SLAMS: The Flying Crowbar
The device itself was called the Supersonic Low Altitude Missile. Despite being the size of a bomber, it was to to be unmanned, without a crew or pilot. The device would have carried an apocalyptic 16 nuclear warheads when fully armed. It would be powered by a nuclear fission reactor that generated up to 600 megawatts of power. This thermal energy (as well as radioactive fission products) was jammed into the combustion chambers of ramjets.
This allowed a truly wild capability: supersonic speed, barely 80 feet off the ground to avoid radar and air defenses. The system would be guided by an onboard inertial guidance system, followed by a newly designed system eventually called TERCOM, which is still used in cruise missiles today. Because it was nuclear powered, it could operate indefinitely, able to loiter and fly in circles until called in for a strike.
There were massive downsides however. The exhaust of the vehicle could be likened to a small, mobile Chernobyl disaster. It was so destructive that it was theorized that the weapon could cause damage just by circling around a target before even attacking with it's offensive weapons. Not only would the area behind the exhaust be irradiated, but in the vehicle's final descent phase, it would be burnt and blasted with sonic booms as the SLAMS traversed possibly as low as 80 feet in the air, while flying at Mach 3. Individuals would die from overpressure, and buildings would be devastated. The vehicle would fly to a target, descend to avoid air defenses and radar, and drop up to 16 nuclear warheads on various targets, before finally nosediving and detonating a final warhead. Such a devastating weapon, after being researched since 1956, was finally considered "too Provocative" by the Department of Defense and State Department in July 1964.