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Project 921-3 Tengyun Space Plane

China unveiled the Tengyun Project in 2016, which is planning the first test flight for the Chinese space plane in 2030, Beijing-based Science and Technology Daily reported in December 2016. TengYun means 'to soar on clouds', "cloud mounting”, or "cloud rider". The word reminds Chinese of the heroic Monkey King Wukong from the classical epic "Journey to the West".

"The Journey to the West" or Xi You Ji, is the title of a Ming Dynasty (1368-1644) book that belongs to the "four most wondrous classical novels" of China. The plot revolves around Buddhist monk Xuanzang, who travels west to India with his four disciples, including the famous monkey king Sun Wukong, in search for holy scriptures. The other protagonists are the half-pig and half-monk Zhu Bajie and the water monster Sha Wujing. Xuanzang’s noble steed is a white horse that used to be a river dragon. The story dates back to a historically documented India trip: A monk named Xuanzang traveled to India in search of holy scriptures, more precisely the Mahayana, in the seventh century. With history at its base, the author Wu Cheng'en weaves a legend full of Buddhism and Taoism, heroes, demons, divine figures, supernatural power, and kung-fu. The fabulous monkey king is a classic trickster figure, equal parts arrogant, impatient, funny, upright, and brave.

Classic novel Journey to the West has been adapted so many times and in so many ways in China and overseas that people barely bat an eye when yet another adaptation of the story is announced. However, just why this Chinese literature classic and its lead character the Monkey King have been able to fascinate people for so long still remains a mystery. While the US has dozens of superhero characters, for many Chinese, the sole and only local superhero is the Monkey King, the Monkey King, who stood against the rules set by the celestial and underworld gods. The Monkey King is a sort of a tragic hero who keeps trying even though he knows some things are insurmountable. After all the hardships they have to face, the travellers are stripped of their humanity when they become gods who lead lives with no feelings and in which nothing interesting happens.

The project, codenamed Tengyun [means 'ride the clouds'] was first revealed in 2016. In myths and legends, Tengyun means that immortals fly by clouds. In Taoist lwritings, it refers to the dirty air in the human body, and may be translated as driving the cloud; or a scend to heaven and go to heaven. The speed is high and very fast.

A Space plane is a crucial weapon of the future and represents the trend of integrating aviation and space technologies. Many countries have been developing space planes, including the US with its X-37B, which many military observers claim is a prototype space fighter. A space plane can be used for reconnaissance, anti-satellite, anti-ballistic missile and ground attacks if used as a weapon, the military expert said, noting that it can also send satellites and astronauts into space at a lower cost than rockets, because it is reusable and uses standard airports.

Two-stage-to-orbit (TSTO) means the space plane consists of two aircraft, with the first stage carrying the second stage, The first stage will provide power to the space plane upon takeoff, and when it reaches a certain height and speed, the second stage will detach from it and power itself further into space, as the first stage will land just like a normal plane.

The Tengyun project aims to develop a reusable two-stage-to-orbit spaceplane which consists of planes for both stages. Demonstration and verification of the Tengyun horizontal takeoff, horizontal landing (HTHL) spacecraft is to be completed by 2025. Tengyun is understood to be unrelated to an apparent September “reusable experimental spacecraft” test launched by a Long March 2F. Tengyun will, according to previous reports, be capable of carrying both crew and cargo to orbit. It will also be able to release satellites into orbit. Zhang Hongwen of CASIC’s third research institute said in 2018 that the research was at an early stage.

The spaceplane is composed of two planes, with the larger aircraft acting as a carrier aircraft. A small scale model was shown at the Zhuhai Airshow 2018. A space plane can be used for reconnaissance, anti-satellite, anti-ballistic missile and ground attacks if used as a weapon, the military expert said, noting that it can also send satellites and astronauts into space at a lower cost than rockets, because it is reusable and uses standard airports.

