Apollo Missions 11 - 17: Glitches and Issues

Miscellaneous and Personal Stuff I Must Share
1

I’m interested in learning about the various technical difficulties experienced by the moon landing missions.

Right off the bat, we all know about Apollo 13 and the oxygen tank explosion on the service module.

With Apollo 11, Neil had to switch to manual mode on the Lunar Module (LM) landing to avoid rocks, boulders and a crater after overshooting the intended landing site. He had about 30 seconds of fuel left before safely landing.

Apollo 12 was apparently struck by lightning during lift off, which knocked out some electrical systems, but not the navigation system.

Apollo 14 almost aborted landing because the landing radar wasn’t working. Houston instructed them to turn off the breaker to the radar and turn it back on again and this solved the problem.

On one of the later missions the moon buggy steering was jammed. Two of the wheels couldn’t turn, but since the buggy had four-wheel steering they could still get around.

Oh, I forgot, the error messages reported by the Apollo 11 LM during descent were due to the fact that Buzz had turned on the ascent radar, but left it in standby mode, in case they needed to abort the landing. This extra CPU usage caused the overflow error messages that almost cancelled the landing.

So! What else transpired during the moon landing missions? I’m not interested in the Apollo 1 disaster, only the moon missions.

2

Resulting in the famous Try SCE to Aux and the subsequent beknighting of flight controller John Aaron as a steely-eyed missile man.

3

On Apollo 12, Alan Bean pointed the color camera intended for live TV transmissions at the sun, burning it out and rendering it useless.

4

He actually had plenty of fuel, he just didn’t know it. The fuel gauge was inaccurate.

5

John Young of Apollo 16 tripped over and broke a heat flow experiment.

6

If the OP hasn’t done so already, pick up A Man on the Moon, by Andrew Chaikin. It goes into a lot of this stuff.

Off the top of my head…

Apollo 11:

Armstrong switching to “manual” during the landing wasn’t exactly a glitch. Theoretically, the LM could reach the surface without any intervention (except possibly shutting down the engine, I’m not certain…). But the astronauts generally planned to take over control at some point prior to touchdown. And I have “manual” in quotes because there were a number of levels of automation. I’m not sure any of them were completely manual in the sense that the astronaut was making raw data control inputs. You could say he was flying by hand, but as I understand the LM’s systems, he could also be said to be sharing control to some degree.

Anyway, Armstrong took control sooner, and for longer, than had been anticipated.

Also on 11, they had to use a pen cap to push in a breaker prior to liftoff from the lunar surface. The switch itself had been broken off at some point. Even without that fix, they would have had several ways to fire the ascent engine.

12:

Already covered. But what I find most interesting is that NASA worried the lightning strike might have damaged the pyrotechnics that deployed the parachutes. They decided they may as well fly the mission and see what happened, a decision that would probably not go the same way today.

13:

Already covered. But I’ll add that despite the drama in the movie, there was no tough decision to close the reaction valves, thereby negating the possibility of landing. When the explosion happened those valves shut automatically, and the mission rules were clear that the landing was off. Lovell knew that, and if you listen to the actual audio you can hear the disappointment in his voice. The famous “Houston, we have a problem” is wrong. It was, “…we’ve HAD a problem”.

14:

Before the drama with the landing radar, they couldn’t dock the two spacecraft. Very nearly aborted the whole landing early on. Then on the surface, Shepherd and Mitchell lost their bearings and couldn’t find the crater they were looking for.

15:

A vice on the outside of the LM was installed backwards, so they had trouble disassembling the core samples they’d worked hard to obtain.

16:

They had problems with the command / service module backup control systems. Ken Mattingly was worried they’d cancel the whole thing and that he’d screwed it up.

17:

There was a change of ground receiving station / frequency just at the moment of liftoff from the lunar surface. Nobody realized that, so once they had blasted off they found themselves with no comm. Astronaut Jack Schmitt changed antennas or frequencies or something and reestablished communications. I got to talk with him about that once when I was interviewing him for an article I wrote.

7

14 had a number of problems. Llama Llogophile mentioned the docking problem during Transposition and Docking - it went smoothly, the Command Module properly inserted its probe into the lunar module, but the docking mechanism refused to latch. They tried a few times, eventually striking the Lunar Module hard which enabled the docking mechanism.

Later, as the LEM descended towards the moon, they noticed that the abort switch was randomly triggering. They realized that there was a short circuit in the switch, likely from a piece of solder that might have been broken off due to the hard hit when they docked earlier in the mission. Once “PDI”, or powered descent would begin then the switch would be monitored by the computer and would abort if closed. It was possible for the astronauts to override a bit in the guidance computer to disable aborts, but it would be a race and mistyping anything in the computer could add any number of additional problems…

The MIT team that developed the computer realized that when a program started, it would write its ID to a register to display on the DSKY (Display and Keyboard). Other programs would check that ID to see what was running, but it had no effect on the main program. So, they started P63 which was the program that controlled the descent phase, and then changed the number to something like 74 which meant they were aborting. That way, if the abort switch triggered, the computer would ignore it since it would check the running program and think they were already aborting. They had to manually set a few other flags, and Alan Shepherd had to manually initiate the descent, but once started they could turn off the “Abort Enable” flag and then set everything back as expected. It’s a brilliant hack.

I’ve heard some computer scientists speculate that this hack might have prevented setting the landing radar into the correct mode for landing which would explain the problem further down line.

8

I’ve never seen proof of this. In fact I believe they added extra fuel on subsequent missions just to be safe.

9

Fascinating read. Thank you.,