Supersonic Low Altitude Missile

The Supersonic Low Altitude Missile or SLAM was a U.S. Air Force nuclear weapons project conceived around 1955, and cancelled in 1964. SLAMs were conceived of as unmanned nuclear-powered ramjets capable of delivering thermonuclear warheads deep into enemy territory.

Source: Wikipedia — Supersonic Low Altitude Missile (CC BY-SA 4.0)