Comprehensive coverage of all aspects of space application oriented fault tolerance techniques • Experienced expert author working on fault tolerance for Chinese space program for almost three decades • Initiatively provides a systematic texts for the cutting-edge fault tolerance techniques in spacecraft control computer, with emphasis on practical engineering knowledge • Presents fundamental and advanced theories and technologies in a logical and easy-to-understand manner • Beneficial to readers inside and outside the area of space applications

Recent advances in micro-electronics and in computer architecture have led to renewed interest in fault-tolerant computers for spacecraft applications. The general field of fault-tolerant computers is surveyed, and concepts of static and dynamic redundancy, error detection by code or multiple processing, and the significance of low-level redundancy are explained. Prior efforts in the design of fault-tolerant computers for space applications are surveyed with processing capability, weight, and reliability estimates listed for a number of representative efforts. The SAMSO Fault-Tolerant Spaceborne Computer (FTSC) is the most current of these developments, and it is described in greater detail together with the proposed reliability test methodology for the prototype. Recent developments in reliability estimation, employment of microprocessors, and fault-tolerant software that are related to this field are briefly discussed. (Author).

Low availability, high cost, and poor performance of radiation hardened (rad-hard) equipment has driven the market to rely on commercial-off- the-shelf (COTS) equipment for the computing needs of today's spacecraft. This thesis describes the tailoring of a COTS embedded real-time operating system and design of a human-computer interface (HCI) for a triple modular redundant (TMR) fault-tolerant microprocessor for use in space-based applications. Once disadvantage of using COTS hardware components is their susceptibility to the radiation effects present in the space environment. and specifically, radiation- induced single-event upsets (SEUs). In the event of an SEU, a fault-tolerant system can mitigate the effects of the upset and continue to process from the last known correct system state. The TMR basic hardware design used for this research is an acceptable fault-tolerant design candidate for the main processor for space-based applications. We found that a COTS embedded real-time operating system could be tailored to support the TMR hardware. The HCI accepts serial data from the TMR, correctly identifies the source of the error, allows for processor mode selection and provides system- and board-level reset capabilities. The tailored operating system combined with the HCI is a viable software imp- lementation to support hardware-based fault-tolerant computing in a space environment.

Fault-tolerant computers have been developed for applications that require a very high degree of hardware reliability, and it is frequently asked whether similar techniques can be brought to bear on software for critical applications, e.g., ascent guidance software on launch vehicles, launch-control software for ground computers, and control and command software. The principal techniques employed in hardware fault tolerance are seen to be applicable also through software fault tolerance: error detection, protective redundancy, and rollback provisions. Of course, they need to be implemented in a specific manner; particularly the redundancy must be provided by a different code than that used for the primary modules. The recovery block (proposed by Randell), with the addition of a watchdog timer, has been implemented in a number of skeleton routines and has been found quite suitable in connection with the established structure for spaceborne software. A reliability model is proposed that shows a very considerable reduction in failure probability even when the fault-tolerance provisions themselves are far from perfect. It is therefore believed that the time is quite ripe to undertake serious studies of fault-tolerant software for space applications. (Author).