Ten years ago, this month, the crew of Shuttle Atlantis—Commander Brent Jett, Pilot Chris Ferguson, and Mission Specialists Joe Tanner, Dan Burbank, Heidemarie Stefanyshyn-Piper, and Canada’s Steve MacLean—roared into orbit to restart the construction of the International Space Station (ISS). Following the delivery of its initial elements into space from December 1998, the station had steadily grown from a couple of modules to the basis of today’s multi-national outpost: with the U.S. Destiny lab, the Quest airlock, the Canadian-built Canadarm2 mechanical arm, and the first set of electricity-generating solar arrays, batteries, and radiators. However, that single set of arrays provided barely a quarter of the power which the station would eventually need to support its remaining science modules. On STS-115, Jett’s crew would deliver the P-3/P-4 truss segment, equipped with a second set of arrays, batteries, and radiators to double the station’s existing power capability.
As outlined in yesterday’s AmericaSpace history article, the STS-115 crew was announced by NASA in February 2002 and trained for an original launch date in the first half of 2003. At the time of the Columbia disaster, Jett and his team were less than 16 weeks away from liftoff. All shuttle crews were stood down as the Columbia Accident Investigation Board (CAIB)—chaired by former U.S. Navy Adm. Harold Gehman—worked to identify the causes and contributory factors in the disaster, and NASA pressed ahead with its efforts to return the surviving orbiters to flight. Most of the shuttle crews-in-training at the time of Columbia’s loss were broken up and reassigned, but the six-strong STS-115 team remained intact. So too did their basic mission profile.
However, there were several significant changes between the STS-115 planned before Columbia and the STS-115 which actually rose to orbit in September 2006. In keeping with post-Columbia requirements, the first and second days of the mission included a thorough checkout of the shuttle’s Thermal Protection System (TPS) and Reinforced Carbon-Carbon (RCC) surfaces to identify any areas which may have sustained damage during launch. Burbank and MacLean, working with Ferguson, grappled the 50-foot-long (45-meter) Orbiter Boom Sensor System (OBSS) with the Canadian-built Remote Manipulator System (RMS) mechanical arm and employed its high-resolution television camera and twin laser sensors to conduct an eight-hour-plus inspection of Atlantis’ wing leading edges and nosecap. “It’s a series of automated maneuvers, so we’re essentially relegated to the role of monitoring the automatic activity that’s going on,” said Ferguson before launch. “While it’s a highly-focused and intensive task, we are able to back out a little bit and monitor the computer’s automated system. It’s a long day and it’s going to be a tedious day, but we’re prepared for it.”
With docking targeted for 6:46 a.m. EDT on 11 September, the crew was awakened several hours beforehand, to a rousing cello performance by Dan Burbank’s children. Another facet of the post-Columbia regime required Jett to fly Atlantis through a Rendezvous Pitch Maneuver (RPM). In essence, this took the form of an orbital “back flip” at a distance of about 600 feet (180 meters), which allowed Jeff Williams aboard the ISS to extensively photo-document the condition of the shuttle’s flight surfaces for damage. For the photo-documentation, Williams was based in the station’s Zvezda service module with digital camera equipment, equipped with 400 mm and 800 mm lenses.
“The RPM maneuver … is actually very visually dramatic,” said Jett, “but from a flying standpoint, it’s not really any more difficult than any other type flying we do for rendezvous. The real significance of the RPM is that it allows the station crew to take photos of the underbelly tile areas of the orbiter, which we don’t inspect on Flight Day Two.” From his perspective, Jett set up the initial conditions to begin the RPM, allowed it to happen, then assumed control of Atlantis at the end to continue the approach and docking. His target was Pressurized Mating Adapter (PMA)-2 at the forward “end” of the U.S. Destiny lab, and he performed a smooth docking at 6:48 a.m. Within two hours, after pressurization and leak checks, the hatches were opened and nine astronauts and cosmonauts from four sovereign nations engulfed each other in smiles, handshakes, and bear-hugs.
Yet there was little time to reflect on their surroundings. Almost immediately, Ferguson and Burbank grappled the massive P-3/P-4 truss with the shuttle’s RMS and detached it from the payload bay. Coming so soon after docking, it was “a long, long day,” according to Jett. Aboard the ISS, MacLean joined Williams at a Robotic Workstation (RWS) to employ the space station’s own Canadarm2 to receive the truss and ready it for installation. With MacLean operating Canadarm2, this marked the first occasion that a Canadian citizen had operated the station’s arm in orbit.
