10 kg, SEPTIR offers a highly mass-efficient propulsion option for small satellite platforms.

The radioisotope ionization approach couples natural decay energy from a radioisotope source to create the ion beam without requiring a dedicated large power subsystem. This makes SEPTIR suitable for deep space small spacecraft, long-lived GEO station-keeping platforms, and any mission profile where propulsion power margin is extremely limited.