ntrs.nasa.gov: Control techniques to improve Space Shuttle solid rocket booster separation - NASA Technical Reports Server (NTRS)

ntrs.nasa.gov: STAGE SEPARATION OF PARALLEL-STAGED SHUTTLE VEHICLES, A CAPABILITY ASSESSMENT M. J. Hurley, Design Specialist Flight Technology, Space Shuttle G. W. Carrie, Senior Design Engineer Vehicle Design & Structures, Space Shuttle Convair Aerospace Division of General Dynamics San Diego, California INTRODUCTION Stage separation has long been recognized as a major Space Shuttle problem area. The parallel-staged or “piggyback” arrangement precludes use of.separation techniques developed for tandem zhicle stages. Also, since most shuttle configurations are not symmetrical (thereby complicating interactions), experience gained from Titan IIIC solid motor separation is not directly applicable. Unlike present-day launch vehicle stage separation, the depleted Space Shuttle booster is as massive as the orbiter element and large intervehicular interaction is probable. Abort separation is likely to yield the most severe separation condition, since aerodynamic loading is significantly higher during the abort regime. Aerodynamics, including interference effects, will dominate the separation dynamics for all but the lowest dynamic pressures. Convair Aerospace has been conducting detailed analytical and experimental studies of multibody staging directly related to Space Shuttle for three years (Ref. 1 through 10). In support of these studies, one of the most comprehensive multibody separation simulations in existence today was developed on Independent Research and Development (IRAD) funds (Ref. 3). This simulation, in its various stages of development, was the analytic basis for the various analytical studies performed to date. This paper is essentially self-contained; it reviews the genesis of the forward link separation concept, evolves the stage separation system from its initial concept through detailed preliminary design, and presents major conclusions and results of supporting analyses. The paper contains all pertinent material generated as a consequence of the Space Shuttle Phase B study which was documented in June of 1971. In some areas, the approach differs from our Phase B baseline and reflects results from more current analyses; these differences are not always noted in the text that follows. STAGE SEPARATION CONCEPTUAL ANALYSIS This table presents 16 qualitative measures used to perform a preliminary evaluation of various separation system concepts so that a few of the better concepts might survive. The first three of these “measures” were in actuality merely categories used to label the various candidates. These categories were useful in ensuring that the candidates to be considered adequately span or exhaust the conceptual possibilities of systems that can perform the separation function. The remainder were measures intending to reject obviously poor candidates so that a select few may be looked at in detail in a subsequent design-oriented evaluation. A brief discussion of each should serve to illustrate its intent. By commonality (see table) we mean the degree to which the separation system does not duplicate the functions of other systems - e.g., the support and release (of these supports) functions of the interstage attachment system. Complexity is an obvious factor influencing design (nonrecurring) costs, qualification testing (nonrecurring) costs, maintenance (recurring) costs and even reliability. As such, complexity cannot be considered an independent measure, but its ease of determination makes it a valuable qualitative measure. Further, complexity has a direct bearing on the risk that such a conceptual approach might cost considerably more than expected to design and qualify or, worse, must eventually be scrapped in favor of an alternative approach. Dispersion sensitivity is meant to measure the degree to which the system concept can tolerate the inevitable variability of contributing factors; e.g., engine thrust rise and thrust decay uncertainties, aerodynamic load variations, variations in mass properties, sequence timing uncertainties, etc. It is a general consequence of constraints that systems properly employing constraints will be less dispersion sensitive (other things being equal), since the separation trajectory is restrained from entering an undesirable clearance-critical region. Reliability and safety are also not independent. Reliability is the certainty that the system will perform as designed when called upon to do so, including known variability (and its probability) in its operation. Safety is how safe the concept itself might be and embodies the consequence of potential (i.e., probable) failures in terms of the loss of life and equipment. Maintainability is the ease of maintenance of the system in operation and includes the system turnaround requirement. Nonrecurring costs are distinguished from recurring costs in that the former is a one-time cost (development, testing, and initial procurement) and the latter a cost per operation (per flight). Some separation concepts can be used only with “belly-to-belly,’ or “belly-to(booster’s) back” parallel arrangements (clusters) and imply operational restructions. All concepts investigated applied to parallel (as opposed to tandem) arrangements. The factors of separation system performance and ‘equivalent (booster) weight are estimates of the adequacy of the envisioned system in performing its intended function efficiently. The final category brings‘ out the degree to which the candidate concepts can be extended into the abort regime where the booster mass is substantially increased and aerodynamic loading becomes a major problem.