At its simplest, the 3D printing of food takes the form of extruding purees through nozzles that consider the viscosity of the original feedstock, and printing it in additive layers onto a platform. The end result is often dried or baked into a biscuit form. The cognoscenti actually call this 2.5D, as the process involves many 2D layers and only the final product is itself a 3D object.
Another approach is to load up a printer with capsules of ingredients, like inkjet printer cartridges. Supply water, oil and heat and the printer can then combine these ingredients into a finished meal. Indeed, food printers could potentially prepare a wide range of meals from a handful of basic ingredients.
No one becomes an astronaut for the quality of the food, which is notoriously bland, largely freeze-dried and lacking in structure or mouth appeal. To date, space missions have been relatively short or are easily resupplied with food items from Earth. With an eye to...