CHAPTER 18 DAY IN THE LIFE: RISKY AND REWARDING SPACEWALKS—SPACE SHUTTLE MISSION STS-120/ISS-10A 318 3. Repair Materials Had To Be Crafted On Orbit The solar array specialists, structural loads analysts, EVA team, and the crew’s maintenance instructors tried to find any available materials on orbit that could clear a snarl of wires and permanently sew together the panels that had come apart at the hinges. Clearing or cutting the snag could likely be done using available US and Russian EVA tools however, EVA tools would not do the trick for repairing the hinges. Looking back, this effort was similar to the famous scene in the movie Apollo 13 when ground controllers had to figure out how to build a carbon dioxide filter out of parts available to the crew. Using array parts on the ground and gathering a pile of various materials available inside the ISS, the flight control and engineering team came up with an ingenious solution. Special straps that could hold the panels together were proposed, taking advantage of intentionally designed holes on each side of the hinges (a thick pin was inserted into these holes to stabilize the arrays for launch, but the holes were not used after a standard array deploy). Five straps of three different lengths—89 to 165 cm (35 to 65 in.)—would hold the panels together the way tuxedo cufflinks work. Each end fed through a hole on opposite sides of the separated hinge lines. Crew members had to manufacture the straps out of a sheet of aluminum, some wire, and some tape. They cut the aluminum into 10 cm (4 in.) long and 2 cm (0.75 in.) wide strips, punched holes in the aluminum using a hand punch, created the specific length needed using 12-gauge wire, made an EVA tether point, and wrapped everything in tape (see Chapter 16). The developed technique was then tested on the ground (Figures 13 and 14). The cufflink that was produced on orbit is shown in Figure 15. Launch pin holes that are not used after the array comes out of its blanket box. These were used as attach locations for the straps holding the array panels togethe array panels together. “Cufflink” straps that would hold the panels together despite the damage Figure 13. Hardware engineers and analysts discuss the repair during STS-120/ISS-10A while looking at the solar array ground unit. This photo provides some scale, when the array is compared to a human. A full Solar Array Wing would measure 35 m (115 ft) in length. 4. Electric Shock and Sharp Edges Hazards One of the most challenging aspects involved the safety of a spacewalking crew member working around the solar array. Unlike Orbital Replacement Units, which were discussed in the Introduction and Chapter 16, the arrays were not meant to be repaired by an EVA crew member. These arrays have sharp areas, which could puncture or cut the spacesuit. Plus, in this case, there were a lot of “unknowns” about the damage and what could be sharp in that snag point. Most significantly, a solar array carries enough electric charge to electrocute the crew member in the spacesuit. Team members had to methodically think of everything that could lead to an electric current getting to the crew member, and to keep those scenarios from happening. The electrical power systems flight controller can reconfigure the electrical power system to reject energy from some areas, but no one can prevent the solar cells from becoming energized. The concerns were numerous regarding the electrical aspect. Could crew members actually be electrocuted if they touched the damaged area? Could metal parts heat up and turn molten, such that a drop could come off and burn a hole in the spacesuit? Could