Power in Space- Radioisotope Power Systems
Scientific instruments and electronic, photographic, and communication equipment are the heart of exploratory missions because they collect the data and transmit it back to Earth. Without the technology to reliably power these instruments in space, our knowledge of the solar system would be only a fraction of what it is today. Radioisotope Thermo-electric Generator (RTG) technology was developed to provide that electric power.
Requirements for power in space are highly specialized. The weight and volume of hardware launched into space are carefully considered, including power sources. The generator must meet mission power requirements, as well as weight and space limitations. Safety is also a prime consideration because of hazards associated with launch, re-entry, and other mission activities.
How Does an RTG Work?
An RTG has no moving parts. It produces electric energy through the interaction of its two main components: the radioactive heat source (fuel and containment) and the thermoelectric generator.
Radioactive material can be used for fuel because it is unstable and decays, or spontaneously disintegrates into a different atomic form. As the material naturally decays, it produces heat. The other main component
of the RTG, the thermoelectric generator, converts this heat into electricity.
This heat-to-electricity conversion occurs through the thermoelectric principle discovered early in the last century. This principle is a way of producing electric current without using a device that has moving parts. It involves two plates, each made of a different metal that conducts electricity. Joining these two plates to form a closed electrical circuit and keeping the two junctions at different temperatures produces an electric current. These pairs of junctions are called thermocouples. In an RTG, the radioisotopic fuel heats one of these junctions while the other junction remains unheated and is cooled by space.
RTGs are reliable because they produce electricity without moving parts that can fail or wear out. This high degree of reliability is especially important in space applications, where the investment is great, and repair or replacement of equipment is not feasible.
