311 DAY IN THE LIFE: RISKY AND REWARDING SPACEWALKS—SPACE SHUTTLE MISSION STS-120/ISS-10A CHAPTER 18 since the Columbia accident in 2003, NASA had worked hard to develop a method to repair the delicate heat- dissipating tiles that protected the orbiter during reentry into the Earth’s atmosphere. (This was in addition to wing leading edge repairs, which required different materials.) The tile repair material was a consistency somewhere between peanut butter and toothpaste. The crew would apply the repair material to damaged tiles, and the material would harden to the firmness of a pencil eraser and insulate (via specifically formulated properties) the orbiter during its super-heated reentry. This material was squirted out of a container called the Tile Repair Ablator Dispenser (T-RAD). The new EVA was labeled the T-RAD Detailed Test Objective. Most EVAs are planned, preflight, over the course of months or even years however, the operations team was asked to quickly finalize a tile repair test procedure because of the criticality of the test and the familiarity of the team and crew with the tile repair testing. A debris strike had damaged a tile during the STS-118/ISS-13A.1 mission that flew in August 2007. The level of speculation about tile repair capability prompted Space Shuttle Program management to conduct an official test as soon as possible. The team was able to develop this EVA within a few short weeks using some already-developed techniques that were familiar to the crew. Parazynski happened to be on the EVA Thermal Protection System repair collaborative team, as was the STS- 120 lead EVA officer Dina Contella. Putting the experiment on this flight with quick turnaround was acceptable for the STS-120 operations team in terms of the limited training required. In fact, it seemed serendipitous that the team that worked so hard on creating this capability would get to execute the on-orbit test. The team agreed to insert the tile repair test spacewalk after P6 installation (EVA 3) and before the increment crew Node 2 EVA. As discussed in Chapter 4, long missions with a number of spacewalks can be very tiring to the crew. This Detailed Test Objective EVA would be shorter than usual (4 hours) to better allow for spacewalks on back-to-back days without exhausting the crew. When Discovery lifted off on October 23, 2007, the spacewalks had evolved from the original three planned EVAs to five EVAs. It was to be the first ISS docked mission with five planned EVAs and the first mission with five different EVA crew members. Flight Days 1-3 (Tuesday, October 23 through Thursday, October 25) Outboard (rotates) S3 SARJ (covered in MLI) Inboard Figure 5. S3 SARJ (circled) rotates the outboard segments to point the solar arrays at the sun. The EVA crew was tasked with inspecting this SARJ to determine the source of increased motor current. STS-120 launched on Tuesday, October 23, 2007. The mission proceeded with a normal early mission timeline, including checkout of the spacesuits on October 24 (Flight Day 2). On October 25, the day the shuttle was performing a rendezvous with the ISS, the operations team was approached about adding a new EVA task to the mission to have the crew look at the starboard Solar Array Rotary Joint (SARJ) (Figure 5). This huge round gear measures 4 m (13 ft) in diameter and is driven by a motor to enable the solar arrays on the end of the truss to track the sun via rotation of the entire end of the truss. The engineering community had seen some slightly increased currents (~0.1 amp, with intermittent changes up to 0.8 amp) associated with the motor. Video indicated that the arrays