CHAPTER 17 SYSTEMS: EXTRAVEHICULAR ACTIVITIES—BUILDING A SPACE STATION 290 US Extravehicular Activity 23 Water-in-Helmet Incident During US EVA 23 on July 16, 2013, water entered astronaut Luca Parmitano’s helmet about an hour into the EVA. The crew, flight control team, and engineers on the ground did not understand the source of the water and initially thought it may have come from a leak in the drink bag. However, the increasing quantity and unknown source caused the flight control team to call for an early termination of the EVA. Parmitano started translating back to the airlock. On the way, the water migrated to his face, covering his eyes, ears, and nose. Since there was no gravity to pull the water away from his nose and mouth, he could potentially drown in space. His vision and communications were degraded, and he had to use his safety tether as a guide to get into the airlock. Both crew members made it back into the airlock. Via a series of hand squeezes, Chris Cassidy (the other crew member) confirmed Parmitano was okay while they performed an airlock repress and suit doffing. After the EVA, the crew reported approximately 1.5 liters (0.4 gallons) of water in Parmitano’s helmet. This quantity matched the amount that was later determined to be missing from the water tanks that fed the sublimator during the EVA. Looking back, it was clear that Parmitano nearly drowned in the suit, and that the quick actions taken by the crew and ground team saved his life. Prior to this incident, crew procedures did not mention what to do if this quantity of water was in the helmet. This is because spacesuit testing on Earth showed that the fan would shut down and the water system would close off if a large quantity of water entered the ventilation system. However, in a zero-gravity environment, water can form a thin layer on the wall of the fan housing, flowing along the wall without stopping the fan blades as it would on Earth. The teams realized this fairly soon after the incident and then focused on determining how the water had entered the ventilation system in the first place. Because the investigation was expected to take quite some time, the team worried about calling a halt to EVAs for several months. The team needed to have the ability to perform EVAs while the investigation was ongoing. Without knowing the failure’s exact cause (root cause), the team developed procedures to have the crew to take safing actions and return to the airlock if this happened again. A helmet absorption pad, which was attached by Velcro to the inside of the helmet, and a snorkel that extends from the crew member’s mouth down to the waist area were designed and quickly flown to the ISS. The EMU has a fan for oxygen ventilation, a pump for water circulation, and a water separator for condensation gathering that are coupled together through a common shaft and magnetism. The unit is called the Fan/Pump/ Separator (Figure 11). The water separator portion of the FPS in Parmitano’s suit had become clogged with tiny particles, causing water to back up and deposit into the fan. Planning and Training Extravehicular Activity Tasks When the external portions of the ISS were being designed, the engineers and managers often made compromises between how much time would be spent assembling or repairing a component via EVA versus the use of robotic or automated systems. Many factors had to be considered, including the complexity of performing a task in space by a human or a robotic arm, the mass or size of the item, the cost of manufacturing the hardware or software for each option, and of course the schedule. To reduce the amount of EVA time to assemble the ISS, engineers designed modules and some truss segments with automated bolts and power and data connectors to create a permanent interface. When possible, automated mechanisms deployed appendages such as antennas and solar arrays that had to be tucked down to a lower profile to fit in the cargo bay of the Space Shuttle. However, having a human perform a spacewalk allowed for lower-complexity designs with simpler bolts or mechanisms driven by powered drills that were held by EVA crew members. Also, an EVA crew could assist with human intervention to save the day when automated systems encountered a failure.