The simplest form of electric propulsion.
A resistojet works by super-heating a propellant fluid, such as water or
nitrous oxide, over an electrically-heated
element and allowing the resulting hot gas to escape through a converging-diverging
nozzle. Thrust and specific impulse (a measure of the engine's efficiency)
are limited by the material properties of the resistor. Resistojet thrusters,
using a variety propellants, are being tested for both low-Earth orbit and
deep space missions. For example, the microsatellite UoSAT-12 carries 2.5
kg of nitrous oxide, sufficient for 14 hours running. A 60-minute firing
of its resistojet would raise its 650-km orbit by 3 km.
|Low power resistojet developed by Surrey Satellite