Successful application of software reliability engineering for the NASA Space Shuttle

The Space Shuttle avionics software represents a successful integration of many of the computer industry's most advanced software engineering practices and approaches. Beginning in the late 1970s this software development and maintenance project has evolved one of the world's most mature software processes applying the principles of the highest levels of the Carnegie Mellon University Software Engineering Institute's Capability Maturity Model, Trusted Software Methodology, and ISO 9001 standards. This software process, considered to be a "best practice" by many software industry organizations includes state-of-the-practice software reliability engineering methodologies. Life-critical Shuttle avionics software produced by this process is recognized to be among the highest quality and highest reliability software in operation in the world. This case study explores the successful use of extremely detailed fault and failure history, throughout the software life cycle, in the application of software reliability engineering techniques to gain insight into the flight-worthiness of the software and to suggest "where to look" for remaining defects. The role of software reliability models and failure prediction techniques is examined and explained to allow the use of these approaches on other software projects. One of the most important aspects of such an approach, how to use and interpret the results of the application of such techniques, is addressed.