High-altitude nuclear explosions (HANE) have historically been nuclear explosions which take place above altitudes of 30 km, still inside the Earth's atmosphere. Such explosions have been tests of nuclear weapons, used to determine the effects of the blast and radiation in the exoatmospheric environment. The highest was at an altitude of 540 km (335.5 mi).
The only nations to detonate nuclear weapons in outer space are the United States and the Soviet Union. The U.S. program began in 1958 with the Hardtack Teak and Hardtack Orange shots, both 3.8 megatons. These warheads were initially carried on Redstone rockets. Later tests were delivered by Thor missiles for Operation Fishbowl tests, and modified Lockheed X-17 missiles for the Argus tests. The purpose of the shots was to determine both feasibility of nuclear weapons as an anti-ballistic missile defense, as well as a means to defeat satellites and manned orbiting vehicles in space. High-altitude nuclear blasts produce significantly different effects. In the lower reaches of vacuous space, the resulting fireball grows much larger and faster than it does near the ground, and the radiation it emits travels much farther.
List of high-altitude nuclear explosions
The debris fireball and aurora created by the Starfish Prime test, as seen from a KC-135 aircraft at 3 minutes.
The Starfish Prime flash as seen through heavy cloud cover from Honolulu, 1,300 km away.
United States USA -- Hardtack I -- Johnston Atoll, Pacific Ocean
Yucca 28 April 1958, 1.7 kt, 26.2 km
Teak, 1 August 1958, 3.8 Mt, 76.8 km
Orange, 12 August 1958, 3.8 Mt, 43 km
United States USA -- Argus -- South Atlantic Ocean
Argus I, 27 August 1958, 1.7 kt, 200 km
Argus II, 30 August 1958, 1.7 kt, 240 km
Argus III, 6 September 1958, 1.7 kt, 540 km (The highest known man made nuclear explosion)
Soviet Union USSR -- 1961 tests -- Kapustin Yar
Test #88, 6 September 1961, 10.5 kt, 22.7 km
Test #115, 6 October 1961, 40 kt, 41.3 km
Test #127, 27 October 1961, 1.2 kt, 150 km
Test #128, 27 October 1961, 1.2. kt, 300 km
United States USA -- Dominic I -- (Operation Fishbowl) -- Johnston Atoll, Pacific Ocean
Bluegill, 3 June 1962, failed
Bluegill Prime, 25 July 1962, failed
Bluegill Double Prime, 15 October 1962, failed
Bluegill Triple Prime, 26 October 1962, 410 kt, 50 km
Starfish, 20 June 1962, failed
Starfish Prime, 9 July 1962, 1.4 Mt, 400 km (The largest man made nuclear explosion in outer space)
Checkmate, 20 October 1962, 7 kt, 147 km
Kingfish, 1 November 1962, 410 kt, 97 km
Soviet Union USSR -- Soviet Project K nuclear tests -- Kapustin Yar
Test #184, 22 October 1962, 300 kt, 290 km
Test #187, 28 October 1962, 300 kt, 150 km
Test #195, 1 November 1962, 300 kt, 59 km
