The suits are being tested to provide input to the development of flight-ready suits for future human missions to the moon and Mars.

In this year's Desert RATS field test, Eppler donned a Mark III-suit. His colleague Keith Splawn wore an I2-suit. Splawn is an engineer at Delaware-based ILC Dover, the company that designed and developed both suits.

The two "suit subjects" ran through a number of scenarios: scrambling up hills; collecting rock and soil samples; testing communications and navigation equipment; and controlling the SCOUT rover both manually and with voice commands and gestures.

Near the end of the two-week period, Astrobiology Magazine's Henry Bortman interviewed Dr. Eppler about his experiences. Eppler has spent more than 100 hours in the Mark III, and has also done some work in an older version of the I-suit.

The I-suit, an all-fabric suit, was developed as a lighter alternative to the Mark III, which combines both hard and fabric components. The original I-suit had a "body seal" design: the two main parts of the suit joined together around the ribs. The I2-suit, a newer model, allows its wearer to enter from the rear, as does the Mark III.

Astrobiology Magazine: During this year's tests, you were in the Mark III-suit. But you've also spent some time in the original I-suit. How would compare those experiences?

Dean Eppler: I did a number of runs in the original I-suit, which you got into very much like the shuttle suit, where the suit comes together just below the base of your sternum. And I don't care what gender you are, if you compare the shape and circumference of your body around your shoulders and around your sternum, you're going to find that these two shapes don't really fit very well. So you've got to push one into the other. Getting in and out of the I-suit - getting in, in particular - was never one of my favorite things to do.

People have asked me if I get claustrophobic in suits. Generally I don't, but getting into the old I-suit was never something I enjoyed doing. You had to get one arm going, and then the second arm, and then close your eyes and push like hell and hope when it's all done there's a hand at each end of the arm and there's a head sticking out of the helmet connection. With a rear-entry suit, there's a certain amount of contortion you have to go through to get in, but it's a lot easier on the body. So I'm a big fan of the rear-entry suit.

AM: So the I-suit was more difficult to get into. But once you were in it, was it easier to work in than the Mark III because it was lighter?

DE: That's an interesting question, because when we first started doing work with the I-suit, we thought, Well, it's about 50 pounds lighter, it's going to be a lot easier to work in. And what I found after doing a number of runs - particularly an exercise we did at Silver Lake in California in February of 1999 - was that I was as tired, perhaps more tired, with the I-suit than I was with the Mark III.

Even though we had taken 50 pounds off of the total system weight, we hadn't worked on any way of reacting that system weight onto my hips. Your hips and your whole leg structure can lift about an order of magnitude more weight than your arms can. Your arms really aren't meant to do that kind of endurance activity. We found that, even though the suit was lighter, because I was carrying most of its weight on my shoulders, I wasn't realizing any reduction in fatigue.

That was quite a surprise to everybody, me in particular. Because I assumed, Well, this is kind of a pain to get into, but it's going to be worth it because I'm going to be a lot less tired. It was kind of a shock to find I wasn't a lot less tired. In fact, in some cases I think I was more tired after I-suit runs. There's a lot of complexity to your ability to move in, handle, work with and get fatigued by a suit. It's more than just how much it weighs.

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