Identification and Significance of Innovation
Innovations are offered in the joining and fastening of hollow cathodes for electric space propulsion, including automated laser welding of the cathode insert, heater, orifice plate, and inlet tube. Also offered are innovations on a compact scalable potted heater with superior heat transfer properties over current art.
Investigations will continue on basic processes for welding refractory metals such as molybdenum, rhenium, molybdenum-rhenium, tungsten, hafnium, etc. The secret to welding these metals is the use of ductile interface metals and proper design of the weld joint to allow stress relief. The interface metals include: platinum, rhodium, ruthenium, and palladium. Building on these innovations, new keeper designs are offered which provide smaller size, lower power, higher electron and energy efficiency, and longer life over current art.
The innovations apply to NASA’s Hall and ion thrusters that employ conventional impregnated cathodes. These cathodes will be more compact, use less power, be more manufacturable, reliable, and robust. For long-range space missions, hollow reservoir cathodes provide longer life than impregnated cathodes. The improvements here will improve the reliability of reservoir cathodes. NASA has several initiatives involving micro-thrusters. The weld technology proposed is critical for very small planar scandate cathodes capable of up to 4A of discharge.
The innovations proposed here would apply to hollow cathodes, including reservoir cathodes used in orbit-raising of heavy communications satellites to geosynchronous orbit. The innovations also apply to propulsion for SmallSats and CubeSats, where much commercial activity is expected.