A special type of path, capable of direct transfer between a low-altitude Earth orbit (LEO) and a low-altitude Moon orbit, with flight time between 13 and 15 days, could be of great interest for future lunar missions. This paper presents the results of the research on this type of path, and shows that these paths could be a good alternative for an Earth-Moon transfer, and also other kinds of transfer in Earth-Moon system. The origin of these paths is related to a family of generally unstable direct orbits around the Lagrangian equilibrium point L1, known as the Family G. These paths are predicted by the circular, planar, restricted three-body problem (PR3C) associated with the Earth-Moon system. The authors initially considered the restricted three-body Earth-Moon-probe problem to establish a set of initial conditions, close to the Earth, and final conditions, close to the Moon, in such a way that these conditions were related through an empirical mathematical expression. Next, they considered a more complex and realistic dynamical problem, the four-body problem Sun-Earth-Moon-probe, where they take into account the eccentricity of the Earth's orbit as well as the eccentricity and inclination of theMoon's orbit. An empirical expression related to the initial and final conditions of the paths continued to exist.On the other hand, the consideration of a more complex dynamical system opened up new lines of investigation with respect to the probe's inclination and speed on its final approach to the Moon. The existence of a well-defined set of paths, derived from the direct periodic orbits around the Lagrangian equilibrium point L1, and capable of carrying out a direct transfer maneuver between low-altitude terrestrial and lunar parking orbits has been verified. This set was graphically represented starting with injection velocity Vi(or velocity required to acquire the transfer path) versus the altitude of the terrestrial parking orbit, HT, for 160 <= HT <= 20000 km and with HL (altitude of the lunar parking orbit) <= 100 km, and via an empirical mathematical expression for 160 <= HT <= 700 km The numerical results found for PR3C are quite similar to those of the four-body problem. When compared to the conventional methods of Hohmann and patched conic, it can be seen that the paths studied have total relative velocities that are very close to those obtained by these methods. However, velocities found via conventional methods are not sufficient to conclude the maneuver, because they do not take into account the disturbances of the gravitational fields of the Sun, Earth, and Moon during the entire maneuver.
Alternative paths to Earth-Moon transfer
Alternative Flugbahnen für den Erde-Mond-Transfer
2006
20 Seiten, Bilder, 23 Quellen
Aufsatz (Zeitschrift)
Englisch
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