Starfish Prime - Explosion

Explosion

On July 9, 1962, at 09:00:09 Coordinated Universal Time, (July 8, Honolulu time, at nine seconds after 11 p.m.), 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′W / 16.467°N 169.633°W / 16.467; -169.633Coordinates: 16°28′N 169°38′W / 16.467°N 169.633°W / 16.467; -169.633. 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 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.

After the Starfish Prime detonation, bright auroras were observed in the detonation area as well as in the southern conjugate region on the other side of the equator from the detonation. According to one of the first technical reports, "The visible phenomena due to the burst were widespread and quite intense; a very large area of the Pacific was illuminated by the auroral phenomena, from far south of the south magnetic conjugate area (Tongatapu) through the burst area to far north of the north conjugate area (French Frigate Shoals). . . . At twilight after the burst, resonant scattering of light from lithium and other debris was observed at Johnston and French Frigate Shoals for many days confirming the long time presence of debris in the atmosphere. An interesting side effect was that the Royal New Zealand Air Force was aided in anti-submarine maneuvers by the light from the bomb."

In part, these auroral effects were predicted by Nicholas Christofilos, a scientist who had earlier worked on the Operation Argus high-altitude nuclear shots.

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.

Pages 19–21 of "A 'Quick Look' at the Technical Results of Starfish Prime", August 1962 states:

"At Kwajalein, 1,400 miles to the west, a dense overcast extended the length of the eastern horizon to a height of 5 or 8 degrees. At 0900 GMT a brilliant white flash burned through the clouds rapidly changing to an expanding green ball of irradiance extending into the clear sky above the overcast. From its surface extruded great white fingers, resembling cirro-stratus clouds, which rose to 40 degrees above the horizon in sweeping arcs turning downward toward the poles and disappearing in seconds to be replaced by spectacular concentric cirrus like rings moving out from the blast at tremendous initial velocity, finally stopping when the outermost ring was 50 degrees overhead. They did not disappear but persisted in a state of frozen stillness. All this occurred, I would judge, within 45 seconds. As the greenish light turned to purple and began to fade at the point of burst, a bright red glow began to develop on the horizon at a direction 50 degrees north of east and simultaneously 50 degrees south of east expanding inward and upward until the whole eastern sky was a dull burning red semicircle 100 degrees north to south and halfway to the zenith obliterating some of the lesser stars. This condition, interspersed with tremendous white rainbows, persisted no less than seven minutes."

"At zero time at Johnston, a white flash occurred, but as soon as one could remove his goggles, no intense light was present. A second after shot time a mottled red disc was observed directly overhead and covered the sky down to about 45 degrees from the zenith. Generally, the red mottled region was more intense on the eastern portions. Along the magnetic north-south line through the burst, a white-yellow streak extended and grew to the north from near zenith. The width of the white streaked region grew from a few degrees at a few seconds to about 5-10 degrees in 30 seconds. Growth of the auroral region to the north was by addition of new lines developing from west to east. The white-yellow auroral streamers receded upward from the horizon to the north and grew to the south and at about 2 minutes the white-yellow bands were still about 10 degrees wide and extended mainly from near zenith to the south. By about two minutes, the red disc region had completed disappearance in the west and was rapidly fading on the eastern portion of the overhead disc. At 400 seconds essentially all major visible phenomena had disappeared except for possibly some faint red glow along the north-south line and on the horizon to the north. No sounds were heard at Johnston Island that could be definitely attributed to the detonation."

"Strong electromagnetic signals were observed from the burst, as were significant magnetic field disturbances and earth currents."

In 2006, Palmer Dyal described the particle and field measurements of the Starfish diamagnetic cavity and the injected beta flux into the artificial radiation belt in the Journal of Geophysical Research. His measurements describe the explosion from 0.1 milliseconds to 16 minutes after the detonation.