5 Terrifying Moments During the Apollo 11 Moon Landing Mission

5 Terrifying Moments During the Apollo 11 Moon Landing Mission


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As the dust settled on the moon’s Sea of Tranquility after the landing engine of the Apollo 11 Lunar Module shut down, Commander Neil Armstrong’s steely voice crackled over the radio at Mission Control, a quarter of a million miles away: "Houston, Tranquility Base here. The Eagle has landed.”

The relief on Earth was tangible: “Roger, Twan… Tranquility. We copy you on the ground. You got a bunch of guys about to turn blue. We're breathing again. Thanks a lot,” Spacecraft Communicator (CAPCOM) Charles Duke stuttered to Armstrong who, with Lunar Module Pilot Buzz Aldrin, had just become the first astronauts to safely land on the moon.

This historic exchange on July 20, 1969 marked the end of a perilous journey to the lunar surface, but a multitude of threats still faced the pair of NASA astronauts during their surface operations—while Command Module Pilot Michael Collins looked down alone, orbiting high above the lunar landscape.

And, despite arriving in one piece, the expert touchdown was by no means certain. Below are five of the scariest moments during Apollo 11.

1. Missing the Mark on Touch-Down Amid Multiple Alarms

After arriving in lunar orbit and later separating from the Command Module to begin their landing sequence, Armstrong and Aldrin had little idea that their moon landing plans had already been modified by an overlooked effect of Newtonian physics.

A couple of hours earlier, as the spidery Lunar Module “Eagle” undocked from the Command Module “Columbia,” residual pressure inside the tunnel that connected the two spacecraft before undocking wasn’t sufficiently vented, causing Eagle to get an additional boost as it separated.

It was slight, but at around nine minutes before touchdown, Armstrong realized they were going to overshoot their landing site, estimating they’d miss by approximately three miles (which was a close educated guess, they actually missed by four). As the moon is littered with boulders and craters, the planned landing site was chosen as it was comparatively smooth. So with the modified flight plan, the duo had to find another suitable place to safely touch down.

As if that wasn’t enough drama, the Eagle’s computer had been distracting them with program alarms throughout their descent. Radio communications with Mission Control were also patchy. The recurring alarm was being triggered by the onboard landing computer that was warning of an overload. Fortunately, as the alarm was intermittent, Mission Control deemed the risk of computer overload low and green-lit the landing.

As the minutes ticked down, and the pair watched the lunar surface getting closer by the second, another problem became clear: they were burning more fuel than calculated. Due to their overshot landing, they were nearly running on empty so there was even more urgency to find a landing spot.

“You never [want to] go under the ‘Dead Man’s Curve,’” Flight Controller Steve Bales later recalled in an interview. “It was an altitude [where] you just don't have enough time to do an abort before you had crashed … Essentially, you're a dead man.”

With only 30 seconds of fuel left in the tank, Armstrong guided the Eagle softly down onto its impromptu landing site that, moments later, would become “Tranquility Base”—the first (temporary) human outpost on the moon.

2. Post-Landing Explosion?

As the adrenaline ebbed and the astronauts carried out their post-landing tasks, another problem was brewing. Although it had been shut down, sensors were detecting a pressure build-up in the landing engine fuel line. This could mean only one thing: ice had accumulated in the line, plugging it, and the backed-up fuel vapor was getting heated by the hot engine.

Discussions between NASA and Grumman Aircraft Engineering Corporation, the company that oversaw the Lunar Module’s development, deemed this increase in pressure a hazard that may trigger a deadly explosion if not remedied. So they drew up plans to vent the system.

“We all felt that the consequences of an explosion, even of the relatively small amount of fuel remaining in that short section of line, was unpredictable and unacceptable,” wrote aerospace engineer and “Father of the Lunar Module” Thomas J. Kelly in his book 2001 book, Moon Lander.

Before the instructions could be relayed to Armstrong and Aldrin, however, the ice plug thawed, the gas was released, and the problem remedied itself.

3. Dangers of Moon Dust

Even though the ground beneath Tranquility Base had the appearance of being free from any boulders that may have damaged the Lunar Module as it touched down, before Apollo 11, scientists couldn’t be absolutely sure that Armstrong and Aldrin would land on stable ground. What if the stuff acted like quicksand? There was also the possibility that the fluffy accumulations of moon dust covered jagged shards of rock that could cause injuries to moonwalkers or to the lander itself.

Although previous robotic missions, such as the Surveyor landers, were designed to study the lunar surface as a prelude to planning later Apollo missions, it wasn’t until Armstrong’s “one small step” crunched into the grey powder that NASA was sure the surface was safe for extravehicular activity (EVA).

While this may be a minor point in the annals of the Apollo Program, lunar dust is no joke. Created over billions of years by meteorite impacts, the moon lacks processes that would erode these minuscule particles into smoother shapes. Apollo astronauts found the abrasive dust to be more than a nuisance.

Later missions after Apollo 11 featured longer EVAs, and there are reports about these tiny shards of rock permeating Lunar Module interiors, coating helmet visors, jamming zippers and even penetrating layers of protective spacesuit material.

“All of the astronauts complained of the problems with dust,” said Brian O’Brien, a Rice University professor from 1963 to 1968 who built radiation and dust experiments for the Apollo missions. “The very access to the moon stirs up dust. And the walking of an astronaut or the movement of a rover stirs up dust. The dust will travel ballistically, because there’s no atmosphere, and it will stick to anything and everything.”

