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In the news today:

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?

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  • $\begingroup$ So you would like to know if the two communications cards are redundant ? And couldn't (some of) the eight PDU's be redundant too ? $\endgroup$
    – Cornelis
    Dec 19, 2020 at 9:58

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According to Spacenews.com on December 17 "NASA said it had decided to “use as is” one of eight power and data units (PDU)on the Orion spacecraft". The reason it is so redundant is so that if one fails, you still have 7 identical units. In the event of all of the units failing, which is unlikely, i believe Orion has a backup unit to abort the mission.

EDIT: apparently you already said something about the article lol

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    $\begingroup$ So any one of them can do the job? This unit is octupley redundant? (sp?) Can that be confirmed independently? I used these somewhat non-technical articles as background sources in order to formulate the question, I'm not sure they are sufficiently reliable as supporting sources for answers. Anyway, thanks for your answer post and Welcome to Space! $\endgroup$
    – uhoh
    Dec 20, 2020 at 1:07
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    $\begingroup$ Do you have a source that confirms that every function on Orion is supported by all 8 PDUs? A car has 4 wheels, but that doesn't mean that it's not bad if one fails. $\endgroup$ Dec 20, 2020 at 1:38
  • $\begingroup$ This seems to be the most unlikely interpretation of the imprecise text. It implies that there is a 32-fold redundancy because of "One of two redundant channels in one of two communications cards in that PDU". $\endgroup$
    – asdfex
    Dec 20, 2020 at 9:15

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