Spacesuits of the future may resemble a streamlined second skin

September 18, 2014 by Jennifer Chu
The MIT BioSuit, a skintight spacesuit that offers improved mobility and reduced mass compared to modern gas-pressurized spacesuits. Credit: Jose-Luis Olivares/MIT

For future astronauts, the process of suiting up may go something like this: Instead of climbing into a conventional, bulky, gas-pressurized suit, an astronaut may don a lightweight, stretchy garment, lined with tiny, musclelike coils. She would then plug in to a spacecraft's power supply, triggering the coils to contract and essentially shrink-wrap the garment around her body.

The skintight, pressurized would not only support the astronaut, but would give her much more freedom to move during . To take the suit off, she would only have to apply modest force, returning the suit to its looser form.

Now MIT researchers are one step closer to engineering such an active, "second-skin" spacesuit: Dava Newman, a professor of aeronautics and astronautics and engineering systems at MIT, and her colleagues have engineered active compression garments that incorporate small, springlike that contract in response to heat. The coils are made from a shape-memory alloy (SMA)—a type of material that "remembers" an engineered shape and, when bent or deformed, can spring back to this shape when heated.

The team incorporated the coils in a tourniquet-like cuff, and applied a current to generate heat. At a certain trigger temperature, the coils contract to their "remembered" form, such as a fully coiled spring, tightening the cuff in the process. In subsequent tests, the group found that the pressure produced by the coils equaled that required to fully support an astronaut in space.

"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," says Newman, who has worked for the past decade to design a form-fitting, flexible spacesuit of the future. "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 coil design was conceived by Bradley Holschuh, a postdoc in Newman's lab. Holschuh and Newman, along with graduate student Edward Obropta, detail the design in the journal IEEE/ASME: Transactions on Mechatronics.

An original active tourniquet design, combining shape memory alloy (SMA) actuators with 3-D printed structures (the cream-colored plastic) and passive fabric (the white strip). Credit: Jose-Luis Olivares/MIT

How to train a spacesuit

While skintight spacesuits have been proposed in the past, there's been one persistent design hurdle: how to squeeze in and out of a pressurized suit that's engineered to be extremely tight. That's where may provide a solution. Such materials only contract when heated, and can easily be stretched back to a looser shape when cool.

To find an active material that would be most suitable for use in space, 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 trained as tightly packed, small-diameter springs, this material contracts when heated to produce a significant amount of force, given its slight mass—ideal for use in a lightweight compression garment.

The material is commonly produced in reels of very thin, straight fiber. To transform the fiber into coils, Holschuh borrowed a technique from another MIT group that previously used coiled nickel-titanium to engineer a heat-activated robotic worm.

Shape-memory alloys like nickel-titanium can essentially be "trained" to return to an original shape in response to a certain temperature. To train the material, Holschuh first wound raw SMA fiber into extremely tight, millimeter-diameter coils then heated the coils to 450 degrees Celsius to set them into an original, or "trained" shape. At room temperature, the coils may be stretched or bent, much like a paper clip. However, at a certain "trigger" temperature (in this case, as low as 60 C), the fiber will begin to spring back to its trained, tightly coiled state.

Two shape memory alloy (SMA) coil actuators, shown in their stretched and contracted states. Credit: Jose-Luis Olivares/MIT

The researchers rigged an array of coils to an elastic cuff, attaching each coil to a small thread linked to the cuff. They then attached leads to the coils' opposite ends and applied a voltage, generating heat. Between 60 and 160 C, the coils contracted, pulling the attached threads, and tightening the cuff.

"These are basically self-closing buckles," Holschuh says. "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."

Keeping it tight

The group's next challenge is finding a way to keep the suit tight. To do this, Holschuh says there are only two options: either maintaining a constant, toasty temperature, or incorporating a locking mechanism to keep the coils from loosening. The first option would overheat an astronaut and require heavy battery packs—a design that would significantly impede mobility, and is likely infeasible given the limited power resources available to astronauts in space. Holschuh and Newman are currently exploring the second option, looking into potential mechanisms to lock or clip the coils in place.

As for where the coils may be threaded within a spacesuit, Holschuh is contemplating several designs. For instance, an array of coils may be incorporated into the center of a suit, with each coil attached to a thread that radiates to the suit's extremities. As the coils activate, they could pull on the attached threads—much like the strings of a puppet—to tighten and pressurize the suit. Or, smaller arrays of coils could be placed in strategic locations within a spacesuit to produce localized tension and pressure, depending on where they are needed to maintain full body compression.

Several actuators aligned into a 3-D-printed cartridge structure, paired with passive fabric to form an active tourniquet, and mounted on a rigid object approximating a human limb. Credit: Jose-Luis Olivares/MIT

While the researchers are concentrating mostly on applications in space, Holschuh says the group's designs and active materials may be used for other purposes, such as in athletic wear or military uniforms.

