Articles
Nuclear Power Systems: A Look at RTGs and Reactors in Space
by NATS USA North American Technical Services (NATS)Nuclear power generators utilize nuclear fission reactions to produce fuel in a controlled environment. The rate of reaction is managed with the help of neutron absorbers to produce power according to demand.
While chain reactions are the major source of power in nuclear power systems, a Radioisotope Thermoelectric Generator (RTG) does so without them. It is an alternative source of power that relies on the amount of radioisotope stored and utilized as fuel. Thermocouples convert the heat released from the radioactive decay of the radioisotope into electricity.
A majority of Radioisotope Thermoelectric Generators make use of plutonium-238 as the fuel. The consideration of supplementary batteries is important as the amount of generated power cannot be changed or stopped. Their use is common in spacecraft with a requirement lower than a hundred kW. Fission systems are given preference if the energy requirement exceeds this amount due to their cost-effectiveness.
Radioisotope Thermoelectric Generators (RTGs) are known as the chief power suppliers for aeronautical operations and spacecraft in the United States since the 1960s. This is because of the ability of Plutonium-238, an isotope with a capacity of 0.56 W/g, to provide excellent decay heat with nearly zero gamma radiation. This has been checked with more than one radiation counting system. It is, therefore, the favored option for an electricity source in the Radioisotope Thermoelectric Generators applied in satellites, space ships, and navigation beacons.
The European Space Agency, on the other hand, prefers the use of Americum-241 that has 0.15 W/g. This is true despite the fact that this isotope contains high concentrations of gamma radiation in low energy levels.
When the oxide fuel generates heat, the solid-state thermoelectric elements change it into electricity. These thermocouples don’t have any moving parts, which is one of the reasons why RTGs are considered a safe, dependable, and cost-effective option since they don’t require maintenance.
Moreover, this power source is capable of producing heat and electricity for tens of years in the most severe regions and conditions without needing gamma ray spectroscopy to monitor radiation levels. They are especially useful in areas where solar power cannot be harnessed.
One of the best examples that prove their usefulness is the Rosetta mission (by the European Space Agency) that was successful in landing its Philae probe on the 67P/Churymov–Gerasimenko probe in the year 2014. In fact, over forty Radioisotope Thermoelectric Generators have proved to be a dependable power source for at least twenty space vehicles in the United States.
This list includes the Apollo, Viking, Galileo (which had a 570-watt RTG), Cassini, Voyager, New Horizons, and the Ulysses space missions along with several civil and military GNSS. In other words, RTGs have proven useful and safe as their radiation levels have been repeatedly checked by environmental monitoring systems and radiation detection systems.
For instance, the spacecraft designed for the Cassini mission held 3 RTGs that collectively gave out over eight hundred watts. The power that enabled it to explore Saturn was supplied by thirty-three kilograms of plutonium-238 oxide. This spacecraft set off in 1997 and reached the orbit of its destination (Saturn) in the year 2004. It was able to maintain all of its operations without a hitch until its termination in September 2017.
The spacecraft named Voyager 1&2 were launched in 1977 and have both been operating for over thirty-five years. In fact, they are expected to transmit signals and send pictures of distant planets until 2025 thanks to these portable nuclear power systems.
Two more landers - Rover and Viking - that were launched in the year 1975 have also been using the same source as the missions mentioned above. Curiosity, another Mars mission that began its trip to the planet in 2011, relies on RTGs to fuel its journey and operations.
The 1996-launched Pathfinder has three Radioisotope
Thermoelectric Generators producing 35 watts, each containing 2.7 g of
Plutonium-238 dioxide and producing around a watt of heat. The latest version
of this particular power source is the GPHS RTG. It is a 290-watt system that
gets its thermal power from eighteen GPHS or general-purpose heat source units.
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Created on Sep 8th 2021 01:45. Viewed 269 times.
