Find out how in this article how Apollo 11 astronauts Neil Armstrong and Buzz Aldrin escaped a shocking crash landing on the Moon.
With lack of fuel, almost zero visibility on landing, and infirm and poorly known landing site: the conditions are just right for a phenomenal crash.
On July 20, 1969, Neil Armstrong and Buzz Aldrin descended to the lunar ground in a frail Lunar Module (LM) with legs, controlled by a miniature computer and a test pilot.
During the thirteenth orbit of Apollo 11 around the Moon, on the morning of July 20, 1969, Houston time (it is already evening in France), Neil Armstrong, commander, and Buzz Aldrin, pilot, say goodbye to Michael Collins.
Dressed in their Apollo 11 spacesuits, they enter the lunar module (LM, Lunar Module, sometimes LEM, Lunar Exploration Module ), called Eagle.
Michael Collins, left in the control module (Columbia), closes the hatch on his side.
For thirty lunar orbits, he is now alone onboard the spacecraft. No human being before him has been isolated so far from his planet.
He still has a job to do for his colleagues. The Lunar Module is only a few tens of meters away and begins to rotate on itself.
Aldrin takes a photograph of the Columbia control module
Collins must visually inspect the condition of the machine. There is still time to cancel the descent of the lunar module if a problem is detected.
“Be careful, guys! “He said to his two companions after having observed the integrity of the lunar module.
Inside Eagle, Armstrong and Aldrin are standing and wearing a spacesuit with a helmet providing pure oxygen.
They are held by a harness and, under their feet, by Velcro, a beautiful invention that NASA helped popularize.
Aldrin takes a photograph of the Columbia control module.
He is the cameraman, responsible for filming the descent, and Armstrong asks him if the camera is engaged correctly.
Houston gives the order, and Aldrin starts the LM engine.
The space train, whose successive orbits have reduced altitude, is only 14.3 kilometers from the ground.
For 29.8 seconds, the engine moves the Lunar Module away from Columbia. The Eagle enters an elliptical orbit.
For the moment, the Lunar Module is advancing its head forward and, still in this position, begins the descent to the Sea of Tranquility.
Struggling Lunar Module Computer
The crew checked the correct functioning of the small attitude motors for the last time, which gave roll and pitch control.
The settings are looking good. Houston gives the “Go” for the landing maneuver.
At the time, everyone preferred this notable term to the typical “landing.”
However, since it is a question here of plunging back into the reality of the moment, he will be temporarily resurrected.
When the radar altimeter reads 12 kilometers above sea level, Eagle has turned to stand on the ground.
The onboard computer, which receives the altimeter data, now controls the descent.
Charles Duke, CapCom In Houston
With the power of a calculator from the 2000s – low end – it is a little painful.
The LGC (LEM guidance computer) has a read-only memory of 36,864 words (15 bits, 16 minus one for control) and a random access memory (Ram) of 2,048 words.
The ground is now very close. At 1,200 meters, Charles Duke, CapCom in the center of Houston (it is he who is speaking live with the crew), announces “Go for landing,” in other words, the conditions are right, and the moon landing is authorized.
The Lunar Module (LM) is then a few seconds ahead of the planned trajectory and will, therefore, land at the end of the ellipse scheduled for the moon landing.
Buzz Aldrin Indicates “Alarm 1201 “
At the same time as announcing less than 500 meters (1,600 feet), Aldrin indicates “alarm 1201 “.
The computer is full. “Alarm 1201. We are Go,” replies Charles Duke, in the jargon of astronautics, directly from that of aeronautics.
Clearly: “we continue. ” Faced with the error, the computer automatically “reboots,” according to the expression nowadays used, and starts by offloading part of the data. Alarm 1201 is still there. “We are Go” repeats Houston.
Neil Armstrong Looks Outside The LM
“Four hundred thirty meters above sea level.” While Buzz Aldrin is plunged into monitoring the control screens, Neil Armstrong looks outside and notices that the device is heading straight towards a crater a hundred meters in diameter.
The Lunar Module must land on a relatively flat surface. If the incline is too steep, it may tip over.
Even if the craft remains on its feet, it will not be able to take off if the gradient exceeds 2%.
Lunar Module Passes The Danger Zone
“Two hundred thirty meters above sea level.”
Armstrong switches to manual piloting and gives a little gas to pass the crater. Sixty seconds of fuel remains.
The Lunar Module passes the danger zone by about 350 meters and approaches the ground.
A cloud of dust envelops Eagle. Armstrong no longer sees anything.
Aldrin follows the altitude, which is now counted in feet, and the vertical speed, in feet per second (it is then about 0.75 m / s and decreases).
There is only thirty seconds of fuel left in the tank.
The Lunar Module Has Just Detected The Ground
A lamp lights up. The three contractors under the feet of the Lunar Module have just detected the ground.
The engine is stopped. It is 3:18 p.m. in Houston and 8:18 p.m. in France.
A nasal path that of Armstrong, distorted by the radio link, announces “here the basis of Tranquility.” Men are on the Moon.
The first occupation of the two astronauts is to check that the Lunar Module is ready to leave.
Then, it is a question of resting a little (the two astronauts have slept very little), but the exiguity of the lunar module, the noises which one hears there, and especially the excitement prohibit sleep.
The astronauts, therefore, undertake to don the lunar walker’s outfit for its first use in real situations.
The first steps on the Moon will take place the next day, July 21, 1969.
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