Calculating the Initial Orbital Speed of a Satellite

The initial velocity (relative to the object being orbited) of a satellite can be calculated as follows:

Vp = sqrt( (2 * G * M * Ra) / (Rp * (Ra + Rp)) )
Va = sqrt( (2 * G * M * Rp) / (Ra * (Rp + Ra)) )

G is Newton's constant of gravity (6.673e-11).
sqrt is the square-root-function.

Vp is the (relative) velocity at the periapsis.
Va is the (relative) velocity at the apoapsis.

M is the mass of the object being orbited (this is assumed to be far greater than the mass of the satellite).
Rp is the minimum radius (periapsis) of the satellite's orbit.
Ra is the maximum radius (apoapsis) of the satellite's orbit.

Note that when Rp and Ra are equal, Vp and Va are also equal (the orbit is a circle).

Orbital Velocity Calculator

Further information about the mechanics of orbits can be found at:
"Rocket & Space Technology" - ORBITAL MECHANICS

	Input:
Mass:		kilograms	This is the mass of the object being orbited (e.g. the earth).
Distance at periapsis:		meters	This is the minimum radius of the satellite's orbited.
Distance at apoapsis:		meters	This is the maximum radius of the satellite's orbited.

	Result:
Velocity at periapsis:		meters per second
Velocity at apoapsis:		meters per second

Orbital period:		seconds