Mathematics – Logic
Scientific paper
Jan 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002iaf..confe.901c&link_type=abstract
IAF abstracts, 34th COSPAR Scientific Assembly, The Second World Space Congress, held 10-19 October, 2002 in Houston, TX, USA.,
Mathematics
Logic
Scientific paper
After decades of Solar System exploration, NASA has almost completed the initial reconnaissance, and has been planning for landing and sample return missions on many planets, satellites, comets, and asteroids. The next logical step of space exploration is to expand the frontier into other missions within and outside the solar system. These missions can easily last for more than 30 to 50 years. Most of the current technologies and spacecraft design techniques are not adequate to support such long life missions. Many breakthrough technologies and non-conventional system architecture have to develop in order to sustain such long life missions.Some of these technologies are being developed by the NASA Exploration Team (neXt). Based on the projected requirements for ultra long life missions, the costs and benefits of the required technologies can be quantified. The ultra long-life space system should have four attributes: long-term survivability, administration of consumable resources, evolvability and adaptability, and low-cost long-term operations of the spacecraft. The discussion of survivability is the focus of this paper. Conventional fault tolerant system design has to tolerate only random failures, which can be handled effectively by dual or triple redundancy for a relatively short time. In contrast, the predominant failure mode in an ultra long-life system is the wear-out of components. All active components in the system are destined to fail before the end of the mission. Therefore, an ultra long-life system would require a large number of redundant components. This would be impractical in conventional fault tolerant systems because their fault tolerance techniques are very inefficient. For instance, a conventional dual-string avionics system duplicates the all the components including the processor, memory, and I/O controllers on a spacecraft. However, when the same component in both strings fail (e.g., the processor), the system will fail although all other redundant components are still functioning properly. In contrast, an innovative avionics system architecture has been developed for ultra long-life system that uses redundant resources much more efficiently. This architecture employs generic function blocks that can be programmed to replace any type of components in-flight. In that way, each individual generic block is essentially equivalent to an entire redundant string of components in the conventional approach. Hence, the ultra long-life system can achieve much higher level of reliability while carrying much less components. For digital circuits, the generic redundant block can be implemented by large FPGAs. For analog or mixed-signal circuits, new technologies still need to be developed to implement the generic redundant block. Due to the programmability of the generic redundant blocks, the location of a specific component might not be pre-determined. Therefore, the connectivity among components has to be very flexible. Technologies such as wireless interconnection, switching network or free space optical connections are candidates for supporting the high flexibility interconnection. The performance and reliability of these technologies is being evaluated and breakthrough technologies and design techniques will be highlighted in the paper.
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