1. Definition

Extravehicular Activity (EVA) refers to any activity astronauts perform outside a spacecraft beyond Earth’s atmosphere. Commonly called a “spacewalk,” EVA is essential for spacecraft maintenance, scientific experiments, and assembly of structures in space.

2. Historical Background

  • First EVA: Alexei Leonov, USSR, March 18, 1965 (12 minutes outside Voskhod 2).
  • First American EVA: Ed White, Gemini 4, June 3, 1965.
  • Longest EVA: 8 hours, 56 minutes (NASA astronauts, 2001, STS-102).

3. EVA Equipment

Spacesuit (Extravehicular Mobility Unit - EMU)

  • Layers: Thermal micrometeoroid garment, pressure bladder, cooling garment.
  • Life Support: Oxygen tanks, CO₂ scrubbers, water supply.
  • Communications: Built-in radio systems.

Safety Devices

  • Tethers: Prevent astronauts from drifting away.
  • SAFER (Simplified Aid for EVA Rescue): Mini jetpack for emergency maneuvering.

Tools

  • Pistol Grip Tool: Battery-powered drill for bolts.
  • Restraints: Foot restraints, handrails for stability.

4. EVA Procedures

  1. Pre-EVA Preparation: Suit checks, depressurization of airlock.
  2. Egress: Astronaut exits spacecraft via airlock.
  3. Operations: Repairs, experiments, assembly.
  4. Ingress: Re-enter airlock, repressurize, suit removal.

5. EVA Environments

  • Low Earth Orbit (LEO): International Space Station (ISS) operations.
  • Lunar Surface: Apollo missions, Artemis program.
  • Mars Simulations: Analog missions on Earth.

6. Physiological Challenges

  • Microgravity: No up or down; movement requires careful planning.
  • Vacuum Exposure: Risk of decompression sickness, ebullism.
  • Temperature Extremes: −157°C (shade) to +121°C (sunlight).
  • Radiation: No atmospheric shielding; increased cancer risk.
  • Fatigue: Suits are heavy and restrict movement.

7. Practical Applications

  • Spacecraft Maintenance: ISS repairs, satellite servicing.
  • Scientific Research: Microgravity experiments, cosmic dust collection.
  • Construction: Assembly of space stations and telescopes (e.g., Hubble).
  • Planetary Exploration: Surface sample collection, habitat setup.

8. Memory Trick

EVA = “Every Venture’s Adventure”

  • Remember: Every time astronauts venture outside, it’s an adventure requiring careful planning, specialized equipment, and teamwork.

9. Common Misconceptions

  • EVA is effortless: Movement in microgravity is physically demanding and requires significant training.
  • Spacesuits are invincible: Suits can be punctured by micrometeoroids or debris; they provide limited protection.
  • Astronauts float freely: Tethers and restraints are always used to prevent drifting away.

10. Surprising Facts

  1. Astronauts lose up to 2 liters of sweat during a spacewalk due to the suit’s insulation and exertion.
  2. The EMU suit weighs over 130 kg on Earth, but is weightless in space.
  3. Spacesuit gloves reduce hand strength by up to 50%, making tasks like turning bolts extremely tiring.

11. Recent Research

A 2022 NASA study published in npj Microgravity found that extended EVAs may alter astronauts’ immune responses, increasing susceptibility to infection (Crucian et al., 2022). This highlights the importance of monitoring health during long-duration missions.

12. Diagrams

Spacesuit Layers

Spacesuit Layers Diagram

EVA on the ISS

Astronaut Performing EVA

13. EVA in Popular Culture

  • Movies: “Gravity,” “The Martian,” and “Apollo 13” depict EVAs, but often exaggerate risks and ease of movement.
  • Video Games: “Kerbal Space Program” allows simulated EVAs with realistic physics.

14. The Human Brain and EVA

The human brain has more connections than there are stars in the Milky Way (100 billion neurons, each with thousands of synapses). This complexity enables astronauts to process vast amounts of sensory data and make split-second decisions during EVAs.

15. Future Directions

  • Artemis Program: Lunar EVAs with new suits designed for dust protection and mobility.
  • Mars Missions: Development of suits for thin atmosphere and extreme temperatures.
  • Robotic Assistance: Use of drones and robotic arms to reduce human risk.

16. Summary Table

Aspect Details
Definition Activities outside spacecraft
First EVA Alexei Leonov, 1965
Equipment EMU suit, tethers, tools
Risks Radiation, temperature, fatigue
Applications Maintenance, science, construction
Research Immunology changes (Crucian et al., 2022)

17. References

  • Crucian, B., et al. (2022). “Immune system dysregulation during extended EVAs.” npj Microgravity. Link
  • NASA EVA Factsheet. Link

18. Study Questions

  1. What are the main physiological risks during EVA?
  2. How do astronauts prevent themselves from drifting away?
  3. What recent findings have been made about immune system changes during EVA?

19. Quick Recap

  • EVA is vital for space exploration and maintenance.
  • Requires specialized suits, tools, and training.
  • Presents unique physiological and technical challenges.
  • Recent research is improving safety and understanding of long-term effects.