Demystifying the twists and turns behind the success of Fat Five
Long March Five Rebirth
On the evening of December 27, the Long March 5 Yaosan carrier rocket was successfully launched. Guo Wenbin / Photo
Qian Xuesen, known as the father of China's aerospace, once said: If scientific experiments can be successful every time, why bother? Setbacks and failures make us smarter.
The "Nirvana of the Phoenix" journey on the Long March 5 is the best example right now.
Two years ago, the second launch of the Long March 5 suffered a defeat. This news shrouded the hearts of the Chinese people like a haze, and once caused questions. Today, the largest rocket in China lasted for more than 900 days.
On December 27th, accompanied by a roar of shocking Yue, Long March 5 launched its third flight at Wenchang Space Launch Site. A group of dazzling flames surrounded the big rocket “gorgeously turned” and flew. Out of the sky. In the end, the mission was declared a success. This big rocket fell dormant for two years, and finally raised his eyebrows and exhaled!
Behind the sky can be described as "one twist and one twist." In the words of Long Lehao, an academician of the Chinese Academy of Engineering and chief designer of the Long March Series rockets of the First Academy of China Aerospace Science and Technology Corporation, he often said, "Failure is almost a success, and success is a failure." Day and night, the Chinese astronauts dare not take it lightly.
Thrilling 2 hours 43 minutes
The Long March 5 is a rocket that is doomed to be extraordinary from its birth. It has pinned the dreams and aspirations of too many people. For a long time, when talking about the development of a certain technology or field in China, people have been used to describe it as "big but not strong". But aerospace is breaking this claim, and the first fist to break it is the Long March V-equivalent to a "space power" ticket. Its development difficulty can be imagined.
As early as 1986, China has already carried out the demonstration of a new generation of launch vehicles. Since the mid-1990s, research on new generation rocket engines has been put on the agenda. In 2016, after a 30-year demonstration of a new generation of large rockets, the Long March V made its first successful flight and attracted much attention.
However, behind the success of the first flight, there were also episodes of "almost failed".
Hu Xudong is the 01 commander of Long March V ’s first flight mission. He still remembers that it was November 3, 2016, and the launch time was postponed from 18:00 to 20:43. In the meantime, it experienced 6 breathless time resets, and even once faced the test that the launch mission was forced to be cancelled.
People watching the launch therefore remembered the special moment of "surprising danger", and also had a bit more intuitive understanding of this rocket that kicked off the prelude to the era of China's big carrier.
The time returned to 17:30 on the same day, the atmosphere in the measurement hall suddenly became tense, and the eyes of hundreds of scientific and technical personnel all turned to the big screen. Because the first-stage circulating pre-cooling pump of the rocket could not start normally, the rocket "fever". The temperature displayed on the big screen at this moment is 238K, which is much higher than the takeoff standard of 110K ...
According to Hu Xudong's recall, at this time, the mission command research decided that if the engine's pre-cooling effect did not reach the launch conditions by 19:30, the propellant leakage procedure would be started to cancel the launch mission.
At 19:28, there were only two minutes left to the "bottom line", the engine temperature dropped to a predetermined value, and the rocket successfully "fevered".
"Set the ignition time to 20:40." Hu Xudong exhaled loudly. However, even at the last moment before the launch, emergencies have repeatedly occurred.
At 20:40, with only one minute left before the last launch, Hu Xudong had just issued the "1 minute preparation" password, and suddenly heard the commander of the control system Wei Kang issued the "best password in the history of Chinese aerospace": "01, abort the launch!"
At this moment, Hu Xudong stood up involuntarily and asked a question.
Ten seconds before the launch, Hu Xudong began to count down, and suddenly received a request from Wei Kang "Please wait."
"Abort the launch!" Hu Xudong stopped the launch procedure and organized an investigation of the cause of the failure. The problem was finally resolved.
The "ignition" password was finally issued, and the rocket took off.
Behind the cheers, astronauts, including Hu Xudong, began to organize and analyze the launch data. They are faced with 630,000 pieces of raw data-these are related to whether China ’s big rockets can still “turn the crisis into safety” next time.
Guessed the beginning but didn't guess the ending
Long Lehao was on the scene during the first two missions of the Long March 5. One of his obvious feelings is that although the first launch mission was successful, the "stumble" 3 hours before takeoff seemed to be more touching. He said: "This is also inevitable. After all, this is a brand new rocket. The situation is too complex."
Correspondingly, for the second launch, for many people at the scene, "it was said to be very smooth." "Before take-off, it was not as thrilling as the Long March 5 Yaoyi (that is, the first flight mission, reporter's note, the same below)." Long Lehao said, Yao Er's launch site, "much calmer" "better in the first few minutes Much more. "
He was still thinking, "This may be the first tortuous experience, exposed some problems, and then did a lot of improvement work. I have experience, and my mind is relatively stable."
Indeed, after the second take-off of the Long March 5 from the Wenchang Space Launch Site, everything in the first few minutes of flight was normal. But after flying for more than 300 seconds, the problem appeared.