In October 2019 the First Research Institute of the Chinese Academy of Aerospace and Aerodynamics successfully conducted a wind tunnel experiment, in which the second-stage aircraft freely detached from the first-stage aircraft of a two-stage-to-orbit (TSTO) space plane. TSTO means the space plane consists of two aircraft, with the first stage carrying the second stage. The first stage will provide power to the space plane upon takeoff, and when it reaches a certain height and speed, the second stage will detach from it and power itself further into space, as the first stage will land just like a normal plane,

China is reported to be developing a space plane that would go from runway to orbit and back down again at hypersonic speeds. Researchers at the China Academy of Launch Vehicle Technology (CALT) are developing a spacecraft that will be propelled by a combination of turbine engine, ramjet and rocket engine, according to the academy, which is part of China Aerospace Science and Technology Corp (CATSC). When completed, the hypersonic space plane would boost the Asian country to the forefront of the aerospace industry — eclipsing the capabilities of the now retired Space Shuttle. The cutting-edge aerospace vehicle that, if successful, will enable the public to make space journeys. China Central Television (CCTV) reported 02 Augsut 2016 that scientists from China Aerospace Science and Technology Corporation have started work on a new vehicle integrating different kinds of engine technologies. In early July 2016, China Academy of Launch Vehicle Technology, an institute of the corporation, said on its website that it was coordinating with other institutes to study the new vehicle.

The space plane would use a combined cycle engine that would allow it to take off from an airport runway and fly into orbit. The horizontal takeoff would be powered by a turbofan or turbojet engine, followed by a ramjet engine to propel the plane upward through atmosphere. As the spacecraft reaches supersonic speeds, it then will switch to a scramjet engine that would push it through the “near space” portion of the atmosphere from 20 kilometers to 100 kilometers above sea level. Once it is through this “near space” environment, the space plane finally will use its onboard rocket motors to maneuver into orbit. The rocket-based combined-cycle engine (RBCC). The RBCC results in a substantial (appx. 50%) reduction in scramjet maximum speed required to be attained.

Some single-stage hypersonic vehicle designs rely on a low-speed propulsion system responsible for achieving the speed necessary for ramjet operation, and a high-speed propulsion system that operates as a ramjet or a combined ramjet/scramjet. Such systems, however, have several disadvantages. For example, the low-speed propulsion system typically relies on conventional gas turbine engine technology to achieve ramjet viable speeds (less than approximately Mach 3). The overall vehicle weight is sensitive to the weight of the combined propulsion system. Since development and operational cost typically scale with vehicle weight raised to an exponent, it is important to keep vehicle and propulsion weight to a minimum.

Just like the US space shuttle, the Chinese version will be reusable, allowing the astronauts to orbit, land, and take off again with only minimal repairs. This reusability would lower costs for the space program and allow Chinese astronauts to access Earth’s orbit more frequently. China’s hypersonic shuttle was reported in 2016 to be slated for development and testing over the next three to five years, with a target service date of 2030. The space plane was similar to the British Skylon, which also used a combined cycle engine and rocket motors to achieve hypersonic launches. Instead of a scramjet for hypersonic flight, the British version of the space plane used pre-cooled jet engines. Both space planes were under development and are expected to begin flight testing in 2020 with deployment on or before 2030.

In a broadcast on China state television broadcaster CCTV, CASTC engineer Yang Yang also alluded to a possibility of using the space plane for tourism. Because of its combined cycle engine, the space plane will propel itself into space much more gradually than a rocket engine-powered craft. This gentle launch reduces the physical strain on passengers, improving the “ease of access to space for untrained persons.”

Zhang Yong, deputy chief designer at the academy's research and development center, said that with a much lower operational cost and a higher safety guarantee compared with rockets, the space vehicle will be capable of transporting humans hundreds of kilometers above the Earth. It will be used for astronaut missions and for space travel by the public, he added. It will have a huge potential in space tourism or intercontinental passenger travel, Zhang said. "Space travelers will have a short period of weightlessness when the vehicle reaches an altitude of about 100 kilometers. If the spacecraft continues to fly up to 400 km above Earth, passengers will experience what it is like to be in a space station," he said.

Yang Yang, a designer at the academy's Institute of Combined-Cycle Aerospace Vehicle Technology, said all the space-exploring nations now use rockets for such activity. "Rockets have an ultrafast acceleration during flight, resulting in very strict requirements for astronauts' physical condition. In comparison, the combined-powered spacecraft will gather speed slowly and gently, making the air pressure acceptable to non-astronauts," he said. The space vehicle can also be used to deploy satellites, he added.

Wang Ya'nan, editor-in-chief of Aerospace Knowledge magazine, said, "Such a vehicle will be able to fly over the Pacific Ocean within an hour, because it will travel in near-space at a speed of 7,000 km/h." Yang Yuguang, secretary of the International Astronautical Federation's Space Transportation Committee, said the rocket-based combined cycle and turbine-based combined cycle technologies will be the key to the success of the project.