At 2 a.m. EDT on the 12th, MacLean and Williams maneuvered the P-3/P-4 segment toward its eventual location at the far-port end of the P-1 truss. It remained on the end of Canadarm2 overnight, in a thermally benign “overnight park” position, ahead of the first EVA, conducted by Tanner and Stefanyshyn-Piper. The decision to split the installation over two days was based purely upon the mission protocols. “If we wait till the next day, we just don’t have enough time in the day to get everything done with the arm maneuvers,” said Tanner. The need for at least two hours to simply get the P-3/P-4 segment out of Atlantis’ payload bay, followed by several more hours of constant attention to get it transferred over to Canadarm2 and installed onto its P-1 location, made it more advantageous to split the activities into two halves. By leaving the truss in the overnight park condition, it would not get too hot or cold and would remain healthy until it was installed onto the space station the following morning.
With the Quest airlock having been installed onto the space station in July 2001, this would not be the first time that it had been used by spacewalkers to begin their EVAs. However, the first EVA of STS-115 was notably different from its predecessors, in that Tanner and Stefanyshyn-Piper performed an overnight “campout” in the airlock, whose pressure had been reduced from its ambient 14.7 psi to 10.2 psi. Unfortunately, on this occasion, it would be a campout without marshmallows! The campout prebreathe had been trialed by Expedition 12/13 astronauts Bill McArthur and Jeff Williams in April 2006, but on STS-115 it would be utilized for the first time before a “real” EVA.
“If we can spend some time at 10.2, before going down to the final suit pressure of 4.3, that time spent breathing pure oxygen gets reduced significantly, from four hours to the 45-minutes-to-an-hour range,” Jett explained. “That’s a big saving, when you’re trying to get a 6.5 or 7-hour EVA done. On the shuttle when we weren’t docked to station, we could take the shuttle to 10.2; it wasn’t a big deal. We can’t do that with the entire station, so we take the two EVA crew members and put them in the equipment lock of the airlock. We close the hatch and just take that one section of the station down to 10.2.” By spending the night at this reduced pressure level, not only was nitrogen purged from Tanner and Stefanyshyn-Piper’s bloodstreams—thereby reducing the risk of the “bends”—but their final pre-EVA preparations were correspondingly shortened, allowing them to better function at the 4.3 psi pressure of their suits.
“The downside is that you probably have to go to the bathroom in the morning, and so we will do what we refer to as a hygiene break,” recalled Tanner. “For that break, you must put on an oxygen mask. We repressurize the station airlock, so that we can open the hatch, and then while wearing this oxygen mask, you go to the bathroom and come back in and the total amount on the mask is 70 minutes. Once you get back in the airlock, depress it again down to 10.2 and if you’ve achieved your 70 minutes on the mask, then you can take the mask off and do a normal suit-up.”
Tanner and Stefanyshyn-Piper floated out of Quest at 5:17 a.m. EDT and spent six hours and 26 minutes in vacuum, connecting power cables, releasing launch restraints on P-3/P-4’s Solar Array Blanket Box (SABB) and Beta Gimbal Assembly (BGA), and configuring the automobile-sized SARJ and its drive-lock assemblies.
In doing so, Stefanyshyn-Piper became only the eighth woman in history to make an EVA, following in the footsteps of trailblazing pioneers Svetlana Savitskaya and Kathy Sullivan, Hubble Space Telescope (HST) veteran Kathy Thornton, and the world’s then-most-experienced female spacewalker, Peggy Whitson. EVA veteran Tanner, on the other hand, had previously spacewalked on five occasions outside Hubble and the space station, totaling more than 35 hours. Working briskly, the duo had almost finished the entirety of their activities within 3.5 hours, allowing Mission Control to assign them a number of “get-ahead” tasks. These included the removal of SARJ launch locks, although a minor glitch occurred when a bolt and washer came loose and floated off into space.
Next day, 13 September, it was the turn of Burbank and MacLean, both first-time spacewalkers. Interestingly, MacLean became only the second Canadian—after STS-100’s Chris Hadfield—to perform an EVA. He and Burbank spent seven hours and 11 minutes wrapping up the activation of the SARJ, completing the release of its launch locks. Assisting them from inside Atlantis’ cockpit were Tanner, as Intravehicular (IV) crewman, with Stefanyshyn-Piper commanding the RMS. However, the spacewalkers were forced to overcome a handful of minor problems, including a malfunctioning helmet camera, a broken socket tool, and stubborn and loose bolts. Following the return of Burbank and MacLean inside the shuttle, Mission Control activated and commenced a four-hour checkout of the SARJ, successfully engaging the first of its drive-lock assemblies and rotating the joint by 180 degrees.
