A tiny blue-and-white rocket plane glides 44,000 feet above the Mojave Desert. Test pilot Brian Binnie, wearing a helmet and a navy blue flight suit, is focused on the cockpit’s digital instrument display, stealing only quick glances out the vehicle’s 18 little round windows. With the flip of a switch, he fires the rocket motor, igniting nitrous oxide and rubber. The effect is instantaneous and violent: Binnie gets slammed with four Gs as his craft shoots forward like a Sidewinder missile.