The W25 was a small nuclear warhead developed by the United States Air Force and Los Alamos Scientific Laboratory for air-defense use. It was a fission bomb with a nominal yield of 1.7 kt. The W25 was used for the MB-1 "Ding Dong", an unguided air-to-air rocket used by US Northrop F-89 Scorpion, F-101 Voodoo, and F-106 Delta Dart interceptor aircraft, and Canadian CF-101 Voodoo aircraft, as part of NATO nuclear sharing. The MB-1 entered service in 1957 and was eventually redesignated the AIR-2 Genie. Limited numbers were carried by Air National Guard F-106 aircraft until December 1984. History Genie application The W25 program began in March 1951, when the Division of Military Application suggested that the use of nuclear weapons to blunt enemy aircraft attacks be examined. However, little immediate action was taken because the state of the art in both warheads and missiles was not yet advanced enough for the proposal to be practicable. Technology soon improved and, by February 1952, the Joint Chiefs of Staff requested that the Joint Air Board study the matter. The study was completed in January 1953, which suggested that gun-, rocket- and missile-carried warheads were possible, launched from interceptor and bomber aircraft. The board specifically recommended the development of nuclear warheads for the RIM-8 Talos, CIM-10 Bomarc and MIM-3 Nike Ajax surface-to-air missiles. During discussions about the report, it was believed that tens of thousands of air defense warheads would be needed, and so the warheads would have to be economical in nuclear materials to reduce their cost. At the same time, the US air force wanted a high-velocity, nuclear armed, air to air missile. The air force believed that, because air defenses operated under peacetime conditions, it was desirable to have the ability for a human to make confirmation that an unidentified aircraft was indeed hostile before engaging it. Sandia National Laboratory had been investigating the high-altitude operation of nuclear weapons since 1952 and, in August 1953, concluded that the only major concern was high-voltage breakdown at low pressures. That meant that existing weapon-firing sets were unsuitable, so solutions were examined. It was soon decided that the problem could be solved through the use of a sealed nuclear weapon, with the weapon filled with high-pressure air to prevent electric arcing. In October 1953, the air defense warhead programs took an unusual turn in that they avoided the then-trend to highly standardise