Our stereotype of a spacesuit involves an astronaut clad in a bulky white outfit like some outer space Michelin Man wearing a rucksack – and about as graceful. But if an MIT team has any say, the spacesuit of the future will be a snug, form-fitting outfit that’s not only lighter and more flexible but also easier to get on, automatically tightening up to a proper fit at the touch of a button.
Spacesuits are vital if space explorers are ever going to do more than just stare out the porthole, but making a suit capable of keeping a human being alive in the vacuum of space is much more involved than just slapping on a fish bowl and a couple of air bottles.
A spacesuit is a complex system that’s more like a flexible spaceship than a bit of airtight tailoring. The suit itself is a complex assembly of layers designed to keep in air at a reasonable fraction of atmospheric pressure, along with billows and pleats that allow the wearer to move about with some degree of freedom, and the backpack – that is a fantastic feat of engineering – made up of tanks, cooling systems, air scrubbers, pumps, and everything else needed to support life.
That is pretty much what spacesuits, or pressure suits, have been like since the days of the Apollo program, but it’s never been a very good solution. Pressure suits are bulky, cumbersome, as hard to move about in as a hardhat diving suit, and not very comfortable.
Part of the reason for this is the need to inflate the entire suit with air, which introduces all sorts of engineering challenges that are far from solved after some 80 years of development. However, there is an alternative.
Back in the 1960s, NASA realized that human skin is actually pretty tough stuff. It’s very good at keeping in pressure, which is why (along with some suspension of disbelief) Peter Quill (AKA Star Lord) can jump into space in Guardians of the Galaxy wearing nothing but a breathing mask without exploding. The space agency reasoned that if it could come up with a suit based on skin, the result would be much lighter and flexible – more space leotards than suits.
The result was the experimental Space Activity Suit (SAS), pictured above. Instead of an air-filled envelope, the SAS used a skin-tight rubber leotard that clung to astronaut like spandex, pressing in to protect the wearer from the vacuum of space by means of counter pressure. For breathing, the astronaut wore a simple helmet with an airtight ring seal to keep in pressure, and the suit had an inflatable bladder on the chest to keep the wearer’s lungs from blowing up like a balloon.
This setup made for a much lighter, more flexible suit that was mechanically far simpler because the breathing system needed to be no more complex than a scuba set, and the rubber could be made porous enough to allow sweat to penetrate and evaporate, which removed the need for complex cooling systems.
The snag with the SAS was that materials in the days of Apollo were much too primitive to make the design practical. In recent years, a team led by Dava Newman, a professor of aeronautics and astronautics and engineering systems at MIT, came up with the Biosuit, which uses modern fabrics, computer modelling, and engineering techniques to produce an updated and more practical counter-pressure suit.
But there was still a big problem. True, the Biosuit was very good at protecting a prospective astronaut, but its skintight design made it almost impossible to put on. It’s so tight that it makes a neoprene wetsuit seem like a set of oversized dungarees. All sorts of solutions were proposed, such as a computerized machine that would weave a new suit about the wearer when needed. That sort of arrangement for getting dressed might suit Iron Man, but as a practical system, it left much to be desired.
MIT’s new approach is a next-generation version of Newman’s Biosuit, that goes on loose like a pair of coveralls, but when an electric current is applied, tightens up for the proper snug fit. This way, the suit would be both lighter and simpler than a pressure suit, and easy to don.
The new approach incorporates coils formed out of tightly packed, small-diameter springs made of a shape-memory alloy (SMA) into the suit fabric. Memory alloys are metals that can be bent or deformed, but when heated, return to their original shape. In this case, the nickel-titanium coils are formed into a tourniquet-like cuff that incorporates a length of heating wire. When a current is applied, the coil cinches up to provide the proper counter pressure needed for the Biosuit to work.
The technique for forming the coils was borrowed from another MIT project to create a robotic worm. This involved "training" the SMA by heating it to 450º C (842º F) and then bending it into the desired shape. When the coil cooled to room temperature, it could be stretched out, but when heated to 60º C (140º F), it shrank back into its original shape in what the MIT team compared to a self-closing buckle.
In fact, buckles are what the team are currently concentrating on. By using various configurations of the coils along with tendon-like threads for tightening the suit over the torso, the Biosuit can provide the proper amount of counter pressure. In order to maintain it without continually heating the coils, however, the team needs to come up with some sort of a catch that will lock the coils in place rather than relying on a continuous supply of electricity and needlessly heating up the suit – yet it will still have to be easy to unfasten.
Beyond this, the team sees the coil technology as having earthbound applications as well, in everything from athletic wear to military fatigues
"You could use this as a tourniquet system if someone is bleeding out on the battlefield," said Bradley Holschuh, a postdoc in Newman’s lab, who conceived the coil design. "If your suit happens to have sensors, it could tourniquet you in the event of injury without you even having to think about it."
The MIT team results were recently published in IEEE/ASME: Transactions on Mechatronics.