Reforged Arrow
The story of Long March 7A rocket's go-around
At 7:01 on April 9th, the Long March 4B carrier rocket successfully launched the test 6 03 satellite into space. This was the 365th space flight of the Long March series of carrier rockets.
Rockets are the foundation for the development of aerospace industry. At present, my country's latest Long March series rocket is the "Long March VIIA".
At 1:51 am on March 12th, at the Wenchang Space Launch Site in China, with a huge roar, an orange-red tail flame crossed the deep blue sky. The Long March 7A carrier rocket drew a gorgeous curve and successfully completed the test nine. The number satellite was sent into a predetermined orbit.
As a new configuration rocket that fills the gap in the high-orbit orbit carrying capacity of China's launch vehicle, the successful flight of the Chang-7A has experienced some "small ups and downs."
On March 16 last year, the Chang-7A rocket failed to put the satellite into its intended orbit, and the launch mission failed.
Subsequently, the development team embarked on a journey to find the answer to the first flight failure.
From the first flight to the go-around, from failure to success, in the past 361 days and nights, how did they deal with the haze of failure, and how did they regroup and fly against the wind?
Failure-get all telemetry data as soon as possible
On March 16, 2020, the Chang-7A rocket flew for the first time.
Before the rocket was launched, the test team organized a rescue team to stand by at any time in the outdoor field to deal with various emergencies before the launch.
Tian Yurong, deputy director of the Long March No. 7 series model office, also stared at the rescue team.
The engine ignited normally and the rescue team's mission was over.
Tian Yurong let out a long sigh of relief, "The rocket flew very well at the time."
On the way back to the accusation hall with a colleague, the phone rang, "There seems to be a problem with the flight curve." Hearing these words, Tian Yurong's heart suddenly caught.
"My mind was blank. I raised my leg and ran to the accusation hall. It was not a long way, but it felt so long that I couldn't run to the head."
In the accusation hall, the test team members have gathered around the two chiefs (commander-in-chief and chief designer) of the Chang-7A model.
Within 162 seconds after ignition, the rocket's flight curve was perfect. Both the altitude and speed of the rocket were almost in line with the theoretical values. When the flight reached 168 seconds, it malfunctioned and the Star Arrow crashed into the Pacific Ocean.
where is the problem?
"You need to get all the telemetry data as soon as possible." Tian Yurong immediately contacted colleagues at the launch site.
"Everyone wants to find the reason as soon as possible and carry out the next step." Tian Yurong said, everyone immediately began to race against time. At a little bit late at night, they got all the data.
"I think my life is gone for half a year." said Ma Zhonghui, deputy chief designer of the Chang 7A rocket. From production to launch, most of her hard work has been spent on this new rocket.
Failure was caught off guard, and the most urgent task was to find the problem quickly.
Ma Zhonghui and the experts and team members watched the video over and over again, interpreted the data, and analyzed the reasons; the model two headquarters organized each unit to determine the working status of their products... Through overnight analysis, everyone found a phenomenon: the booster oxygen box engine entrance Insufficient pressure.
Why does this phenomenon occur?
Is it the "culprit"?
Zero-the most important thing is to find the cause of the failure
After the test team returned to Beijing, in accordance with the epidemic prevention and control policy at the time, they needed to be isolated at home for 14 days.
Time waits for no one, and the team members took the initiative to ask for "centralized isolation".
"Returning to zero as soon as possible is our responsibility." More than 40 core team members stayed at the Changzheng Hotel and took a shuttle bus every day to and from the hotel and the resetting work site. Experts, scientific research and engineering technicians from all walks of Trouble shooting and repair of Changqi A rocket.
This is the first time that Ma Zhonghui has encountered zeroing in more than ten years since he joined the work. "Associate telemetry data with abnormal phenomena during flight, find the initial abnormal phenomena, locate which system is out of order, and then use experiments and analysis to judge. The cause of the abnormal phenomenon is like solving a case.” Ma Zhonghui said that the most important thing to zero is to find the cause of the failure.
It does not mean to deny previous work, but to make up for what was technically inadequate.
The 361 days of flying against the wind began, and the whole team was engaged in the intense zero-returning work: looking at the computer every day, watching the data, watching the video over and over again, and collecting the data into a curve; then the aspect ratio was compared, and every detail was analyzed. For fear of missing an abnormal link, affecting the fault location.
During the first flight, the rocket appeared abnormal when it was only a few seconds away from the first stage separation at the end of the first stage flight segment.
Because of his familiarity with related technologies, the arrow body structure designer Yao Ruijuan took the initiative to sign up to participate in the zero-returning work. “Daily interpretation of data, meetings and discussions, early in the evening at 9 o’clock in the evening, usually in the middle of the night.” Yao Ruijuan said.
When the problem of failure became more and more clear and gradually focused on the power system, the designers of the power overall professional were mixed in their hearts.
Some people sit in the computer room and look at the data, and ask themselves repeatedly: Why haven't these issues been considered?
Seeing this scene, Fan Ruixiang, the chief designer of the Long Seven A Rocket, persuaded them: This is a problem of professional knowledge, a deep-seated problem that no one has realized, and has nothing to do with the individual, so we must treat it in a correct way.
Facing this unforeseen problem, Ma Zhonghui drew a lesson: technical problems are profound, we must respect technology, first, we must be rigorous, and second, we must verify in place, we must not take it for granted.
