4.2.1.3 Results, Sensitivities, and Uncertainty Ranges

Sensitivities of vehicle cost to assumed design heritage and engineering management are shown in Figure 4.3. Clearly, DDT&E costs are significantly reduced as a result of the RBD effort, which results in a higher confidence in the RBS vehicle design as the program enters full-scale development. Potential variations in the RBS assumptions used for the NAFCOM inputs covering design heritage (design levels 1-8) and engineering management (management levels 1-5) appear to show a potential for RBS DDT&E estimates to increase by 50-100 percent, although the assumptions used for the baseline cost appear reasonable.

4.2.2 Engines

The engine estimates cover DDT&E and production. For the RBD, a NK-33 engine is used with Castor 30 and Star 63D solid motors in the second stage. The RBS uses five AJ-26 engines in the reusable first stage and an RS-25E engine for the expendable second stage. The reusable AJ-26 engines are assumed to be refurbished every 10 flights and replaced every 20 flights.

4.2.2.1 Models

The models and methodologies used to generate cost estimates for the engines are contractor-proprietary. These models are generally accurate when based on similar applications, although they rely on assumptions about reusability requirements, which carry some uncertainty.

image

FIGURE 4.3 Sensitivities to NASA/Air Force Cost Model inputs normalized to the baseline RBS design, DDT&E program. Sensitivity of cost to the design maturity (e.g., whether or not requalification of an existing design, Requal, is needed) and Engineering Management Level needed for program execution. NOTE: DDT&E, development, test, and evaluation; RBD, reusable booster demonstrator; RBS, reusable booster system. SOURCE: Air Force Space and Missile Systems Center, SMC Developmental Planning, “Reusable Booster System Costing,” presentation to the committee, February 15, 2012. Approved for Public Release.



The National Academies of Sciences, Engineering, and Medicine
500 Fifth St. N.W. | Washington, D.C. 20001

Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement