CHAPTER 17 SYSTEMS: EXTRAVEHICULAR ACTIVITIES—BUILDING A SPACE STATION 296 opposite direction, something that doesn’t happen on the Earth where a person’s feet anchor the body against these forces. Another stabilization tool is the Body Restraint Tether—a device attached to the EMU that clamps to a handhold on the ISS and can be made rigid to hold a crew member steady. This tether is actually a stack of balls with a cord through the middle and a tightening mechanism, similar to a shop light or camera mount. A computerized Pistol Grip Tool is comparable to a sophisticated power screwdriver or cordless drill used to install or remove bolts when precise torque or turns are required. In addition to specialized tools for some tasks, common tools that were made EVA-friendly include wrenches and sockets, bags to keep tools contained, cameras, trash bags, etc. A tool mount called a Mini-Workstation on the front of the suit contains often- needed tools, ready and within reach. Foot Restraint (boot tips go under loops) Bag for small tools Cart for moving larger items down the front face of the ISS truss Tethers Trash Bag Pistol Grip Tool Figure 17. This photo of astronaut Sunita “Suni” Williams was taken by astronaut Aki Hoshide during Expedition 32. A fairly standard quantity of tools can be seen on the front of her spacesuit, although each EVA requires a somewhat different complement of tools. Two versions of safety tethers are attached to D-shaped rings on the suit near the hips, and one of these has a take-up reel that houses a 26-m (85-ft) steel cable. This safety tether can be attached to the structure and allows the crew member to travel far without having to relocate his or her tether point. However, if the crew member were to let go with only this cable attached, he or she could float away from structure and possibly come back to impact an unintended area off of the ISS. Other tethers are often used in addition to safety tethers, once a crew member arrives at the work area. A Pistol Grip Tool (under Williams’ arm) has functions similar to a cordless drill used for bolting and unbolting equipment. She is holding onto a cart that can translate along the truss but is rarely used for this purpose. Extravehicular Activity Preparations and the Airlock For an EVA to be conducted, the crew has to get outside without taking the entire ISS cabin pressure down to vacuum. Thus, the suited- up EVA crew members go into a telephone booth-sized airlock that is depressed to vacuum just prior to the EVA. That small volume on the ISS that goes to vacuum is called the Crewlock, which is part