15 Secrets of Space Suit Design

It’s no secret that astronauts couldn’t survive the harsh environment of space without their suits. But there are plenty of things you might not know about how these suits go from concept to prototype to the final frontier. We asked Lindsay Aitchison, Space Suit Engineer at the Advanced Space Suit Design Group at NASA’s Johnson Space Center, to walk us through the process.

1. Designing space suits requires a particular set of skills.

And they’re not necessarily the ones you might think. Aitchison says the job requires both critical thinking and creativity. “You need to be detail-oriented and come up with a very precise test plan,” she says. “When you’re working with human test subjects, you have to design a test where you get constructive feedback on things that are squishy subjects, like comfort. How do you define comfort? You have to think about it from an engineering standpoint and engineer a suit to be comfortable.” Thinking creatively, Aitchison says, allows her to see how technologies from different fields might be incorporated into space suit design.

2. Suits are crafted for their missions.

When creating a new suit, Aitchison says NASA’s engineers must answer two questions to help them determine the structure of the suit: Where are you going and what are you doing?

The engineers start with where the astronaut is going, which falls into two categories: A micro-gravity location or a planetary environment, where they’ll have to walk (which determines how much mobility they’ll need in their suit). The engineers also consider things like how high radiation might be, the temperature ranges an astronaut will experience, and the risks of micro-meteoroids.

Next, engineers have to think about what astronauts will be doing on their missions: Will they be walking on their hands, as they would in micro-gravity, or walking on their feet, as they would on a planetary surface? Will they be digging with tools, or carrying everything on a toolbelt and performing tasks with their upper body? Will they need to be autonomous? “If you're on a planetary surface, that's pretty far from earth, so we're trying to develop more technologies so that you do autonomously EVAs,” Aitchison says, “whereas [on] space stations, you have a lot more direct contact with the flight control team, so we can offload some of those informatics and rely on flight control to help us.”

3. New Suits Need New Shoes.

EMU suit; photo courtesy of NASA.

The suit most people are familiar with is the Extravehicular Mobility Unit (EMU) suit. Because it's designed for use in micro-gravity—in which astronauts use their hands to move themselves around—to make repairs and modifications to the International Space Station (ISS), telescopes, and more during spacewalks, it needs to have mobility in the shoulders, hands, and arms. "You use the lower area [of the suit] for stability, so that way you have a stable work platform if you're at the end of a robotic arm," Aitchison says. "If it's too loosey goosey, you can't get any work done."

But new space suits, including the new Z-2, are being designed to go to planetary environments, so Aitchison and other designers spent a lot of time focusing on the design of the waist and hip joints—and the shoes. "This is the first time since Apollo that we need to have a walking boot, and when you're walking in different gravity fields, the way you walk changes," Aitchison says. "So we're focusing on how to design a boot to work with how you walk in, say, Martian or Lunar gravity environments. It's very different from the EMU, which is just a hard-soled boot."

To figure out what kind of shoe they'd want on their new suits, Aitchison did a number of walking tests with different suits in 2008. "We had [the suits] offloaded to different gravity weights, so if you were walking on a treadmill, it felt like you were walking at 3/8 gravity or 1/6 gravity because [a rig] was holding up the weight of the suit," she says. The team placed motion capture markers on the lower half of the suit to analyze how the foot, ankle, and hips were moving at different gravities. "We noticed through our testing that people tend to swing their hips up and sort of gallop [in different gravities], so if you pay attention to that, you can figure out where you need to have flexibility versus stiffness in the sole [of the shoe] to make that motion easier."

Though the team is still evaluating designs, Aitchison says that they're currently looking at a hiking boot sole. "It's pretty stiff in the forefoot but it's got some flexibility in the mid foot so you can sort of do those kneeling tasks."

4. The goal is to make new suits lighter.

Apollo suit; photo courtesy of NASA.

The EMU weighs a whopping 300 pounds (the astronauts, of course, don't feel that weight in microgravity). The Apollo suits, including backpacks, weighed 180 pounds on Earth and just 30 pounds on the Moon, by comparison—but, Aitchison says, "they didn't have a lot of mobility to them." The goal for new suits is to make them lighter while maintaining mobility. "When we add mobility, we're talking about adding hard elements like bearings, which make it very easy to work in a pressurized suit but come with a mass penalty," Aitchison says. "So we're trying to figure out low mass solutions for having those hard elements. We're looking at titanium because that saves us about 30 percent of mass on the bearings when we do that. And then [we're] looking at new types of composite materials for the upper torso material and for the hips and the brief section of the suit."

