Recently, at the Donghu Laboratory in Hubei Province, researchers successfully accelerated a 1.1-ton test vehicle to 650 kilometers per hour within a distance of 1000 meters using suspension support and electromagnetic propulsion. The test speed broke the global record for similar platforms and became the fastest maglev test speed in the world. it happens that there is a similar case. In April of this year, China Aerospace Science and Industry Corporation announced at its vacuum tube maglev test base in Datong, Shanxi that the prototype of the new generation of "super high-speed rail" had completed its first ultra high speed test, with a speed exceeding 1000 kilometers per hour. Through the above news, we can feel the rapid development of ultra high speed rail technology, and also feel that the dream of human travel in "supersonic vehicles" is slowly becoming a reality. Generally speaking, at standard atmospheric pressure, the speed of sound is approximately 340 meters per second (1224 kilometers per hour). Imagine if future vehicles could travel at the speed of sound, what would that be? Let's perceive it concretely from the scenes of life. Taking Beijing to Shanghai as an example. The distance between Beijing and Shanghai is about 1200 kilometers, and if passengers choose to travel by car, it will take more than ten hours; If taking a commercial plane, it takes about 2 hours; If there is an "ultrasonic vehicle", theoretically it only takes about 60 minutes for passengers to cross Beijing and Shanghai. So, what is the current development status of "supersonic vehicles"? How far are people from traveling by high-speed train? In this issue, let's explore its development path, current situation, and prospects. The long-term effort to break through the "curse" of sound barrier is supersonic, as the name suggests, which refers to the movement speed of an object exceeding the speed of sound. In order to facilitate the description of motion approaching or exceeding the speed of sound, the scientific community has introduced a unit - Mach. 1 Mach is equal to 1 times the speed of sound. In fact, ultrasound is not an unattainable abstract concept. On the shooting range, the speed of bullets when fired from the barrel can reach more than twice the speed of sound; In the park, when the old man who exercises in the morning shakes his whip, the tip of the whip will break through the speed of sound and produce a "sonic boom", making a loud "pop" sound; In space, many spacecraft manufactured by humans have speeds far exceeding the speed of sound... The pursuit of speed by humans has never ceased. At the beginning of the 20th century, with the development of aviation technology, the speed of airplanes gradually increased. Pilots have found that when the speed of the aircraft approaches the speed of sound, the fuselage of the aircraft will vibrate violently, making control exceptionally difficult. This seems to have built an invisible barrier that is difficult to cross in front of humanity, a phenomenon later known as the 'sound barrier'. In fact, 'sound barrier' is caused by a sudden change in aerodynamic characteristics during supersonic flight of an aircraft. The essence of sound propagation is the vibration transmission of air molecules. When an object moves at subsonic speed (below the speed of sound), the air in front of it will slowly flow towards both sides of the object like "receiving advance notice"; When the speed of an object approaches or exceeds the speed of sound, air molecules cannot avoid it in time and will accumulate in front of the object, forming a strong compression wave, which is called a "shock wave". Compressive waves cause a sharp increase in drag and unstable lift on objects, which is one of the reasons why early aircraft had difficulty breaking through the speed of sound. The historic period of breaking through the curse of voice barrier began in the 1940s. After decades of development, weapons and equipment such as X-1 test aircraft, F-100 supersonic jet fighter, and "Zircon" and "Dagger" hypersonic missiles have emerged successively. At the same time, ultrasonic technology has also been extended to the civilian field. In 1976, the "Concorde" passenger plane jointly developed by Britain and France was put into operation. This aircraft is capable of cruising across the Atlantic at a speed of approximately 2 Mach, reducing the travel time from Paris/London to New York to 3.5 hours, saving about half of the time compared to regular aircraft. However, the Concorde also had fatal flaws: the "sonic boom" noise generated during flight prohibited it from supersonic flight over land and only allowed it to fly on transoceanic routes; The fuel consumption is more than twice that of ordinary subsonic aircraft, and the ticket price is high... It must be mentioned that in 2000, the "Concorde" aircraft crashed and was eventually retired three years later, causing civilian supersonic aircraft to fall into silence. In recent years, with the advancement of materials science, aerodynamics, and propulsion technology, civil supersonic aircraft have once again become a hot topic in the industry. It is reported that many companies around the world are developing a new generation of supersonic aircraft to solve problems such as "sonic boom" noise pollution that have previously occurred. Exploring the key technology of supersonic flight requires breakthroughs in multidisciplinary techniques to enable aircraft to achieve stable flight beyond sound speed. These technologies are like precision gears, jointly driving the aircraft to achieve supersonic flight. Power system - the "super heart" of supersonic flight. When the aircraft breaks through the speed of sound, it needs to overcome huge shock wave resistance, and the process of overcoming resistance cannot be separated from the specially designed supersonic engine. The variable intake duct of a supersonic engine is like a "speed bump" for the airflow. With the help of adjustable geometric surfaces, the supersonic airflow can be reduced to subsonic airflow, which is then pressurized and sent into the combustion chamber. At the same time, the afterburner located upstream of the engine nozzle can instantly increase thrust by more than 50% by injecting additional fuel into the high-temperature exhaust gas for secondary combustion. In addition, some supersonic aircraft use combined cycle engines, which further expands the applicable speed range of the aircraft. The flexible combination mode design makes the combined cycle engine an ideal power core for hypersonic flight. Pneumatic layout - the "body code" for taming airflow. Ordinary aircraft with straight wings perform well at low speeds, but once the flight speed approaches the speed of sound, the air in front of the aircraft gathers, like a sudden wall standing in front of the aircraft, causing it to experience tremendous shock resistance. The earliest "wall