Reliability and cost considerations for launch vehicle avionics

The optimum redundancy for an avionics processor can be determined from cost and reliability considerations. The use and expense of redundant architectures are examined, along with the cost and advantages of using space-qualified parts. The advanced launch system (ALS) vehicle model was used for the comparisons. Avionics redundancy models included duplex, triple modular redundancy, and quad systems. Processors were modeled as simplex, dual self-checking pairs, or triplex checking. Cost factors were those which result in the cost per launched vehicle. These included cost of launch equipment, cost of scrubbing a launch, failure investigation, repair, and the cost of money due to schedule delays. The primary conclusion reached was that the use of redundancy to achieve fault tolerance is required for higher value missions. The use of less-highly qualified parts can lower costs for less expensive payloads, but will require a culture change to allow launching with known faults. The need for greater emphasis on determination of coverage for fault-tolerant systems was demonstrated