High-altitude nuclear explosions
by Wm. Robert Johnston
last updated 28 January 2009
Effects of high-altitude nuclear explosions, summary:
The familiar immediate effects of low-altitude nuclear explosions are flash, blast, and prompt radiation. Effects are significantly different for explosions above most of the atmosphere. Since blast is the shock wave transmitted through air, this is attenuated with height and is absent for explosions beyond the atmosphere. Flash is the visible and infrared light pulse from the fireball formed from heated air. With higher altitude, the fireball formation is significantly altered with consequent effects on flash. Prompt radiation includes ionizing radiation from the nuclear reactions in the warhead and decay of fission products left by the explosion. These radiations, particularly neutron radiation, are significantly attenuated by the atmosphere for low altitude bursts. For explosions above most of the atmosphere, ranges of prompt radiation effects are greater than for atmospheric bursts.
Several effects are relatively unique to high altitude bursts:
- Electromagnetic pulse (EMP) is important only for high altitude bursts. For such detonations, ionization of the upper atmosphere can produce a brief intense pulse of radio frequency radiation which can damage or disrupt electronic devices. For explosions above most of the atmosphere, EMP can affect large areas.
- Ionization of the atmosphere from explosions in the atmosphere can interfere with radar and radio communications for short periods.
- Charged particles produced by explosions above the Earth's atmosphere can be captured by the Earth's magnetic field, temporarily creating artificial radiation belts that can damage spacecraft and injure astronauts/cosmonauts in orbit.
Effects of high-altitude nuclear explosions, detail:
Nuclear tests at high altitudes, summary:
From 1958 to 1962, the U.S. and U.S.S.R. conducted over a dozen nuclear tests in the Earth's upper atmosphere or in space--the highest at an altitude of 540 km. The table below lists information on all tests above 20 km altitude.
|nation||test name||date||time (UT)||lat. (°)||long. (°)||alt. (km)||location||yield (kt)||warhead||sources|
|USA ||HARDTACK I--Yucca ||28 Apr 1958 ||02:40:00.3||12.617 N||163.025 E||26.2||Pacific Ocean || 1.7||W-25, plutonium implosion?||4,6,14|
|USA ||HARDTACK I--Teak ||01 Aug 1958 ||10:50:05.6||16.744 N||169.533 W||76.8||Johnston Island||3800 ||W39, thermonuclear, 50% fission||4,6,14|
|USA ||HARDTACK I--Orange ||12 Aug 1958 ||10:30:08.6||16.358 N||169.536 W|| 43 ||Johnston Island ||3800 ||W39, thermonuclear, 50% fission||4,6,14|
|USA ||Argus I ||27 Aug 1958 ||02:28 ||38.5 S|| 11.5 W|| 200 ||South Atlantic Ocean|| ~1.5||W-25, plutonium implosion?||2,4,6,9,14|
|USA ||Argus II ||30 Aug 1958 ||03:18 ||49.5 S|| 8.2 W|| 240 ||South Atlantic Ocean|| ~1.5||W-25, plutonium implosion?||2,4,6,9,14|
|USA ||Argus III ||06 Sep 1958 ||22:13 ||49.5 S|| 9.7 W|| 540 ||South Atlantic Ocean|| ~1.5||W-25, plutonium implosion?||2,4,6,9,14|
|USSR||#88 Groza ("Joe 79") ||06 Sep 1961 ||06:00 ||48.45 N|| 44.3 E|| 22.7||Kapustin Yar || 10.5||R-12?||11,12,14,25,26,27,28|
|USSR||#115 Grom ("Joe 98") ||06 Oct 1961 ||07:15 ||48.45 N|| 44.3 E|| 41.3||Kapustin Yar || 40 ||R-5||10,11,13,14,25,26,27,28|
|USSR||K PROJECT--#127 K-2 ("Joe 109?") ||27 Oct 1961 ||? ||46.1 N|| 70.6 E|| 150 ||Kapustin Yar || 1.2||R-12?||10,11,14,16,25,26,27,28|
|USSR||K PROJECT--#128 K-1 ("Joe 105?") ||27 Oct 1961 ||? ||46.7 N|| 69.6 E|| 300 ||Kapustin Yar || 1.2||R-12?||10,11,14,16,25,26,27,28|
|USA ||DOMINIC I/FISHBOWL--Starfish Prime ||09 Jul 1962 ||09:00 ||17.2 N||169.1 W|| 399 ||Johnston Island ||1400 ||W-49, thermonuclear||4,6,9,14|
|USA ||DOMINIC I/FISHBOWL--Checkmate ||20 Oct 1962 ||07:30 ||16.0 N||169.5 W|| 147 ||Johnston Island || <20*||XW-50X1||3,4,6,14|
|USSR||K PROJECT--#184 K-3 ("Joe 157") ||22 Oct 1962 ||03:40:45 ||49 N*|| 46 E*|| 290 ||Kapustin Yar || 300 ||R-12?||1,5,8,10,11,14,25,26,28|
|USA ||DOMINIC I/FISHBOWL--Bluegill Triple Prime||26 Oct 1962 ||08:59 ||16.9 N||169.2 W|| 48.2||Johnston Island || 400 ||W50, boosted fission||3,4,6,7,14|
|USSR||K PROJECT--#187 K-4 ("Joe 160") ||28 Oct 1962 ||04:41:20 ||47 N|| 64 E|| 150 ||Kapustin Yar || 300 ||R-5M, thermonuclear||1,5,10,11,14,15,24,25,26,28|
|USSR||K PROJECT--#195 K-5 ("Joe 168") ||01 Nov 1962 ||09:12 ||49 N*|| 46 E*|| 59 ||Kapustin Yar || 300 ||R-12?||10,11,14,17,25,26,28|
|USA ||DOMINIC I/FISHBOWL--Kingfish ||01 Nov 1962 ||11:10 ||16.6 N||169.4 W|| 96.3||Johnston Island || 400 ||W50, boosted fission||3,4,6,7,14|
|USA ||DOMINIC I/FISHBOWL--Tightrope ||04 Nov 1962 ||06:30 ||17.1 N||169.1 W|| 21 ||Johnston Island || <20*||W31||3,4,6,14|
Notes: The exact yields of shots Checkmate (20 Oct 1962) and Tightrope (4 Nov 1962) are unknown; the U.S. has reported their yields as 0-20 kt. For the K Project shots K-3 and K-5, reported locations from  refer to the delivery missile launch site at Kapustin Yar; these missiles travelled downrange towards Sary Shagan before detonation. All shots in the table above were delivered by rocket or missile with the exception of shot Yucca (28 April 1958) which was suspended from a balloon.