"Suddenly, the (Long March 5) flight curve is not quite the opposite ..." In the test hall of Wenchang Aerospace Launch Site, Long Lehao saw on the big screen that the curve did not run up in their predetermined direction. It's "dropping" down.
His mind was tight: the drop of the flight curve meant that the rocket was gradually losing thrust. If the thrust was not enough, the rocket would have no acceleration and would not be able to overcome the effect of the gravity field.
"At that time, I had a premonition that it was 'finished', and this launch was about to fail ..." Long Lehao said.
The test hall was silent.
A measurement and control team member at the scene told reporters that their hearts, like the flight curve on the big screen, "keep falling down," and many people shed tears in silence.
That night, Xinhua News Agency issued a newsletter that the mission failed.
"No one wants to see this result." Long Lehao said, he quickly told himself that the failure of scientific experiments is inevitable. What should be done now is how to find out the cause of the failure as soon as possible, and take measures to fight for it as soon as possible. Go-around, and once again prove that our rocket is trustworthy.
That night, when Long Lehao left the test hall, he did not have too much communication with the aerospace juniors on the scene. But he believes that these young astronauts are capable of withstanding pressure. "It does look like this now, they are not overwhelmed by difficulties-they are lying down and still standing up!" Long Lehao said.
Is it the engine?
On April 16, 2018, the National Aeronautics and Space Administration released a survey of the Long March 5 Yao-2 rocket failure, which mentioned that the Long March 5 Yao-2 rocket had a sudden failure when it flew to 346 seconds.
The cause of the failure was that the turbine exhaust device of the first-stage liquid-hydrogen-oxygen engine of the core unit had an abnormality in the local structure in a complex thermal environment, and the thrust of the engine dropped sharply instantaneously, causing the launch mission to fail.
The engine, and the engine, yes, this word that once stung the Chinese people's key aviation technology, this time became a "stumbling block" in the aerospace field.
Big rockets are naturally inseparable from large thrust, and large thrusts cannot be separated from the engine. Prior to the Long March 5, the maximum thrust of a single active rocket engine in China was only about 70 tons, and it seemed "too weak" to launch a very large spacecraft.
New high-thrust engines came into being. According to Zhou Limin, secretary of the Party Committee of the Sixth Academy of China Aerospace Science and Technology Corporation, after 15 years of unremitting efforts, 8 newly developed 120-ton liquid oxygen kerosene engines were assembled on 4 boosters of the Long March V and 4 newly developed Hydrogen and oxygen engines are equipped with two each on the first and second rockets.
He has an image saying that the development of the engine is as difficult as climbing Mount Everest. "Some foreign experts said that even if we designed it, we would not be able to manufacture it." Among them, the hydrogen and oxygen engine that failed in the second mission. It is even more difficult.
Zhou Limin still remembers that in the face of a brand new engine, the development team began to work day and night to solve scientific and technological problems, dozens of new materials and more than 100 new processes were conquered one by one. However, starting the engine became the biggest stumbling block.
He said that the entire engine is in an unstable dynamic process during the starting phase, because the speed changes from a stationary state to tens of thousands of revolutions, and the temperature must go from a low temperature state to a high temperature state. Our control timing is controlled in milliseconds. If any one of the actions does not cooperate well, failure to achieve the expected results may lead to failure.
What initially struck the development team was that after the prototype of the engine used for the first flight of the Long March V was developed, its test results were failed four times in succession: two start explosions and two gas system burns.
Zhou Limin said that these blows the confidence of the entire research and development team and design team very much. "Many people dream of the explosion, they ca n’t eat, and they do n’t sleep well."
Shoot out the "devil" and destroy the "enemy"
And these are just the "pain" that Chinese astronauts encountered in the engine development stage. After the failure of the Long March 5 Yao 2 mission, the pressure on these people became even greater. They even called the problem of a failed engine "the devil".
An experimental member of the Sixth Academy of China Aerospace Science and Technology Corporation told reporters that in order to eradicate the "devil" and eliminate the "enemies", the development team has suffered more than two years of suffering, hardships, twists and turns, and doubts. The grinding, hard work, struggle, and tackling that we have experienced are also rare in the history of development. Especially for those "devil" who are deeply hidden, the tension of fighting is more complicated than ever.
"The" Devil "popped up from time to time, blinding the development team's eyes and even pushing them into the boundless abyss where the fingers were out of reach. But the development team was not intimidated by the darkness and was not crushed.
According to the statistics of the Sixth Academy of China Aerospace Science and Technology Corporation, in the second and third quarters of 2019 alone, the team ’s 11 hydrogen and oxygen engine development teams in Beijing accumulated 23,000 hours of overtime, and finally eliminated the “devil” hidden in the engine and eliminated The "enemy" who resists and resists stubbornly eliminates hidden dangers and eliminates faults.
The chief designer of the Long March 5 rocket told reporters that after the Long March 5 Yao 2 rocket failed, after more than 100 days of troubleshooting and positioning, and more than 180 days of test verification, the cause of the failure was finally confirmed. After that, according to the conclusion of the failure investigation, the development team made design improvements to the core-level hydrogen and oxygen engine, and adopted corresponding improvement measures from the aspects of structure, materials, and technology to improve the adaptability to the flying environment.
