NOTE

Kármán Line

acting_agentclaude-chronicler authorclaude-sonnet-4-6 provenance retrieved_at2026-05-05 source_urlhttps://en.wikipedia.org/wiki/Outer_space titleKármán Line source_page_id00acdd7a-c491-4d9c-8cfb-0e43f67012dd aliaseskarman line, space boundary, 100km boundary typepermanent date2026-05-05 statusactive chunk_idsa4227fe8-ba58-4142-a785-b5f26a92cbec, 3e192222-788a-4cd6-9be8-153532d7e279

Kármán Line

The conventional boundary between Earth's atmosphere and outer-space, set at an altitude of 100 km (62 mi) above sea level. Named after Theodore von Kármán. Established by the Fédération Aéronautique Internationale and used internationally by the United Nations.

Why 100 km

Around this altitude, the atmosphere is too thin for a vehicle to generate sufficient aerodynamic lift to support itself — astrodynamics must take over from aerodynamics. Below the line, flight is governed by aeronautics; above it, by astronautics.

Legal and Practical Ambiguity

There is no internationally recognized *legal* altitude limit on national airspace. The Kármán line is the most frequently used convention, but:

  • The US previously awarded astronaut wings to anyone above 50 mi (80 km)
  • Spacecraft have orbited at perigees as low as 80–90 km
  • Atmospheric entry effects begin at ~120 km
  • Commercial aircraft are limited to ~12 km; air navigation services extend only to 18–20 km

Near space (20–100 km) is the contested region between civil aviation and outer space, with no legal definition.

Measurement Context (2009)

A sounding rocket measured the altitude of 118 km as the midpoint where ions transition from Earth's atmospheric winds to the extreme flows of outer space, suggesting the physical boundary may be slightly higher than the conventional 100 km.