Robert Krulwich at Krulwich Wonders has a post on a chilling movie of five service members as a two kiloton device detonates 18,500 feet above them. Four were volunteers.
"On July 19, 1957, five Air Force officers and one photographer stood together on a patch of ground about 65 miles northwest of Las Vegas. They'd marked the spot "Ground Zero. Population 5" on a hand-lettered sign hammered into the soft ground right next to them."See the movie and Krulwich's blog at Five Men Agree To Stand Directly Under An Exploding Nuclear Bomb