4. Alien Infections?

Though scientists are now acutely aware of the impacts of space radiation and dust on astronaut health, in those pioneering days of 1969, there was some degree of trial and error.

By 1969, only landed a handful of robotic landers had touched down on the lunar surface. And while these landers confirmed that the moon’s surface was rocky, dusty, covered in craters and devoid of complex life forms, some precautions for possible infection by alien microbes had to be taken—but only after the Apollo astronauts became infected by these hypothetical space germs.

After risking their lives for the advancement of humanity, Armstrong, Aldrin and Collins had the dubious pleasure of being stuck in planetary protection quarantine on their return, just in case a deadly space-borne plague had hitched a ride with them.

As soon as their re-entry capsule splashed down in the Pacific Ocean on July 24, the trio was transferred to a mobile quarantine facility inside which they were transported to NASA Lunar Receiving Laboratory at Johnson Space Center where they had access to a larger quarantine facility until their release on August 10, 1969.

5. Alternate Reality: A President’s Announcement of Mission Failure

Probably the most terrifying moment of the Apollo 11 landing, however, didn’t actually happen.

A speech, prepared for then-President Richard Nixon in the event of mission failure, was released to the public 30 years later, detailing the White House’s response should the unthinkable have happened. Any number of things could have gone wrong during that pioneering mission, so, to prepare, the president was ready to address the nation when it became obvious the mission was lost.

The text ends on a poignant note: “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.”

The “In Event of Moon Disaster” speech was never read but was instead filed away as a reminder that space exploration is a dangerous endeavor that has claimed the lives of many brave explorers since the beginning of the space age. Meanwhile, the men of Apollo 11 became the first humans to set foot—and survive—on an alien world.

Want more HISTORY? Check out these stories:

See Photos of How Astronauts Trained for the Apollo Moon Missions

How Landing the First Man on the Moon Cost Dozens of Lives

Apollo 11 Moon Landing Timeline: From Liftoff to Splashdown

Why Civil Rights Activists Protested the Moon Landing

How Many Times Has the U.S. Landed on the Moon?

Why the Air Force Almost Blasted the Moon with an H-Bomb

The Amazing Handmade Tech That Powered Apollo 11's Moon Voyage

Watch the full episode of Moon Landing: The Lost Tapes.


Apollo 11 – The Key Moments

The 18 key moments of the most famous space mission in history.

Book online now and upgrade to a free annual pass

On a sweltering July day in 1969, the largest rocket ever built lifted off a Florida launchpad, carrying with it three American astronauts about to make history. Destination: Tranquility Base, the Moon.

The Apollo 11 mission was the culmination of eight years of frenzied work at NASA, ever since 1961 when US President Kennedy promised to beat the Russians and land a man on the Moon by the end of the decade.

Other Moon missions followed, but no other moment in history has so captivated our collective passion to explore the unknown than the first time that humans walked on the surface of an alien world.

As we anticipate the 50th anniversary of the first Moon landing in July 2019, here are the key people and moments of Apollo 11.


Apollo 11: Secret Nixon speech reveals what would happen if Armstrong and Aldrin couldn't come back

Apollo 11 was a rousing success and astronauts Neil Armstrong and Buzz Aldrin were able to walk on the Moon and…

Following are three critically important leadership examples from JFK which all Americans should recognize and respect, especially as the USA aspires to land women and men on the moon by 2024 in furtherance of building a permanent lunar base for a springboard to Mars:

1. Formulate and effectively communicate a bold vision to unify the nation.

2. Foster innovative thinking and leverage new technology to advance science.

3. Take big risks to demonstrate the immense possibilities of human ingenuity.

JFK’s courageous actions to effectuate space exploration yielded countless scientific and technological discoveries which have since altered the course of society for the greater good — and, by extension, the human race.


Key Moments To The Lead-Up Of Apollo 11 Moon Landing

Neil Armstrong took his first small step for man on the moon 50 years ago tomorrow. And when he did it, he walked on into the history books. Andrew Chaikin is with me now. He wrote the book "A Man On The Moon: The Voyages Of The Apollo Astronauts." Good morning.

ANDREW CHAIKIN: Good morning.

KING: So how did the landing play out?

CHAIKIN: Well, landing on the moon is basically a controlled fall out of orbit.

CHAIKIN: And you only have enough fuel for one try.

(SOUNDBITE OF ARCHIVED RECORDING)

CHARLIE DUKE: Eagle, Houston. You are go to continue powered descent. You are go to continue powered descent.

CHAIKIN: The onboard computer, which was absolutely primitive by today's standards, had had about 37,000 words of memory, although those were very.

CHAIKIN: . Well-chosen words. But the computer was critical. It was absolutely the third crew member in that lander. And everything pretty much went OK until about five minutes into the final descent to the moon.

(SOUNDBITE OF ARCHIVED RECORDING)

BUZZ ALDRIN: Got the Earth right out our front window.

CHAIKIN: . When, all of a sudden.

(SOUNDBITE OF ARCHIVED RECORDING)

NEIL ARMSTRONG: Program alarm.

CHAIKIN: . Something was wrong with the computer.

(SOUNDBITE OF ARCHIVED RECORDING)

ARMSTRONG: Give us a reading on the 1202 program alarm.