Project Tengyun could provide round-trip travel between Earth and space, according to a statement 12 March 2018 Zhang Hongwen, president of the Third Academy of China Aerospace Science and Industry Corporation and a member of the 13th National Committee of the Chinese People's Political Consultative Conference. The China Academy of Launch Vehicle Technology has started a space travel project that seeks to reduce the cost of space travel through developing reusable carriers and lowering the flight trajectory, "The key issue to solve is to reach a high-enough accelerated speed from take-off from a normal airport, theoretically the joint work of an aviation engine and rocket engine," Jiao Weixin, a space professor at Peking University, said 20 March 2018. Although both plane and rocket technologies have been mastered independently, Jiao said, the question is how to combine them cost-effectively. Considering the high cost, once the research is done, the first applications should be made in the military field rather than popular space travel, according to Jiao.

China made an important breakthrough in developing its own space plane, a genre of aircraft that is expected to become a crucial weapon in the future, a state-owned research institute said 23 October 2018. The First Research Institute of the Chinese Academy of Aerospace and Aerodynamics successfully conducted a wind tunnel experiment, in which the second-stage aircraft freely detached from the first-stage aircraft of a two-stage-to-orbit (TSTO) space plane, according to a statement the academy released. When detaching, there is very strong and complicated flow distribution that could affect the flight of the aircraft, so the two stages must be separated fast and safely.

The experiment solved multiple technical difficulties and set up a universal wind tunnel experiment protocol, providing an advanced method to develop future space planes, the statement said. With the successful development of technologies like scramjet engines, technical research has gone past the concept stage.

CASIC revealed at the October 2020 China International Commercial Aerospace Forum that by 2025, China will build a reusable spaceplane, named Tengyun. The Tengyun project aims to develop a reusable two-stage-to-orbit spaceplane which consists of planes for both stages They even claim, the spaceplane is "already under construction". But this phrase ranslates better into "currently being worked on" or "currently being developed" which typically refers to the overall project, not necessarily a prototype or a physical sample. If they wanted to specify that something was under construction, they would have written "assembly" or a similar phrase. Other sources mention that a demonstration/experimental flight has been successful, marking a major milestone breakthrough, while others mention that only a full-scale prototype was expected by 2025, and that commercial service will not begin until 2030.

Gee Whiz!! Americans have been doing such studies for half a century, and still haven't come up with a workable design.

Launch vehicles or rocket boosters are primarily used to deliver satellites to orbit or weapons over large distances (ICBMs). However, most of the existing rocket designs are expendable, making them costly for most missions and less competitive in the world launch market. A transatmospheric vehicle (TAV) or reusable launch vehicle (RLV) would be capable of returning to earth to be reused after minimal refurbishment and refueling. TAVs most likely would have aerodynamic and operability characteristics similar to conventional aircraft but have capability of delivering payloads to low earth orbit (LEO). The promise of TAVs is that their reusability would potentially allow them to launch payloads into orbit at much lower cost than current expendable rockets.

Airbreathing propulsion engines have several advantages over expendable rockets, namely, they do not require stored liquid oxygen, which results in smaller and less costly launch vehicles. In addition, airbreathing engines don't have to rely strictly on engine thrust but can utilize available aerodynamic forces, thus resulting in far greater maneuverability. This can also manifest itself in greater vehicle safety since missions can be aborted much easier. Alternatives to all-rocket propulsion systems include a combination of gas turbine jet engines, ramjets, scramjets and rockets that can be integrated into a combined cycle airbreathing propulsion system.

Gas turbine engines, and the devices that are powered by gas turbine engines, are limited in overall design and performance by mechanical, material, and thermodynamic laws. They are further constricted by the design limitations of the three elements that make up the baseline design of gas turbine engines: the compressor, the combustor and the turbine. In turbines for aircraft, these three engine sections are contained inside of the outer turbine casing and are centered on a load bearing drive shaft that connects the turbine (on the rearward portion of the drive shaft) with the compressor (on the forward portion of the drive shaft). Typically the drive shaft is a twin or triple spool design, consisting of two or three concentric rotating shafts nested one inside the other. The different spools allow the turbine assembly and the compressor assembly, each of which is connected to one of the spools of the drive shaft, to rotate at different speeds.

The turbine is optimized to run at one particular speed for combustion and thrust processes, and the compressor is optimized at a different speed to more efficiently compress incoming air at the inlet face and raise the air pressure to a significant point to where there is a pressure ratio differential, significant enough to provide combustion. Highly compressed air at ratios of 30:1 to 40:1 ignites when mixed with atomized fuel in the combustor. The difference in speeds of the spools is typically accomplished by reduction gears to accommodate the required speeds for combustion and propulsion operation.

