EVA Space Suit Product

Overview

An EVA space suit is the smallest crewed spacecraft in service: a wearable pressure vessel with its own atmosphere, thermal control, communications, and consumables. The configuration described here follows the orbital EVA suits used on the Space Shuttle and International Space Station — a fiberglass Hard Upper Torso joined to a soft Pressure Garment Assembly, topped by the Helmet Assembly and supplied by the Primary Life Support System backpack. The complete unit masses about 145 kg, weightless on orbit but a major handling problem on the ground, and sustains a working astronaut for eight hours plus a 30-minute reserve.

The fundamental design compromise is pressure. At full cabin pressure a fabric suit balloons rigid and the crew member cannot bend a joint. The suit therefore runs at 29.6 kPa of pure oxygen — physiologically equivalent to cabin air because the oxygen partial pressure is preserved — at the cost of a pre-EVA prebreathe protocol that washes dissolved nitrogen out of the blood to prevent decompression sickness.

Pressure garment

The soft suit is a laminate of functions. The Pressure Bladder holds gas; the Restraint Layer over it carries every structural load, because an unrestrained bladder would stretch into a sphere. Outside both, the Thermal Micrometeoroid Garment stacks five to seven aluminized Mylar layers under an Ortho-Fabric shell, handling thermal extremes from −155 °C in shadow to +120 °C in sun and stopping micrometeoroid dust at several km/s.

Mobility comes from two devices used throughout the Arm Assembly and Lower Torso Assembly: the Suit Rotary Bearing, a sealed ball-bearing ring that lets a pressurized segment rotate almost freely, and the Fabric Joint, a convoluted joint cut so that bending changes internal volume as little as possible. Constant volume is the whole game — any joint that compresses gas when flexed springs back, and the astronaut fights it with every motion for eight hours. Crew are fitted using Sizing Ring Set in the arms and legs rather than fully custom garments.

Torso, helmet, and gloves

The HUT Shell is the structural hub: the Scye Bearing Ring shoulder openings, the Helmet Disconnect Ring, the backpack, and the chest-mounted Display and Control Module all bolt to it. The astronaut enters through the Body Seal Closure, pulling on the lower torso first and then diving up into the hanging upper half.

The Helmet Bubble is a fixed polycarbonate hemisphere; the head turns inside it rather than with it. Over it ride the gold-coated EVA Sun Visor, a clear Protective Visor, adjustable eyeshades, and LED floodlights for the 30-minute nights that come 16 times per orbital day. The Vent Pad washes fresh oxygen across the visor so exhaled CO2 never pools at the face.

Gloves are the hardest engineering in the suit and the only fully personal part of it. Each Glove Bladder is dip-molded over a cast of the individual hand, restrained by a Glove Restraint with a palm bar that stops ballooning, and covered by a Glove TMG with silicone fingertips. Hand fatigue limits real EVA work more than any other factor, and Fingertip Heater Set deal with the cold-soak that tools conduct into the fingers.

Life support

The Primary Life Support System closes three loops. The oxygen loop feeds the suit from the Primary Oxygen Tank through the Oxygen Regulator Stack; vent flow of about 170 L/min, driven by the Fan/Pump/Separator, carries exhaled gas through the CO2 Scrubber Cartridge and back. The water loop pumps chilled water through the Liquid Cooling and Ventilation Garment — 91 m of tubing against the skin in the Cooling Tubing Network network — picking up metabolic heat before it can reach the gas. Both loops dump their heat in the Sublimator, where feedwater from the Feedwater Tank freezes in a porous plate and sublimates directly to vacuum, rejecting up to ~590 W with no moving parts. The Suit Battery powers everything at 20.5 V.

Failure cases are covered by the Secondary Oxygen Pack pack: 30 minutes of independent oxygen at 41 MPa, used with the Purge Valve in an open-loop mode that cools and clears CO2 by simply flowing gas overboard while the crew member retreats to the airlock.

Operations

The crew member runs the suit from the DCM Panel, reading the mirror-imaged Suit Status Display with a wrist mirror. Voice and biomedical telemetry travel through the Communications System — the Communications Carrier Cap "Snoopy cap" microphones, the UHF Transceiver, and the Biomed Harness that lets flight surgeons watch heart rate and metabolic load throughout. A suit is certified, maintained, and resized on orbit as a fleet asset; the same HUT may serve many crew members over years of service.