CHAIKIN: Some of the people who were really caught up short by these alarms were the people who had actually written the software for the computer, and they were at MIT in Cambridge, Mass. And one of the main authors of that software was a young computer engineer named Don Eyles.

(SOUNDBITE OF ARCHIVED RECORDING)

DON EYLES: We looked at each other with sort of blank faces. Something was going on in the computer that we didn't understand. If it had been up to me, I would have called an abort.

KING: That is absolutely terrifying. So why did they not abort?

CHAIKIN: Well, one of the heroes here is the flight director, Gene Kranz. Couple of weeks before the mission, they had done a simulation in which computer alarms had come up, and they had not been ready for them. Kranz said to his computer guys, I want you guys to be prepared for every conceivable computer alarm that might come up. So when these alarms came up, there was one guy in a back room. He was only 24 years old. His name was Jack Garman.

(SOUNDBITE OF ARCHIVED RECORDING)

JACK GARMAN: It's executive overflow. If it does not occur again, we're fine. It's continuous that makes it no-go. If it reoccurs, we're fine.

KING: He's so calm. We're fine. We're fine.

CHAIKIN: It's absolutely amazing to hear him. (Laughter) It's just one of these stunning examples of the amazing performance of these young people who were given awesome responsibility during these missions.

(SOUNDBITE OF ARCHIVED RECORDING)

DUKE: You're looking great to us, Eagle.

CHAIKIN: So they're still about 3,500 feet above the moon when Gene Kranz pulls his flight controllers and then finally gives them the go-ahead to continue the landing.

(SOUNDBITE OF ARCHIVED RECORDING)

GENE KRANZ: OK. All flight controllers, go, no-go for landing. Retro.

KRANZ: Capcom, we're go for landing.

DUKE: Eagle, Houston, you are go for landing, over.

ALDRIN: Roger, understand, go for landing.

CHAIKIN: And then after that, there were more alarms on the computer.

(SOUNDBITE OF ARCHIVED RECORDING)

DUKE: Roger, 1201 alarm. We're a go. Same type. We're a go.

EYLES: We had four more of those alarms before we actually got to the surface. And at one point, the display went blank for a period of about 10 seconds. Armstrong laughed about it afterwards.

KING: I guess if you're going to have a - if you're going to have to go through that, have a sense of humor, right?

CHAIKIN: Oh, you know, this is exactly what Armstrong had signed up for. But by the time that Armstrong actually got to look out the window and see where the computer was taking them, he saw they were headed for a crater the size of a football stadium. And it was completely surrounded by boulders, which were themselves the size of small cars.

(SOUNDBITE OF ARCHIVED RECORDING)

ARMSTRONG: Pretty rocky area.

CHAIKIN: So he took over semi-manual control to fly past the crater and head on and look for a safer spot.

(SOUNDBITE OF ARCHIVED RECORDING)

ALDRIN: Altitude-velocity, light.

CHAIKIN: Down in Mission Control, nobody knew about the big crater in the boulders. For Gene Kranz and his controllers, this was getting very, very tense.

(SOUNDBITE OF ARCHIVED RECORDING)

KRANZ: During all of our training exercises, we had normally landed by this time. And from this time on, all we do is give him readouts on fuel remaining.

(SOUNDBITE OF ARCHIVED RECORDING)

CHAIKIN: Armstrong is trying to bring the lander straight down the last hundred feet. And what's happening now is that the lander's engine is blowing dust away in all directions. And it makes it very hard for him to judge his motion over the surface. Armstrong knew that his fuel supply was dwindling, and Kranz knows he and his guys really are not running the show anymore. It's going to be up to Neil Armstrong whether to land or not.

(SOUNDBITE OF ARCHIVED RECORDING)

KRANZ: Now, this is when the - it started to get sort of dicey in the Mission Control Center because we're in to the point where literally many of us have stopped breathing at that time.

(SOUNDBITE OF ARCHIVED RECORDING)

ALDRIN: Forward, forward, 40 feet down, 2 1/2.

CHAIKIN: Thirty feet is the altitude above the surface. Two and a half down means that they're descending at a rate of 2 1/2 feet per second.

(SOUNDBITE OF ARCHIVED RECORDING)

ALDRIN: Kicking up some dust, 30 feet, 2 1/2 down, faint shadow. Four forward.

CHAIKIN: Four forward is the velocity over the surface, the forward velocity of four feet per second.

(SOUNDBITE OF ARCHIVED RECORDING)

ALDRIN: Four forward - drifting to the right a little, down a half.

CHAIKIN: Thirty seconds means they have 30 seconds left before they either have to abort or go ahead and land with the fuel they have remaining.

(SOUNDBITE OF ARCHIVED RECORDING)

ALDRIN: Down a half. Contact light. OK. Engine stop. ACA - out of detent.

ALDRIN: Mode control - both auto. Descent engine command override - off. Engine arm - off. Four hundred thirteen is in.

DUKE: We copy you down, Eagle.

ARMSTRONG: Houston, Tranquility base here. The Eagle has landed.

DUKE: Roger, Tranquility. We copy you on the ground. You got a bunch guys about to turn blue. We're breathing again. Thanks a lot.

KING: God, it gives you goose bumps, doesn't it?

CHAIKIN: Every time. And, you know, I feel like it's taken me my entire adult life to understand what an amazing achievement it was.

