At this time, there is a huge cigar-shaped UFO suspended in the sky. Its appearance is similar to the color of space, gray and black.
Because its length has reached 5 kilometers, its appearance in the sky gave a huge shock to those watching it on the ground. However, what Zhang Desen did not expect was that he was not completely silent, but was accompanied by a low humming sound, which surprised Zhang Desen.
Because in his impression, such alien spaceships are usually silent. Now a huge cigar-shaped spaceship with a low humming sound suddenly appeared, which made him feel very fresh and strange. Special, so in order to connect with the alien spacecraft in his impression, he had to imagine this spacecraft as a special sound spacecraft.
At the same time, this is a huge cigar-shaped spaceship. It is emitting huge light to the four weeks. But even so, there are bright lights everywhere around it. But among them it has 10 huge bright lights which are the greatest. And these bright lights are arranged very neatly.
At this time, Zhang Desen said to his friends around him:
"I didn't expect that this huge cigar-shaped space carrier is a sounding spacecraft, although it is a little lower. If I had been in space before, if there was no air in space and no sound could be transmitted, I wouldn't know it now. This huge cigar-shaped space carrier actually has a low humming sound."
When Li Longfang heard what Zhang Desen said, he immediately said:
"Perhaps the captain's impression of aliens has always been that their technology is very advanced, so he forgot that not every alien technology is equally advanced, and occasionally some have corresponding flaws. But to be honest, , we are actually quite shocked that they can create such a huge cigar-shaped spacecraft.”
Zhang Desen said:
"You're right. I just don't know what it will do next?"
However, just as Zhang Desen finished speaking, the huge cigar-shaped UFO suddenly fired a bright beam of light toward a densely forested place in the north of Hezhou City. The beam appears dark red and is round in shape. And when this beam of light hit the dense forest in the deep forest, all the trees there instantly withered and fell down.
And it's not just the trees, as long as it's the birds and insects where the light beam passes. After being illuminated by this beam of light, they all fell to the ground one after another.
At this time, Zhao Chengming asked Zhang Desen:
"Captain, what are they doing? Then why do you think it is so powerful that it makes all the forests wither? And even the birds and insects flying in the sky cannot escape the damage of that beam. It's so powerful. "
After Zhang Desen thought for a moment, he replied:
"No matter what kind of beam this beam is, I guess it must be very hot."
Zhao Chengming heard what Zhang Desen said, looked at it and thought about it again, and then said:
"I'm afraid that's the case. Captain, look at the fallen birds and insects. They all have burnt marks, and many of them have been burnt to death. Although we are far away from there now, But according to the results of remote observation, those fallen trees indeed seemed to have been burned to death."
Zhang Desen said with a serious expression at this time:
"To be honest, I'm not worried about the scorching point of that beam. Because if that beam is just ordinary scorching, it won't leave any sequelae. It's just that you will be very unlucky after being hit by it. But what if? That beam has associated radiation, so that's terrible. The consequences of radiation are horrific."
After Zhao Chengming heard this, he immediately asked Zhang Desen:
"Then captain, should we cordon off that area?"
After Zhang Desen thought for a while, he said to Zhao Chengming:
"After our plan starts later, you stay here and communicate with General Feng Yucai. Tell him our guess just now and explain to him the hazards of radiation. Let him make corresponding arrangements to avoid possible radiation hazards. So many innocent people.”
After hearing this, Zhao Chengming immediately said:
"Captain, don't worry. You and Li Longfang will go to the squad leader to implement the plan later."
When the time comes, I will immediately communicate with Feng
General Yucai communicated. Please leave everything to me, don't worry. "
After hearing this, Zhang Desen said:
"Okay, you can, but please don't contact us too intensively for a while. I may have to fly at supersonic speed, and it won't be just for a moment. So in order to ensure the smooth operation, I rarely reply. I hope you can understand. ."
But at this moment, a female voice suddenly came. Just listen to her say:
"What is supersonic flight? Can you tell me about it?"
When everyone took a look, it was Feng Ling'er who walked in. A soldier from the United Family General Team next to him expressed his helplessness because he could not fire and injured Miss Feng Ling'er, so he could not stop Miss Feng Ling'er from breaking in. Zhang Desen waved his hand and asked the soldier to return to his original post. After that, he said to Feng Linger:
"Miss Feng, why did you break in again?"
