Sixty miles up, you sit in a chair on the open deck of a small rocket, admiring the stars above, the Earth far, far below. The vacuum beyond your visor is cold, but it would boil your blood if your pressure suit failed. You give your parachute straps a reassuring pat. It’s utterly silent. Just you and your fragile body, hovering alone above the Earth. “Space Diver One, you are go,” crackles a voice in your ear, and you undo your harness and stand up. There’s nothing for it now: You paid a lot of money for this. You breathe...