Not long ago, NASA announced a very avant-garde, very scientific and technological future space vehicle propulsion system, which is led by Marshall Space Center, a subsidiary of NASA. The full name of the system is heliopause electrostatic rapid transit system, or solar electric sail propulsion system Unified HERTS. Does the appearance alone have the feeling of future technology? Is it subverting your understanding of aircraft?



The structure of electronic sail



The electronic sail is not as complete as the traditional sail. As the main part of the propulsion system, there are some special thin aluminum wires. Yes, you are right. Those thin wires are aluminum wires. Of course, this is not the common aluminum wire in our life. These aluminum wires are very thin and very long, with a diameter of 1 mm. They are about the same thickness as a paper clip, and they are super long, about 12.5 miles, or about 20 kilometers. What is the concept of this length? It's almost 219 football fields together. An electronic sail usually consists of 10-20 aluminum wires, radiating from the center to the surrounding. After the rocket reaches the designated position, it extends the aluminum wire from the center to both ends, and two small rockets propel it to complete the fan-shaped deployment task of the aluminum wire group. Make the electronic sail complete the final deployment form.



Power source of e-sail



Of course, it's not that the electronic sail propulsion system can set sail in space. The important thing in interstellar navigation is propulsion power. The traditional space engines need their own propellants, which will occupy a large proportion of the total mass of the rocket, and seriously restrict the payload and flight distance of the spacecraft. Therefore, it is always the direction of scientific research to seek a more effective way of promotion.



Scientists have turned their attention to the sun, the ultimate energy boss in the solar system. The electronic sail is to use the solar wind generated by the sun to propel. Different from the molecular wind on the earth, the solar wind is a flow of charged particles in the supersonic plasma emitted from the upper atmosphere of the sun, which is composed of particles such as protons and electrons. The effect of their flow is very similar to that of air flow. The density of the solar wind is very thin and insignificant. Generally, in the interplanetary space near the earth, there are several to dozens of particles per cubic centimeter, while the density of the wind on the earth is 268.7 billion molecules per cubic centimeter. However, the strong force of the solar wind is far stronger than the wind on earth. The speed of solar wind near the earth is generally 350-450 kilometers per second, and it can reach 800 kilometers per second when it is strong. It may not feel like just looking at the numbers. We need to know that the violent wind on the earth is a typhoon. The wind speed of typhoon 12 is only over 32.5 meters per second, and such wind speed is already a disaster.



Because of the thinness of the solar wind, we have no direct perception of it. But its ultra-high speed is the key to the black technology of e-sail. In fact, some scientists have tried to make interstellar flight through the solar wind before. NASA successfully launched a small solar sail powered satellite in 2010. In May of the same year, Japan's space agency launched a space probe called Ikaros, proving the possibility of solar sails for interstellar navigation. Unlike previous solar sails, which use extremely thin metal plates with sail effect and rely on solar pressure to propel, this e-sail project uses the aluminum wires mentioned above. These aluminum wires will be positively charged and use the force that repels the particles in the solar wind to provide power for spacecraft and spacecraft. In theory, it doesn't need any propellant. As long as there is sunlight, it can fly, and the speed is far faster than the existing aircraft. It is expected that the high speed can reach 400-750 kilometers per second.



High speed movement of electronic sail



In order to better understand the e-sail, a new unit needs to be introduced. The astronomical unit Au is often used in astronomy instead of the length unit we usually use to express distance. An Au is the average distance from the sun to the earth, which is about 149.6 million kilometers. The farther away from the sun, the thinner the solar wind, in order to ensure sufficient thrust and acceleration, the effective area of the electronic sail will increase with the voyage. At 1AU, the effective area is 601 square kilometers, only a little smaller than that of downtown Chicago; at 5aU, the effective area can reach 1200 square kilometers, close to the size of Los Angeles.



Another advantage of e-sail is that its acceleration distance is far beyond that of solar sail. Generally, when the sail sails past 5aU, its acceleration will stop due to the dissipation of solar photon energy. Due to the continuous particle flow and the increased effective area, the acceleration of the electronic sail will not stop, but will continue to a distance of 16-20au. As the first human aircraft to reach the edge of the solar system, Voyager completed its mission in 2010 after 35 years of flying. E-sail, on the other hand, can accomplish this task in 12 years or less. Therefore, this black technology may subvert the existing propulsion technology.



Of course, the technology has not entered the launch stage. The number of protons rejected by the wires and the number of electrons attracted by the wires are still being tested at the Marshall Space Flight Center, and the plasma test is in progress to modify the model. It is expected that within 10 years, the e-sail will officially enter the space stage. In fact, no matter what the future of e-sail will be, there will be explosive technological breakthroughs in the future of human spaceflight that will subvert the existing technology, and our pace in space will be further and further. Only breakthrough ideas