National Aeronautics and Space Administration
Figure 3-2. Extravehicular Mobility Unit Components The Portable Life Support System (PLSS) (Figure 3-3) is made up of four distinct circuits: a) Oxygen Ventilation Circuit. b) Primary Oxygen Circuit c) Feedwater Circuit d) Liquid Transport Circuit These circuits provide suitable breathing environment and thermal control for the crewmember inside the Space Suit enclosure. The Primary Oxygen Circuit supplies oxygen at regulated pressure to the Oxygen Ventilation Circuit for crewmember breathing, SSA pressurization and expulsion of water from storage tanks in the PLSS. The fan portion of the fan/pump/separator, located in the Oxygen Ventilation Circuit, circulates the oxygen and gas exhaled by the crewmember through connecting ducts and items. The exhaled CO2 is removed from the breathing environment by a contaminant control cartridge. Cooling and humidity removal occurs as the oxygen circulates through the sublimator. Additionally, primary oxygen is also directed through ducting to pressurize the water storage tanks located in the Feedwater Circuit. The water storage tanks supply makeup water to the coolant loop as well as expendable water at regulated pressure to the sublimator. The Feedwater Circuit in the sublimator is open to atmosphere (vacuum) and, as the expendable water is fed into the sublimator, it freezes and then sublimates to space. This sublimation process removes heat from the Liquid Transport Circuit. The pump circulates cooling water through the Liquid Transport Circuit which includes the Liquid Cooling and Ventilation Garment of the SSA, worn by the crewmember. The water removes heat from the crewmember and is cooled by the sublimator.
Published on Feb 27, 2014
Report of the NASA Mishap Investigation Board examining the high visibility close call event of July 16, 2013 when ESA astronaut Luca Parmit...