Fifty-five years ago today, five Army officers and a photographer stood directly under a 2-kiloton atomic blast at the Nevada Test Site, about 65 miles northwest of Las Vegas, and survived.

The five officers, who volunteered for the duty, and the cameraman, who did not, designated the July 19, 1957, test site with a hand-lettered sign as "Ground Zero, Population 5," KPLU, a Seattle/Tacoma-based NPR station, said in a story marking the 55th anniversary of the blast.

The intent of the Cold War test was to film the officers surviving the blast and convince U.S. military leaders of the time that using low-grade nuclear missiles in the air would be relatively safe for people on the ground, KPLU reported.

A movie, obtained from government archives by AtomCentral.com, shows two F-89 jets zooming into view and one shooting off the missile carrying the atomic warhead. The officers are shown waiting during a countdown for the missile to detonate 18,500 feet above them. One officer, wearing sunglasses, looks up as the warhead explodes, at first in silence, followed by a roar, after which the sky goes black and the air turns to fire.

The movie narrator shouts: "It's happened! The mounds are vibrating. It is tremendous. Directly above our heads!"

KPLU said the film was shot at the direction of Col. Arthur B. "Barney" Oldfield, public information officer for the Continental Air Defense Command in Colorado Springs.

KPLU listed the test participants as Col. Sidney Bruce, Lt. Col. Frank P. Ball, Maj. Norman "Bodie" Bodinger, Maj. John Hughes, Don Lutrel, and photographer George Yoshitake.

KPLU said it looked for death records on the five officers and said that as far as it could determine, at least two of them lived relatively long lives.

The test was one of many that the government conducted with live participants in close proximity to nuclear blasts or to ground zero directly after explosions. In a 2010 interview in The New York Times, Yoshitake spoke about the effect of the tests on cameramen like himself who chronicled the events.

"Quite a few have died from cancer," said Yoshitake, then 82. "No doubt it was related to the testing."