Introduction To The Development Of Filament Winding Technology And Its Application In High-Precision Fields

 

 

Introduction to the development of fiber winding technology and its application in high-precision fields

 

As an advanced material, composite materials have a very broad development space. Advanced composite materials have a series of advantages such as light weight, high specific strength, high temperature resistance and corrosion resistance. They are widely used in aerospace, defense equipment and energy development, and have promoted the rapid development of related industrial fields.

 

The wide application of composite materials depends to a large extent on the molding process of composite materials. Among them, winding and laying technology is the fastest and most effective composite molding technology in recent years.

 

 

Fiber winding technology is a process in which continuous fibers or cloth tapes soaked in resin glue are wound onto a core mold according to a certain rule, and then cured and demolded to obtain the product. According to the different physical and chemical states of the resin matrix during fiber winding molding, it is divided into three types: dry winding, wet winding and semi-dry winding. Among the three winding methods, wet winding is the most commonly used; dry winding is only used in high-performance, high-precision cutting-edge technology fields.

 

my country’s fiber winding technology has gone through more than half a century of development, from scratch to large, and has continued to grow along with the development of my country’s aerospace and national defense.

 

The Birth Of Fiber Winding Technology

 

In the early 1960s, according to the needs of national military industry and national economic development, Harbin FRP Research Institute Co., Ltd. (formerly Harbin FRP Research Institute) and Beijing FRP Institute Composite Materials Co., Ltd. (formerly Beijing 251 Factory) respectively carried out research on fiber winding technology.

 

In 1964, Harbin FRP Research Institute proposed the basic law of spiral fiber winding (i.e., the tangent point method) and gave the mathematical expression of this law, i.e., the calculation of winding speed ratio; it was the first time in China that the fiber trajectory on the head surface was located in a plane, which successfully solved the problem of calculating the center angle of fiber winding on the head surface, and provided a theoretical basis for the design and process design of the winding machine.

 

Based on this law, Harbin FRP Institute designed and manufactured a mechanical winding machine, as shown in Figure 1. Using these equipment, several types of pressure vessels have been developed, realizing the mechanization of my country’s fiber winding process.

 

At the same time, breakthroughs have been made in key technical issues such as the structural design of winding products, raw material selection and anti-seepage lining. In 1964, Beijing Institute of Glass and Steel Composite Materials Co., Ltd. realized the winding of the standard line (then called “North Star winding”) (i.e. the standard line method), summarized the general formula of the winding law, established the motion equation of the geodesic winding law, and described the relationship between the quantities in a line.

 

By 1965, my country had fully mastered the basic law of spiral winding and realized fully mechanized spiral winding. China’s fiber winding technology was officially born in the early 1960s.

 

 

 

Development Of Filament Winding Technology

During the 20 years from the 1970s to the late 1990s, my country conducted a comprehensive study on filament winding technology. The basic laws of filament winding and the laws of special-shaped winding were explored, the development of mechanical filament winding equipment was improved, and the design, manufacturing process, structural calculation and performance testing of filament winding products were studied. During this period, the comprehensive development of filament winding technology was mainly reflected in the further exploration and improvement of theory and the research and development of equipment.

 

Theoretical Exploration and Improvement of Filament Winding Technology

In 1975, Beijing Glass Steel Institute Composite Materials Co., Ltd. derived the design calculation formula for filament winding internal pressure vessels and the formula for calculating the winding angle of the vessel head. In 1987, the computer program of the motion equation group of the winding machine was successfully compiled, which made the motion design and implementation of the winding law of gas cylinders and other rotating products more perfect and scientific, and provided a basis for the motion design of mechanical winding machines and the software design of computer-controlled winding machines.

 

In 1965, my country fully mastered the winding law and the winding speed ratio calculation method, and realized the mechanization of spiral winding. Since 1971, Harbin Glass Research Institute has started to study the winding of special-shaped parts, and proposed the principle of “equivalent circle assumption” for the cross section of special-shaped parts, which solved the approximate calculation problem of fiber winding of special-shaped parts.

 

In 1987, the calculation principle of fiber winding of grid structure was proposed. The realization of this new technology not only solved the key technology of a certain satellite, but also marked that my country’s fiber winding technology has entered a new stage of development. From 1996 to 1998, a new type of non-geodesic-quasi-geodesic path algorithm was proposed, which is mainly used for the design of stable trajectory of fiber winding of rotating bodies.

 

Harbin Glass Research Institute conducted the first research on special-shaped winding technology in China in 1971, including the winding of non-rotating bodies with polygonal equal cross-sections, winding of variable cross-sections, and winding without end heads without end heads, as shown in Figure 2, and proposed the principle of “equivalent circle assumption” for the cross section of special-shaped products, which solved the approximate calculation problem of fiber winding of special-shaped product cross-sections.

 

In 1978, Harbin FRP Research Institute first proposed the “Basic Theory of Non-geodesic Stable Winding” and gave the specific calculation formula of non-geodesic stable winding of cylinders; in 1985, Harbin FRP Research Institute first proposed the use of continuous fiber winding method to manufacture reinforced frame composite material structure in China, and derived the “grid structure fiber winding calculation principle”, and first proposed the use of continuous fiber winding method to manufacture reinforced composite material structure in China. The realization of this technology marks that my country’s fiber winding technology has entered a new stage of development.

 

 

Research And Development Of Fiber Winding Equipment

 

Harbin FRP Research Institute Co., Ltd. imported a large hydraulic servo CNC W250 CNC winding machine from Germany in 1974, which was the first time that my country introduced fiber winding equipment from abroad.

 

 

Beijing Institute of Glass and Steel Composite Materials Co., Ltd. successfully developed a digital program-controlled electro-hydraulic servo fiber winding machine (SYC-250) based on WE-250. Beijing Institute of Glass and Steel Composite Materials Co., Ltd. also developed X1 and X2 planetary fiber winding machines;

 

From 1975 to 1978, Harbin Institute of Construction Engineering (now Harbin Institute of Technology) and Wuhan Institute of Building Materials (now Wuhan University of Technology) successively developed step-by-step 8-petal continuous tube winding machines and cam-driven steel belt continuous tube winding machines;

 

From 1984 to 1997, Harbin Institute of Glass successfully developed spherical and annular winding machines, and developed fiber-wound spherical and annular products, as shown in Figure 4, which were used in the aerospace field.

 

 

 

Figure 4 Spherical winding machine and monopolar hole spherical and annular products

 

In 1985, Harbin Institute of Technology successfully developed a multi-coordinate high-performance winding machine prototype and a 3,4-coordinate closed-loop microcomputer numerical control winding machine, and developed a winding software package with a non-geodesic mechanism.

 

In 2000, a six-axis microcomputer-controlled winding machine was successfully developed. This achievement marks that my country has made great progress in fiber winding technology, control software and hardware.

 

By the end of the 1990s, my country’s fiber winding technology entered a period of comprehensive development. Fiber winding technology began the industrial production stage of glass fiber reinforced plastics industries such as pipes and tanks. The winding machine has stronger movement flexibility and functionality. The microcomputer-controlled fiber winding machine can achieve three-dimensional control and has formed a series of commercial production stages; the fiber winding process is combined with other processes to promote the composite manufacturing process of composite materials.

 

Research on thermoplastic composite winding technology has begun in China. The rapid development of fiber winding technology has provided strong support and guarantee for my country’s aerospace and national defense construction. Filament winding products are also used in various civil industries and fields such as petroleum, chemical industry, water supply and drainage, electricity, mining, environmental protection, and hydraulic engineering.

 

Development Achievements Of Fiber Winding Technology

In the 21st century, my country’s fiber winding technology has made great achievements after nearly 60 years of development. It is mainly manifested in four aspects: basic research on fiber winding, equipment, product application, and related standards and patents.

