laitimes

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

author:Institute of Physics, Chinese Academy of Sciences

In this year's college entrance examination, in the Jinan middle school examination center, a new type of anti-cheating black technology was born:

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

It was given a shiny name: Magnetic Shotgun!

According to reports, the magnetic gun can snipe black flying drones to ensure the fairness of the college entrance examination.

01 Fantastic Shotgun

The editor found that netizens are very curious about how this magnetic gun is used:

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

The editor is also curious!

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

Looking up on the Internet, Xiaobian found that many netizens believe that the magnetic bullet gun used here uses electromagnetic fields to launch magnetic bombs to hit drones.

At first glance, it seems to fit the name of the magnetic gun, but when you think about it, it feels... Something is wrong?

First of all, the above description is actually closer to the electromagnetic gun, a weapon that uses electromagnetic force to obtain extremely high kinetic energy from the projectile, its working principle is not difficult to understand, and it is related to electromagnetic interaction - this is what I learned in high school physics, isn't it very simple!

Electromagnetic guns can be divided into magnetic cannons, coil guns and heavy guns according to different structures, and we will use the more common magnetic guns to give an example:

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

Simple schematic diagram of a magnetic cannon | Source: Wikipedia

As shown in the figure, two parallel metals form a guide, the conductive projectile is inserted horizontally between the guides, after the power is applied, the current returns to the negative electrode from the positive electrode through the projectile, according to the right-handed spiral law, the magnetic field shown in the figure will be formed from the bottom up, the projectile is accelerated by the Lorentz force in the magnetic field, moves towards the shell port at a very fast speed, and finally shoots at high speed.

This analysis step, isn't it very familiar!

Isn't this the high school physics problem in the electromagnetic field section!

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?
How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

"Dead High School Physical Memories Suddenly Attack Me"

02 A magnetic cannon that should not be underestimated

At present, typical magnetic cannons are generally used in the military field, and the design goal is to allow the energy of 5-50 megajoules (MJ) of the shell fired. We can simply calculate it using the following kinetic energy formula:

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

Suppose we drive an ordinary family car weighing 1.5 tons, and to reach a kinetic energy of 50MJ at some point, we need an instantaneous speed of 929.6 km/h (258.2 m/s).

Oh, I don't think any ordinary car has reached this instantaneous speed... The editor can only think of the following supergods:

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

According to the above calculations, it is not difficult to find that in fact, if you really want to obtain such a high projectile exit speed, you need a strong current to accelerate the projectile, we can estimate:

For simplicity, if we ignore the electric field, the Lorentz force on the charged particle in the magnetic field is:

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

In the macroscopic state, the amperage force of the projectile is:

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

where l is the spacing between parallel guides. According to the Bio-Safar law, for constant current, the magnitude of the excited magnetic field is:

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

For current-carrying straight conductors, the integration is calculated according to the following schematic diagram:

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

Simple schematic

The magnitude of the magnetic field at m can be obtained:

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

For a semi-infinitely long parallel straight conductor, you can take:

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

For small magnetic cannons, we simply assume that the width of the guide rail is not large, and the magnetic field can be regarded as the superposition of two semi-infinite parallel straight wires with opposite currents, then simply look at the uniform strength magnetic field to obtain:

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

where l is the spacing between the two orbits, μ is the vacuum permeability, whose value is μ=4π×10 Newtons/ampere.

Simplicity yields:

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

That is to say, a current of 1000 amperes can only produce a force of 0.1N, if you want to accelerate the projectile to the order of kilometers per second, the current may reach the order of millions of amperes, and the power generation power is as high as tens of megawatts or even hundreds of megawatts, which is almost the power generation power of a medium-capacity thermal power plant!

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

It is conceivable that the strong current required for the operation of the electromagnetic gun will bring great load to the launcher, which also brings great challenges to the materials used to make orbital and projectile bodies, and the relevant materials are still in the stage of further development.

That is, even in the military field, the technology of electromagnetic guns is not yet mature, assuming that the magnetic gun outside the college entrance examination room is really something similar to electromagnetic guns ...

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

If it is really used to shoot down UAVs, it may theoretically be closer to the CS/LW21 handheld electromagnetic explosion-proof launcher exhibited at last year's Zhuhai Air Show, which is an electromagnetic gun developed by China Ordnance Equipment Group, the principle is similar to the coil gun in the electromagnetic gun, but the following 9mm diameter flat round shrapnel is used:

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

This electromagnetic gun uses flat round shrapnel

This electromagnetic gun has a rate of fire of 100 rounds per minute, an effective range of 50 meters, and can smash beer bottles to pieces:

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

This electromagnetic gun is tested for its effect

It can be seen that the power is still not small. Of course, the current CS/LW21 is only a conceptual weapon, if it can further improve the performance of range and aim, it is very likely to be used in anti-terrorism and riot control missions in the future.

