CZ-8 (Long March 8)

Among the conventional carrier rockets currently in service in China, the main sun-synchronous orbit rocket has a carrying capacity of 1 ton to 3 ton, and there is still a lack of a suitable rocket for the 3 to 5 ton class. Sun-synchronous orbit, also known as near-polar sun-synchronous satellite orbit, its orbital plane can rotate around the earth's axis, and the rotation period is consistent with the earth's revolution period. Therefore, whenever the satellite passes over the same place, it can always maintain the same sunshine conditions, which is very suitable for meteorological and earth observation. The familiar remote sensing satellites such as Fengyun Meteorological Satellite and Ocean Satellite generally use this orbit. It is expected that during the '14th Five-Year Plan' period, sun-synchronous orbit satellites will account for 50% to 60% of Chhina’s future satellite launches.

The medium-lift Long March 8 has a modular design and incorporates technologies that have been used by the Long March 3A and Long March 7. Its core level 1 and booster are the "same models" as the Long March 7, and the core level 2 is actually the third sub-level of the Long March 3A series rocket; Although the hydrogen-oxygen engine module of the Long March 8 is not exactly the same as that of the Long March 5, the reliability of the related technology has been proved after the 3 flights of the Long March 5 this year. The development of the Long March 8 follows the idea of 'modularization, serialization, and combination', inheriting the products and technologies of the in-service models, drawing on the results of existing tests and verification, and realizing the rapid integrated development of the models.

With two core stages and two boosters, the rocket is 50.3 meters tall, has a liftoff weight of about 356 tons, and is propelled by liquid oxygen, liquid hydrogen and kerosene. Its core stages are basically identical to those used by the Long March 7 and Long March 3A. It can transport a 5-ton spacecraft to a sun-synchronous orbit 700 kilometers above Earth, designers said. Launches will be conducted at the Jiuquan Satellite Launch Center in the Gobi Desert and Wenchang Space Launch Center in Hainan province. Long Lehao, a top rocket scientist at the China Academy of Launch Vehicle Technology, previously said the first stage and boosters of the Long March 8 will be recovered and reused.

China is planning to develop the next-generation CZ-8 (Long March 8) medium-lift carrier rocket and will conduct the first test flight by the end of 2018, Li Tongyu, the head of carrier rocket development at the China Academy of Launch Vehicle Technology said 27 February 2017. Li said use of the Long March 8 will extensively reduce the launch costs of low- and middle-orbit satellites, giving it bright prospects in the commercial launch market.

The core-stage of CZ-8 is based on CZ-7 and CZ-3A (Long March 3A) carrier rockets, the CZ-8 was expected to have two solid-propelled boosters with a diameter of 6.5 feet [this was not to be], the representative added. "…if everything goes well, its maiden flight will take place by the end of 2018," Li said, as quoted by the China Daily newspaper.

The rocket will be able to deliver a payload of about 4.5 metric tons to a sun-synchronous orbit, or 2.5 tons to geosynchronous transfer orbit, according to Li. The China Academy of Launch Vehicle Technology, the parent company of the the China Aerospace Science and Technology Corporation, is the leading space launch vehicle manufacturer in China.

National Aeronautics and Space Administration (CAA) reported on the 26 September 2016 for the first time on a formal occasion, "Long March No. 8", and said it would speed up the implementation of Mars exploration. Long March 8 launch vehicle (English abbreviation: LM-8 or CZ-8) is a major carrier of the mainland launch satellite synchronous orbit satellite. The design of the launch vehicle will be based on the sun's long-range series of long-range solar synchronic orbit carrier rockets (such as the Long March 3).

National Defense Science and Technology Bureau Chief Engineer, National Aeronautics and Space Administration Secretary-General Tian Yulong said that the red belt, the current mainland space technology capacity has entered the ranks of the world's advanced.

This is the first time that the National Defense Science and Industry Bureau had mentioned "Long March 8" on a formal occasion. Previously, the CPPCC National Committee members, Aerospace Science and Technology Group China Launch Vehicle Technology Research Institute of the former party secretary Liang Xiaohong during the two sessions in 2015 revealed that as a new type of solar synchronous orbit rocket, Long March 8 was in the demonstration stage. Tian Yulong said that this year is China Aviation Planning Year, the National Defense Science and Technology Bureau will be completed to complete the "aerospace development" in the thirteenth five year plan for space science released in the 2016 "China's flight space" White paper, organized the completion of China's first "aerospace law" draft preparation work.

The take-off stage has been developed for eight years in the Long March 7 project, and the 3-meter-diameter high-altitude second sub-stage has undergone more than 100 launches in the Long March 3A series rocket project, which fully absorbs the current and new-generation carrier rockets. The first stage is equipped with two YF-100 liquid oxygen kerosene engines, and the second stage is equipped with two YF-75 high altitudes. Hydrogen-oxygen engine, one sub-class bundles two 2.25m diameter boosters, each booster is equipped with a YF-100 liquid oxygen kerosene engine. The thrust-to-weight ratio of the Long March 8 is as high as 1.39, which is the highest thrust-to-weight ratio of all rockets in service in China. The YF-100 has a rated thrust of 124.7 tons, and the take-off thrust of the entire arrow is about 498 tons. The high thrust-to-weight ratio means that it can have more capacity under the same take-off weight.

