Cosmic Velocity - Second to Mile per Second

The second cosmic velocity (Earth's escape velocity) is approximately 11,200 m/s (11.2 km/s), the minimum speed to escape Earth's gravity completely.

v₂ = √(2GM/r) = √2 × v₁ ≈ 11.2 km/s. Exactly √2 times the first cosmic velocity.

To km/h: × 3,600. To mph: × 25,000. 11.2 km/s = 40,320 km/h = 25,053 mph.

Moon missions, Mars missions, deep space probes (Voyager, New Horizons), and any mission leaving Earth's gravity well.

Apollo missions: ~11.2 km/s. Voyager probes: exceeded v₂ to leave solar system. New Horizons: launched at record 16.26 km/s (fastest ever from Earth).

Thinking you need this speed everywhere — you only need it at launch. In space, much less Δv is needed.

~11 km/s to escape Earth. √2 × orbital velocity. Remember: orbit ≈ 8 km/s, escape ≈ 11 km/s.

Mile per second measures statute miles traveled in one second. An extremely high speed unit used for spacecraft, missiles, and astronomical phenomena.

1 mi/s = 60 mi/min = 3,600 mph = 1,609.344 m/s = 5,793 km/h.

To mph: × 3,600. To km/h: × 5,793. To m/s: × 1,609.344.

Earth's orbital speed: 18.5 mi/s. Moon's orbital speed: 0.64 mi/s. Space shuttle orbital: 4.9 mi/s. Escape velocity: 6.95 mi/s.

Earth escape velocity: 6.95 mi/s (11.2 km/s). Solar escape (from Earth): 26 mi/s. Fastest spacecraft (Parker Solar Probe): 120 mi/s peak.

Underestimating how fast this is — 1 mi/s is 3,600 mph, incredibly fast. Confusing with mi/min (60× slower).

Think 'space speeds in miles.' 1 mi/s ≈ 1.6 km/s. To escape Earth: ~7 mi/s. Orbital speed: ~5 mi/s.