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The Astronaut's New Clothes

Since the early days of manned space flight, engineers have designed a wide variety of space suits. Their biggest challenge, though, may still lie ahead: a suit for the first manned mission to Mars
aging



J. W. Stewart
On Mars
Image: NASA

ON MARS astronauts will need space suits that are lighter and offer greater mobility than those currently in use.
A lonely figure in a bulky space suit walks slowly across a giant meteorite impact crater. The rocky desert landscape appears cold, dry and hostile¿not unlike Mars. In fact, the man is testing the space suit astronauts might wear if they ever go to the Red Planet.

The scene is Devon Island in the Canadian high arctic, a place about as close to the desolate setting of Mars as you can get on Earth. The 20-kilometer-wide Haughton Crater on Devon Island, the result of a meteorite impact about 23 million years ago, is the only such impact crater known to lie in a polar desert environment, which makes it the ideal testing ground for Mars mission space suits. NASA has no immediate plans to send a man or woman to the Red Planet. But several companies have been working on a space suit for Mars.

"A prototype would be an exaggeration," says Ed Hodgson, Preliminary Design Engineer at Hamilton Sundstrand Space Systems International. "We have been working on concepts for space suits for a Mars mission with the recognition that the challenge is a big one and we need all the lead time we can get." ILC Dover, a subsidiary of Hamilton Sundstrand, makes the suits that shuttle astronauts use during space walks. Their concept suit is called the I-suit. David Clark Company, which makes the orange suits that shuttle astronauts wear during takeoff, has also built a Mars concept suit, the D-suit. And the NASA Johnson Space Center created a third, the H-suit, using from components from outside companies.

The suit NASA uses today for extravehicular activity (EVA) is a 24-year-old modular design that has evolved from Apollo, Skylab and shuttle program applications. In these suits, the so-called Lower Torso Assembly (LTA), roughly the equivalent of pants and boots, consists of a Waist Assembly, Trousers Assembly and Boot Assembly. The pieces are made of fabric but joined together using metal bearings. Fabric is really an understatement: the material contains a layer of urethane-coated nylon, followed by Dacron, neoprene-coated nylon, five layers of aluminized Mylar and an outside layer of Teflon, Kevlar and Nomex.

The counterpart to the LTA is the HUT, or Hard Upper Torso, which is made of fiberglass and connects to arms, gloves and a helmet. The Primary Life Support Subsystem (PLSS) attaches to the back of the HUT. It resembles a backpack and provides the astronaut with oxygen. The PLSS also controls the air pressure in the suit, as well as the temperature of the oxygen and water that run through the garment to keep the astronaut cool. The HUT removes humidity, odors and carbon dioxide from the air inside the suit and carries the communication equipment and sensors. A secondary oxygen pack attaches to the bottom of the PLSS for emergency oxygen and other life-support functions. On the front of the HUT, astronauts carry a Display and Control Module (DCM), which keeps them informed about the status of the PLSS. The entire contraption runs on batteries built into the PLSS.

This sophisticated system becomes quite heavy, approximately 300 pounds, on Earth. In the weightlessness of space, that doesn't present a problem, but moving around on another planet in such heavy gear would be a different story. "The mission [to Mars] is going to demand a system that weighs less than half of what the current system weighs," Hodgson explains. "It has to be half the weight because we're operating on a planetary surface with 0.38g's [0.38 times Earth's gravity]." Gravity on our planet's moon-the only celestial body on which humans have set foot-pales in comparison, having only 0.16 times the gravitational force of Earth.

Mars Space Suit Concept

Image: The NASA JOHNSON SPACE CENTER

THE H-SUIT is one of three space suit designs being explored for future missions.

A mission to Mars would also take significantly longer than one to the moon¿a delay that creates additional problems. "You can go to the moon and be there for only a few days, do three space walks and come home. When we go to Mars, best case right now, you would be in transit for six months," Hodgson says. Once the spacecraft reached the planet, it could stay for only a few days. To minimize the time and fuel spent, a mission to Mars would have to occur during a time when the solar orbits of Mars and Earth brought them close together. But as the planets continued on their paths, they would move increasingly farther apart, making a return trip more difficult and time-consuming. Alternatively, a crew might stay on Mars for two years and return when the planets again neared one another. Such a long mission, though, would require an extremely efficient use of the resources available on board. Recycling would be essential in all aspects of the mission, but regenerating systems tend to weigh more as well.

