Following consideration of all materials presented in the previous chapters, the committee arrives at the following six principal findings regarding the reusable booster system (RBS) concept.
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 little relevant experience exists concerning reusable systems, there are large uncertainties associated with implementation of the vehicle features necessary to ensure needed operability.
Second, the cost projections are based on the “Americanization” of Russian hydrocarbon engine technology, but cost risks associated with development of operable engine development are difficult to capture. Given the limited experience base of U.S. industry developing oxygen-rich, staged-combustion (ORSC) hydrocarbon engines, the cost uncertainties associated with the engine development may be significant.
Third, the details underlying the required infrastructure needs are unclear, so uncertainties exist in the costs associated with the required infrastructure.
Finally, the estimated operational costs assumed modest postflight inspection requirements, which assume successful development of an effective Integrated Vehicle Health Management system and little added costs associated with 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 therefore 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 Evolved Expendable Launch Vehicle (EELV) costs. Given the significant number of commercial entities pursuing novel approaches towards achieving launch capabilities, the future of space lift may look very different from that 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.
Second, the RBS business case does not address the impacts of single source providers. So, while the business case assumes that RBS captures the complete Air Force launch manifest and is developed with a single source provider, the cost risks associated with using a single source are not adequately addressed. Said another way, the cost benefits associated with retaining competition in vehicle development were not included in the business case. Since the commercial launch market is rapidly changing and will be driven by cost considerations, neglecting an assessment of the role of competition is viewed as a weakness in the current RBS business case.
Third, the RBS business case assumed full capture of the Air Force launch manifest, but the Air Force maintains a requirement for independent launch capabilities for mission assurance needs. With this need for development and/or maintenance of a second launch system capability, the RBS business case model is overly optimistic in its assumption regarding full capture of the Air Force launch manifest.
The end result of these factors is that the uncertainties associated with the RBS business case are sufficiently large that the business case cannot be considered to be closed at the present time.
Finding 3: Reusability remains an option for achieving significant new full-spectrum launch capabilities at lower cost and greater launch flexibility.
The Air Force Space Command has identified a long-term science and technology objective for achieving full-spectrum launch capabilities at significantly reduced costs, and reusability remains a potential option for realizing this objective. In concert with reduced costs, development of a robust reusable system might have additional benefits that may be realized, including replenishment of satellites on need; deployment of distributed constellations; rapid deployment of capabilities; robust launch operations from multiple, defendable launch sites; and operations by Air Force personnel.
Finding 4: For RBS to significantly impact Air Force launch operations, it would have to be more responsive than current expendable launch systems. However, no requirement for RBS responsiveness has been identified that would drive technology development.
The current business case for RBS is built on satisfying the current EELV launch manifest with a launch-on-schedule assumption to operations. With this assumption and the lack of an operability requirement for RBS, the technologies necessary to significantly enhance operability and reduce operations costs will not be emphasized. It is through development of design features and technologies, and the resulting changes to Air Force operations that the true value of a reusable system lays.
Finding 5: Technology areas have been identified in which continued applied research and advanced development are required before proceeding to large-scale development. These areas include reusable ORSC hydrocarbon-fueled engines, rocketback return-to-launch-site (RTLS) operation, vehicle health management systems, and adaptive guidance and control capabilities.
Finding 6: Given the uncertainties in the business case and the yet-to-be mitigated technology risks, it is premature for Air Force Space Command to program significant investments associated with the development of a RBS capability.
While the committee found that the RBS business case cannot be closed at this time, and it is premature to begin large-scale RBS development activities, the committee does strongly endorse the continued research and
advanced technology development needed for future launch systems. The committee makes the following six recommendations.
Recommendation 1: Launch responsiveness should be a major attribute of any reusable launch system. To address this perceived disconnect, the Air Force should establish specific responsiveness objectives independent of the Evolved Expendable Launch Vehicle launch-on-schedule requirements that can be used to drive technology development.
The committee believes that responsiveness considerations should be a major consideration when addressing reusable launch systems and their supporting technologies. At the present time, responsiveness requirements beyond a launch-on-schedule philosophy have not been defined. Since these responsiveness requirements can drive vehicle and technology needs, it is important for the Air Force to define nominal responsiveness goals to provide focus for research and development activities.