 

Basic Research On Fiber Winding Technology

Many achievements have been made in key technologies such as stable winding theory, multi-coordinate motion mathematical model, fiber winding CAD/CAM software, precision tension control system, heavy-duty winding equipment research and development, manufacturing and drive. We have fully mastered the technologies of mechanical host, multi-axis linkage winding CAD/CAM software package, electronic control system, tension control, temperature control, measurement/data acquisition, quality assurance system, etc. We have independent intellectual property rights and software copyrights in many key technologies.

 

Filament Winding Equipment

The advanced level of fiber winding equipment is a reflection of the development level of winding technology. my country has basically realized full servo control by microcomputers. Two-axis, three-axis, and four-axis microcomputer-controlled fiber winding machines have played an important role in the winding and molding of pipelines, storage tanks, various pressure vessels, electrical insulation products, and sports and leisure products.

 

Microcomputer-controlled fiber winding machines with 6 axes of motion have been used in the research and production of composite products. Although my country has made certain achievements in the development of winding equipment, there is a big gap between China and advanced countries in the research and application of high-performance fiber winding machines.

 

Filament Winding Products

my country’s fiber winding products are rich in categories and widely used, including Shenzhou spacecraft load-bearing components, satellite structural parts, aviation gas cylinders, space system pressure vessels, solid rocket engine shells, large launch tubes and other high-performance fiber winding products used in the high-tech fields of aerospace and weapons and equipment; pipes, tanks, pressure vessels, gas cylinders, transmission shafts, rollers and other winding products used in various industrial fields of the national economy; rackets, fishing rods, musical instruments and other products used in the field of sports and leisure.

 

Figure 5 shows the composite shell of the SPTM-14 and EPKM-17 perigee-changing solid rocket engines developed by the Harbin Institute of Glass. It was successfully used with the Long March 2 carrier rocket to launch the Asiastar 2 satellite and the American Exstar satellite. It is the first large solid rocket engine fiberglass shell used for commercial launch services in my country.

 

Figure 6 shows the composite extension arm of the directional antenna used for Chang’e 1. Figure 7 shows the first domestic fiber-wound fiberglass cone ring used for 300 MW and 600 MW steam turbine generators, replacing imports and filling the domestic gap; Figure 8 shows the application of domestic fiber-wound carbon fiber composite rollers in textile machinery.

 

 

 

Filament Winding Standards and Patents

Product standards and specifications are a sign of product maturity, and product standardization also promotes wider application of products. So far, my country has issued and implemented more than 30 national standards, military standards, industry standards and specifications for fiber winding methods and products. Table 1 is the current standards and specifications for some winding products. Winding technology and related products have been granted more than 1,000 patents. Among them, there are more than 800 patents for composite pipe technology, manufacturing, equipment, design, etc.

 

 

 

Table 1 Current standards and specifications for winding products

 

Future Development Trends of Fiber Winding Technology and Equipment

 

At Present, My Country’s Fiber Winding Technology and Equipment Show the Following Development Trends:

 

The fiber winding process is composited, and the winding process is combined with pultrusion, weaving, RTM, laying, molding and other processes. And developed products such as winding pultruded thin-walled tubes, composite threaded bars, flexible continuous composite pipes, composite leaf springs, etc.

 

Winding machinery is highly automated, highly integrated and highly intelligent; robots are used for fiber winding, which has the advantages of multiple degrees of freedom, flexible movement, and a wide range of processes. They are especially suitable for winding small and complex components, including axially asymmetric and double concave parts.

 

New curing technologies and online curing monitoring technologies are constantly applied. Infrared heating, microwave heating, flame heating, electron beam curing and other technologies are widely used in the curing and molding of winding products.

 

Fiber winding products are developing in the direction of high performance and low cost.

 

Part 2: Development History, Trends and Applications of Winding Technology of Advanced Composite Material Forming Technology

 

Advanced composite materials have the advantages of high specific strength, large specific modulus, good fatigue resistance, good vibration reduction performance and strong designability, and are widely used in the field of national defense science and technology and civil engineering.

 

The amount of composite materials has become one of the important indicators for evaluating the performance of aerospace vehicles. In the production technology of resin-based composite materials, fiber winding technology is the earliest developed and most widely used processing technology. Compared with other production processes, fiber winding composite products can be designed according to the structural characteristics and stress conditions of the product.

 

The winding law can give full play to the strength of the fiber, and has the characteristics of neat fiber arrangement and high accuracy. It has been widely used in aerospace and civil industries, such as rocket engine casings, aircraft fuselages, aeroengine blades, blade rings and casings, automotive fuel gas cylinders, medical oxygen cylinders, oil and gas storage tanks and pipelines.

 

The winding molding process mainly involves winding the continuous fiber (or cloth tape, prepreg yarn) soaked in resin glue onto the core mold evenly and stably under the guidance of the wire guide according to a certain linear law, and then obtaining the product after curing treatment. The filament winding process is a molding technology mainly used for products with axisymmetric structures.

 

According to its structure, it is mainly divided into two categories: lined and unlined. Its product performance is relatively stable.

 

Figure 1 is a schematic diagram of the filament winding process.

 

 

 

Figure 1 Schematic diagram of fiber winding process

 

The Development History and Trend of Winding Molding Technology

 

Fiber winding products first appeared in 1945 as fiberglass rings, which were used in atomic bomb engineering at that time. In 1946, the United States applied for a patent for fiber winding technology.

 

In 1947, Kellogg Company in the United States successfully manufactured the world’s first winding machine, and then the first rocket engine shell was manufactured through the winding process.

 

In the 1950s, NASA and the Air Force Materials Research Laboratory successfully used the winding process to manufacture the “Polaris A3” missile engine shell. With a cost of only 1/10 of titanium alloy, the weight was reduced by 1/2 and the range was more than doubled, thus establishing the application status of winding products in the high-end military field.

 

In the 1960s and 1970s, winding technology developed rapidly, but the fiber material was mainly glass fiber. With the development of new materials, the application fields of fiber winding products have become more and more extensive, gradually expanding from the initial military field to chemical, sewage treatment, petroleum and other fields.

 

Commercial winding machines have also begun to be produced and sold. Many American companies have begun to produce various high-pressure pipes, sewage pipes and other composite materials, such as large storage tanks with a diameter of 10 m and a volume of 1000 m3.

 

In the 1980s and 1990s, the application fields of fiber winding technology were still mainly aviation and national defense technology, but there was also some development in the civilian field, such as pressure pipes and containers. The world’s first computer-controlled winding machine came out during this period. The use of computer-controlled winding machines increased the winding accuracy and expanded the types of fiber winding products.

 

Since the 1990s, fiber winding technology has entered a stage of rapid development. The development and research of multi-axis winding machines have made the shapes of fiber winding products more diverse (Figures 2 and 3).

 

Figure 2 FRP pipes and carbon fiber composite gas cylinders

 

Figure 3 FRP tank and rocket engine shell

 

With the rapid increase in the application of fiber winding products in high-end technology fields, it has developed into one of the key components of structural power and fuel systems.

 

At present, fiber winding technology has been widely used in aerospace, national defense science and technology and civil industry, including satellite trusses, rocket engine shells, aircraft auxiliary fuel tanks, engine nacelles, brakes and fuel tanks; missiles, rocket launch tubes, torpedo tubes and machine gun mounts; pressure pipes, tanks, CNG cylinders, bearings, energy storage flywheels, sports equipment and transportation vehicles, etc.

 

Nowadays, fiber winding technology is developing towards high-level mechanization, automation, and intelligence such as robot operation, so as to realize automated winding molding. The development of fiber winding software is the only way to achieve automated winding.

