> I’m confident that with advances in material science we would figure out how to build safe nuclear aircraft and nuclear rockets, ushering in a new space age.

I'm absolutely certain of it. In regards to nuclear rocketry, it wasn't even the anti-nuclear crowd that killed one of the most promising technologies but they certainly guaranteed it would die in the dustbins of JPL's archive.

NASA and the United Aircraft Corporation came up with a reactor design called the nuclear lightbulb [1] that used tens of kilograms of uranium instead of thousands by heating uranium hexaflouride [^1] to a plasma and using an irrotational vortex [^2] of neon gas to compress it until it became a self sustaining [^3] black body radiator [^4]. They were just about to test the reactor with real fuel when it was canceled (during Nixon's administration as part of the Mars program) but they managed to experimentally identify the remaining production challenges like the computational power needed to keep the core stable and the material science necessary to separate the vortex from the fluid economically. There has been so much progress in fields that address those challenges that many of the problems are considered solved and the remainder are surmountable engineering problems.

I really hope with this renewed interest in nuclear someone eventually revives the design and tries to bring it to its conclusion. Just based off of the declassified publications from the 60s and early 70s [2][3][4][5] it is obvious how much potential this design had: it's safe [^5], useful for rocketry and terrestrial power generation, and self breeding by nature of its design [^6]. Who knows where we could be in space exploration and the battle against climate change had the design been fully explored.

[1] https://en.wikipedia.org/wiki/Nuclear_lightbulb

[2] https://ntrs.nasa.gov/citations/19730018850

[3] https://ntrs.nasa.gov/citations/19730018851

[4] https://ntrs.nasa.gov/citations/19710010820

[5] and many more in the JPL archives! Search for "gas core reactor"

[^1] UF6 is the most common intermediate in the enrichment process and depleted UF6 is how most of our nuclear waste is stored... and this reactor is a perfect breeding reactor for the waste (see [^5]). All of the infrastructure for dealing with the materials have existed since the Manhattan project.

[^2] the opposite of a rotational vortex like a tornado, which have calm centers. In an irrotational vortex the particles in the center have the highest velocity and in the reactor it acts like a centrifuge, forcing the uraninum to the center and compressing it to tens or hundreds of atmospheres. This part was tested experimentally.

[^3] the energy of the plasma and compression from the vortex increase the neutron cross section to the point where the nuclear reaction becomes self heating with only 20kg of fuel. They stopped just short of testing the full cycle but this is the same concept behind nuclear weapons, which use precise explosives to compress nuclear fuel until it reaches criticality, except the vortex can't generate the kind of pressures necessary for a nuclear explosion.

[^4] the NASA/UAC design heats the UF6 till it radiates most of its energy away as UV. Classical steam turbines or hydrogen gas seeded with tungsten nanoparticles (in the case of a rocket engine) allow the system to extract power.

[^5] since it's an active design, tons of power is required to pump the vortex and keep the core in a fissile regime. If any part of the system fails, the core loses pressure and becomes a really expensive gas canister until the chamber is cleaned up and the core restarted. With a plasma window separating the core from a vacuum, the entire system can be designed to depressurize safetly.

[^6] anything injected into the core gets bombarded by neutrons and the vortex system constantly wicks away small amounts of the core. The system forms a closed loop that recycles unused fuel via centrifuge and it can also separate out transmuted waste [*]. The NASA/UAC team tested this with a neutron gun to simulate fission in the core.

[*] we could have had honest-to-god alchemy!