Spacewalk

Spacewalk
NASA · Public domain · source
Name	Spacewalk
Firstperformed	1965
Performedby	Alexei Leonov, Ed White
Location	Low Earth Orbit, Extravehicular Activity

Spacewalk is the activity of an astronaut exiting a pressurized spacecraft into outer space to perform work, inspection, assembly, or experimentation. It involves complex coordination between crew, ground control, and robotic systems from agencies such as Roscosmos, NASA, European Space Agency, JAXA, and Canadian Space Agency. Spacewalks have enabled construction of orbital platforms like the International Space Station and servicing of spacecraft such as the Hubble Space Telescope.

Definition and Terminology

"Extravehicular activity" (EVA) is the formal term adopted by NASA and other agencies; related terms include "extra-vehicular mobility unit" and "tethered operations". Historical nomenclature includes "spacewalk" popularized in media coverage of early EVAs by Soviet Union and United States programs. Specific subtypes include "stand-up EVA", "tethered EVA", "untethered EVA"—the latter exemplified by operations using the Manned Maneuvering Unit—and "internal transfer" EVAs during missions such as Skylab and Mir dockings.

History and Milestones

The first human EVA was performed by Alexei Leonov in 1965 from the Voskhod 2 spacecraft, followed months later by Ed White on Gemini 4. Milestones include the first untethered maneuver using the Manned Maneuvering Unit on STS-41-B, the first long-duration series of EVAs during Skylab and Mir programs, and the extensive assembly and maintenance EVAs during the International Space Station era. Servicing missions to the Hubble Space Telescope by Space Shuttle crews marked a shift from short inspections to complex repair and upgrade tasks. National programs such as Roscosmos's Salyut missions and cooperative ventures including Shuttle–Mir illustrated geopolitical and technical evolution.

Equipment and Suits

Primary EVA hardware centers on pressure suits like the Extravehicular Mobility Unit used by NASA and the Orlan suit employed by Roscosmos. Suits integrate life support systems, thermal control, micrometeoroid protection, and communication systems developed with contributions from contractors tied to Boeing, Lockheed Martin, and Collins Aerospace. Tools include tether assemblies, portable life support backpacks, foot restraints, and specialized payload handling fixtures used on programs such as STS-88 and Expedition missions. Airlock systems vary by vehicle: the Quest Joint Airlock on the International Space Station, the Shenzhou airlock for Chinese EVAs, and adapted modules during Space Shuttle flights.

Procedures and Safety

EVA procedures are choreographed through mission planning by Mission Control Center teams including Johnson Space Center flight controllers and international partners at TsUP. Pre-breathe protocols to avoid decompression sickness often reference protocols used in Gemini and Apollo programs, and involve staged oxygen exposure and prebreathe exercises conducted inside the spacecraft or the Airlock. Safety measures include umbilical tethers, SAFER jets from NASA development, redundant suit systems, and contingency plans drawn from incidents such as the STS-49 capture and the Mir collision responses. Training uses neutral buoyancy facilities like the Neutral Buoyancy Laboratory and virtual reality rigs at centers including ESA's facilities and JAXA's training centers.

Notable Spacewalks and Records

Historic EVAs include Alexei Leonov's first excursion, Ed White's early American EVA, and repair EVAs by Michael Massimino and John Grunsfeld on Hubble Space Telescope servicing missions. Records include cumulative EVA time holders from NASA and Roscosmos crewmembers participating in long-duration Expedition rotations on the International Space Station, and milestones such as the first Chinese EVA performed by Zhai Zhigang during the Shenzhou 7 mission. High-profile operations include STS-88 station assembly, Expedition 61 thermal shield repairs, and emergency EVAs prompted by micrometeoroid impacts observed in missions tied to STS-107 investigations.

Effects on Humans and Physiology

Human physiology during EVA is affected by microgravity, vacuum exposure risks, radiation from sources such as Van Allen radiation belt transits, and fluid redistribution altering cardiovascular function—phenomena studied extensively by NASA and researchers at institutions like Wyle Laboratories and Aerospace Medical Research Center. Bone density loss, muscle atrophy investigated in bed rest studies at clinics associated with European Space Agency research, and neurovestibular adaptation are mitigated through in-flight exercise regimes and suit countermeasures. Psychological stressors examined by investigators at Johnson Space Center and universities influence selection and training for complex EVA tasks.

Future Developments and Technologies

Emerging systems under development by organizations including NASA, SpaceX, Blue Origin, and Roscosmos aim to support EVAs beyond low Earth orbit for missions to Moon destinations under Artemis and for prospective Mars surface operations. Next-generation suits such as NASA's xEMU, international modular airlock proposals, autonomous robotic assistants from groups like Canadian Space Agency robotics teams, and advanced propulsion-enhanced maneuvering units are planned to expand capabilities. Technology demonstrators funded through programs like NASA Innovative Advanced Concepts and collaborations with industry partners point toward integrated surface EVA systems, plasma shielding concepts, and in-situ resource utilization tools for sustained off-world operations.

Category:Extravehicular activity