 

The research on computer-aided design (CAD) winding line is the cornerstone of automated software development. Using computer-aided design winding line, combining finite element analysis technology with fiber trajectory calculation technology can simplify the optimization design of winding line and greatly shorten the product design and development cycle. The organic combination of computer-aided design, computer-aided engineering (CAE) and computer-aided manufacturing (CAM) is an inevitable trend in the future development of automated winding.

 

Application of Winding Molding Technology

 

Application in Energy, Chemical Industry And Transportation Fields

 

The main applications of winding products in the civil field include: composite pressure pipes, storage tanks, pressure vessels, breathing cylinders and natural gas cylinders, fan blades, towers, poles, insulators, sports and leisure products, industrial transmission shafts, various rollers, etc.

 

 

 

Figure 4 Pressure vessels, gas cylinders, membrane shells

 

As a modern industry, automobiles are developing rapidly under the impetus of science and technology. With the continuous improvement of the application level of automobile composite materials, the amount of composite materials used per vehicle will gradually increase. In 2015, the total amount of plastics and composite materials required by my country’s automobile industry was about 1.65 million tons.

 

With the continuous development of molding technology and equipment, the application of composite automotive parts in the automotive field will expand day by day. In order to improve the lightweight and high-strength performance of automobiles, composite materials are gradually replacing traditional automotive manufacturing application materials. The main applications of winding technology in automobile manufacturing are drive shafts, exhaust pipes, turbocharger pipes, vehicle-mounted gas cylinders, energy absorbers, bumpers, etc.

 

The most demanded composite material in the marine ship field is composite pipes. The composite pipes formed by winding are widely used in offshore oil and gas transportation, offshore platforms and ships due to their corrosion resistance, oil resistance, high temperature resistance and other characteristics.

 

In addition, there are also applications such as dredging pipelines, submarine oil hoses, submarine pressure hulls, deep-sea detectors, diving breathing cylinders, and ship masts (Figure 5).

 

Figure 5 Offshore pipelines and cables

 

Applications in the field of oil and gas engineering can be divided into land and offshore applications, mainly oil and gas transportation pipelines and dredging pipelines (Figures 7 and 8). Composite pipelines are gradually replacing traditional steel pipelines due to their superior corrosion resistance and are widely used in actual engineering.

 

 

 

 

Figure 6 Land oil and gas pipelines, offshore oil and gas pipelines

Application in Aerospace and Military Fields

 

The automated forming process of aircraft composite components mainly includes three types: fiber winding, fiber tape winding and fiber laying. Due to the high strength, high temperature resistance and corrosion resistance of winding products, winding products can be used in the aviation field to form parts such as radomes, engine casings, fuel tanks, aircraft auxiliary fuel tanks and filters. They can also be used in the forming of small aircraft and helicopter fuselages, wings, blades, landing gear and other structures. Many high-pressure gas cylinders on modern large jet airliners are manufactured using composite winding forming technology.

 

In the field of aerospace, winding forming technology is mainly used in the manufacture of Shenzhou spacecraft load-bearing components, satellite structures, return capsules, space systems, composite pressure vessels, solid rocket engine shells, etc.

 

In the field of national defense and military industry, winding forming technology is mainly used in large missile composite launch tubes, torpedo tubes, attitude control systems, gun racks, rocket launch tubes, rail gun barrels, etc.

 

Spark machine tools have made major breakthroughs in the field of multi-axis CNC winding. Processing complex components such as wings and blades is no longer difficult!

 

The winding and laying molding of advanced composite materials are key manufacturing technologies for core components such as solid rocket engine casings, large aircraft fuselages, wings, and wind turbine blades, and play a vital role in the implementation of major projects in my country and the development of the aerospace industry. For many years, my country’s composite winding and laying molding manufacturing technology has been facing the problem of “stuck neck”.

 

On April 2, 2022, the multi-axis linkage composite CNC winding equipment, a national key project developed by Xinghuo Machine Tool Group Corporation and Wuhan University of Technology, was officially delivered to the client. As a result, the “stuck neck” problem of long-term reliance on foreign composite winding equipment has been completely solved, and Xinghuo Machine Tool Group Corporation has also fully achieved a major breakthrough in the independent control of key core technologies.

 

As an advanced material, composite materials have a very broad development space. Advanced composite materials have a series of advantages such as light weight, high specific strength, high temperature resistance and corrosion resistance. They are widely used in aerospace, national defense equipment and energy development, and have promoted the rapid development of related industrial fields. The wide application of composite materials depends to a large extent on the molding process of composite materials. Among them, winding and laying technology is a fast-growing and effective technology in recent years.

 

Winding technology refers to the method of continuously winding pre-impregnated rubber fibers or cloth tapes on a core mold or lining corresponding to the inner cavity size of the product under the conditions of controlled tension and predetermined linear shape, and then solidifying it into a product of a certain shape at room temperature or under heating conditions.

 

With the development of computer technology, information technology, and control technology, the functions of tape winding molding technology are constantly expanding. From a foreign perspective, the United States has applied the tape winding molding process to model development: 13 parts in the nozzle components of the MD-2 solid rocket engine and the engine nozzle of the “Dwarf” missile are all wound; Europe and Japan also widely use the tape winding molding process in the fields of spacecraft and weapons development: the booster nozzle of the European “Ariane” rocket, the shell of the French M51 missile, and the booster nozzle of the Japanese M-3S2, H-I, and H-H rockets are all using wound composite materials.

M51 missile casing during winding

 

In China, my country has been developing composite winding equipment and its molding process since the 1960s. For example, Beijing FRP Research and Design Institute, 703 Institute of the First Academy of Aerospace, 43 Institute of the Fourth Academy of Aerospace, Harbin Institute of Technology and Huazhong University of Science and Technology have successively developed different composite winding molding equipment.

 

The multifunctional cloth tape CNC winding machine independently developed by Northwest University of Technology has high working efficiency, and the wound products meet the model process requirements, becoming a key supporting equipment that can meet the development of high-performance engine nozzles and aerospace vehicle insulation and ablation-resistant parts.

 

However, the above-mentioned winding molding equipment is basically developed for rotating body parts with regular surfaces, and cannot be wound for large irregular and complex structural parts such as wings, fuselages, and wind turbine blades of large aircraft.

 

 

 

Multifunctional CNC tape winding machine independently developed by NJTU

 

With the development of composite materials related technologies, tape winding and laying molding technologies show a trend of multi-process composite, precision molding equipment, increasing application of CAD/CAM technology, combination of molding equipment and robots, increasing number of thermoplastic resin-based composite materials and continuous application of new curing technologies.

 

After more than 40 years of research and development, the research and application of composite winding and laying molding manufacturing technology in my country has begun to take shape, but it still faces the strict blockade of foreign technology and serious shortage of technology reserves.

 

The multi-axis linkage composite material CNC winding equipment developed by Xinghuo Machine Tool Group Corporation and Wuhan University of Technology was officially delivered to the client. As a result, the “neck-stuck” problem of long-term reliance on foreign composite winding equipment has been completely solved.

 

The equipment delivered to the user this time is a key equipment of the national key project. It is an intelligent high-tech product integrating new processes, new material manufacturing technology, automatic control technology, etc. It can complete the winding processing and production of various non-metallic glass fiber and carbon fiber composite products in cylindrical, spherical, conical and other shapes. The equipment has the characteristics of high degree of automation, high precision and strong reliability. It has broken through many domestic technical bottlenecks, solved the domestic (technical) bottleneck problem, and filled the domestic gap.

 

Fiber winding technology is currently used in many special components and key areas, but due to the constraints of foreign core key technologies, the research and development of domestic high-end winding equipment technology and equipment is relatively slow.

 

To this end, Xinghuo Machine Tool Group Co., Ltd. and Wuhan University of Technology established the first “Composites Winding Equipment Innovation Engineering Center” in China that specializes in composite materials equipment in 2020, and went all out to carry out technology research and development.

