In this era, the concept of satellite communication networks is not very mature.

The common communication method still relies on the ground transmission tower and various cables for relay connection.

Although this method of communication also has the advantage of stable connection, because of the need to build a huge number of ground base stations and communication cables, the required infrastructure investment is actually very large.

At this time, the most common communication method for people in China is still fixed telephone, and there are very few people who can use mobile phones.

So for mobile communications, everyone actually has no needs.

However, the absence of such a demand now does not mean that there will be no such demand in the future.

After that, in just 20 years, China has become the country with the most mobile devices in the world, and the demand for this is actually very large.

Therefore, it is necessary to plan the construction of a low-orbit satellite communication network now for the sake of precautionary considerations.

Generally speaking, the distance of 100 kilometers to 300 kilometers from the earth's surface is low orbit, and the service life of satellites operating in these orbits is generally not very long, because they will constantly fall to the surface under the influence of the earth's gravity, and can only use fuel to maintain the orbital altitude.

Low orbit has many benefits for satellite communications, the biggest of which is to reduce costs.

For example, Iridium is located at an altitude of about 800 kilometers, while the altitude of the new generation of low-orbit communication satellites is basically about 300 kilometers.

This puts the thrust of the rocket at a lower rate, and the number of satellites that can be launched at one time is also greatly increased.

For example, the Chang-3B rocket, which made its first flight this year, has a carrying capacity of 5.65 tons in an 800-kilometer orbit and a carrying capacity of 10.82 tons in a 300-kilometer orbit.

This means that the launch cost of a low-orbit satellite is half that of a high-orbit satellite.

Of course, apart from Zhang Xingyang, there are no real people in China who are really aware of the commercial and military uses of low-orbit communication networks.

But this does not prevent Zhang Xingyang from instilling his own ideas in others.

"Old Chen, what do you think will happen to the form of network communication in the future?"

This is a symposium on the eve of the establishment of the domestic Internet network information center, to discuss various matters of the future Internet.

Although Chen Zhongyan is the chief master of Beidou navigation, it does not mean that he does not understand the development of the Internet, on the contrary, he knows it very well.

"The future network communication mode must be through wireless transmission to access user equipment, as for the use of ground base stations for signal coverage, or satellite network for signal coverage, it is difficult to say."

"Xiao Zhang, what do you think?"

After all, the establishment of the Internet Network Information Center has been prepared for several years in China, and the preparations in various aspects have actually been relatively perfect.

Therefore, the two of them still like to talk a little bit more about the two people's majors, and the content in the aerospace field.

"Old Chen, these two methods actually have their own advantages, but I personally prefer to use a low-orbit satellite network."

"Oh? Tell me your reasoning. ”

Chen Zhongyan was a little interested, because he felt that Zhang Xingyang really seemed to have his own unique opinions.

"The only satellite communication network in the world is Iridium's global telephone service, which has just been launched this year."

"However, because the number of communication satellites they actually use is only 66, although they can cover the whole world, the amount of data that a single satellite can access at the same time is very low, and it is impossible to meet the huge amount of data after the arrival of the Internet era."

"Therefore, if you want to really connect to the Internet through satellites in the Internet era, what can really be used is to launch a large number of small satellites in the low orbit of the earth for network communication."

Chen Zhongyan did not expect Zhang Xingyang's ambition to be so big, because if the network construction is really carried out in this way, the construction cost required is definitely much more than that of using the ground base station for networking.

"Xiao Zhang, have you ever thought about such a cost problem, as well as the follow-up maintenance problem?"

Chen Zhongyan frowned and expressed his opinion, not particularly agreeing with Zhang Xingyang's thoughts.

"Old Chen, in fact, the cost is really not as high as you think."

"Huh? The cost of rocket launch alone is a big cut, not to mention the cost of satellites. ”

As the chief engineer of the Beidou navigation system, Chen Zhongyan is naturally not a layman, and knows that the cost problem here is mainly focused on satellites and rockets.

However, he did not know that the Rocket Research Institute had been busy with the research process of new rocket engines and new recyclable rockets this year, otherwise he would not have had such concerns.

"Don't worry about this, our research institute is currently developing a high-thrust liquid oxygen kerosene engine, which can meet the requirements of multiple recycling."

"If a recyclable rocket is used, the launch cost of the satellite will be reduced to a very low level, and it is expected that the launch weight of one kilogram will not exceed 5,000 yuan."

"As for the issue of satellites, we don't need to use a generation of satellites for more than ten years like Iridium, which actually makes his satellites expensive and difficult to replace."

"The design life of the satellite only needs one to two years, which not only reduces the production cost of the satellite, but also makes it easier to upgrade it for the future."

Chen Zhongyan thought in his heart that if what Zhang Xingyang said was true, then the matter of low-orbit satellite networks could still be tried.

I just don't know if what he said is true, after all, Zhang Xingyang's age is too young, according to ordinary people's ideas, he can't do things firmly without hair.

Although Zhang Xingyang has done a lot of things since he took over the research institute, he still hasn't accumulated enough prestige to make people believe in him.

"Old Chen, let me calculate an account for you, the initial construction of the domestic satellite communication network will require the launch of about 4,000 low-orbit satellites."

"And the new generation of recoverable rockets we designed can launch a payload of about 26 tons to a 300-kilometer orbit at a time, assuming that each is 250 kilograms, then it can launch 104 satellites into the sky at a time."

"In this way, 4,000 satellites only need 40 rocket launch missions to complete."

"If you use recyclable rockets, even if each rocket is reused only five times, then only eight rockets are needed to complete the launch mission."

"Even if you can only recover the first stage of the rocket, you can save a lot of money, and our rocket uses liquid oxygen kerosene as fuel, which is cheap."

"All things considered, the cost of building a low-orbit satellite network is actually much cheaper than building thousands of ground base stations."

Zhang Xingyang seriously calculated the cost for Chen Zhongyan.

At this time, Chen Zhongyan realized that he seemed to be really persuaded by him, and laughed:

"Xiao Zhang, what you said is very good, but when will your rockets be built?"

"The country can't have so much time waiting for you!"

"Although I also hope that this system can be established, the technical difficulties in the short term are still quite large."

For Zhang Xingyang, the technical problem is the least need to consider, and what he needs is more policy inclination and funding.

"Old Chen, our rocket will definitely be tested within next year, and we will never let the country wait for us!"

Looking at Zhang Xingyang, who was almost on the verge of making a military order, Chen Zhongyan was also a little curious about how far he could go:

"Okay, I'll talk to you about this idea, but if you want to actually make this happen, it depends on the progress of your rocket development."