Should The NASA-Air Force Cost Model?

There exist a number of commercially-available cost modeling tools to assist the NASA cost estimator develop realistic cost estimates. The NASA estimates are primarily based on NAFCOM (NASA-Air Force Cost Model).

NAFCOM is an automated parametric cost estimating tool that uses historical space data to predict the development and production costs of new space programs. It uses parametric relationships to estimate subsystem- and component-level costs for aerospace hardware, including Earth-orbiting spacecraft, piloted spacecraft, launch vehicles, upper stages, liquid rocket engines, scientific instruments, and planetary spacecraft. The model is used primarily in the early phases of a space project and estimates development and production costs at the subsystem and/or component level.
NAFCOM can estimate either by a product WBS or a labor, material, and overhead functional breakdown structure. Wizards assist the user in structuring a WBS appropriate for the system being estimated.
ESA has much less data on large manned space systems than NASA and therefore mainly used tools based on unmanned spacecraft data, adding cost multiplication factors to take into account the higher equipment and testing standards for human space flight.
The benefit of the data used by ESA is that it is very recent, incorporating the actual, current state of the technology and the market. Recent stepwise “jumps” in technology and costs over time can be identified, which are sometimes not captured by the gradual “year of technology” normalization factors used in NAFCOM. However, the setting of proper “human-rating factors” to be applied to satellite CERs and the stretching of the tools beyond their normal application (for instance, because equipment masses in human spacecraft tend to be much higher than for unmanned satellites and probes) poses some