Talk-Polywell.org

I had a setting where peolple wanted to build heavy lifters discretely. Since the second stages would continue to be used in space and they weremt as concerned about being sued, an NTR would suit there purposes well.

I was thinking a monolithic SLS silicon carbide build for the core. Carbon dioxide would be both moderator and fuel, possibly with methane as a backup. After launch the ship would use the reactor with a rankine cycle for power. Ideally a loss of coolant would mean a loss of moderator, shutting it down. The core and containment system would be designed to passively keep the reactor just below meltdown. I was even thinking it would have a partial liquid fuel cycle, further reducing critical isotope buildup.

It waa rendered obsolete when i realized you might as well just go with an orion drive for the heavy lifters, and Musk is making even that somewhat pointless with Starship.

It would be a cool grad school project for a nuclear engineer or such to model it out and give it specs though.