This balloon is one of many parts of the SCR-578 survival radio set that entered service in 1942. It was a common piece of equipment on U.S. Army Air Forces aircraft that flew long-duration missions over open water. An SCR-578 could be placed in a life raft or dropped by another aircraft to aid a downed crew. The full set included a BC-778 radio transmitter (popularly called the “Gibson Girl” for its curved housing) and an 800-foot-long wire antenna. There were two ways to get this antenna airborne — a folding box kite or a balloon if wind conditions prevented use of the kite. This “balloon in a can” is referred to as the Balloon, M-278-A. An included hydrogen generator was attached to the balloon with a tube and then immersed in water, whereby a chemical reaction produced enough hydrogen to inflate the balloon to 4 feet in diameter. Once aloft, the balloon and antenna gave the radio a transmitting range of about 200 miles.