RBS OPERABILITY REQUIREMENTS AND TECHNOLOGY DEVELOPMENT IMPLICATIONS
The committee believes that achieving RBS booster ground turn-around operability is more of a design-requirements issue than a technology-development issue. The problem with many of the past reusable rocket vehicle designs (either single stage to orbit or an upper stage) is that they were so performance driven that even if operability requirements had been imposed, they could not have been effectively implemented without seriously compromising vehicle flight performance. Therefore, if operability requirements were imposed, they were assigned a low priority. This is certainly what happened during the space shuttle orbiter development (see Appendix E). The RBS booster, because its design is not nearly as performance driven, offers the opportunity for operability requirements to be imposed on at least an equal footing with performance requirements.
The specific operability recommendations contained earlier in this appendix were generated by NASA as a result of their orbiter experience. In addition to imposing a top-level operability requirement (e.g., the RBS booster shall be capable of re-flight in XX hours with a YY person ground crew), the NASA-generated recommendations listed previously could be tailored for RBS and specified by the Air Force as detailed operability requirements for the RBS booster. Also, they could be imposed as being equally important as the flight performance requirements.
From a technology development standpoint, IVHM and its associated sensors is clearly the tall pole for implementing operability, which is discussed in Section 3.1.8. Most of NASA’s recommendations are well understood design approaches that require little technology development. They are usually not “least weight” design options, which is why they have not been implemented in current expendables or performance-driven reusables. Many of the design approaches recommended are similar to, or fairly standard to, those used on commercial and military aircraft. Adapting these to the RBS booster will require redesign to accommodate the harsh vibration and acoustic environment imposed by rocket engines and then validation by extensive qualification testing. This redesign/qualification effort could be considered technology development, but it is not considered an especially high technical risk. However, the committee believes there is significant cost risk associated with attempting to qualify revised designs currently used on aircraft to the very harsh rocket launch environment.