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IMAGE: Expedition Four Flight Engineer Carl Walz
Click on the image to hear Expedition Four Flight Engineer Carl E. Walz's greeting (366 Kb).

Expedition Four
Spacewalking, ISS Style

By Astronaut Carl Walz:

In light of the launch of STS-110, and hot on the heels of the highly successful STS-109 Hubble repair flight, I thought I would pass on a few observations of our ISS experience with our U.S. spacewalk hardware.

On 20 February, Dan Bursch and I donned the U.S. spacesuit, the EMU, and did a five-hour, 47-minute spacewalk. Yury Onufrienko, our commander, suited us up and then provided camera views while we were outside the vehicle. This event marked the first U.S. spacewalk since the Skylab program to be performed without the Space Shuttle present. Since it was a unique event, it was designated U.S. EVA Number 1. Of course, we have to date seven ISS spacewalks using the Russian space-suit, the Orlan without the Shuttle present. Spacewalk is somewhat of a misnomer, as the work is very demanding technically and physically. The suit resists almost all movements, so you get a pretty good workout. The EVA had two major purposes. The first was to verify that all major joint airlock systems were functional and the second was to perform get-ahead tasks for the 8A crew. In a way, we performed the first 8A EVA prior to 8A's launch!

Because our last airlock training had been performed about four months before the EVA, and our last run in the Neutral Buoyancy Lab (NBL) was also about four months before, and since we had not ever run the timeline in the NBL, we required some in-flight preparation that was different than what a Shuttle-based space-walking crew would require. Some of the items were things planned by our ground team for us, and we requested a dress rehearsal of all the spacewalk preparations up to hatch opening.

IMAGE: Expedition Four Flight Engineer Carl Walz
Flight Engineer Carl Walz prepares inside the Quest airlock for a 5-hour, 47-minute spacewalk on February 20, 2002.

Our timeline was developed by our EVA, Robotics, and Crew Systems Operations Division Expedition 4 team lead, Dina Barclay, and her EVA team, which included John Raines, Tracy Snow, and Roger Lottridge. They did a superb job of planning not only our EVA timeline, but all our preparation and in-flight training activities leading up to the EVA. Our timeline was verified in the NBL by Pat Forrester and Joe Tanner, both astronauts with EVA experience on the ISS.

Our in-flight preparation included the use of DOUG, a computer program that provides graphical depictions of the exterior of the Station. DOUG is a product of the Virtual Reality Laboratory in Building 9. Dave Homan and his team did a great job providing us with a superb computer tool for EVA preparation. Using DOUG and our timelines, we were able to visualize translation paths, and we were also able to see where the hardware we would be working with was actually located. DOUG also allowed us to practice "flying" SAFER, our special jet backpack designed to propel us back to the Station in the event we would "fall" off and float away. With no Shuttle present, there was no vehicle available to pick us up if we floated away. We also had an EMU trainer program to review EMU malfunctions and emergency procedures prior to the EVA. This of course allowed us to freshen up our knowledge of the spacesuit as well. Our suit lead, Tracy Snow, uplinked training scenarios to us so we could better use these trainers. It was almost like a training session on the ground.

Typically before a Shuttle-based EVA, the EVA crew has a chance to perform suited runs in the NBL almost every week. Besides great practice for the spacewalk tasks, the crews also gain physical training time, since the stiffness of the suit makes every movement difficult. We of course did not have that luxury here, so we had to use a combination of workouts on the Resistive Exercise Device on board the Station, and also arm ergometry performed on the cycle ergometer, the CEVIS, to maintain our fitness for the EVA tasks.

From an airlock preparation standpoint, the Space Station environment affords us the luxury of time to prepare for the EVA's. While Shuttle-based EVA's rely on highly choreographed timelines to be precisely executed, we can perform our preparations in a less-rushed manner. Some preparation jobs are put on our "task list" where we can perform the activities whenever we wish. EVA tool check-out, crew-lock preparation, mini-workstation configuration were all done as task list items.

