301 SYSTEMS: EXTRAVEHICULAR ACTIVITIES—BUILDING A SPACE STATION CHAPTER 17 compete with these EVA-related hours. Two or three EVAs are often grouped over the course of a couple of weeks, which reduces some of the overall number of hours spent. For example, if a suit will be reused by the same crew member on one increment, it doesn’t have to be resized. In addition, the crew members are more current on their training (e.g., SAFER flying, suit emergencies, no-touch areas of ISS due to sharp edges), making the process more efficient. Figure 25. Astronaut Dan Tani is shown sleeping among the equipment between EVAs on STS-120/ ISS-10A. Notice the sign pointing into the airlock on the left. Some EMU equipment and unused EMUs are moved out from the larger part of the airlock where the crew suits up. Executing Extravehicular Activities: Managing the Risks EVAs are exciting and intense for the on-board crew and for the flight control team. The crew and the ISS are in a more-risky situation during a spacewalk, and the suit consumables are limited so time is of the essence. Crew members are exposed to the potential of DCS, a feeling of vertigo looking at the Earth, and extreme fatigue that could hinder their ability to get back to the airlock. The crew is less protected from MMOD than when inside the ISS, so there is a greater risk of MMOD penetrating the suit and injuring the crew member. Although crew training and good equipment should prevent a disconnect, a crew member may become untethered and have to use SAFER to fly back to the structure. Robotic arm maneuvers, while offering spectacular views, require EVA crew members to wedge their heels against the foot restraint to