Future spacesuits could be made of lightweight stretchy material that shrinks to fit astronauts’ bodies, according to US researchers developing such technology.
A team at the Massachusetts Institute of Technology (MIT) are developing a “second skin” bodysuit containing small, springlike coils that contract in response to heat, which could be used to give astronauts much greater freedom of movement.
An electric current heats the shape-memory alloy (SMA) coils in the suit, causing them to revert to a pre-programmed shape and actively compressing the wearer’s body, thereby providing the kind of pressure required by spacesuits.
‘With conventional spacesuits, you’re essentially in a balloon of gas that’s providing you with the necessary one-third of an atmosphere [of pressure,] to keep you alive in the vacuum of space,’ said Prof Dava Newman, who led development of the new suit.
‘We want to achieve that same pressurization, but through mechanical counterpressure — applying the pressure directly to the skin, thus avoiding the gas pressure altogether.
‘We combine passive elastics with active materials. … Ultimately, the big advantage is mobility, and a very lightweight suit for planetary exploration.’
The challenge in designing skin-tight pressurised suits is in making it possible for the wearer to easily squeeze in and out of them. Research Dr Bradley Holschuh came up with the idea of the SMA coils, which can be stretched after they have cooled down, enabling the wearer to remove the suit.
The technology could also be used to create protective suits for military personnel, he said. ‘You could use this as a tourniquet system if someone is bleeding out on the battlefield. If your suit happens to have sensors, it could tourniquet you in the event of injury without you even having to think about it.’
Holschuh considered 14 types of shape-changing materials — ranging from dielectric elastomers to shape-memory polymers — before settling on nickel-titanium shape-memory alloys.
When used to create tightly packed, small-diameter springs, this material contracts when heated to produce a significant amount of force relative to its low mass — making it ideal for use in a lightweight compression garment.
To transform the alloy from reels of very thin, straight fibre into coils, Holschuh borrowed a technique from another MIT group that previously used coiled nickel-titanium to engineer a heat-activated robotic worm.
The fibre was would into extremely tight, millimetre-diameter coils and then heated to 450°C to set them into an original, or “trained” shape. At room temperature, the coils may be stretched or bent but at a certain “trigger” temperature (in this case 60° C), the fibre begins to spring back to its trained, tightly coiled state.
The researchers then arranged several coils in an array and attached the end of each one to an elastic cuff that then tightened when a voltage was applied to the coils.
‘These are basically self-closing buckles,’ said Holschuh. ‘Once you put the suit on, you can run a current through all these little features, and the suit will shrink-wrap you, and pull closed.’
To keep the suit tight would either require a constantly high temperature, which would be uncomfortable for the wearer and require heavy battery packs, or a mechanism to lock or clip the coils in place – and idea the researchers are now studying.
They are also looking at whether to place the coils in the centre of a suit and attach them to threads leading to the four limbs, or to use smaller arrays of coils in strategic locations around the suit.