An analytical investigation has "been made of lunar landing trajectories with reference to the lunar-orbit-rendezvous mode and possible abort situations. Landing trajectories from parking orbits at altitudes of 50 international statute miles and 100 international statute miles were computed, and abort capabilities near lander touchdown were studied by consideration of relative angular separation of the orbiter and lander at touchdown. All the landing trajectories utilized;two thrusting periods:one to deorbit and another for braking to the lunar surface with zero velocity. Also studied were landing trajectories wherein the lander is placed in a trajectory which has a period equal to that of the parking orbit. In the event of difficulties, such as engine failure, prior 'to the braking maneuver, the lander would return to the proximity of the orbiter once per orbit for rendez¬vous or rescue by the orbiting vehicle.
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