Bright Sword starts with the grenade flat.

Chapter 396 Laser weapons have no recoil!

After Liu Xiu finished speaking, he took out the plan regarding the star destroyer cannon and showed it to the senior officials of Wandering Blue Star.

Of course, this plan to build a star destroyer cannon will require a huge amount of resources.

Fortunately, although the resources required to build a star destroyer are enormous, with the advancement of technology, especially anti-gravity technology and the construction of miniaturized nuclear fusion reactors, interstellar meteorite mining has become a very natural technology.

Although the stars in the Proxima Centauri system are not very massive, there are still many asteroids, so it naturally does not delay Liu Xiu's mining operations.

In fact, the reason why Liu Xiu chose to use laser weapons instead of electromagnetic kinetic weapons, in addition to the slow speed of electromagnetic kinetic weapons projectiles, is another more critical reason. That is the powerful recoil of electromagnetic kinetic weapons, which will make the crust of the Wandering Blue Planet unable to bear it and may even cause a global earthquake, thereby destroying the underground city and causing casualties. It is even very likely that the crust of the Wandering Blue Planet will directly rupture.

Because any projectile or kinetic weapon has recoil. For example, the most common gunpowder rifle has a large recoil and must be equipped with a special stock. And barreled artillery with greater recoil even requires a special muzzle brake and recoil return system.

The physical principle of recoil is also very simple, which is the principle of conservation of momentum in Newtonian mechanics. If a projectile flies in one direction, then the projectile itself must have an opposite vector, and the total momentum is balanced.

Precisely because of the existence of this principle, not only do gunpowder-fired barreled weapons have strong recoil, but even conceptual-level weapons like electromagnetic guns also have recoil. Of course, for the current Wandering Blue Star, electromagnetic guns are already a very common weapon.

However, electromagnetic guns are not like ordinary gunpowder weapons that complete the acceleration process in a very short moment. Therefore, although the initial velocity of the electromagnetic gun projectile is higher than that of most gunpowder fired projectiles, the acceleration process of the electromagnetic gun projectile is relatively longer and takes more time. Therefore, the recoil of the electromagnetic gun will be more balanced.

So here comes a new question, do laser weapons have recoil? If not, how do we explain the light pressure phenomenon?
However, in common sense, luminous objects seem to have no recoil. If they did, wouldn't we be able to feel the recoil when we turn on the flashlight?
In fact, it is impossible to feel the existence of such a force. If there is such a recoil force, wouldn't it be possible to install a spotlight on the back of a bicycle and use it as an electric bike?

The reality is that not only weak light sources like flashlights have no recoil, but even strong light sources like searchlights have no recoil. So is it because the recoil is too small and can only be measured by instruments, and it is difficult for humans to feel it! And if ordinary light doesn't work, then can a highly directional laser work?
However, many experiments have shown that even with powerful lasers, you still cannot feel the recoil.

However, Einstein said that photons have no rest mass; but as long as there is energy, there will be kinetic mass, and if there is kinetic mass, there will be impulse, and if there is impulse, there will be recoil.

Of course, the most important thing is the "light pressure" phenomenon that can be directly demonstrated in the experiment. That is, a strong laser beam is directly hit on a very light and thin metal foil. Then these foils will directly move. This shows that laser can indeed produce movement, so it is called "light pressure".

Some people have designed extremely thin and large solar sails, hoping to use the light pressure of the sun and other stars to achieve unpowered deep space flight.

However, some people point out that even if the solar wind has thrust, it is very weak. Even if such a sail is made to cover an area of ​​one square kilometer, the effective light pressure near the blue star is only equivalent to a few grams. Therefore, it is pure fantasy to fly in deep space with this little force. In addition, the pressure of the solar wind is not necessarily pure light pressure, but more likely to be produced by high-speed proton nuclei in the solar wind, and proton nuclei are not components of sunlight. The phenomenon that a strong laser can push a metal foil in a laboratory is not necessarily that the photons directly transfer power to the metal foil.

It is more likely that the strong laser ionized the material on the surface of the metal foil and produced a plasma jet, which gave the metal foil a reaction force and caused it to start moving. No matter how directional the laser is, it still belongs to the category of light. Visible light is just a band of electromagnetic waves.

All electromagnetic waves are Lorentz tensors, not directional vectors. Moreover, when electromagnetic waves are radiated, they will be subject to certain radiation damping. Therefore, it is still unclear whether strong lasers have recoil.

However, experiments are the only criterion for testing the truth. So in order to determine whether laser weapons really have no recoil, Liu Xiu asked people in the laboratory to use billion-watt laser weapons for testing. However, the test results showed that even laser weapons of such power still did not produce half a milligram of recoil.

Although the power of laser weapons that are less than 100 million watts may sound great, in reality they are not that great. After all, one watt-second is only equal to one joule!

One gram of TNT explodes with 4,200 joules of energy, so 100 million watts is equivalent to the explosion of 238 kilograms of TNT. It is not as powerful as the aerial bombs during World War II. After all, the aerial bombs during World War II were loaded with more than 238 kilograms of TNT!
Therefore, a laser of this power is naturally not what Liu Xiu needs. In Liu Xiu's opinion, let alone a billion-watt laser, even a megawatt-level laser cannot reach the power threshold of a star-destroying laser cannon weapon.

After all, one megawatt of power is only one trillion, which is equivalent to the explosion of 2.38 million kilograms of TNT. This power is not even a fraction of Big Ivan. How is it possible to destroy a planet with a diameter of tens of thousands of kilometers with one shot!
Therefore, although the megawatt-level laser power looks very large, in fact, in order to reach the entry threshold of the star destroyer cannon, the power of the laser cannon must be at least 100 million watts, and one 100 million watt is equivalent to a power of 100 billion watts.

The power of an explosion of approximately 23.8 million tons of TNT is approximately equal to half of a Big Ivan, but with such a power, at most it can only destroy an asteroid, such as a comet.

As for wanting to destroy a planet like the Blue Star with a diameter of 10,000 kilometers with one shot, the power of its laser cannon must be increased by at least one or two orders of magnitude, that is, it needs to reach the number of one GaiWa or one ZiWa.

Of course, if you want to build a super-large laser cannon of such power, there will be considerable design challenges first. For example, what kind of design can achieve such power and ensure that it will not be burned during firing.

You should know that the temperature of laser is very high, it can reach hundreds of millions of degrees or even higher, because some scientists have used lasers to reach the temperature of controlled nuclear fusion.

Therefore, although the current technology of Wandering Blue Planet seems very advanced, with quantum computers, heavy nuclear fusion, space fighters, and mechas.

However, when it comes to the research and development progress of laser weapons, the laser research level is really not as high as that in the world before Liu Xiu traveled through time.

(End of this chapter)