of the projected cost for this RBS baseline concept that predicted significant life-cycle savings compared to the EELV system satisfying the same launch manifest. This cost study used industry standard models for estimating the cost of the RBS launch stages, independent cost estimates of the required propulsion systems and ground infrastructure, and model-based estimates of the operational costs.

The Air Force Space Command asked the Aeronautics and Space Engineering Board of the National Research Council to conduct an independent review and assessment of the RBS concept prior to considering a continuation of RBS-related activities within the Air Force Research Laboratory portfolio and before initiating a more extensive RBS development program. The Committee for the Reusable Booster System: Review and Assessment was formed in response to that request and charged with reviewing and assessing the criteria and assumptions used in the current RBS plans, the cost model methodologies used to frame the RBS business case, and the technical maturity and development plans of key elements critical to RBS implementation. The committee consisted of experts not connected with current RBS activities who have significant expertise in launch vehicle design and operation, research and technology development and implementation, space system operations, and cost analysis. This committee solicited and received input on the Air Force launch requirements, the baseline RBS concept, cost models and assessment, and technology readiness. The committee also received input from industry associated with the RBS concept, industry independent of the RBS concept, and propulsion system providers.

Based on the input received, its own analysis, and judgment based on committee expertise, the committee came to six major findings.

Finding 1: Cost estimate uncertainties may significantly affect estimated RBS life-cycle costs.

There are several important factors that lead to significant uncertainties associated with the RBS cost estimates developed to date. First, the vehicle development costs were estimated using NASA/Air Force Cost Model (NAFCOM), which is an industry standard model, and reasonable model inputs were used, but operability impacts on vehicle design are not captured using this model. Since NAFCOM is largely based on historical data and lacks relevant experience on reusable systems, there are large uncertainties associated with implementing the vehicle features necessary to ensure operability.

Second, the cost projections are based on the “Americanization” of Russian hydrocarbon engine technology, but cost risks associated with development of an operable engine are difficult to capture. Given the limited experience of U.S. industry in developing oxygen-rich, staged combustion (ORSC) hydrocarbon engines, the cost uncertainties associated with the engine development may be significant.

Third, the details underlying the infrastructure needs are unclear, so uncertainties exist in the costs associated with the infrastructure.

Finally, the estimated operational costs assumed modest postflight inspection requirements, which assume successful development of an effective integrated vehicle health management (IVHM) system and little added cost for the mission assurance requirement.

Finding 2: The RBS business case is incomplete because it does not adequately account for new entrant commercial providers of launch capabilities, the impacts of single-source providers, Air Force need for independent launch sources for meeting their assured-access-to-space requirement, and technical risk. The cost uncertainties associated with these factors do not allow a business case for RBS to be closed at the present time.

In addition to the basic cost uncertainties associated with the RBS, three additional factors exist such that an assessment that the RBS business case is not complete and cannot be closed at the present time. First, the RBS business case does not account for new-entrant commercial providers, in that the business case is based on a comparison of the RBS concept to an extrapolation of recent EELV costs. Given the significant number of commercial entities pursuing novel approaches to achieve launch capabilities, the future of space lift may look very different from those employed today. With global competition to reduce launch costs, it is anticipated that recent EELV costs may not be the proper baseline for cost comparisons.

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