Thrilling and exciting! Looking back at the first human journey to the moon | Human Lunar Day

54 years ago today, Armstrong left clear footprints on the moon for the first time on behalf of all mankind. To commemorate this great feat, July 20th of each year is designated as "Human Lunar Day".

Behind the glory, there was a series of thrills. What scared the ground personnel so much that they turned pale? What did the astronauts encounter before landing on the moon?

On July 16, 1969, astronauts Armstrong, Aldrin and Collins embarked on the first human journey to the moon. At the beginning, the mission went very smoothly - after the Saturn V rocket entered orbit, the Apollo 11 spacecraft separated from the rocket, arrived at the moon, and flew around the moon. Everything went according to plan. However, just like the plot of a movie, the legendary story is destined to not be smooth sailing. There is always a sharp turn before the climax.

Saturn V rocket launches

On the fifth day of the flight, the command and service module separated from the lunar module, and Apollo 11 was about to land on the moon. Collins stayed in the command and service module and continued to fly around the moon, while his teammates Armstrong and Aldrin would land on the moon in the lunar module.

The three astronauts on the Apollo 11 mission

When the lunar module slowly descended to more than 1,800 meters from the lunar surface, the yellow light on the onboard computer screen suddenly began to flash, indicating the code "1202". The two astronauts and the ground personnel quickly became nervous. There were only 20 seconds left to reach the "death zone", and there was not much time left for decision-making.

First of all, I would like to explain to you that the lunar module of the Apollo spacecraft is divided into an ascending stage and a descending stage. The descending stage is responsible for the soft landing mission and will escort the astronauts to land safely on the moon. The descending stage is also the launch pad for the ascending stage. After the moon landing mission is completed, the ascending stage will be launched from the descending stage, carrying Armstrong and Aldrin from the moon surface back to the lunar orbit, and then docking with the command service module, and the three astronauts will reunite. When a dangerous situation occurs during the moon landing process and it is necessary to abandon the moon landing, the lunar module will use a trick to "escape" - the ascending stage engine will ignite and start, discard the descent stage, and take the astronauts to dock with the command service module in advance and return to Earth.

Eagle lunar module landing on the moon

However, within the last 3 minutes before landing, there are 10 seconds called the "death zone". At that time, the lunar module will descend rapidly. If it uses the "escape" strategy, the fuel tank of the ascent stage will be damaged by the descent momentum, causing the entire module to crash. Therefore, within 20 seconds before entering the "death zone", a decision must be made whether to continue the lunar landing or end the mission early.

Aldrin quickly contacted the ground, and the ground personnel responded that "1202" means "command overflow", which means that the computer can't calculate it, and in order to continue to operate, some commands will be delayed. Based on the situation on the scene, the ground personnel determined that the alarm would not affect the mission and allowed the astronauts to continue landing on the moon. Afterwards, Aldrin reported the "1201" alarm again, and the ground personnel still replied: "Continue to land." Soon, the short and long 10 seconds finally passed, and the lunar module safely flew over the "death zone".

Apollo 11 astronaut Aldrin

Before everyone could breathe a sigh of relief, danger came quietly again. When the lunar module was only 150 meters away from the lunar surface, the astronauts saw from the porthole that the area near the planned landing was full of boulders. If the lunar module hit these rocks, it would be damaged or overturned, and they were forced to obtain "permanent residence on the moon".

With his rich driving experience, Armstrong manually piloted the lunar module to find a flat place to land. At this time, the ground personnel reminded him that the fuel for landing could still burn for 60 seconds. Fortunately, Armstrong quickly found a safe landing site. At 16:17 on the 20th, the Apollo 11 lunar module landed safely: "This is the Sea of ​​Tranquility. The Eagle has landed."

Apollo 11 astronaut Armstrong

The ground crew breathed a sigh of relief as if they were hearing heavenly music, and then all cheered excitedly. A few seconds later, billions of people around the world also learned the good news through television.

At 22:56 on the 20th, Armstrong was the first to open the hatch and step onto the moon. He announced to the world through a live TV broadcast: "This is a small step for an individual, but a giant leap for mankind."