 On October 19, 1962, at about 90 minutes before midnight (local Johnston Island time), an XM-33 "Strypi" rocket launched a low-yield nuclear warhead which detonated successfully at an altitude of .It was reported that the yield and burst altitude were very close to those desired, but according to most official documents the exact nuclear yield remains classified.It is reported in the open literature as simply being less than 20 kilotons.