Starfish Prime was a high-altitude nuclear test conducted by the United States of America on July 9, 1962.
On July 9, 1962 the Starfish Prime test was successfully detonated at an altitude of 400 kilometres (250 mi). The coordinates of the detonation were 16°28′N 169°38′WCoordinates: 16°28′N 169°38′W. The actual weapon yield came very close to the design yield, which various sources have set at different values in the range of 1.4 to 1.45 megatons (6.0 PJ).
The Thor missile carrying the Starfish Prime warhead reached a maximum height of about 1100 km (just over 680 miles), and the warhead detonated on its downward trajectory when it had fallen to the programmed altitude of 400 kilometres (250 mi). The nuclear warhead detonated 13 minutes and 41 seconds after liftoff of the Thor missile from Johnston Island.
Starfish Prime caused an electromagnetic pulse (EMP) which was far larger than expected, so much larger that it drove much of the instrumentation off scale, causing great difficulty in getting accurate measurements. The Starfish Prime electromagnetic pulse also made those effects known to the public by causing electrical damage in Hawaii, about 1,445 kilometres (898 mi) away from the detonation point, knocking out about 300 streetlights, setting off numerous burglar alarms and damaging a telephone company microwave link. The EMP damage to the microwave link shut down telephone calls from Kauai to the other Hawaiian islands.
A total of 27 small rockets were launched from Johnston Island to obtain experimental data from the Starfish Prime detonation. In addition, a large number of rocket-borne instruments were launched from a firing area at Barking Sands, Kauai in the Hawaiian Islands.
A very large number of United States military ships and aircraft were operating in support of Starfish Prime in the Johnston Island area and across the nearby North Pacific region.
A few military ships and aircraft were also positioned in the region of the South Pacific Ocean near the Samoan Islands. This location was at the southern end of the magnetic field line of the Earth’s magnetic field from the position of the nuclear detonation, an area known as the southern conjugate region for the test. In addition, an uninvited scientific expeditionary ship from the Soviet Union was stationed near Johnston Island for the test and another Soviet scientific expeditionary ship was located in the southern conjugate region near the Samoan Islands.
According to U.S. atomic veteran Cecil R. Coale, some hotels in Hawaii offered “rainbow bomb” parties on their roofs for Starfish Prime, contradicting some reports that the artificial aurora was unexpected.
While some of the energetic beta particles followed the Earth’s magnetic field and illuminated the sky, other high-energy electrons became trapped and formed radiation belts around the earth. There was much uncertainty and debate about the composition, magnitude and potential adverse effects from this trapped radiation after the detonation. The weaponeers became quite worried when three satellites in low earth orbit were disabled. These man-made radiation belts eventually crippled one-third of all satellites in low earth orbit. Seven satellites failed over the months following the test as radiation damaged their solar arrays or electronics, including the first commercial relay communication satellite, Telstar. Detectors on Telstar, TRAAC, Injun, and Ariel 1 were used to measure distribution of the radiation produced by the tests.
In 1963, Brown et al. reported in the Journal of Geophysical Research that Starfish Prime had created a belt of MeV electrons, and Wilmot Hess reported in 1968 that some Starfish electrons remained for five years.
Resulting scientific discoveries
The Starfish bomb contained Cd-109 tracer which helped work out the seasonal mixing rate of polar and tropical air masses.
The Starfish EMP waveform measured by Richard L. Wakefield of Los Alamos led to a revolution in understanding this nuclear effect.