Tianlong No. 3 review: 600 tons pull 820 tons, top students make low-level mistakes, and supervision cannot be absent

Scientific and industrial forces

2024-07-04 10:44Published on the official account of "Science and Industry Power" under Shanghai Observer.com

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On June 30, the Tianlong-3 liquid launch vehicle developed by Tianbing Technology had a serious accident during a hot test run at the Comprehensive Test Center in Gongyi City, Henan Province, and the rocket broke away from the launch pad and fell into the mountain.

02 Tianbing Technology quickly released authoritative information after the accident, responded to the concerns of the media and the public in a timely manner, and said that there were no casualties.

03However, the cause of the accident was preliminarily determined to be the failure of the connecting structure of the test bench due to design, manufacture or installation, which was a low-level error.

04 Experts suggested that Tianbing Technology should summarize the lessons and re-determine the balance between efficiency and safety, zeroing and trial and error, and ensure that low-level mistakes are not repeated.

05At the same time, the industry needs to avoid vicious competition, establish a commercial aerospace industry association, share the latest technological achievements, and promote the healthy development of China's commercial aerospace.

Technical support is provided by Tencent Hybrid Model

On June 30, the major accident of the Tianlong-3 recyclable rocket must have been known to everyone. The statement released by Tianbing Technology more than three hours after the accident described the incident as follows:

At 3:43 p.m. on June 30, 2024, the Tianlong-3 liquid launch vehicle independently developed by Tianbing Technology carried out a hot test of a sub-stage nine-machine parallel power system at the Comprehensive Test Center in Gongyi City, Henan Province. During the test run, a sub-stage rocket ignited normally, the engine thrust reached 820 tons, due to the failure of the structure of the connection between the rocket body and the test bench, a sub-stage rocket detached from the launch pad, after liftoff, the rocket computer actively shut down, the rocket fell into the deep mountains 1.5 kilometers southwest of the test bench, and the rocket body fell into the mountains and disintegrated. The test site is far away from Gongyi City, and before the test, we jointly improved safety and security measures with the local government and organized the evacuation of surrounding personnel in advance.

Tianbing Science and Technology official Wei sent a letter of apology

Tianbing Technology's response can be described as rapid, providing specific information and clear conclusions of the accident in the first time, which eliminates the spread of rumors and the possibility of greater negative impact to the greatest extent. On July 2, Tianbing Technology issued another document to apologize for the fright caused by the accident to the citizens of Gongyi and the adverse impact on the commercial aerospace industry.

The crisis public relations of the heavenly soldiers is remarkable. As a result of the timely release of authoritative information, the response of the media and the public has been generally rational. Although, there are still a lot of skeptical voices on the Internet. While most people expressed shock and regret, they hoped that the pace of China's commercial space would not stop because of this. The public generally accepts the idea that astronautics is a high-stakes undertaking and that failures and setbacks are normal. Aren't Musk's Falcon Nine and Starship also blown up?

SpaceX 猎鹰9号火箭

However, the accident was truly unusual. The transformation of test runs into test flights can be said to be unheard of in the history of aerospace. If you're unlucky, the consequences will be dire. And the reason for the announcement of the Heavenly Soldier turned out to be an unbelievably low-level mistake. How did this happen?

Tianlong-3 is a large recoverable liquid rocket benchmarked against SpaceX's Falcon 9, with a diameter of 3.8 meters, a take-off mass of 590 tons, a low-earth orbit capacity of 17 tons, and a sun-synchronous orbit capacity of 14 tons. This is the main rocket tailored by Tianbing Technology for the construction of the mainland's giant Internet constellation, and the development progress is the fastest among the domestic recyclable rockets. There are high hopes for it. If this test goes well, then the first flight of orbit will take place in September.

Tianlong No. 3 in the Zhangjiagang plant of Tianbing Technology

Those who follow SpaceX know that the Falcon 9 and Starship often undergo a first-stage full-system static test run. This is the closest test to launch and verifies the operation of all subsystems at the same time, so problems can be identified efficiently, especially for reusable and recoverable rockets. It's so much in line with the business mindset for efficiency that it's not surprising that it's favored by SpaceX and China's commercial rocket companies.

China's aerospace has traditionally relied more on subsystem testing. But the national team is also keeping pace with the times in the new situation. They are also trying to use business thinking to improve efficiency. Earlier, on June 14, the Long March 10 three-plane parallel test was the largest test vehicle in China's aerospace history, with a total thrust of 382 tons.

On June 14, the Long March 10 completed the test run of a sub-stage rocket power system Source: China Aerospace Science and Technology Corporation

Musk's business thinking starts from first principles and has subverted many conventions formed in the aerospace industry for many years, such as multi-engine paralleling, vertical rocket recovery, methane propellant and stainless steel rocket body. Adopting the multi-machine parallel power test route recognized by SpaceX and the Chinese national team, Tianbing Technology's decision-making is no problem.

