Minutes and seconds passed.

Half an hour later.

"The command center, the command center, and the helium drainage have been completed, and the temperature measurement of the pump casing is still 15K higher than the standard temperature......"

The news coming back from the front made the atmosphere in the hall of the command and control center suddenly become solemn.

"Old Wu, is there any other way?"

Launch commander Wang Yudao.

Wu Chunmin shook his head and said with a wry smile: "Although the natural circulation pre-cooling mode is simple, it is the only measure that can be taken at present, even if other methods are useful, it will take time, the launch window is too close, and we simply do not have enough time to perfect a new set of pre-cooling schemes." ”

"If the temperature is 15K, what is the launch risk?"

"It's hard to say, but it's likely to have an impact on engine ignition."

Wang Yu turned his gaze to Liu Xuesong again: "Old Liu, what do you think?" ”

Liu Xuesong said: "There is no room for luck in space launches, and we can't let a problem rocket go to the sky!" ”

"In this case, I'm afraid this launch will have to be canceled."

"Even if it is canceled, it will not be a matter of time to find out the fault of the pre-cooling system. This will not only have an impact on the follow-up project of the 921 rocket, but also on the progress of the aerospace aircraft project. ”

For a while, everyone in the hall was talking.

Liu Xuesong glanced at Pang Xuelin, who was standing silently on the side, a little helpless.

Originally, he also wanted to invite Pang Xuelin over and let him see the 921 rocket, a product that represents the highest level of China's aerospace industry, but he didn't expect such a big mistake before the launch, which made people look down on it in vain.

Wang Yu said: "If you really can't do it, you can only order the termination of the launch procedure and postpone this mission." ”

"Wait!"

At this moment, Pang Xuelin's voice suddenly remembered: "Professor Wu, you just said that there is a way to improve a new set of pre-cooling schemes, what is the scheme?" ”

Wu Chunmin was slightly stunned and said: "There is another way, which is discharge pre-cooling, that is, before the engine starts, under normal pressure, open the pump front valve and pre-cooling discharge valve, and the cryogenic propellant flows through the front pipeline and pump of the pump under the pressure of the storage tank, and finally discharges it by the pre-cooled discharge valve in front of the main valve of the propellant. Since the propellant is discharged in a large flow in a short period of time, pre-shot replenishment is required to replenish the cryogenic propellant consumed by pre-cooling. In this way, not only is the propellant waste much more than that of cyclic pre-cooling, but there are also several problems with discharge pre-cooling. ”

"What's the problem?"

"The first problem is that the exhaust pre-cooling needs to discharge hundreds of kilograms of liquid oxygen in a very short time (about 5 minutes), and the tank must be replenished before ejection. The discharge of a large amount of liquid oxygen requires some corresponding pipelines and ground treatment equipment. In contrast, the liquid consumption for circulating pre-cooling is generated in three hours. The whole process is continuous, there is no special operation before injection due to pre-cooling, and the liquid oxygen used for pre-cooling is returned to the tank, and only the vapor phase components are discharged, so there is no need for special ground treatment and piping equipment. Therefore, the use of cyclic pre-cooling can greatly simplify the pre-firing operation and ground equipment. The second problem is that when the cryogenic propellant goes through the ground filling pipeline for a long time, it absorbs the external heat flow to increase the temperature, and the high-temperature propellant enters the tank, which increases the overall propellant temperature in the tank and decreases the quality of the propellant. The problem is that the 921 rocket adopts the method of cyclic pre-cooling, and we want to temporarily change to emission pre-cooling, so we need to carry out very complex calculations, and now there are only more than two hours left before the launch window is closed, and in addition to other pre-launch preparations, there is only less than one hour left for us to do theoretical calculations, and it is impossible for us to complete such complex calculations in such a short time. ”

Pang Xuelin said: "Is there any treatment equipment for exhaust pre-cooling?" ”

At this time, Wang Yu, the launch commander-in-chief, interjected: "This is true, our launch tower has prepared several sets of systems according to different rockets, and if the 921 rocket wants to use emission pre-cooling, the launch tower can provide supporting equipment." ”

Pang Xuelin smiled faintly, looked at Wang Yu and said, "Commander Wang, can you let me try it?" Within half an hour, I figured out the amount of liquid oxygen to be discharged for the discharge pre-cooling, and the launch procedure continued to move forward simultaneously. ”

"Half an hour?! Professor Pang, are you sure? ”

Wang Yu frowned, a little hesitant.

Liu Xuesong and Tao Yongchang also looked at Pang Xuelin with shocked expressions.

Wu Chunmin frowned involuntarily, he knew very well how terrifying the amount of calculations required for the pre-cooling system was, and in the process of pre-cooling calculation, it was inevitable to solve the two-phase flow.

The models for calculating and analyzing two-phase flow mainly include homogeneous model, split-phase model and slip flow model. Among these models, the homogeneous model is the least difficult, the slip flow model is the most difficult, and the discharge pre-cooling is precisely the slip flow model, even if there is a perfect mathematical model and with the help of a computer, Wu Chunmin will need at least one to two days to complete such a calculation, but Pang Xuelin said that he is sure to complete it within half an hour, how is this possible? !

Several other experts who understand the complexity of pre-cooling calculations have similar ideas to Wu Chunmin, but they have not raised objections.

On the one hand, Pang Xuelin's name is too big.

The addition of the Nobel Prize in Chemistry and the Fields Special Prize has almost raised him to an unprecedented height, and it is an insurmountable peak in the Chinese academic community.

On the other hand, it is Pang Xuelin's achievements.

Needless to say, even in the field of engineering, lithium-air batteries, carbon nanomaterials, room-temperature superconducting materials and other achievements, each of which has a very significant impact on the current global industrial system, superconducting materials are even expected to make Pang Xuelin win the Nobel Prize in physics again next year.

Therefore, since Pang Xuelin said that he was sure, no matter how doubtful everyone was, it was impossible to directly oppose it.

And they also want to see if the level of this big guy is as powerful as it is legendary.

Soon, the staff in the command hall gave Pang Xuelin the banknotes and found them.

Pang Xuelin picked up the banknote and asked Wu Chunmin about the parameters of the circulating pre-cooling system, and quickly calculated it on the manuscript paper.

Liu Xuesong, Wu Chunmin, Wang Yu and others came behind Pang Xuelin one by one, wanting to see the big guy's calculation ideas.

Soon, however, they gave up.

Because Pang Xuelin's calculations on the manuscript paper are like a book from heaven, not to mention them who are engaged in aerospace engineering, even if they are professional mathematicians, they can't figure out the formulas written by Pang Xuelin on the manuscript paper for a while.