Distributed processing on the Space Shuttle - A case study

Abstract

A Power Extension Package (PEP) has been designed to provide additional electrical power and energy during Shuttle sortie missions. The considered investigation was conducted to determine the most suitable allocation of PEP monitoring and control functions between the Orbiter's existing (centralized) Systems Management General Purpose Computer and an embedded PEP processor. PEP monitoring and control functions are examined, and a configuration definition is considered, taking into account the 'functional migration' process, function allocation criteria, and candidate functional configurations. A trade study is conducted, giving attention to an assessment of four candidate configurations. Assessment factors are related to cost, development risk, aspects of reliability and safety, PEP design complexity, PEP/STS integration complexity, flight operations, and launch/landing site operations. A thorough (subjective) assessment of the PEP system life cycle indicates substantial benefits from a distributed processing approach.