Starfish Prime Nuclear Test

Date: July 9, 1962 • Location: Starfish Prime, International

The United States conducted the Starfish Prime high-altitude nuclear test, the largest nuclear explosion in outer space.

Starfish Prime was a high-altitude nuclear test conducted by the United States, a joint effort of the United States Atomic Energy Commission (AEC) and the Defense Atomic Support Agency. It was launched from Johnston Atoll on July 9, 1962, and was the largest nuclear test conducted in outer space, and one of five conducted by the US in space.