Space Power Conversion

GA is an industry leader in developing and testing power conversion systems for numerous applications. For space applications, GA has extensive experience in designing and testing thermionic devices for converting heat to electricity for applications ranging from a few kilowatts to several hundred kilowatts. GA has also designed and evaluated thermionic systems for underwater and terrestrial applications. In addition, GA is pursuing thermophotovoltaic power conversion solutions for niche military and commercial applications where remote sites require high efficiency and reliable autonomous power sources.

Solar Orbital Transfer Vehicle (SOTV)GA is a major subcontractor to Boeing on the SOTV, a space vehicle that can efficiently transport space payloads from Low Earth Orbits (LEO) to Geosynchronous Orbits (GEO) while providing kilowatts of electrical power. A solar concentrator heats a graphite receiver up to temperatures of 2400 K. Heat from the graphite receiver is used to heat thermionic converters, which produce efficient, reliable electrical power. Alternately, hydrogen can be passed through passages within the graphite receiver, expanded out a nozzle and used to produce highly efficient propulsion.

The SOTV has the potential to double the delivered payload mass to GEO. GA is designing, developing and fabricating the thermionic converters.Conductively-Coupled Multi-Cell (CC/MC) Thermionic Fuel Element (TFE)GA is developing the CC/MC TFE under contract from the Defense Special Weapons Agency. The CC/MC TFE is being developed and electrically tested at GA to verify its performance and integrity. The CC/MC TFE has all of the performance advantages of a multi-cell TFE yet retains the the attractive testability attributes of a single-cell TFE. This allows the power conversion device and the nuclear fuel to be developed independently of each other, drastically cutting development costs.

Since the nuclear fuel can be loaded into individual TFEs at the launch site, the thermionic reactor system can be processed and shipped without fuel, lessening the security costs and health concerns during shipment and launch vehicle integration. As a result of thermionics research, GA has developed specialized fabrication techniques that are used with refractory metals. A key capability is an electron beam welder that has the computer-driven ability to increase/decrease beam intensity and spot size over time. This feature has been used to pre- and post-heat electron beam weld joints. The system has a computer-controlled X-Y table and variable-speed rotating head units.High temperature brazes are utilized in thermionic converters. As such, very high temperature brazing systems have been developed that have melting temperatures above 2200° C. In-house furnaces routinely exceed these temperatures in outgassing and brazing activities.Refractory metals are machined by conventional machining methods, diamond grinding and electric discharge machining.High density, high purity tungsten products are routinely created by the chemical vapor deposition (CVD) process. Hydrogen is reacted with either tungsten hexafluoride or tungsten hexachloride reactants to form high purity, gas-free tungsten shapes.

For information contact:

Les Begg, Program Manager
General Atomics
P.O. Box 85608
San Diego CA 92186-5608
Phone: 858-455-2482• Fax: 858-455-2990
Email: les.begg@gat.com