Feng Linger pouted and replied:
"You actually treat me as an outsider, okay, let me tell you. My dad said that the mysterious monster kept emitting terrible lights and could hurt me at any time. In order to ensure my safety, I thought I came to you. It's safer, but now you are treating people like this..."
After hearing this, Zhang Desen thought about the same truth and was worried that she would burst into tears, so he immediately comforted her repeatedly. And when he looked at Zhang Desen, he was not angry with her, so he asked excitedly:
"Mr. Zhang, you haven't answered me yet, what is supersonic flight?"
After hearing this, Zhang Desen felt that if he didn't tell her, she might keep pestering him. After all, there were still many things that she didn't know or didn't quite understand. Zhang Desen looked at the time and felt that the time was okay. Who asked Li Longfang to prepare the rest and set off at any time. Then I briefly talked to Miss Feng Ling'er about what supersonic flight is.
Supersonic flight, also known as "supersonic flight". It refers to the flight of an aircraft at a speed above Mach 1.2. Its main feature is that wave resistance becomes the main part of the resistance.
The aerodynamic center moves backward and the flight damping decreases. This requires the aircraft's wings to be swept back and reduce their area. The aircraft body must be made into a pointed and elongated shape to increase the area of the control surface (especially the vertical tail). As the control performance deteriorates, the anti-interference and recovery capabilities become worse, so the pilot's movements are required to be coordinated and gentle when flying at supersonic speeds.
Supersonic flight will cause sonic booms and produce powerful noise, and supersonic flights are generally prohibited over residential areas. After the advent of the jet engine, mankind finally realized its dream of flying at supersonic speeds in 1947. It took more than 40 years.
When the flight speed is very high (Mach number exceeds 2.5), due to the friction of gas molecules, aerodynamic heating is caused, which increases the surface temperature of the aircraft body. The current common aluminum alloy materials cannot withstand it. Aviation tools with a Mach number exceeding 2.5 must use titanium alloy. or other heat-resistant alloy structural materials.
Supersonic aircraft use supersonic combustion ramjet engines, which are classified as ramjet engines. The principle of the ramjet engine was proposed by Frenchman René Rolland in 1913 and was first used by Germany on the V-1 missile in 1939. The ramjet engine consists of three parts: the inlet, the combustion chamber, and the propulsion nozzle. It is much simpler than the turbojet engine.
Ramping is a process that uses head-on airflow to slow down and increase static pressure after entering the engine. This process does not require a high-speed rotating, complex compressor. The high-speed airflow decelerates after expansion, and after the air pressure and temperature increase, it enters the combustion chamber to mix and burn with fuel. The temperature is 2000-2200, or even higher. After expansion and acceleration, it is discharged from the nozzle at high speed, generating thrust.
Ramjet engines are currently divided into three categories: subsonic, supersonic, and supersonic combustion (or hypersonic). The subsonic ramjet engine uses aviation kerosene as fuel, adopts a divergent inlet and a convergent nozzle, and the boost ratio during flight does not exceed 1.89. Generally it cannot work at speeds less than Mach 0.5.
The scramjet engine uses a supersonic inlet, the combustion chamber inlet is subsonic airflow, and a convergent or convergent divergent nozzle is used.
Use aviation kerosene or hydrocarbons as fuel. The propulsion speed is Mach 2 to Mach 5 and can be used for supersonic target drones and surface-to-air missiles. The supersonic combustion (hypersonic) engine is a novel engine that uses hydrocarbon fuel or liquid hydrogen fuel. The flow rate of air in the engine is always maintained at supersonic speed.
Speeds as high as Mach 5 to Mach 16.
There are differences between supersonic combustion engines and turbofan jet engines
. In fact, it is also different from a rocket engine. Although the speed of a multi-stage rocket is extremely high, reaching more than Mach 20, it carries all the fuel, so its payload is lower than that of an aircraft equipped with a supersonic combustion ramjet engine at the same volume.
