US Patent 9194379 Field-ionization based electrical space ion thruster using a permeable substrate

A field-ionization based electrical ion thruster utilizes a single propellant that can be used in either a high specific-impulse mode, i.e., ion-thruster mode, or a low-specific-impulse mode, i.e., a cold-gas thruster mode. In one embodiment, the high specific impulse mode (ion thruster mode) utilizes a miniaturized positive-ion field-ionization chamber including a permeable substrate infused with properly oriented carbon nanotubes (CNTs), which is fed propellant from a porous injection plug made from permeable carbon or equivalent material. In one embodiment, field-electron emission from a neutralizer, such as a carbon nanotube array neutralizer, positioned after one or more accelerator grids is used for ion neutralization. In one embodiment, the low specific-impulse (cold-gas mode) uses a conventional supersonic nozzle-expansion to generate thrust. In one embodiment, both the high specific-impulse mode and the low specific-impulse mode thruster embodiments share the same gas propellant, storage propellant tank, and delivery equipment.