Completed 10 launches in two months
Want to make Chinese rockets more powerful rely on these "god operations"
Recently, China Aerospace is very busy. From May 5th to July 9th, 10 launches were carried out. The Long March 5B, Kuaizhou 1A, Long March 11 and other carrier rockets were successively launched. Performed a new generation of manned spaceship test ship and the launch mission of multiple satellites.
As we all know, rockets are vehicles used for space activities. Just as there are different types of cars on the ground, rockets are also divided into different models. The "strength" varies from large to small. According to their own characteristics and carrying capacity, they perform different tasks.
So, how are rockets classified according to carrying capacity, what are the characteristics of different types of rocket engines, and how can the rocket's carrying capacity be improved? Qian Hang, a model designer of the First Academy of China Aerospace Science and Technology Corporation (hereinafter referred to as the First Academy), introduced the reporter of Science and Technology Daily using the Long March series of launch vehicles as an example.
Different types of rockets have their own advantages
On May 5th of this year, the Long March 5B carrier rocket was launched at the Wenchang Space Launch Site in my country and made its debut. In the future, this type of "big rocket" will play an important role in the construction of China's space station.
Calling the Long March 5 the "Big Rocket", it's not just pointing. Qian Hang said that according to the size of the carrying capacity, the launch vehicle can be divided into four categories: small, medium, large and heavy (super heavy). Different types of rockets have their own advantages.
At present, there is no unified quantitative standard for this classification method. my country's aerospace industry generally regards the launch vehicle with a near-Earth orbit carrying capacity of 20 tons to 100 tons, and its derivative configuration is called a large launch vehicle.
The Long March 5 series of my country's new generation of large launch vehicles, developed by the First Academy, has launched two configurations. The Long March 5B is a first-and-a-half stage rocket. It is the only rocket in active service in my country that can be launched into orbit without separation between stages, and its reliability has been greatly improved. At the same time, it has a low-Earth orbit carrying capacity of over 22 tons. These characteristics make it the best choice for undertaking the launching mission of the space station module of our country. The basic model of the Long March 5 is a two-stage half-configuration rocket. Although its low-Earth orbit carrying capacity can reach more than 25 tons, its mission is mainly aimed at deeper space.
The carrying capacity of the Long March V rocket's geosynchronous transfer orbit is about 14 tons, and it can undertake the launch of a large-scale communication satellite based on the Dongfanghong V platform. The rocket also has an earth-moon transfer orbit carrying capacity of more than 8 tons, and a ground fire transfer orbit carrying capacity of about 5 tons. According to the plan, my country will launch the Tianwen-1 Mars probe and Chang'e-5 lunar probe with the Long March V rocket in 2020.
The carrying capacity of medium-sized launch vehicles in low-Earth orbit is usually 2 to 20 tons. In the Long March rocket family, this category of rocket lineup is huge. It has undertaken all Beidou satellite and Chang'e series detector launch missions, and is known as the "Golden Rocket" long top three series launch vehicle; completed the 11 Shenzhou spacecraft and the launch of the Tiangong 1 and 2 space laboratory Long March 2F Rockets; as well as the new generation carrier rocket Long March VII, which is mainly used for launching cargo ships in future space station missions, are representatives of China's medium-sized rockets.
Those with a low-Earth orbit carrying capacity of less than 2 tons are called small launch vehicles. Don't underestimate them. In today's increasingly prosperous microsatellite market, "little rockets" also make a big difference. Taking China's new generation of small launch vehicle Long March 11 as an example, as the first solid launch vehicle in the Long March rocket family, its near-Earth orbit carrying capacity is about 700 kg, and the 700 km solar synchronous orbit carrying capacity is about 400 kg. The ability to complete technical preparations and launch within 24 hours of receiving a mission order can meet the needs of rapid and mobile satellite launches in emergency situations.
In addition, with low, medium and high orbit launch capabilities, near-Earth orbit carrying capacity of more than 100 tons, takeoff thrust up to 3,000 tons, it is a heavy carrier rocket, its representatives include the United States used to perform the Apollo manned mission to the moon The Saturn V rocket, developed by the Soviet Union, has maintained the world record of carrying capacity and so on.
Solid and liquid engines are not distinguished
In recent years, in the face of increasing demand for space resource development and increasingly fierce competition in the commercial launch market, my country has developed a new generation of large, medium, and small launch vehicles with four models, including the Long March 5. Qian Hang said that the new generation of carrier rockets are designed with reliability, safety and economy as the main principles, and are non-toxic, environmentally friendly, cheap, and specific impulse (a description of the efficiency of rocket propellant utilization, referring to the amount of propellant produced The higher the impulse) liquid hydrogen, liquid oxygen or liquid oxygen kerosene engine. So does this mean that liquid fuel engines are better and more powerful than solid fuel engines?
