Space Activity Suit - Construction

Construction

The original SAS design was based on two new fabrics: a type of "powernet" (or "girdle fabric") for high-tension areas, and an elastic bobbinet weave for lower-tension areas. Both were based on a heavy elastic warp thread with a much less elastic weft thread to form a netting. The terms warp and weft are used loosely here, as the material was not woven using traditional means. Powernet used spandex cord as the warp with nylon cord as the weft, allowing movement primarily along the warp axis. Bobbinet used cotton-wrapped rubber warp and nylon or dacron weft, and was flexible in both directions. The cotton wrapping limited the maximum stretch to 200% of the rest length. The amount of over-pressure bobbinet could create was about 2.0 kilopascals (15 mmHg; 0.29 psi) over the torso, the largest volume, and up to 5.3 kilopascals (40 mmHg; 0.77 psi) over smaller radius curves on the wrist and ankles. Powernet could produce about 6.7 kilopascals (50 mmHg; 0.97 psi) even on the torso. A minimum of 17.3 kilopascals (130 mmHg; 2.5 psi) is needed for normal breathing.

Multiple layers and patches of the two materials were used to control the overall mechanical pressure around the body. Starting at the skin, a "slip layer" of light powernet was used to allow the outer layers to slide over the skin without binding. Under this layer a number of foam pads were placed on various concavities on the body to keep them in contact with the suit. On top of this was the counter-pressure bladder, part of the breathing system. On top of this were up to six additional layers of powernet over the trunk with bobbinet arms and legs, or all-bobbinet garments covering the trunk only. The garments were put on like a normal bodysuit with a large zipper closing the front, with additional drawstrings at some points to help close the garment. Zippers on alternating layers were offset.

The positive-pressure breathing system consisted of three main portions: the pressurized helmet, the breathing bladder, and the tankage system in a backpack. The bladder and helmet were connected together to pump air out of the bladder and over the torso when the user breathed in, reducing the amount of pressure on the user's chest. The helmet was secured by means of a non-elastic garment of Nomex cloth which wrapped around the chest and under the under the arms, and by the elastic layers above and below it.