The cause of the fault was found, identified, and improved. Everything looks so smooth.
However, new problems have arisen.
On November 30, 2018, problems occurred during the long-range test of the improved core-level oxyhydrogen engine.
Li Dong told reporters that this time the astronauts responded faster. According to the cause of the failure, the development team improved local weak links in the engine to increase the dynamic strength margin of the structure.
On March 29, 2019, the zeroing work and improvement verification of the engine test failure were all completed-the two long-range test verifications passed smoothly, and the second problem was thus resolved.
But soon, they ushered in the third "encounter".
On April 4, 2019, when the final assembly of the Long March 5 Yaosan rocket entered the final stage, a core-level hydrogen-oxygen engine for subsequent missions, during the analysis of test data, an "abnormal vibration frequency" ".
It can be said that there are twists and turns, and once again verify the sentence: the road of scientific exploration has never been smooth.
"Without a trace of doubt, God!" Li Dong said, the developer found the problem "the crux" of the problem-the local structure of the engine, very sensitive to the complex force and thermal environment, easily cause resonance, once excited, it is not easy to decay.
In July 2019, the developers completed structural improvements to the engine and completed more than a dozen large-scale ground tests.
At this point, the engine problems that have plagued the Long March 5 for more than two years have finally been investigated.
According to the statistics of the First Academy of China Aerospace Science and Technology Corporation, the Long March 5 failed from July 2nd, 2017 and successfully launched on December 27th, 2019. It took 908 days and carried out more than 40 key technical tests.
908 days and nights, and climbed up again after numerous falls. And the biggest "hard bone"-the hydrogen and oxygen engine, also completed the Phoenix bath fire, Nirvana rebirth in more than two years.
According to Long Lehao, more than 900 days, such an interval time-beyond the mission failure cycle and then follow-up flight cycle, in the history of the Long March rocket is relatively long, he did not even have such a long interval in his impression The "zeroing" of time.
"Of course we hope that the interval time is shortened a little, but scientific research cannot change with subjective wishes." Long Lehao said that the failure of the Long March 5 Yao-2 rocket was caused by the interaction of a certain engine component under the complex force-heat environment. Occurrence of failure-This problem is hidden deeper, in most cases it does not occur, but only occasionally, but once it occurs, it is a "catastrophic result".
In his opinion, this "return to zero" finally caught this troublesome "devil". Although it took a long time, it was worth it.
"We all held our breaths"
In fact, it is not possible for a few teams to complete the "devil" and "rebuild" the engine.
Yan Yong, deputy director of the Beijing 11th Institute of the Sixth Academy of China Aerospace Science and Technology Corporation, told reporters that the failure of the Long March 5 Yao 2 rocket launch has pushed the liquid power business with a "gold medal power reputation" to the cusp of the wave, and the core first-level high-oxygen rocket The failure of the engine put the engine development team under tremendous pressure and test. With the help of the group and the Sixth Academy, the institute uses all effective resources to carry out the zeroing work-it can be said that this is a "national unity" of technological breakthroughs.
"I've seen so many academicians gather for the first time!" Said Lu Wei, the 11 director of quality in Beijing. His most impressive review was that 25 academicians and 5 university professors came to the scene as invited experts and listened. Engine development work, put forward opinions and suggestions, nearly 60 leading experts in the system also participated in the exchange and discussion.
In fact, after the defeat of the mission two years ago, many people are also eager to try and return to the "battlefield" to show their skills.
"If the setbacks obstruct the light of the road ahead, then lift the fire with no regrets at the beginning of the night!" Chen Jiwei, the commander of the station system of Wenchang Space Launch Station, told reporters that without frustration and discouragement, everyone took a breath, each system, Various positions were reorganized, starting from scratch, and immediately put into preparation for the go-around of the rocket.
Repeat the process over and over, imagine one after another, and run the drill over and over again. The air compressor of a system in the test station is not very stable. Equipment manufacturers have repeatedly performed dozens of improvement tests, and the problem still exists.
Many people have persuaded Chen Jiwei, "It's not a restrictive factor, it's almost OK." However, his answer was relentless. "The factors that affect the task must be discounted and solved to the end!"
Today, the Long March V has finally won this "combat war", and it has also become the most iconic mission of China Aerospace in 2019. And this is not only because it determines the implementation of major engineering tasks such as Chang'e-5, the Manned Space Station and the first Mars exploration, but also that it presents the process of scientific experiments from failure to success in such an intuitive way. In front of the public, people are impressed and amazed.
In addition to Qian Xuesen's sentence, Albert Einstein also had a "golden sentence" that was regarded as a guild by the scientific community. The main idea is that a person on the road of scientific exploration has made detours and made mistakes, which is not a bad thing What's more, it is not a shame. In practice, we must have the courage to admit and correct mistakes.
Long March 5 did it. The Chinese astronauts did it.
China Youth Daily · China Youth Network reporter Qiu Chenhui