Early in September, several dozen scientists and engineers converged on a cattle ranch in the high desert near Flagstaff, Arizona. They were there to participate in the eighth annual Desert RATS (Research and Technology Studies) field season. This year's research focused on the interaction between SCOUT, a testbed for exploring rover technologies, and two "astronauts" wearing different experimental spacesuits. Dr. Dean Eppler, a geologist who works at NASA's Johnson Space Center in Houston, Texas, wore a Mark III suit. Keith Splawn wore an I2-suit. Splawn is an engineer at Delaware-based ILC Dover, the company that participated in the development of 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 been performing tests on the Mark III suit for many years; he has spent more than 100 hours putting it through its paces. He has also done some work wearing an earlier version of the I-suit. In this, the first of three interview segments, he talks about the Mark III.

Astrobiology Magazine: From the outside, the Mark II suit looks quite bulky and heavy. How easy is it to do geology field research when you're wearing it?

Dean Eppler: As a geologist, what I want to be able to do is go anywhere, do anything and see everything. The first time we were out in the field here our suit runs involved me doing a walkthrough in shirtsleeves, and then putting on the suit and doing the same thing in the suit. We found that the Mark III in many cases has almost shirtsleeve-equivalent mobility.

Now there's a few things you can't do in the Mark III, but they're relatively limited. I can't quite reach the ground, although I can squat down and get within about 6 inches of it. But for walking, for using tools and things like that, it's pretty much got all the range of motion anybody would need. That's one of the things that, despite the present weight of the suit, makes it an exceptional piece of equipment. I just get in and I wear it. I don't have to spend any more time thinking about how to make the suit do something than you do to make sure that your jeans move the right way when you walk.

Some of the earlier suits, the Apollo suits, had a lot of things that the crew could not do in them, that they had to work very hard to overcome. Probably the biggest example was dropping things. You really couldn't bend over and grab them. You either had to do this funky sideways motion or go down on your knees. That suit had that kind of mobility partly because of the technology available at the time and partly because that suit was used to do a lot of things in addition to walking on the moon.

With the Mark III, I can do anything but dance, and that's partly because I can't dance, and partly because I'm in a 1-G (normal Earth gravity) environment. I've worn that suit on the KC-135 (an Air Force jet) at one-third and one-sixth G and it's a real treat. Once you get the weight off, you can do anything in that suit - including getting down to the ground, because you don't have to worry about getting back up again. You basically go down and pop back up. We actually have a picture in the lab of one of the other suit subjects doing a handstand in the Mark III at one-third G.

AM: How much does the Mark III weigh?

DE: It's a heavy suit now. With suit and backpack on, it weighs as much as I do, about 210 pounds. The Mark III was originally built when NASA was considering a new space station suit. Part of the reason it weighs so much is because one of the goals for a new space station suit was to get a zero-pre-breathe system. Presently, the space station is pressurized at 14.7 psi (pounds per square inch) and the suits the space-station astronauts use when they go outside the station work at about 4 psi. So the crew members have to go through a lengthy pre-breathe process to make sure that they don't get the bends. (Scuba divers go through a similar decompression process before surfacing from a dive.)

If you use a higher suit-operating pressure you can spend less time pre-breathing. So the Mark III suit was originally built to take a lot higher operating pressure than we are presently using it at and consequently it's a lot beefier and heavier than it needs to be. One of the things Joe Kosmo (the project lead for Desert RATS) and I have been interested in doing over the years is building a Mark III that only has to go to 4 psi instead of the 8.5 psi that the current Mark III was designed for, to see what kind of weight savings we can get.

AM: You must get tired pretty quickly carrying so much weight around.

DE: When I'm standing there, my heart rates are actually down around almost what they'd be if I was just standing around normally. You can position yourself so that the column of pressurized air in the suit is supporting most of the weight of the suit. So there's ways to manage the weight and ways to work within the suit. One of the things I always tell people is that if you try and fight the suit, it's going to win every time. You're not hard. It is. A lot of learning how to work in the suit - and I think the astronauts will tell you this as well - is learning how to work within its limitations, so that you're not working yourself up into a lather trying to do something you just can't do.