How we'll move from place to place in the future will be determined by what passengers can withstand. How fast can the body accelerate? How long can it sit in one place? How many can we pack into a vehicle? Right now we have only a rough sense of these corporeal limits.
Much of what we know is drawn anecdotally from the violent, often accidental experiences of airmen and astronauts. In 1966 a test pilot named Bill Weaver managed to eject when his SR-71 Blackbird broke apart at Mach 3.18. His systems officer was killed, but at 78,000 feet Weaver survived more than 2,000 mph of air resistance, revealing that a human can in fact withstand incredible shock at a very high altitude, at least when protected by a pressurized suit.
In 1960, Air Force captain Joseph Kittinger established as-yet-unbroken records for the highest parachute jump (102,800 feet) and the fastest human free-fall through the atmosphere (614 mph). And between 1947 and 1954, Air Force colonel John Stapp, part of the Aero Medical Laboratory of the Wright Air Development Center, subjected himself to repeated tests on a rocket sled that zipped across what is now Edwards Air Force Base. During one run on his “human decelerator,” Stapp went from 630 mph to a complete halt in just a few hundred feet, experiencing 46 Gs of deceleration.
But standardized data about human tolerances is hard to come by. J.D. Polk, NASA’s chief of space medicine, knows a great deal about the strain of space travel—his astronauts have endured hours of waiting at the launch pad and lived for months in a weightless environment—but even he can’t quite name the breaking point of a human being. That’s because engineers can’t test humans the way they can other components of a spaceship. In designing a space shuttle, “you can stress a part until it breaks,” Polk says. “The human body is the only system in engineering that you can’t take to failure.”single page
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.