The third body, the apollo spacecraft, is assumed to have

It is assumed to have a negligible mass compare with the two bodies. Its position is an undetermined function of time. The spacecraft position requires system of differential equations that was derived from the Newton's laws of motion and the inverse square law of gravitation. This is a three body system where a small mass orbits the two other bodies with much larger masses.

Spherical shaped cell might increase the surface area and decrease the volume.