The Plumbbob Charleston shot was a 12 kiloton test of a balloon lofted device detonated a 1,500 ft. over the Nevada desert on September 28, 1957. The design of the UCRL Charleston device posed some delicate public relations problems for the AEC before the shot. Its predicted yield range was from 10 to 100 kilotons, with the most probable yield between 50 and 60 kilotons. The high end of the yield range was well above that for any device fired to date in Nevada.

In addition, there was a possibility that more than half of the yield of the Charleston device might come from fusion processes.