2218. Non-Weight Based Cost Modeling


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C J Meisl: 2218. Non-Weight Based Cost Modeling. 1994.



This paper discusses the advantages of non-weight based cost models and uses launch vehicle rocket engine cost modeling as an example. Top level parametric cost models were generated for pump-fed liquid bipropellant booster and upper stage rocket engines in the 20 Klbs to 2000 Klbs thrust class. The models cover production and full scale development costs and are based on thorough engineering analysis, not regression analysis, using data from historical rocket engines, potential engine derivatives and proposed new engine concepts. The models depend on thermodynamic cycle, propellant type, thrust level, engine complexity, engine maturity and other design parameters. The models are simple cost estimating relationships (CERs) with a transparent rationale and an accuracy of 10 to 30%, depending on the engineering expertise used in the generation of the input variables. The format of the models and the rationale behind them are given in this paper. The cost models make use of adjective and objective parameters. For the adjective inputs, metric scales are given to convert them into numerical values. The adjective inputs require good engineering understanding of rocket engine design and manufacturing principles. Several programmatic and manufacturing process improvement factors are incorporated to extend the applicability of the historical data based cost models to new reusable or expendable advanced performance and/or to low cost engine concepts. The validity and reasonableness of the cost models were successfully checked against detailed cost data of the Space Transportation Main Engine (STME) and against current manufacturing and programmatic analysis results of new engines. A comparative (non-quantitative) evaluation of these new rocket engine cost models with existing weight based models such as TRANSCOST, PRICE-H predictions and a Tecolote Research Inc. originated model is also contained in the paper.


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