 

At present, a number of high-precision and ultra-heavy CNC winding equipment have been completed, achieving major breakthroughs in the independent control of key core technologies to meet the needs of national defense construction.

 

 

CNC Winding Equipment Delivery Site

As the “chain leader” enterprise of the province’s industrial chain, Xinghuo Machine Tool Group Co., Ltd. is also developing lightweight production wire laying equipment and heavy-duty CNC winding machines with a load capacity of 300 tons based on existing technologies, adding spark elements to strengthen the province’s and even the country’s mechanical manufacturing industry chain, realize the advanced industrial foundation, and modernize the industrial chain.

 

my country breaks through the automatic laying technology of composite materials to help develop a new generation of fighters

 

Faced with the rapid development of foreign composite material laying technology and equipment technology, the AVIC Manufacturing Institute formed a technical research team in 2006 in combination with the needs of my country’s aviation weapons and equipment, aiming at engineering applications and challenging the automatic laying manufacturing technology of composite materials.

 

Over the years, with the support of all parties and through unremitting efforts, the team has basically mastered the key technologies of composite material automatic laying manufacturing technology and equipment, and its overall level is in the leading position in China. It has made a lot of technical reserves for the promotion and application of this technology in the aviation field in China, and has also laid a solid foundation for the improvement of the overall level of my country’s aviation manufacturing technology.

 

Filling The Gap and Standing Out

For many years, the laying of composite prepregs has been mainly based on manual crafts. Until the beginning of the “Eleventh Five-Year Plan”, there was still a blank in the domestic equipment manufacturing field for automatic tape laying machines suitable for the manufacture of large aircraft wing composite structures; at the same time, there are only a handful of automatic laying equipment truly used in the production of aviation models in China, and all of them rely on imports, which greatly restricts the further improvement of production efficiency and product stability in the aviation manufacturing industry.

 

In order to break this bottleneck and promote the orderly development of my country’s aviation manufacturing industry towards automation, networking, and intelligence, the project team bravely took on this “hard bone”.

 

After five years of hard work and countless days and nights of hard work, the moment when manual laying was transformed into automatic realization, the joy of success permeated the hearts of everyone in the project team. The composite material automatic laying equipment combines the development and progress of related material technology and laying process, opens up the composite material automatic laying production process, and fills the domestic gap. The project team proudly said: “Our overall technology has reached the international advanced level, and some aspects can be called internationally leading!”

 

Nowadays in the field of domestic aviation manufacturing, this composite material laying equipment that has been tested by test pieces and installed parts can be said to be the “only one”. Unlike ordinary CNC cutting equipment, this equipment has the characteristics of complex structure, strong static and dynamic rigidity, high dynamic performance requirements, multiple linkage coordinates, and complex control.

 

In particular, its core component, the laying head, has many components, high precision, high integration, small and exquisite, multiple laying actions, and quite complex collaborative control. The specification range it adapts to has basically reached the international advanced level.

 

 

 

Japan manufactures carbon fiber main wing structure for Boeing 787 for the United States

Bold innovation, bravely take the lead

 

It is not easy to take the lead. The biggest problem encountered by the project team is that the relevant process research during the development of composite material laying equipment is still in its infancy in China, and it is difficult to put forward exact technical indicators for the development of automatic tape laying machines in terms of equipment functions and performance. How to extract the demand for automation from manual work? The bottlenecks encountered by the team in the initial research and development stage can be imagined.

 

In view of this, the project team studied and determined the overall technical approach of first developing the main body of the equipment, introducing and integrating individual key components first, and then innovating. On the basis of high-starting point and high-level foreign advanced equipment, equipment development and process exploration should be carried out to break through key technologies and master core technologies. With the support of the manufacturing institute, the project team sent people to visit and exchange technology several times abroad, and invited foreign technical experts to give lectures and consultations.

 

Through in-depth exchanges and cooperation with foreign technical experts, a solid foundation has been laid for equipment development and process research. According to the targeted technical survey of domestic aviation main engine factories, the project team summarized and analyzed the application needs of the industry.

 

After determining the overall structural scheme and international cooperation partners for key components, designers and process personnel, through repeated experiments and collisions, finally broke through the design and manufacturing technology of key functional components, and realized the function of simulating manual production with mechanisms.

 

At the same time, in view of the preparation technology and conditions of prepreg, prepreg slitting equipment and processes were developed to solve the material supply problem of laying equipment, and layability research was conducted on typical structures to explore the optimal laying process parameters.

 

Pioneer Team With Responsibility On Shoulders

A team that dares to challenge must have its uniqueness. The rich project resources of the institute provide a platform for developers to have a broad vision. This team started with high-end CNC machine tools and has been engaged in the development of high-difficulty equipment.

 

Everyone in the team is not simply engaged in the development of a composite material laying equipment. The equipment involved is very diverse and adaptable to a wide range of professional fields. It can be said that they have experienced many battles and are knowledgeable.

 

In making equipment, mechanical, electrical, pneumatic, hydraulic, assembly, commissioning, and service are all indispensable. The team may not have obvious advantages relying on individuals alone, but the comprehensive ability of the team together is obviously better than others.

 

Today, the project team has grown from more than 10 people at the beginning to more than 30 people now, gathering talents from various professional fields such as structural design, integrated control, gas-liquid transmission, simulation analysis, software programming, assembly and debugging, without missing items or shortcomings.

 

As a special equipment R&D team, in addition to having rich experience, it must also have a solid foundation. It is far from enough to continue the past path of “introduction, digestion, and absorption” to achieve the development of complete equipment. The so-called knowing the truth must also know the reason. There is always a risk of falling behind when relying solely on experience to conquer the world. The project team fully recognizes this point.

 

In recent years, it has been committed to technological innovation, working hard on basic research, and building an experimental platform with the support of the institute. It really digs deep from the basic principles and strives for excellence.

 

This is a group of people who can endure loneliness. In order to break through the technical difficulties of the project, they lie on the test bench for days and months without getting tired. For them, meeting challenges is a kind of fun.

 

“Being able to help the country solve the technical difficulties of ‘stuck necks’ and make some special equipment urgently needed by aviation in a down-to-earth manner, this achievement and honor cannot be replaced by any reward.” Deputy Chief Engineer Sun Nianjun said with satisfaction.

 

As the best solution for the manufacture of large-scale integral composite structures of aircraft, composite material automatic laying technology will play an irreplaceable and important role in the development of new aircraft in my country, and can provide equipment and process foundation for the future development of high-performance fighters and large aircraft.

 

With the implementation of new aircraft development projects such as new generation fighters, large aircraft and unmanned aerial vehicles in my country, and the development and promotion of domestic composite material automatic laying equipment, the future of domestic composite material automatic laying technology is full of hope.

 

S-300 Air Defense System Ground Bombing

In recent times, a large number of battles in which the Russian army used S-300 surface-to-air missiles to carry out ground strikes have been found on the Ukrainian battlefield. In Kharkov, Zaporizhia and Kherson, the engine and body wreckage of the S-300 missile were found.

 

 

 

Then the question is, as a surface-to-air missile that performs air defense missions, can the S-300 air defense system play a guest role as a surface-to-surface ballistic missile?

 

Of course it can. The S-300 air defense missile system currently in service in Russia is originally a very powerful ground attack weapon, but it was previously hidden under the halo of surface-to-air missiles, and people didn’t know much about it.

 

 

 

In the southern part of Kherson Oblast, the Ukrainian army has just destroyed a Russian ground-to-air missile position. The location is in the village of Zelenotropinsik, where two Russian S-300 missile launchers were destroyed, as well as command vehicles and other vehicles.

 

From the video, the S-300 missiles are on duty. It is said that the Ukrainian army used HIMARS rocket launchers to attack this S-300 ground-to-air missile position. It is rumored that this S-300 ground-to-air missile position is used by the Russian army for ground strikes.

