In the 1950s and early '60s, a small band of high-altitude pioneers exposed themselves to the extreme forces of space, years before NASA's Mercury 7 mission would make headlines. Led by John Stapp, this project–Project Excelsior–sent one man a record-breaking 102,800 feet above Earth lifted by a balloon. Though largely forgotten, this group of explorers were the first to test the limits of human physiology and ingenuity in high altitutdes.

[text adapted from PBS.org]