KING: Andrew Chaikin - author of the book "A Man On The Moon: The Voyages Of The Apollo Astronauts." Andrew, thanks so much.

(SOUNDBITE OF BRIAN ENO, ROGER ENO, ET. AL.'S "STARS")

KING: And just quickly, something we want to clarify - on Monday, we aired a story from Susan Stamberg about an exhibit centered on the sculptor Augusta Savage. We said Wendy Ikemoto curated the show. Ikemoto is associate curator of American art at the New York Historical Society Museum and Library, and she coordinated the "Augusta Savage: Renaissance Woman" show in New York. But it was originally curated by Jeffreen Hayes for the Cummer Museum of Arts and Gardens in Jacksonville, Fla. Transcript provided by NPR, Copyright NPR.


Key Moments To The Lead-Up Of Apollo 11 Moon Landing

NPR's Noel King talks to historian Andrew Chaikin about the things that went wrong during the Apollo 11 moon landing. He wrote: Man on the Moon: The Voyages of the Apollo Astronauts.

Neil Armstrong took his first small step for man on the moon 50 years ago tomorrow. And when he did it, he walked on into the history books. Andrew Chaikin is with me now. He wrote the book "A Man On The Moon: The Voyages Of The Apollo Astronauts." Good morning.

ANDREW CHAIKIN: Good morning.

KING: So how did the landing play out?

CHAIKIN: Well, landing on the moon is basically a controlled fall out of orbit.

CHAIKIN: And you only have enough fuel for one try.

(SOUNDBITE OF ARCHIVED RECORDING)

CHARLIE DUKE: Eagle, Houston. You are go to continue powered descent. You are go to continue powered descent.

CHAIKIN: The onboard computer, which was absolutely primitive by today's standards, had had about 37,000 words of memory, although those were very.

CHAIKIN: . Well-chosen words. But the computer was critical. It was absolutely the third crew member in that lander. And everything pretty much went OK until about five minutes into the final descent to the moon.

(SOUNDBITE OF ARCHIVED RECORDING)

BUZZ ALDRIN: Got the Earth right out our front window.

CHAIKIN: . When, all of a sudden.

(SOUNDBITE OF ARCHIVED RECORDING)

NEIL ARMSTRONG: Program alarm.

CHAIKIN: . Something was wrong with the computer.

(SOUNDBITE OF ARCHIVED RECORDING)

ARMSTRONG: Give us a reading on the 1202 program alarm.

CHAIKIN: Some of the people who were really caught up short by these alarms were the people who had actually written the software for the computer, and they were at MIT in Cambridge, Mass. And one of the main authors of that software was a young computer engineer named Don Eyles.

(SOUNDBITE OF ARCHIVED RECORDING)

DON EYLES: We looked at each other with sort of blank faces. Something was going on in the computer that we didn't understand. If it had been up to me, I would have called an abort.

KING: That is absolutely terrifying. So why did they not abort?

CHAIKIN: Well, one of the heroes here is the flight director, Gene Kranz. Couple of weeks before the mission, they had done a simulation in which computer alarms had come up, and they had not been ready for them. Kranz said to his computer guys, I want you guys to be prepared for every conceivable computer alarm that might come up. So when these alarms came up, there was one guy in a back room. He was only 24 years old. His name was Jack Garman.

(SOUNDBITE OF ARCHIVED RECORDING)

JACK GARMAN: It's executive overflow. If it does not occur again, we're fine. It's continuous that makes it no-go. If it reoccurs, we're fine.

KING: He's so calm. We're fine. We're fine.

CHAIKIN: It's absolutely amazing to hear him. (Laughter) It's just one of these stunning examples of the amazing performance of these young people who were given awesome responsibility during these missions.

(SOUNDBITE OF ARCHIVED RECORDING)

DUKE: You're looking great to us, Eagle.

CHAIKIN: So they're still about 3,500 feet above the moon when Gene Kranz pulls his flight controllers and then finally gives them the go-ahead to continue the landing.

(SOUNDBITE OF ARCHIVED RECORDING)

GENE KRANZ: OK. All flight controllers, go, no-go for landing. Retro.

KRANZ: Capcom, we're go for landing.

DUKE: Eagle, Houston, you are go for landing, over.

ALDRIN: Roger, understand, go for landing.

CHAIKIN: And then after that, there were more alarms on the computer.

(SOUNDBITE OF ARCHIVED RECORDING)

DUKE: Roger, 1201 alarm. We're a go. Same type. We're a go.

EYLES: We had four more of those alarms before we actually got to the surface. And at one point, the display went blank for a period of about 10 seconds. Armstrong laughed about it afterwards.

KING: I guess if you're going to have a - if you're going to have to go through that, have a sense of humor, right?

CHAIKIN: Oh, you know, this is exactly what Armstrong had signed up for. But by the time that Armstrong actually got to look out the window and see where the computer was taking them, he saw they were headed for a crater the size of a football stadium. And it was completely surrounded by boulders, which were themselves the size of small cars.

(SOUNDBITE OF ARCHIVED RECORDING)

ARMSTRONG: Pretty rocky area.

CHAIKIN: So he took over semi-manual control to fly past the crater and head on and look for a safer spot.

(SOUNDBITE OF ARCHIVED RECORDING)

ALDRIN: Altitude-velocity, light.

