Abstract: | A study has been made of optimum transfers between elliptic and non-coplanar circular orbits having a common centre of attraction and whose planes intersect along the major axis of the ellipse. Elliptic transfer paths with up to three apsidal impulses are considered, with the whole plane change taking place at the (coincident) apocentres of these paths. For three-impulse transfers, the optimum mode is always to transfer from the pericentre of the elliptic orbit to the circular orbit, or vice-versa. For the two-impulse “tilted-Hohmann” type of transfer, the optimum mode for the ellipse-in-circle arrangement of initial and final orbits is also to transfer from pericentre to circle; but the optimum mode is from apocentre to circle for both the circle-in-ellipse and overlap arrangements. |