The steps of the heavenly soldiers are indeed very large. The first static test ran all 9 engines at once, and it was not throttled. The total thrust of 820 tons is more than ten or two times longer. However, high thrust is not a problem. Starship conducted three static firing in February and August last year, reaching about 3,600 tons of thrust with half of the engines throttled and a small number of engines failed to ignite. The question is, are the heavenly soldiers ready for thrust of this magnitude?

Apparently not.

The connection structure is not the crown jewel, it is a simple machine that can be done by Newtonian mechanics. At present, there is a patent for the connection structure of Tianbing on the Internet, which is completely consistent with the shape of the Gongyi test bench, and the bearing capacity is 600 tons. Some people speculate that the actual bearing capacity of the test bench is 600 tons. It may be that the person who decided the thrust of the test bench did not know much about the bearing capacity of the test bench, or the thrust was planned to throttle to 600 tons, but due to an operation error or engine control system failure, it was accidentally increased to 820 tons.

In fact, no matter what the situation, the test bench with a design bearing capacity of 600 tons should also be able to pull the first-stage rocket with a thrust of 820, because there is an extremely important factor in the engineering design, called the safety factor. The factor of safety refers to the ratio of the ultimate failure stress to the allowable stress. In mechanical or civil engineering, the minimum safety factor is not less than 1.5. In other words, a test bench with a bearing capacity of 600 tons will be able to pull a rocket with a thrust of less than 900 tons in any case. 820 tons, it should be easy.

Therefore, there should be no doubt that the cause of the accident officially announced by Tianbing is the failure of the connecting mechanism of the test bench due to design, manufacture or installation. It's also almost certain that this is a low-level error.

In the final analysis, the root cause of such low-level problems is often management and institutional negligence. The problem of management is often related to corporate culture. Dig a little deeper, and it has to do with the manager's personal style and way of thinking.

In recent years, China's commercial aerospace industry has shown a trend of rapid development. On the other hand, it's rolled up. Everyone understands that there will not be too many head companies left in the future. So benchmarking against SpaceX has become the simplest, most effective, and tried and tested strategy. The falcon IX-class recoverable rocket is currently the focus of competition. In the next three years, not counting the national team, there will be seven recoverable rockets making their first flights, three of which will meet or exceed the capacity of Falcon 9. Tianryu 3 is at the forefront.

Tianbing Technology Gongyi Test Bench Source: Tianbing Technology

It is understandable that many companies are looking for breakthroughs and are in a hurry. Driven by anxiety and impetuousness, it is inevitable that things that go against the spirit of science and do not respect objective laws will occur. The rapid development and rapid progress of Tianbing Technology have attracted a lot of attention. In my article last year, which took stock of China's commercial aerospace, I vaguely expressed my concerns.

However, in such an environment, enterprises also have a lot of difficulties. Radical innovation may also be a helpless choice. Something happened, isn't it too harsh to let Tianbing Technology take all the responsibility alone? Because such an accident has curbed the good development momentum of China's commercial aerospace, and it is not something we want to see.

For a better tomorrow for China's commercial spaceflight, we need to reflect. The word reflection has changed somewhat in recent years, and it seems to be tied to public knowledge. But I still want to say that we will always need objective, scientific and constructive reflection.

The following are the author's observations and suggestions.

As for the heavenly soldiers, it is necessary to conscientiously sum up the lessons and lessons, find out the problems in management and system, re-determine the balance between efficiency and safety, zeroing and trial and error, and ensure that low-level mistakes are not repeated. The pace of development should be adjusted based on the actual situation of the enterprise. Haste makes waste. More importantly, if there is a problem with the corporate culture, do not hesitate to change it. But keep the bold and innovative genes! Don't overdo it, if you are afraid of the straw rope for ten years because of safety issues, you will lose your vitality and future.

For the industry, it is possible to continue to roll, but vicious competition must be avoided. Bottomless poaching, plagiarism, and marketing hype are all poison. It is necessary to draw profound lessons from certain industries, prevent and guide them as soon as possible, and prevent problems before they occur. It is proposed to establish a commercial space industry association, and all companies will jointly develop and voluntarily join the commercial space industry convention, and commit to abide by a specific and feasible code of conduct. It is necessary to encourage mutually beneficial cooperation, share the latest technological achievements, and do not let the "open source horse" dominate.

For the competent authorities, we must continue to encourage innovation, and we must focus on the system to prevent major safety accidents, especially accidents caused by low-level mistakes that should not have occurred. It is proposed to establish an independent regulatory agency for space activities to conduct professional evaluation and approval of the site selection design and the development of various space activities of state-owned and private commercial space companies. This matter will inevitably be negligent in the separate examination and approval of the planning, environmental protection, launch, and measurement and control departments. It is unprofessional for the local government to do it. Professional things have to be done by professional people.

Tianlong-3 Source: Xinhua News Agency

If we take this as an opportunity to find out the causes of all the problems that have been exposed, make up for the gaps that have been discovered, and correct the mistakes without throwing away the advantages, then the bad things can definitely become good things.

I hope that one day in the future, when we talk about Gongyi's test run into test flight rocket in 24 years, we will say: This is an important turning point, the beginning of the maturity of China's commercial aerospace, and an unexpected coming-of-age ceremony.

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