1. Figures 2-8 summarize the results of 72 iterated solutions covering four orbital periods. An examination of the optimum orbit transfer maneuvers reveals several interesting characteristics.
2. This abrupt change in character of the optimum steering program is made more evident in Fig. 5 by rescaling the time of each solution so that a comparison may be made on a common normalized time scale. When this is done, it becomes obvious that between Tf - IT and r/ = 4?r/3 the time variation becomes more abrupt. A closer examination reveals that there exists a discontinuous solution at T/ - 1.21637T for which 6 changes instantaneously from 90° to - 90° at the midpoint of the maneuver. The instantaneous change also could be interpreted to be from 90° to 270°. This thrust steering "corner" is discussed in further detail by Leitmann17and Faulkner.18It is the only discontinuous solution encountered for circle-to-circle orbital transfer and is brought about at ^ rf by the simultaneous vanishing of A and B in Eq. (38).
3. Dynamic Problems of Interplanetary Flight