CHAPTER 17 SYSTEMS: EXTRAVEHICULAR ACTIVITIES—BUILDING A SPACE STATION 282 built largely by shuttle crews that wore shuttle spacesuits. Figure 2. Astronaut Mark Lee tests the nitrogen-propelled backpack that would be needed for the ISS. Space Shuttle mission STS-64 (September 1994). During the ISS design development, NASA conducted specific Space Shuttle EVA experiments to determine acceptable ways to assemble a space station and understand new requirements for EVA equipment. This process included testing designs for assembling a truss structure and new EVA tools for an extravehicular crew member who had to maneuver around a large ISS structure. Although all ISS EVAs include having the crew member tethered by lifeline to its structure, shuttle crews tested a nitrogen-propelled backpack flown by extravehicular crew members using a joystick (Figure 2). This backpack—called Simplified Aid for EVA Rescue (SAFER)—can be used in case an