The International Space Station (ISS) orbits 250 miles above Earth, so when astronauts start hankering for pizza, they can’t exactly call out for delivery. A crispy crust is a must, but NASA had to consider the weightlessness of space and the safety hazard of crumbs drifting into air vents or expensive equipment when trying to create a pizza that is safe for life on the ISS.

In its search for space pizza, NASA gave the first round of funding to a small Texas business to build a 3D food printer and one of its first recipes was printing pizzas in layers, starting with the dough, then the sauce, and finally the toppings. Apparently, the printed pizza didn’t meet NASA’s requirements because they never provided a second round of funding.

Today, astronauts on the ISS have pizza on the menu. Space pizza is pastes and sauces that are spread onto pre-made dough, and toppings that must stick to the sauces; the pizzas can be warmed up, but a truly crispy crust isn't possible. Restrictive diets tend to change people's perspective on what constitutes "good" food, and astronauts learn to appreciate whatever they can get.