dr. labuza. why would one want a long shelf life for space foods? these astronauts were only up there for days to maybe several weeks. the foods had to be produced six months ahead of time. we never knew when a rocket was going off. they had food in storage. we wanted to make sure it was still good, so we had to study the rate at which the quality was lost and package it a way that minimized rate of quality loss. to review... in any chemical reaction, substances are transformed into completely different substances. the natural direction of a chemical reaction is determined by the tendency to go in the direction of lower energy and higher entropy. in an exothermic reaction, energy is released. in an endothermic reaction, energy is absorbed. the speed of a chemical reaction is determined by the nature of the substances involved, as welas their concentration and temperature. a catalyst is a substance that increases the rate of a chemical reaction. sometimes, as in the case of preserving food, it is necessary to slow down a chemical reaction. you know,