Manned spaceflight is an idea that has been engraved in the bones of Chinese astronauts when Liang Tian was born.

Seriously calculated, this is actually the idea that the Chinese have had since ancient times.

Pangu opens the sky, and Chan'e runs to the moon.

Su Dongpo's sentence "When is the bright moon", in addition to being a beautiful poem, really explores an astronomical question - when was the moon born.

Before Su Dongpo, there was also a famous astronomer named Wang Ximing in the Tang Dynasty.

He is committed to popularizing the knowledge of space through popular songs.

The name of this ballad is "Butian Song", and since its birth, it has undergone dozens of versions of evolution.

To say that it is popular, of course, is to people who are accustomed to ancient texts in that era.

If you continue to push forward, there will be the flying mural of the ladies in the Mogao Grottoes in Dunhuang.

Many people in modern times believe that astronomy is a "foreign subject" that was first studied by Westerners.

In fact, our country has a real history of studying the stars.

Or in the 70s of the 20th century.

In a place called Puyang, an ancient tomb was unearthed.

This ancient tomb is more than 7,000 years old.

Inside the ancient tomb, there are green dragon and white tiger patterns made of mussel shells.

The use of the four signs to represent the stars is a tradition that has existed in Chinese civilization since ancient times.

This ancient tomb is long before the birth of Chinese culture for 5,000 years.

The clam shell burial of the [left green dragon, right white tiger] unearthed from this ancient tomb directly pushed the beginning of the four-elephant astrological tradition to two thousand years before history.

Fang Yuan was not so interested in the history that was too long.

Or rather, he doesn't think he should be interested in them.

His ignorance in this area is all caused by the lack of brains.

When the brain group is in place, the content that comes with these base group encyclopedias will not be a problem at all.

In contrast, Fang Yuan prefers to listen to what happened to Liang Tian and whether he wrote about it in his memoirs.

"Old man Liang, you said earlier that after the [Mabuhai No. 1] in 97, our country has experienced three years of benign development. And after that? You're going to work with Brother Dong to study manned spaceflight? ”

"No, Dongge and [921 Project] missed each other, when the manned space program began to advance, wasn't China's international commercial space going through the darkest moment?"

"That's a pity."

Fang Yuan couldn't hear anything like missing his dreams, so it was easy to empathize.

"I did feel sorry for Brother Dong, but Brother Dong was very open-minded, and he always said that he had caught up with the good times."

"It's good times, isn't it?"

"Well, three years in a row have made our country want to have its own global satellite navigation system."

"Beidou navigation, huh?"

"You're talking about 2000, right? I remember that Beidou was established in 1994, right? ”

"The project was established in 1994 with the Beidou-1, which is a navigation system used by our country itself, and we did not think about making a global satellite navigation system at the beginning. Beidou navigation took 26 years to complete the global network. ”

"I have seen this in the history books, and our country's Beidou is divided into three steps."

"Xiao Fangyuan has read a lot of history books!"

"Then this is all required content, and it must be memorized." Fang Yuan memorized the original words in the history book: "Beidou navigation is the second national strategy of China's aerospace after [two bombs and one satellite], and it has derived the [Beidou spirit of the new era], and its influence has penetrated into all aspects of life. ”

"All aspects of life ......" Liang Tian thought for a while and commented: "This sentence sums up very well, you people born in 2050 are actually not very obvious about the changes that Beidou navigation has brought to your life." ”

"How so?"

"From the moment you were born, many things are directly around you, for you, it may be as normal as air, and we are watching Beidou step by step, changing all aspects of our lives."

"For example?" Fang Yuan asked Liang Tian to give an example.

"Let's put it this way, when we were young, it was very difficult to know the exact time. My fathers had to always find a place to spend time inside their tables. I often don't know the specific time because the watch or the clock at home stops, and with Beidou navigation, there is an all-weather high-precision timing service. ”

"Uh......"

Fang Yuan really couldn't imagine that there was still an era of technical difficulty in answering the question of [what time is it now].