 

Because of the ability to carry out radio commands in the guidance system. The S-300 air defense missile has a certain ground strike capability at the beginning of its development. When the S-300 is conducting a ground strike, the maximum range can reach 120 kilometers. Equivalent to a short-range ballistic missile.

 

 

The S-300 missile has a 150 kg fragmentation-killing blasting warhead, which is as powerful as a 300 mm Tornado rocket. The overall combat effectiveness of the S-300 missile when conducting ground strikes is comparable to that of the Tochka-U ballistic missile.

 

Of course, the accuracy of the S-300 when conducting ground strikes is very general. The S-300 missile adopts a mid-course inertial navigation + radio command + terminal semi-active radar guidance system. The error of the inertial navigation can be corrected by radio command in the mid-course of the trajectory, allowing the missile to enter the parabolic uncontrolled flight in the second half with a relatively accurate attitude.

 

The missile launch process is as follows: First, the elements that need to hit the fixed ground target are converted into missile firing instructions, namely the range, firing azimuth and elevation angle, and loaded into the fire control system of the surface-to-air missile.

 

In the first half of the trajectory, the trajectory deviation is continuously corrected by the inertial navigation system, and then the missile is tracked by the ground fire control radar, and then the error of the inertial navigation system is corrected by radio commands to maintain accuracy.

 

In this way, the fire control system controls the missile to fly to the highest point of the trajectory calculated before launch, and then the engine is shut down. The missile flies along a parabola in the second half of the uncontrolled trajectory until it falls into the target area.

 

 

 

The accuracy of the missile’s landing point corrected by radio commands can reach within tens of meters. This is equivalent to the accuracy of a short-range ballistic missile in the 1980s.

 

Fortunately, the Russian military has a large number of S-300 missiles in stock, tens of thousands of them, so it is also very useful to use them to attack ground targets in Ukraine.

 

 

How did the Russian army come up with this move? In fact, they learned it from China. China is the most classic example of using surface-to-air missiles to transform into surface-to-surface missiles.

 

During the Yemeni civil war, there was a special ballistic missile battle. The Houthi armed forces launched a short-range ballistic missile at the military base of the Saudi and other Gulf countries in Yemen, killing 147 officers and soldiers of the coalition, including two senior commanders. The ballistic missile launched in this attack was actually a surface-to-surface ballistic missile modified from a Chinese Hongqi-2 surface-to-air missile.

 

 

 

 

In the 1990s, China converted a large number of Hongqi-2 surface-to-air missiles into surface-to-surface ballistic missiles and exported them in large quantities. It then developed the B611 missile family, and then Iran, Turkey and other countries developed their own series of missiles based on this missile. This huge missile family with Hongqi-2 as its ancestor is all the descendants of Hongqi-2, with dozens of models.

 

Mengtian Laboratory: Boosting the breakthrough of turbofan engines!

In the future, the Mengtian Laboratory will mainly focus on microgravity science research and support cutting-edge experimental projects such as fluid physics, materials science, and ultracold atomic physics.

 

 

On October 31, 2022, the Mengtian laboratory module was successfully launched

But there is one function that everyone still doesn’t understand. The space station is in a microgravity state, so why does the Mengtian laboratory module specifically conduct microgravity research? Is this microgravity science research really that important?

 

Mengtian laboratory module: mainly researching microgravity science

 

The Wentian laboratory module was launched on July 24, 2022. This laboratory module with a maximum diameter of about 4.2 meters, an axial length of about 17.9 meters, and a weight of 20 tons consists of a working cabin, an airlock cabin, and a resource cabin. The main task is to support sealed cabin applications and extravehicular experiments, and store astronaut consumables, space station spare parts, and supply cargo.

 

 

The experimental facilities of the Wentian laboratory cabin are located in the working cabin. There are a total of 8 experimental cabinets in the working cabin, including a life ecology experiment cabinet, a biotechnology experiment cabinet, a variable gravity science experiment cabinet, a scientific glove box, a low-temperature storage cabinet, and 3 empty experiment cabinets reserved for follow-up.

 

In addition, there are 30 exposed payload interfaces, and 1 expansion platform interface and 1 payload hanging point interface are reserved, providing ample scientific experimental resources.

 

 

The Mengtian Experimental Module, which has similar functions to the Wentian Experimental Module, has more payloads and is equipped with 13 standard payload cabinets. It is mainly aimed at microgravity scientific research and can support cutting-edge experimental projects such as fluid physics, material science, and ultracold atomic physics. It can be called the “Dream Factory” of Tiangong.

 

At the same time, in order to maximize the support capabilities for extravehicular experiments, the Mengtian Module is equipped with 37 payload installation stations outside the cabin, which can provide mechanical, electrical, and information capabilities for various scientific experimental payloads to ensure that they can carry out various experiments in the space environment.

 

Many friends are confused. There are already a large number of experimental equipment in the core module and the Wentian Experimental Module. Why is there another Mengtian Experimental Module? Isn’t this redundant? The core module, Wentian and Mengtian Experimental Modules do have experimental equipment, but the division of tasks and positioning of the three are different, which is very different.

 

 

Marked C is the core module, I is the Wentian module, and II is the Mengtian module

 

Especially for the microgravity experiment in the Mengtian laboratory module, it is difficult to find a suitable simulation environment on Earth, because the way to achieve the microgravity environment is to simulate the period between the end of the climb phase and the beginning of the dive phase of the parabolic flight of a large aircraft. The time can only be calculated in seconds, which is not enough to do a longer experiment.

 

 

 

 

In addition, the microgravity science environment of the Mengtian Experimental Cabin is specially customized for “fluid physics and material science”. The material research in it is very important for my country’s future jet engines, especially variable cycle and turbine-based scramjet engines. The reason for this needs to be explained in detail.

 

The core technology of aviation engines: high-temperature turbine

The most widely used modern aviation engines are two types of engines, one is turbojet and the other is turbofan, but in fact the principles of the two are similar, except that the turbofan has an additional duct, and the core engine principle is basically the same. There are basically several components:

 

Multi-Stage Compressor;

 

Combustion Chamber;

 

High and Low Temperature Turbine;

 

It looks like this structure is simple, but in fact it is very complicated. It seems relatively easy to understand with the anatomical diagram of the engine:

 

 

The Working Process Connection Between Each Part is as Follows: the compressor has many stages, from front to back, from the low-pressure compressor to the medium-pressure compressor and finally to the high-pressure compressor. After that, the compressed high-temperature air will be sent into the combustion chamber, and the fuel will be injected and ignited. The high-temperature expanded combustion gas will be discharged to the rear of the engine.

 

 

 

There is a high-temperature turbine behind the combustion chamber, which is the power source of the entire engine. When the high-temperature gas passes through the high-temperature turbine, it will drive the turbine to rotate. This high-temperature turbine then drives the high-pressure compressor in front. Behind the high-temperature turbine are the medium-temperature turbine and the low-temperature turbine, which respectively drive the medium-pressure compressor and the low-pressure compressor in front. Of course, it may also be driven by the gearbox.

 

Engine Thrust and Thrust-to-Weight Ratio

 

Whether it is a turbojet or a turbofan, these two are very important parameters, which indicates the excellence of an engine. The thrust-to-weight ratio of aircraft engines has undergone the following changes:

 

The first generation of aircraft engines appeared in the 1950s, represented by the British Conway engine and the American JT3D engine, with a thrust-to-weight ratio of about 2;

 

The second generation of aircraft engines appeared in the 1960s, represented by the British Spey MK202 and the American TF30 engine, with a thrust-to-weight ratio of about 5.

 

The third generation of aircraft engines appeared in the 1970s and 1980s, represented by the US F100, F110, F404, Europe’s RBl99, M88-3, Soviet RD-33 and AL-31F engines, with a thrust-to-weight ratio of about 8.

