Start Date
4-1971 8:00 AM
Description
This paper describes an analysis of the level of redundancy of line repaceable units (LRUs) required for the Space Shuttle avionics system. The required number of LRUs is neither based on an arbitrary numerical probability nor on an aribtrary number of replicative units. Instead, a total cost to the program of each added LRU is calculated and the configuration that results in lowest program cost is selected.
The analysis includes the costs of developing and procuring hardware, and the annual maintenance expense. Cost penalties for weight and electric power consumption are imposed for each added LRU. Improvement in reliability is quantified in terms of the reduced costs due to fewer lost vehicles and fewer missions where the payload cannot be delivered. Realistic mission rules are used for determining when the payload cannot be safely delivered. The analysis allows a choice of high-reliability or low-reliability procurement policies for each LRU.
The results show that triply redundant Booster equipment and triply-redundant Orbiter equipment, are most cost effective, except for one additional inertial platform and central computer in the Orbiter.
The Determination of Avionics Redundancy for Minimum Cost
This paper describes an analysis of the level of redundancy of line repaceable units (LRUs) required for the Space Shuttle avionics system. The required number of LRUs is neither based on an arbitrary numerical probability nor on an aribtrary number of replicative units. Instead, a total cost to the program of each added LRU is calculated and the configuration that results in lowest program cost is selected.
The analysis includes the costs of developing and procuring hardware, and the annual maintenance expense. Cost penalties for weight and electric power consumption are imposed for each added LRU. Improvement in reliability is quantified in terms of the reduced costs due to fewer lost vehicles and fewer missions where the payload cannot be delivered. Realistic mission rules are used for determining when the payload cannot be safely delivered. The analysis allows a choice of high-reliability or low-reliability procurement policies for each LRU.
The results show that triply redundant Booster equipment and triply-redundant Orbiter equipment, are most cost effective, except for one additional inertial platform and central computer in the Orbiter.
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