"Fat Five" welcomes a broader stage, three "unique skills" help the aerospace power

The Long March 5 Y4 carrier rocket launches the Tianwen-1 Mars probe (Photo by Zhang Gaoxiang from the News and Publicity Center of the National Space Administration)

On the 23rd, accompanied by a deafening roar, the Long March 5 Yao-4 carrier rocket, developed and manufactured by the China Academy of Launch Vehicle Technology (hereinafter referred to as the Rocket Academy) under the China Aerospace Science and Technology Corporation, was launched from the Wenchang Space Launch Center in Hainan, successfully sending my country's first Mars probe, the "Tianwen-1", into the predetermined orbit. The launch mission was a complete success.

So far, the Long March 5 series of launch vehicles have successively carried out three types of missions: launching high-orbit large satellites, launching manned spacecraft test ships, and launching deep space probes. As the powerful member of the Long March rocket family, while helping to build a space power, the "Fat Five" will also build a bigger and broader stage for China's space industry.

Special skill 1: Launching a large satellite in high orbit - "bigger and stronger"

The Long March 5 carrier rocket is the first model of my country's new generation of carrier rockets to be developed. Its development goal is to significantly enhance my country's ability to enter space, and it is an important support and one of the significant signs of my country's progress from a space power to a space power.

The Long March 5 is a real "big guy". The core stage of the rocket has a diameter of 5 meters, and is bundled with four boosters with a diameter of 3.35 meters. The total length is about 57 meters, the takeoff mass is about 870 tons, and the takeoff thrust exceeds 1,000 tons. It uses clean fuels such as liquid hydrogen, liquid oxygen, and kerosene. The carrying capacity of the geosynchronous transfer orbit (GTO) can reach 14 tons.

Previously, my country's main rocket for launching high-orbit satellites was the Long March 3A series of rockets, which are known as the "gold medal rockets". Among them, the Long March 3B rocket with the largest carrying capacity has a geosynchronous transfer orbit (GTO) carrying capacity of about 5.5 tons, which can meet the launch needs of most of the current high-orbit satellites, such as Beidou navigation satellites, communication satellites, etc.

With the continuous development of satellite platforms, heavier satellite platforms have come out one after another, which has put higher requirements on the carrying capacity of rockets. For example, the Shijian-20 satellite, which was successfully launched by the Long March 5 Yao-3 rocket, has an operating orbit of geosynchronous orbit and weighs 8 tons, which is nearly 1.5 times the weight of previous high-orbit satellites.

A larger satellite platform means it can carry more and more advanced payloads. Satellites have more functions and stronger capabilities, and they also require larger-scale launch vehicles for launch. "The Long March 5 launch vehicle has a geosynchronous transfer orbit carrying capacity of about 14 tons, which is more than enough to launch an 8-ton satellite. If it is equipped with a suitable upper stage, it can also achieve the launch of multiple high-orbit satellites with one rocket," said Li Dong, chief designer of the Long March 5 rocket.

The emergence of the Long March 5 launch vehicle also provides more options for meeting the launch needs of future geosynchronous orbit satellites. For example, if the weight of a satellite is about 5 tons, it can be launched by using the Long March 3B rocket in a "one rocket one satellite" mode, or by using the Long March 5 rocket with an upper stage in a "one rocket two satellites" mode. Similarly, if the satellite is lighter, the Long March 5 rocket can send more satellites into orbit in one launch. The "battle-hardened" Long March 3A series rockets can provide high cost-effectiveness, while the powerful Long March 5 rocket is better at multi-satellite deployment.

The Long March 5 Y4 carrier rocket launches the Tianwen-1 Mars probe (Photo by Zhang Gaoxiang from the News and Publicity Center of the National Space Administration)

Special stunt 2: Launching a deep space probe - "traveling through the stars"

Exploring the vast universe has been the dream that the Chinese nation has been pursuing for thousands of years, and deep space exploration is the "key" to open the door of exploration.

Previously, the main research object of my country's deep space exploration was the moon. The Chang'e-1 to Chang'e-4 lunar probes were launched successively using the Long March 3A series of rockets, achieving the first two steps of the three-step goal of the lunar exploration project of "orbiting, landing, and returning". However, if a heavier probe is to be sent to the moon, or to the distant Mars, a rocket with a greater carrying capacity is needed, and only the Long March 5 rocket in the Long March rocket family can take the lead. Therefore, the Chang'e-5 lunar probe, which will carry out the third step of the lunar exploration project, will be launched by the Long March 5 rocket.