The compressor assembly consists of numerous compressor stages, each of which is made up of a rotor and a diffuser, the number of stages dependent upon the total pressure ratio increase required to achieve combustion and produce the desired thrust. The rotor is a series of rotating airfoil blades, or fans (attached to the shaft), which converge the air, i.e., compressing the volume of air and increasing it's velocity, on the intake side of the blade, by passing it into a smaller volumes (convergent channels between airfoil rotor blades) in each the rotor chamber. Adjacent to each rotor is a diffuser (or stator). The diffuser is a fixed, non-rotating disc of airfoil stators whose sole purpose is to reduce the air velocity from the rotor and increase the pressure. The diffuser slows the air down by passing it through divergent (expanding) channels between the airfoil stators, thus recovering the pressure. Upon entering the diffuser the air passes from a narrow opening on the intake side of the diffuser into a gradually enlarging chamber (diffuser) that slows the velocity and raises the pressure of the air. Each compressor stage is made up of a compressor rotor and a diffuser (stator) disc. There are as many stages of the compressor as are required to get the air to the required air temperature and compression ratio (in high performance aircraft turbines usually in between 12:1 to 30:1 dependent on combustor design, flight and speed envelope and turbine thrust requirements prior to entering the combustor.

In the combustor, the high pressure, high temperature, expanding air mixes in a swirl of hot vaporized fuel and ignites to form a controllable flame front. The flame front expands as it combusts, rotating and driving turbine blades as the flame front exits the engine. The turbine assembly consists of several sets of rotating turbine blades connected to the drive shaft and angled so that the thrust of the flame front causes the blades to rotate. The turbine blades, being connected to the drive shaft, cause the drive shaft to rotate and thus the compressor blades to rotate, consequently more air is compressed and the cycle starts all over again.

Advanced turbojet engines, such as found in fighter aircraft, rely on compressing the air, injecting the fuel into it, burning the mixture, and expanding the combustion products through the nozzle to provide thrust at much higher specific impulses (Isp) than rocket engines. Turbojets can be used to provide horizontal takeoff--like conventional airplanes--and are currently materials limited to Mach 2-3 so as to prevent overheating and damage to the turbine blades. At this point another form of propulsion engine, called a ramjet, takes over. This is in lieu of undertaking an expensive development of high-temperature gas turbine blade materials technology to increase the maximum upper limit to approximately Mach 3-4. The ramjet engine operates by using a specially designed inlet to scoop up the ram air, slow it down and then compress it while the vehicle is flying through the atmosphere. Fuel is injected into the air, mixed with it, combusted and then expanded through the nozzle to provide thrust in a similar fashion to the turbojet. Ramjet engines operate most efficiently at vehicle speeds beyond Mach 2-3. A ramjet can be readily integrated into a turbojet engine. The turbojet by itself would operate from take-off to ramjet takeover, and the ramjet would then power the vehicle to its velocity limit of about Mach 6. Above this limit the combustion chamber temperature becomes very high, causing the combustion products to dissociate, which in turn reduces vehicle thrust.

To operate at still higher vehicle speeds, supersonic combustion ramjets, or scramjets as they are called, would be employed. Again, fuel is injected, mixed and combusted with the air, but at supersonic speeds, thus necessitating a different fuel injection scheme than that used by the ramjet. As the vehicle continues to accelerate into the upper atmosphere, rocket engines may be required to supplement the scramjet engine(s) for Mach numbers above 10-12. Certainly rocket engines would be required if orbit insertion and maneuvering in space (above Mach 18) were required.

One way to eliminate the ramjet and its weight impact from the high speed flowpath is to close the Mach number gap between turbojets and scramjets. This can be accomplished by extending the maximum Mach number range of the gas turbine (turbojet) engine operability beyond Mach 3 and/or reducing the minimum Mach number range of scramjet operability to below Mach 6. However, a substantial investment on the order of hundreds of millions to billions of dollars may be required to advance the gas turbine art so as to minimize the Mach number gap. An alternate approach is to combine the ramjet flowpath with the turbine engine. This creates synergy since the ramjet can utilize the isolator that is already required by the turbine engine in a typical turbine based combined cycle concept installation, rather than creating a second isolator in the high speed flowpath. Further synergy can also be obtained by combining the turbojet engine afterburner with a ramjet combustor, which will then substantially reduce the length and weight of the combined propulsion system leading to significantly better vehicle performance.