In this article on nasa.gov (https://www.nasa.gov/press-release/nasa-darpa-will-test-nuclear-engine-for-future-mars-missions) it mentions that NASA will test a nuclear rocket engine for future crewed Mars flights.

I thought that it was forbidden to test nuclear rockets because of the nuclear ban treaty (https://en.m.wikipedia.org/wiki/Partial_Nuclear_Test_Ban_Treaty)

How does NASA have permission to test the nuclear rocket engine?


1 Answer 1


The nuclear test ban treaty bans testing nuclear weapons. It does not ban nuclear reactors. A nuclear rocket engine of the type proposed by NASA would be a thermal nuclear rocket: https://en.wikipedia.org/wiki/Nuclear_thermal_rocket

This is effectively a nuclear reactor where the propellant acts as the coolant. The propellent (often liquid hydrogen) is heated to very high temperatures inside the reactor and is then allowed to escape this provides thrust as well as carrying away the reactor heat, whilst leaving the reactor core intact inside the rocket engine.

Atmospheric nuclear tests were banned in the US in 1963, but nuclear rocket engines were physically tested after that in the US under the NERVA program: https://en.wikipedia.org/wiki/NERVA

Multiple tests of the NERVA thermal nuclear rocket were carried out at the Nevada test site in the 60’s some at more than 1 GW power and producing a specific impulse of 811 seconds (compared to chemical rockets which are limited to around 450 seconds at best).

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    $\begingroup$ Thermal nuclear rockets should be very safe to fly. They will not be used to lift a rocket off the launch pad, they would only be activated in Earth orbit and beyond. During launch the reactor would have control rods held in place to prevent any significant nuclear activation. Testing is another matter, but it should be possible to design a test rig with multiple safety features (I'm not a nuclear expert). But there are still design challenges and regulatory challenges to be overcome. I suspect the advent of the SpaceX Starship may dent interest in the nuclear thermal rocket (we shall see) $\endgroup$
    – Slarty
    Jan 25, 2023 at 8:19
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    $\begingroup$ @TheRocketfan Chernobyl didn't explode. Nor did Three Mile Island or Fukushima. They suffered a meltdown, something very different from a nuclear explosion. $\endgroup$ Jan 25, 2023 at 14:12
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    $\begingroup$ @DavidHammen - Chernobyl did explode; mainly a steam explosion but it was the result of a runaway nuclear chain-reaction. $\endgroup$
    – antlersoft
    Jan 25, 2023 at 15:33
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    $\begingroup$ The issue isn't how safe they are to fly. It's how safe they are to crash. This isn't a bomb or a meltdown. Think nuclear sub dropped from space. $\endgroup$ Jan 25, 2023 at 16:29
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    $\begingroup$ Might be worth mentioning that the Earth's seas are currently awash in ships with nuclear power plants, including all US carriers, most of its subs, and at one point many of its cruisers. So sticking a nuclear generator in a craft to provide power for propulsion isn't exactly a strange new idea. $\endgroup$
    – T.E.D.
    Jan 25, 2023 at 19:40

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