Space shuttle Discovery's mission to deliver Node 2, otherwise known as Harmony, to the International Space Station has become known as, 'the most complicated space station construction mission yet'.

On Tuesday, 23 October 2007, the space shuttle Discovery made a flawless launch and was on its way to dock with the ISS with its payload. Taking its name from Captain Cook's ship, HMS Discovery, the shuttle has, including the latest mission, flown 34 times – more than any of the other shuttles, logging just over 296 days in space in the process.


On this flight to the ISS, Discovery's prime job was to deliver the Harmony module, which would increase the pressurised volume of the ISS, for the first time since 2001, to 18,000ft². The Harmony module, of approximately 2,600ft³ of living space, is the permanent docking point for international laboratories from the European Space Agency and the Japan Aerospace Exploration Agency.

Mission STS-120's crew was made up of seven astronauts – mission commander Pam Melroy, pilot George Zamka, mission specialists Scott Parazynski, Stephanie Wilson, Douglas Wheelock and Italian Paulo Nespoli. A replacement crew member for the ISS, Daniel Tani, was also on board.

The mission was to be complicated but doable. First, move Harmony around to the left side of Node 1 for final positioning later. Secondly, continue to set up the station's exterior support truss and its power system. This task involved moving the ISS's first set of solar power arrays (P6 arrays) to a new and final position.

“The shuttle Discovery docked successfully with the ISS on 25 October.”

The ISS's robotic arm would be operating at the fullest extent of its design and mission commander Melroy was under no illusions about the challenge ahead. "It's the design-limiting case," she said. "It's the maximum capability of the robotic arm's reach, and there are no cameras out there. So our spacewalkers are going to have to be out there going, 'OK, a little bit to the right,' guiding the robotic arm operator."

Initial post launch checks on Discovery were fine and the shuttle docked successfully with the ISS on 25 October. The next day went well too. In a little over six hours mission specialists Scott Parazynski and Doug Wheelock installed the Harmony module to a temporary location on the ISS, prepared the P6 truss for relocating on Sunday, shut one of Harmony's window covers that had opened on launch and retrieved a non-working radio antenna.


Space activity is pioneering – make a plan, plan to change is the order of the day. Sunday, 27 October set the tone for the rest of the mission. Mission control added a new job, asking newly arrived flight engineer, Dan Tani to take a look at the starboard solar alpha rotary joint (SARJ); for the last six weeks or so friction in the joint had been detected during rotation for solar array positioning.

Wilson and Wheelock used the ISS's robotic arm to position the truss to a 'parked' position. In the meantime, spacewalking Parazynski installed handrails on Harmony while Tani checked out the SARJ where he found, wear patterns, metal shavings and one of the rings around the joint was discoloured. Collecting samples for later analyasis, Tani said: "It's like the result that you get with iron filings – you put a magnet under them and they stand straight up."

“In a little over six hours mission specialists installed the Harmony module.”

Monday, day seven, saw the confirmation that the shavings removed by Tani were indeed, ferrous metal. Mission managers decided to scrap the testing of the tile repair dispensing gun, tile repair ablator dispenser (T-RAD) scheduled for Thursday until another mission, opting for further inspection of the starboard SARJ instead; also adding an extra docked day to the ISS for Discovery. The crew spent the day preparing the P6 truss and working on systems inside the Harmony module.

During Tuesday's EVA (extra-vehicular activity), the P6 solar arrays were installed on the P5 truss and deployment commenced. The first set deployed, no problem, the deployment of the second set however was halted when a small tear was noticed; over 95% of the station's power was still available and proceedings were put on hold pending mission control analysis.

On Wednesday, the crew worked on preparations for the next EVA, experiments and installations in Harmony. Because of the solar array problem, mission control decided to put back Thursday's EVA to Friday or Saturday to allow more time for preparation. "We give this team a little time to start thinking about creative solutions, and it doesn't take them long to blow you away with what they come up with," said station programme manager Mike Suffredini.

With a solution in mind to fix the torn array, on Thursday and Friday the crew prepared for Saturday's job including fashioning tools dubbed as 'cufflinks', homemade stabilisers, designed to be load-bearing straps secured with wire and supported below by strips of aluminium, to take the weight off the tear.


The next day, waking up to the somewhat appropriate theme of Star Wars, Parazynski and Wheelock went out to repair the array with a toolkit reading somewhat like a children's project – pieces of aluminium, a hole punch, a bolt connector and 66ft of wire.

“The Harmony module increased the pressurised volume of the ISS, for the first time since 2001, to 18,000ft².”

It took around 90 minutes for the pair to ride the ISS's robotic arm out to the farthest part of the array where the astronauts worked for over four hours to complete the repair. It was the first time the robotic arm was operationally used to reach the jobsite, although the procedure was practiced in 2006.

Compared to Saturday the rest of the mission was a walk in the park and Discovery touched town on runway 33 at Kennedy's shuttle landing facility in Florida on Wednesday, 7 November.

"This mission demonstrates the value of having humans in space and our ingenuity in solving problems," said Bill Gerstenmaier, associate administrator for space operations, NASA Headquarters, Washington.

Gerstenmaier is right. Machines can do many things but thinking and acting 'out of the box' to make 'something out of nothing' is a human trait. Long may it continue.