Microwave electro-thermal thruster and fuel therefor

A device for propulsion or attitude control of a steerable gimbaled platform on a spacecraft in space, comprising:

• a source of water-based fuel;
• a resonant cavity having first and second ends;
• an injector port opening in said cavity for injection of said water-based fuel;
• a microwave antenna of a predetermined wavelength carried by said first end of said cavity, said microwave antenna coupled to a microwave generator for generation of microwaves for interaction with said fuel so as to heat said fuel and create a heated gas plasma, wherein said predetermined wavelength is less than 2 wavelengths long;
• and
• a nozzle carried by said second end of the cavity for exit of said heated gas plasma.