Mason Peck, NASA’s former chief technologist, is on a mission to make space more accessible to all. What if anyone could print a satellite in space, using asteroid or lunar material? Or jet from the Earth to the Moon—and beyond—using just the hydrogen found in a two-liter bottle of water? Together with his colleagues at Cornell, Peck is developing cracker-sized satellites called “sprites,” a solar-powered hydrogen engine, and other technologies that may some day democratize space exploration.