CHAIKIN: Down in Mission Control, nobody knew about the big crater in the boulders. For Gene Kranz and his controllers, this was getting very, very tense.

(SOUNDBITE OF ARCHIVED RECORDING)

KRANZ: During all of our training exercises, we had normally landed by this time. And from this time on, all we do is give him readouts on fuel remaining.

(SOUNDBITE OF ARCHIVED RECORDING)

CHAIKIN: Armstrong is trying to bring the lander straight down the last hundred feet. And what's happening now is that the lander's engine is blowing dust away in all directions. And it makes it very hard for him to judge his motion over the surface. Armstrong knew that his fuel supply was dwindling, and Kranz knows he and his guys really are not running the show anymore. It's going to be up to Neil Armstrong whether to land or not.

(SOUNDBITE OF ARCHIVED RECORDING)

KRANZ: Now, this is when the - it started to get sort of dicey in the Mission Control Center because we're in to the point where literally many of us have stopped breathing at that time.

(SOUNDBITE OF ARCHIVED RECORDING)

ALDRIN: Forward, forward, 40 feet down, 2 1/2.

CHAIKIN: Thirty feet is the altitude above the surface. Two and a half down means that they're descending at a rate of 2 1/2 feet per second.

(SOUNDBITE OF ARCHIVED RECORDING)

ALDRIN: Kicking up some dust, 30 feet, 2 1/2 down, faint shadow. Four forward.

CHAIKIN: Four forward is the velocity over the surface, the forward velocity of four feet per second.

(SOUNDBITE OF ARCHIVED RECORDING)

ALDRIN: Four forward - drifting to the right a little, down a half.

CHAIKIN: Thirty seconds means they have 30 seconds left before they either have to abort or go ahead and land with the fuel they have remaining.

(SOUNDBITE OF ARCHIVED RECORDING)

ALDRIN: Down a half. Contact light. OK. Engine stop. ACA - out of detent.

ALDRIN: Mode control - both auto. Descent engine command override - off. Engine arm - off. Four hundred thirteen is in.

DUKE: We copy you down, Eagle.

ARMSTRONG: Houston, Tranquility base here. The Eagle has landed.

DUKE: Roger, Tranquility. We copy you on the ground. You got a bunch guys about to turn blue. We're breathing again. Thanks a lot.

KING: God, it gives you goose bumps, doesn't it?

CHAIKIN: Every time. And, you know, I feel like it's taken me my entire adult life to understand what an amazing achievement it was.

KING: Andrew Chaikin - author of the book "A Man On The Moon: The Voyages Of The Apollo Astronauts." Andrew, thanks so much.

(SOUNDBITE OF BRIAN ENO, ROGER ENO, ET. AL.'S "STARS")

KING: And just quickly, something we want to clarify - on Monday, we aired a story from Susan Stamberg about an exhibit centered on the sculptor Augusta Savage. We said Wendy Ikemoto curated the show. Ikemoto is associate curator of American art at the New York Historical Society Museum and Library, and she coordinated the "Augusta Savage: Renaissance Woman" show in New York. But it was originally curated by Jeffreen Hayes for the Cummer Museum of Arts and Gardens in Jacksonville, Fla.

Copyright © 2019 NPR. All rights reserved. Visit our website terms of use and permissions pages at www.npr.org for further information.

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More on the Moon landing

The simple reason is that it had never been done before - and it was a big ambition for countries, and their space programmes, to be the first to land a human on the Moon's surface.

In the run-up to the Moon landing, the US was competing with the Soviet Union in something called the space race. This was a competition between them to be the first to complete missions exploring the world outside the Earth's atmosphere.

This race started when the Soviets - the US's enemy during the Cold War - launched the first Soviet Sputnik satellite in 1957.

Then, Soviet cosmonaut Yuri Gagarin became the first human in space on 12 April 1961.

The Americans wanted technological superiority - and it looked like the Soviets were winning in the space race.

So, in 1962, US President John F Kennedy announced a big ambition, in a speech which is now very famous.

"We choose to go to the Moon!" he said.

US space agency Nasa invested lots of money (around $25 billion, which is around £20 billion) and effort into making this happen. The mission would come to be known as the Apollo programme and its goal was to land humans on the Moon and bring them safely back to Earth.

About 400,000 people worked on it.


Apollo 11's Infamous Landing Error Code 1202 Offers Earthly Lessons For Self-Driving Cars

Astronaut Edwin E. "Buzz" Aldrin Jr. photographed during Apollo 11 Extravehicular Activity on the . [+] Moon.

The 50th anniversary of the historic Apollo 11 landing on the moon takes place on July 20, 2019.

You might recall the famous utterance heard worldwide that the Eagle had landed (the word “Eagle” was the name given to the lunar module aka lunar lander used in the Apollo 11 mission).

Going back in time to that incredible feat that occurred five decades ago, listen carefully to the recorded audio chatter between astronauts Neil Armstrong and Buzz Aldrin while carrying on a dialogue with the mission control center during the descent to the moon.

Unless you are a nerdish fan of computers or spaceflight, you might not have noticed that there was a subtle undercurrent of concern about some rather jarring, alarm-blaring, display-flashing error codes known as the numbers 1202 and 1201.

It’s an incredible story that the general public knows little about.

Let’s unpack the tense tale, along with considering lessons learned that can be applied to the now emerging self-driving driverless autonomous cars.