The figure below plots altitude versus geographic latitude for all nuclear detonations. High altitude explosions fall in three groups, from left to right: U.S. tests over the South Atlantic (Operation Argus); U.S. tests near Johnston Island in the Pacific Ocean; and Soviet tests near Kapustin Yar (southern Russia near Kazakhstan).
Nuclear tests at high altitudes, detail:
The high altitude nuclear tests included these series:
- USA--Three shots during Operation Hardtack I, 1958: these shots were to investigate effects of high altitude detonations. 
- USA--The three shots of Operation Argus, 1958: this series was crafted to test aspects of production of trapped particle radiation belts from high altitude nuclear explosions. This was the only U.S. above-ground test series which was conducted in secret; it was not announced until 19 March 1959. 
- USSR--Two shots in 1961 at high altitudes.
- USSR--The K Project shots, 1961 and 1962: this series tested the effects of high altitude nuclear explosions on ballistic missile defense systems. 
- USA--The five shots of Operation Fishbowl, 1962: this series, during the atmospheric test series Operation Dominic, investigated effects of high altitude nuclear explosions. Bluegill Triple Prime was the third attempt for this particular test, with two previous attempts resulting in destruction of the missile and warhead (the first loss occurred on the pad, resulting in significant contamination of the site). The last shot, shot Tightrope, was the last atmospheric nuclear test by the United States. 
The table below lists, for detonations at altitudes over 40 km, the duration of the thermal pulse, data on the geomagnetic field at the shot location, and data on any artificial radiation belts produced. [7,19,21,22,23]
|shot data||duration of thermal pulse (s)||magnetic field data at detonation location||radiation belt production|
|shot||date||altitude (km)||yield (kt)||strength (G)||declination (°)||inclination (°)||L value||characteristics||injected electrons||decay time|
|Teak||01 Aug 1958||77||3800||0.1||0.332||10.6||30.0||1.12||low altitude||<1021||few days|
|Orange||12 Aug 1958||43||3800||0.15||0.337||10.6||29.6||1.12||low altitude||<1021||1 day|
|Argus I||27 Aug 1958||200||1.5|| ||0.263||-25.5||-55.3||1.7||narrow band|| ||0-20 days|
|Argus II||30 Aug 1958||240||1.5|| ||0.285||-22.6||-58.7||2.1||narrow band|| ||10-20 days|
|Argus III||06 Sep 1958||540||1.5|| ||0.256||-21.7||-58.4||2.0||narrow band|| ||10-20 days|
|#115||06 Oct 1961||41||40|| ||0.494||6.9||65.6||1.75|| || || |
|K-2||27 Oct 1961||150||1.2|| ||0.473||6.9||66.0||1.8|| || || |
|K-1||27 Oct 1961||300||1.2|| ||0.442||6.3||65.7||1.8|| || || |
|Starfish Prime||09 Jul 1962||399||1400||<0.001||0.288||10.6||30.0||1.12||wide distribution||1.3x1025||1-2 years|
|Checkmate||20 Oct 1962||147||<20||<0.001||0.320||10.6||28.7||1.1|| || || |
|K-3||22 Oct 1962||290||300|| ||0.444||6.3||65.8||1.8||wide distribution||3.6x1025||30 days|
|Bluegill Triple Prime||26 Oct 1962||48||400||0.1||0.336||10.7||30.5||1.12|| || || |
|K-4||28 Oct 1962||150||300|| ||0.474||6.9||66.0||1.8||wide distribution||1.2x1025||30 days|
|K-5||01 Nov 1962||59||300|| ||0.494||7.3||66.2||1.75||narrow band||1.2x1024||30 days|
|Kingfish||01 Nov 1962||96||400||0.15||0.328||10.6||29.8||1.12|| || || |
The radiation belts from Starfish Prime caused damage to several satellites. Operation of Ariel I became intermittent after 7 days; Traac and Transit 4B both showed significant degradation of output from their solar cells before ceasing operations 36 and 24 days after the detonation, respectively. 
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© 2005-2006, 2009 by Wm. Robert Johnston.
Last modified 28 January 2009.
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