The new Z-2 will be about 20 pounds lighter than the EMU, "which doesn't seem like much," Aitchison acknowledges. "But again, we're adding in all the capability of the lower torso that we haven't had before."

5. Design starts by playing with old prototypes.

Once the where and the what are figured out, it’s time to get down to designing. The Advanced Space Suit Group has prototypes from the last 30 years of suits, as well as shuttle suits and suits from the Apollo era. “We start by testing those suits and understanding the different features,” Aitchison says. “What type of shoulder works best for what type of activity, different designs of the hips and boots and the style of entry. Do you want to have a zipper? All those things.” Playing with those features allows the engineers to sketch out what parts of different suits would be best for a particular mission.

6. NASA Scientists design the suits, but private companies make them.

Two-dimensional rendering of the "Technology" version of the Z-2 suit. Photo courtesy of NASA/Johnson Space Center.

Testing of the suits, and sketching up the designs, happens in house. But when it comes time to build, NASA turns its designs over to private companies. “We write the requirements and give the general concept of what we want built for us, and we have vendors that will build the suits for us, to the specifications that we write,” Aitchison says. The engineers work on one suit at a time, but since the start of Constellation in 2005, they’ve been getting prototypes every three to five years.

7. Certain parts of the suits are hand sewn.

In the Apollo era, space suits were sewn together by hand. You might think, with advances in technology, that this practice would have gone the way of the dodo, but that's not the case.

A little space suit anatomy: The innermost layer of the space suit, called the bladder—"think of that as basically being the balloon that holds all the air inside of it," Aitchison says—is sealed and welded together by a machine. On top of that is the restraint layer, which gives the bladder strength and structure. "It makes sure [the bladder] bends to that specific location and it takes all of the loads of the suit to protect that bladder from too much force when you bend your elbow or if you put pressure onto it," Aitchison says.

The restraint layer is the part of the suit that's still hand stitched. "There is a room full of sewers with different types of sewing machines, depending on what part of the suit they're stitching, and they can do some very precision sewing by hand," Aitchison says. "Like a 16th of an inch in some places, and they are incredible at that." The sewers use specific types of thread for certain locations, depending on whether they need more strength or elasticity in that section.

8. But they're still cutting edge.

Engineers used 3D human laser scans and 3D-printed hardware to develop and size the Z-2 suit—the first time that's ever been done.

9. Suits are allowed to leak.

But not a lot. According to Aitchison, the whole suit is allowed to leak a maximum of 100 SCCM (standard cubic centimeters per minute). To ensure the suit doesn't leak, and that it's meeting the requirements determined by the designers, its parts are rigorously tested during the fabrication process. Seam allowances are measured with rulers, and samples are purposely destroyed to ensure they meet the required strength characteristics. "[Testers] pull out a machine to see how much force it takes to rip either the seam or the fabric itself," Aitchison says.

When the designers receive the full suit, it, too, undergoes testing. "We do structural and linkage testing, which means we inflate the suit to 1.5 times its regular operating pressure—which is 4.3 PSI when we're doing a space walk—to make sure that it's structurally sound, we're not seeing any windowing at the seams or have any leaks," Aitchison says. "And then after we do the structural [test], we go back down to regular operating pressure and redo the leak check."

10. There are no custom space suits.

It's not cost effective to build one suit for every crewmember. Instead, the suits are constructed using a modular system, which is part of why they're so bulky. "When you have mix and match components, we tend to make it a little bit larger, so that we can fit a wider population of people," Aitchison says. "We have different components—basically small, medium, large sorta fit—so we can mix and match components between different sized crew. That way it helps us with logistics and with redundancy on the space station, too." (Currently, the space station has enough components for four full Extravehicular Mobility Unit, or EMU, suits, as well as a number of replacement parts.) Having a modular system also makes things easier with repairs: If one part breaks, engineers can simply replace the part instead of building a whole new suit.

