The specific energy (energy per unit mass) of a space vehicle is composed of two components, the specific potential energy and the specific kinetic energy.
The formula for specific potential energy associated with a planet of mass M is given by
ϵp = − universal gravitational constant ×Mass / distance
ϵp = − GM / r
ϵp = specific potential energy
G = the universal gravitational constant (G = 6.67×10−11 m3 kg−1 s−2),
M = the mass of the body to be escaped
r = distance from the centre of mass of the body to the object.