It must be odd indeed for astronauts, munching on a tough-looking freeze-dried Neapolitan ice cream block while the real Naples glides gracefully past (along with the entire 'boot' of Italy) some 200 miles below. It must be frustrating, too, to know that all that real ice cream is tantalisingly out of reach. Yet, by simply tearing open the foil outer and popping the freeze-dried block into the mouth (thereby re-hydrating it in the process) they find that, more often than not, the unappetising-looking substance explodes with flavour. That makes these authentic all-American astro-snacks a technological marvel in their own right.

They don't look like real food, yet taste like real food. How can this be? Freeze drying is the process that has been applied to astronaut food since the early days when eating the right stuff was as important as having it. It's a fiendishly complex process that can be summarised thus: The ice cream is placed in a vacuum chamber and frozen until the water crystallises. The air pressure is lowered, forcing air out of the chamber. Next heat is applied, vaporizing the ice. Finally, a freezing coil traps the vaporised water. This process continues for hours, resulting, over time in a perfect freeze-dried ice cream slice. So now you know. All of the goodness. All of the flavour. Yet none of the water content. Amazing.