Starfish Prime

Starfish Prime
The debris fireball stretching along Earth's magnetic field with air-glow aurora as seen at 3 minutes from an RC-135 surveillance aircraft.
Information
Country	United States
Test series	Operation Fishbowl
Test site	Johnston Island
Date	July 9, 1962
Test type	Exoatmospheric
Yield	1.4 megatons (6.0 PJ)

Starfish Prime was a high-altitude nuclear test conducted by the United States on July 9, 1962, a joint effort of the Atomic Energy Commission (AEC) and the Defense Atomic Support Agency.

A Thor rocket carrying a W49 thermonuclear warhead (manufactured by Los Alamos Scientific Laboratory) and a Mk. 2 reentry vehicle was launched from Johnston Island in the Pacific Ocean. The explosion took place at an altitude of 250 miles (400 km), above a point 19 miles (31 km) southwest of Johnston Island. It was one of five tests conducted by the US in outer space as defined by the Fédération Aéronautique Internationale (FAI). It produced a yield equivalent to 1.4 megatonnes of TNT. It was the largest man-made nuclear explosion in outer space.

The Starfish test was one of five high-altitude tests grouped together as Operation Fishbowl within the larger Operation Dominic, a series of tests in 1962 begun in response to the Soviet announcement on August 30, 1961 that they would end a three-year moratorium on testing.

In 1958 the United States had completed six high-altitude nuclear tests, but the high-altitude tests of that year produced many unexpected results and raised many new questions. According to the U.S. Government Project Officer's Interim Report on the Starfish Prime project: