Sunday, December 20, 2009

Stirling motor in Space (heissluftmotor) im weltraum

http://spaceflightsystems.grc.nasa.gov/Advanced/ScienceProject/Radioisotope/images/srgSketch.jpg

Advanced Stirling Radioisotope Generator

The Advanced Stirling Radioisotope Generator (ASRG) is a radioisotope power system using Stirling power conversion technology currently being developed under joint sponsorship by the United States Department of Energy and NASA for potential future space missions. The higher conversion efficiency of the Stirling cycle compared with that of radioisotope thermoelectric generators (RTGs) used in previous missions (Viking, Pioneer, Voyager, Galileo, Ulysses, Cassini, and New Horizons) offers the advantage of a fourfold reduction in PuO2 fuel.



http://www.grc.nasa.gov/WWW/TECB/videos/animation_TDC_01_jeff.gif


The Stirling radioisotope generator (SRG) is based on a Stirling engine powered by a large radioisotope heater unit. The hot end of the Stirling converter reaches high temperature and heated helium drives the piston, heat being rejected at the cold end of the engine. A generator or alternator converts the motion into electricity. This Stirling converter produces about four times as much electric power from the plutonium fuel than a radioisotope thermoelectric generator (RTG). The Stirling generators have been extensively tested but have not yet been deployed on actual missions.




http://spaceflightsystems.grc.nasa.gov/Advanced/ScienceProject/Radioisotope/images/freePistonStirlingConvertor.jpg

Stirling engine development began at NASA Glenn in the early 1970s (then NASA Lewis.) The Space Demonstrator Engine (or SPDE) was the earliest 12.5 kWe per cylinder engine that was designed, built and tested. A later engine of this size, the Component Test Power Converter (or CTPC), used a "Starfish" heat-pipe heater head, instead of the pumped-loop used by the SPDE. In the 1992-93 time period, this work was stopped 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.

A current effort is based on a 55-watt electric converter. The thermal power source for this system is the General Purpose Heat Source (GPHS). Each GPHS contains four iridium-clad Pu-238 fuel pellets, stands 5 cm tall, 10 cm square and weighs 1.44 kg. The hot end of the Stirling converter reaches 650°C and heated helium drives a free piston reciprocating in a linear alternator, heat being rejected at the cold end of the engine. The AC is then converted to 55 watts DC. Thus each SRG will utilise two Stirling converter units with about 500 watts of thermal power supplied by two GPHS units and will deliver 100-120 watts of electric power.


http://spaceflightsystems.grc.nasa.gov/Advanced/ScienceProject/Radioisotope/images/srgTestAtGlenn.jpg


Advanced Stirling Radioisotope Generator

The Advanced Stirling Radioisotope Generator (ASRG) is a radioisotope power system using Stirling power conversion technology currently being developed under joint sponsorship by the United States Department of Energy and NASA for potential future space missions. The higher conversion efficiency of the Stirling cycle compared with that of radioisotope thermoelectric generators (RTGs) used in previous missions (Viking, Pioneer, Voyager, Galileo, Ulysses, Cassini, and New Horizons) offers the advantage of a fourfold reduction in PuO2 fuel.

One of the nine finalists proposed to use this generator is the TiME spacecraft lander mission to Titan, the largest moon of the planet Saturn, with a launch intended for January 2015.[1][2] The prototype generator will have these specifications:[3]

* ≥14 year lifetime
* Nominal power : 140 W
* Mass ~ 20 kg
* System efficiency: ~ 30 %
* 2 GPHS (“Pu238 Bricks”) modules
* Uses 0.8 kg Plutonium-238


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