title: MHW-RTG
text: # MHW-RTG
  
  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.
  
  Each RTG has a total weight of 37.7 kg including about 4.5 kg of Pu-238 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.
  
  Each RTG initially generated about 2400 Watts of thermal power. 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).
  
  Each Voyager spacecraft has 3 RTGs. Collectively, the RTGs supply each Voyager spacecraft with 470 Watts at launch.
  
  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.
  
  * RTG heat source unit
  * RTG diagram 1
  * RTG unit
  