range in the Atlantic and brought back by ship to the launch site. The direct injection into GEO/LEO transfer orbit is unfavorable because either an expendable kick stage is required or a third stage which has re-entry and landing capability of its own. The most simple solution both technically and from the operations standpoint seems to be the SSTO + OTV version. For verification a performance and cost analysis was performed for three types of vehicles, as shown in FIG. 2. (This is a model comparison only for concept evaluation). The detailed cost model includes refurbishment cost, direct operations cost (such as system management, ore—launch ops., launch and mission control, propellants, recovery and transportation) as well as the indirect operations cost (launch site administration, support and facilities). Beside the vehicle system concept the vehicle size or payload capability has a major influence on transportation cost. FIG. 3 illustrates the interrelation between vehicle GEO payload capability, number of launches per year and total construction period for a 5 GW SPS. The cost impact both of vehicle size and launch rate is shown in FIG. 4. The specific cost are reduced with increasing annual launch rate, however, increasing vehicle size is more effective for cost reduction above some 50 launches per year. Larger vehicles require higher development investments but the difference can be amortized already after the launch of one SPS because the transportation may be reduced by a factor of two. The economics of large size vehicles again confirm a ballistic—type system providing a large payload volume. Larger pieces of the SPS reduce the orbital assembly effort and the related cost. However, even if the larger size means better economics, one certainly would not go straight to the final vehicle but an intermediate size in the 100 to 200 Mg GEO payload class, or 4 000 to 6 000 Mg launch mass (GLOW). This size of vehicle could also be used for nuclear waste disposal into space. The equatorial ESA launch site Kourou (French Guyana) would probably be a good option for an international launch site, both for SPS and nuclear waste transportation. Environmental restrictions at the Kennedy Space Center as well as the 8 — 10 % higher payload recommend this. Basically a policy decision is required for the next generation of launch vehicles whether the US will make a joint effort with Europe or go alone (may be in one direction and Europe in another).
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