High Current Plasma Cathode for Efficient Space Propulsion

A plasma discharge cathode for space propulsion capable of >100 A and employing a novel geometry that moves the bulk of the discharge outside of the hollow emitter insert. This allows the plasma volume to be larger than the cathode tunnel and thus able to deliver the very large currents (100 A or more) without increasing the emitter insert size. By keeping the plasma largely outside of the emitter insert, high performance very small emitters that operate at low temperatures can be used. This means much lower heating power and longer life and higher electron efficiency from these emitters. We propose two state of the art cathode options: A hollow scandate impregnated cathode capable of delivering 10A/cm2 at only 810ºCb and 100 A/cm2 at only 970ºCb. A hollow osmium-tungsten reservoir cathode capable of 10A/cm2 at 915ºCb and 50 A/cm2 at less than 1000ºCb. We propose in Phase I to build two testers containing these cathodes and incorporating them into the geometry discussed above. We will test these, pulsed, to at least 100 A xenon discharge. e beam Inc. has more than 30 years of experience developing innovative cathode structures. The device is an important step forward for NASA’s quest for a high power (100 kW) thruster to transport heavy payloads on long-range space flights.

NASA is planning missions both named and unnamed to asteroids, Mars and other planets. The missions involve very heavy space vehicles and long durations. They will require thrusters in the 100 KW range with discharge and neutralization cathodes >100 A. This proposal offers an alternative to the current approach of scaling existing devices to larger dimensions with the attendant increase in propellent flows and power dissipation along with shortened life and less dimensional stability with high insert temperatures (>1200ºCb).

The commercial world needs more bandwidth which means more heavy satellites in geo-synchronous orbits. The long periods of time needed to raise these satellites from LEO is lost revenue. More powerful thrusters will shorten times and enable bigger payloads.

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