 

The fourth generation of aircraft engines appeared in the 1990s, represented by the US F119 and Europe’s EJ200 engines, with a thrust-to-weight ratio of more than 10. The F119 is equipped with the F-22 fighter, and the EJ200 is equipped with the “Typhoon” fighter.

 

The fifth generation of aircraft engines appeared in the early 21st century, represented by the US F135 engine and the F136 engine jointly developed by the United Kingdom and the United States, with a thrust-to-weight ratio of 12 to 13

 

 

Civilian Turbofan Engine

 

There are several ways to achieve a higher thrust-to-weight ratio. The first is to increase the bypass ratio. The larger the bypass of the turbofan, the greater the thrust. However, as the bypass ratio increases, the resistance also increases. This method can be used for low-speed passenger aircraft and some fighter jets, but high-speed aircraft can only find ways from the inner channel. There are roughly several parameters related to thrust:

 

The Flow Rate Through The Engine;

 

The Temperature Difference Between the Engine Intake and “Exhaust” (Core Engine Temperature);

 

The first requirement is relatively easy to understand. The greater the air flow, the greater the thrust; but the number of modern engine compressor stages is getting higher and higher. When it reaches the combustion chamber, the pressure is already very high.

 

High-temperature and high-pressure air is actually not conducive to the operation of the engine combustion chamber, because it will reduce the temperature difference between the engine intake and exhaust.

 

Therefore, if there is a cooling technology that can cool the intake, it would be a good idea, but in fact, this cannot be done on jet engines for the time being.

 

 

 

The second is the increase in the temperature of the jet engine combustion chamber (turbine inlet temperature). The higher the temperature of the gas discharged from the combustion chamber, the greater its expansion pressure and the higher the thrust. Every 1°C increase in turbine inlet temperature is an improvement.

 

For example, the famous AL-31F engine has a turbine inlet temperature of 1685 K (1,412 °C) and a thrust-to-weight ratio of 7.87:1, while the F119 has a turbine inlet temperature of 1577°C and a thrust-to-weight ratio of 10.

 

It must be reminded here that there are many ways to increase the thrust and thrust-to-weight ratio of the engine, and only the more typical methods are introduced here.

 

To increase the temperature before the turbine, it is necessary to consider whether the high-temperature turbine can bear it, because the high-temperature gas directly impacts the high-temperature turbine.

 

 

The temperature before the turbine of the F119 engine mentioned above is already around 1600℃. Most materials have melted or softened at this temperature, or at least are far lower than the performance at room temperature. So how to improve the high temperature resistance of the high temperature turbine? There are several methods:

 

Unparalleled Cooling Technology;

 

More High Temperature Resistant Materials;

 

Stress-Free and Damage-Free Manufacturing Methods;

 

As long as the blade is cooled fast enough, its high temperature resistance can be increased. At present, the methods for cooling the blades include divergent cooling, air film cooling, impact cooling, internal enhanced convection cooling, laminate cooling and thermal barrier coating. Take air film cooling as an example, that is, drilling holes on the surface of the blade, leading the internal airflow from the hollow blade to spray out through the air holes, isolating the high temperature flame, so that the fan blade can survive higher temperatures.

 

Another way to increase high temperature resistance is to directly improve the high temperature resistance of the blades, such as adding other metal materials such as rhenium to cobalt-based high temperature alloys or nickel-based metal materials to improve the high temperature resistance and mechanical properties of high temperature alloys, as well as chromium-based high temperature alloys and ceramic blade materials, and starting to use anti-corrosion and thermal insulation coatings on the blades.

 

 

Another is to improve the manufacturing process. For example, conventional forging, no matter how dense it is, will also form defects when the material solidifies and crystallizes. Under the conditions of rapid cooling and heating, the material will soon be damaged by defects caused by stress, and even cause the engine to stop in the air or even cause the aircraft to crash and people to die. Solidifying high-temperature alloys and single-crystal high-temperature alloys can solve this problem.

 

Among them, single-crystal high-temperature alloys have developed to the third generation. In addition to blades, the inner wall of the combustion chamber, turbine guide vanes and turbine disks also require extreme high temperature resistance and high temperature creep prevention.

 

 

 

Zero-Gravity Environment, Manufacturing Better Alloys And Single Crystal Materials

 

Currently, various materials are basically manufactured in a gravity environment. As you all know, there is a problem in a gravity environment. The mixing of various materials in alloy materials is a problem. It may also be mixed with the inner wall material of the “crucible”, resulting in impure materials. Defects caused by convection during smelting and casting are also a big problem. In a zero-gravity environment, these problems that make materials prone to defects can be avoided:

 

Zero-gravity can achieve “container-free smelting”, and materials can be suspended in the air for heating: high-purity, high-strength new materials can be smelted to obtain quality standards that cannot be achieved by ground production, and “perfect” nickel-based single crystal high-temperature alloys can also be manufactured.

 

More importantly, we can compare the process of smelting defect-free materials under zero-gravity conditions with the process under gravity environment, find the causes and laws of defects to improve the process, and finally produce products that are close to or even better than those in a zero-gravity environment. Only a better test environment can discover more problems, thereby producing metal materials that are more resistant to high temperatures and higher in strength.

 

 

 

At present, the temperature before the turbine has basically become an extremely important indicator for determining engine performance. For every 100℃ increase in the temperature before the turbine, the thrust can increase by 15%. If the difference is 200℃, it means that the engine is one generation behind. According to the current global engine turbine temperature improvement rate, it increases by about 10℃ every year. This is how someone determined that my country’s engine technology was 20 years behind that of the United States. So you can see the importance of high-temperature alloy research.

 

 

 

Microgravity Material Research is In Full Swing Abroad: Now it’s China’s Turn!

 

The space industry of the United States and Russia started relatively early. As early as 1969, the Soviet Union conducted the first experimental research on space metallurgy, and the United States followed closely. So far, the laboratories of the United States, Russia, ESA, Japan, etc. based on the International Space Station have conducted more than a thousand metallurgical experiments in space.

 

 

 

In May 2021, the International Space Station released a 2020 research report, one of which was about the physical properties of industrial alloys:

 

The research conducted by the European Space Agency involved measuring the thermophysical properties of industrial alloys using electromagnetic levitation agents to improve the hardening process in zero gravity.

 

This study specifically recorded the results obtained for three high-temperature alloys (nickel-based high-temperature alloys), which are widely used in turbines and other power applications.

 

Among these results, there are high-resolution thermophysical properties (liquid surface tension, viscosity, mass density, specific heat capacity) data that are not available on Earth, which are essential for improving manufacturing efficiency and product quality.

 

It has been 24 years since the first module of the International Space Station was launched into space in 1998. Although it is already old and the maintenance cost is very high, the 16 participating countries are still reluctant to give up. It has been extended to 2031, and the research on high-temperature alloys is also an important reason.

 

 

Although China’s Tiangong space station is a little late, we have basically completed it. The microgravity experiment cabinet, which is crucial to the research on high-temperature alloys, is also ready. I believe that our research on high-temperature alloys will make great progress, and the Mengtian laboratory cabin will provide us with a perfect experimental environment.

 

 

Further Reading: Variable Cycle Engine and TBCC

The United States has determined that the power of the future sixth-generation aircraft will be the variable cycle engine. This engine is nothing special. It can work in a turbojet state at high speed, which is fuel-efficient and has excellent high-speed performance. It can work in a turbofan state at low speed, which has high thrust and is fuel-efficient. It combines the advantages of turbojets and turbofans but avoids the disadvantages of both.