"Old man Liang, I am willing to sleep in the dark without knowing what night it is, this time is not time, it doesn't matter." Fang Yuan habitually raised the bar.

"Xiao Fangyuan, the calibration time, I specially said it to you in order to give you an example."

"What about the bigger?"

"To put it mildly, the precise time of stock trading, the precise time of high-speed bullet trains, the specific height of Mount Everest, and the speed of melting of Tianshan No. 1 glacier all have to be measured by Beidou navigation."

"Oh. All right. I don't have the capital for stocks, I have no interest in Everest and Glacier, as for high-speed bullet trains, all the cars now, they have long been unmanned, and there is no difference between arriving early or late, a difference of one and a half seconds. ”

Habitual bar raising×2.

"Unmanned driving itself is also achieved through Beidou."

"Is that so? I am a simple human brain, and it is normal to have incomplete knowledge. ”

It's useless to raise the bar, there are always excuses.

"At the end of the day, it's all too common for you. In a similar situation, for us, we have experienced many historic moments. When I started shopping online, Beidou Navigation could tell me where the delivery had arrived, and when Liang Hangyu called an online taxi for my pet to come to my home, Beidou Navigation could let me at least when I should go down to pick it up. ”

"Old man Liang, do you call your son's online car-hailing for pets a historic moment?"

"It's never been unusual, as long as it hasn't happened before, it can be called a historic moment."

"Okay. I try to pretend I'm convinced by you. Fang Yuan said quite seriously: "I hope that you and your family will try not to take a taxi for your pet alone, being alone in the car, it is easy to think that you have been abandoned." ”

"Little doll, you're looking for a strange focus."

"What's weird? The law stipulates that owners are fully responsible for the behavior and safety of their pets. It is the responsibility not to let the pet hurt others, and it is also the responsibility not to let the pet ride on the transportation independently. ”

"When Liang Hangyu sent his dog to me by taking an online car-hailing car, the car was still driven by a driver, and it was not considered an independent ride."

"It's still easy to have an accident, right?" After asking, Fang Yuan himself smiled: "Am I talking a little far." ”

"Okay." Liang Tian didn't mind, and naturally returned to the previous topic: "Do you know, Xiao Fangyuan, our country is not legally able to have its own navigation system, and there are less than 4 hours left for a while. ”

"Four hours?" Fang Yuan expressed doubts: "If I remember correctly, it took twenty or thirty years to build the Beidou navigation, using the [Changsanjia] rocket, 44 launches, and an astonishing 100% of the arrows were not missing." ”

"Xiao Fangyuan still knows a lot about Beidou navigation."

"I don't have a brain, and I don't have a brain. At the beginning of your trip, you went to the Xichang Satellite Launch Center, which was specially loaded and cared, and it was also known as the Beidou home port. ”

"Thank you little doll for caring so much about my upbringing."

Fang Yuan wanted to make a grimace.

This is in line with his state of mind at this time.

But it doesn't fit the character he wants to create.

The mature deputy captain directly said the key point: "If you start to calculate the project in 1994, it obviously took 26 years to successfully build a global network, how did it come to you, and the legitimacy is calculated in hours?" ”

"When I say Beidou four hours, I don't mean what you understand." Liang Tian explained loudly, "It is the time to get the construction permit before the establishment of the Beidou global positioning and navigation system. ”

"We need to get permission to build our own navigation system?" Fang Yuan had no contact with this period of history.

"Of course, the orbital resources of navigation satellites are limited, and in 2000, when our country wanted to have its own satellite navigation system, 80% of the good positions were occupied by the two countries that first started the space race."

"According to your statement, since there is already a global positioning and navigation system, wouldn't it be better to use it directly? Why do you have to have your own? ”

"Before the establishment of the Beidou navigation system, our country used GPS. Think about it, if you need to navigate, not an online car-hailing, but a missile, using someone else's navigation, is it equivalent to being completely blind at any time? ”

"Old man Liang's height is just different!" Fang Yuan would not have thought of this.