If the moon is the starting point of deep space exploration, then Mars exploration is the biggest hot spot. my country's Mars exploration mission plans to achieve orbiting, landing and patrol exploration of Mars through a single launch. Therefore, the "Tianwen-1" Mars probe carries a Mars rover, which can achieve soft landing and patrol exploration on the surface of Mars while orbiting and exploring. The diversity of the mission puts higher requirements on the launch capability of the carrier rocket.

The outstanding carrying capacity of the Long March 5 rocket has laid a solid foundation for my country's Mars exploration program. Compared with the previous lunar exploration, the launch of the Mars probe by the Long March 5 rocket this time has three characteristics.

First, the orbital entry speed is higher. The speed when the rocket separates from the probe will be higher than the second cosmic speed of 11.2 kilometers per second, allowing Tianwen-1 to escape the earth's gravity. This is also the first time that a Chinese rocket has reached this speed.

Second, the probe is heavier. The mass of the Tianwen-1 Mars probe is about 5 tons, which is more than one ton heavier than the Chang'e-4 lunar probe. It is the heaviest probe launched by my country so far.

Third, the launch orbit is more refined. In order to allow the probe to enter the orbit more accurately, the development team carried out a refined "narrow window multi-orbit" design, subdividing the 30-minute launch window every day into three 10-minute windows, corresponding to three launch orbits. A total of 42 launch orbits were designed during the 14-day window period, and automatic switching of launch orbits was achieved for the first time. "This is unique in the history of China's space launches, setting a record for the number of rocket launch orbits designed for a single launch," said Wang Jue, chief commander of the Long March 5 rocket.

Not only that, the emergence of the Long March 5 rocket makes it possible to fly to planets such as Jupiter and Saturn that are farther away from the earth.

Long March 5 Y4 carrier rocket on the eve of launching the Tianwen-1 Mars probe (Photo by Zhang Gaoxiang from the News and Publicity Center of the National Space Administration)

Special Skill 3: Launching Space Station Modules - "Private Customization"

The Long March 5B carrier rocket, which belongs to the Long March 5 series of rockets, is my country's first new generation large liquid carrier rocket with a one-and-a-half-stage configuration. It is also a rocket specially developed for the construction of manned space engineering space stations. It will provide "privately customized" launches for my country's space station core module and experimental module.

The Long March 5B rocket also uses a 5-meter diameter core stage and a 3.35-meter diameter booster, uses clean fuels such as liquid hydrogen, liquid oxygen, and kerosene, and has the largest fairing in China with a height of 20.5 meters and a diameter of 5.2 meters. Its height is equivalent to that of a six-story building, which is enough to accommodate the cabin of the space station. The total length of the Long March 5B rocket is about 53.66 meters, the takeoff mass is about 849 tons, the takeoff thrust exceeds 1,000 tons, and the low-Earth orbit (LEO) carrying capacity can reach 25 tons, making my country's rocket carrying capacity stand on a 20-ton platform and enter the world's first echelon. In order to meet the requirements of space station rendezvous and docking, the Long March 5B rocket also has a "zero window" launch capability. At the same time, its unique high-thrust direct-to-orbit technology and large-diameter cabin-rocket separation technology make it possible to directly send payloads into the predetermined orbit with only one stage of the rocket.

According to the "three-step" development strategy of my country's manned space program, the Long March 2F rocket, known as the "magic arrow", undertook the task of launching manned spacecraft and space laboratories, and successfully completed the mission objectives of the first two stages. The third step of the manned space program is to build a space station to solve the problem of large-scale, long-term manned space applications. The expansion of the scale of the space station also puts higher requirements on the capabilities of the launch vehicle. Take the core module of the space station as an example. It is 16.6 meters long and weighs more than 22 tons. Only the Long March 5B rocket can be launched. On May 5 this year, the Long March 5B rocket, which has been developed for nearly ten years, successfully completed its first flight mission, marking the first victory of the space station phase flight mission, and laying a solid foundation for the full realization of the third step development strategy of my country's manned space program.

There are two other types of Long March rockets involved in the manned space program. Among them, the Long March 7 rocket is a new-generation medium-sized carrier rocket developed for launching cargo spacecraft. It is responsible for transporting "space express" to the space station; the Long March 2F rocket is a renowned "magic arrow" and is currently my country's only manned rocket and the "exclusive rocket" for astronauts to enter space.

In the next two to three years, the "three heroes" of the Long March manned space program will jointly witness every step of my country's space station construction.

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