A Note on Hohmann Transfer Velocity Kicks
A Hohmann transfer is a well-known spacecraft manoeuvre, initiated by a horizontal velocity kick Δv1, which effects a change from an original, say, circular orbit to the Hohmann transfer ellipse in its perigee, and completed by a second horizontal velocity kick Δv2 in the apogee, to eflect a change from the transfer ellipse to a final, say, larger circular orbit.
A velocity kick as mentioned above is apparently instantaneous, and free of any side effects, a very idealized concept, which, as it turns out, isfar removedfrom reality.
Recent investigations into Ward spirals have shed some light into how velocity changes can be brought about. It is shown that a vertical impulse component must be present to accompany a horizontal impulse in order to assure that the altitude remains constant during a horizontal velocity change.