In the past, the development of new-type rockets required the manufacture of a large number of test pieces for actual tests. At the same time, it was necessary to build a large-scale shaking table matched with the rocket, which was time-consuming, labor-intensive and cost-intensive. Long March 8 abandoned this traditional model, and replaced it with a short test cycle and low cost for online testing based on modal analysis technology based on virtual technology. The model is more accurate and the deviation is smaller.

The Long March 8 will also adopt the "two levels and one vertical" model, that is, horizontal assembly, horizontal overall transportation, and vertical transition and docking of the spaecscarft cover assembly to explore the realization of the rapid launch of China's carrier rockets. It is expected that around 2022, the integrated Long March 8 rocket will achieve "two levels and one vertical", which can simplify the construction scale of the launch site. The launch area no longer requires a large and complex tower and reduces construction costs.

The triple vertical mode is more friendly to the working conditions of the rocket, but the disadvantage is that it occupies the mobile launch pad during the entire test and launch cycle of the rocket, which is not conducive to the improvement of the rocket launch efficiency.

Although the three-level model has higher requirements for the rocket working conditions, it also brings the convenience of the test and launch work. The rocket is sent to the launch pad by road transportation for lifting, and then the transport platform can undertake the next mission. The rocket is in the horizontal assembly , During the horizontal test, the launching station is not occupied, and the launching station is occupied for the shortest time, which is very conducive to high-density launch.

The entire test and launch cycle of the Long March 8 is only 7 to 10 days. Compared with the current test and launch cycle of large liquid rockets, which is more than 20 days, it is a leap forward.

Fast manufacturing is another core advantage. By the following year (2022), this type of rocket will have an annual production capacity of 30.

According to Duan Baocheng, deputy commander-in-chief of the Long March 8 launch vehicle, the Long March 8 has established market demand-oriented development at the beginning of the project, fully considering the integration of technology and economy, and through trials including project system and high inheritance, Realize effective control of rocket costs.

"Long March 8 has a carrying capacity of 5 tons and a take-off scale of 356 tons. The carrying efficiency is among the best among domestic rockets, and it will inevitably bring high cost performance." said Duan Baocheng. "In the next 5 to 10 years, there will be strong demand for large-tonnage space launch missions in sun-synchronous orbits, and the Long March 8 has emerged as the times require. It is the first nationally-approved launch vehicle for the commercial market. While carrying out low-cost design in aspects such as, structure, etc., by carrying out vertical take-off and landing research, it can be reused and further reduce costs." Qian Hang said.

In the future, by adjusting the number of boosters, Long March 8 will also develop different carrying capacities, achieve serial development, and continue to iteratively optimize, becoming the main rocket in China's medium and low orbit satellite launch market, and providing powerful support for China's subsequent satellite networking projects. support.

Since the 1980s, China has been planning for a new generation of launch vehicles, and has gradually formed a development plan for the new generation of small, medium and large launch vehicles. The launch mission of a new generation of carrier rockets during China's space "13th Five-Year Plan" period has successfully concluded.

At 12:37 noon on 22 December 2020, the Long March 8 carrier rocket developed by the China Academy of Launch Vehicle Technology affiliated to China Aerospace Science and Technology Corporation was successfully launched at the Wenchang Space Launch Site in China with "one arrow and five stars". This is the first flight mission of China's new generation of medium-sized carrier rocket Long March 8, and also the 356th flight of the Long March series of carrier rockets.

Xiao Yun, commander-in-chief of the Long March 8 launch vehicle, said that the success of the first flight of the Long March 8 will strongly promote the upgrading of China’s medium-sized launch vehicles, and will drive and traction the development of China’s future medium and low orbit satellites to meet the needs of future medium and low orbit high The demand for density launch missions is of great significance to the building of a space power. Xiao Yun introduced that China’s current main carrier rocket capable of launching in low-medium orbits can deliver 3 tons of payload to sun-synchronous orbit. The Long March 8 has increased this capacity to 4.5 tons. This is an increase in the capacity of the Long March series of carrier rockets. It will also be a platform upgrade for payloads such as satellites.

"On the sun-synchronous orbit, the Long March 8 with a carrying capacity of 5 tons will form a more optimized and reasonable capacity layout with the new generation of launch vehicles such as Long March 5, Long March 6, Long March 7, and Long March 11. This will greatly enhance China's aerospace capabilities in and out of space." Xiao Yun said.

The China Academy of Launch Vehicle Technology affiliated to China Aerospace Science and Technology Corporation at 11:06 on 27 February 2022 launched the Long March No. 8 Yao-2 carrier rocket (also referred to as the "Changba Yao-2 Rocket") ignited and took off at the Wenchang Space Launch Site in Hainan, and then successfully sent the 22 satellites lifted into the predetermined orbits, and the launch mission was a complete success , creating the highest record of China's launch of multiple satellites with one arrow.

