For unprotected payloads (not in fuselage), usually the case for the first stage, the last term in (2B) is zero. The inert weight fractions, 8r, 8L, 8P and e, are determined from statistical analysis of past designs as discussed in the text. Solution of (IB) and (2B) for the value of k0, the payload weight divided by the GLOW, requires an iterative procedure since e is a function of WF. Note that the stage payload for the first stage is the second stage, W2. The stage payload for the second stage is the final payload in orbit, where the payload ratio Ko of the final payload to the GLOW is In order to determine Wr it is necessary to know the distribution of energy required to achieve orbit between the stages. A first estimate for the distribution of AV between stages may be obtained by linearizing the problem and cnsidering the following simple case. We have for each stage of an n stage vehicle or the most efficient (lowest inert weight) stage should have the highest AV. Since, however, the inert weight fraction is dependent on, among other factors, the stage AV, a heuristic approach to the problem is required for the second iteration. This was done for one case (Fig. 2). It was evident that, within the limits set by (5B), the distribution of AV between stages was not a highly sensitive parameter. A value indicated by Fig. 2 was therefore taken for all cases studied. APPENDIX C. LOGISTICS COSTING Assessing the costs of logistics support for a program such as the SPS ranks among the most complex problems of systems analysis. With the available combinations of transport methods, production tooling, crew habitat designs, equipment procurements, and numerous other parameters, the SPS production scenario under consideration is difficult to completely specify, much less analyze. There is obviously a tradeoff in the systems analysis: whether to model the system with more parameters, generally producing higher accuracy, or fewer, resulting in quicker model verification and more manageable algorithms. The approach detailed here attempts to compromise between these two extremes. It is assumed that the entire process of space industrialization can be broken down into four major
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