Bit of a specific one here but, I was looking at the Wikipedia article on the timeline of STS-51-L (Challenger disaster) today and I couldn’t figure out what one of the events meant.
A point came during the vehicle breakup when the high pressure fuel turbopumps were approaching their redlines. This I understand. The next event seems to be the final communication from the number two engine: “Channel A votes shutdown, two strikes on channel B”.
What the hell does this mean?
In: Engineering
the shuttle had 2 computers, which were both running the same code. the idea was that the two computers would cast votes on important decisions, and that normally they’d agree, but if one of them had an error (a glitch really) then the voting outcomes would be different and the error could be caught and an overruling decision would be made by the astronaut. From what you’ve written, it looks like computer A wanted to shutdown the engine. Not sure about 2 strikes on channel B, maybe astronaut slang for saying that channel B agreed with A?
Edit: Apparently the shuttle used a triple-redundant avionics computer, so there would be a majority vote on decisions ie: 2:1 against or for.
Edit edit: But the main engine controller was dual redundant
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