1998 - Draper Laboratory

well as reversing the whole process. Rapid recovery from singleeventupsets occurring in quick succession in a high-radiationenvironment should also be part of a technical demonstrationplan.Beyond the demonstration and validation of key architecturalcharacteristics and implementation parameters, it is alsonecessary to start defining the various phases of the mannedMars mission, specifically, their computational performance andreliability requirements. A mission-specific fault-tolerantcomputer can then be configured on which to demonstrate theaforementioned characteristics.An aggressive technical demonstration plan can be executed overa period of about 2 years.Summary and ConclusionsManned missions to Mars are going to be extremely demandingfrom the viewpoint of the onboard information processingsystems. Such systems would need to be operational for longdurations and meet the safety criteria of manned spacecraft.A fault-tolerant computing approach that uses parallel-hybridredundancy, implemented in an open system architecture, hasbeen proposed to meet the stringent mission requirements.Many of the key architectural attributes such as real-time errormasking, dynamic reconfiguration between high-throughput andhigh-reliability configurations, use of COTS hardware andsoftware, and low fault-tolerance overheads have beendemonstrated via three generations of increasingly matureimplementations.AcknowledgmentContributions to this paper by Robert L. Shuler of NASA JohnsonSpace Center are gratefully acknowledged.References[1] Harper, R.E. and J.H. Lala, “Fault-Tolerant Parallel Processor,”AIAA Journal of Guidance, Control, and Dynamics, Vol. 14,No. 3, May-June 1991.[2] Lala, J.H., “Fault Detection, Isolation, and Reconfiguration inFTMP: Methods and Experimental Results,” 5th DigitalAvionics Systems Conference, Seattle, WA, November 1983.[3] Lala J.H., R.E. Harper, and L.S. Alger, “A Design Approach forUltrareliable Real Time,” Special Issue of IEEE ComputerMagazine on Real-Time Systems, Vol. 24, No. 5, May 1991.[4] Lala, J.H. and R.E. Harper, “Architectural Principles forSafety-Critical Real-Time Applications,” The Proceedings ofthe IEEE: Special Issue on Real-Time Systems, January 1994.[5] Harper R.E., “Critical Issues in Ultrareliable ParallelProcessing,” PhD Thesis, Massachusetts Institute ofTechnology, Cambridge, MA, 1987.[6] Hopkins A.L., Jr., J.H. Lala, and T.B. Smith III, “The Evolutionof Fault-Tolerant Computing, 1955-85,” DependableComputing and Fault-Tolerant Systems, Vol. I: The Evolutionof Fault-Tolerant Computing, Springer-Verlag, Wien, Austria,1987, pp. 121-140.[7] Hanaway, J.F. and R.W. Moorehead, “Space Shuttle AvionicsSystem,” NASA SP-504, Superintendent of Documents, U.S.Govt. Printing Office, Washington, DC 20402, 1989.[8] Lala J.H. et al., “Advanced Information Processing System(AIPS)-Based Fault-Tolerant Avionics Architecture for LaunchVehicles,” Proc. Ninth AIAA/IEEE Digital Avionics SystemsConf., IEEE Press, Piscataway, NJ, 1990, pp. 125-132.Advanced Fault-Tolerant Computing for Future Manned Space Missions8