In 1969, lightning struck Apollo 12 seconds after launch; John Aaron’s “SCE to AUX” call restored telemetry and helped save the Moon mission

On November 14, 1969, three astronauts were aboard a 363-foot Saturn V SA-507 rocket with rain pelting the launch tower when suddenly the sky spoke up, not once, but twice. Just thirty-six seconds after takeoff, lightning struck the craft. Another sixteen seconds later, it hit again. The lights on the command module went wild, the astronauts lost their main instruments, and in one of those truly frightening moments, it became a real question of whether Apollo 12 was a spaceship built to endure that unforeseen mishap.

According to NASA's own 2019 description of this event, the first strike hit the craft somewhere around 6,000 feet above ground level, and the second, sixteen seconds later, knocked out the spacecraft's guidance platform, sending commander Pete Conrad's voice over the radio: "OK, we just lost the platform, gang. I don't know what happened here; we had everything in the world drop out." It was a 24-year-old flight controller remembering something strange he had noticed during a dull night shift a year ago, and shouting four words that made everyone in the room go blank: "Try SCE to auxiliary.”

The rocket that accidentally invented its own weather


Apollo 12 did not get hit by an existing storm. Rather, the ionized cloud of hot exhaust created by the rising Saturn V acted like a giant lightning rod and initiated the electrical discharges. NASA's own pre-launch weather rules at the time were built to check for one thing: active lightning near the pad. They had no way to flag a rocket that could trigger its own strike out of a sky that wasn't otherwise showing that kind of activity, which is exactly the gap that let Apollo 12 launch that morning. The 3,000-ton Saturn V itself, and the possibility that its exhaust plume could complete a circuit through a charged but non-stormy sky, simply wasn't part of what forecasters were checking for.

The misunderstanding of such an important factor is precisely why atmospheric scientists were prompted to investigate the process of "triggered lightning". Indeed, a 1989 peer-reviewed paper titled “Natural and Artificially Initiated Lightning,” published in the journal Science, by lightning researchers Martin Uman and E. Philip Krider, cited the Apollo 12 lightning-initiation event as a key early trigger for what had by then become an established field of research into rocket-and-structure-triggered lightning. This led to significant changes in the decision-making process regarding launching into an active storm system for NASA and the US Air Force.

The switch nobody had heard of

Back in Mission Control, the readings seemed cryptic: fuel cell pressures, AC bus voltages, and guidance system information all displaying meaningless values at once, usually meaning a full system malfunction. But the flight controller John Aaron knew better; a year earlier, while working a night shift, he had happened to watch a routine ground test at Kennedy Space Center in which operators accidentally dropped the spacecraft's power. The telemetry that came back wasn't just blank zeros, it settled into the same strange, specific numbers he was now looking at. Curious, Aaron had traced that anomaly on his own time to an obscure piece of hardware called Signal Conditioning Electronics (SCE), and learned that switching it into its auxiliary power mode let it keep working even on low voltage. That's the memory he drew on now.

After Aaron uttered "SCE to AUX" into the communications channel, flight director Gerry Griffin didn't recognize the solution, and neither did the astronauts. There was some confusion in the radio communication before astronaut Alan Bean finally found the tiny switch on the board and turned it on. The telemetry readings returned to normal immediately, and the mission that landed near the Surveyor 3 spacecraft and safely splashed down on November 24, 1969, continued. Apollo 12 went on to land near the Surveyor 3 spacecraft and splashed down safely on November 24, 1969. According to NASA's technical investigation of the incident, the underlying cause traced back to a gap in the launch weather criteria, not a flaw in the Saturn V rocket itself, and the incident directly shaped the more restrictive launch rules used today.

The unglamorous truth

The real story is not so much about the genius of one man but rather of a system that thought highly enough of its own obscure corner cases to run simulations for them, and of a control room that had somebody paying attention to a tedious test that everyone else may have thought to be boring. In a world where technology companies boast about “moving fast,” Apollo 12 reminds us that living through the unexpected generally requires preparation: someone studying the manual, performing the strange simulation, remembering the edge case scenario, which suddenly became crucial only 36 seconds into flight.