High - altitude nuclear explosion 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 weapon s , 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 Dominic I 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 . EMP generation . The strong electromagnetic pulse ( EMP ) that results has several components . In the first few tens of nanoseconds , about a tenth of a percent of the weapon yield appears as powerful gamma rays with energies of one to three mega - electron volts ( MeV , a unit of energy ) . The gamma rays penetrate the atmosphere and collide with air molecules , depositing their energy to produce huge quantities of positive ions and recoil electrons ( also known as Compton electrons ) . The impacts create MeV - energy Compton electrons that then accelerate and spiral along the Earth ' s magnetic field lines . The resulting transient electric fields and currents that arise generate electromagnetic emissions in the radio frequency range of 15 to 250 megahertz ( MHz , or one million cycles per second ) . This high - altitude EMP occurs between 30 and 50 kilometers ( 18 and 31 miles ) above the Earth ' s surface . The potential as an anti - satellite weapon became apparent in August 1958 during " Hardtack Teak " . The EMP observed at the Apia Observatory at Samoa was four times more powerful than any created by solar storms , while in July 1962 the " Starfish Prime " test damaged electronics in Honolulu and New Zealand ( approximately 1 , 300 kilometers away ) , fused 300 street lights on Oahu ( Hawaii ) , set off about 100 burglar alarm s , and caused the failure of a microwave repeating station on Kauai , which cut off the sturdy telephone system from the other Hawaiian islands . The radius for an effective satellite kill for the various prompt radiations produced by such a nuclear weapon in space was determined to be roughly 80 km . Further testing to this end was carried out , and embodied in a Department of Defense program , " Program 437 " . Drawbacks . There are problems with nuclear weapons carried over to testing and deployment scenarios , however . Because of the very large radius associated with nuclear events , it was nearly impossible to prevent indiscriminate damage to other satellites , including one ' s own satellites . " Starfish Prime " produced an artificial radiation belt in space which soon destroyed three satellites ( Ariel , TRAAC , and Transit 4B all failed after traversing the radiation belt , while Cosmos V , Injun I and Telstar 1 suffered minor degradation , due to some radiation damage to solar cell s , etc . ) . The radiation dose rate was at least 60 rads / day at four months after " Starfish " for a well - shielded satellite or manned capsule in a polar circular earth orbit , which caused NASA concern with regard to its manned space exploration programs . Differences from atmospheric tests . In general , nuclear effects in space ( or very high altitudes ) have a qualitatively different display . While an atmospheric nuclear explosion has a characteristic mushroom - shaped cloud , high - altitude and space explosions tend to manifest a spherical ' cloud , ' reminiscent of other space - based explosions until distorted by Earth ' s magnetic field , and the charged particle s resulting from the blast can cross hemispheres to create an auroral display which has led documentary maker Peter Kuran to characterize these detonations as ' the rainbow bombs ' . The visual effects of a high - altitude or space - based explosion may last longer than atmospheric tests , sometimes in excess of 30 minutes . Heat from the " Bluegill Triple Prime " shot , at an altitude of 50 kilometers ( 31 mi ) , was felt by personnel on the ground at Johnston Atoll , and this test caused retina burns to two personnel at ground zero who were not wearing their safety goggles . Soviet high - altitude tests . The Soviets detonated four high - altitude tests in 1961 and three in 1962 . During the Cuban Missile Crisis in October 1962 , both the US and the USSR detonated several high - altitude nuclear explosions as a form of saber - rattling . The Soviet tests were meant to demonstrate their anti - ballistic missile defense s which would supposedly protect their major cities in the event of a nuclear war . The worst effects of a Soviet high - altitude test occurred on 22 October 1962 , in ‘ Operation K ’ ( ABM System A proof tests ) when a 300 kt missile - warhead detonated near Dzhezkazgan at 290 - km altitude . The EMP fused 570 km of overhead telephone line with a measured current of 2 , 500 A , started a fire that burned down the Karaganda power plant , and shut down 1 , 000 - km of shallow - buried power cables between Aqmola and Almaty . The Partial Test Ban Treaty was passed the following year , ending atmospheric and exoatmospheric nuclear tests . The Outer Space Treaty of 1967 banned the stationing and use of nuclear weapons in space . The Comprehensive Nuclear - Test - Ban Treaty of 1996 prohibits all kinds of nuclear explosions ; whether over - or underground , underwater or in the atmosphere . List of high - altitude nuclear explosions . USA – Hardtack I – Johnston Atoll , Pacific Ocean US Government Films :