CHAPTER 17 SYSTEMS: EXTRAVEHICULAR ACTIVITIES—BUILDING A SPACE STATION 300 can also be pumped up to 413 mm Hg (8 psi) beyond the standard cabin pressure to help collapse bubbles in the crew member’s body. The flight surgeons in the control center will make medical recommendations while the EVA flight controllers work with the other crew members on the steps for installing and operating a device to allow the pressure of the suit to get this high. Quite a bit of overhead is involved in performing spacewalks (Figures 24 and 25), with more than 100 on-board crew hours logged before and after EVAs. Time is spent configuring the suits, preparing the tools with the exact complement needed (the astronaut cannot go back inside the ISS to grab a missing tool), studying the spacewalk (which may take place months after the last training run or is a contingency timeline that the crew never actually simulated), conducting refresher training on failures that could occur, discussing the robotics interaction with the EVA crew, and discussing the details with the ground team. The EVA flight control team will also collectively spend hundreds of hours planning and executing these activities. Airlock Umbilical that mates to the front of the EMU before and after EVA Airlock Control Panel (bags of tools are floating above it) Figure 24. The Crewlock is crowded with two crew members, tools, bags, and spare parts. Shirtsleeve crew members essentially stuff the crew in, with one crew member facing the hatch to be able to open it for egress to space and the other crew member facing a panel to operate the airlock. This is a photo of astronaut Rick Mastracchio (astronaut Clay Anderson’s feet are also shown) during STS-131/ISS-19A while the Space Shuttle was docked to the ISS. The Wall of EVA needed for ISS assembly required countless hours of preparations both on the ground and in space—and that was after all of the preflight ground testing and training. With the ISS in steady- state operations, science objectives