Anxious Moments During The First Landing On The Moon

The lunar module that was being piloted down to the moon surface began to report errors when the craft was just seven and a half minutes away from landing.

Think about this for a moment. I assure you that having errors crop-up while in the midst of such an already tricky and risky effort is not something you desire to occur. It was later indicated that the heart rates for both the astronauts jumped up feverishly when the errors began to appear.

Things were tense, especially since landing on the moon had never actually occurred before and had only been practiced in a simulator.

The astronauts were faced with the possibility that they might need to call off the landing if something went awry during the descent. If they didn’t land on the first try, there was no second try available and they’d have to sheepishly and disappointingly return to earth without having landed on the moon.

It would have been a crushing blow to NASA, it would have been a heart-wrenching let-down for the country, it would have potentially tarnished the image of America worldwide, along with creating an expanded window for the Russians to try and get to a moon landing before the United States did.

Everything was on the line.

Of course, worse still would have been a crash landing onto the moon, which one shudders to even contemplate.

Two obscure error codes were involved, each consisting of four digits, and represented status that there was an issue or problem occurring in their spacecraft. During the design of the system for the lunar lander, the developers had come up with a slew of error codes that could be displayed if the computer detected something amiss on the craft.

Here’s the rub. When the astronauts had done simulated landings, doing so over and over again, not all of the possible error codes were tested out, and thus there were some error codes that the astronauts had never seen or directly knew about.

As luck or unluck would have it, the two error codes of 1202 and 1201 had not been previously exhibited during their training efforts. As such, the astronauts were unaware of what those particular error codes signified. Furthermore, even most of the mission control staff monitoring the landing had not seen the 1202 and 1201 before either.

Okay, let’s try to relive history.

Put yourself into the cramped lunar module. With just minutes left to land, bells start ringing and buttons are flashing, trying to get your rapt attention. Nearly immediately, the astronauts realized they didn’t know what the error code signified, and so they (remarkedly) calmly brought it to the attention of mission control:

Within mission control, there were blank stares as by-and-large no one knew what the 1202 was about. Meanwhile, Steve Bales, a guidance officer, called over to a backroom area where various engineers were stationed and ready to dig into any system related matter that might arise.

“1202. What’s that?” he reportedly asked.

John “Jack” Garman, a NASA engineer, took a look at a list he had handmade of the numerous error codes that the teams had come up with.

He realized that the 1202 was a code meaning that the guidance computer on-board the landing craft was getting overloaded with tasks. The programmers had anticipated this overloading might someday occur, and so had established a system internal aspect that would automatically do a fast reboot and then a memory restore to try and get the computer back underway.

In theory, the computer was going to be able to resolve the error, without needing any human intervention. Garman said afterward that he figured if the 1202 error code didn’t recur frequently during the rest of the descent, the astronauts were probably okay to proceed in spite of whatever was seemingly overloading the onboard computer system.

“Give us a reading on the 1202 program alarm,” Neil said.

In the recorded voice transmissions, you can hear in Neil’s voice a seriousness and sternness and exasperation that so far no one from mission control had yet told the astronauts what to do about the error.

Again, place yourself in the lunar module and imagine that you’ve got this crazy unknown 1202 error code screaming at you, you’ve never seen it before, you don’t have any procedure in-hand to deal with it, and it could be something extremely dangerous, happening in real-time, while you are aiming to hopefully safely land on the moon, and you are completely in-the-dark as to what it is and what you are supposed to be doing about it.

Each second that the 1202 remains an unknown could be another second toward your doom.

Within mission control, Darmon and Bales relayed internally that the astronauts should proceed on the landing, and so capcom Charlie Duke said to the astronauts:

In this context, “go” means that the landing could continue to proceed unabated. Also, since no further instruction of what to do was being voiced to the astronauts, it implied that the alarm, whatever it meant, could be ignored. If you are wondering whether the astronauts might have been curious about what the 1202 represented, I believe they only cared at the moment about whether the 1202 required any action on their part.

I was fortunate to have had lunch with Buzz Aldrin during a recent visit he made to Los Angeles, and when I asked him about the 1202, he indicated indeed that once mission control essentially said to not worry about it, he let it go and didn’t put any further thought towards it.

This makes sense too, namely that no additional explanation or elaboration was particularly needed per se, plus the astronauts already had their hands full with trying to land, so they set aside worries about the 1202 and focused on the landing process.

If you listen to the remaining minutes of the recorded audio, you’ll hear that the 1202 error happened again, and again, along with a related error code of the 1201. Mission control informed the astronauts that it was considered the same type of error and implied therefore that there was no need to do anything about the alarms.

For everyone listening at the time of the actual moon landing, the chatter seemed to be the normal kind of interaction you’d expect between the astronauts and mission control, often technical in nature and you don’t really know what their jargon means or signifies.

In this case, it was a subplot of grave concern and intensity, but that millions upon millions of people listening were unaware was playing out in real-time and could have ditched the landing entirely.

That’s the story within the story about the Apollo 11 moon landing.

Lessons Learned For Self-Driving Driverless Cars

Can a systems related matter that happened some fifty years ago be of relevance today?

Self-driving driverless cars are real-time based systems that need to act quickly and drive a car while the vehicle is in motion, perhaps on a freeway and barreling along at 70 miles per hour.

