Orbital Insertion Velocity Calculator

Orbit Is Falling and Missing the Ground

A circular orbit exists at exactly the velocity where an object's forward motion carries it as far around the curve of the Earth as gravity pulls it down — too slow and it falls back to the surface, too fast and it flies outward into a higher orbit. That balance point depends only on Earth's gravitational parameter and the orbital radius, which is why orbital velocity decreases predictably as altitude increases.

The Formula

GM is Earth's standard gravitational parameter (3.986 × 10¹&sup4; m³/s²), and r is orbital radius — Earth's mean radius (6,371 km) plus altitude above the surface.

Where This Calculation Matters

• Launch vehicle targeting — a rocket's guidance system has to reach both the target altitude and the exact circular velocity for that altitude; falling short on velocity produces an elliptical orbit that decays.
• Satellite constellation design — orbital velocity determines orbital period, which drives coverage patterns for communication, navigation, and imaging constellations.
• Geostationary placement — a satellite must reach precisely the velocity that matches Earth's rotation at geostationary altitude to appear fixed over one point on the ground.
• Rendezvous planning — two spacecraft meeting in orbit must match not just position but velocity, which starts from knowing the circular velocity at the target altitude.

Orbital Velocity by Altitude

Orbital velocity falls as altitude rises — a geostationary satellite moves roughly 2.5 times slower than one in low Earth orbit, even though it travels a much greater distance per orbit.

How to Use This Calculator

1. Enter the altitude above Earth's surface in kilometers.
2. Select Calculate to get the required circular orbital velocity in meters per second.

Related Calculations

Budget the delta-v needed to reach that velocity with the Delta-V Calculator, or check the launch vehicle's thrust margin with the Thrust to Weight Ratio Calculator.