3.4 THE IMPACT OF LAUNCH SITE ON ORBITAL OPERATIONS The launch site should, if at all possible, be selected in plane with the final destination orbit. This greatly simplifies operations and at the same time considerably decreases delta V requirements. Having the launch site at the latitude of KSC when the final orbit is equatorial requires a 28.5° plane change during the orbit transfer. Making this plane change requires an additional delta V of at least 4000 fps over the simple in-plane transfer. This is the additional delta V quoted in the literature. It requires out-of-plane thrusting during each orbit of the entire flight. Another option is an in-plane transfer to geosynchronous altitude with the plane change Deing made at that point. This requires 5,000 fps delta V for the plane change but the operations are simplified somewhat. Trip times are increased by more than just the extra delta V that must be input to the system. Even with lateral thrust applied during the climb to altitude much of the plane change remains to be made after synchronous altitude is reached. Delta V for this plane change can only be applied close to the nodes of the two orbits. This means thrusting is occurring only 1/3 to 1/5 of the time. The net result is that the 28.5° plane change could more than double total flight time for the low thrust transi t. G&N would be significantly complicated by the introduction of a large plane change, requiring three dimensional operation rahter than two dimensional. All of this is eliminated by a launch site in plane with the final orbit. There are also other advantages to low inclination launch sites such as; multiple launch opportunities, somewhat increased launch vehicle payload, and multiple rescue opportunities. These factors are discussed elsewhere. 3.5 OCCULTATION EFFECTS AND IMPACT ON SELF-ELECTRIC POWERED VEHICLE Because the transfer starts from a low Earth orbit at a (relatively) low inclination, the vehicle spends a portion of each of at least the low altitude orbits in the Earth shadow (night). This occulta- tation of the sun every few hours creates a special problem for the self-powered electric vehicles. For these cases at least part of the SSPS is generating power for use by the thrusters. Thus, the entry into Earth's shadow and reemergency into sunlight represents a shut-down and start-up of a gigawatt level power system with the attendant mechanical and thermal shocks. There is also the problem of attitude control loss during occultation. The severity of this problem is not yet established. If the transfer plane contains the earth-sun line, shadow passage would occur during every orbit all the way out to geosynchronous
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