I haven’t had an opportunity to really dig into this, but Boeing just patented a jet engine powered not by hydrocarbon fuel combustion but by small nuclear explosions. Basically an Orion (via laser-driven inertial confinement compression of tiny fusion fuel pellets) in a jet, stuck on a passenger plane.
The US Patent Office page on this.
THIS should link directly to the PDF of the patent.
Sigh. Every single time I think I’ve got a handle on “this is everything in the world of NPP, I can finally finish the book,” they suck me back in.