Here, NASA astronauts-in-training, men at absolutely peak mental and physical condition, undergo grueling tests in . . . oh, wait. Never mind. That’s the self-described overweight and out-of-shape LIFE magazine Science Editor Warren R. Young, who flew with aviators during zero-gravity tests in 1959. The Soviets had, of course, launched the first artificial satellite, Sputnik I, in 1957, and the race was on to see who would take the next big human step into space: zero-gravity training was a key part of the preparation for space travel.

Young had the rare opportunity to experience zero-G training with the aptly named Zero Gravity Experiment, in a modified transport plane dubbed How High the Moon. And how does it feel to literally float several feet above a solid surface? Young reported that potential astronauts should look forward to a blissful sensation, while preparing for confusion. What’s up? What’s down?

He was also “astonished to find that the world of weightlessness actually feels more natural than our customary gravity-controlled realm,” while zero gravity “seems to give simultaneous buoyancy to both body and spirit.” Even the old hands on board had wide smiles each time How High the Moon “zoomed up into a ballistic curve that counterbalanced gravity” (see video below). Each of the tough Air Force men, Young wrote, smiled like a child on a trike. They felt a kind of awe, and the experience never got old.

[WATCH: LIFE magazine’s Warren Young revels in weightlessness]

Delia Mandia is a native New Yorker and NYU undergraduate student whose passion is her global nonprofit organization, Night Night Monster. She also enjoys competitive gaming (she is world-ranked) on her custom built hydro-cooled PC, and attending Stargate conventions.