Obviously there's the problem of testing such an engine. You'd be ejecting uranium fission products into the environment, making it extremely dangerous for any people nearby and doing significant damage to any wildlife present. But are there any other factors that would make making a nuclear salt-water rocket difficult?

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    $\begingroup$ I feel that your question is probably best inverted. "What are the easy bits of building nuclear salt water rockets?", which leads to simple and straightforward answers like "we've given it a name already" and "we know how to manufacture the fuel" because literally everything else is hideously difficult. I mean, seriously. Steady state exploding nuclear fluid flow? $\endgroup$ Aug 2, 2022 at 8:04
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    $\begingroup$ I am skeptical as to whether the principle of the nuclear salt water rocket has actually been thought out very well, and many descriptions of it seem like "toy models". For the higher performance versions (i.e. performance substantially in excess of well-studied and plausible GCNR designs) one wonders if the heat dissipation issue can actually be resolved at all. $\endgroup$
    – ikrase
    Aug 2, 2022 at 9:43
  • $\begingroup$ Why do you need other factors? $\endgroup$
    – gerrit
    Aug 2, 2022 at 12:07

1 Answer 1


Well with the design proposed by Robert Zubrin, the man to first propose this theoretical type of rocket, it is not certain that fission within current proposed nuclear saltwater rockets could easily be controlled:

"Whether fast criticality can be controlled in a rocket engine remains an open question" - Ralph L. McNutt Jr. from the NASA Institute for Advanced Concepts

It was also considered very expensive if the rocket uses 235U - the uranium isotope originally proposed for this kind of rocket- but people did try to see if other cheaper isotopes can be utilized like 239Pu and 233U. However, this could still be costly and pretty radioactive unless a much better potential fusion-fission hybrid reactor can be developed in the future.


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