"You could use this as a tourniquet system if someone is bleeding out on the battlefield," Holschuh says. "If your suit happens to have sensors, it could tourniquet you in the event of injury without you even having to think about it."

"An integrated suit is exciting to think about to enhance human performance," Newman adds. "We're trying to keep our astronauts alive, safe, and mobile, but these designs are not just for use in space."

Explore further: MIT seeks funding for elastic spacesuit

More information: "Low Spring Index NiTi Coil Actuators for Use in Active Compression Garments." Holschuh, B Obropta, E. ; Newman, D. Mechatronics, IEEE/ASME Trans, Volume: PP Issue:99, DOI: 10.1109/TMECH.2014.2328519

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5 / 5 (1) Sep 18, 2014
Seems like one could turn the problem around--use the memory springs as a release mechanism. Have the suit inherently tight and form-fitting as is, but attach a power source when suiting up to release tension, step into the suit, then turn the power off and disconnect as the elastic components pull the suit back tightly around you. The springs would basically be a shoe horn just to hold things open enough to get in. The power source would remain at the suit up area...

Another thought would be to wrap the suit in a separate jacket with appropriate seals, and a vacuum could be pulled within that space causing air pressure within the suit cavity to push against the inside and make it larger--essentially the opposite of a g-suit. Step in, release the vacuum, and step out of the chamber.

Just throwin' stuff out there...
I Have Questions
5 / 5 (4) Sep 18, 2014
How would they deal with the heating and cooling needed by astronauts in space?
5 / 5 (1) Sep 18, 2014
@I Have Questions-- My guess would be that they would still need an outer layer or layers--for environmental control, micrometeorite protection, attachment points for helmet/gloves or whatever, etc. It just (perhaps) wouldn't need to be airtight, or made of a dozen layers including an air bladder, or even one piece for that matter. I could see how things could be easier this way, by essentially turning the current suit inside out and eliminating the bubble of air that so hinders astronauts' movements today because of having to overcome that pressure-induced stiffness...
3 / 5 (2) Sep 18, 2014
How would they deal with the heating and cooling needed by astronauts in space?

The method currently used could still apply (running water tubes throughout the fabric)
A power pack will still be needed in any case (communications. HUD, oxygen supply, water pump, ... ) and the backpack and helmet will remain. Though the latter might be replaced with a smaller goggle/nose/mouthpiece set.

A skintight suit will likely also lose most of the radiation protection capabilities afforded by old style EVA suits (which isn't much...but still).
not rated yet Sep 18, 2014
@Bradley Holschuh: instead of running the coils along the surface of the material, try sandwiching shorter, wider versions between two parallel layers, with the axis perpendicular to to the layers, so that, in the "relaxed" mode, they can expand and push the two layers apart. When heated to return to their trained shape, they will contract and draw the two layers together.

If the "sandwich" is wrapped around a body, when relaxed, the springs pressure will be constrained by the top, now outer layer, or material, so the body inside the lower, now inner layer will be under pressure.

To remove the sandwich, simply heat, the springs retract and the pressure is released, enabling the body to take off the sandwich.

It will take some engineering to get this right, but I imagine a spring with only one or two turns, made out of a flattened strip of alloy about 5 - 10 millimeters wide and 1 millimeter thick.

Good luck!
not rated yet Sep 18, 2014
@Bradley Holschuh: think of chain mail made sandwiched between two layers of polymer, with short, fat springs instead of metal links.
not rated yet Sep 18, 2014
Active materials are a great idea, but this system uses heat to cause the material to contract. This is fine for a prototype, but in practice it won't be such a good idea.
1 / 5 (1) Sep 19, 2014
Where will they put their MAGs in a suit like that? And, will the suit squeeze out bodily fluids and/or prevent the MAG from functioning optimally?
3.7 / 5 (3) Sep 19, 2014
Well that explains this outfit

-One can imagine that these suits could eventually be 3D printed directly onto the skin with multiple layers for environmental control, insulation, muscle augmentation, sensory extension, power generation and storage and the like, and removed with exposure to a gas or specific EM radiation at a specific frequency, or simply peeled off robotically.
not rated yet Sep 22, 2014
There's an extremely simple mechanical solution to the question:


When the active and passive springs provide equal force, the fabric pulls equally in both directions, but, if you make a tube or a sleeve out of the material with the active springs along the sleeve, using power to make them contract would make the tube wider and shorter, releasing the compression and essentially squeezing whatever is in, out. An astronaut would push their limb in and disconnect the power, whereupon the material would stop pushing back lenghtwise and start squeezing the limb sideways.

It's basically the chinese handcuffs in reverse.

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