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Meeting	ACGS Committee Meeting 117 - Napa, CA - March 2016
Agenda Location	9 SUBCOMMITTEE A – AERONAUTIC AND SURFACE VEHICLES 9.4 A Short History of the Space Shuttle Orbit Flight Control System Development and Application Evolution
Title	A Short History of the Space Shuttle Orbit Flight Control System Development and Application Evolution
Presenter	Philip Hattis
Affiliation	Draper
Available Downloads*	presentation
	Downloads are available to members who are logged in and either Active* or attended this meeting.
Abstract	The Space Shuttle Orbit Flight Control System (OFCS) provided all Guidance, Navigation, and Control (GN&C) capabilities from external tank separation during ascent until entry interface during return. Its development began in earnest in 1975 with first orbital flight application in 1981. While the Shuttle OFCS design benefitted from some Apollo program heritage, the many operational requirements for the Shuttle and unique vehicle design characteristics demanded specialized algorithmic adaptations and numerous new functional features. Among the primary challenge areas for the Shuttle OFCS design were capacity and speed limitations of the General Purpose Computers (GPC) as well as the fault-tolerant processing architecture. Many special GN&C design features and compromises were needed to overcome these limitations. There were a number of integrated system dynamics surprises that arose in the initial few Space Shuttle orbital missions. These motivated modifications to the OFCS to assure adequate safety margins on subsequent flights, to conserve mission propellant, and to sustain the useful lives of subsystems needed by the reusable orbiters. The complexity and sophistication of the Shuttle on-orbit operations evolved greatly over its three decades of missions. Deployment of large payloads using compliant release mechanisms and an agile, but flexible robotic arm introduced classes of vehicle attitude disturbances that posed system stability challenges. Much work was done to fully evaluate and extend the OFCS control envelope to accommodate these evolving operational capabilities. This Paper provides a short history of the Shuttle OFCS development and orbital application evolution addressing the topics noted above.