🌌 Kármán Line — Where Does Space Begin?

Drag the altitude slider to explore how atmospheric density, aerodynamic lift, and orbital speed change with height. The Kármán Line (~100 km) marks where the air is too thin to provide meaningful aerodynamic lift at any speed — and any aircraft would need to travel orbital velocity just to stay aloft.

Probe Settings

Altitude 80 km Wing area (m²) 30 m² Aircraft mass (t) 15 t Lift coeff C_L 0.50

Zone

—

Telemetry

Altitude—

Air density ρ—

Pressure p—

Orbital speed—

Min. lift speed—

Lift ≥ orbit speed—

Physics:
ρ(h) = ρ₀·exp(−h/8500)
L = ½·ρ·C_L·A·v²
v_orbit = √(GM/r)
Kármán: v_lift = v_orbit

Legend

━ Density profile
━ Min. lift speed
━ Orbital speed
✦ Kármán Line ≈100 km
⊕ Your probe altitude

The Kármán Line Explained

Hungarian-American physicist Theodore von Kármán calculated that above approximately 100 km altitude the atmosphere becomes so thin that an aircraft would need to travel at orbital velocity (≈7.9 km/s) just to generate enough lift to support itself. At that point, it is no longer "flying" aerodynamically — it is orbiting. The Fédération Aéronautique Internationale (FAI) adopted 100 km as the official boundary of space. Below this line, lift > gravity is possible with sub-orbital speeds. Above it, only rocket thrust can maintain altitude. The US Air Force uses 80 km (50 miles) as its own boundary, which is why some X-15 pilots were awarded astronaut wings for reaching that altitude.