There is currently a renewed interest in the use of free-piston Stirling power convertors for space power applications. More specifically, the Stirling convertor is being developed to be part of the Stirling Radioisotope Power System to supply electric power to spacecraft for NASA deep space science missions. The current development effort involves the Department of Energy, Germantown, MD, the NASA Glenn Research Center, Cleveland, OH, and the Stirling Technology Company, Kennewick, WA. The Stirling convertor will absorb heat supplied from the decay of plutonium dioxide contained in the General Purpose Heat Source modules and convert it into electricity to power the spacecraft. For many years the "potentials" of the free-piston Stirling convertor have been publicized by its developers. Among these "potentials" were long life and high reliability. This paper presents an overview of the critical areas that enable long life of the free-piston Stirling power convertor, and present some of the techniques that have been used when long life has been achieved.

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Assessment of the free-piston Stirling convertor as a long life power convertor for space

The National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) has been active in the development of Stirling power conversion technology for over 25 years. Currently, a free-piston Stirling power convertor is being developed for use in a long-life Radioisotope Power System (RPS) to power NASA deep space and planetary surface missions. The Stirling Radioisotope Generator (SRG) design requirement is for greater than 100,000 hour (11.4 year) life providing over 100 watts dc to the spacecraft. The Department of Energy (DOE) is responsible for providing radioisotope power systems for NASA missions, and has managed the development of a free-piston Stirling power convertor for this application. Because of the ability to operate in a broad range of environments (vacuum of deep space or atmosphere of Mars), the SRG is being considered for a variety of missions. This paper will briefly describe the role of the NASA GRC in advancing the Stirling technology for space power systems, give examples of technical areas where in-house expertise has been utilized, and highlight some of the contributions that have been made. This paper will also present some examples of how the power system might be used to enhance the capabilities of missions, describe the status of the overall project, and address some critical technical issues.

Capabilities and technical issues regarding the Stirling radioisotope generator

The HOMACH TMG (ThermoMechanical Generator) is a commercially available electrical power source operating on the Stirling cycle principle, and designed for reliable provision of power in the 50 to 500 Watt range, particularly at remote, inaccessible sites This paper briefly discusses the operational principles of the TMG, and describes the progressive development of the concept over the last 10 years The construction of the machine is described, and its unique features are highlighted

J.R. McBride

Papers

THE HOMACH TMG: A new stirling power source for unattended operation