Onboard the autonomous car are numerous computer processors, including various electronic memory banks used to house programs that are being executed or performed to drive the car. In addition, there is a myriad of sensors on the car, such as cameras, radar, ultrasonic devices, LIDAR, and the like, all of which are collecting data during the driving act and relaying that data into the computer processors and memory banks.

In the case of the 1202 error on the Eagle, what prompted the error was (in simple terms) a faulty radar unit that was essentially bombarding the onboard computer in such a manner that the computer kept getting handed task after task, though the flooding tasks weren’t truly needed to be undertaken. The Operating System (OS) of the computer allowed the memory to fill-up, but then this meant that other legitimate tasks would not have a slot to work in.

As I had mentioned earlier, the programmers had anticipated that somehow for whatever reason there might be a time when the onboard computer might become overloaded with tasks. They had devised an internal mechanism that if something untoward led to the memory getting maxed out, the system would do a fast reboot and memory reload, which hopefully would clear out whatever was causing the initial problem.

Though this does suggest that the computer can then proceed with the high priority of running the craft, notice that it does not necessarily solve the underlying problem of the radar unit that’s pounding away at the computer. In any case, the good news is that the trick of the quick reboot was able to deal with the matter and the other precious landing subsystems were able to do their thing, meanwhile the radar was continuing to be an irritant but not so much that it led the craft astray.

How many times have you rebooted your smartphone or laptop computer and then had it clear up a problem?

I’m betting you’ve done such reboots many times.

Have you also perchance done a reboot and then later on the same problem seemed to crop-up?

That’s a somewhat similar case of the 1202, namely that the reboot temporarily “solves” the problem of letting the computer proceed, but it didn’t “solve” the root cause of the faulty radar unit aspects.

Here then are some insightful Apollo 11 lessons for AI developers, automakers, and tech firms that are creating the software and systems for driverless cars:

Anticipate and code for wayward sensors. You cannot assume that the sensors on the driverless car will be working flawlessly. Besides the obvious aspect that the sensor might get blinded by dirt or debris, there is also the chance that the sensor could go awry due to some internal bug or issue. Make sure to code for this possibility and have some provision of what to do once the matter arises.

Ensure that the driverless car OS is robust. Some of the operating systems being used for autonomous cars are somewhat stripped down for speed, yet they need to also be able to handle a wide variety of both known and unpredictable faults or systems issues that could happen. Make sure the OS is up to the task of supporting the systems involved in driving the car, safely so.

Do not ignore edge cases. The focus for most driverless car efforts right now is aiming at driving during normal everyday conditions, and not dealing with unusual or infrequent kinds of driving situations (so-called “edge” aspects). This though belies the true aspects of driving which can include foul weather, bad roadways, and the like. Autonomous cars that are being tried out on our public streets need to be ready to handle edge or corner cases.

Testing must be exhaustive. If you leave out test cases when testing a driverless car, you are setting up a potentially dangerous situation that someday in the real-world the thing you didn’t test will happen, and perhaps have quite adverse consequences. Testing needs to be as complete as feasible.

Use reboots cautiously and only as a last resort. Imagine you are in a driverless car, zipping along on the highway, and the AI announces that it needs to do a reboot, right away. This is not the same as doing a reboot on your smartphone when you are playing a video game that froze-up the phone. Developers should consider an on-board reboot as a last resort and only invoked with great caution.

You’ll be happy to know that the amount of computer capability packed into a self-driving car is many magnitudes greater than the puny but valiant computers used on the Apollo 11 spacecraft.

Those programmers in 1969 could only dream of someday having access to the incredibly powerful computing that we commonly have available today. Even your smartphone is by far superior in computer power than were the lunar lander computers.

That’s though just the hardware side of things.

From a software perspective, we still today can readily have the same kinds of issues occur, including hidden bugs or suddenly appearing faults, which could have happened back in 1969. Let’s make sure that we learn the lessons of the past and therefore are extremely mindful when designing, coding, testing, and fielding autonomous cars.

Thanks go to NASA and all those involved in getting us to the moon, and hopefully, today’s driverless cars will be prepared for any 1202 or 1201 codes that might pop-up.


Quick facts about the 1969 Moon landing:

1. NASA&rsquos Apollo 11 crew blasted off from Earth on July 16, 1969, from Cape Canaveral, Florida.

2. The Apollo 11 spacecraft took three days to reach the lunar orb.

3. Of the three Apollo 11 astronauts, Command Module pilot Michael Collins was the only one who did not set foot on the Moon.

4. The Apollo crew and to spend 21 days in quarantine after returning to Earth.

5. President Richard Nixon awarded the three men the Presidential Medal of Freedom &ndash the highest civilian award in the US.

Moon landing: A timeline of the 1969 Apollo 11 Moon landing (Image: GETTY)

When is NASA going back to the Moon?

The US space agency has boldly announced in February this year it will renew its focus on permanently returning to the Moon.

NASA administrator Jim Bridenstine told a press conference NASA will go to the Moon &ldquoas soon as possible&rdquo.

The space agency aims to send remote rovers to Mars by 2024, followed by manned crews in 2028.

The NASA chief said: &ldquoIt&rsquos important that we get back to the Moon as soon as possible.

&ldquoThis time when we go to the Moon, we&rsquore actually going to stay.

