The genius of the nuclear lightbulb design is the irrotational vortex of neon gas that contains the plasma - this design separates the hot stuff from any solid

The genius of the nuclear lightbulb design is the irrotational vortex of neon gas that contains the plasma - this design separates the hot stuff from any solid materials that might melt. This vortex provides the pressure required to reach criticality and separates the plasma from the single crystal beryllium oxide walls, which in turn separates the neon vortex from the reaction mass (hydrogen gas seeded with tungsten nanoparticles when used as a rocket engine and water when used as a power plant). At that temperature, the plasma emits most of its energy as a black body radiator and the SC BeO walls are designed to pass through all of that radiation. The constant flow of neon cools down the entire system. Like I said, UAC actually built functional prototypes that went just short of using fissile material. The non-nuclear parts of the design were validated experimentally. The only remaining theoretical parts are precise control of the fission reaction, which they didn't have the computational power for back then, and long term operation/maintenance, since imperfections in the SC beryllium oxide degrade the container and cause it to melt down eventually. There were plans to demonstrate a slow neutron plasma, which would significantly reduce material degradation, but they never got to it before Nixon canceled the Mars program.