Qian Hang said that the advantages of liquid fuel engines are high fuel energy density, large specific impulse, easy flow control, and can be used for maneuvering or orbit change. However, liquid fuel is not easy to store, and most of them need to be refilled before the rocket is launched. The unsymmetrical dimethylhydrazine and nitrous oxide fuels used in China's traditional liquid fuel engine rockets are highly toxic, highly corrosive, flammable and explosive, and very dangerous. They have extremely strict requirements for storage and refueling. . In recent years, my country's new generation of launch vehicles have adopted green fuels such as liquid hydrogen, liquid oxygen, and kerosene, which have basically no impact on the environment, but storage and refueling are more complicated.
The basic principle of a solid fuel engine is to ignite the pellets and produce a large amount of high-temperature gas from the nozzle to propel the rocket forward. Compared with the gunpowder toy "Sky Monkey" born in the Song Dynasty, its structure and principle have not changed much. Qian Hang introduced that solid fuel engines have three main advantages. First, compared with liquid fuel engines, it does not require a complicated mechanical structure such as a fuel pump, and the structure is simpler and cheaper. Secondly, because the pellets exist in solid form, their characteristics are more stable than liquid fuel, and they are also stored more. Safety; in addition, due to the simple structure, the solid fuel engine can be made very light, and it is easier to miniaturize. But solid fuel engines also have their disadvantages. For example, the combustion time is relatively short, the specific impulse is small, the ignition cannot be repeated, and the thrust adjustment is difficult. This has restricted the adaptability of its tasks.
The form of the rocket engine is neither good nor bad, nor can it determine the carrying capacity of the rocket. Although the current domestic solid fuel engine launch vehicles such as the Long March 11 and the Kuaizhou-1A developed by the China Aerospace Science and Industry Corporation are small launch vehicles, they are also equipped with the SLS heavy launch vehicle being developed in the United States. The world's most powerful solid fuel rocket engine.
4 measures can effectively improve rocket capacity
Carrying capacity is the most direct and important parameter index of rocket performance. Qian Hang said that the rocket's capacity is mainly determined by the rocket's overall design level, engine performance and manufacturing level, arrow body structure design and manufacturing level and other factors.
He said that to improve the rocket's carrying capacity, there are four main measures. The first is to increase the propellant by optimizing the ratio between stages (the mass of the i-th rocket divided by the mass of the i+1-th rocket is one of the parameters that affect the ideal speed of the rocket) while keeping the rocket configuration unchanged. The amount of filling. The Long March 3A series, the European Ariane 5 series, and the US Falcon 9 launch vehicle have all adopted this measure to significantly increase their carrying capacity.
Structural optimization and weight loss is the eternal theme of the vehicle design. In the launch of the Asia-Pacific 6D satellite launch mission on July 9 this year, the Long March 3B carrier rocket increased its carrying capacity by 50 kg through weight reduction to meet the launch requirements. Qian Hang introduced that in the early stage of the design and application of the vehicle, the main purpose is to improve the structural efficiency by improving the process, selecting new materials, and optimizing the force transmission path. The rocket has higher requirements for the lightweight design of the arrow body structure system. After a lot of simulation calculations and experiments, the rocket technical team of the First Academy proposed the main binding and engine concentration "double diffusion" structure, and the super-atmospheric bottle deformation adaptive support structure. , Bundled lifting multi-functional integrated structure and many other new lightweight design schemes, with good results.
The performance of the engine directly affects the rocket carrying capacity. In the capacity improvement measures of the US Space Shuttle and Falcon IX rocket, improving engine thrust and specific impulse is one of the important links. my country has used the first expansion cycle power mode hydrogen-oxygen engine developed on the Long March V carrier rocket, which is the rocket engine with the highest specific impulse performance in the world and has the ability to start at high altitude multiple times.
In addition, the overall optimized design is also an effective way to improve the rocket's capacity. Qian Hang said that from the perspective of the overall configuration of the rocket, you can use a high-thrust engine as the basic power as much as possible, choose a high specific impulse engine for the upper stage, and carry out joint design of the load attitude control to reduce the structural load conditions, which can effectively improve the rocket delivery. ability.
Our reporter Fu Yifei