Human drone makes its first flight to Mars! What core technologies did you use to hover at a height of 3 meters for 30 seconds?

A piece of good news came from the Jet Propulsion Laboratory, a subsidiary of NASA in the United States, that the Witness drone carried by the Perseverance rover made its maiden flight.

The guy flew 3 meters high and hovered for 30 seconds. You don't look at flying high, and the duration is very short. But it's an uncompromising miracle, the first time a human-built aircraft has taken flight outside of Earth.

I waited until midnight before the Jet Propulsion Laboratory released a more complete flight video. After all, it takes a lot of time to send data back from Mars, which is 55 million kilometers away.

This small drone is called Wisdom, also called "Little Wisdom", with a total weight of 1.8 kilograms. However, this is already the result of JPL's engineers desperately trying to lose weight. The weight of 3 pounds and 6 taels is heavy compared to our common home-use drones. DJI's Phantom series drones only weigh 1.3kg. But the Witness drone is completely different from the drones we commonly use for filming. Our common drones are called "multi-rotors". The Wit is a standard coaxial reverse propeller helicopter configuration.

You must know that the atmosphere on Mars is extremely thin, only 1/100 of that of Earth, which is equivalent to an altitude of 30,000 meters on Earth. Therefore, Wit's propeller is 1.2 meters long, and it rotates 2,500 times a minute, five times faster than ordinary drone propellers. Fortunately, the air on Mars is thin and the resistance is small, otherwise it would not be able to rotate so fast.

Wit has a solar panel overhead. All electricity comes from this solar panel. It takes a full day of sunshine to fully charge the battery. The Wit uses a lithium battery, and the total capacity is similar to that of an ordinary power bank.

Know that lithium batteries are very afraid of freezing. Nowadays, electric vehicles are very popular, but they are not used much in Northeast my country. The winter in the Northeast is very cold, and as soon as the temperature drops, the mileage of electric vehicles keeps dropping. It's colder on Mars. The Jezero crater, where the Perseverance rover is located, has a temperature of minus 83 degrees Celsius at night and minus 22 degrees Celsius during the day. Therefore, 2/3 of the electricity is used to keep warm, and only 1/3 of the electricity is used to fly, and it takes 90 seconds to fly down.

Precisely because Mars is cold, the sun is a little weaker. So the best time to fly is around 11:00 noon local time. It only takes more than a minute to fly, and there is still half a day to recharge after getting down. The electricity accumulated in half a day can sustain this "little smart" through the cold night. If it takes off in the evening, there is not much electricity left, and it is just before the sun goes down. If you want to recharge and can't recharge, you can only wait to die. Therefore, this drone does not fly if it wants to. In any case, the Wit needs to be in the sun on and off for 24 hours in order to be fully charged, so it can't fly several times a month. This drone does not carry any special equipment, that is, it flies up and takes a picture. The processor is Qualcomm Snapdragon 801, and the system is Linux. It looks similar to a mobile phone, but the problem that this drone has to deal with is completely different from that of a mobile phone. Our common civilian drones are equipped with a magnetic compass, which can distinguish east, west, north and south. With a GPS receiver, it can determine its precise position, and a camera with optical flow positioning can rely on vision to judge its own movement. With ultrasonic sensors, it can judge the distance from the ground and automatically avoid obstacles.

The Wit uses a laser altimeter, which is better than the ultrasonic sensors of home drones. But other aspects are not cheap. On Mars, a magnetic compass is useless, and the Martian magnetic field is weak and messy. There is also no GPS fix on Mars. These two navigation methods are useless. Wit's motion positioning can only rely on the vision of the camera to perform optical flow positioning. To put it bluntly, this technology is to install a camera on the stomach and use the ground image as a reference to calculate how much and in which direction it has moved.

The radio signal sent by this drone will be transmitted about 1000 meters after it is dead, so it cannot be too far away from Perseverance. After all, the images taken must first be transmitted to Perseverance, which will then be forwarded to the spacecraft running on Mars orbit. Relay satellites, which are then relayed to Earth, are received by the ground measurement and control station in Spain, so that we can see this image.

Although the drone is weak, and despite its experimental nature, no specific mission is scheduled. That's another $80 million, plus $5 million in operating expenses. But this is Mars after all, and our human aircraft flew away from the earth. So this is still a very memorable achievement. When the Wright Brothers' Aviator flew for the first time, didn't it only fly for 12 seconds, at a distance of 37 meters? By the way, Wit carried a small piece of muslin from the left wing of the Wright Brothers Flyer, wrapped around the wires extending from the solar panels. At least in the eyes of JPL engineers, the first flight of Wit is as important as the first flight of humans. If Wit is doing well, then research into the next-generation helicopter, Dragonfly. But Dragonfly is not flying on Mars, but on Saturn's moon Titan.

Titan has a dense atmosphere with an air pressure 1.45 times that of Earth's surface. And Titan is farther away, receiving only 1% of the sunlight that Earth does. Unfortunately, most of the sunlight is also reflected, so the temperature on Titan is -190 degrees Celsius. Moreover, the rotation of Titan has been locked by the huge Saturn, and one face is always facing Saturn. The rotation speed of the atmosphere far exceeds the rotation speed of the surface, and this environment is much harsher than that of Mars.

The image you are seeing now was taken by the Huygens probe. A few minutes after it landed on the surface of Titan, the Huygens stopped working, and the working time was not long. In such a complex and harsh environment, if Dragonfly can really fly on Titan, it will undoubtedly be another innovation of mankind.

Americans have made many firsts in the exploration of the solar system. We have to admit that, in addition to the Soviet Union's achievements in the exploration of Venus, other relevant knowledge about the major planets in the solar system is mainly contributed by Americans. We are just getting started in deep space exploration, even though our Mars rover Tianwen-1 has a very high starting point. It can be said that it is a step that spans the decades of American history, but after all, we are filling the domestic gap and doing what Americans have done decades ago. Our national strength has become very strong, and our technology has become relatively advanced. In terms of ability and resources, we should do things that have not been done by our predecessors, so that we can better represent the height of all mankind and be more meaningful.

It's numerous fun to fight the destiny. With a lot of money, artificial intelligence and big data in the first hand, in order to get along with the hawkers who buy vegetables, is there any prospect? How boring is fighting in the nest.

I believe that no engineer will be satisfied with repeating what others have done over and over again, right? The Mars rover carried by Tianwen-1 has not been thrown away yet, but it will be soon. Don't worry, I will talk to you later.