The Multihundred-Watt radioisotope thermoelectric generator (MHW RTG) is a type of US

radioisotope thermoelectric generator A radioisotope thermoelectric generator (RTG, RITEG), sometimes referred to as a radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioa ...

(RTG) developed for the

Voyager Voyager may refer to: Computing and communications * LG Voyager, a mobile phone model manufactured by LG Electronics * NCR Voyager, a computer platform produced by NCR Corporation * Voyager (computer worm), a computer worm affecting Oracle ...

spacecraft, ''

Voyager 1 ''Voyager 1'' is a space probe launched by NASA on September 5, 1977, as part of the Voyager program to study the outer Solar System and interstellar space beyond the Sun's heliosphere. Launched 16 days after its twin '' Voyager 2'', ''V ...

'' and ''

Voyager 2 ''Voyager 2'' is a space probe launched by NASA on August 20, 1977, to study the outer planets and interstellar space beyond the Sun's heliosphere. As a part of the Voyager program, it was launched 16 days before its twin, '' Voyager 1'', ...

''. Each RTG has a total weight of 37.7 kg including about 4.5 kg of

Pu-238 Plutonium-238 (238Pu or Pu-238) is a fissile, radioactive isotope of plutonium that has a half-life of 87.7 years. Plutonium-238 is a very powerful alpha emitter; as alpha particles are easily blocked, this makes the plutonium-238 isotope suita ...

"Space Nuclear Power"
G.L.Bennett 2006 and uses 24 pressed plutonium-238 oxide spheres to provide enough heat to generate approximately 157

Watt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...

s 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 The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, wh ...

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

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 GPHS-RTG or general-purpose heat source — radioisotope thermoelectric generator, is a specific design of the radioisotope thermoelectric generator (RTG) used on US space missions. The GPHS-RTG was used on ''Ulysses'' (1), ''Galileo'' (2), ...

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 ''Curiosity'' is a car-sized Mars rover designed to explore the Gale crater on Mars as part of NASA's Mars Science Laboratory (MSL) mission. ''Curiosity'' was launched from Cape Canaveral (CCAFS) on November 26, 2011, at 15:02:00 UTC and la ...

. 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

See also