"It is understood by AFRL and NASA that the objectives listed below are both extremely challenging and may not be complete. [Vendors] are encouraged to suggest alternative approaches to meet the top level objective of defining a processor and associated software suite that provides high performance, fault tolerant, power scalable computing suitable for the broad range of space/mission environments and especially the extreme environments expected in future NASA and Air Force missions," the agencies stated.
One of the main issues that comes with building any space systems is radiation. NASA has talked about space mission's use of radiation-hardened computer chips in the past, noting that such systems contain extra transistors that take more energy to switch on and off. Cosmic rays can't trigger them so easily.
Rad-hard chips continue to do accurate calculations when ordinary chips might "glitch." NASA said it relies almost exclusively on these extra-durable chips to make computers space-worthy. But these custom-made chips have some downsides: They're expensive, power hungry, and slow -- as much as 10 times slower than an equivalent CPU in a modern consumer desktop PC. It is always an issue to give spacecraft as much computing horsepower as possible.
An example of what a NASA system handles today: According to NASA, the International Space Station's U.S. segment alone handles 1.5 million lines of flight software code run on 44 computers communicating via 100 data networks transferring 400,000 signals (pressure or temperature measurements, valve positions, etc.). Main control computers have 1.5 gigabytes of total main hard drive storage in the U.S. segment compared to modern PCs, many of which have more than 500 gigabyte hard drives.
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