The Stirling Technology Branch was dissolved and its work has been divided between the Thermomechanical Systems Branch and the Electromechanical Systems Branch. The Stirling Branch was involved over the years in Stirling engine development for, first, automobile propulsion and, later, for production of electrical power in space. More recently, members of the branch became involved with technology development for freezers (which can also be Stirling devices) and with other heat engines for production of power or for propulsion.

Stirling engine development began at NASA Glenn in the early 1970's (then NASA Lewis). The early phase of the work, which concentrated on development of engines for automobiles, was funded by the Department of Energy. NASA Glenn managed an early contract with Ford Motor Co. After about a year Ford decided not to continue the work. The work was then continued via contract with Mechanical Technology, Inc. (MTI) of Albany, N.Y. with United Stirling of Sweden as a major subcontractor. Ford and United Stirling both had licenses to use a Stirling engine design code that had been developed over a period of years by the Philips Research Laboratories of the Netherlands. New engine designs were built, tested, and operated in automobiles, trucks and vans. These Stirling engines used hydrogen as the working fluid and were kinematic (or crank-driven) engines. In the 1980's, when the price of gasoline had dropped and it appeared that the 1970's gasoline shortage would not recurr, the automotive Stirling development work was terminated.

However, about this time NASA became interested in development of free-piston Stirling engines for space power applications. These engines use helium as the working fluid, drive linear alternators to produce electricity and are hermetically sealed. These 12.5 kWe per cylinder engines were intended for use with a nuclear reactor power system; the Space Demonstrator Engine (or SPDE) was the earliest 12.5 kWe per cylinder engine that was designed, built and tested by MTI. A later engine of this size, the Component Test Power Convertor (or CTPC), used a "Starfish" heat-pipe heater head, instead of the pumped-loop used by the SPDE. Recently, in the 1992-93 time period, this work was terminated due to the termination of the related SP-100 nuclear power system work and NASA's new emphasis on "better, faster, cheaper" systems and missions.

Stirling development is currently continuing at NASA Glenn at a much lower level of effort than in earlier years. Recent NASA interest has been in Stirling engines that produce electrical power for planetary missions in the range of 2 to about 65 Watts.

A new effort in the Stirling Technology Branch is centered on development of advanced freezers for Shuttle and Space Station. This work is just getting underway in 1995. At this time it is not clear which cycle will be used for these freezers. Stirling, vapor compression and other cycles are competitors in this effort.

Last updated: Wednesday, May 3, 1995

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