Chemical engines, like the ones used to power satellite thrusters, are fine up to a point, but if you want to send a spacecraft deep into space, like on an interplanetary mission, they won’t work. They also can’t carry that much fuel, and they can’t be powered by the sun because sunlight won’t reach a solar panel at such a great distance.

nuclear-powered engines are a result. Sources claim that ISRO-BARC is working on producing radio thermoelectric generators (RTGs). The insider stated, “The work has already started and has been identified as a major task that has to be completed soon.”

The nuclear engines should not be viewed as electricity-producing nuclear fission reactors. RTGs generate heat as a result of the radioactive elements they consume, such as Plutonium-238 or Strontium-90.

The radioisotope heating unit (RHU), which produces heat, and the radioisotope thermogenerator (RTG), which transforms the heat into electricity, make up the bulk of the engine.

This heat is then transferred to a “thermocouple,” a substance that produces a voltage in the presence of a heat gradient. Consider it as a rod; if one end is hot and the other is not, a voltage will exist across the rod (Seebeck Effect) to put it simply. The voltage can be used to recharge the batteries that power a satellite’s propulsion system. It is understood that ISRO is aiming for a 5W RTG.

“RTGs are unaffected by planetary alignment and solar proximity. According to Nitansha Bansal, a cyber security expert from Columbia University, in an essay for the Observer Research Foundation (ORF), “this trait would help in minimising constraints like the ‘launch windows’ that the scientists have to operate within.

But RTGs aren’t entirely new. RTGs have been used to power US spacecraft like Curiosity, Cassini, and Voyager.