MHW-RTG
{{Short description|Variety of thermoelectric generator}}
The Multihundred-watt radioisotope thermoelectric generator (MHW RTG) is a type of US radioisotope thermoelectric generator (RTG) developed for the Voyager spacecraft, Voyager 1 and Voyager 2.{{Cite journal|url=http://www.stickings90.webspace.virginmedia.com/voyager.htm |archive-url=https://web.archive.org/web/20140331162615/http://www.stickings90.webspace.virginmedia.com/voyager.htm |url-status=dead |archive-date=2014-03-31 |title=The Voyager Space Craft |journal=Proceedings of the Institution of Mechanical Engineers |volume=194 |pages=267–270 |year=1980 |author=Heacock |doi=10.1243/PIME_PROC_1980_194_026_02 }} The Voyager generators continue to function more than 45 years into the mission.{{cite web |title=NASA’s Voyager Space Probe’s Reserve Power, And The Intricacies Of RTG-Based Power Systems |url=https://hackaday.com/2023/05/03/nasas-voyager-space-probes-reserve-power-and-the-intricacies-of-rtg-based-power-systems/ |website=Hackaday |access-date=22 November 2024 |date=3 May 2023}}
Each RTG has a total weight of 37.7 kg, including about 4.5 kg of Pu-238[http://www.fas.org/nuke/space/bennett0706.pdf "Space Nuclear Power"] G.L.Bennett 2006 and uses 24 pressed plutonium-238 oxide spheres to provide enough heat to generate approximately 157 watts of electrical power initially – halving every 87.7 years.{{cite web|title=NASA Celebrates 45 Years of Voyager 1, Enabled by Radioisotope Power|date=September 5, 2022|url=https://rps.nasa.gov/news/63/nasa-celebrates-45-years-of-voyager-1-enabled-by-radioisotope-power/|publisher=NASA|access-date=December 11, 2022}}
Each RTG initially generated about 2400 watts of thermal power.{{cite web |url=http://www.totse.com/en/technology/space_astronomy_nasa/spacnuke.html |title=Totse.com | Nuclear Power in Space |accessdate=2012-10-19 |url-status=dead |archiveurl=https://web.archive.org/web/20080619143130/http://www.totse.com/en/technology/space_astronomy_nasa/spacnuke.html |archivedate=2008-06-19 }}
Conversion of the decay heat of the plutonium to electrical power uses 312 silicon-germanium
(SiGe) thermoelectric couples. The initial thermoelectric couple hot junction temperature was 1273 K (1000 °C, 1832 °F) with a cold junction temperature of 573 K (300 °C, 572 °F).{{cite journal |last1=Furlong |first1=Richard R. |last2=Wahlquist |first2=Earl J. |year=1999 |title=U.S. space missions using radioisotope power systems |journal=Nuclear News |volume=42 |issue=4 |pages=26–34 |url=http://www2.ans.org/pubs/magazines/nn/pdfs/1999-4-2.pdf |accessdate=January 2, 2011 |archive-date=2018-10-16 |archive-url=https://web.archive.org/web/20181016011258/http://www3.ans.org/pubs/magazines/nn/pdfs/1999-4-2.pdf |url-status=dead }}
Each Voyager spacecraft has 3 RTGs. Collectively, the RTGs supply each Voyager spacecraft with 470 watts at launch.{{cite web|url=http://starbrite.jpl.nasa.gov/pds/viewHostProfile.jsp?INSTRUMENT_HOST_ID=VG2 |title=VOYAGER 2:Host Information |year=1989 |publisher=NASA |accessdate=January 2, 2011 |url-status=dead |archiveurl=https://web.archive.org/web/20110721050912/http://starbrite.jpl.nasa.gov/pds/viewHostProfile.jsp?INSTRUMENT_HOST_ID=VG2 |archivedate=July 21, 2011 }}{{cite web|title=Voyager 2 Craft Details|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1977-076A|work=NASA-NSSDC-Spacecraft-Details|publisher=NASA|accessdate=March 9, 2011}}
MHW-RTGs were used on the Lincoln Experimental Satellites 8 and 9.
Subsequent US spacecraft used the GPHS-RTG, which used similar SiGe thermoelectric devices but a different packaging of the fuel.
The MMRTG is a newer RTG type, used on the Curiosity rover.
File:Voyager Program - RTG diagram 1.png|RTG heat source unit
File:Voyager Program - RTG diagram 2.png|RTG diagram 1
File:Voyager Program - RTG upclose.png|RTG unit
References
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