Permanent Human Settlement of the Earth, Space and Ocean Frontiers

Tuesday, December 26, 2006

Space Suits

Ralph Buttigieg

Sydney NSW

Above is a picture of a space shuttle astronaut wearing the Shuttle EMU space suit. The spacesuit is a pressure suit with a heritage going back to 1930's high altitude flights. Pressure suits have been used for decades by all the space faring nations and allowed the Apollo astronauts to explore the Moon.

However if pressure suits are the best we can do we can forget about Space settlements.

A conventional spacesuit surrounds the occupant with a pressurised balloon. The suit will inflate to the originally sewn shape and will want maintain the shape. The astronaut has to fight against the suit to move. Mobility is only possible with the use of constant volume joints. Even with the best pressure suits every movement is remains an effort. The gloves provide special difficulties, fine work is virtually impossible. There are other problems, to keep astronauts cool they have to wear a garment of tubes that pump water around the body. Also any puncture would be fatal.

These suits are complicated, expensive and heavy. The old Apollo Moon suit weighted about 100kg, the Shuttle suit even more, 131kg. Operations on the Moon and Mars are going to be dusty, those joints will need to be regularly cleaned and repaired. The work in maintaining such suits , not to mention the expense will be a severe restraint on even a small settlement. The comparison here is with undersea exploration. Think back to the old hard hat suits, they were dangerous and expensive to use. What is required is the space version of SCUBA gear.

Fortunately there is an alternative. Back in the late 60's Dr Paul Webb developed a revolutionary protective suit called the Space Activity Suit. The SAS was based on the realisation that the human skin is a pretty good barrier to vacuum. A person can be exposed to space for one to three minutes with out serious harm. The body will swell due to gas expansion but this takes several minutes. If the skin could be reinforced there would be no swelling. Dr Webb therefore developed an elastic leotard to provide mechanical counter pressure (MCP). Any swelling is restrained by the elastic garment . The suit needs no joints bending requires minimal effort. There is no need for the complicated cooling garment .either. The leotard can be made from porous material so the astronaut can still sweat away the body's metabolic heat. Even the problem of punctures is reduced, any cut would produce local bruising at most.

Dr Webb was able to successfully take the suit to proof of concept stage. As can be seen from t picture the test subject was able to run on a treadmill!

If you think skin tight leotards are just a bit to sissy for astronauts don't worry. They would well a lose fitting coverall over the leotard to protect them from micro-meteorites and solar radiation.

There are problems with MCP suits the major one being the difficulty of donning the outfit. The original suit required assistance and took about 20 minutes to put on. However that was over 30 years ago, according to Dr Webb new materials allow the suit to be put on by one person in a few minutes.

Dr Webb is still not alone in researching MCP suits, others include Dava Newman from MIT and James Waldie in Australia. Hopefully NASA and others do fund this essential work.