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Appendix E COST TRADE-OFFS Reliable cost ligures are difficult to come by at this time. Shuttle redesign, replacement, and operations costs are in flux. Titan IV, MLV, and Titan II costs either are being renegotiated or are competition-sensitive. The best that can be done is to use existing NASA and Air Force cost data bases and should-cost models to determine the likely cost drivers. While by no means accurate enough for budget purposes, their use in the past has proven useful in determining first-order trade-offs, i.e., more refined subsequent calculations seldom overturn the general results. The calculations were performed by the Aerospace Corporation. Figures E-l and E-2 indicate the total launch costs of various mixes (see Table E-l) of shuttles (STS), Titan IVs, medium-launch vehicles (MLVs) and Titan Us corresponding respectively to 24 and l6 equivalent shuttle flight loads per year depending upon the annual depreciation assumed for the shuttle fleet. Depreciation includes the cost of replacements Orbiters regardless of cause. Comparing the 2 figures, the total costs clearly depend upon the total flight load; it costs more to launch 24 than to launch l6 shuttle-equivalent flight loads per year, though the increase is not proportional. Taking either figure, it doesn't make much difference what mix is chosen, though at more than a one percent depreciation it costs less to have fewer rather than more shuttles in the mix. Such differences as occur may well be within the estimating accuracy. The calculations assume that each mix is stable, i.e., changes from one mix to another could generate added costs unless the changes were well planned in advance. In any case, a commonly held assumption that ELV costs are simply an add-on to the (fixed) costs of the shuttle program is not substantiated by the available data bases and cost models when all costs are considered. What is more important to total cost, again taking either figure, is the depreciation rate for the shuttle fleet. Based on the logistics considerations discussed in Appendix C, the depreciation rate one might expect is in the range of l-2 percent. The clear cost trade-off here is between higher (and earlier) reliability improvement costs and higher (and later) depreciation costs. Safety will drive to the former; near-term funding and schedule pressure could drive to the latter. 43
44 4.4 r- 4.2 » 4.C O CO z O 5 24 Equivalent STS Flts/Yr 3.8 3.6 3.4 8,11,2,12 ± 4% 1% 0% Depreciation 10, 10, 2, 9 STS, T-4, T-2, MLV Figure E-l Total Cost TrendsâMixed Fleet Options Studied (Case I) 12, 9, 2, 6
45 3.8 3.6 3.4 3.2 3. 2.8 16 Equivalent STS Flts/Yr 6, 6, 2, 9 9, 4, 2, 6 STS, T-4, T-2, MLV 0% Depreciation I 12, 2, 2, 3 Figure E-2 Total Cost TrendsâMixed Fleet Options Studied (Case II)
46 TABLE I NATIONAL DEMAND MODEL POST FY-9l CASE I: TOTAL DEMAND OF 24 EQUIVALENT STS FLIGHTS STS 8 l0 l2 TIV ll 10 9 Til 2 2 2 MLV l2 9 b CASE II: TOTAL DEMAND OF l6 EQUIVALENT bTS FLIGHTS STS 6 9 l2 TIV b 4 2 Til 9 62 MLV 633 CASE I is a discounted version of the national demand presented by NASA Headquarters (J. Fitts). CASE II is a much more conservative version of the national demand.
