A few years ago a company by the name of AirLaunch had a novel idea for a rocket—put it in a C-17 cargo plane and then slide it out the back at high altitude. The rocket would rotate until it was vertical and then fire, heading into orbit. You can watch video of the drop tests. “We examined a wide variety of propellants ranging from storable hypergolics, RP/LOX, to fluorine/deuterium.” That may sound exotic, but Ehrlich joked that “this was a paper study!” Now imagine that instead of a relatively small rocket, there was a much larger rocket, with a...