ARRIVAL AND DEPARTURE IMPULSIVE DELTA-V DETERMINATION FOR PRECESSING MARS PARKING ORBITS

The arbitrary assumption of using tangential periapsis burns at both M ars arrival and departure, without considering the actual geometry bet ween the parking orbit and the inbound and outbound hyperbolic asympto tes, can lead to a misleading estimate of the initial low-Earth orbit departure mass of the Mars vehicle. However, performing a detailed sim ulation where the actual arrival and departure geometries are analyzed would require extensive computation times. Therefore, in an effort to obtain a realistic estimate of the initial low-Earth orbit mass witho ut sacrificing computation time, the method outlined in this paper was developed. This method, which builds on previous work, considers the actual geometry between the inbound and outbound hyperbolic asymptotes and the parking orbit, along with the precession effects caused by th e oblateness of Mars, in calculating the arrival and departure DELTAV values. Thus, a realistic estimate of the vehicle mass in low-Earth or bit can be produced. Three different mission scenarios representing al ternatives to the arbitrary assumed tangential periapsis burns are pre sented: 1) a tangential periapsis arrival and an in-plane departure; 2 ) an in-plane arrival and an in-plane departure; and 3) a tangential p eriapsis arrival and a three-dimensional departure (i.e., a departure burn with an in-plane and an out-of-plane DELTAV component). The resul ts obtained by this method compared very well for all three cases with a trajectory integration code, where the differences in the initial l ow-Earth orbit mass were within one percent. The computation times for the first and third mission scenarios were on the order of a few CPU seconds, while the second mission scenario required a few minutes of C PU time. Therefore, the present method would be an ideal tool for prel iminary mission design, as it reduces the computation time of the anal ysis with only minimal loss in accuracy.