breaking weapon" was a swept wing configuration wing. The swept wing configuration refers to tilting the wing backwards, which can effectively disperse and weaken shock wave resistance. For example, the first generation of supersonic fighter jets after World War II commonly adopted this design method to assist the aircraft in easily crossing sound barriers. The delta wing configuration that emerged later had sharp leading edges and high structural strength. It could efficiently "split" shock waves during high-speed flight, while generating leading edge vortices and effective vortex lift during low-speed takeoff and landing. The Concorde supersonic passenger plane, with its triangular wing configuration, tamed the airflow and flew at high altitude at a speed of 2 Mach. Materials Science - Armor for Resisting High Temperatures. When an object flies at supersonic speed, it encounters strong compression effects caused by shock waves, which not only bring huge resistance, but also cause strong aerodynamic heating phenomena. When the speed of the aircraft reaches 2 Mach, the surface temperature of the aircraft can reach 250 ℃; When the speed reaches 4 Mach, the temperature will soar above 900 ℃; A spacecraft that enters the atmosphere at a speed of 25 Mach has a surface temperature sufficient to melt steel. Hypersonic aircraft need to develop advanced materials that can withstand this' fire test 'in order to fly safely. Researchers were the first to discover titanium alloys. This material is about 40% lighter than steel and can maintain excellent structural strength even in high temperature environments of 300 to 500 ℃. Carbon based composite materials and ceramic based composite materials are two other types of "high-temperature armor" suitable for hypersonic aircraft discovered by researchers. Ceramic based composite materials used for engine nozzles can directly withstand high temperatures above 1300 ℃, becoming a "heat-resistant barrier" for aircraft to isolate flames; The reinforced carbon composite material used for the nose cone and wing leading edge of the space shuttle is like a sturdy "high-temperature shield" that can withstand extreme aerodynamic heat of up to 1500 ℃ when the spacecraft re enters the atmosphere. There is also a resin based composite ablative material that can be regarded as a protective hero who sacrifices himself to protect the master. For example, the resin based composite material coated on the surface of the return capsule of China's Shenzhou spacecraft will undergo layer by layer erosion and carbonization when exposed to high temperatures, consuming its own materials and carrying away a large amount of heat. Even if the spacecraft enters the atmosphere at a super high speed of 25 Mach, the temperature inside the capsule can still be maintained within an acceptable range for the human body. In addition, there is also an active cooling technology, which can be said to be the "portable air conditioning" of aircraft. This cooling technology fills the cabin walls with coolant, which vaporizes like "sweating" when heated, absorbing a large amount of heat and instantly taking away high temperatures. With the arrival of the ultrasonic era, the application of ultrasonic technology has gradually radiated to the ground field, as we shuttle from the clouds to the ground at high speed. Looking around the world, many countries have turned their attention to the field of "high-speed flying trains". As early as the 1980s, Chinese scientists began to deeply cultivate the magnetic levitation technology applied to "high-speed flying trains". In 2001, the world's first manned high-temperature superconducting maglev experimental vehicle, the Century, developed by Southwest Jiaotong University, made its debut. Although its top speed was only 10 kilometers per hour, it verified the core principles of self suspension and self guidance in maglev technology. In 2013, Chinese scientists proposed the concept of "super high-speed rail", with the core being "vacuum pipeline+maglev technology". In April this year, China Aerospace Science and Industry Corporation announced at its vacuum tube maglev test base in Datong, Shanxi that the new generation of "super high-speed rail" full-size prototype vehicle completed its first ultra high speed test, with a speed exceeding 1000 kilometers per hour. This milestone event not only marks China's global leading position in the field of ultra high speed rail transit, but also indicates that human land transportation may enter the "supersonic era". One of the key factors in achieving the transition from "soaring through the sky" to "galloping on the ground" using supersonic technology is to reduce air resistance. When the train speed exceeds 600 kilometers per hour, more than 80% of the resistance comes from the air. For a regular high-speed railway running at a speed of 300 kilometers per hour, an "air wall" is formed in front of the train during travel. For every 1 kilometer forward, the train pushes away 200 tons of air. By utilizing a vacuum pipeline environment, this problem can be effectively solved. It is reported that the train operates in a pipeline close to vacuum, reducing air resistance to 3% of traditional high-speed trains and consuming only 1/10 of the energy of an airplane. This environment not only greatly improves the running speed of trains, but also reduces the noise phenomenon during train operation. In addition, another key factor for the "high-speed flying train" to achieve "ground speed" is the use of high-temperature superconducting maglev technology. By utilizing the principle of "same sex repulsion, opposite sex attraction", the magnetic field on the track in front of the train attracts the train, while the magnetic field on the track behind the train repels it, thereby generating a strong linear thrust that drives the train forward. This "non-contact" driving method fundamentally avoids mechanical friction and is a prerequisite for achieving ultra high speed operation of trains with a speed of over 1000 kilometers per hour. However, if the "high-speed flying train" wants to smoothly enter the application and market, it still faces some challenges. ——Sealing and maintenance of vacuum pipelines. The smooth operation of the "high-speed flying train" requires solving the problem of vacuum maintenance in pipelines that are hundreds of kilometers long. On the one hand, the sealing and maintenance costs of vacuum pipelines are extremely high; On the other hand, once the vacuum environment leaks, the train will face the danger of pressure loss, posing a threat to passenger safety. ——Strength and toughness of pipeline materials. The vacuum pipeline is subjected to atmospheric pressure on the outside and equipped with suspension, pumping and pressure reducing equipment inside, which places extremely high demands on the material performance of the pipeline. Choose high strength and toughness