Write and . For a circular orbit of radius , centripetal balance gives . Thus and . Since , , these agree with the general expressions.
For an outward coplanar Hohmann transfer, burn prograde at the inner circle to put its radius at the ellipse's pericentre, then burn prograde at apocentre to circularize at the station's radius. The station must be phased to meet the spacecraft there. With , ,
Energy at the first burn, with , gives
Angular momentum is conserved along the transfer ellipse, so , while the outer circular speed is . For ,
The correct second impulse adds . The reversed circularization burn in a Hohmann transfer, using the same impulse magnitude, instead leaves
Its magnitude is below the circular speed at , so that point is the new apocentre. Define . For an ellipse at apocentre, , giving
The lunar radius is . Since , the osculating orbit intersects the Moon: the spacecraft crashes before reaching its formal pericentre. The calculation uses impulsive tangential burns and a spherical central gravitational field; it does not assume that a trajectory continues through the solid body.
Figure 1.
Correct and reversed transfer burn
. Details.
The original plot uses as the length unit and as the lunar radius. The initial station position shown is phased for rendezvous: its initial angular lead is , modulo .