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50 years ago today, at 20:17 UTC (3:17pm EST), Apollo 11 Lunar Module Eagle landed on the moon in the Sea of Tranquility. This is the story of that landing. Some of this content will be repeats of previous facts.

We start after Neil and Buzz in the Lunar Module (LM) have disconnected from Michael Collins in the Command Service Module (CSM) and were heading down to the moon.

(Diagrams of the different spacecrafts are at the bottom of this article)

Decent to the surface
About 4 minutes into their decent and landing sequence, they got a program alarm. 1202. Unable to find this error in their book, a choice had to be made.
1. Continue with the unknown alarm and potentially crash into the moon
2. Abort, which could also fail due to the unknown alarm
3. Continue with the unknown alarm and potentially land successfully.

NASA discovered the alarm meant the computer was over loaded and was going to stop processing more requests until it caught up. NASA determined as long as the alarm was intermittent, they were good to continue landing. During the entire landing and confusion of the error, there was also a problem with the antenna causing communication problems.

Low on fuel and off course
With an unreliable computer, Neil took over control of the Landing Module (LM) and proceeded to manually land. Due to the issues with the computer, they now found themselves off course. Instead of a nice smooth landing area as expected, they were now heading into a rough, rocky area. With less than a minute of fuel left, they still had not found a safe place to land. The 30 second mark was their final chance to abort the mission. With dust being kicked up from the engines, they had no way of seeing the surface any more to see if it was safe to land, so they chose to just continue and land. They landed on the surface with 23 seconds of fuel left.

Video of the final minute of the landing, shot from the 16mm camera in the LM window.

We’re on the moon, now can we get out?
Buzz and Neil didn’t immediately get out after landing on the moon. In fact, their first order of business after a systems check was to take a nap. Being too excited from, you know, landing on the moon, they convinced NASA to let them skip their nap, however they needed to take the time to just rest and relax.

Three hours later, they were ready to exit onto the surface. All suited up, they started to depressurize the LM, however once the gauge read zero, they found there was still too much pressure to open the hatch.

“We tried to pull the door open, and it wouldn’t come open,” Aldrin said. “We thought, ‘Well, I wonder if we’re going to get out or not?’ It took an abnormal time for it to finally get to a point where we felt we could pull on a fairly flimsy door.”

In fact, Aldrin eventually resorted to peeling back one edge of the front hatch … but carefully. “You don’t wanna rupture that door and leave yourself in a vacuum for the rest of the mission!” he recalled with a chuckle.

Armstrong maneuvered toward the open hatch, aided by Aldrin. As Armstrong twisted his bulky suit to head out, unheard in the vacuum of the cabin, something small snapped. Armstrong’s backpack had broken off the ascent engine arming switch. This would not be discovered until 21 hours later when they needed that switch to leave the surface of the moon.

Leaving the moon
While making preparations to leave the surface, Buzz noticed the broken switch laying on the LM floor covered in moon dust. Unable to activate the broken switch, Mission Control advised the astronauts to retract the point of one of their Fisher-provided ballpoint pens and use the hollow end to push the broken circuit breaker switch. Aldrin, however, recalls it a bit differently.

“Since it was electrical, I decided not to put my finger in, or use anything that had metal on the end, I had a felt-tipped pen in the shoulder pocket of my flight suit that might do the job.”

“I inserted the pen into the small opening where the circuit breaker switch should have been, and pushed it in; sure enough, the circuit breaker held. We were going to get off the moon, after all,” Aldrin recounted. “To this day, I still have the broken circuit breaker switch and the felt-tipped pen I used to ignite our engines.”

For the most part, their docking with Collins in the command module and heading back to earth was pretty uneventful.

The astronauts used Eagle‘s ascent stage to lift off from the lunar surface, leaving the decent stage on the moon, and rejoin Collins in the command service module. They jettisoned Eagle before they performed the maneuvers that propelled the ship out of the last of its 30 lunar orbits on a trajectory back to Earth. Back in Earth orbit, they jettisoned the service module (the cylinder part of the CSM) and started re-entry in the Command Module. They returned to Earth and splashed down in the Pacific Ocean on July 24 at 16:50 UTC after more than eight days in space.

Contingencies and more stuff left on the surface
There was a fairly good chance that the mission would be a failure, and either Neil and Buzz would be left to die on the moon, or all three astronauts would be lost.

30 years after the moon landing, it was discovered that in preparation for this, President Nixon had a speech prepared if the worst should happen.

“Fate has ordained that the men who went to the moon to explore in peace will stay on the moon to rest in peace.

These brave men, Neil Armstrong and Edwin Aldrin, know that there is no hope for their recovery. But they also know that there is hope for mankind in their sacrifice.

These two men are laying down their lives in mankind’s most noble goal: the search for truth and understanding.

They will be mourned by their families and friends; they will be mourned by their nation; they will be mourned by the people of the world; they will be mourned by a Mother Earth that dared send two of her sons into the unknown.

In their exploration, they stirred the people of the world to feel as one; in their sacrifice, they bind more tightly the brotherhood of man.

In ancient days, men looked at stars and saw their heroes in the constellations.

In modern times, we do much the same, but our heroes are epic men of flesh and blood.

Others will follow, and surely find their way home. Man’s search will not be denied. But these men were the first, and they will remain the foremost in our hearts.

For every human being who looks up at the moon in the nights to come will know that there is some corner of another world that is forever mankind.“

Michael Collins recounts in his autobiography that his biggest fear wasn’t complete mission failure and loss of his own life along with Neil and Buzz, but that Neil and Buzz would be stuck on the surface of the moon and he would be forced to return home alone. “I am not going to commit suicide; I am coming home, forthwith, but I will be a marked man for life and I know it.”

Collins took this photo of the LM heading toward the surface. This photo is the only photo that includes every person in the world, alive or dead, except for Michael Collins. (it’s also the background photo on my phone)

Among the other things left on the moon, described in previous facts, each moon landing mission also left a mirror on the moon. This was done so that NASA (and you at home with the correct laser telescope) can beam a laser off the mirror to both verify the location of the moon landings, as well as monitor the distance between the moon and the earth (sub fun fact: the moon is very slowly moving away from the earth and will one day stop orbiting us. Don’t worry, we’ll all have been dead for millions of years by then.)

Finally, you know that footage of Neil going down the ladder, making those iconic footprints? Yeah, NASA lost that original footage as well as a bunch of other original footage from the first moon landing. Most of the video we all know today was actually just a recording someone made of the original footage (before it was lost) on a monitor.

The good news is they found where the tapes went. The bad news is they were part of a batch of 200,000 tapes that were degaussed — magnetically erased — and re-used to save money.

“The goal was live TV, We should have had a historian running around saying ‘I don’t care if you are ever going to use them — we are going to keep them’,”

They found good copies in the archives of CBS news and some recordings called kinescopes found in film vaults at Johnson Space Center.

You can re-live the entire Apollo 11 mission in real-time at: https://apolloinrealtime.org/11/