Apollo 11 Landing: Why Astronauts Were Almost Trapped on The Moon Forever?

Just outside the front window of the spacecraft, suspended in the black, hung the jewel-like blue-green marble of the Earth. The view was beautiful, amazing, awe inspiring; but mission commander Neil Armstrong didn’t have time to enjoy the view
Apollo 11

What Happened During the Apollo II Moon Landing?

Just outside the front window of the spacecraft, suspended in the black, hung the jewel-like blue-green marble of the Earth. The view was beautiful, amazing, awe inspiring; but mission commander Neil Armstrong didn’t have time to enjoy the view- he was sharply focused on landing the Apollo 11 lunar module, the Eagle, on the moon. There were no second chances, they’d either land, crash or abort the lunar landing. The Eagle was only 30,000 feet and rapidly descending towards the surface of the moon when suddenly a master alarm rang and the onboard navigational computer flashed error code 1202…

Apollo 11 Launch Date

On July 16, 1969, Apollo II launched from Cape Kennedy, Florida carrying 3 astronauts: Commander Neil Armstrong, Command Module Pilot Michael Collins and Lunar Module Pilot Edwin “Buzz” Aldrin on a mission to the moon. Once Apollo 11 reached the moon and entered lunar orbit, the Lunar Module, named the Eagle, undocked from the Command and Service modules which formed the Columbia. The spacecraft then made a carefully controlled descent to land on the moon.

rocket launch

Historic Apollo 11 Moon Landing

After the Eagle touched down at 20:17 UTC on July 20, 1969, 650 million people worldwide watched the footage in awe as Commander Armstrong took humanity’s first step on the moon. The moon landing has become the stuff of legend, immortalized in photographs and movies. To many it seemed like the trip to the moon was an amazing success, carried out by brave astronauts with ease. However, behind the scenes mission control in Houston and the astronaut crew had to troubleshoot various hazards in real time throughout the historic mission. 


7 different ways the astronauts of the Apollo 11 mission almost didn’t make it home.

Number 1:  Because of a computer error

 Imagine being crammed into a tiny spacecraft, with only 160 cubic feet of livable space, 7 and a half minutes from the surface of the moon and your navigational computer throws up an unknown error code? That’s exactly what happened. Armstrong was preparing to land the Eagle on the moon when the Apollo Guidance Computer, the “AGC” suddenly displayed error code 1202. 

The AGC was a technological marvel for its time. It was fairly compact, weighing only 70.1 pounds (31.79683 kg) and requiring 70 watts at 28 volts DC. The computer was central to the mission, especially landing. Among other tasks it managed navigation, velocity, altitude, and engine performance data. It also constantly adjusted the abort trajectory, prepared to shoot the crew back into orbit should something force an abort.

Neither Armstrong nor his co-astronaut Aldrin knew what error code 1202 was. He had never even seen it during the many simulated moon landings he had done during training. Armstrong alerted Houston and they told him to ignore the error and proceed with the mission. The computer system ended up triggering error code 1202 a nerve wracking four times and 1201 once. As it turns out, the computer was being overloaded with too many commands from a radar system and was running out of memory.


Number 2: They Missed  the Chosen Landing site

Around the same time that the navigational computer was flashing overload error codes, the astronauts had another serious problem on their hands. About 9 minutes before the Eagle was set to touchdown on the surface of the moon, Armstrong realized that they were going to overshoot their carefully chosen landing site. He estimated they’d miss by approximately 3 miles (4.82 km)–which was a good guess, they actually missed by it by 4 (6.43 km).

When the Eagle undocked from the Columbia, unvented residual pressure inside the tunnel that connected the two spacecrafts gave the Eagle an additional boost as it separated. Though slight, the extra push put the Eagle out of range of the desired landing site. The moon is covered with craters and rocks and the planned landing site was relatively smooth. Worse yet, the lunar module was burning fuel quicker than expected. Soon Houston alerted the Eagle that they only had 60 seconds of fuel left before they would have to abort the mission.

The spacecraft careened,  skimming over the lunar terrain at 34/mph (55/km). The descent engine kicked up dust from the surface, making it hard to see. With less than 30 seconds of fuel left in the tank, Armstrong landed the Eagle onto a fairly smooth looking area. The blue ‘Contact Light’ on the console came on. Then Armstrong said the phrase that has now been committed to history: “Houston, Tranquility Base here…the Eagle has landed.”


Number 3: Pressure Buildup

Not long after the Eagle landed on the moon, another problem began to develop. Though the landing engine fuel line had been shut down, sensors were detecting a pressure build-up. This meant that ice had plugged the descent-fuel helium heat exchanger and there was some fuel vapor caught in the line between the exchanger and the valves. The vapor was being heated by the Eagle’s hot engine, building pressure which could cause an explosion.

NASA rapidly drew up plans to vent the system. However before Houston could relay instructions to Armstrong and Aldrin, the ice plug thawed and the gas dispersed on its own, remedying the problem.

space exploration

Number 4: Unknown Lunar Surface

Another hazard that could have prevented the astronauts from successfully completing their mission to the moon and returning home was simply an unknown. NASA didn’t know how stable the surface of the moon was. The Eagle being able to land firmly on Tranquility Bay was a good sign, however did a thin layer of moon dust cover jagged shards of rock that could cause injury to the lander or astronauts?


