ELAPSED TIME 102:45:41.4. ENGINE STOP. THE EAGLE HAS LANDED. We made it!! As of THIS MOMENT 50 years ago, we’re on the freaking Moon!
What a ride! Just 2 hours ago, our lunar module Eagle undocked from command module Columbia. A little over 1 hour ago, Eagle did a 30 sec burn, lowering to a 50000 feet (15240 m) orbit above the surface. This was on the far side of the Moon, so we waited a bit before proceeding. If needed, we could have hung out for another 2 hour orbit.
Just 20 minutes ago, Eagle regained contact with Mission Control. They gave us a GO to proceed, so 13 minutes ago we started our final descent. So far so….oh no!! A computer alarm!! 1202?? What the heck is a 1202?? Turns out it’s the computer working exactly as designed. And that’s a good thing.
I’m hugely oversimplifying, but: since we needed our spacecraft to be as light as possible, we needed to have our computers do a lot, i.e. multitask. Again, oversimplifying, but on modern computers, our operating system can divvy up resources as it sees fit, and we can run multiple programs at once.
Back in 1969, we didn’t have enough power for that. We put one program at a time in the driver’s seat, and told the other programs to simmer down, hang onto their data and wait their turn. In theory, we weren’t ever supposed to run out of “passenger seats” in our big car.
As a safety precaution, we decided to keep our rendezvous radar on during the landing. Due to a problem with a power supply, the radar was erroneously trying to shove “passengers” into our vehicle like a clown car. Fortunately, our programmers were really smart.
If there were more passengers than seatbelts, the computer would automatically kick the extra ones out by rebooting. This meant that the passengers already strapped in didn’t lose any data, and that the driver could just keep on driving and ignore the reboots. Mission Control chose correctly to ignore the alarm.
It’ll be another few hours we til take one small step and do Science outside. Meanwhile, @astromichaelcollins is up in lunar orbit heating up some coffee. Everyone wave hello! 👋
Original post: https://www.instagram.com/p/B0Jtj9oF3py/