 

 

Its difficulty lies in the seamless switching between turbojet and turbofan, as well as the higher turbine inlet temperature. For example, the turbine inlet temperature of the GM XA100 variable cycle engine is 1648℃, and the performance is greatly improved. The fuel efficiency of XA100 is improved by 25%, and the thrust is increased by 10%. It can increase the fighter’s air time by 50% and the range by 35%.

 

TBCC: Turbine-Based Scramjet

The scramjet engine has a very simple structure and excellent performance, but it can only be started at 4-5 times the speed of sound. At present, there are two ways to solve the turbine-based scramjet engine:

 

The turbojet engine is pushed to 4-5 times the speed of sound to ignite the scramjet engine;

 

The turbojet engine is pushed to supersonic speed, and then the subsonic scramjet engine is ignited;

 

 

 

The latter is more difficult, but the former is not easy either. Either one can solve the problem, but the first one obviously requires a higher level of turbojet. Although the working time is not long, it can be achieved with a turbojet with afterburner, but we must understand that if a higher temperature and longer afterburner combustion chamber is used, the heat resistance temperature of the turbine will also increase, because this will increase the pressure of the combustion chamber, so high temperature resistance has always been a hurdle that cannot be bypassed.

 

Let’s take a look at the MAX force of the Long March 5B rocket!

As my country’s current rocket with the largest low-Earth orbit carrying capacity, the Long March 5B rocket has increased the low-Earth orbit carrying capacity of my country’s Long March series rockets from 9 tons to 25 tons, and is known as the “strongman” in the Long March rocket family.

 

It is understood that the space station is located in a low-Earth orbit about 400 kilometers from the earth, and the manned space station module is the heaviest payload in my country so far. The takeoff weight of the Wentian cabin and the Mengtian cabin exceeds 23 tons.

 

So, how did the Long March 5B rocket get so strong? ——The rocket fully exploits the advantages of the large thrust of liquid oxygen-kerosene engines and the high specific impulse of hydrogen-oxygen engines. The eight 120-ton liquid oxygen-kerosene engines have a maximum pressure of 500 atmospheres, which is equivalent to pumping water from the Huangpu River directly to the Qinghai-Tibet Plateau 5,000 meters high. The take-off thrust can reach more than 1,000 tons.

 

 

 

The two hydrogen-oxygen engines configured in the first-stage rocket have the characteristics of high specific impulse, which enables the rocket to obtain greater thrust with less fuel. “The so-called specific impulse is the thrust generated by the engine burning a certain amount of fuel in a certain period of time. This can be figuratively understood as the ‘fuel consumption’ of a car.

 

The engine using liquid hydrogen and liquid oxygen propellants has low ‘fuel consumption’, which is one of the propellants with high specific impulse we have at present.” The deputy chief designer of the Long March 5B rocket explained. Therefore, the large carrying capacity of the Long March 5B rocket is due to the full exploitation of the working potential of the two new engines.

 

At the same time, in order to carry more propellants, living materials, etc. to maintain the on-orbit operation of the space station, after each launch mission, the Long March 5B rocket development team will optimize and improve the rocket according to the flight results to further improve the carrying capacity. Therefore, only the Long March 5B rocket can launch the manned space station compartment.

 

Big head! Accommodation Space Max

The Long March 5B rocket is not only “thick in the waist”, but also has a “big head”, and is known as the rocket “Bing Dwen Dwen”. And this “big head” is actually the fairing.

 

The fairing is an important component of the launch vehicle, used to protect satellites or other payloads from harmful environments such as aerodynamics, aerodynamic heating and acoustic vibration. The Long March 5B rocket has the longest and largest fairing in my country, with a length of 20.5 meters, a diameter of 5.2 meters, and a volume of more than 345 cubic meters. Such a spacious space is also tailored for launching space station modules.

 

As the size of the fairing increases, in order to ensure the carrying efficiency, the stiffness of the structure will decrease accordingly, and stiffness is a key factor affecting the separation energy design and separation envelope design. How to accurately simulate the stiffness characteristics of the fairing during flight and separation to ensure safe and reliable separation is a technical challenge faced during the development process.

 

After comparing multiple plans, the development team finally determined the separation plan, evaluated the fairing separation plan through a large number of simulation analysis and prediction, and carried out fairing separation tests many times, effectively verifying the design correctness and coordination of various system interfaces.

 

The deputy chief designer of the Long March 5B rocket introduced: “For this mission, in the early stage of fairing production, the development team used 3D visual scanning and other technologies to accurately simulate the dimensions of the fairing and the experimental cabin, and repeatedly checked in detail to confirm the safety gaps at key locations to ensure that the experimental cabin has enough space during flight and separation and will not get close to the fairing during flight.”

 

 

 

Simple Configuration, Maximum Reliability

my country’s current rockets are all multi-stage rockets. Multi-stage rockets often accelerate by igniting the lower stage rocket first, and then adjust the orbital posture and orbital accuracy through the upper stage rocket. This is like a long-distance race, where rockets of different stages take on the “relay” process of “starting, accelerating, sprinting, and crossing the finish line”.

 

The Long March 5B rocket only uses one and a half rockets to directly enter orbit, from ignition to orbit entry in one go. It is the only one and a half rockets in my country’s current launch vehicles that directly enter orbit, enriching and improving the spectrum of new generation launch vehicles.

 

In terms of system reliability, fewer stages, no stage separation, simple system, and high reliability are naturally high. For example, a bicycle has a simple structure, and it is okay to bump into it. If you fall, you can get up and continue walking. However, the spacecraft system is complex, and any slight bump in any position may cause great danger.

 

 

We know that stage separation is one of the most complex and most problematic links in rocket flight. The stage separation process of rockets is one of the key links that affect the success or failure of flight. Its control process is very complex. The boundary conditions of ground tests are quite different from the actual separation environment, which is one of the difficulties in rocket development.

 

Therefore, the fewer stages, the fewer separations and the lower the probability of failure. The Long March 5B rocket directly enters orbit with one and a half stages, which reduces the number of separations and further improves reliability.

 

Building Tiangong, Mission Significance Max

 

Manned space flight engineering is an important symbol of building a space power. The space station construction mission is the last step of the “three-step” development strategy of my country’s manned space flight engineering, and it is also the most complex step in the implementation of the project. The successful completion of the space station construction mission is of great significance to the long-term development of manned space flight and the long-term operation of the space station.

 

“This launch of the Mengtian experimental module docking with the core module will help the three modules of the space station form the basic configuration of the ‘T’ shape, complete the construction of the basic configuration of the Tiangong space station, and lay a solid foundation for the subsequent work in the space station operation phase, which is of great significance.” said a popular science expert from the General Design Department of the Rocket Academy.

 

 

This year, the Long March 7 and Long March 2F rockets will also launch the Tianzhou-5 cargo spacecraft and the Shenzhou-15 manned spacecraft respectively, achieving all the established tasks in the space station construction phase.

 

In the future, the Long March 5B rocket will also carry out the launch mission of my country’s large-scale space telescope for surveying the sky, meeting my country’s deeper needs for space exploration in the future. In particular, the Long March 5B rocket will form a combined rocket with the upper stage of the Long March series to achieve the mission requirements of my country’s multi-satellite network launch.

 

Analysis of my country’s new generation of satellite-borne atomic clocks – the “Chinese heart” of Beidou satellites

 

On February 12, 2018, my country successfully launched the fifth and sixth networking satellites of Beidou-3 in a one-shot two-satellite manner. The two satellites were each equipped with a high-precision rubidium atomic clock developed by the 203 Institute of the Second Academy of China Aerospace Science and Industry Corporation. As my country’s independently developed satellite-borne atomic clocks, their technical indicators have reached the international advanced level.

 

 

The Long March 3B Carrier Rocket Stands On the Launch Tower.

 

Before Launch, Technicians Conduct Various Functional Checks On The Rocket.

