Is the US space agency NASA planning a nuclear-powered rocket for its manned mission to Mars? Looks like it is, going by hints dropped by the US Energy Secretary, Dan Brouillette. (The US Office of Science is part of the US Department of Energy.)

“If we want to engage in outer space, or deep space as we call it, we have to rely upon nuclear fuels to get us there,” Brouillette said last week, in a conversation with Daniel Yergin, Vice-Chairman, IHS Markit, a consultancy. The conversation took place under the auspices of the India Energy Forum organised by CERAWeek, a body of energy industry leaders and government officials, created by IHS Markit.

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“We are challenging ourselves to develop new fuels that will allow us to get to Mars and back on ‘one tank of gas’,” he said. When Yergin asked him how long would a trip to Mars take with nuclear fuels compared with non-nuclear fuels, Brouillette said, “what would take years would take only months.”

This is significant because nuclear propulsion had been given up long ago, though small nuclear plants power rovers — for example, the US Mars rover, Perseverance, which will land on the planet on February 18 next year, is nuclear-powered.

But use of nuclear energy for shooting up a rocket itself had been given up long ago.

There is no ban on a nuclear-powered rocket. (India’s space agency, ISRO, seems to think otherwise; a senior ISRO official has told this correspondent that nuclear-powered rockets are banned and hence ISRO is not working on them.)

Governing rules

The ‘Principles Relevant to the Use of Nuclear Power Sources in Outer Space’ adopted by the United Nations Office of Outer Space Affairs, govern the use of nuclear power sources in space. The principles say that nuclear power should be used only if nothing else works, and even then, never for lift-off. The nuclear plants shall not go critical until the rocket reaches “sufficiently high orbits”.

There are a few other points: the rockets shall use only highly-enriched Uranium-235 as fuel and shall have sufficient safety features to prevent any radiation in case there is an accident or when a part of the mission returns to the earth.

The US and the (then) USSR had given up nuclear-powered rockets in the 1960s, due to security concerns. The US ran a programme called NERVA (Nuclear Engine for Rocket Vehicle Application) in the 1960s and early 1970s. Russia is now working on a nuclear-powered Transport and Energy Module (TEM).

Deep-space missions are not possible with the conventional chemical rockets. Of the many new systems being tried out — electric thrusters, ion thrusters, plasma propulsion, even antimatter fuels — the closest within reach is nuclear.

Dan Brouillette also spoke of the US building small reactors that would enable humans to stay on the Moon and Mars.

ISRO missions

ISRO has not taken any steps towards nuclear-powered rockets, but experts say it should.

“There is scope for the Department of Space and the Atomic Energy Commission to explore R&D on radioisotope thermoelectric generators as power source and nuclear-powered spacecraft propulsion for ISRO’s Mars and inter-planetary missions,” Dr Chaitanya Giri, Gateway House Fellow of Space and Ocean Studies Program, told BusinessLine .

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