just for the sake of it...
kinetic energy = gravitational potential energy
1/2m1v^2 = Gm1m2/r
m1 = mass of satelite, m2 mass of planet.
So, by rearranging, v^2 = 2Gm/r,
so
escape velocity = sqrt (2Gm(e)/R), where G is gravitational constant, m(e) is mass of planet, R is radius of planet.