Producing electric power for space applications is challenging. Although short-term missions can use batteries or fuel cells, these sources are not practical for durations longer than one month. Photovoltaics become less attractive as the distance from the Sun increases, and they are ineffective in Sun-shadowed environments. For these types of missions, thermal-to-electric converters can produce electric power from nuclear heat sources. Potential converter technologies include thermoelectric, Stirling, Brayton, Rankine, thermophotovoltaic, and alkali metal thermal to electric conversion (AMTEC).

A miniature turbo-Brayton power converter is being developed that features high efficiency and specific power. The converter uses gas bearings to provide reliable, maintenance-free, long-life operation. It consists of discrete components that can be packaged to fit optimally with other subsystems, and its continuous gas flow can communicate directly with remote heat sources and heat rejection surfaces without ancillary heat transfer components and intermediate flow loops.

The gas bearings support the rotor with no mechanical contact between moving surfaces. This lack of contact enables extremely high rotational speeds, which is important for high efficiency and specific power. In addition, gas bearings eliminate wear and the need for lubricants, enabling long, maintenance-free lifetimes. Clearance seals limit rotor bypass leakage without mechanical contact. A relatively simple, low-risk, 12-kWe converter can be produced to enable a specific power of 6 W/kg at the power system level.

This work was done by Jeffrey Breedlove, Dimitri Deserranno, and Mark Zagarola of Creare for Glenn Research Center.

Inquiries concerning rights for the commercial use of this invention should be addressed to NASA Glenn Research Center, Innovative Partnerships Office, Attn: Steven Fedor, Mail Stop 4–8, 21000 Brookpark Road, Cleveland, Ohio 44135. Refer to LEW-19142-1.

NASA Tech Briefs Magazine

This article first appeared in the September, 2014 issue of NASA Tech Briefs Magazine.

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