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Use wechat scan QR code < / P > < p > to share with friends and circle of friends < / P > < p > -- Xinhua News Agency news: according to < a target = "_ blank" href=" https://news.163.com/news/search?keyword=%E7%BE%8E%E5%9B%BD "> US space agency reported on April 19 that the US" smart "spacecraft < a target ="_ blank" href=" https://news.163.com/news/search?keyword=%E7%81%AB%E6%98%9F "> Mars < / a > < a target ="_ blank" href=" https://news.163.com/news/search?keyword=%E7%9B%B4%E5%8D%87%E6%9C%BA "> the helicopter has completed its first flight. Background < / b > < / P > < p > < b > wit was launched from Earth on July 30, 2020 with the Mars rover willpower, and successfully reached Mars orbit in February this year. Since then, the helicopter has landed on the surface of Mars with the rover, deployed solar panels to power itself, and prepared for its first test flight on the 11th. However, in the process of rotor test, the airborne computer has a failure. < / P > < p > the fault occurs when the helicopter attempts to switch from "pre flight mode" to "flight mode". NASA said a software update was necessary to solve the problem. The agency now has to develop, test and upload new software to the flight controller. Then, the mission team must restart the smart to continue testing as planned. < / P > < p > software failure delayed the first brief test flight of the smart. NASA's plan is for the helicopter to take off about 3 meters, hover for about 30 seconds, and then land safely in the right position. This is a very easy task for UAVs on earth, but it will be a challenging feat on the red planet, which is more than 160 million kilometers away from the earth. < / P > < p > the atmosphere of Mars is about 100 times thinner than that of the earth, which makes it more difficult for aircraft to take off and fly. To solve this problem, the rotor speed of the smart needs to reach 2500 rpm, which is much faster than the passenger helicopter on earth. In addition, because Mars is too far away from the earth and the signal delay time is too long, it is obviously unrealistic to pass the earth remote control test. Therefore, the whole testing process must be automatic. < / P > < p > NASA hopes that the smart will conduct five aerial demonstrations in 30 days, and each one will be more challenging than the previous one. The first step is to prove that the smart can fly, and the final step is to test how far it can fly. Wit's goal is to increase the way NASA explores other planets. "When we explore the surface of Mars, we may find that the terrain is too dangerous, the distance is too far or the range is too large for the rover to do the work effectively or efficiently," said Dave Lavery, director of NASA's Mars helicopter project < / P > < p > < / P > < p > once a new test date is determined, NASA plans to send the flight plan of the smart to Mars in advance, wait for the helicopter to restart and perform the scheduled mission, and send back information about its performance. (Xiaoxiao) < / P > < p > < b > related reading: < / b > < / P > < p > < A=“ https://www.163.com/dy/article/G78KNTQ805329CR2.html " target="_ How difficult is it to fly on Mars when self "urlmacroreplace" false "style =" line height: 1; "> < b > US $47222, 1g smart helicopter, taking off is equal to success? < / b > < / a > < / P > < p > < / P > < p > in order to cooperate with the Mars 2020 exploration mission, NASA's Jet Propulsion Laboratory has built an unmanned helicopter, which weighs only 1.8kg, but costs a total of $85 million, equivalent to $47222 per gram! Considering that the international price of gold is 61.66 US dollars per gram, the price of this small aircraft called "smart" is 766 times that of gold per gram. It should not be objected to saying that it is "the most expensive in history". < / P > < p > Mars helicopter wit < / P > < p > what kind of scientific mission is it shouldering? NASA's expectation of it is very simple, three words: fly. < / P > < p > the mission is so simple that the "smart" does not carry any scientific equipment, but only two cameras and a low bandwidth wireless transmission device, which is responsible for transmitting photos of the flight process to the Mars rover within 1 km. Of course, because Mars is too far away from the earth, it takes at least ten minutes for electromagnetic waves to come back. It is not realistic to fly a remote-controlled UAV from the ground. Therefore, the "smart" will "fly autonomously" according to the procedures set on the ground and the data from the sensors. < / P > < p > flight simulation animation < / P > < p > a friend said, NASA is stupid! It's just about flying. It'll take Dajiang minutes to get things