"It's the same for civilian use, without Beidou navigation, there would be no 2020s, and you can make satellite phones at your fingertips." Liang Tian concluded: "From any point of view, navigation must be a system to be owned. ”

[Far ahead] This stalk, probably only people who have used the first batch of mobile phones that can make satellite calls will feel it.

Forty or fifty years have passed, and Fang Yuan doesn't know the potential meaning of Liang Tian's words.

What Fang Yuan was more concerned about was what Liang Tian had mentioned before.

"Old man Liang, what do you mean by Beidou four hours?"

"As mentioned earlier, when our country embarked on the formation of a global satellite navigation system, there were very few good positions left in geosynchronous orbit. ITU's application for GNSS orbit resources is on a first-use, first-served basis, with expired applications forfeited. ”

"First served?" Fang Yuan joined his understanding and asked out loud, "It's not in the order of application, right?" ”

"Yes. In 2000, ITU identified three available locations. At that time, we were also applying with the European Union. ”

There are so many countries in the world, and there are not only one or two people who want to have their own navigation.

Many countries have filed applications.

ITU requires China to accurately launch navigation satellites to a specified location within seven years and send back signals.

This process is the same as the fact that after the launch of [Dongfanghong No. 1], the electronic signal must be transmitted back to be considered successful.

However, this time, what is needed is not trembling electronic music, but clear navigation signals.

If it can be done, the three good positions that ITU has found are China.

If you can't do it, it's someone else's.

Moreover, it is very likely that our country will never be able to have an independent satellite navigation system because of this.

Beidou navigation in the eyes of the public and Beidou navigation in the eyes of astronauts have never been the same thing.

From 2000 to 2007.

Seven years sounds like a long time.

In 2000, he was still in the sixth grade of primary school, and in 2007 he completed the college entrance examination.

But for Chinese astronauts, it is necessary to race against time.

"In this, not only do we have to overcome our own technical difficulties, but we also need to face embargoes and technical blockades that may be possible at any time."

"Your generation is stuck in all sorts of ways, isn't it?"

"Yes, the first thing to bear the brunt of is the rubidium atomic clock."

"What are rubidium atomic clocks used for?"

"Rubidium atomic clock is a spaceborne accessory with navigation satellites as the core. A rubidium atomic clock that meets the requirements of a navigation satellite must achieve an error of one million years, within one second. ”

"Uh...... For a million years, I don't know how many have been found on the other side, and if human beings still exist, they should not have lived on the earth for a long time, so what's the point of counting about a million years and a fraction of a second? ”

Fang Yuan was a little disapproving: "Old man Liang, you can't impose your father's desire for precise timing on the satellite. ”

"Little doll, you can be admitted to college at the age of 14, shouldn't you really go through some back door?" Liang Tian raised some doubts about Fang Yuan's reserves.

"Don't you know better than I know if I have a back door to go through or not?" Fang Yuan's eyes widened a little angrily.

"Eh, look at my old dizziness, Xiao Fang was originally researching materials, not space technology, I almost forgot."

Liang Tian gave lectures to young people on the earth, and he had never encountered such a problem as before.

In the generation with a brain group, common sense is automatically mastered by everyone, but it is difficult to specialize in the arts.

Fang Yuan is the opposite.

He can study his field to the extreme.

I don't know anything about the common sense that many of my peers trigger automatically.

Fang Yuan squinted at Liang Tian, didn't say a word, and only expressed his attitude with his eyes.

Liang Tian patiently gave Fang Yuan some popular science.

The basic principle that satellites are able to achieve positioning is time-based calculations.

The time taken from the time the satellite sends the signal to the time it is received by the user can be used to calculate the distance between the satellite and the user.

With this distance as the radius, a virtual sphere can be formed.

When the user connects 4 satellites in different positions at the same time to form 4 virtual spheres, there will be a meeting point.

This meeting point is where the precise location is.

Location is space, but this location is measured by time.

The accuracy of the rubidium atomic clock determines the accuracy of navigation.

After saying this, Liang Tian looked at Fang Yuan and asked out loud: "Little Fang Yuan, the old man said that, do you still understand?" ”