Best Practices for Reliable and Robust Spacecraft Structures

,A study was undertaken to capture the best practices for the development of reliable and robust spacecraft structures for NASA’s next generation cargo and crewed launch vehicles. In this study, the NASA heritage programs such as Mercury, Gemini, Apollo, and the Space Shuttle program were examined. A series of lessons learned during the NASA and DoD heritage programs are captured. The processes that “make the right structural system” are examined along with the processes to “make the structural system right”. The impact of technology advancements in materials and analysis and testing methods on reliability and robustness of spacecraft structures is studied. The best practices and lessons learned are extracted from these studies. Since the first human space flight, the best practices for reliable and robust spacecraft structures appear to be well established, understood, and articulated by each generation of designers and engineers. However, these best practices apparently have not always been followed. When the best practices are ignored or short cuts are taken, risks accumulate, and reliability suffers. Thus program managers need to be vigilant of circumstances and situations that tend to violate best practices. Adherence to the best practices may help develop spacecraft systems with high reliability and robustness against certain anomalies and unforeseen events. I. Introduction ASA is currently in the process of developing the next generation crewed and cargo launch vehicles and spacecraft to return to the moon and beyond. With the experience and knowledge base available from past similar programs, a document that captures salient aspects of successful programs is being developed. This document serves as an important guide in evaluating next generation and future spacecraft concepts and proposals. As a part of this guide, guides for individual technical disciplines are being developed. Reliable and robust structural systems design is one of these technical disciplines. The structures document describes pertinent issues, best practices, errors, miss-steps, lessons learned, and summarizes the previously used design processes (tools and standards) for the structures discipline. Structural systems provide the basic framework to distribute external and internal loads resulting from all flight loads, ground loads, and associated operational and environmental loads. The primary objective of a structural system is to remain intact and experience minimal deformation when exposed to various environments, including ground processing, testing, launch, on-orbit, and re-entry operations. Structural systems also provide containment for pressures as in pressure vessels, pressure components, and pressurized structures. Structures tend to be a dependent subsystem in the sense that many requirements flow to structures from other subsystems. Space systems are very complex products of multiple disciplines, and therefore require a multidisciplinary analysis and optimization approach to capture various system interactions and sensitivities in order to obtain optimum system