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Advances in electronics over the past decade have produced major improvements in the power and flexibility of personal computer systems. Unfortunately current avionics systems for space applications typically have not leveraged these COTS advantages. Recently, there has been a trend toward utilization of commercial bus interconnects, primarily VME and PCI. These parallel interconnects have the disadvantage that a single failure can disable an entire string of the redundancy. Honeywell has developed a patent pending architecture for an avionics system that combines the high reliability of previous serial systems with the flexibility and openness of direct COTS bus interface. A decade ago, the state of the art for avionics systems made a step change from the PAVE PILLAR systems of the 1980's to the integrated modular avionics (IMA) used in the Boeing 777. This next generation avionics architecture is not based upon traditional Byzantine redundancy structures, but on a truth based scheme where each element knows when an internal failure occurs and removes itself from the system. IMA utilizes a lock step microprocessor design that communicates to a COTS backplane for input/output, and to a virtual backplane™ (a reliable, high-speed serial bus such as 1394 or AFDX) for intra-system communication. The system functions are implemented using an ARINC-653 time and space partitioned operating system. The entire system provides the simplicity of a simplex system, implements the highest level of reliability provides complete flexibility to reconfigure both software applications and hardware interfaces, allows for rapid prototyping using low-cost COTS hardware, and is easily expandable beyond the initial point implementation. As the only 5th generation avionics architecture, the concepts incorporated into Honeywell's IMA are ideally suited to be the backbone of the next generation Crew Exploration Vehicle for Project Constellation.