done. It's less than 10000 yuan. You don't have to say that it's not really possible to use Dajiang, because the environment on Mars is totally different from that on earth. < / P > < p > < / P > < p > the radius of Mars is about half of that of the earth, and the average density is less than that of the earth, so the gravity on the surface of Mars is very low. If a beautiful girl weighing 100 kg goes to Mars to weigh herself, she will only weigh 38 kg. That is to say, the 1.8kg "smart" on the ground only needs 0.68kg of thrust on the surface of Mars (almost three gears of electric fan) to fly. Is it easy? < / P > < p > successful launch test on Mars < / P > < p > but wait! You may not know that the Martian atmosphere is extremely thin, the surface atmospheric pressure is only 0.6% of the earth's sea level, the electric fan on three gear is like you yawn. The air density on Mars is almost equal to the air density at the height of 34 km of the earth. Only one plane on the earth can fly to such a high altitude. In 1977, the MiG-25 of the former Soviet Union briefly rushed to the height of 37650 meters, and the second highest limit for the "Blackbird" of the United States was 26600 meters. 34 kilometers is close to a vacuum. Don't even think about the helicopter. The MiG-25 and blackbird look like it's not easy for the smart to fly on Mars. < / P > < p > although the body of Mars helicopter is small and its total weight is only 1.8kg, JPL has equipped it with two pairs of "huge" carbon fiber propellers with a diameter of 1.2m; in order to fly, the speed of propellers should reach 2400rpm and the tip speed is close to Mach 0.7. You may say that 2400 is not fast, but compared with such a large propeller and such a light weight, it is still a little difficult to achieve accurate control. In other words, its two propellers are overlapped up and down. The lower propeller rotates clockwise and the upper propeller rotates counterclockwise, which is similar to what we usually seeMost helicopters are different. And why? < / P > < p > < / P > < p > most of our common helicopters are supported by a main rotor and a tail rotor on the tail. When the main rotor rotates, it will push the air, and the reaction force of the air will produce a reverse torque on the rotor. When the rotor rotates counterclockwise, the fuselage will rotate clockwise, which is very dangerous and will cause the aircraft to lose control. We also install a propeller on the tail of the helicopter, let it blow to the left, through the thrust to compensate the torque of the fuselage, can achieve the effect of controlling the direction. < / P > < p > helicopter mechanics diagram < / P > < p > most helicopters adopt this method, because its structure is very simple, it does not need too complex mechanical components, and its reliability is higher. But its mechanical efficiency is relatively low, because a lot of energy is used to counteract torque rather than to generate lift. In 1754, Russian scientists invented the coaxial twin screw helicopter, which installed a pair of counter rotating propellers on the same shaft. When the two propellers rotate at the same speed, the torque generated by them will cancel each other, so the fuselage can maintain the direction and the tail rotor is not needed to correct the deviation. < / P > < p > coaxial twin-screw helicopter does not need tail rotor correction < / P > < p > the advantages of coaxial twin-screw helicopter are obvious, it significantly improves the lift of the propeller, stable output power, small blade vibration during flight, and reduces the phenomenon of backward blade stall. Its disadvantage is that the structure of rotating parts is complex, and due to the relationship between the air flow disturbance between the blades, the thrust of two pairs of blades is only 15% more than that of a pair of blades, which is not the relationship of 1 + 1 = 2 as we imagine. "Smart" is equipped with a set of 2 ah Sony lithium batteries, which can only fly for 90 seconds and about 50 meters at most. After that, it has to stop and use solar energy to charge. The light on the surface of Mars is weak, and the charging time may be very long. < / P > < p > NASA always spends money on space exploration without blinking an eye. A Mars rover named "willpower" costs $2.725 billion and $85 million to build a small plane - although its mission is just to fly and take a short video, that's reasonable. After all, this is the first flight on Mars. < / P > < p > maybe we will take a plane to Mars next time when tianwen-2 visits Mars. Of course, the price will not be so expensive. I'm afraid some people will call it "loser" for the $850000 one plane like "smart"! < / P > < p > < / P > < p > who knows?

2023-03-22 10:04:32