Room-temperature superconductors are so popular, how much will this benefit the aerospace industry?

Recently, a South Korean paper claimed to have discovered the world's first room-temperature superconducting material, which attracted public attention. If we ignore the noise on the Internet, we might as well clarify three questions: What is superconductivity and room-temperature superconductivity? In order to achieve relevant achievements, what technical difficulties do researchers need to overcome? If room-temperature superconductivity becomes a reality, what application prospects may it have in the aerospace field?

There are many limitations behind the magic

Before discussing room-temperature superconductivity, we need to understand the concept of superconductivity. The so-called "superconductivity" means that electric current can flow through a conductor without hindrance and generate a strong magnetic field. The most common application scenario of superconductivity in daily life should be the nuclear magnetic resonance machine in the hospital, whose core component is a coil wound with niobium-titanium alloy wire.

However, in order for materials to reach a superconducting state, a large amount of liquid helium and a cryogenic refrigerator are traditionally required to cool them to around -264 degrees Celsius, which undoubtedly comes at a great cost, including huge energy consumption, the high cost of liquid helium, and complex structures. In recent years, with the advancement of material technology, some materials that can exhibit superconducting properties at liquid nitrogen temperatures (about -196 degrees Celsius) or even higher have been discovered and improved, but they are still far from room temperature.

Imaginary picture of space electromagnetic launch device

Superconductivity research was a frontier field in materials science in the 20th century. In 1908, liquid helium was successfully produced, with a boiling point of about minus 269 degrees Celsius, which laid the foundation for superconductivity research. In 1911, researchers discovered that at the extremely low temperature of liquid helium, the resistance of mercury suddenly disappeared. This is considered the "starting point" of superconductivity research. In 1933, German physicists Meissner and Ossenfeld realized that as long as the temperature of the material is lower than the superconducting critical temperature, the total magnetic induction intensity inside it is zero, that is, it has complete anti-magnetism. This is the test standard for superconductivity, the "Meiners effect".

So how does low-temperature superconductivity come about? The answer lies in the exquisite microscopic world.

Classical theory holds that resistance is caused by the collision and obstruction of electrons in wires.

However, in superconducting materials, electrons form pairs of so-called "Cooper pairs" and quickly avoid obstacles like dancing, achieving zero-resistance transmission of current. This wonderful phenomenon is believed to be caused by the vibration of atoms inside the material crystal, which is the "BCS theory" jointly proposed by Bardeen, Cooper, and Schrieffer.

However, due to the extremely low temperature conditions such as liquid helium, superconductivity has long been difficult to be widely used in large-scale engineering, which has also prompted researchers to devote great enthusiasm to the research of "high-temperature" superconductivity. In 1986, scientists were surprised to find that yttrium barium copper oxide, bismuth-based materials, etc. can still exhibit superconductivity in the relatively high liquid nitrogen temperature range. This means that liquid nitrogen, which is easier to obtain and cheaper, can be used as a superconducting coolant.

This breakthrough provides a broader "stage" for the practical application of superconductivity and also provides strong support for the construction of many large scientific facilities. For example, the "Eastern Super Ring" and the International Thermonuclear Experimental Reactor and other facilities have applied new superconducting cables, which effectively reduced the power demand of the refrigeration system.

However, the research on "high-temperature" superconductors seems to have encountered the dilemma of "theory lagging behind reality". Scientists have been trying to explore the mystery, but have not yet fully revealed its specific principles, and basically remain at the hypothesis stage. For example, some scholars believe that the complex interactions between electrons and new condensed matter phenomena may be the main reasons for the birth of "high-temperature" superconductors.

It is not difficult to see that the so-called "high temperature" in the field of superconductivity research is still not something that the general public can experience in their daily lives, so it is even more difficult to obtain superconductivity under room temperature conditions.

