MINIMUM COST CRITERIA FOR SPS TRANSPORTATION TO GEO Dietrich E. KOELLE, MBB Space Division, Ottobrunn/Germany The transportation of 50 000 tons (Mg) mass to GEO — as presently estimated for a 5 GW SPS — poses a great challenge to system design and technology, especially however to economic optimization. Required is a heavy cargo launch vehicle with more than 200 Mg payload in geosync, orbit (GEO), requiring up to some 250 launches for one SPS. A cost—optimized vehicle of this size seems to be able to realize a range of 50 to 150 $/kg (1980) specific transportation cost to GEO. This is more than two orders of magnitude lower than the Space Shuttle plus I US (23 000 $/kg). However, the range indicated means 2 to 6 Billion S launch cost for one 5 GW SPS, or about one third up to the same amount as the SPS space segment will cost. For this reason, a strict application of cost optimization has to be applied in vehicle design and not only a performance optimization as in the past. For a minimum cost heavy cargo launch vehicle the following ground rules can be established: (1) FULLY REUSABLE: The launch vehicle system shall not comprise any expendable components; the goal is 50 to 100 re—uses with minimum refurbishment. (2) UNMANNED: For heavy cargo transportation man Is not required. The pressurized cabin, the life support and safety systems are a payload penalty and increase cost. (3) TECHNICAL SIMPLICITY: Minimum technical complexity is required in order to limit development, fabrication and operations cost. This means minimum number of stages and system interfaces, no deployable tanks or boosters. Performance (payload) must be achieved by adequate sizing instead of increasing technical complexity. (4) OPERATIONS SIMPLICITY: Operations cost represent the largest cost share in case of fully reusable vehicles. Therefore, the design must take into account minimum launch, recovery and refurbishment effort. These ground rules can be applied to the vehicle design alternatives shown in FIG. 1: Winged vehicles are excluded because they need a flight crew and the associated equipment. This cer— tainly decreases the payload and increases cost. Because of the lower structural efficiency only two- stage systems can be considered. In case of unmanned ballistic vehicles a single stage system to LEO (SSTO) is feasible, however, with a lower payload than two—stage or 1 1/2 —stage systems. The latter need recovery of tanks or boosters, increasing system complexity and operations cost. Two—stage systems — either to LEO or into LEO/ GEO transfer orbit have a suborbital first stage. This means that the vehicle has to be recovered down—
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