What is a bus undervolt?

Transcription

Swigert (CMP): Okay, Houston, we've had a problem here.

CAPCOM Jack Lousma (CC): This is Houston. Say again, please.

Lovell (CDR): Uh, Houston, we've had a problem.

Lovell (CDR): We've had a MAIN B BUS undervolt.

CAPCOM Jack Lousma (CC): Roger MAIN B undervolt.

CAPCOM Jack Lousma (CC): Okay, stand by Thirteen, we're looking at it.

A "bus" is a physical electrical interface where many devices share the same electric connection. This allows signals to be transferred between devices (allowing information or power to be shared). A bus often takes the form of an array of wires that terminate at a connector which allows a device to be plugged into the bus.

http://forum.cakewalk.com/Basic-Question-m1553465.aspx

Yes, I've been boning up on Apollo 13 and found that Yahoo answer about "bus." Can't find the "undervolt" part. All reports on Apollo 13 seem to assume the reader knows that. This one doesn't!

Maybe I found it myself just now when I wasn't even looking for it.

"Master caution and warning triggered by DC main bus B undervoltage."
http://history.nasa.gov/apollo/problem.html

The "-age" ending helps. Maybe it just means "power shortage," specifically in one huge "outlet" denominated "B."

Still open to answers!

Poking around some Apollo 13 discussion and using my physics teacher background, I suggest that they meant that the bus in question was not receiving as much voltage is it was supposed to, and therefore its function was compromised. (I found a fascinating discussion of intentionally supplying a reduced voltage to your computer to make it run cooler, a process called undervolting, but that's another story!)

(electricity) An undervoltage relay which removes a motor from service when a low-voltage condition develops, so that the motor will not draw excessive current, or which prevents a large induction or synchronous motor from starting under low-voltage conditions.

http://www.answers.com/topic/undervoltage-protection

Thanks to both of you!