Military Technology

The hall of Xinyuehu Aerospace Command and Control Center in Haoyu Science and Technology Park is now brightly lit, and everyone is in their places, waiting for the important moment to arrive. On the big screen in front of the hall, there is a 3D model image of the moon. On the slowly rotating moon, there is a circle of green lines. The end of the green line shows a strange-looking aircraft. This is exactly For the lander of the Lunar Cargo 2 spacecraft, which was launched five days ago, these green lines are exactly the trajectory of its previous flight around the moon.

In front of the lander are these circles of red lines, which are the routes the lander is expected to travel. At the end of the red line, there is a flashing dot. This is the final landing point of the Zhesu lander, the aircraft landing site of the Zhihai Lunar Surface Scientific Research Station.

In fact, many people have confused a concept. In everyone's impression, it seems that the moon does not rotate, because in our impression, the moon always faces the earth, and the back side can never be seen, so we think that the moon does not rotate. It will rotate on its own.

In fact, the moon rotates, but its rotation period is relatively long. Because "because of the "tidal locking" effect, the moon rotates while orbiting the earth for 27 days, 7 hours, 43 minutes and 11.47 seconds. Therefore, the moon we see on the earth is always the front side of it. His backside cannot be seen.

Ten hours ago, the lander successfully separated from the orbiter and is now gradually descending to the altitude of the lunar orbit in preparation for landing.

Therefore, today's landing process also attracted a lot of attention. The guest auditorium in the command and control hall was also filled with many reporters and invited guests.

Wu Hao and others also came to the scene and accompanied several important guests to witness the entire landing process with their own eyes.

In fact, in addition to some experts and professors, these guests also included some leaders, including local leaders from Anxi and provincial leaders who came to watch the entire launch process.

After all, this can be regarded as a grand event in the scientific and aerospace fields of Anxi and even the whole province, so the leaders are also very concerned about it. They have made several phone calls before to inquire about the details and are concerned about the progress of the entire project.

Now at this most critical moment, they came in person, which made Wu Hao and the others very grateful, and they felt the leaders' support and concern for them.

As the general person in charge of the entire project, Yu Chengwu also acted as the host and commentator, personally helping them and introducing some important guests who came this time.

"Xiao Wu, when will we land?" The leader sitting next to Wu Hao looked at the big screen and asked Wu Hao with a smile.

Seeing the leader's inquiry, Wu Hao glanced at the time and replied with a smile: "There are about forty minutes left. Our lander is currently flying around the moon, gradually lowering the orbital altitude, adjusting the orbital angle, and waiting until the entire landing After the vehicle reaches this predetermined height and position, it can implement orbit change and descent.

You see, those red lines on the big screen are its next trajectory. We have to wait until it descends to an altitude of about fifteen kilometers and reaches the sky above the Zhima Basin in the southern hemisphere of the moon. That is the red dot flashing on the screen. position, and then the official landing begins. The entire descent and landing process takes about fourteen minutes. This is also the most dangerous fourteen minutes from rocket launch to final landing. It is related to the success or failure of the entire mission. "

"Fifteen kilometers, is it so low?" This altitude on Earth is almost the same as the altitude of our civil aviation aircraft. Another leader said in surprise.

Hearing the leader's words, Wu Hao smiled and nodded: "Yes, our current international flights of civil airliners are generally around 13,000 to 16,000, and the final orbit may not be as high as the aircraft."

"So low!"

After Wu Hao finished speaking, the leaders next to him all showed surprised expressions. They didn't expect that the altitude of the lunar orbit would be so low.

Seeing this, Wu Hao smiled and explained: "The moon's volume is only one-eighth of the earth, its radius is one-fourth of the earth's, and its weight is only one-eighty-one of the earth's.

Therefore, compared with the earth, it is very small overall and its mass is very light, so its own gravity will be very small, only one-sixth of our earth.

If the gravity on our earth is '1', then the gravity on the moon is only '0.17', which is very small.

In this way, we can convert it. Our earth's Kármán line, which is the dividing line between our earth's atmosphere and space, and also the dividing line of gravity, is one hundred kilometers.

Above this 100 kilometers, you can achieve weightless floating, and below this height, you will feel gravity.

Then convert this height to the moon, 0.17 is 17 kilometers, so we can conclude that the Kármán line on the moon is 17 kilometers.

Of course, this number is not an exact number, it is just a rough value, which may be higher or lower. And due to the lack of atmosphere on the moon and the speed of flying around the moon, the altitude of this landing orbit is lower.

These are all carefully calculated, so there will be no problems. "

Finally, Wu Hao added something, which was a reassurance to the leaders and made them feel at ease.

Sure enough, after hearing Wu Hao's introduction, the leaders couldn't help but nodded, and they had a general understanding of the entire landing process.

"The height of fifteen kilometers should not be too high. Why is it so dangerous?" Another leader who accompanied him immediately raised such a question.

The leaders all laughed at this. Indeed, the altitude of fifteen kilometers on Earth is the flight altitude of international flights, which is still far away from space.

It may also be because of our country's excellent achievements and strong strength in the aerospace field, so in the eyes of the leaders, it seems that there is no difficulty at such a height.

In this regard, Wu Hao was also very helpless, but who let the other party be the leader? He could only explain with a smile: "On our earth, this height is really nothing. Even many extreme skydivers can start from 10,000 Skydive at an altitude of more than 20,000 kilometers and then land safely.

But this is the moon, another planet 380,000 kilometers away from us. Things that are very easy on Earth will be difficult on the moon.

It seems that these fifteen kilometers are very simple, but we have to reduce the lander's flight speed from 1.7 kilometers per second to zero during the landing process of about fourteen minutes.

In other words, during the entire descent process, the engine on the lander must continuously work to slow down the lander. This process is very important.

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