Freeze drying is like sending food into suspended animation. It looks dry and feels dry to the touch, yet, by simply tearing open the foil outer and popping the freeze-dried block into the mouth (thereby re-hydrating it in the process) astronauts find that, more often than not, the unappetising-looking substance explodes with flavour. All of which makes this authentic all-American astro-snack a technological marvel in its own right.

It doesn't look like real ice cream, yet tastes like ice cream. It can even be stored for years without refrigeration, so long as it remains in its foil wrapper. 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 that keeps the ice cream totally intact, minus any moisture. Amazing.