Like "Kiwi", a rocket engine of nuclear energy, tested at the Alamos Scientific Laboratory (LASL) in 1959. (Not to be confused with Kivi which is a Dutch aeronautical agency and also a Russian engine).

From Appendix 6: Rocket engine with nuclear operation for use in American ICBM missiles.

“Kiwi A”

-More than the engine itself, it is the name of the program. Kiwi that is a bird that cannot fly.

-It used uranium as fuel, but it was only statically tested. It was included in the Rover and the Pluto Project (the latter was an atomic ramjet). Another Project was the Snap to give auxiliary energy to the satellites.

"Kiwi test installation”

"Combustion chamber"

-The control bar is introduced through the center, hydrogen enters from above.