On the morning of November 14, 1969, ominous clouds blanketed the sky above the Kennedy Space Center. But the rain was dying down and conditions were within the minimums of what was considered adverse, so Apollo 12 lifted off. About 36 seconds in, things got weird.
The crew didn’t realize it, but a powerful electrical surge had shot through the Saturn V. And about 20 seconds later, mother nature would prove that lightning can and will strike the same place twice. Apollo 12 was in the dark. Several major systems went offline, including all three fuel cells, the spacecraft’s main source of power. If they didn’t find a solution in the next 90 seconds, Apollo 12 would have to abort.
On the ground at the Manned Spacecraft Center in Houston, mission control was just as confused. Their consuls were reading nonsensical telemetry data from the spacecraft, giving the team no sign of a solution. This was a nightmare scenario for flight director Gerry Griffin. Just over a minute into his first mission as lead flight director, he was facing a potential disaster. But if Griffin learned anything from his mentors, there were a lot of options and failure was not one of them.
SCE to Auxiliary was the answer to their problems, and 24-year old EECOM John Aaron was the only one who knew it. A year earlier, the flight controller was in mission control during a simulation in which the spacecraft’s voltage was accidentally dropped. The change affected the Signal Conditioning Equipment or SCE which was a small power supply that provided voltage to critical instrumentation points in various systems - including the fuel cells. If the power supply failed, an auxiliary supply could be switched on.
All the crew had to do was find the right switch, which wasn’t a simple task given the complexity of the spacecraft’s display. Astronaut Al Bean was the only member of the crew who knew which switch to flip. And just like that, the spacecraft's systems came back online and the flight controllers were able to read the data again.