It's a marvellous fact that the Apollo missions achieved escape velocity, or close enough that they could have done so with small design modifications. The ca

It's a marvellous fact that the Apollo missions achieved escape velocity, or close enough that they could have done so with small design modifications. The calculation is fun: The kinetic energy required to escape Earth's orbit entirely is: G M / R, where G is Newton's constant, M is the mass of the Earth, and R is the radius of the Earth. The kinetic energy required to get to the Moon is: G M / R - G M / r, where r is the distance to the moon. To compute the ratio of the second quantity to the first, note that the GM factors cancel. So the ratio is: (1/R-1/r) / (1/R) = 1 - R / r The distance to the moon is about 60 times the radius of the Earth. So: Kinetic energy required to get to moon / Kinetic energy required to escape Earth's orbit entirely = 1 - 1/60 ~ 98 %. In other words, the Apollo missions had at least 98% the kinetic energy required to escape Earth orbit's entirely.