Since nuclear weapons were developed in the Manhattan Project, safety and control have been prime concerns. Safety in this instance means preventing an unintended nuclear detonation or the release of hazardous materials from a weapon-in a fire or airplane crash, for example.
Control has to do with preventing unauthorized use of a nuclear weapon.
The table on the facing page lists safety and control features of weapons now in the U.S. nuclear stockpile or under development. In 1952, missiles and bombs began to be carried on the outside of the aircraft, so the fissile components were to be inserted by an electrically operated screw-jack. Elaborate procedures have been designed for missile crews to follow before a weapon can be launched. Submarine ballistic missile launches also require complex, coordinated procedures to be conducted by a majority of the entire crew. But over the years, a number of safety and control features have also been incorporated into some, but not all of, the weapons themselves.