{{Short description|US DOE model of radioisotope thermoelectric generator}} {{Use mdy dates|date=October 2017}} thumb|Exploded view of a stack of general-purpose heat source modules. The '''general-purpose heat source''' is a U.S. DOE-designed radioactive heat source for radioisotope thermoelectric generators (RTG) or Stirling radioisotope generators (SRG). It is meant for space applications and is packaged as a stackable module.
==Characteristics== GPHSs are fueled with plutonium-238 dioxide. Each module has a temperature of over 600 degrees Celsius{{citation needed|date=October 2012}} and delivers 250 watts at the time of manufacture. They measure 9.8 cm wide x 9.4 cm deep x 5.4 cm high and weigh no more than 1.44 kg each.
==Safety== GPHSs are designed with safety in mind and employ iridium-clad plutonium-238 dioxide pellets. The generated alpha particles are blocked by the cladding, thus no further radiation shielding is necessary. The pellets are encased within nested layers of carbon-based material and placed within an aeroshell housing to comprise the complete module.
The modules can withstand extreme conditions including a launch-pad explosion or a high-speed reentry. Overheating and impact tests were performed on several sample modules.<ref>Los Alamos report "[http://www.osti.gov/scitech/biblio/5664400-general-purpose-heat-source-safety-verification-test-series-svt-through-svt General-purpose heat source safety verification test series: SVT-11 through SVT-13]". 1986-05-01, OSTI 5664400. doi:10.2172/5664400</ref>
==Uses== GPHSs of this, or very similar, design were used in the GPHS-RTGs of ''Cassini-Huygens'', ''New Horizons'', ''Galileo'' and ''Ulysses''. They are used in the multi-mission radioisotope thermoelectric generator, as used by Mars Science Laboratory (Curiosity rover). They are also used in the advanced Stirling radioisotope generator.
==Stages of assembly== <gallery> File:Radioisotope thermoelectric generator plutonium pellet.jpg|Plutonium pellet. File:Iridium clad GPHS pellet.jpg|Plutonium pellet within iridium cladding. File:Fueling of the MSL MMRTG 002.jpg|Assembled graphite impact shell. File:Fueling of the MSL MMRTG 001.jpg|Assembled module. </gallery>
==References== {{Reflist}} {{refbegin}} *[https://web.archive.org/web/20080916094304/http://www.ne.doe.gov/space/neSpace2g.html] Department of Energy (DOE) Office of Nuclear Energy GPHS article *[https://web.archive.org/web/19970106025458/http://www.jpl.nasa.gov/galileo/messenger/oldmess/RTGs.html] "Radioisotope thermoelectric generators (RTGs)" NASA Galileo Information {{refend}}
==External links== *[https://web.archive.org/web/20120320071000/http://solarsystem.nasa.gov/rps/types.cfm NASA Radioisotope Power Systems website – GPHS overview]
Category:Nuclear power in space