The Bio-Suit
The Bio-Suit was a novel approach to spacesuit design that used and biomedical breakthroughs in skin replacement and materials to replace the bulky conventional "balloon" spacesuit with a 'second skin' approach to provide light weight, flexibility, and comfort in all extraterrestrial environments.
It provided life support through use of mechanical counterpressure applied to the entire body through a tight-fitting suit, excepting a helmet for the head. The inner layer of the Bio-Suit could be sprayed on, and disposed of, together with dirt and dust, after each EVA. The external layers would include embedded "wearable technologies" that would be tailored to the environment and mission.
Existing space suits used hard fiberglass or metal and soft fabric components. Mobility was obtained by pleats that opened as joints bent and rotational bearings. These suits, all derived from the very fist purpose-designed spacesuits of the 1960's, were heavy, bulky, restricted astronaut mobility, and required extensive special training and exhausting joint torque force to work in.
A modern Mechanical Counter Pressure (MCP) suit, first studied by NASA in 1971 as the Space Activity Suit, would eliminate these difficulties. The Bio-Suit study did not identify a specific design, but rather identified candidate technologies for the suit layers and the embedded information systems. These included:
- Electric Alloy Mesh Concept, using a seamless Shape Memory Alloy mesh to generate voltage-controlled mechanical counter-pressure. Pressure would be distributed by a viscous thermal-regulating gel layer. The gel layer moderated the high temperature of the SMA later and protected the body against impacts the skin directly, wicking away perspiration and absorbing body heat.
- Thermal Gel Suit Concept, using "smart" polymer gels which expanded at a threshold temperature to create mechanical counter-pressure. The smart gel was trapped in a quilted layer beneath a stretchless restraint layer. The restraint layer prevented outward expansion of the gel, directing the pressure inwards against the body.
- Electric Gel Suit , using "smart polymer gels which expanded in an electric field to create mechanical counter-pressure. The smart gel was trapped in a quilted layer, between metallized fabric layers, beneath a stretchless restraint layer. Opposite charges applied to the metallized layers produced a small electric field sufficient to stimulated the expanding smart gel.
- Stretch Alloy Band Suit Concept using the super elastic properties of Shape Memory Alloys (SMA) to allow the suit's volume to expand enough for donning. Charge would then applied to the SMA band which pulled together the seam of a uni-directional stretch fabric layer, which was able to stretch longitudinally in order to allow flexion at the joints.
- Electric Alloy Zipper Suits using shape memory alloy strips to aid and control the application of mechanical counter pressure while manually zipping together seams in a uni-directional stretch fabric layer.
- Electric Alloy Remote Zipper Suit concept, as the previous concept, but instead of being zipped manually, tightened all at once by digital controls at the shoulders. This system assured uniformity of mechanical counter-pressure and ease of operation.
The study also looked at various alternatives for thermal control: - Absorb concept, which would collect perspiration in a removable component within the suit, either a highly absorptive fabric layer similar to long underwear, or desiccant packs at critical locations.
- Vent-to-Atmosphere concept, which controlled perspiration by venting moisture directly to the outside environment. A selective, semi-permeable organic layer closest to the skin allowed perspiration to pass through at a moderate rate. Subsequent layers of the suit, including the mechanical counter-pressure layer, were also semi-permeable. The openings in the membranes were large enough to allow the suit to breath, but small enough to prevent unwanted fluid loss.
- Transport concept, using a layer of tiny tubes to channel perspiration away from the body to a remote collection point. These tubes might be manufactured or perhaps organic such as the aquaporin network in plant membranes. A partial vacuum at the collection end might moved perspiration through the tubes, or perhaps work would be done by tiny piezoelectric pumps powered by energy harvested from body motion.
An advanced possibility was that the suit layers could be sprayed directly on the astronaut's skins prior to EVA. Electrospinlacing, involving charging and projecting of tiny fibers of polymer directly onto the skin, could be used.
Melt blowing of liquefied polymer could be used to apply thin elastic layers. Application could be made directly to the skin, or to advanced 3D forms generated by laser scanning. Wearable computers, smart gels and conductive materials could be embedded between polymer layers.
The MIT research team, led by aerospace engineer Dava Newman and including Hoffman and students, has begun designing a space outfit called the Bio-Suit System. The new suit will be lightweight and flexible, but will still protect astronauts from the hazards of outer space.
UNDER PRESSURE
The most critical feature of any space gear is the ability to maintain pressure around the astronaut's body when he or she steps out of the cozy confines of a spacecraft.
On Earth's surface, your body is constantly exposed to the pressure of the air molecules in the atmosphere. Pulled down by Earth's gravity, these molecules press against your skin with a pressure of 1 atmosphere, or 14.7 pounds per square inch.
That pressure is critical: All of the tissues and fluids in your body contain essential gases such as oxygen. If the pressure on the outside of your body were to disappear, these gases would separate from your blood and tissues and would try to escape through your skin. "Over the course of 5 to 10 minutes, your skin would start to swell and it would become very painful," says Hoffman. "You can't tolerate that."
BAG IT
In the vacuum of space, there aren't enough air molecules to produce pressure against an astronaut's body.
To protect space explorers, today's spacesuits create air pressure by surrounding an astronaut's body with an air-filled bag. "[Astronauts] are basically wearing a human-shaped balloon," says Hoffman. The gas-filled suit squeezes an astronaut enough to prevent gases from escaping from the body. But as a result, the suit is extremely stiff and difficult to maneuver in. "Particularly in areas like your fingers, you have to work to make the spacesuit move," says Hoffman.
SHRINK WRAP
Instead of relying on an air-filled bag to create pressure, the Bio-Suit System uses tightly fitting fabric to squeeze the skin. The first suit to use this type of mechanical counter-pressure was the Space Activity Suit, created by Paul Webb in the early 1970s. But in order to produce enough pressure on the skin, the suit was made up of more than five separate skintight suits layered on top of one another. "It took over half an hour and the help of two assistants to get [the suit] on," says Newman.
How to make a high-pressure suit that's easy to don? Each Bio-Suit will be custom-made: To outfit an astronaut, scientists will use lasers to create a three-dimensional scan of the astronaut's body. Then, the suit will be crafted to perfectly fit those dimensions.
In the future, the Bio-Suit will also be made from "active materials." These materials change shape when electricity is applied to them. That way, the astronaut could easily zip into a one-layer suit. "Then, just before you are about to go outside, you activate the suit and it shrinks around you," says Hoffman. Once the astronaut returns to the safety of a space station, he or she would deactivate the shrinking mechanism to take off the garment.
BONUS FEATURES
In addition to a suit that fits like a second skin, the engineers from MIT hope to design different modules that future astronauts could slip over the outfit to match their daily needs. "You can put on whatever components you need depending on the environment you are working in," says Hoffman. For example: If the astronauts plan on working outside all day, they might slip on jackets that would protect them from collisions with speeding space debris. Or, since the temperature on Mars can dip to a frigid -153 C (-225 F) at the poles, an astronaut may choose to wear an overcoat with electrical heating wires running through it.
Future spacesuits may even help improve the astronaut's work performance. Scientists from other labs are trying to develop artificial muscle Fibers that can contract and expand along with a person's muscles as they move. The Bio-Suit may someday have these artificial muscle fibers sewn into it. That way, when astronauts need an extra boost, they could activate the fibers in the suit to enhance their strength and stamina. "That's a ways off in the future, but it's fun to think about," says Newman.
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