Results of a Manned Over Pressurization Event in the Extravehicular Mobility Unit Space Suit Assembly



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48th International Conference on Environmental Systems


The Neutral Buoyancy Laboratory (NBL) is a 100 x 200 x 40 foot deep tank holding over 6 million gallons of water used to simulate weightlessness for Astronaut training. The maxim “Train Like You Fly” refers to the desire to have the suit perform, during training, as close as possible to how it performs during an Extra-Vehicular Activity (EVA), particularly with respect to mobility. Therefore, the Space Suit Assembly (SSA) used in the NBL is a downgraded hardware version of the flight SSA; it is not designed for the NBL environment or operations. A classification system defines the flight Space Suit Assembly hardware as Class I, and the NBL training hardware SSA as Class IIIW.

On July 20, 2017, during a manned training event in the NBL, the SSA was inadvertently over-pressurized to 22 psid; normal operating pressure being 4.3 psid. The suit subject was removed from the suit with no injury. The event was investigated by a NASA Mishap Team while all manned SSA use was halted for safety reasons. The Team investigated common causes and differences between the Class I and Class IIIW Extra-vehicular Mobility Unit (EMU). The investigation determined that the event was limited to Class IIIW hardware and its external flow-controlled open loop ventilation systems. The flight EMU is a pressure regulated closed loop ventilation system. This paper will examine the differences between the Class I and Class IIIW SSA hardware and provide details of the Mishap Investigation. Corrective actions taken to mitigate risk with hardware, operations, and hazard documentation will be discussed.


Jinny Ferl, ILC Dover
Stephen Anderson, ILC Dover
Mallory Jennings, NASA
Marques Lynch, SGT Inc.
Clark Groom, ILC Dover
Walter Fritz, ILC Dover
ICES400: Extravehicular Activity: Space Suits
The 48th International Conference on Environmental Systems was held in Albuquerque, New Mexico, USA on 08 July 2018 through 12 July 2018.


Neutral Buoyancy Laboratory, Over Pressurization, NASA Mishap Team, Space Suit Assembly