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Spacewalks

Canadian Suits Up for Spacewalk: MacLean has Key Role in Space Station Construction

Countless hours of training underwater and on virtual simulators are about to pay off for Canadian astronaut Steve MacLean as he gets set to walk in space on the latest trip by Shuttle Atlantis to the International Space Station (ISS) on mission STS-115. Only the second Canadian in history to step out into the vacuum of space, Maclean will conduct a mission-critical spacewalk to complete installation of a newly delivered solar panels platform that will boost power to the orbiting laboratory.

Just the third shuttle flight since the Columbia tragedy in 2003, the STS-115 mission marks the 19th shuttle visit to the fledgling station and the next step in its construction. The ISS represents the greatest and most complex space project in the history of humankind, with 15 countries participating. The main goal of MacLean and his six crewmates on this 12-day flight is to install a massive new truss and make sure that the accompanying set of solar panels delivers the proper power to the high-flying outpost.

NASA astronaut Joseph Tanner in 2000 during a spacewalk he performed. A section of the newly-deployed solar panel is in the background. Tanner is going to perform the first spacewalk planned in the course of Mission STS-115. (Photo: NASA)

After inspecting the shuttle for signs of possible launch damage and then docking with the ISS early on day 3 of the mission, the crew of Atlantis will get straight to work on the next phase of building the station. MacLean has a full plate of complex activities as he divides his time between commanding the station's own construction crane, the Canadarm2, and preparing for his gruelling spacewalk.

Late on day 3, setting the scene for the upcoming spacewalks, Joseph Tanner will use the orbiter' robotic arm to reach into the shuttle cargo bay and pick up the truss assembly called P3/P4. He will then hand this 17.5-ton payload over to Maclean, who will be controlling the station's Canadarm2 to park the truss overnight. The next day, again commanding the station's robotic manipulator, Steve will bring the new assembly towards the station and install it at the end of the P1 and spacewalkers Joe Tanner and Heidi Stefanyshyn-Piper perform the first spacewalk to attach the truss assembly.

On day 5, MacLean and crewmate Dan Burbank get a chance to don their spacesuits for the second of three scheduled orbital spacewalks. But there is a lot of preparation needed before stepping outside into the unforgiving environment of space for a 6.5-hour excursion.

The night before, MacLean and Burbank will take inventory of their spacesuits and tools. They will then lock themselves in the U.S. Quest airlock chamber and camp out for the night. The spacewalkers will don oxygen masks and start slowly lowering the surrounding air pressure so they can eliminate nitrogen in their blood, just as deep divers do on Earth to avoid getting "the bends" or decompression sickness. The morning of Day 5, after going through their checklists of all their extravehicular activity (EVA) tasks and putting on their spacesuits, they will let the air out of Quest, open the hatch, and step outside.

Canadian Space Agency astronaut Chris Hadfield preparing for his spacewalk in 2001. Hadfield installed the Canadarm2 on the International Space Station. (Photo: NASA)

Flying in unison with the Shuttle and orbiting station at 28,000 km per hour, more than 400 km above the Earth, MacLean and Burbank will spend most of their time getting the newly delivered Solar Alpha Rotary Joint (SARJ) ready for activation. The SARJ allows the solar arrays to rotate 360 degrees to point the power generating panels directly towards the sun and track the Sun as it changes position throughout the year. MacLean will gingerly remove six launch restraints, four thermal covers and 16 launch locks on the SARJ. With the addition of the new set of solar arrays and the SARJ, the ISS will have more reliable energy and double the power capacity available up to 128 kilowatts to run the many activities on the growing station.

While MacLean is on EVA, Stefanyshyn-Piper will be at the controls of the robotic workstation to operate the station's Canadarm2 and its camera systems. Meanwhile, Canadian ground controllers will supervise all robotic activity from both the Canadian Space Agency headquarters in Longueuil, Quebec, and the Johnson Space Center, in Houston, Texas.

Later on day 5, while MacLean and Burbank are recovering from their exhausting excursion, ground controllers will send commands up to unfold the newly installed solar panels and turn them on. The stage will now be set for the third and final EVA on day 7 where Piper and Tanner will remove the final restraints and braces on the truss system.

Canadian technology and talent have played a vital role throughout the history of ISS assembly since the first module was placed in orbit back in 1998, but it will be thrust into the forefront on this mission like never before. Everything from the shuttle Canadarm and its new boom extension and specialized 3-D laser camera, the station's Canadarm2 and computerized vision system, to Steve MacLean and mission controllers on the ground, Canadian know-how will be pivotal in making all the construction tasks a success. This mission is huge in terms of Canadians being involved in the first post-Columbia assembly flight back to the Space Station," says MacLean. It's pretty clear that, to date, this is the flight with the most Canadian expertise ever.