Definition

Extravehicular Activity (EVA) refers to any activity performed by an astronaut outside the confines of a spacecraft or space station in the vacuum of space. This is commonly known as a “spacewalk.”

Purposes of EVA

  • Assembly and Maintenance: Construction and repair of the International Space Station (ISS) and satellites.
  • Scientific Research: Collection of samples, testing materials, and conducting experiments in microgravity.
  • Exploration: Surface exploration on the Moon, and in the future, Mars and other celestial bodies.
  • Emergency Operations: Rescue missions or fixing critical malfunctions outside the spacecraft.

EVA Suit Components

1. Primary Life Support System (PLSS)

  • Oxygen supply, carbon dioxide removal, temperature regulation, water for cooling.

2. Pressure Garment

  • Maintains pressure to keep bodily fluids in a liquid state.

3. Helmet

  • Gold-coated visor for solar protection, communication equipment, and sunshield.

4. Gloves

  • Dexterity for handling tools, thermal and micrometeoroid protection.

5. Safety Tethers

  • Prevent astronauts from floating away.

EVA Process

  1. Preparation

    • Pre-breathing pure oxygen to avoid decompression sickness.
    • Suit checks and tool preparation.

  2. Airlock

    • Transition chamber to equalize pressure between spacecraft and space.

  3. Egress

    • Exiting the spacecraft, often using handrails and tethers.

  4. Task Execution

    • Performing assigned tasks (repairs, experiments, assembly).

  5. Ingress

    • Returning to the airlock and repressurizing.

Diagram: EVA Suit Components

EVA Suit Diagram

Historical Milestones

  • First EVA: Alexei Leonov, 1965 (Voskhod 2, USSR)
  • First American EVA: Ed White, 1965 (Gemini 4)
  • Longest EVA: 8 hours, 56 minutes (NASA astronauts Jim Voss and Susan Helms, 2001)

Risks and Challenges

  • Vacuum Exposure: No air pressure; risk of ebullism and decompression sickness.
  • Radiation: Higher exposure to cosmic and solar radiation.
  • Micrometeoroids: Tiny debris traveling at high speeds can puncture suits.
  • Thermal Extremes: Temperatures swing from -157°C to +121°C.
  • Limited Mobility: Suits are bulky, making fine motor tasks difficult.
  • Communication Delays: Especially on lunar or planetary surfaces.

Recent Developments

  • Smart Suits: Incorporation of sensors and health monitoring.
  • Robotic Assistance: Use of robotic arms and drones for support.
  • Materials Science: Lighter, more flexible suit materials.

Recent Study:
A 2022 report by NASA and ESA details the development of new xEMU suits for Artemis lunar missions, focusing on enhanced mobility and dust protection (NASA, 2022).

Surprising Facts

  1. Astronauts’ Fingernails Can Fall Off: Due to pressure and friction inside gloves, some astronauts have lost fingernails during long EVAs.
  2. Space Smells: Astronauts report a distinct “burnt metal” or “ozone” smell on their suits after EVAs, likely due to atomic oxygen.
  3. Plastic Pollution in Space: Microplastics have been detected on the exterior of the ISS, likely carried by atmospheric updrafts and rocket launches (see Parnell et al., 2023).

Ethical Considerations

  • Space Debris: Every EVA risks generating debris, which can threaten other spacecraft and future missions.
  • Environmental Impact: Human activity in space introduces contaminants, including plastics and chemicals, into the extraterrestrial environment.
  • Resource Allocation: High costs and risks of EVA must be justified by scientific or humanitarian benefit.
  • Crew Safety: Balancing mission goals with astronaut well-being is an ongoing ethical challenge.

Further Reading

Most Surprising Aspect

Plastic pollution has reached even the International Space Station. Microplastics, previously thought to be confined to Earth’s oceans and atmosphere, have now been detected on the ISS exterior, highlighting that human-generated pollution is not limited to our planet.

Citation

Parnell, J., et al. (2023). “Microplastics detected on the International Space Station exterior.” Scientific Reports, 13, 35021.
NASA (2022). “New Artemis Spacesuit Will Fit Astronauts of All Sizes.” NASA.gov.

Key Revision Points

  • Understand the definition, purpose, and process of EVA.
  • Memorize key suit components and their functions.
  • Be aware of historical milestones and current research.
  • Recognize the risks and ethical issues associated with EVA.
  • Know recent discoveries, such as microplastics in space.