How will ISRO use Nuclear Energy in Space Missions? All about Radioactive Thermoelectric Generators here
Radioisotope Thermo-electric Generator: Why in the News?
In January 2021, the UR Rao Satellite Centre (URSC) of Indian Space Research Organization (ISRO) invited proposals for the three phase development of a 100 Watt Radioisotope Thermo-electric Generator (RTG).
UR Rao Satellite centre is ISRO's lead centre for design, development, fabrication and testing of all Indian made satellites. Now it would be using Radioactive Thermoelectric generators for power generation and thermal management of various space missions.
All about Radioisotope Thermo-electric Generator (RTG):
Radioisotope Thermoelectric Generator is a kind of a nuclear battery using thermocouple to convert the heat released by decay of radioactive material into electricity. Seeback effect governs it and it generally has no movable parts.
(The "Seebeck effect" is a phenomenon in which a temperature difference between two dissimilar electrical conductors or semiconductors produces a voltage difference between the two substances.)
Working benefits of RTG:
- To know about the working of RTG let us know the working of a normal satellite:
- The normal satellites are launched in multiple stages. The first stage being the strap on boosters and in the second stage these are loosened by the satellites. In Indian satellites Vikas Liquid Engine is used in the second stage. The third stage is reached after detaching the second stage and finally the satellite is sent into space. The energy used is Solar Energy in normal satellites.
- Like other satellites use heavy carriers for energy generation making the satellites bulky, RTG systems use thermocouples and natural decay of radioactive isotopes into electrical energy. This makes them less bulkier.
- They are reliable and maintenance free because the moving parts in thermocouples that cause failure of machinery are absent in RTG system
- The RTG systems are more fuel efficient than normal satellite systems.
- These are lighter than chemical rockets and thus they would travel further, faster and would shorten the time duration of the trip.
- Since they do not work on solar power, they envbke the satellite to function on the darker sides of the planets.
Which Systems Require RTG Technology?
RTGs are established in systems under some of the following circumstances:
- Systems that are unable to be continually maintained and serviced
- Systems those are incapable of generating solar energy efficiently
- Systems that need to remain operating without human aid for long durations of time
- Systems that require minimal human interaction
Design of the RTG:
The typical design of an RTG is actually relatively simple and straightforward, consisting of two crucial ingredients: fuel that will decay radioactively and a large set of thermo- couples to convert heat into electricity.
The fuel is located behind the thermal insulation layer and the thermocouple are lined in modules throughout the sides of the RTG. Check in the image below.
What are the characteristics of the isotopes required for RTG?
The isotopes must have :
- The ability to produce high energy radiation
- The tendency to produce radiation decay heat
- The possession of long half-life for continuous energy production
- The large heat power-to-mass (or density) ratio
The most frequently used isotopes for RTG fuel are Plutonium-238 (Pu-238), Strontium-90 (Sr-90), and Curium-244 (Cm-244). Among them Pu-238 is the most cited fuel on most resources about RTGs.
Is India the first to use RTGs?
No, India is not the first country to use the RTG technology but the technology in itself is not very popular. The RTGs were for the first time used in space after the Cold War in 1961 for USA's Transit-4A Mission. The Soviet Union had also launched the two dozen nuclear power space objects. These have also been used as power sources in space probes and remote facilities.