IMAGE: Expedition Four Flight Engineer Dan Bursch
Flight Engineer Dan Bursch moves around the Quest airlock using handrails.

We also had the opportunity to look out the windows of Station to view some of our worksites. The forward facing window of the docking compartment gave us a great view of the joint airlock, and allowed us to know exactly where our safety tether reels were located. Those tether reels are our main means of security while spacewalking, providing us a constant secure physical connection to the Station.

We performed the dress rehearsal on 15 February, five days prior to the actual EVA. The rehearsal, very similar to what we did with the Orlan suits in January, went really well with all elements of the suit-up process completed and all equipment checked out, well within the time guidelines. Astronauts Charlie "Scorch" Hobaugh and Cady Coleman were our capcoms and helped guide us through the practice. It had been almost nine months since the joint airlock had been used for an EVA, so the rehearsal gave us a lot of confidence that all airlock systems were go.

To prepare our bodies for the lower pressure in the spacesuit than inside the Station, we have to do a pre-breathe before depressurization of the airlock. We do that with a combination of breathing pure oxygen from an oxygen mask, including 10 minutes of cycle ergometer exercise on the mask, and then 72 minutes of pure oxygen breathing in the spacesuit. The program is pretty complicated, but Dan and I were both able to perform the exercise, get back to the airlock, and don the spacesuits without problem. Yury was our hose wrangler, helping collect the unwieldy oxygen hoses that provided our breathing gas. Yury also helped us don our spacesuits, which are three-piece units, as opposed to the one-piece Orlan. He also installed our SAFER's and gently moved us into the crew-lock.

On the 20th, EVA day, we got up a little earlier than normal, had a nice breakfast, and then started the preparations. We had all the necessary equipment staged the night before, so we were able to start our pre-breathe early. Because we had practiced getting our spacesuits on recently, we were able to get dressed in the suits even faster than before. We were able to open the airlock external hatch about 30 minutes earlier than planned. We exited the airlock at dawn, and started our work right away. We attached power cables, retrieved tools for the 8A space-walkers, removed thermal blankets from the Z1 truss, did fluid connector inspections, and several other tasks that the ground needed us to do.

Yury remained inside and manned the cameras. Joe Tanner, the Chief of the Astronaut Office's EVA Branch and an astronaut with lots of EVA experience, provided our task guidance as we performed the various activities outside ISS. During a Shuttle mission, this activity is performed by the IVA Shuttle crew member who has spent time training time with the space-walking crew at the NBL. In the ISS case, where fewer crew members are available, the ground took over and provided the guidance. We were blessed with excellent communications with the ground during the EVA, so it seemed like Joe was inside the Space Station and giving us his guidance.

IMAGE: Expedition Four Flight Engineer Carl Walz
From left are Expedition Four Flight Engineers Dan Bursch and Carl Walz.

The exterior of the Space Station looked just like new. It was very shiny and clean. It was very easy to move around the exterior, as there were lots of handholds along the way. Our long safety tethers were firmly attached to structure, and if that failed, we had the SAFER jet backpack to fly us back to the Station. We worked both night and day (remember we get sunrise 16 times a day), using our helmet lights to illuminate our paths when necessary.

February 20th was not only a big day for us, it was the 40th anniversary of the flight of John Glenn in Friendship 7, when he became the first American to orbit the Earth. During the spacewalk, Dan and I reflected on that anniversary, and afterwards got a chance to talk to Senator Glenn from NASA Headquarters in Washington.

After the EVA was over, it was time to put all our space-walking gear away. It was kind of a sad time, similar to when you take down your Christmas tree and decorations after Christmas. We will pull it all out again of course when the STS-110 mission comes to visit.

We would like to thank our EVA team from the EVA, Robotics, and Crew Systems Operations Division, the Astronaut Office, the EVA Project Office and the Virtual Reality Lab for their great work for ISS EVA 1. We also used the experience from our Russian EVA's to make our EVA 1 successful. We hope future crews will be able to use our experience to make their EVA's from the crew-lock successful as well.

Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 09/04/2002
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