Verifying shuttle onboard software using expert systems

The Space Shuttle uses a complex set of software to guide, navigate, and control it through all phases of flight. Adding to the complexity is the fact that the software is reconfigured for each flight, i.e., thousands of constants in the software are changed to reflect the unique properties of a given mission. In the last level of tests, the software is flown through end to end nominal and abort scenarios taking the shuttle from liftoff to landing. The analysis of the results of the testing is experience and labor intensive. A set of pass/fail criteria were defined for each test case and in parallel with the knowledge acquisition, tools were developed which allowed the automation of the knowledge being gathered on paper. A prototype of the Analysis Criteria Expert System (ACES) was put into production in the verification of the reconfigured onboard flight software

Paper Session III-A - Space Shuttle Avionics Upgrade: Issues and Opportunities

The Space Shuttle uses a complex set of software and hardware to guide, navigate and control it through all phases of flight. Five IBM AP-101B flight computers host a set of highly critical and complex programs. The current man-machine interface consists of a series of dedicated electromechanical instruments and switches combined with specialized displays with limited function. The exponential growth of microprocessor technology combined with the approaching obsolescence of the Space Shuttle cockpit avionics have driven NASA to explore a Product Improvement Plan for the Space Shuttle which includes the cockpit displays and controls. The IBM Systems Integration Division (SID) in Houston is currently studying alternatives for upgrading the Shuttle\u27s cockpit. Some goals of the upgrade include: Offloading of the main computers by distributing some of the avionics display functions, reducing crew workload, reducing maintenance cost, and providing display reconfigurability and context sensitivity. These goals are being met by using a combination of offthe- shelf and newly-developed software and hardware. The software will be developed using Ada, and must meet the timing constraints imposed by existing Shuttle Systems. Advanced active matrix liquid crystal displays are being used to meet the tight space, weight and power consumption requirements. These displays are tied to commercially available 80386 microprocessors. On top of the challenges presented by the software and hardware development are programmatic constraints. These include: Transparency to existing Shuttle avionics and data processing systems, Integration into training facilities: avionics labs, simulators, aircraft, etc., Development of ground support systems: Software Development facilities, verification capabilities, systems integration environments, etc. and Installation into the operational Shuttle fleet without impacting current flight rates. Of course, this all has to be done within cost and timing constraints in a dynamic environment. This upgrade holds promise for future improvements to the onboard avionics systems. An example is online storage and display of crew checklists and procedures. This and other potential growth paths must be accounted for in the design of this upgrade. The opportunities for laying the groundwork of a cohesive strategy for avionics in the nation\u27s space fleet are many and the issues are complex but the technology has advanced far enough that significant benefits can be achieved by upgrading the current system making this a worthwhile if not mandatory task