Extravehicular Mobility Unit

Extravehicular Mobility Unit
Name	Extravehicular Mobility Unit
Caption	Astronaut Bruce McCandless II testing the Manned Maneuvering Unit with the EMU during STS-41-B.
Manufacturer	ILC Dover (pressure garment), Hamilton Sundstrand (life support)
Missions	Space Shuttle program, International Space Station
First use	STS-6 (April 1983)
Retired	2024 (planned)
Successor	xEMU

Extravehicational Mobility Unit. It is an independent anthropomorphic system that provides environmental protection, mobility, life support, and communications for an astronaut performing extravehicular activity outside a spacecraft. Primarily used aboard the Space Shuttle and the International Space Station, it represents a significant evolution from the suits used during the Apollo program. The system's modular design allowed for its adaptation across decades of missions, from satellite servicing to the construction of the International Space Station.

Design and components

The system is a modular, semi-rigid suit consisting of two primary subsystems: the Pressure Garment Assembly and the Portable Life Support System. The Pressure Garment Assembly includes the hard Upper Torso, fabric Lower Torso, arms, gloves, and the iconic Protective Helmet Assembly. Key components like the Display and Control Module, mounted on the chest, allow the crewmember to monitor and control critical functions. Communications are handled via the S-band Extravehicular Activity Communications system, linking the astronaut to their crewmates and mission control at NASA's Johnson Space Center. For mobility and tool interface, the suit incorporates bearings at the shoulder, wrist, and waist, and is compatible with the Manned Maneuvering Unit and the station's Canadarm2.

History and development

Development began in the late 1970s at NASA following the success of the Apollo program and the Skylab missions, with the goal of creating a reusable suit for the new Space Shuttle program. The contract for the pressure garment was awarded to ILC Dover, while Hamilton Sundstrand developed the life support backpack. Its first operational use occurred during the STS-6 mission in April 1983, where astronauts Story Musgrave and Donald H. Peterson conducted the first shuttle-based spacewalk. The design proved its worth during critical missions like the STS-61 Hubble Space Telescope servicing mission and was continuously upgraded to support the extensive assembly tasks of the International Space Station throughout the 2000s.

Operational use

The unit enabled hundreds of spacewalks across the Space Shuttle program and operations aboard the International Space Station. Notable missions include the repair of the Hubble Space Telescope on servicing missions like STS-61 and STS-125, which required intricate suit maneuvers. During the construction of the International Space Station, astronauts from NASA, Roscosmos, the European Space Agency, and JAXA used it to install major modules like Kibō and Columbus. It was also instrumental in emergency repairs, such as those conducted during STS-120 to fix a torn solar array on the station's P6 truss.

Life support and systems

The Portable Life Support System provides a shirt-sleeve environment within the suit. It regulates oxygen pressure, removes carbon dioxide using a system of lithium hydroxide canisters, and controls temperature and humidity through a water sublimator. Electrical power is supplied by silver-zinc batteries, and a water reservoir provides cooling via the Liquid Cooling and Ventilation Garment worn by the astronaut. Critical safety features include a secondary oxygen pack for emergency purge and warning systems for pressure loss or coolant failure, designed to protect the crewmember in the vacuum of space.

Training and preparation

Astronauts train extensively in the suits at facilities like the Neutral Buoyancy Laboratory at Johnson Space Center, which simulates microgravity. Preparation for an actual spacewalk involves a lengthy pre-breathing protocol to avoid decompression sickness, often using the station's Quest Joint Airlock. Crews also practice specific tasks in the lab with high-fidelity mockups of hardware from the International Space Station. Final suit checks and ingress are assisted by fellow crewmembers inside the airlock, following procedures developed over decades by teams at NASA.

Variants and upgrades

Several configurations have existed, including the original Shuttle EMU and the enhanced ISS EMU with longer-life components. The Advanced Crew Escape Suit, used during shuttle launch and reentry, was a derivative of its pressure garment technology. Planned upgrades over the years included the "Series 4000" improvements and the development of the Exploration Extravehicular Mobility Unit, or xEMU, for the Artemis program and future missions to the Moon and beyond. The design legacy is also evident in suits developed by companies like SpaceX for the Crew Dragon program.

Category:NASA space suits Category:Space Shuttle program Category:International Space Station