3246. Predicted Production Costs for Advanced Aerospace Vehicles


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Han P. Bao: 3246. Predicted Production Costs for Advanced Aerospace Vehicles. 2002.



For early design concepts, the conventional approach to cost would be some kind of parametric weight-based cost model. There is now ample evidence that this approach can be misleading and inaccurate. By the nature of its development, a parametric cost model requires historical data and is valid only if the new design is analogous to those based upon which the model was derived. Advanced aerospace vehicles have no historical production data and are nowhere near the vehicles of the past. Using an existing weight-based cost model would only lead to errors and distortions of the true production cost.
This paper outlines the development of a process-based cost model in which the physical elements of the vehicle are costed according to a first-order dynamics model. This theoretical cost model, first advocated by early work at MIT, has been expanded to cover the basic structures of an advanced aerospace vehicle. Elemental costs based on the geometry of the design can be summed up to provide an overall estimation of the total production cost for a design configuration. This capability to directly link any design configuration to realistic cost estimation is a key requirement for high payoff MDO problems.
Another important consideration in this paper is the handling of part or product complexity. Here the concept of cost modulus is introduced to take into account variability due to different materials, sizes, shapes, precision of fabrication and equipment requirements. A case study based on the preliminary analysis of the shape of a vehicle is presented to illustrate the approach for estimating its production cost. It is shown that changing the baseline ratio between pressurized area and non-pressurized area by as little as .5% would incur a cost variance of roughly 5% in cost (no linear relationship is implied) while using a weight-based cost model would result in no cost change because the overall weight of the vehicle remains practically the same. Ultimately the most important implication of the development of the proposed process-based cost model is that different design configurations can now be quickly related to their cost estimates in a seamless calculation process easily implemented on any spreadsheet tool.


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