# orbital velocity

(redirected from*Orbital speed*)

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## orbital velocity

The velocity of a satellite or other orbiting body at any given point in its orbit. It is also the velocity required by a satellite to enter an orbit around a body. The orbital velocity,*v,*is given by the expression

*v*= √[

*gR*

^{2}(2/

*r*– 1/

*a*)]

*R*is the radius of the orbited body,

*r*is the distance from the center of mass of the system (i.e. from the approximate center of the primary),

*a*is the semimajor axis of the orbit, and

*g*is the standard acceleration of gravity. For a circular orbit,

*r*=

*a*and the circular velocity is given by

*v*= √(

*gR*

^{2}/

*r*)

To escape from an orbit *a * must tend to infinity and the escape velocity is then given by

*v*

_{e}= √(2

*gR*

^{2}/

*r*)

The orbital period for an elliptical orbit is given by

*P*= 2π

*a*

^{3/2}/√

*gR*

^{2}

## orbital velocity

[′ȯr·bəd·əl və′läs·əd·ē] (astronomy)

The instantaneous velocity at which an earth satellite or other orbiting body travels around the origin of its central force field.