Extravehicular activity

Extravehicular activity (EVA) refers to any activity performed by an astronaut or cosmonaut outside a spacecraft beyond the Earth's appreciable atmosphere. The term most commonly applies to spacewalks made outside a spacecraft orbiting Earth (such as the International Space Station), but also has been used to describe lunar surface exploration performed by Apollo astronauts.

History

The first EVA was performed by Soviet cosmonaut Alexei Leonov on March 18, 1965, during the Voskhod 2 mission. Leonov spent 12 minutes outside the spacecraft, connected to it by a tether. The first American EVA was conducted by astronaut Ed White on June 3, 1965, during the Gemini 4 mission. White's EVA lasted approximately 23 minutes.

Types of EVA

There are two main types of EVAs:

• Unpressurized EVAs: These are conducted in the vacuum of space, requiring astronauts to wear a space suit to provide life support and protection from the harsh environment.
• Pressurized EVAs: These occur within a pressurized environment, such as the interior of a spacecraft or space station, and do not require a space suit.

Space Suits

Space suits used for EVAs are complex systems designed to provide life support, mobility, and protection. The most commonly used space suit for EVAs on the International Space Station is the Extravehicular Mobility Unit (EMU). The Russian equivalent is the Orlan space suit.

EVA Procedures

Before an EVA, astronauts undergo extensive training, including simulations in neutral buoyancy pools to mimic the microgravity environment of space. The procedures for an EVA include:

• Pre-breathing pure oxygen to prevent decompression sickness
• Donning the space suit
• Exiting the spacecraft through an airlock
• Performing the assigned tasks, such as repairs, maintenance, or scientific experiments
• Re-entering the spacecraft and undergoing post-EVA medical checks

Significant EVAs

Some notable EVAs include:

• The repair of the Hubble Space Telescope in 1993, which involved multiple spacewalks to replace faulty components.
• The assembly and maintenance of the International Space Station, which has required numerous EVAs since its construction began in 1998.
• The lunar surface EVAs conducted during the Apollo program, which included the first human steps on the Moon by Neil Armstrong and Buzz Aldrin during the Apollo 11 mission in 1969.

Challenges and Risks

EVAs pose several challenges and risks, including:

• Exposure to radiation
• The potential for micrometeoroid impacts
• The physical strain of working in a space suit
• The risk of equipment failure or loss of tether connection

Future of EVA

As space exploration advances, EVAs will continue to play a crucial role in missions to the Moon, Mars, and beyond. New technologies and space suit designs are being developed to enhance the safety and efficiency of EVAs for future missions.

See also

• Space exploration
• International Space Station
• Apollo program
• Space suit
• Neutral buoyancy

External links

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