What Is Orbital Velocity?
Orbital velocity is the speed an object must maintain to stay in a stable circular orbit around a celestial body. At this velocity, the gravitational pull exactly provides the centripetal force needed for circular motion. Too slow and the object falls; too fast and it escapes into a higher orbit or away entirely.
For low Earth orbit (about 400 km altitude), the orbital velocity is approximately 7.67 km/s (27,600 km/h). This means the International Space Station completes one orbit every 92 minutes. The orbital velocity decreases with increasing altitude because gravitational force weakens with distance.
Formula
Where v is orbital velocity, G is gravitational constant, M is central body mass, and r is orbital radius (body radius + altitude).
Orbital Velocities at Surface Level
| Body | Orbital Velocity (km/s) | Escape Velocity (km/s) |
|---|---|---|
| Moon | 1.68 | 2.38 |
| Earth | 7.91 | 11.19 |
| Mars | 3.55 | 5.03 |
| Jupiter | 42.1 | 59.5 |
Frequently Asked Questions
Why is escape velocity √2 times orbital velocity?
Orbital velocity balances gravitational potential with kinetic energy for a bound orbit (total energy = -GMm/2r). Escape velocity gives zero total energy (kinetic energy = gravitational potential). The ratio is always √2 for circular orbits, regardless of altitude or central body.
Can you orbit at any altitude?
Not practically. Below about 160 km for Earth, atmospheric drag is too strong for a stable orbit. The minimum practical LEO altitude is about 200 km. There's no maximum altitude, but very high orbits (beyond the Hill sphere) become unstable due to the Sun's gravitational influence.