Chapter 1101 Overcome the black barrier?
While Chang Haonan was brainstorming, the Shenzhou-5 spacecraft at an orbital altitude of 340 kilometers had also entered the final stage before returning.
Generally speaking, a returnable spacecraft will start lowering its orbit and adjusting its attitude about one-third of a cycle in advance.
In order to ensure that the most critical control instructions are foolproof, this process will not be completed through relay communications, but will be directly handled by overseas measurement and control stations or maritime measurement and control ships——
In fact, The two measurement and control points located near Africa were set up for this orbit adjustment.
Of course, in order to preserve the stable transmission of images in the cabin, the Qingluan constellation is still on standby. It needs to wait until the spacecraft lands safely before it can readjust its attitude and return to the original working mode of serving the sun-synchronous orbit.
At this time, other irrelevant information is no longer displayed on the screen in front of the command and control hall.
Only a track map is left, as well as the spacecraft status obtained during the last measurement and control connection.
Compared to twenty hours ago, this place has become much emptier now.
Some leaders and guests watching the launch mission have left.
The comrades in charge of the recovery mission had already set off to the vicinity of the landing site.
However, the tension in the atmosphere is no less intense than that of the launch.
Spacecraft return technology is inherently a huge technical difficulty.
Some early manned space missions even abandoned the spacecraft directly and ejected the astronauts alone and landed with parachutes.
In addition, the Columbia spacecraft at the beginning of the year and the Soyuz TM10 spacecraft in the middle of the year also had problems during their return.
Therefore, before entering the orbit change procedure, the staff need to make sure again and again that there are no mistakes.
At 5:33 in the morning, the command and control center finally received a new message:
"Yangtze River 3 reported that the target was found!"
Yangtze River 3, also It is the Yuanwang-3 survey ship on standby in the southern Indian Ocean.
Just a few seconds after the words were spoken, half of the area was divided on the large screen to display images of the Shenzhou 5 cabin.
The astronaut was holding the movable instrument panel with both hands at this time, checking the operating information of the spacecraft attentively.
Similar to the orbit change, the return of the spacecraft does not actually require the astronauts to personally control it.
The previous four unmanned spacecrafts were also directly controlled from the ground to complete the entire process.
However, some investigation results show that the landing point of the Alliance spacecraft shifted in May because the control instructions issued by the ground were inconsistent with the information received by the spacecraft.
Therefore, an additional step was added on Shenzhou 5.
"Shenzhou 5 reports that the spacecraft is operating normally!"
Soon, the astronaut's angry voice sounded.
Compared to before the launch, more than 20 hours of space travel did not seem to have much impact on him.
It shows that the entire life support system of the spacecraft should be very consistent with the requirements.
Two minutes after capturing the target, Yuanwang-3 issued the first data command to return to the program.
The spacecraft then began to adjust its attitude.
At 5:36, the return module separated from the orbital module, and lightly completed a 180° turn, aligning the heat-insulating outsole of the tail forward in the direction of flight, and then braked the rocket engine to ignite, completing Deorbiting operation procedures...
Due to the limitation of the measurement and control range, this series of actions must be completed in just a few minutes, otherwise the spacecraft will leave the measurement and control range of Yuanwang-3.
So, even though everything seems to be in order, the movement of lowering the spacecraft's orbit must be rapid enough.
In almost a few breaths, the distance has been reduced from the original 340km to about 250km.
Correspondingly, the picture on the big screen also shook violently, almost similar to the situation during yesterday's rocket launch.
Soon, Shenzhou 5 left the measurement and control range and entered the last measurement and control blind spot before returning.
Fortunately, the images inside the cabin have not been cut off, allowing everyone on the ground to directly observe the basic conditions of the astronauts.
It was not until 5:59, when the propulsion module separated and the return capsule began to enter the inertial flight stage, that the whole scene finally returned to calm.
Shen Junrong, who had hardly taken a breath just now, leaned back on the back of his seat, took off his blue work hat, and straightened his half-grey and half-white hair:
"It seems... the maneuvers during the return process were a bit too violent..."
"The time is so stuck... there is nothing we can do about it."
Don't say that. It was the first time for Shen Junrong to watch this, and even Chang Haonan, who had watched the documentary in his previous life, was really sweating just now. They were just pretending to be calm now:
"Wait until the relay communication technology matures in the future. Now, we should be able to enter the attitude adjustment process earlier..."
