Nuclear propelled KE bomb

I've seen ideas for nuclear-propelled spacecraft and for KE projectiles but not nuclear-propelled KE projectiles. We know why KE bombs are nice- significant damage without fallout. Why a nuke tube? Nuclear propulsion gives us a high speed launch without tons of fuel or specialized launch vehicles. Firing from a tube significantly reduces fallout. There's also the possibility of reusing old warheads (as opposed to dismantlement) which would reduce costs.

Launch effectiveness? Ehh, not so sure. Check the link for a bunch of specs on Operation Plumbob. Operation Plumbbob's Pascal-B test had a blast yield 300 Tons (of TNT). The device was at the bottom of a 500ft length, 4ft diameter shaft with a concrete plug directly above the device and a ~900 kg steel cap (approx 2000lb) welded to the top of the shaft. The blast launched the cap at about 66 km/s, so the cap had an energy of about 59400000 J (59.4 MJ) or 0.01419 TNT Tons. A 300 Ton blast yield to get a 0.01 Ton launch energy. That is some crappy efficiency. For reference, the Little Boy had 16 kT yield.

It could be much better though. In the link it describes the effects of the nuclear blast and how it propels objects. There was also the unimplemented Project Thunderwell. "The idea was that a deep shaft would be dug in the earth and filled with water. A spacecraft would be placed atop this shaft, and a nuclear explosive would be detonated at the bottom."

There's also Project Orion which was a nuclear-propelled spacecraft. It was carefully calculated for efficient launch. My brain is taking a fart right now and I can't find anything to calculate launch efficiency.

Placing a guidance system on the projectile is possible. Building a circuit capable of surviving the massive acceleration wouldn't be too difficult. Launch could be dampened to reduce the impulse too. Making guidance fins that actually affect a multi-ton bomb might be another story. Perhaps thrust vectoring with a flat/oval aerodynamic shape would be more effective at turning.

The projectile would need to be aerodynamically designed. It may be useful to have a crumpling/expanding nose for a faster dump of energy on impact.

Cost? You'd need a nuclear warhead. A typical nuke cost $1M USD in the '80s. It's possible that warheads could be reused. Dig a big hole. I dunno. A gigantic aerodynamic rod of dense material. Tungsten would be excellent but stupidly expensive. Repurpose a seamless pipe manufacturing plant perhaps? You could make huge steel pipes and fill them with a cheap dense material (lead comes to mind) and use a heat-resistant nosecone and outer plating. So probably a few million to research, a few million per launch.

some final questions an ideas -What size projectile can one feasibly launch? -What kind of launch angle / trajectory are we looking at? -Can we put the projectiles into low-orbit and drop them on the other side of the earth? -Is it even guidable? -Do we need to worry about terminal velocity? The projectile doesn't have to rely on gravitationally energy when you can turn the projectile and use the horizontal momentum. -While the projectile is an unstoppable slug of metal, how vulnerable is the guidance system? -Where do we launch them from? Land? Sea? Air? -How about a two-stage launch. A light launch puts the projectile and an entire launch tube into the air. Then the airborne launch tube provides the majority of the energy while the device is in a low-fallout area

links below