“Crumbs are a huge issue,” explains Sebastian Marcu, co-founder of Bake in Space—a German company aiming to make bread that can be consumed in the cosmos. “On Earth, crumbs will land in your toaster tray. But in microgravity, they fly around with no way to contain them.” Midway into the flight of Gemini 3 in 1965, American astronaut John Young discovered the potential danger when he pulled out a corned beef sandwich that he had smuggled aboard (perhaps it had seemed more appealing than the rehydratable hot dogs and prepared food cubes that he had been sent to test). Young quickly realized that free-flying crumbs could land in astronauts’ eyes or throats, or make their way into equipment. He never got to eat his sandwich. It was the first—and, until now, last—sandwich to ...