(I) In the early days of space travel, every pound weight added £ 100 to the cost of the flight. (II) So food had to be as high as possible. (III) One way of making food higher was to remove the moisture from it. (IV) This was realised by a process known as freeze-drying. (V) Frozen food was, of course, deficient in vitamins, which were necessary for the astronauts in harsh conditions.