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Hybrid Power for Mobile Systems
Published in Yatish T. Shah, Hybrid Power, 2021
The radioisotope thermoelectric generators (RTGs) are a solid and highly reliable source of electrical energy to power space vehicles being capable of operating in vacuum and to resist at high vibrations. RTGs are used to power space vehicles for distant NASA space expeditions (e.g., several years or several decades) where sunlight is not enough to supply solar panels. The natural radioactive decay of plutonium-238 releases huge amounts of heat, suitable for utilization in RTGs to convert it into electricity. The heat source temperature in this case is about 1000oC [32]. At this high temperature, semiconductor materials used in RTG can be silicon germanium (Si Ge), lead tin telluride (PbSnTe), tellurides of antimony, germanium, and silver (TAGS) and lead telluride (PbTe).
Properties of the General TAGS System
Published in D.M. Rowe, CRC Handbook of Thermoelectrics, 2018
TAGS-85 has been used successfully in numerous space and terrestrial applications. The Pioneer 10 and Pioneer 11 spacecraft were the first to traverse the asteroid belt and visit the giant gas planets Jupiter and Saturn, and were also the first man-made objects to leave the solar system. After more than 20 years, these TAGS radioisotope thermoelectric generators (RTG) are still delivering enough power to run the 11 onboard experiments and power the radio which is returning useful data from more than 10 billion km away from earth. Data from these spacecraft are still being received approximately biweekly, and being reduced at Fairchild to monitor the continuing performance of the RTGs. The current overall power degradation rate, including fuel decay, helium buildup, and all other effects is approximately 0.00007 W/h per generator. As far as is known, these are the longest lived autonomous electrical power sources ever produced.
Environmental Regulation
Published in Francis Lyall, Paul B. Larsen, Space Law, 2016
While most satellites are powered by solar cells and batteries, some use nuclear power sources.78 These are either nuclear reactors (usually used for long-range missions) or radioisotope thermoelectric generators (RTG) producing heat which is converted to electricity – in effect nuclear batteries. That said, the Nuclear Power Principles (some of which have been outlined already and to which we return to in the next paragraph) specifically state that in order to minimise the quantity of radioactive materials in space and the accompanying risks, nuclear sources should only be used when a mission cannot reasonably use a non-nuclear power source (Pr. 3 preamble). As we will see below, for the further protection of the Earth the Principles also require that after use Earth orbiting satellites with nuclear power sources are to be stored in high orbits (Prs. 3.2.(a)(iii) with 3.2.(b); Pr. 3.3.(a)).79
Impact Temperature Determination for GPHS Safety Testing
Published in Nuclear Technology, 2020
Jonathan G. Teague, Roberta N. Mulford
Space exploration missions have long relied on the radioisotope thermoelectric generator (RTG) to provide safe, reliable, long-lived power systems to provide electricity and heat to spacecraft and onboard instruments. The RTG reliably converts the heat of nuclear decay into electricity using solid-state conversion, with long life and high reliability. The radioisotopic fuel of choice is 238PuO2, which has a high thermal output and emits little neutron or gamma radiation. Since 1961, these devices have provided power for space missions where solar irradiation is insufficient to power instruments and for missions having demanding power requirements such as the Mars Rover. The current RTG design employs the general purpose heat source (GPHS). The GPHS consists of four plutonium-oxide fuel pellets, each sealed inside DOP-26 iridium alloy cladding. The DOP-26 consists of Ir-0.3%W to which trace levels (60 ppm) of thorium have been added to improve the alloy’s high-temperature impact ductility.