The United States detonated a nuclear weapon in space as part of Operation Plowshare on July 9, 1962. The 1.4 megaton device, code-named Starfish Prime, was launched from Johnston Island in the Pacific Ocean and detonated at an altitude of 400 kilometers (250 miles). The resulting explosion was equivalent to a magnitude 8.8 earthquake on the Richter scale. There is no record of any other country detonating a nuclear weapon in space.