A space activity suit is a kind of spacesuit, which provides mechanical pressure by means of elastic garments as opposed to pressurizing the suit with the breathing gas, as is standard practice in regular suits.

History

Original research was done by Paul Webb, who in 1968 published a paper titled "The Space Activity Suit: An Elastic Leotard for Extravehicular Activity" in the April 1968 issue of Aerospace Medicine. Research was funded by NASA.

In 1971, Webb, along with James F. Annis, published NASA CR-1892, "Development of a Space Activity Suit", including experimentation with a human volunteer put into a low-pressure chamber to exercise and perform tasks requiring manual dexterity. The results were positive, and the researchers felt that further improvements were possible.

NASA discontinued research into the space activity suit, and pressurized suits are still used as of 2005. However, research is under way at the Massachusetts Institute of Technology (MIT) on a Bio-Suit System as a preparation to president Bush's new space vision.

Technology

A space activity suit consists of a pressurized bubble helmet (much like those in fully pressurized spacesuits), a positive-pressure breathing system, and an elastic leotard, which provides mechanical counterpressure to the body. The main difference from a pressure suit is that the counterpressure to the surface of the body is provided by an elastic non-airtight fabric instead of gas pressure (amazingly our skin is actually quite airtight).

This has certain advantages: Cooling is accomplished by the evaporation of sweat through the fabric (instead of water cooling systems). The unpressurized and elastic suit allows finer and less laborous movements (which leads to less fatigue and more manual accuracy), has less mass and is much simpler. It is also thought to be safer, since isolated damages to the suit may lead to localized skin swellings or injuries, but not to general (deadly) decompression.

Quoting the NASA Contractor Report from 1971:

In conclusion, the SAS at its present stage of development will protect man from the effects of the vacuum environment, in a garment, which permits improved mobility and natural body movements. Physiologically the approach is sound, and although there remain many problems to be solved, they are principally mechanically in nature. It has been suggested that solution of the mechanical problems, combined with careful tailoring based upon biomechanical analysis, plus the development of specific elastic fabrics, could eventually lead to a space qualified version of the SAS.