There are some problems in manned spaceflight that cannot be simulated no matter how many times the unmanned spacecraft is tested.
Therefore, no matter which country they are in, astronauts who undertake their first mission have extremely special treatment.
The time to relax did not last long.
In the next five minutes, the trajectory of Shenzhou 5 continued across the northern Indian Ocean and over South Asia, and finally entered China, where it was captured by the radars of several measurement and control stations.
And its altitude was basically close to the atmosphere... At 6:04, the trajectory information displayed on the screen and extending forward suddenly disappeared.
It means that the spacecraft has entered the black barrier area——
At an altitude of 35 to 80km above the ground, due to the severe friction between the reentry body and the air, the high temperature will cause the air around the spacecraft to ionize to form plasma. Shield all electromagnetic waves.
Although some optical systems can still make observations, the failure of radar and communication signals is still equivalent to cutting off the connection between the ground and the target, especially the inability to obtain sensor data on the spacecraft.
Therefore, this is also the riskiest section of the entire return process.
Actually, the entire black barrier stage only lasts about 3-4 minutes.
But for everyone present, it can be said that every second seems like a year.
It was not until 6:08 that the command hall finally reacquired target data.
At this time, the return capsule has arrived over the Baiyun Obo area in Mongolia Province.
After passing the black barrier, the gate of hell is actually over.
Although there are risks in the following steps, they are completely different.
Sure enough, good news came one after another.
As soon as the command and control hall confirmed the status of the spacecraft, it received a report from the forward search, rescue and recovery unit:
"I am helicopter No. 743, and the return capsule has been found!"
< br>After the report ended, footage from a helicopter quickly appeared on the big screen.
On the prairie in the early morning light, the semi-oval return capsule of Shenzhou 5 has thrown away its insulated bottom and is slowly descending in mid-air, dragging a huge parachute.
Because the altitude at this time is already too low, most measurement and control methods have failed.
The staff in the command and control hall were relatively idle.
Therefore, when this scene appeared, many people started to applaud.
Even the commander-in-chief sitting on the podium did not interfere.
Having reached this point, a little celebration is not considered opening the champagne in advance.
However, Shen Junrong is not among them.
"Although this is already the fifth time, every time I see the spacecraft passing through the black barrier, my heart still can't stop beating..."
He gently tapped his heart, While talking to Chang Haonan.
When people relax after a long period of tense emotions, they often show a stronger desire to express themselves.
Old experts are no exception to this.
"I suddenly had an idea."
Shen Junrong just found a topic to relieve the pressure, but Chang Haonan's answer was serious:
"If you control the flight angle of the re-entry body at the same time And the aerodynamic shape changes the reentry process from omnidirectional ablation to directional ablation. Then the plasma existence area can be limited to part of the surface. Can normal communication be achieved in the black barrier area? "< br>
“Huh?”
The former was just a casual comment, but now his attention was completely on the slowly falling spaceship.
As a result, I suddenly heard Chang Haonan say "normal communication in the black barrier area."
The whole person was immediately shocked.
But I didn’t hear the first half of it clearly, so I froze in place.
Chang Haonan also saw the other party's embarrassment and immediately repeated what he just said.
This time, Shen Junrong must have heard clearly.
But for a moment I didn't know how to answer.
Communication within a black barrier is actually a subject that has been studied for a long time.
It’s just that I haven’t been able to find a solution with high operability in engineering.
Seeing this, Chang Haonan further explained:
“The so-called black barrier is essentially a non-equilibrium state caused by the chemical balance in the stagnation area and the diffusion of fluid to the conical front end of the aircraft. The ionization process of chemical freezing, chemical reaction surface enhancement, aircraft surface ablation, introduction of additional particles and free electrons, and deposition of net surface charge, free electrons and ions in the gas interact, resulting in the formation of a plasma sheath around the aircraft layer.”
As he spoke, he wrote down a series of formulas in his notebook:
“When electromagnetic waves propagate in plasma, the imaginary part of the wave number determines the absorption of waves by the plasma. Then we lower the sheath somewhere. The electron density can improve the transmittance of electromagnetic waves at this location. For example, changing the blunt structure to a pointed cone structure can very effectively reduce the thickness of the sheath itself, which is equivalent to reducing the electron density... ”
The expression on Shen Junrong’s face changed from shock to curiosity, and then to contemplation.
It was not until ten minutes later that the spacecraft landed smoothly and there was a roaring tsunami of applause from all around that he woke up from his thoughts again...
(End of this chapter)
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