Simulation analysis locates the fault, but theoretical analysis alone is not enough, and it needs to be verified through experiments.
The time to reset to zero is tight, which puts forward a difficult test for the team.
Wu Hao, deputy head of the strength group of the third room of the General Design Department of the China Academy of Launch Vehicle Technology, watched the failed flight video of the rocket hundreds of times.
The test system is huge and complex. If there is any damage, there is no time to make new test pieces, which will directly affect the rocket's go-around.
"In the beginning, the test model was very large. It took 24 hours to calculate a calculation. It took too long. I continued to rebuild and refine the model. Within 10 days, I carried out nearly a hundred analyses, and the hands became'mouse hands'. "Wu Hao said that in the end, they reduced the model calculation time from 24 hours to 3 to 4 hours.
Through simulation analysis, she pointed out that there is a risk of damage to the second-level engine frame under abnormal third-level working conditions.
One stone stirred up a thousand waves.
This conclusion was questioned by many experts.
"I also play drums in my heart, but since I have discovered a potential problem, I have to break the casserole and ask it to the end." Wu Hao said, walking a road that no one else has traveled means opening a road in the mountains and building a bridge in the water.
There are many engine load conditions, and all factors are combined up to nearly a hundred kinds, and the original operating conditions of the previous tests are only a dozen.
Wu Hao and the team members reduced nearly 100 working conditions to 10 through simulation, and finally completed the test that normally takes two to three months to complete in 14 days. The simulation results and the test accord with 98%.
Go-around-fight a beautiful turnaround
Only by completing the go-around as soon as possible can the team's confidence be boosted, to come out of the effects of defeat, and to reverse the passive situation.
At the beginning of April 2020, after the fault location was completed, the Model Two Chiefs proposed to organize the mission of the Chang-7A rocket and complete the product preparation at the end of 2020, so that the rocket will have the factory conditions.
"This is a decision made under tremendous pressure from public opinion and production. The mission of the go-around is very important and we must go all out." Fan Ruixiang said.
Work progress has become the biggest problem facing the development team.
Chen Keqin, the model chief designer of the Chang 7A rocket servo system (a feedback control system used to accurately follow or reproduce a certain process), said that the production of an arrow, the servo products are usually required from production, assembly, assembly and adjustment to acceptance and delivery. It took half a year, but in order to meet the schedule requirements of the model go-around, front-line personnel worked overtime. This time it only took 3 months.
From April to June last year, Zhao Jianhua, the assembler of the servo mechanism, never took a weekend, and has been fighting on the front line.
"Because of the failure, I am more careful in my work, so I can't make any mistakes." In order to better understand the product status and make it easier to find problems, he has to record the product in detail every day, even if there is no information required to be recorded, he will also record it .
During the development of the Chang-7A rocket, the team not only prepared one rocket product, but also carried out 28 ground tests and 74 technical status changes.
In addition to changing the technical status that affects flight, more than 200 "triple" tasks (re-analysis, re-design, and re-verification) have been carried out to improve weak links.
The day the broken sword is recast is when the king returns.
On December 30, 2020, a brand-new Long-7A rocket was released and the factory review was completed.
After more than 300 days and nights of hard work, the development team of the Chang-7A rocket embarked on a new journey to go around.
The assembled rocket is tall and tall, and after completing a series of final assembly tests, it enters the vertical transfer procedure before launch.
At the end of the transfer road at the Wenchang Aerospace Launch Site, a huge launch tower held the rocket into its arms with open arms.
Looking at the towering rocket, Ma Zhonghui was full of emotion.
"Aerospace launch is a high-risk industry. Any small mistake will affect the work of thousands of people. These tasks seem ordinary, but they are not simple. It is this seemingly ordinary work that makes this new rocket hit. A beautiful turnaround!"
Failure is not a "curse", but a "catalyst" to promote China's aerospace development; adversity is not a desperate situation, but a "touchstone" to sharpen the will.
After passing the "darkest moment" and ushering in the warmth of spring, the carrier rocket represented by the "Changqi A" is holding the Chinese nation's dream of pursuing the stars and the sea.
And those spacefighters who live up to the time and live up to their youth, with the spirit of "dare to overcome all difficulties and obstacles, and dare to climb the summit of space science and technology", help China's spaceflight to go deeper in the universe.
◎Link
The Chang-7A rocket is a three-and-a-half-stage rocket formed on the basis of the Long March VII rocket and combined with the three sub-stages of the Chang three A series rockets. It is the main configuration of the new generation of medium-sized carrier rockets and fills the geosynchronous transfer of my country's carrier rockets. The orbit has a blank carrying capacity of 5.5 tons to 7 tons.
The Chang VII A rocket inherits the technical foundation of the Chang VII rocket and the Chang San A series of rockets, and adopts the design concept of "generalization, serialization, and combination", which is conducive to rocket mass production and supports the high-density launch of this type of rocket in the future.
According to the current mission schedule, the Chang-7A rocket will have full missions before 2025, and will perform 3 to 5 launch missions every year.
In the future, the Chang-7A rocket will also develop a larger diameter fairing configuration according to mission requirements. After the transformation, it can perform the launch mission of zero-degree orbital inclination satellites, as well as deep space exploration missions such as lunar exploration, fire detection and asteroid detection. , To provide important support for the construction of my country's space power.
(Our reporter Chai Yaxin)