On the Threshold of Space [1956] [DVD]

From imdb: During the 1950s, with the advent of faster jets and bombers that could fly higher, the problem of a safe bail-out system arises. Also, a looming space-race against the Soviets forces the U.S. Air Force to design and test ejection systems that could be used in experimental planes or future spacecraft. Can a human withstand the blunt physical forces at play during an ejection from a high-flying aircraft and also during the rough descent toward the earth ? That's where aerospace medicine comes-in. Capt. Jim Hollenbeck, a doctor working for the space branch of the United States Air Force Medical Corps, is sent to Sovern Air Force Base in Florida to test a faulty experimental ejection seat.

A series of tests and evaluations at supersonic speed follow. The head of the program, Dr. Hugh Thornton, also tests a rocket sled launched at 1,000 miles per hour to evaluate the human-body endurance and recovery. Capt. Jim Hollenbeck is asked to test a balloon gondola designed to carry a human 20 miles up into the stratosphere. From a height of 100,000 feet, the test-pilot parachutes down to earth in a spherical capsule. Being at the threshold of space this experiment could provide the basis for sending a man into space. The new officer in charge of the program, Maj. Ward Thomas, is a more cautious man who doesn't want any mishaps or fatalities that could jeopardize the whole program.

After many trial-and-error experiments, Washington D.C. authorizes a floating high-altitude platform. Thus, a test-pilot could evaluate the survivability of such an ascent and eventual parachuted-descent to earth. To the horror of his new wife, Pat, Capt. Jim Hollenbeck volunteers for the immensely dangerous test.