Although the Surveyor landers and other previous robotic missions had studied the lunar surface, it wasn’t until Armstrong’s iconic footstep into the grey moon dust that NASA was sure the surface would support EVA or extravehicular activity.

As it turns out, lunar dust is dangerous, mainly due to its abrasiveness. Lunar dust has been created over billions of years by meteorite impacts, however the moon lacks processes that would grind down these tiny particles into smoother shapes. 

Astronauts from various missions report tiny shards of rock permeating lunar module interiors, jamming zippers and even penetrating layers of protective spacesuit material. Lunar dust travels ballistically because there’s no atmosphere on the moon, and it will stick to anything.


Number 5: Broken Switch

 A broken switch almost trapped the astronauts on the moon. No one knows exactly how the switch broke, but Aldrin is fairly certain that it happened after he and Armstrong reentered the Eagle following their 2.5 hour walk on the moon. The flight plan instructed the astronauts to seal the lunar module’s hatch, repressurize the cabin, disconnect their backpacks and connect their spacesuit hoses to the spacecraft’s life support systems. 

After that, they would vent the cabin once more, open up the hatch and throw the backpacks and other unneeded equipment onto the moon’s surface, thereby reducing the weight of the craft for liftoff.

Though Armstrong and Aldrin had practiced the routine many times during training, somehow during execution one of them banged something or stumbled against Aldrin’s side of the instrument panel, snapping off a small switch. 


Settling on the floor to rest, Aldrin happened to notice a little black switch lying in the lunar dust which had permeated the cabin. To their dismay, the astronauts realized that the broken piece was the small circuit breaker arm that controlled the power running to the ascent engine. If it was broken off, it couldn’t be pressed in on the console to complete the circuit, the ascent engine wouldn’t be able to power up, and the Eagle couldn’t blast off the moon. 

The astronauts alerted Houston to the problem. While the astronauts tried to nap, NASA engineers scrambled to find a workaround that would reroute power to the engine without the switch. Unfortunately after several hours, they still hadn’t found a solution.

The broken end of the switch was still visible, deep inside its small hole on the console. Sadly, it was too small a hole for a finger. However, Aldrin was able to use a felt tipped pen to depress the circuit breaker and close the circuit, allowing the ascent engine to power up. Basically, Aldrin pulled a McGuyver move to help get the Eagle back to Columbia. 


Number 6: Command Module Almost burned down

The command module carrying the astronauts back to earth was almost hit by burning, disintegrating chucks of the service module during re-entry to the earth’s atmosphere. 

To return to Earth, the flight plan was that the Columbia would separate into two parts: the astronauts would stay inside the Command Module while the Service Module was jettisoned. Once safely away, the Command Module would position itself so that the heat shield was facing towards Earth’s atmosphere.

As the command module descended to the lower atmosphere, the parachute would deploy, slowing the spacecraft and leading to a splash down in the Pacific Ocean approximately 5 minutes later. Meanwhile, the Service Module would break apart and burn up while entering Earth’s atmosphere.


To prevent any debris from the Service Module accidently colliding with the Command Module and injuring or even killing the astronauts, the Service Module was supposed to perform a series of thrust maneuvers to move it away from the re-entry path of the Command Module. In fact, by shifting the Service Module to a significantly different trajectory, its orbit would change and  it wouldn’t even re-enter the Earth’s atmosphere at the same time as the Command Module.

However, the thrust maneuvers of the Service Module failed and both modules from the Apollo 11 Mission followed the same re-entry trajectory. Luckily no debris from the disintegrating Service Module hit the Command Module and the astronauts were able to splash down safely. Later it was realized that there was an error in how the Service Module was configured to jettison its remaining fuel.

Apollo 11 Landing: Why Astronauts Were Almost Trapped on The Moon Forever? 5

Number 7: Possibility of Alien Infection

A final issue that may have prevented the astronauts returning home was the possibility of alien infections. In 1969, only a few robotic landers had been to the moon. Their studies confirmed that the moon surface was rocky, dusty, covered in craters and devoid of complex life forms. However, NASA still took precautions in case the astronauts were possibly exposed to and infected by alien microbes. 


After the Command Module successfully splashed down in the Pacific Ocean on July 24th, 1969,  the U.S.S. Hornet recovered astronauts Neil Armstrong, Michael Collins, and Buzz Aldrin. They were immediately placed in a Mobile Quarantine Facility and transported to the NASA Lunar Receiving Laboratory at the Johnson Space Center. There, the astronauts were moved to a larger quarantine facility. After determining that the astronauts hadn’t been infected by any nasty space germs, they were released on August 10, 1969, just shy of 3 weeks after they had returned to earth.

In 1996, some 30 years after the Apollo 11 mission, a draft of the speech President Richard Nixon would have given to the nation in the event of mission failure was released. Considering all of the issues that went wrong and all the issues that could have gone wrong during Apollo 11, it’s amazing that the mission was successful and the astronauts made it home. To quote the beautiful yet poignant speech that President Nixon never had to give:

“In ancient days, men looked at the 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.”

What do you think was the scariest aspect of the Apollo 11 mission? Let us know in the comments. Also see more

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