Recommendation 2: Independent of any decision to proceed with RBS development, the Air Force should proceed with technology development in the following key areas: reusable oxygen-rich staged-combustion hydrocarbon-fueled engines; rocketback return-to-launch-site operations; vehicle health management systems; and adaptive guidance and control systems. These technologies will have to be matured before they can support any future decision on RBS, and most of them will be also applicable to alternative launch system concepts.
Continued development is needed in these four principal areas to sufficiently mature these technologies to the point where significant investments can be committed to the RBS programs. The committee recommends that investments in these four areas continue independent of a decision to proceed with RBS development at this time. Since these technologies have application beyond RBS, with the exception of rocketback RTLS, this technology maturation will benefit the Air Force independent of RBS in areas of advanced rocket propulsion, system reliability, and vehicle autonomy.
Recommendation 3: The Air Force Research Laboratory’s (AFRL’s) Pathfinder project is under way to demonstrate in flight, using a small-scale vehicle, the critical aspects of the return-to-launch-site maneuver. To increase chances for Pathfinder’s success, AFRL should develop and fly more than one Pathfinder test vehicle design. In addition, competition among RBS concepts should be maintained as long as possible to obtain the best system for the next generation of space launch.
The use of a rocketback maneuver for RTLS operations of an RBS has not been previously demonstrated, so this approach to reusability carries significant risk. Given these risks and the resulting parameter space for innovative solutions, the Pathfinder program should be executed in a manner wherein several vehicle designs are developed and flown. While this approach will increase costs in the near-term, the long-term benefits to achieving a true high-performance solution will overwhelm this initial cost, if reusability is pursued in the future.
Recommendation 4: The decision to proceed with the RBS development program should be based on the successful completion of the Pathfinder activities and on assurance that the technical risks associated with the reusable oxygen-rich, staged-combustion hydrocarbon-fueled engines, rocketback return-to-launch-site vehicle health management systems, and adaptive guidance and control systems are adequately mitigated.
Given the immaturity of principal technologies and the inherent risks of the rocketback RTLS operation, the committee recommends that the decision to proceed with RBS development be tied to the successful completion of the Pathfinder program and suitable mitigation of the principal technical risks. The committee understands that this approach delays potential achievement of an RBS capability. Delaying the decision to proceed with the RBS
development has the additional benefit of enabling the business environment regarding emerging new entrant commercial launch providers to become clearer.
Recommendation 5: Following successful completion of the Pathfinder program, the Air Force should reevaluate the RBS business case, accounting for the following factors: new-entrant commercial launch providers; potential impacts of single-source providers; and Air Force need for independent launchers to satisfy assured-access-to-space requirements.
Upon the successful completion of the Pathfinder program and the associated development of the four principal technologies, the Air Force should reevaluate the business case for RBS to determine if it can be closed at that point. This business case analysis should include the impacts of new-entrant commercial launch providers, single-source providers, and the Air Force need for independent launchers.
Recommendation 6: When constructing the RBS program, the decision points for proceeding from technology development to demonstration to prototype to production for RBS should be based on quantitative assessments during the successful completion of the previous phase. These go/no-go decision points should be structured as on-ramps to subsequent phases with technical underpinnings that are sufficiently well understood to proceed. The decision points for proceeding from Pathfinder and hydrocarbon boost technology risk reduction to a mid-scale demonstrator and from the demonstrator to Y-vehicle prototypes should be considered as on-ramps.
Given the costs associated with the development of a new space launch capability and the technical uncertainties associated with its operational approach, it is prudent to construct any potential future RBS program in a manner wherein the decision to proceed to any next phase is strongly tied to the successful completion of the previous phase.
Today, the United States finds itself in the midst of a potentially fundamental transition of space launch from a model wherein the government develops and controls the launch vehicles to a service-based model wherein industry develops launch vehicles and then sells services to both commercial and governmental organizations. Within the uncertainties of this transition, the committee is aware of a large number of organizations that are developing capabilities using innovative designs, development, and operational approaches. The review and evaluation of the RBS concept within this transition is fundamentally difficult, but the committee firmly believes that the future of U.S. space launch will be strong, given the technology developments recommended in this study coupled with innovative designs and approaches for more cost effective and robust launch systems.