Why do lower orbits have higher speeds?

Closer to the central body gravity is stronger, requiring faster motion to maintain a circular path. Speed scales as 1/√r.

Does this work for elliptical orbits?

For an elliptical orbit use the vis-viva equation v = √(G M (2/r - 1/a)). The circular formula is a special case where r = a.

About 1.022 km/s, consistent with its large orbital radius of roughly 384 400 km.

Determine the orbital speed of a body in a circular orbit using v = sqrt(G * M / r).

Orbital Radius

Central Body Mass

Orbital Velocity

7,672.32 m/s

Velocity (km/s)7.6723 km/s

Orbital Velocity vs Orbital Radius

For a circular orbit the gravitational pull provides exactly the centripetal force needed.

v = √(G M / r)

*G* = 6.674e-11 N m² kg⁻²

*M* = central body mass

*r* = orbital radius (centre-to-centre)

Higher orbits are slower; lower orbits are faster.

Find the speed of the ISS at about 400 km altitude (r = 6 771 km).

Calculate the time for one full orbit.

Find the speed needed to leave a gravitational field.

Compute satellite speed from altitude.