Tuesday, July 21, 2009

Lunar Links And One Great Story

With the recent anniversary of the Apollo 11 moon landing, interesting links are everywhere. First is an epic history of one of my favorite games: Forty Years Of Lunar Lander.

Another of my old favorites, Buzz Aldrin's Race Into Space (which I've written about before), now has a Window's version as an open source project, which you can download here. And for more information on BARIS, go to The Docking Module.

Now, a fantastic story from my good friend John Harwood:
Did I ever mention that Apollo 11 wouldn't have landed if not for my dad? That may sound overstated, but it's actually not. Admittedly, Apollo 11 wouldn't have landed if not for 29,999 other people as well, but my dad was one of them, and the story (as he would tell it) is pretty interesting.

Dad worked for TRW on a team of folks testing the guidance software for the lunar module. He tells of endless hours of running punch cards to test anything and everything they could think of to make sure the guidance and navigation system wouldn't have unexpected glitches. One evening, one of his fellow engineers spotted a very odd anomaly in a very rare and unlikely set of circumstances and wasn't sure whether that was something to bring forward as urgent as they were now a little over a month away from launch.

If the rendezvous radar, which was used to find the command module upon return of the ascent module, was running at the same time the system got overloaded, it would have completely halted the guidance computer, basically causing a modern day lock-up. If this happened when they were within a certain distance of the surface of the moon, that would have been an automatic abort situation as they would have had no guidance computer and they would have had to kick in the backup abort guidance system to take them back to the command module. That's a situation that basically should never happen because you don't use the rendezvous radar during descent and it was one of those strings of failures that would be very unlikely but would have dire consequences were it to happen.

So they brought this to the attention of a guy at MIT who dad always referred to as the "genius who thought in computer code" to check and see if that was serious enough to warrant a fix and what if anything could be done. So they did come up with a workaround to cause it to just give out an alarm instead of locking up, the computer would reboot, but only come back up with the important programs and ignore things like the rendezvous radar data (more specific details
here). This was a pretty big deal to fix since it was just over a month from launch and they had to have the finalized hardware put together. In those days, you didn't just put in a patch or re-write the software quickly, the "software" was comprised of hard-wired circuitry and they had to redo the entire wiring for that system and get it in place, but it was deemed important enough that they went ahead and did so.

Fast forward to the landing and sure enough, the rendezvous radar was left on, I don't recall if that was intentional or by oversight of the astronauts, and they did indeed overload the system, and when you listen to the audio of the mission, you hear them calling out system alarms 1202 and 1202, and without the reprogrammed workaround by the MIT guy, the guidance computer would have shut down and either rebooted to rest state or not come back at all, and they would have either had to abort or Neil would have had to try to fly manually the rest of the way down. I'd bet that Neil would have proceeded, but then they wouldn't have had any guidance computer for landing or subsequent take off.

Dad was recognized along with several other people from TRW for their contributions and given NASA's highest award, the
Silver Snoopy, for their efforts. And he wound up being randomly chosen from the award winners to get to go watch Apollo 12 take off. Right into a thunderstorm while getting struck by lightning. But that's another story...

So without my dad and the others at TRW who helped uncover the problem in testing, and the MIT team who reprogrammed the software, Apollo 11 would have either aborted a couple of thousand feet from landing, or a possible disaster may have happened later if they proceeded with the landing. So for me, every time I watch the landing, I love it when they call out those alarm codes, because I know that in an alternate universe where my dad didn't help bring that error forward, Apollo 11 aborted right then and there. And perhaps they had to do so much re-testing that Apollo 12 didn't launch by the end of the 1969 and we missed Kennedy's goal. And the Russians beat us there or gave such a PR black eye that the Cold War went a different way.

Everyone's dad is a hero in one way or another, but it's neat to have a story like that to tell. We landed on the moon because of my dad.

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