TABLE 2.1 Reusable Booster System (RBS) Ground-Based Research and Development (R&D) Areas

RBS Ground R&D Element

 

Comment

Oxygen-rich, staged-combustion (ORSC), hydrocarbon engine

 

Enable U.S.-built, ORSC engine with acceptable performance, life, reliability, and cost. Augmented by long-term industrial efforts.

Return to launch site

 

Development/validation of models and hardware required for successful RBS flight phases. Wind tunnel tests as appropriate.

Autonomous guidance and control

 

Advance controls required for RBS flight phases.

Integrated vehicle health management

 

Integrated with adaptive guidance and control (AG&C) for flight phases and provides benefits for ground operations.

Ground operations

 

Includes experiments to validate efficient designs and operations, including subsystem maintenance, propellant management, and vehicle integration.

Advanced subsystems

 

Efforts on structures, power, thermal, and actuation subsystems tailored to RBS requirements.

2.5 RBS AND RECENT REUSABLE VEHICLES

There have been a number of recent programs for reusable launch vehicles (RLVs). The most relevant are the space shuttle, the National AeroSpace Plane (NASP, X-30), Lockheed Martin X-33, and Kistler K-1, and it is of interest to contrast these with the proposed RBS program. In addition, reusable options for the SpaceX Falcon 9 are under consideration. (Other organizations have initiated efforts on reusable concepts but have not built or tested a full-scale concept.) Table 2.2 lists some salient features of the RBS and the RLV programs.

The requirements and approaches for RBS differ in significant respects from those of prior RLVs, and some of the key differences can be seen in Table 2.2. All these RLVs were required to accommodate crew; which imposes demanding requirements on overall vehicle design that can significantly affect mission performance and cost. The upper stages of the RLVs were designed to be recoverable, which implies they must accommodate very stressing reentry environments. Relative to the RBS vehicle approach, this adds complexity and mass to the upper stages and, in practice, increases ground operation requirements and costs. The RBS is the only concept shown in Table 2.2 that proposes an expendable upper stage and a reusable first stage. That approach enables vehicle and mission options to reduce costs relative to traditional performance-optimized approaches. Other important differences include the single-stage-to-orbit approach of NASP and the X-33; the downrange recovery of the space shuttle; and key subsystems such as first-stage propulsion. It is noted that most of the RLV programs were initiated with requirements for elements that had not been demonstrated under flight-type conditions, much as is being proposed for the RBS program. This, in general, led to unanticipated costs. Overall, the differences between the RBS and RLV programs are such that comparisons between them are unlikely to be fully relevant or prudent. Further discussion of the space shuttle, NASP (X-30), and Venturestar (X-33) is contained in Appendix E.



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