THREE-DIMENSIONAL TRAJECTORY ANALYSIS FORnROUND-TRIP MISSIONS TO VENUS

摘要

For orbit-to-orbit round-trip missions to Venus, the dependence of mission velocity-increment requirements on mission time, wait time, at¬mospheric braking, and synodic period of departure was investigated. The analysis is characterized by noncoplanar, elliptical planetary or¬bits;successive two-body approximations;and impulsive velocity incre-ments. Round trips from 100 to 780 days and wait times from 40 to 510 days were studied for departure dates in 1979 and 1980.nThe velocity-increment requirements for each round trip were based on three modes of operation:(l) atmospheric braking on arrival at Venus and Earth, (2) atmospheric braking on arrival at Earth, and (3) all propulsive braking. All three velocity-increment summations were mini¬mized for each mission time.nThe dependence of velocity-increment requirements on mission time was such that a number of local minimum values of velocity-increment re-quirement occurred for mission times between 100 and 780 days. One of these minimums was for a mission time of about 460 days and a wait time of 40 days. A lower minimum occurred for a mission time of about 760 days and a wait time of 450 days. With atmospheric braking, the differ¬ence between these minimum values decreased. This trend may be signifi¬cant in deciding between a long and a short round-trip mission to Venus.nFor missions between 100 and 630 days, increasing the wait time in¬creased the velocity-increment requirements. For missions between 630 and 780 days, however, increasing the wait time decreased the velocity-increment requirements.nThe effect of synodic period of departure on velocity-increment re-quirements may be neglected for preliminary planning of round-trip mis-sions to Venus.