Unlimited prospects for aerospace applications

Spaceflight is a great cause of using speed to break free from the gravitational pull of planets, explore and develop the vast space. The most classic spacecraft carrier is the rocket, which generally uses the high-temperature and high-speed jet generated by fuel combustion to generate a strong reaction force to continuously accelerate and lift the payload until it flies out of the atmosphere.

However, most of the existing rockets take off directly from ground launch pads. In order to accelerate and fly away from the troposphere with dense air and high resistance, a large amount of fuel is needed, which also means that the rocket will lose a lot of precious carrying capacity.

In order to solve this problem, space launch agencies have proposed a variety of innovative solutions, including air launch of rockets mounted on aircraft, launch of rockets to high altitudes using giant airships and balloons, and launch of rockets by throwing out centrifuges.

For example, the Pegasus air-launched rocket successfully entered orbit in 1990. Before launch, it was suspended under the belly of a specially modified passenger plane. When the carrier plane was flying at a height of about 13,000 meters at Mach 0.8, the rocket was released, and then the first-stage solid engine was ignited to accelerate the climb.

However, these launch methods all have some drawbacks, especially the high operating and maintenance costs of platforms such as aircraft, limited transportation capacity, and generally only small rockets can be launched, with insufficient orbital capacity. For example, the Pegasus rocket has a 700-kilometer sun-synchronous orbit capacity of just over 200 kilograms, and can only deliver small payloads into orbit. The unit launch cost is higher than many large and medium-sized ground-launched rockets, so the large-scale application of the Pegasus rocket and subsequent air-launched rockets has always been difficult.

However, once room-temperature superconducting materials are developed and successfully put into practical use, the history of space launches is expected to "turn over a new page". For example, researchers and engineers can learn from the principles of maglev trains and electromagnetic catapults to build a new concept of space launch device, whose structure is similar to a maglev train track perpendicular to the ground.

At that time, on the tower, the suspension coils will be responsible for maintaining the launch direction of the rocket and preventing the friction between the rocket and the track from causing resistance, while the acceleration coils will provide the rocket with a strong takeoff thrust to help it quickly break out of the dense air near the ground. When the rocket is fully accelerated by the launch device and breaks out of the troposphere, the first-stage engine will be ignited to continue to accelerate and climb, and finally enter orbit.

Compared with air launch, this launch method basically only consumes electricity. Moreover, since room-temperature superconducting materials do not require complex cooling systems, the scale of the launch device can be made very large. Therefore, it is expected to send heavier payloads into orbit, and the unit launch cost will be significantly reduced. It is likely to give birth to larger spacecraft combinations and new forms of space activities.

In addition to the field of space launches, room-temperature superconducting materials also have broad application prospects in satellites, spacecraft and other spacecraft.

For example, in the process of spacecraft design, it is necessary to take appropriate shielding measures for electronic equipment and sensitive instruments to protect them from external magnetic field interference. Room-temperature superconductors will be the perfect material for magnetic shielding devices. Just make a shell and put the instruments and equipment sensitive to magnetic fields into it to form a stable magnetic field shielding area inside.

In addition, if room-temperature superconducting materials are used to manufacture wires to replace traditional metal wires inside spacecraft, it is expected that not only will power consumption be reduced, but also heat will be significantly reduced, thereby simplifying the design of the power supply and temperature control systems, helping new satellites to have more powerful performance and lighter structure.

In short, superconducting technology has made great progress in just a few decades, bringing new possibilities for human beings to pursue a better life and explore the unknown world. Researchers have continued to deepen their research and experiments on superconductivity, and have been tirelessly exploring and challenging the limits of matter. As a priority application field for many cutting-edge technologies, aerospace will surely shine here once room-temperature superconductivity becomes a reality in the future, helping humans to further explore and develop the vast sky. (Author: Wanmi Qingkong Xiangyu Image source: Science fiction film and television works review expert: Jiang Fan, deputy director of the Science and Technology Committee of China Aerospace Science and Technology Corporation)