Hard Upper Torso
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A Hard Upper Torso Assembly, or HUT, is a central component of several space suits, notably Roscosmos' Orlan and NASA's Extravehicular Mobility Unit (EMU). The fiberglass HUT forms a rigid enclosure about the upper body of the occupant, providing pressure containment for this part of the body. The HUT incorporates structural attachment points for the arms, Lower Torso Assembly (LTA), helmet, chest-mounted Display and Controls Module (DCM), and Primary Life Support Subsystem (PLSS) backpack.
The original HUT design for the EMU, first used in 1980, included bellowed shoulder bearings, which allowed for variation in the angle of the shoulder bearings. This allowed for one configuration to ease donning of the suit, and a different configuration to allow maximum mobility during EVA. However, the limited life of the bellows prompted a redesign in 1990 to a fixed shoulder bearing angle and position, referred to as the Planar HUT, resulting in reduced mobility and more difficult donning and doffing.
Because of the high cost of manufacturing, only three sizes of HUTs are produced for the EMU. This has the effect of limiting the number of people who can be properly fit for the suit. The three HUT sizes are supposed to accommodate occupants from the 5th to the 95th percentile.
The HUT also includes an In-Suit Drink Bag, with a plastic tube extending into the helmet, to allow the astronaut to stay hydrated.
--The OpenLuna HUT --
The current plan for the OpenLuna HUT is that it will contain the counter-lungs, (allowing the system to operate more independently of the air purification system) several medical devices, and will provide a connecting point for the lacing system. It is currently being developed as a front entry and bottom entry device, rather like a SCUBA tank. It will contain an integrated helmet for C-Spine protection, with a removable front mask. As such, this wiki page contains the jumping off point for the helmet. The PLSS will hang from the back, and will attach to the suit by concealed hoses that will allow the operator to remove it without depressurizing the suit, and will allow extension hoses and external tethering and buddy breathing.
Current plans call for each suit to be custom made for specific suit operator (or just Operator) using 3D body scanning, then a vacuum forming mold will be made from the scan (allowing room for the counter-lungs and other medical devices, and allowing some room for body size change from reduces gravity or - other considerations) and the HUT will be "Vac-formed" out of HDPE (High Density Poly-Ethylene) for it's radiation shielding properties.