Speaking of which, do you notice something is wrong?

Whether it is an electromagnetic gun or an electromagnetic gun, the positioning is still in the research and development stage of military weapons, and the "magnetic gun" born in the sky, its task is to prevent someone from cheating through the drone, assuming that it is really shooting a bullet to shoot down the drone, it will actually bring great hidden dangers:

  • The drone is constantly flying dynamically, if the bullet is missed, it is likely to accidentally injure the staff around the examination room or pedestrians passing by, considering that the kinetic energy of the bullet is not small, it is still very dangerous to hit people...
  • If the drone is really shot down, the drone may also hit and injure passers-by during the fall...
  • It is inevitable that there will be a collision sound during the crash of the drone, which will also affect the candidates in the examination room...

Therefore, no matter how you look at it, the use of electromagnetic guns similar to CS/LW21 to prevent college entrance examination drones from cheating is not very reasonable, nor is it in line with our original intention of maintaining the order of the college entrance examination.

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

03 College entrance examination black technology

In that case, the question arises, what is this "magnetic gun"?

After reviewing the information, the editor found another greater possibility:

The so-called magnetic bullet gun is not really a bullet fired, but a wireless signal jammer.

Let's briefly understand the wireless communication system of the UAV: first, the transmitter transmits the data through a series of coding and modulation, and then transmits radiation to the channel in the form of electromagnetic waves, and finally, the receiver receives the corresponding electromagnetic signal sent by the transmitter.

It is not difficult to see that if there is human intervention in the outgoing signal in an open channel, there is an opportunity to achieve counter-UAVs.

If we use a signal jammer to emit a high-power interference signal far beyond the normal communication signal power, and completely drown the original signal in various high-power noises, the receiver can almost or completely unable to parse the correct signal from it, thereby losing the ability to communicate.

It's like you need to find dozens of soybeans doped in such an ocean ball, which is basically impossible...

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

Can you find out the soybeans inside?

At present, the working frequency band of civil UAVs with higher sales on the market is mainly divided into 2.4GHz and 5GHz two frequency bands, the bandwidth ranges from tens of megahertz to hundreds of megahertz, if the wireless network card is configured inside the magnetic gun and switched to the monitoring mode, all wireless signals in the coverage range can be intercepted, and then based on the artificial neural network to identify the intercepted signal, decide the interference signal that needs to be used, and transmit this information to the interference system inside the gun body.

Therefore, when the guard finds that there is a drone around the examination room, he can first aim the magnetic gun at the drone to intercept and identify the signal, and then pull the trigger, activate the circuit board inside the gun body for generating electromagnetic waves, emit the corresponding high-power signal, carry out electromagnetic suppression interference on the drone, force the drone to disconnect from the controller, compared to the physical attack of the real bullet, such a signal interference method, can force the drone to automatically return home or land on the spot in a low-noise situation. This ensures that the candidates in the examination room are not affected.

So, don't be misled by the name "Magnetic Gun"! Essentially, it can be any shape, and I can even design it to look like a high heel—as long as the required circuit board and a series of devices are installed inside the shoe.

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

It's okay to aim and shoot with high heels

In addition to magnetic guns, in recent years, various black technologies have been used in the college entrance examination, such as:

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

Gaokao patrol robot

The college entrance examination patrol robot in the picture comprehensively applies biometrics and big data analysis, we only need to upload the surveillance video of various exam cheating in the past to its processing end, it can automatically decode and analyze, once similar suspected cheating is detected in the examination room, it will automatically trigger an alarm. Don't say, this robot really looks good!

At the intersections of some important test sites of the college entrance examination, the "Sound Hunting" system, that is, the sonar positioning system, is also installed to locate those cars and motorcycles that honk their horns or drag racing near the examination room through acoustic tracking, and accurately locate them in the first time, so as to deal with them in time to ensure that the examinees are not affected.

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

Traffic police track and process vehicles through the "Hunting Sound" system

Of course, no matter what kind of black technology, the ultimate purpose is to escort thousands of students.

Here, we also sincerely wish all students:

Ten years of cold window, looking forward to a bright future, a hundred days of hard fighting, must be the title of the gold list!

How does the anti-cheating artifact "magnetic bullet gun" born in the college entrance examination "shoot"?

Bibliography:

[1] Miao Yanqing, Jin Lei, Tan Weirong, et al. Aviation Standardization and Quality,2014,(6):29-32.)

[2] WU Xiaosong, FANG Zhijun, CHEN Tonghai. Research on countermeasure technology of civil UAV[J]. China Radio, 2018(3): 55-58.

[3] Greff K, Srivastava R K, Koutník J, et al. LSTM: A Search Space Odyssey[J]. IEEE Transactions on Neural Networks and Learning Systems, 2017, 28(10): 2222-2232.

Editor: Mueller's Nanny