Today's space suits operate in a vacuum and use this condition to their advantage. The air inside the space suit inflates it like a balloon, separating the different layers of the space suit fabric and creating very efficient insulation. "If you try to squeeze a balloon, the more you squeeze on it, the tougher it gets to do because the pressure is going up," explains Phil West, a spokesman for the NASA Johnson Space Center. "And if you try to bend the balloon, it doesn't bend very easily." Some of the metal bearings¿so-called mobility bearings¿therefore also function as joints, letting components rotate against each other. Other special joints let the astronauts bend the suit while keeping its overall pressure constant.

The vacuum also allows the current suit to pass carbon dioxide on to the environment in a process that wouldn't take place on Mars, where the atmosphere contains mostly carbon dioxide. And although the atmosphere on Mars is very thin, winds on the planet could create problems. "Clearly dust gets blown around Mars quite a bit," West says. "Even though a very fast wind on Mars doesn't feel like much because the pressure is so low, it still blows dust around. We expect the dust to behave a lot the way lunar dust did in that it got into everything," he says. Current space suits are not protected against such dust intrusions, which could disable mobility bearings and harm other components of the already maintenance-intensive suits.

Radiation is another major concern. "Most of our EVA experience, and specifically with the space suits, has been within the protective confines of Earth's magnetosphere," Hodgson explains. "We dealt with some more challenging radiation environments when we went to the moon, but the mission duration was so short it wasn't as much of an issue." So far no one has found a viable form of protection against radiation that could be integrated into a space suit. The only means of limiting exposure today is limiting the amount of time spent outside.

Radiation protection aside, spending more time outside the spacecraft also calls for greater mobility. "When you work on the space shuttle or the space station, we call it a space walk, but that's sort of a misnomer," West says. "It's really more of a space float. You really just pull yourself along handrails, doing your walking with your hands. You can get around with pretty limited leg mobility, as the astronauts on the moon did. But we would like to provide the astronauts with more mobility than that so they aren't so restricted." On Mars, he says, "You want to be able to pick up rocks, survey the land and pick yourself up if you fall down."

To cope with these requirements, the Mars suits under development take different approaches. "The H-suit has more rigid components than the I-suit; the I-suit has more fabric components," West says. "They have some bearings in similar places, but you get in and out of them differently. We've tested the I-suit and the H-suit as recently as last fall in the Arizona desert to see how they behave."

The researchers at Hamilton Sundstrand are also looking to improve the Display and Control Module in space suits for use on the International Space Station and shuttle missions. The system on the current NASA space suit, for example, only processes and displays information about the suit in simple text. By the time a manned Mars mission becomes a reality, though, the suits might contain an integrated computer design in which astronauts monitored suit information and "to-do" lists on the same computer. The system could also be used for communication and to provide reference data.

The Hamilton Sundstrand team is considering a technology that would project information onto the helmet's visor or onto the astronaut's retina. They are also looking into small wrist-worn devices. But West is skeptical: "How complex you go is the question. I mean do you go as far as fancy information displays trying to get video data or information from the rover over to the astronaut," he says, "or do you limit yourself to keeping it more straightforward? How do you deal with all that information?"

Hodgson agues that such display devices could greatly simplify the lives of Mars explorers. "One of the things you can do is enable the astronaut to do the kind of detailed examination of the surface he wants to do, without the need to repeatedly kneel down to the surface, and that entails using cameras that you can carry at the end of a stick and actually transfer the image directly to a display in your suit," he says. "So you can get up close and personal with a rock without having to go down to it." West thinks these aspects are secondary in developing a Mars suit. "Who knows what kind of processing and display capabilities exist by the time we go to Mars? I think those types of things have the option of being integrated into a suit package. Our biggest challenges are the reliability and weight and getting a mobile suit with those features.

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