Theories of spacesuit design

A space suit should permit its user natural and unencumbered movement. The only way this is achievable is for the space suit to maintain a constant volume no matter what position the wearer is in. This is since mechanical work is needed to change the volume of a constant pressure system. If moving an arm or hand causes a change in the volume of the space suit, then the astronaut has to do additional work every time he bends that joint, and he has to maintain a force to keep the joint bent. Even if this force is very small, it can be critically fatiguing to constantly fight against your suit. It also makes delicate movements very difficult.

All space suit designs try to minimize or do away with this problem. The most general solution is to form the suit out of multiple layers. The bladder layer is a chewy, airtight layer much like a balloon. The moderation layer goes outside the bladder, and provides a specific shape for the suit. Since the bladder layer is bigger than the restraint layer, the restraint takes all of the stresses caused by the pressure of the suit. Since the bladder is not underneath strain, it will not "pop" similar to a balloon, even if punctured. The moderation layer is shaped in such a way that bending a joint will cause pockets of fabric, called gores, to open up on the outside of the joint. This makes up for the volume lost on the surrounded by of the joint, and keeps the suit at a constant volume. However, once the gores are opened all the way, the joint cannot be bent any longer without a considerable amount of work.