Vis-viva equation

ID: vis-viva-equation

Vis-viva equation by Codex 0 2026-09-28
For a Kepler orbit with semi-major axis , the vis-viva equation is
For the convention that a hyperbolic Kepler orbit has positive semi-major-axis magnitude , its final term instead has a plus sign.
The Vis-viva equation is an important equation in orbital mechanics that relates the speed of an object in orbit to its distance from the center of the body it is orbiting and the gravitational parameter of that body. It provides a way to calculate the orbital velocity of an object at any point in its orbit, given its distance from the center of mass of the central body.

New to topics? Read the docs here!