The Changba rocket, which successfully flew for the first time in December 2020, is China's new generation of main medium-sized launch vehicles, filling the capacity gap of China's sun-synchronous orbit carrying capacity of 3-4.5 tons, and can undertake more than 80% of medium and low-orbit launch missions. The launch of the Changba Yao No. 2 rocket is the first flight of a new generation of carrier rockets in 2022, the first launch of our academy's space mission in 2022, and the first flight of a new configuration without boosters.

Chen Xiaofei, the deputy chief designer of the Long March 8 rocket, said that compared with the Yao-1 rocket, the biggest difference in the shape of the Chang-8 Yao-2 rocket is the cancellation of two boosters, from a two-stage and a half configuration to a two-stage configuration. cascade configuration. It took only one year for the development team from the successful first flight to the completion of the final assembly and testing of the remote 2 rocket and the factory conditions. This is due to the "modular" and "combination" design ideas adopted by the rocket. As early as the beginning of the development, the designers fully took into account the state of the rocket without a booster, and incorporated it into the assessment envelope of the Yaoichi rocket. Therefore, the Haruka 2 rocket does not need to make large-scale changes, but only needs to adapt to the load and flight trajectory to efficiently meet the mission requirements.

The launch of 22 satellites with one arrow set a record for the largest number of satellites launched in China at one time. However, in order to safely and successfully deliver so many satellites to their destination at one time, the layout problem of the "passengers" in the fairing must first be solved. The developers fully sorted out the structure and mission requirements of the satellites, and innovatively designed a three-layer multi-satellite distributor, which can arrange a comfortable "seat" for each satellite within the limited fairing space, and can ensure that the satellites are different The separation of directions is safe.

"A total of 22 stars have to be separated for this mission, and a total of 12 separations have been completed, setting a new record in China's aerospace industry. It can be said that the Changba rocket in the separation of the stars and arrows is like a 'ballet', and the final release of 22 stars It's like 'the goddess scattered flowers'," said Duan Baocheng, deputy commander-in-chief of the Rocket Long March 8 launch vehicle.

Not only that, after the development team completed the design of the multi-satellite distributor, it specially carried out the joint operation test of the satellite and the arrow. During the test, the installation operation sequence and layout position of the satellites were adjusted, and the satellite-rocket was adjusted through multiple rounds of simulation calculations. The separation action has been optimized to ensure the safety of the whole process of the satellite from "getting on" to "getting off".

It is worth mentioning that the height of the fairing of the rocket of the present invention has also been shortened from 8 meters to 5.4 meters, which reduces the load on the key parts of the whole rocket. In this way, the release conditions for rocket launch can be appropriately relaxed, which is conducive to improving the launch probability of the mission, thereby further improving the mission adaptability of the rocket.

The Changba Yao No. 2 rocket is also a "shared rocket", carrying 22 satellites from 7 research and development units. Xiao Yun, the commander-in-chief of the Long March 8 launch vehicle, introduced this new sharing model vividly. "Simply put, it is a carpooling scheme that provides users with affordable launch services, and the threshold is greatly lowered."

In addition, because it is a shared launch, it needs to connect with multiple user units, and the coordination work is multiplied. In the face of difficulties such as iterative update of users and repeated plans during the development process, the development team continues to carry out plan adjustment, feasibility and safety analysis, with enthusiasm The service awareness of the company finally contributed to the implementation of this task. With the successful exploration of the Changba Yao 2 rocket, the institute also plans to promote the normalization of shared launches.

Xiao Yun said: "In the future, the demand for human beings to enter space is increasing. As a 'national team', we have the responsibility and the ability to achieve the common prosperity of the space economy through our efforts and accelerate the construction of a space power."

To achieve repeated use of rockets, engine thrust adjustment is an important technology. In this launch, Long March 8 applied the engine thrust adjustment technology, which is the first engineering application in China's launch vehicle. It has carried out relevant preliminary technical verifications for the subsequent reuse technology in advance, laying a solid foundation for the development of China's reusable launch vehicle.

The Long March 8 is the "first mover" of the Long March family to explore rocket reuse technology. There are several technologies that must be overcome, including engine thrust adjustment technology, landing buffer technology, and control (landing speed) technology. Engine thrust adjustment is equivalent to "reducing the throttle" when returning the rocket. The Long March 8 throttling control of the liquid rocket engine during flight is the first engineering application in China's launch vehicle.

Only when the engine thrust is reduced can the rocket be controllable, well controlled, and able to return. "For example, the weight of our rocket at the time of recovery is only 40 tons, but the rocket has 4 engines and each engine has a thrust of 120 tons. Even if you turn off 3 of them, one has 120 tons of thrust; the mass of 40 tons, With a thrust of 120 tons, the thrust is greater than the mass, and the rocket will be pushed upwards, making it difficult to achieve landing recovery.