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The Orion Crew Exploration Vehicle has requirements for automation and autonomy that exceed the capabilities of the Space Shuttle and International Space Station. The Orion requirements call for automated rendezvous and docking, automated ascent aborts, and automated deorbit burns among other requirements, which result in a spacecraft with a higher level of autonomy from ground-based support. While increased levels of automated functionality provide autonomy necessary for extended duration missions, it also imposes additional requirements to ensure the capability to monitor and control the automated capabilities. This paper presents the GN&C Architecture developed to satisfy these requirements and safely provide the desired increase in spacecraft automation. The joint NASA and Lockheed Martin GN&C team with support from Draper Laboratory is designing the GN&C Architecture described in this paper. The design will provide the interface to the Orion “Timeline Manager” software, which contains the knowledge of the overall mission plan. This mission plan is broken into Mission Segments which represent the low-level decomposition of the mission timeline, e.g., burn maneuvers and other critical events. The GN&C Architecture is designed with a hierarchical structure to sequence through the GN&C Activities necessary to complete the objectives of the current Mission Segment. Each GN&C Activity will be used to configure the individual Guidance, Navigation, and Control Modes. To satisfy control of automation and flexibility requirements the GN&C Architecture must also provide an interface that allows crew and ground operators to access critical GN&C functionality during automation operations and manually configure the GN&C Subsystem when necessary. This flexibility is intended to prevent the development of a „brittle‟ architecture that cannot accommodate the dynamic and unpredictable nature of human space flight. This paper outlines the preliminary Orion GN&C Architecture and describes a functional prototype of the GN&C Architecture created using object oriented design philosophies in the Matlab/Simulink environment. A unique design and code generation process employing Unified Modeling Language (UML) modeling practices was used to capture the design, ensure requirement traceability and generate working prototype Matlab and C-code. |
