The launch of the 921 rocket was scheduled for the afternoon of the next day, October 30, at half past five in the afternoon.

The entire launch center began to be busy as early as a month ago in preparation for this important launch.

Pang Xuelin was only invited to observe the launch of the rocket, except for visiting the launch center and cheering for the staff involved in the launch mission, there was nothing else to do.

At six o'clock in the morning the next day, Pang Xuelin changed into a T-shirt and shorts and sportswear, ready to go out for a run.

Although the genetic optimizer has greatly improved his body, as long as he has time, Pang Xuelin will still insist on the habit of getting up early to run.

When he was in Jiangcheng, he pulled Qi Xin to run with him every day, and occasionally Zuo Yiqiu and Zhou Chen would join in.

Here, only Zuo Yiqiu followed him.

Pang Xuelin opened the door and saw that Zuo Yiqiu, who lived opposite him, also came out wearing a tight sportswear.

"Professor Pang, good morning!"

"Good morning! Little Left, run two laps together? ”

"Okay."

The two of them walked out of the expert building and trotted along the asphalt road.

The morning air is fresh and humid, and the sea breeze is blowing in your face, which is refreshing and cool, and it feels very comfortable.

The Wenchang Satellite Launch Center is close to the coastline and is surrounded by lush tropical vegetation, making for a very nice environment

The two trotted along the asphalt road near the rocket assembly plant, and before they knew it, they came to the vicinity of the launch tower.

The huge 921 rocket stands majestically, and below the rocket, there is a large water tank deep in the ground, and the temperature of the rocket is as high as 3,000 degrees Celsius when the rocket is launched, therefore, under the launch pad, an inverted triangular water guide tank is set up, 22 meters deep, surrounded by the bottom of the launch tower, which will reduce the temperature to 1,000 degrees after the rocket is launched to ensure the safety of the ground device.

The fuel filling port of the rocket also emits white fog from time to time.

It is a white mist produced by the condensation of nearby water vapor due to the low temperature after the boiling and vaporization of liquid hydrogen and liquid oxygen.

The first and second stages of the 921 rocket are liquid oxygen kerosene engines, and the third stage uses hydrogen-oxygen engines, because liquid hydrogen and liquid oxygen will volatilize non-stop after being filled, so cryogenic fuel filling will continue until one hour before launch.

Pang Xuelin and Zuo Yiqiu ran around the launch tower before returning to the expert building.

There was nothing to do in the morning, Pang Xuelin stayed in the room until three o'clock in the afternoon, and he went to the command and control center accompanied by Tao Yongchang.

Although Pang Xuelin has experienced many adventures in the sci-fi world, it is the first time he has seen a rocket launch mission like the real world.

The launch command and control hall was in order, everyone was busy with their own business, and Pang Xuelin's arrival did not cause much of a sensation.

"Booster 1,3 suspected liquid oxygen leakage fault has been eliminated, and each number has followed up the status and entered the -3 hour procedure."

"The reset ignition time is 18:01."

"Understood!"

From time to time, the sound of passwords sounded in the hall.

Tao Yongchang saw that Pang Xuelin was a little curious, and explained: "Professor Pang, there should have been a small glitch just now, but it seems that there is no big problem, and it will not affect the normal launch." ”

Pang Xuelin smiled and nodded.

Aerospace is a high-risk project, and it is normal for various small problems to occur in the process of preparing for launch, and generally will not affect the normal launch.

At this time, Liu Xuesong also found that Pang Xuelin had come to the accusation hall and took the initiative to greet him: "Professor Pang, welcome to come and guide." ”

Pang Xuelin said with a smile: "I'm just a layman, I brought a pair of eyes over today, and it's really funny to guide something." ”

Liu Xuesong smiled and didn't say much.

Tao Yongchang said: "Lao Liu, what's the matter with that liquid oxygen failure just now?" ”

Liu Xuesong said: "There is a bit of a problem with the connection of the liquid oxygen filling port on the No. 1 and No. 3 booster side, which has been solved. ”

Tao Yongchang said: "That's good, I hope everything goes well with this launch." ”

The 921 rocket is a new rocket, and generally this new type of rocket has a relatively high launch risk.

For example, the second launch of the Long March 5 a few years ago directly led to the postponement of key projects such as China's space station, Chang'e-5, and Mars probe for two years.

This time the 921 rocket was launched, and the first launch was the aerospace aircraft demonstrator built by China with all its might, whether it was Tao Yongchang or Liu Xuesong, the pressure on his body was not small.

In the past, it would have been impossible for the top management to directly take such a valuable payload as the aerospace aircraft demonstrator to the new rocket for testing.

It is also because Pang Xuelin's Golden Dragon battery harvests global capital, and it is too easy to make money, so China has the wealth to directly install the aerospace aircraft verification machine on the first launch of the 921 rocket.

Liu Xuesong accompanied Pang Xuelin and Tao Yongchang to chat for a while.

Although he is the chief designer of the 921 rocket, he does not have to worry about the launch process.

He is on the scene and doing similar work to Pang Xuelin, which also plays the role of a mascot.

Time passed minute by minute, and before I knew it, it was more than four o'clock in the afternoon.

From time to time, the commander's instructions sounded at the scene.

"The fuel filling is complete, and the filling port is disengaged."

"Evacuation of the tower staff."

"90 minutes to prepare."

"The latest weather forecast shows that everything is normal in the launch window."

"The engine is starting to pre-cool."

……

Various commands sounded from time to time.

At this moment, an alarm suddenly sounded at the scene.

"Didi, the first stage pre-cooling failed, the engine over-temperature, the first-stage pre-cooling failed, the engine over-temperature ......"

The atmosphere in the hall suddenly became tense.

Soon, the No. 01 launch commander ordered: "110 suspend liquid oxygen discharge, suspend kerosene filling, and all systems remain in a state and do not enter the 60-minute procedure for the time being." ”

Pang Xuelin, Tao Yongchang, and Liu Xuesong also stopped talking, and the expression on Liu Xuesong's face was a little solemn, and he said, "Professor Pang, I'm sorry, I'll go over first and see what's going on." ”

Pang Xuelin and Tao Yongchang glanced at each other and hurriedly followed.

Experts in the lobby of the command and control center quickly gathered and began to discuss the failure.

For the problem of engine precooling failure and overtemperature, Pang Xuelin still has a certain understanding.

For liquid oxygen kerosene engines and liquid hydrogen and liquid oxygen engines, the boiling point of cryogenic propellant is very low, and it is in a gaseous state at room temperature, which is easy to vaporize during storage and transportation, and gas-liquid two-phase flow occurs, so it is easy to cause adverse or even destructive effects on the engine and pressurized delivery system.

To avoid these effects, the engine should be operated in such a way that the propellant remains liquid.

Therefore, the engine and its booster delivery system must be sufficiently pre-cooled before starting.

If there is no pre-cooling, or insufficient pre-cooling, the temperature of the pipeline and pump assembly will be much higher than the temperature of the liquid propellant, so that when the engine starts, the propellant will enter the pipeline and pump and other components in the state of gas-phase or gas-liquid mixed fluid.

The engine and pump can not work normally under this condition, which will cause cavitation, flying, or prolong the starting time and thrust climb time, resulting in pressure and flow fluctuations, stall operation, oxygen-rich combustion and other phenomena, and in serious cases, the start can fail completely.

The pre-cooling is to use the medium in the storage tank or other low-temperature media on the ground to cool the conveying system and the engine before the engine starts, so as to reach the allowable temperature and ensure the reliable operation of the pump.