This handsome "tall guy" is extraordinary

  Wu Yongjiang reporter An Puzhong Wang Lingshuo Yue Yutong

  On March 12, 2021, at the Wenchang Space Launch Site in China, with a gorgeous tail flame across the sky, the Long March 7A carrier rocket ignited into the air, successfully sending the test 9 satellite into its intended orbit.

  The successful launch of the Long March 7A carrier rocket opened the curtain for the launch of my country's new generation of carrier rockets in 2021, marking the addition of a new member of my country's new generation of medium-sized carrier rocket family.

  Today, let us approach the new member of the "Long March Family"-Long March No. 7A.

  "Brothers" mission is very different

  As the "new member" of the Long March VII series of launch vehicles, the Long March VII A has distinct family characteristics and is also a handsome "tall man."

But by careful comparison, people will find many different places.

  As the "brother" of Long March 7, Long March 7A has a total length of 60.1 meters, which is 7 meters higher than Long March 7.

  It turned out that the Long March VII was a rocket with a "two and a half" configuration, while the Long March VIIA was a rocket with a "three and a half" configuration, and the latter had an extra third stage.

  The so-called "two and a half" refers to the "half stage" of the rocket's core first, core second and booster.

Long March No. 7A as a "three-and-a-half level", naturally there is an extra "core three-level".

The extra "core three-stage" module is mainly to provide the power for the Long March VIIA to fly to a higher orbit.

  In order to better complete the mission of future high-orbit satellite launches, the column height of the Long March 7A fairing column is 5.5 meters, which is a bit shorter than the height of 8 meters of the Long March 7 fairing column.

This change is due to the fact that the rocket payload has changed from a cargo spacecraft to a satellite.

  Speaking of this "new member", Meng Gang, the commander of the rocket project, is quite proud.

In March 2018, the development team began to deepen the demonstration of the rocket program.

In December 2019, this type of rocket completed the factory review.

It can be said that it is a "three-and-a-half-stage" rocket formed on the basis of the Long March 7 and combined with the three sub-stages of the Long March 3A series rockets. It is the main configuration of my country's new generation of medium-sized carrier rockets.

Its successful development fills the gap in the carrying capacity of my country's carrier rocket from 5.5 tons to 7 tons in geosynchronous transfer orbit.

  If Long March VII is the representative of my country’s new generation of medium-sized carrier rockets and has won the title of "freight train" for manned space stations, then Long March VIIA is a "high-orbit recruit" who fills the gap in carrying capacity.

  "The successful launch of Long March 7A has further enriched the type spectrum of the Long March series of carrier rockets. It has not only realized the upgrading of my country's medium-sized carrier rockets, but will also forcefully drive and traction the upgrading of my country's future large and medium-sized satellites." Meng Gang Say.

  "Three Breakthroughs" Achieve Good Skills

  Although the Long March VIIA inherits the mature modules of the Long March VII and the Long Three A series of rockets, the development process is by no means a simple "building blocks."

  "The development team has successively achieved'three breakthroughs' in key technologies, laying the foundation for the successful launch of the rocket." said Fan Ruixiang, chief designer of Long March 7A.

  One of the key technological breakthroughs-rocket attitude control technology with large slenderness ratio.

  The Long March VIIA has a slender appearance and is the rocket with the largest slenderness ratio in my country's Long March series.

This adds a lot of difficulty to the rocket's attitude stability control.

  According to Shen Dan, the overall designer of Long March No. 7A, daily experience tells us that most thin and long hard things are easy to break, and the same is true for rockets.

It is manifested in the Long March No. 7A, which is its basic frequency is reduced.

Therefore, the coupling effect of the rocket due to factors such as propellant sloshing is more obvious.

  In order to solve this problem, the development team adopted the method of "moving flowers and trees" to use the old products of the Long March 7 joint training arrow and the Long March 3 A craft storage box to assemble a full-arrow modal rocket.

Through the whole rocket modal test, the elastic frequency of the rocket is mastered.

On this basis, the development team carried out the design of the attitude control parameters of the control system, and through mathematical simulation and semi-physical simulation verification, to ensure that the rocket attitude stability and control accuracy meet the requirements of the mission.

  The second breakthrough of key technology-high-precision high-altitude wind field measurement quasi-real-time two-way wind correction technology.

  When the slender rocket penetrates the atmosphere, it will be disturbed by the high-altitude wind at all times, and there is a risk of "breaking down" after taking off.

In response, the research team has developed a high-precision high-altitude wind field measurement quasi-real-time two-way wind correction technology.

This technology can adjust the attitude of the rocket through the atmosphere according to the high-altitude wind measured several hours before launch, so that it can "head wind forward" along the best path, thereby reducing the risk of the rocket breaking.

  The third breakthrough of key technology-Guidance and control technology that adapts to typical failure modes.

  A data in the field of international aerospace shows that the failure of the rocket's flight is due to the failure of the power system accounting for about half.

How to realize the "resurrection" of the rocket through the adaptive control system under the condition of failure has become a hot topic in the aerospace industry in recent years.

  Through active exploration, the research team adopted a more intelligent guidance method on the Long March 7A-guidance and control technology that adapts to typical failure modes.

The rocket will plan an optimal flight path by itself based on information such as position and speed.

The application of this technology has enabled my country's rocket control technology to reach the international advanced level.

  In addition, Long March 7A also uses the boost non-separation and core-level non-sway technology.

The boosters of most rockets in the world will be separated from the first stage after the mission is completed, and the same is true for other Long March series rockets in our country.

With this technology, Long March VIIA can reduce a set of separation mechanism, greatly reduce the complexity of the separation system, and improve the reliability and economy of the rocket.

This is the first time in the world.

  "New members" will give new uses

  "The successful launch of the Long March 7A is an important milestone in the development of the rocket. But this is only a new starting point. The follow-up work still has a long way to go, and we still need to work hard." Meng Gang said.

  Since Long March VIIA can meet the high-density launch requirements of medium and large high-orbit satellites, it will be in geosynchronous orbit in the future with the Long March III A series rocket with a carrying capacity of 5.5 tons, and the Long March 5 with a carrying capacity of 14 tons. Together, the formation of a more optimized and reasonable distribution of carrying capacity, and vigorously enhance China's space into space.

  According to my country's carrier rocket upgrade strategy, the new generation of carrier rockets will initially realize the upgrade of existing rockets around 2025.

According to the current mission schedule, the Long March 7A mission will be fully scheduled before 2025, with 3 to 5 launch missions to be carried out each year.

  In the future, the development team will also develop a larger diameter fairing configuration for the Long March 7A based on the mission requirements; based on the Long March 7A, through the addition of upper-level programs, the launch of a zero-degree orbital inclination satellite will be implemented to perform lunar exploration. , Fire detection and asteroid detection and other deep space exploration missions.

It will gradually become a basic type of my country's medium-sized high-orbit rockets, undertake a number of major national tasks, and provide a solid guarantee for the construction of my country's aerospace power.

  "In fact, innovation is also the common "family style" of the Long March rocket family." Fan Ruixiang said that as early as the beginning of the aerospace industry, astronauts relied on self-reliance and created the historical cause of "two bombs and one satellite".

Similarly, through the bold innovations of several generations of astronauts, China Aerospace has successively achieved many world-renowned achievements such as manned spaceflight, lunar exploration, and Beidou project.

  The road to dream pursuit is heavy and the road to innovation is endless.

Based on a new starting point, the development team of the new generation of carrier rockets will continue to struggle and make big strides towards the goal of building a space power!