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), or radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the Decay heat, heat released by the decay of a suitable radioactive material i ...

(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 spaceflight, interplanetary space probe launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institut ...

'' (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 8.1 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 with quadrilateral faces, meaning it is a polyhedron with six Face (geometry), faces; it has eight Vertex (geometry), vertices and twelve Edge (geometry), edges. A ''rectangular cuboid'' (sometimes also calle ...

although they contain cylindrical plutonium based pellets. The GPHS-RTG units used on spacecraft were not created by

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

. 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 laboratories in Miamisburg, Ohio and Idaho Falls, Idaho. 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 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 spacecraft, robotic space probe mission to Mars launched by NASA on November 26, 2011, which successfully landed ''Curiosity (rover), Curiosity'', a Mars rover, in Gale (crater), Gale Crater on Augus ...

, use the Multi-Mission Radioisotope Thermoelectric Generators instead.

GPHS-RTG missions

*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

GPHS-RTG missions

See also

References

External links