CDR: Lift-off. The clock’s running.
LMP: Three seconds.
CDR: I got a yaw program -
LMP: Six seconds.
LMP: There’s 10 seconds.
CMP: Clear the tower.
CDR: Roger. Clear the tower. I got a pitch and a roll program, and this baby is really going.
CMP: Man, is it ever!
CC: Roger, Pete.
CMP: Twenty seconds.
CDR: That’s a lovely lift-off. That’s not bad at all.
CMP: Everything’s looking great. Sky’s getting lighter.
CDR: Okay.
LMP: Thirty seconds.
CDR: Looks good.
CDR: Roll’s complete.
I24P: This thing moves, doesn’t it?
CC: Roger, Pete.
CMP: What the hell was that?
CDR: Huh?
CMP: I lost a whole bunch of stuff; I don’t know - -

What the hell was that? That was lightning.

40 years ago last Sunday, November 14th, perhaps the second greatest engineering debug effort took place in NASA history. Second behind Apollo 13 was Apollo 12 and we hardly know about it. (Well maybe we could debate its place among Skylab and Solar Max Missions.) No great Ron Howard movie for this effort. Only a few months removed from the first lunar landing, Apollo 12 began its trip to the moon. As the rocket rose on a plume ionized exhaust, it created a big expensive lightning bolt. It only took 36 seconds into the mission before disaster came calling and then again 16 seconds later another bolt struck the rocket. The combination of the two strikes knocked out the astronaut’s attitude indicator, showing the orientation of the rocket. Telemetry systems that report the rockets status to the ground also began returning meaningless data and other systems began to quickly drop off-line as voltage issues ran through the rocket. Without telemetry data, ground control had no way of determining rocket status, and the mission director was slowly making a case in his head to abort the mission. In an abort, escape rockets would separate the small command module from the top of the whole rocket, and once it reached a safe distance the rest of the rocket would be exploded on purpose, thus bringing a quick end to man’s second attempt at the moon. Mission Director, Gerry Griffin was seconds away from issuing an abort command, without telemetry he had little choice but to save the lives of the three astronauts inside.

Then a surprising calm voice called out over the radio.

‘Try SCE to aux”

That voice was John Aaron. Aaron had seen the problem before and remembered a quick fix. He had seen a similar problem in the lab with the Signal Conditioning Equipment (SCE) system and by switching its power to auxiliary the problem was corrected.

So surprised by the un-scripted suggestion, the flight controllers asked him to repeat the request.

And a second time John said “Try SCE to aux”. Alan Bean inside the command module knew the switch and moved it the AUX position and telemetry was restored. NASA was able to verify that the rocket was on track and gave a “go” for the 1st staging while the astronauts began resetting the rocket’s power generation system. A few minutes later most systems were back to functional status and the astronauts joked about that being an interesting “simulation” they were given. In the highly scripted NASA world, such quick action and thinking is rarely needed. Thankfully 40 years ago this weekend, when it was needed - it was there.

Joe McDevitt
CTO