&ldquoWe&rsquore not going to leave flags and footprints and then come home and not go back for another 50 years.&rdquo


The four Surveyor space probes gathered information about the physical and chemical properties of the lunar soil. Together, they took tens of thousands of photos and helped NASA evaluate the feasibility of a human mission to the moon. Surveyor 6 became the first spacecraft to launch from the surface of the moon, after it lifted off and flew a short distance to another landing site.

These missions set the stage for NASA’s Apollo program.

The program’s first four flights—Apollo 7, 8, 9 and 10—tested equipment for a future moon landing.

On July 16, 1969, at 9:32 a.m. ET, Apollo 11 lifted off on a Saturn V rocket from Cape Canaveral, Florida. Less than three hours later, another rocket burn put astronauts Neil Armstrong, Buzz Aldrin and Michael Collins on course for the moon, in a maneuver known as the “translunar injection.”

Next, the astronauts executed a tricky maneuver to retrieve the stored lunar module that would take Armstrong and Aldrin down to the moon’s surface. The so-called command service module, where the astronauts were staying, detached from the remaining rocket stage and turned 180 degrees.

It then docked with the lunar module, pulling it out of the section of the rocket where it was stored for launch.

Apollo 11 was now ready for a lunar rendezvous.

The astronauts traveled through the cosmos for the next three days.

As Apollo 11 entered orbit around the moon, the astronauts prepared for the next crucial stage of the mission.

Armstrong and Aldrin climbed into the lunar module, named Eagle. Collins stayed in the command module. The two spacecraft separated and the Eagle began its descent to the moon.

The lunar module overshot its landing site by 4 miles, and with only 30 seconds of fuel left, Armstrong piloted the spacecraft to a safe touchdown.


The most important moments that happened during the 8-day Apollo 11 mission

HOUSTON – The Apollo 11 moon landing occurred almost 50 years ago. In honor of the 50th anniversary celebration of Apollo 11 below is a timeline as told by NASA with the most important highlights during the eight-day mission.

July 16, 1969

This was the Apollo 11 launch date out of Cape Kennedy in Florida. The launch sent Commander Neil Armstrong, Command Module Pilot Michael Collins and Lunar Module Pilot Edwin “Buzz” Aldrin into an initial Earth orbit of 114 by 116 miles. Around 650 million people watched Armstrong’s televised image during the launch.

Additionally, the first color TV transmission occurred from Earth to Apollo 11 during the translunar coast of the command and service module/lunar module.

July 17, 1969

A three-second burn of the service propulsion system was made to undergo the second of four scheduled midcourse corrections programmed for the flight. This turned out to be highly successful and the others were no longer needed.

July 18, 1969

Armstrong and Aldrin put on their spacesuits and went to see the lunar module and made the second TV transmission by climbing through the docking tunnel from Columbia to Eagle.

July 19, 1969

At this point in the mission, Apollo 11 had flown behind the moon and out of contact with Earth. At around 75 hours, 50 minutes into the flight, a retrograde firing of the SPS for 357.5 seconds put the spacecraft into an initial, elliptical-lunar orbit of 69 by 190 miles. The second burn that followed later for 17 seconds placed the docked vehicles into a lunar orbit of 62 by 70.5 miles. This calculated to change the orbit of the command and service module, piloted by Collins. The change happened due to lunar-gravity disruptions to the normal 69 miles required. Another TV transmission was made from the service of the moon before the second service propulsion system firing.

July 20, 1969

Armstrong and Aldrin both entered the lunar module again. When the lunar module was behind the moon on its 13th orbit at 101 hours and 36 minutes, the lunar module descent engine fired for 30 seconds to provide both retrograde thrust and commence descent orbit insertion. This changed the orbit to nine by 67 miles, which was following the same trajectory as Apollo 10. Then following when Colombia and Eagle had reappeared from behind the moon, the lunar module was around 300 miles uprange and this made a powered descent with the descent engine firing for 756.3 seconds. After eight minutes, the lunar module was considered at “high” gate and 26,000 feet above the service and around five miles from the landing slide-

The descent engine provided braking thrust until about 102 hours and 45 minutes into the mission. Partially and manually piloted by Armstrong, the Eagle landed in the Sea of Tranquility in Site 2. This happened one-and-a-half minutes earlier than scheduled and also four miles downrange from the touchdown point predicted.

After a four-hour rest period, the activity began and Armstrong emerged from the Eagle and deployed the TV camera for transmission of this event to Earth. At 109 hours and 42 minutes after launch, Armstrong stepped on the moon. 20 minutes later, Aldrin followed him. After about 30 minutes they both spoke with President Richard Nixon through a telephone link.

During their time on the moon, they were both around 300 feet from the Eagle and gathered and reported on lunar samples. After Aldrin spent around one hour and 33 minutes on the surface, he re-entered the lunar module. Armstrong followed around 41 minutes later. All extravehicular activity lasted two-and-a-half hours.

Both Armstrong and Aldrin spent 21 hours and 36 minutes on the moon’s service. Following a rest stage that included seven hours of sleep, the ascent stage engine fired at 124 hours and 22 minutes.

July 21, 1969

This was when the trans-earth injection of the command and service module began as the service propulsion system fired for two-and-a-half minutes when Columbia was behind the moon in its 59th hour of lunar orbit. The astronauts then slept for 10 hours.

July 22, 1969

During the trans-Earth coast, two more television transmissions were made.



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