The morning of Nov. 14th, 1969, was stormy at NASA’s Cape Canaveral launch site, but the Saturn V on the launchpad was going to the moon regardless. Conditions weren’t bad enough to force a scrub, and President Nixon was on site so no one wanted to see the schedule slip. At 11:22 a.m., the monster rocket roared to life and cleared the tower. It was a perfect launch for the first 37 seconds.
Then, all hell broke loose.
Inside the Command Module, Commander Pete Conrad saw a flash through the window at the same time as he felt the rocket shudder. Almost immediately the spacecraft’s master alarm rang through the cabin and the control panel lit up like a Christmas tree with warning lights.
Everything had failed.
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Warning lights said the spacecraft had lost all power and was running on batteries, the ones the crew would use for power during atmospheric reentry. If this was true, they were in a heap of trouble.
But the warnings didn’t match the physical sensations. Lunar Module pilot Al Bean knew that if the spacecraft was working on batteries it would have to have separated from the rocket and the Service Module. That separation, thanks to the powerful launch abort system, would subject the crew to a sudden increase in g-forces. He hadn’t felt any kind of jolt. He also hadn’t felt the rocket change course at all. They also had power, and as long as they had power they weren’t doomed.
Gerry Griffin, far away in Houston’s mission control, was as stumped as the crew. He was also nervous. Apollo 12 was his first mission as lead flight director and he really hoped he wouldn’t be the first person to abort a lunar launch. His former Air Force training, not to mention the hours of launch simulations, kicked in and he calmly looked over the gibberish data on his console. Griffin turned to his environmental control engineer, EECOM, John Aaron, the 24-year-old who had the unenviable job at that moment of troubleshooting the problem.
The gibberish data was familiar to Aaron. He’d seen the same pattern before when a test conductor had dropped the spacecraft’s power system to an unusually low voltage. The low voltage, in turn, affected the signal conditioning equipment (SCE), a box of electronics that translated information from sensors into signals that fed the displays in the spacecraft and mission control. In its normal setting, the box would shut off with low voltage. But in the auxiliary setting, the box would continue to operate in any power condition.
Aaron didn’t know what had happened, but he knew something had knocked the signal conditioning equipment offline. He turned to Griffin and told him to try turning SCE to AUX.
Griffin had no idea what that meant; at first he heard Aaron say turn SCE to off. Griffin passed the command to Gerry Carr, the mission’s Capcom, who was equally confused. A new worry came to Griffin’s mind: if Carr, an astronaut, had no idea what or where the SCE switch was, how could the crew on Apollo 12 be expected to find it in time? When Conrad acknowledged the command over the radio, Griffin’s concerns were confirmed.
“FCE to auxiliary,” Conrad called down. “What the hell is that?” Carr corrected him, repeating clearly “SCE” over and over.
The confusion over “SCE” in mission control and the spacecraft would have been funny had the stakes not been so high.
It was Bean who came to the rescue. Though neither Conrad nor Command Module pilot Dick Gordon knew what the SCE switch was, Bean did and knew where to find it. He flipped the switch, putting the signal conditioning equipment in a state where it could function with low power. One by one, systems came back to life revealing a perfectly healthy rocket and spacecraft.
Amazed, Conrad joked that they might have been hit by lightning. They didn’t know it at the time but they had. Twice. As the Saturn V rose through the electrically charged storm clouds, it turned into a lightning rod. Two separate bolts struck the rocket then followed its contrails all the way to the launch pad to strike again.
Two and a half minutes after the first strike took out their displays, everything in the spacecraft was running normally. The crew, displaying the characteristic giddiness of three men who had nearly escaped a fatality, spent the rest of their ascent to orbit in fits of laughter.
Image: The Apollo 12 mission awaits launch atop the monster Saturn V rocket. Credit: NASA