On March 18, 1965, Soviet cosmonaut Alexei Leonov became the first human to leave a spacecraft and float in open space. His 12 minute 9 second spacewalk outside Voskhod 2 proved that astronauts could work beyond the protection of a cabin. This mattered because future missions would need people to inspect spacecraft, repair equipment, assemble structures, and explore the Moon.
The event also showed that spacewalking is not simple floating, but a demanding operation involving pressure, motion, life support, and risk.
Key Facts
- First human spacewalk: Alexei Leonov, Voskhod 2, March 18, 1965.
- Duration of Leonov's EVA: 12 min 9 s = 729 s.
- Orbital speed near low Earth orbit is about v = 7.8 km/s.
- For circular orbit, gravitational force supplies centripetal force: GMm/r^2 = mv^2/r.
- A tether provides a safety connection and can exert tension, modeled as F = T along the tether.
- Pressure difference creates force on a surface: F = P A.
Vocabulary
- EVA
- EVA means extravehicular activity, which is any astronaut activity performed outside a spacecraft.
- Tether
- A tether is a strong line that connects an astronaut to a spacecraft to prevent drifting away.
- Airlock
- An airlock is a sealed chamber that lets people move between a pressurized spacecraft and the vacuum of space.
- Pressure suit
- A pressure suit is a wearable life-support system that keeps a human body under safe pressure in space.
- Low Earth orbit
- Low Earth orbit is a region a few hundred kilometers above Earth where spacecraft travel fast enough to keep falling around the planet.
Common Mistakes to Avoid
- Thinking a spacewalking astronaut is weightless because there is no gravity is wrong because gravity is still strong in low Earth orbit and both astronaut and spacecraft are continuously falling around Earth.
- Forgetting the pressure suit can stiffen in vacuum is wrong because internal suit pressure pushes outward and can make bending arms, legs, and gloves difficult.
- Assuming a tether pulls an astronaut back automatically is wrong because a tether only provides a force when it becomes taut or is actively reeled or pulled.
- Treating the first spacewalk as routine is wrong because Leonov's suit expanded, reentry procedures became difficult, and the crew faced serious life-support and landing hazards.
Practice Questions
- 1 Leonov's spacewalk lasted 12 min 9 s. Convert this time to seconds, then find how far Voskhod 2 traveled during the EVA if its orbital speed was 7.8 km/s.
- 2 A circular spacecraft hatch has area 0.50 m^2. If the pressure difference across it is 40,000 Pa, what force does the pressure difference exert on the hatch? Use F = P A.
- 3 Explain why Leonov could float beside Voskhod 2 without falling behind it, even though both were moving around Earth at several kilometers per second.