The characteristics of supersonic flight are:
1. The aerodynamic center moves backward and the longitudinal static stability increases;
2. Aircraft damping decreases as Mach number increases.
Both lead to slow attenuation of aircraft disturbances and deterioration of maneuverability (see disturbance motion modes), especially in high altitudes. Therefore, driving movements should be gentle and the pole and rudder should be coordinated. Since the efficiency of the horizontal tail and vertical tail is reduced, the hinge moment increases sharply, and the change pattern is complex, a full-moving horizontal tail and an irreversible booster are required.
The reduction in tail efficiency causes the aircraft's directional stability and lateral stability (see aircraft dynamic characteristics) to decrease as the Mach number increases.
Especially when flying at high altitudes, the directional stability is even worse, so it is necessary to increase the vertical tail area or use automated devices or limit the flight Mach number. Because the air at high altitude is thin and the atmospheric temperature is low, the flight speed range is small, the acceleration is slow and the climb rate is reduced. When the altitude changes drastically, the altimeter and speedometer indications will produce large delay errors, and the difference between the true speed and the speed indication values will increase.
Also, a sound barrier will occur during supersonic flight. The so-called sound barrier is a straight-wing aircraft with a large aspect ratio. When the flying speed is close to the speed of sound, the drag will increase sharply, the control performance will deteriorate, and the flight speed will not increase. Therefore, people once thought that The speed of sound is an insurmountable obstacle for aircraft speed, hence the name, and it is also called the positional sound barrier.
In practice, people have found that when the flight speed reaches nine-tenths of the speed of sound, that is, the Mach number M0.9, which is about 950 kilometers per hour in the air, the speed of the local airflow may reach the speed of sound, generating local shock waves, thereby drastically increasing the aerodynamic resistance. . To further increase the speed, more thrust from the engine is required.
What's more serious is that shock waves can make the airflow flowing through the surface of the wings and fuselage very turbulent, causing the aircraft to shake violently and making it difficult to control. At the same time, the wings will sink and the nose of the aircraft will drop; if the aircraft is climbing at this time, the fuselage will suddenly tilt up automatically.
These nasty symptoms can cause a plane to crash. This is the so-called "sound barrier" problem. Since the transmission speed of sound waves is limited, a moving sound source can catch up with the sound waves it emits. When the speed of an object increases to the same speed as the speed of sound, sound waves begin to pile up in front of the object.
If this object has enough acceleration, it can break through this unstable sound wave barrier and rush to the front of the sound, that is, break through the sound barrier.
An object traveling at supersonic speeds will continue to generate stable pressure waves (bow shock waves) in front of it. When the object moves toward the observer, the observer does not hear the sound; after the object passes, the waves generated (Mach waves) are transmitted toward the ground, and the pressure difference between the waves creates an audible effect, which is a sonic boom.
When the aircraft's flying speed is lower than the speed of sound, the air in contact with the aircraft acts like a "communicator", "notifying" the air ahead that is about to encounter the aircraft forward at the speed of transmitting sound, causing them to "give way."
But when the speed of the plane exceeds the speed of sound, the air in front of the plane is compressed tightly because there is no time to escape, and it accumulates into a thin wave surface - a shock wave. Behind the shock wave, the air is compressed, causing the pressure to suddenly rise. High, preventing the aircraft from further accelerating, and may cause the wings and tail to vibrate violently and cause an explosion.
After Zhang Desen finished telling Feng Ling'er the relevant information, he couldn't help but feel relieved. He felt that Miss Feng Linger would stop making trouble this time.
But everything turned out as he wished. Miss Feng Ling'er suddenly became very quiet, and actually savored everything he said. Zhang Desen couldn't help but say thank you. Of course, thank God, he said this in his heart. If he really said it, it would probably be another inexplicable commotion.
However, what Zhang Desen focused on at this time was of course what was happening outside. He looked at the time again and felt that it was time to set off, but the huge cigar-shaped space carrier did not emit a second beam. , then it’s time to lure it away as soon as possible
.
Soon, Li Longfang also came back and reported to Zhang Desen that everything was ready. Zhang Desen immediately walked to the launch pad with him, preparing to drive his spacecraft to attack this huge cigar-shaped UFO.