 

The Onboard Rubidium Atomic Clock Carried by the Beidou Navigation Satellite

 

The Long March 3 carrier rocket (and the Yuanzheng 1 upper stage) successfully launched the fifth and sixth BeiDou-3 global networking satellites.

 

 

 

Long March 3B Carrier Rocket In The Final Assembly Stage.

 

With the successful launch of the 5th and 6th Beidou-3 navigation satellites, Li Chunjing and his team celebrated with high fives. As the deputy director of the Atomic Frequency Standards Laboratory of the 203rd Institute, he was responsible for the development of high-precision satellite-borne rubidium atomic clocks for the Beidou-3 navigation satellite major project.

 

The satellite-borne rubidium atomic clock developed by his team is regarded as one of the most difficult products to develop for the Beidou-2 navigation satellite.

 

Its high technical content and great difficulty in overcoming it once made Xie Jun, the chief designer of Beidou navigation satellites, say that its development process was “epic”. So, what kind of clock is an atomic clock? What is its relationship with satellite navigation?

 

Atomic Clock Is The “Heart” Of Navigation Satellite

 

“As the ‘heart’ of navigation satellite, satellite-borne atomic clock determines the accuracy of navigation positioning, speed measurement and timing of navigation system, and is one of the core technologies for a country to have the ability to independently develop navigation system.”

 

As the person in charge of the research and development of high-precision satellite-borne rubidium atomic clock for Beidou-2 navigation satellite, Li Chunjing has been fighting on the front line of atomic clock development for 14 years. When talking about satellite-borne atomic clock, he opened up.

 

According to him, Beidou Satellite Navigation System is a global satellite navigation system independently developed and operated by my country. Its basic navigation principle is to use the distance between multiple satellites and an object on the earth to determine the position of the object.

 

According to the principles of physics, this distance can be obtained by multiplying the signal propagation speed by time, and the signal propagation speed used by satellite navigation has a fixed value. Therefore, the more accurate the time measurement, the more accurate the distance calculation, and the more accurate the navigation position positioning.

 

Therefore, from this perspective, “the core of satellite navigation is time measurement.” Wang Wenming, the chief designer of another satellite-borne atomic clock of the 203rd Institute, the hydrogen atomic clock, said that the precision device used to calculate time on the navigation satellite is the atomic clock, which uses the electromagnetic waves emitted when atoms absorb or release energy to time.

 

Because this electromagnetic wave is very stable, and then controlled by a series of precision instruments, the timing accuracy of the atomic clock can reach an error of only 1 second every 20 million years, thus providing accurate time measurement for satellite navigation, and is therefore called the “heart” of the navigation satellite.

 

At present, satellite-borne atomic clocks are divided into hydrogen atomic clocks, rubidium atomic clocks and cesium atomic clocks, which are manufactured using three elements: hydrogen, rubidium and cesium. Among them, the hydrogen atomic clock has the best stability index, but the difficulty of development is also the highest; the rubidium atomic clock has the advantages of small size, light weight, low power consumption, low technical difficulty and high reliability, and is currently widely used in navigation systems of various countries; the cesium atomic clock has a short service life, but its biggest advantage is its low drift characteristic.

 

“At present, my country has mastered the key technologies of rubidium atomic clocks and hydrogen atomic clocks, and has used these two atomic clocks to measure time on Beidou navigation satellites.” Li Chunjing said. At the same time, the 203rd Institute has also formed a satellite-borne cesium atomic clock team and carried out research and development, and it is expected to become the “heart” of Beidou navigation satellites in the future.

 

Well-Deserved High-Tech Craftsmanship

 

Anyone who wants to enter the 203rd Institute’s atomic clock laboratory to find out needs to be fully armed with a white coat, mask, head cover, gloves, and shoe covers. In the end, only the eyes can be left exposed, and this is still not enough. In order to avoid external interference as much as possible, entering the laboratory requires crossing a corridor swept by strong winds and brushing off the dust on the body. In the laboratory, the fresh air system works at full load day and night, and the temperature and humidity are strictly controlled within a certain range. Any atomic clock used by satellites is carefully cared for here like a newborn baby.

 

In addition to the high requirements for the production environment, the debugging of satellite-borne atomic clocks is also a “grinding” job. Atomic clocks are very “delicate”. Any slight change in parameters may affect their performance in space. Therefore, every time the whole machine is debugged, it needs a designer with sufficient experience to “handle” it personally.

 

“For example, after entering space, the ambient temperature of the satellite orbit will fluctuate, and the atomic clock may be affected by this and produce errors, which directly affects the positioning accuracy of the navigation system.” Yang Tongmin said that he succeeded Li Chunjing as the project leader of the satellite-borne rubidium atomic clock.

 

According to Yang Tongmin, in order to reduce the sensitivity of the atomic clock to temperature changes and avoid errors in space, “R&D personnel must understand all the characteristics of this atomic clock and find out what “temper” its circuit and physical system have, so as to know how to make comprehensive adjustments to create the best rubidium atomic clock.”

 

“Once the atomic clock is in space, it will be powered on and run until it “dies”, and it must be absolutely reliable.” Li Chunjing said. In his eyes, “atomic clocks are well-deserved high-tech craftsmanship products, which require engineers with craftsman spirit to carefully build.”

 

To Achieve Global Navigation, You Must First Have a “Chinese Heart”

 

Compared with rubidium atomic clocks, the hydrogen atomic clocks that flew into space with the third and fourth satellites of Beidou Phase III in January 2018 can enable the Beidou navigation system to achieve higher positioning accuracy, global coverage and longer autonomous navigation capabilities, significantly reducing the time calibration pressure of the Beidou navigation system during global application.

 

However, due to the more complex structure and principle of hydrogen atomic clocks, its research and development is more difficult. In order to enable the Beidou navigation system to obtain capabilities comparable to the three major navigation systems of the United States GPS, the European Union Galileo, and Russia’s third-generation GLONASS. The team of the onboard hydrogen atomic clock also spent nearly ten years to solve a series of technical problems such as parameter optimization of the temperature control system and improvement of electromagnetic compatibility, and realized the optimization of hydrogen atomic clock indicators, miniaturization of the whole machine, and lightweight technology research, and finally applied it to Beidou navigation satellites.

 

Whether it is a hydrogen atomic clock or a rubidium atomic clock, the satellite-borne atomic clock, a key task aimed at entering the forefront of the world, was “headscratching” at the beginning of the project – the laboratory environment requirements are high, the technology is completely monopolized by foreign countries, and there is no experience to learn from in the development process. “Although I was mentally prepared, I still didn’t expect that the research would be so difficult. Many problems have never been encountered before.” Li Chunjing said, “But he also clearly realized that the first condition for global navigation is to have an atomic clock! Atomic clock products cannot rely on imports, and there is only one way to go!”

 

Sorting out the clues, doing experiments, and debugging day and night, everyone is as tireless as a clockwork clock. “In order to solve technical problems, we work day and night to conduct experiments and verifications; during environmental tests, team members work in shifts to guard and record data day and night.” Li Chunjing said. For many years, the brain has been highly concentrated on this, and there is really a magical experience of solving problems in dreams. “Everyone has encountered the scene of dreaming about atomic clock joint adjustment.” The excellent “Chinese heart” needed by China’s Beidou navigation satellite was independently developed in this way to overcome difficulties.

 

Today, the space-borne rubidium atomic clocks and hydrogen atomic clocks developed by the 203rd Institute have reached the international advanced level in terms of technical performance and reliability, achieving independent control of key technologies of space-borne atomic clocks and breaking the foreign monopoly. The institute also won the special prize of the National Science and Technology Progress Award in 2017.

 

Looking up at the starry sky, almost every Beidou navigation satellite is equipped with an atomic clock developed by the 203rd Institute. These “Chinese hearts” will make the dream of our country’s Beidou autonomous global navigation system enter the ranks of high performance a reality.