Minute 052: Main Bus B Undervolt

December 18, 2018

The MAIN BUS B UNDERVOLT warning light turns on, followed by the CMC (Command Module Computer) alarm light.

“We have a Main Bus B undervolt,” says Lovell, throwing a switch on the battery selector indicators. “We’ve got a lot of thruster activity here, Houston.”

“What’s the story with the computer now?” asks Swigert.

“It just went offline,” replies Lovell.

Haise hurries through the LM tunnel.

“There’s another Master Alarm, Houston,” says Lovell.

“I’m checking the quads,” says Swigert.

“Christ, that was no repress valve!” says Haise.

“Maybe it’s in Quad C,” says Swigert.

“We’ve got a computer restart,” reports Lovell.

“I’m going to reconfigure the RCS,” says Swigert.

“We’ve got a PNGS light ( Apollo Primary Guidance, Navigation and Control System),” says Lovell.

“The way these things are firing doesn’t make any sense!” says Swigert.

“We’ve got multiple cautions and warnings, Houston,” says Lovell.  “We’ve got a reset – restart.”

“Alright,” says Swigert, “I’m going SCS.” Swigert throws a switch that activates the Apollo Stabilization and Control System, taking over control from the Command Module Computer.

A shudder rolls through the ship.

In Mission Control, the Flight Surgeon watches a monitor.

“Jesus,” says the Flight Surgeon, “Flight, their heart rates are skyrocketing.”

“EECOM, what’s your data telling you?” asks Kranz.

“Uh, Oh-Two tank Two not reading at all,” says EECOM, “Tank One is at seven hundred and twenty one PSI and falling. Fuel cells One and Three are – – oh boy, what’s going on here? Flight, let me get back to you?”

“Flight, GNC , ” says GNC, “Flight, they’re all over the place – – they keep going close to gimbal lock.”

“I keep losing radio signal, ” says COMMS, “their antenna must be flipping around.”

“-P22, they’re going to have to do it manually, if not at all – -” continues GNC.

“One at a time, people!” replies Kranz. “One at a time, one at a time. EECOM, is this an instrumentation problem, or are we looking at real power loss here?”

“It’s reading – ” begins EECOM.


Jim Lovell: Tom Hanks
Jack Swigert: Kevin Bacon
Fred Haise: Bill Paxton
Gene Kranz: Ed Harris
EECOM White Team: Clint Howard
TELMU White Team: Jim Meskimen
CAPCOM: Brett Cullen
Flight Surgeon: Christian Clemenson

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