The Mercury balloon experiment was an experience performed during two missions of the program Mercury. It consisted in a 30-inch balloon of 30 gores of Mylar and aluminum foil material and inflated with nitrogen. It was divided into five equal size lunes composed of uncolored aluminum foil, yellow and orange Day-Glo, flat white paint, and phosphorescent paint. Once ejected out of a spring-loaded door by the firing of an electric squib, it would be trailed attached to a 100 feet nylon line by the capsule. The balloon, the inflating bottle, and shock absorber was packaged between two balsa wood half cylinder shells in a metal cylinder and mounted in the capsule's antenna fairing.

A strain gauge in the antenna canister will measure differences in atmospheric drag between the perigee (100 miles) and the apogee (160 miles) of the orbit. Another part of the experiment was related to visual data, evaluating the relative merit of various colors for optimum visibility in space at short and long ranges.

The first test was carried out during the Mercury-Atlas (MA-7) mission launched into earth orbit from Cape Canaveral by an Atlas rocket on May 24, 1962. Onboard the Aurora 7 spacecraft was the astronaut Scott Carpenter as the pilot. The balloon failed to inflate properly so no valuable data was obtained.

The second one was performed nine hours into the flight of Mercury-Atlas (MA-9) mission piloted by the astronaut Gordon Cooper on May 15, 1963. During the sixth orbit the pilot tried to eject the balloon package, but nothing happened. He tried again, and still nothing happened. Because the antenna canister was later lost, no one ever knew why the tethered balloon failed to eject.