The new 110-ton liquid oxygen kerosene engine has been tested dozens of times on the test bench in the past six months, with a comprehensive duration of more than 10,000 seconds.

Several rounds of tests have been carried out on the operation status of the new liquid oxygen kerosene engine under various working conditions, and detailed data of the engine under different conditions such as ground environment and high-altitude environment have been obtained.

The influence of the high-altitude environment and the ground environment on the engine is still relatively large, and the low gravitational force at high altitude, the rarefied atmosphere and the low temperature have a certain impact on the operation of the engine.

This is the rocket engine with its own oxidizer, and the aircraft engine that uses air as the combustion oxidizer has long been abandoned in the high-altitude environment.

In the past six months, the test time of a single engine has also increased from more than 400 seconds to more than 1,000 seconds.

Because the new liquid oxygen kerosene engine is likely to be used in the first batch of recyclable rockets for test flights next year, the service life of the engine is directly related to the number of times the rocket is used.

Each extension of the service life of a rocket engine basically means that a part of the cost of using a recyclable rocket will be reduced.

Only when the cost of using the recyclable rocket is low enough can Zhang Xingyang be sure to persuade the leaders above to carry out the low-orbit satellite communication network plan that seems to be very exaggerated.

After all, according to Zhang Xingyang's description, the number of satellites in the entire program has almost reached more than 50,000, which is very unbelievable to people of this era, and the number that needs to be replaced every year has reached about 20,000.

Even if the thrust of the newly developed rocket developed by the Rocket Research Institute is large enough, hundreds of low-orbit communication satellites can be launched with each launch.

More than 500 rockets are still needed, and the cost of rockets alone is in the billions, close to tens of billions.

And that's just the cost of building the satellite communication network, not counting the annual maintenance costs that follow.

More than 20,000 satellites need to be launched for maintenance every year, and if the traditional one-time rocket scheme is adopted, then more than 200 rockets are needed, even if the domestic price is not very high at this time, the cost of labor and materials is very low, and the cost is close to three or four billion.

You must know how much the annual military expenditure is, a total of less than 50 billion.

This was to be distributed between the army, navy, and air force, and the Second Artillery Corps (later the Rocket Force), which existed as a strategic deterrent.

If the strategy of rocket recovery is adopted, even if the first batch of rockets cannot reach the theoretical recovery of 10 times due to technical problems, and only three or four times of reuse, it can save nearly 60% of the rocket cost.

That is to say, the construction cost of the whole system can be reduced from the original tens of billions to three or four billion, and the follow-up maintenance cost is only about two billion per year.

And that's just the cost of a complete low-orbit satellite communications network.

According to Zhang Xingyang's idea, in the first two years, basically only the domestic communication network can be built.

In order to successfully build a domestic communications network, only 4,000 low-orbit satellites are needed to complete the basic construction.

Moreover, these 4,000 satellites can still be completed in stages, and the first phase of the construction project can be completed with only 1,000 satellites in Zhang Xingyang's planning.

After all, what everyone needs most at this time is not the high-speed traffic Internet function like in later generations, for many people who have never even been in contact with a mobile phone in their lives, the voice call function is the most important.

The amount of data transmission occupied by the voice call function is completely incomparable with the Internet function.

Because the first few rockets will not be directly used second-hand, third-hand, or even nine-hand rockets, the cost will be slightly higher.

But it is also necessary because the first few launches have to test the performance of the rocket to a certain extent.

In order to make the first experimental launch of the recyclable rocket in 97 years, the people of the various systems are desperately trying to catch up.

The most critical and difficult of the whole system is the propulsion system of the first-stage rocket.

The first-stage rocket propulsion system, which uses eleven YF-110 liquid oxygen kerosene engines, seems to rocket engineers in this era to be basically monster-level difficulty.

You know, no one in China has ever done such a complex propulsion system before.

Because this rocket only has a two-stage structure, the first-stage rocket as the main source of propulsion is extremely demanding, and the three-stage rocket system that was commonly used in China before.

Compared with the two-stage rocket structure, the three-stage rocket system has stronger redundancy ability, which can more easily adjust the attitude of the rocket during flight.

However, the three-stage rocket will be more complex in terms of overall structure, but it will be simpler on the propulsion system of each stage, after all, each stage needs to be propelled at a lower height.

Especially for the rockets that were commonly used at this time, there have never been so many rocket engines per stage.

Take the Chang SanB rocket that was launched not long ago as an example, its first stage rocket uses four YF-31C liquid rocket engines.

Although four boosters using YF-25 rocket engines are used at the same time, it is actually less difficult because of the bundled form.

After all, when the Changsanyi rocket was launched, the four YF-21C liquid engines and four boosters of the first-stage rocket were ignited at the same time.

The eleven rocket engines of the newly developed recyclable rocket, because the recovery function should be taken into account, then some of the rocket engines must be turned on when recycling, so that the first-stage rocket can be decelerated and landed.

This requires that the eleven engines of the new recyclable rocket be controlled separately and ignited in stages.

This puts forward higher requirements for the design difficulty of the entire first-stage rocket propulsion system, compared with the previous rocket design difficulty, one seems to climb Mount Tai, and the other is to climb Mount Everest.

It is precisely because of this that Zhang Xingyang arranged this linkage test of multiple rocket engines to test the mutual influence of the engines when they are running separately.

The number of engine linkages tested has been increased from two to eleven units, also in order to gradually explore the influence between them.

This is also to prepare for the launch of various models with different thrust sizes and different orbital carrying capacities in the future.

After all, it is impossible to use high-thrust rockets every time, and sometimes some low-thrust and low-cost rockets are also needed on some commercial launch missions.

For example, there are only four YF-110 liquid rocket engines as a small-thrust rocket with a first-stage rocket propulsion system, and the overall cost is only about five million, which is very suitable for commercial launch missions of some small satellites.