11. Designers focus on one suit at a time.

Given all the testing and design requirements that go into a suit, it's probably not surprising that engineers take it one suit at a time. "We want to understand what does and doesn't work before we build our next iteration," Aitchison says. From concept to design to prototype to testing, "it takes a long time to build a new suit. It takes over a year." Fabrication on the Z-2 suit will begin this month; it will be completed in August, at which point, testing will begin.

12. Astronauts must don a number of layers before they even put on their suits.

That scene from Gravity where Sandra Bullock pulls off her EMU suit and emerges in nothing but a tank top and her undies? Pure bunk. Real astronauts wear several layers under their suits.

First comes a maximum absorbency garment, or MAG, "which is basically a diaper with extra absorption in it," Aitchison says. "That's your waste management system." Over that are comfort undergarments, form-fitting long johns that keep an astronaut comfortable while he or she is wearing the liquid cooling garment. "It provides skin cooling when you're inside your suit and you're working really hard," Aitchison says. "We don't want you to build up a sweat, so we have cold water running in tubes all over your body that pick up heat from your skin and reject it back out to space."

13. There are ways to make a pressurized suit.

Photo courtesy of MIT

Anyone going into space needs to have pressure on their body to keep it functioning normally; the minimum PSI required for bodily functions like inflating the lungs and keeping the blood flowing is 2.5 PSI. (A little more than that, Aitchison points out, is even better.) To accomplish that, astronauts need either a gas-pressurized suit—which is what NASA uses—or a suit that uses mechanical counter pressure (MCP), like the one developed at MIT (above). "You can kind of think of [MCP] as a very tight wet suit," Aitchison says. "It's got to create the same amount of pressure that we get from the gas around us just by pressing on the skin with the suit itself."

NASA looked at a mechanical pressure suit, developed by Dr. Paul Webb, in the 1970s; it was called the Space Activity Suit. Though it worked very well, it took multiple hours—and the help of several people—to put on. That's not the only drawback to MCP. "The other thing you have to worry about is making sure that you have even pressure across your skin at all different positions," Aitchison says. "Places that are concave, or places that change from being flat to concave—the palms of your hands, the backs of your elbows, the knee, the groin—as you move, the shape of those places change. You need to make sure you develop materials that will stick into those contours and move with the change of shape. So there are a lot of challenges in terms of having the technology that's going to help us do exploration in the next 5 to 10 years. Gas pressurized suits are the way we're going to get there."

14. The Z-2 Will be Pretty Small.

Z-1 Space suit. Photo courtesy of NASA/Johnson Space Center.

It will actually be one of the smallest suits made for exploration. "Previously, on the Z-1, we had the big 13-inch dome," Aitchison says. "That works well for large men, but it doesn't have to be that big for smaller females. So shrinking that shrinks down the rest of the suit too. We looked at the current astronaut population and we tried to design a suit that would fit everyone in the bottom 40 percent in terms of their size." The goal of the Z-2 is to design a suit that will fit everyone from the 5th percentile female and to the 99th percentile male—a huge size range.

15. And you can vote on what it will look like.

Z-2 renderings courtesy of NASA/Johnson Space Center.

NASA's last suit design, the Z-1, looked a little bit like Toy Story character Buzz Lightyear (an accident, according to Aitchison). "There was a lot of talk about it, and we wanted to build on that momentum with this suit just to get people asking questions and wanting to know more about it," Aitchison says. "So we came up with this idea to do a voting website for it."

The engineers worked with fashion students at Philadelphia University to come up with different looks for the suit, which was a very different process than what the engineers were used to. "They definitely take a different approach, coming from a fashion background," Aitchison says. "We had to fill out mood boards with different characteristics, whether it was a patriotic theme or a traditional theme or a science and technology theme. We started out with 12 characteristics and we had to narrow it down to what we thought represented us." Based on that, the engineers and the student designers came up with three concepts: Biomimicry, Technology, and Trends in Society. You can vote for your favorite design here.

For now, the designs are purely aesthetic, but Aitchison can see real-life applications for the bioluminescence in the Biomimicry suit, for example. "When we go to other planetary surfaces, if we're working in environments where we have constant day/night cycles, it might be a cool way to do the crew identifier," she says. "Right now we have fabric stripes along the side and upper arm to indicate who's who to different color stripes for each crew member. [Bioluminescence] could be a unique way to do that that would actually be helpful on a planetary surface."