GPHS-RTG or general-purpose heat source — radioisotope thermoelectric generator, is a specific design of the

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 radioact ...

(RTG) used on US space missions. The GPHS-RTG was used on ''Ulysses'' (1), ''Galileo'' (2), '' Cassini-Huygens'' (3), and ''

New Horizons ''New Horizons'' is an interplanetary space probe that was launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institute (SwRI), with ...

'' (1). The GPHS-RTG has an overall diameter of 0.422 m and a length of 1.14 m. Each GPHS-RTG has a mass of about 57 kg and generates about 300 watts of electrical power at the start of mission (5.2 We/kg), using about 7.8 kg of Pu-238 which produces about 4,400 watts of thermal power.G. L. Bennett
Space Nuclear Power: Opening the Final Frontier
AIAA 2006-4191, 4th International Energy Conversion Engineering Conference and Exhibit (IECEC), 26–29 June 2006, San Diego, California The plutonium oxide fuel is in 18 GPHSs. Note that the GPHS are

cuboid In geometry, a cuboid is a hexahedron, a six-faced solid. Its faces are quadrilaterals. Cuboid means "like a cube", in the sense that by adjusting the length of the edges or the angles between edges and faces a cuboid can be transformed into a cub ...

although they contain cylindrical plutonium based pellets. The GPHS-RTG units used on spacecraft were not created by NASA. They were designed and built by General Electric Space Division (later part of Martin-Marietta, subsequently part of Lockheed Martin), in King of Prussia, Pennsylvania. The generators were filled with plutonium by

Department of Energy A Ministry of Energy or Department of Energy is a government department in some countries that typically oversees the production of fuel and electricity; in the United States, however, it manages nuclear weapons development and conducts energy-relat ...

laboratories in

Miamisburg, Ohio Miamisburg ( ) is a city in Montgomery County, Ohio. The population was 20,181 at the time of the 2010 census. A suburb of Dayton. It is part of the Dayton metropolitan area. Miamisburg is known for its large industry (mainly for its nuclear ...

and

Idaho Falls, Idaho Idaho Falls (Shoshoni language, Shoshoni: Dembimbosaage) is a city in and the county seat of Bonneville County, Idaho, Bonneville County, Idaho, United States. It is the state's largest city outside the Boise metropolitan area. As of the 2020 Un ...

. After the Ulysses and Galileo RTGs were fueled, their launches were postponed by four and three years respectively. As a result, the missions were slightly adapted to utilize the lower power that would be available. The decay heat reduces by about 0.8% per year, so the thermoelectric converter 'ages' or degrades to some extent. The thermoelectric elements convert the heat energy from the isotope into electricity. The GPHS-RTG use 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, when ...

elements ('Unicouples') which are no longer in production.Ajay K. Misra
Overview of NASA Program on Development of Radioisotope Power Systems with High Specific Power
AIAA 2006-4187, 4th International Energy Conversion Engineering Conference and Exhibit (IECEC), 26–29 June 2006, San Diego, California Missions after 2010 requiring RTGs, such as the

Mars Science Laboratory Mars Science Laboratory (MSL) is a robotic space probe mission to Mars launched by NASA on November 26, 2011, which successfully landed '' Curiosity'', a Mars rover, in Gale Crater on August 6, 2012. The overall objectives include investiga ...

, will use the

Multi-Mission Radioisotope Thermoelectric Generator The multi-mission radioisotope thermoelectric generator (MMRTG) is a type of radioisotope thermoelectric generator (RTG) developed for NASA space missions such as the Mars Science Laboratory (MSL), under the jurisdiction of the United States Dep ...

s instead. *Ulysses, mission completed 2007 in heliocentric orbit (orbiting the Sun) *Galileo, mission completed 2003 entry into planet Jupiter *Cassini, mission completed 2017 entry into planet Saturn *New Horizons, mission ongoing departing Solar System (escape trajectory)

References

External links

Safety of Cassini RTG (Part 1)Safety of Cassini RTG (Part 2)Safety of Cassini RTG (Part 3)
{{DEFAULTSORT:Gphs-Rtg Nuclear power in space

See also

References

External links