Later, the second drive-lock assembly was also engaged, with the intention that the SARJ would be rotated again 360 degrees. However, despite several attempts, controllers on the ground did not receive an indication that the drive-lock assembly had properly engaged and the planned deployment of the P-3/P-4 solar arrays was postponed until the problem could be resolved. Engineering teams subsequently developed a software workaround and on the 14th the arrays were confirmed successfully deployed at 8:44 a.m., essentially doubling the space station’s electricity-generating capability. The deployment process required a little over 4.5 hours to complete and the sole difficulty of note was a slight “sticking” (or “stiction”) of the panels as they unfurled. That said, actual usage of the power would not come until the crew of shuttle mission STS-116—planned for December 2006—extensively rewired the station’s electrical and cooling systems.
With several mission objectives rescheduled and reprioritized following the delayed P-3/P-4 deployment, Tanner and Stefanyshyn-Piper readied themselves and their suits for STS-115’s third and final EVA on 15 September. After completing another overnight campout, a Remote Power Controller (RPC) tripped, causing a loss of power to Quest’s depressurization pump. The astronauts transferred back into the station’s adjacent Unity node, whilst continuing their pre-breathing protocol on masks, as engineers tackled the problem. It was eventually narrowed down to a momentary electrical spike and, after a resultant 45-minute delay, the pair ventured outside at 6 a.m.
Both spacewalkers split up for their respective tasks, as Tanner set to work installing bolt retainers on the BGA of the P-6 truss segment, helping to orient the pitch of its own solar arrays and Stefanyshyn-Piper retrieved the Materials on the International Space Station (MISSE)-5 experiment. Working together, they prepared the P-3/P-4 Photovoltaic Radiator (PVR) for deployment and replaced an S-band Antenna Support Assembly (SASA) communications antenna on the S-1 truss for use by the STS-116 crew, together with a baseband signal processor and transponder. Ending after six hours and 42 minutes, EVA-3 brought STS-115’s log of spacewalking up to 20 hours and 19 minutes.
Finally, in the early hours of 17 September, the time had arrived for Atlantis to depart. After sharing farewell wishes to the Expedition 13 crew, the hatches were closed for the last time and Jett undocked from the space station at 8:50 a.m. Ferguson then took the controls for a traditional flyaround inspection of the unusual T-shaped configuration of the ITS, before a final separation maneuver at about 10:30 a.m. With the Expedition 14 crew launched toward the ISS a day or so later, the unique opportunity arose early on 19 September for three different sets of space travelers to communicate with each other, via radio.
“It’s a little crowded in the sky today,” said Williams, then told the upcoming Expedition 14 crew: “We look forward to having you guys on board.” From Atlantis, Jett offered his good wishes to Williams and Vinogradov, ahead of their scheduled return home in late September. “We’ll see you back on Earth sometime soon.”
Atlantis’ originally planned landing date on 20 September was postponed by 24 hours, in order for a focused late inspection of the shuttle’s exterior. This had become necessary when video footage highlighted a piece of debris close to the vehicle. In a sense, this was just as well, because weather forecasts at the Shuttle Landing Facility (SLF) at the Kennedy Space Center (KSC) in Florida were none too favorable. Operating the RMS, Burbank, MacLean, and Ferguson spent several hours painstakingly examining the shuttle’s exterior and acquiring imagery which was then pored over by specialists on the ground. A shim and a spacer piece had been observed protruding from thermal tiles earlier in the flight and turned out to be missing, but it was unknown of they were the observed debris. However, Mission Control gave the spacecraft a clean bill of health and the STS-115 astronauts geared up for their scheduled landing on 21 September.
With light winds and a few clouds forecast over Cape Canaveral, Atlantis’ crew performed the deorbit burn at 5:14 a.m., thereby committing themselves to a touchdown an hour later. At 6:21 a.m., in the darkness of a Florida pre-dawn, Jett guided the shuttle to a smooth landing on Runway 33. In spectacular fashion, his crew had resumed a task left undone following the agony of Columbia and had set the space station on course for completion and full utilization into the second decade of the 21st century.
This is part of a series of history articles, which will appear each weekend, barring any major news stories. Next week’s article will focus on the 50th anniversary of Gemini IX, a September 1966 mission which—to this day—retains the record for the highest altitude ever reached by humans on a non-lunar voyage.