In the news today:
- NASA to skip repair of Orion electronics unit
- NASA will fly Orion deep-space crew capsule ‘as is,’ despite failed component; The agency claims there is enough redundancy in the system
The Space News article beings:
NASA will not repair a faulty electronics unit on the Orion spacecraft recently completed for the Artemis 1 mission after concluding there was sufficient redundancy in the overall system.
In a Dec. 17 statement, NASA said it had decided to “use as is” one of eight power and data units (PDU) on the Orion spacecraft, which provide communications between the spacecraft’s computers and other components. One of two redundant channels in one of two communications cards in that PDU is not working.
Taken naively, "One of two redundant channels in one of two communications cards" could sound like there's a box with four copies of the same thing, and as long as one of the four continues to work, everything will be okay.
Is there quadruple redundancy here?
If so, why so much? Was it in anticipation of failures before launch in a location that's hard to get to (i.e. foresight) or out of an abundance of caution, or something else?
If not, how much redundancy is there exactly?