Chapter 1101 Overcoming the Black Barrier?

While Chang Haonan was brainstorming, the Shenzhou V spacecraft at an altitude of 340 kilometers had already entered the final stage before returning.

Generally speaking, a returning spacecraft will start to lower its orbit and adjust 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 communication, but will be directly handled by overseas measurement and control stations or offshore measurement and control ships-

In fact, the two measurement and control points near Africa are set up for this orbit adjustment.

Of course, in order to maintain 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 working mode of serving the sun-synchronous orbit at the beginning.

At this time, the screen in front of the command and control hall no longer displays other irrelevant information.

Only a track map is left, and the spacecraft status obtained during the last measurement and control connection.

Compared with twenty hours ago, this place has become much emptier.

Some leaders and guests who watched the launch mission have left.

And the comrades in charge of the recovery mission have already set off to the vicinity of the landing site.

However, the tension in the atmosphere was no less than that of the launch.

The spacecraft return technology is a huge technical difficulty.

Some early manned space missions would even abandon the spacecraft directly and eject the astronauts alone and land with parachutes.

In addition, the Columbia at the beginning of the year and the Soyuz TM10 spacecraft in the middle of the year also had problems in the return process.

Therefore, before entering the orbit change procedure, the staff needs to confirm again and again that there is no error.

At 5:33 in the morning, the command and control center finally received a new message:

"Changjiang No. 3 report, target found!"

Changjiang No. 3 is the Yuanwang No. 3 survey ship on standby in the South Indian Ocean.

Just a few seconds after the voice fell, half of the area was divided on the big screen to show the cabin image of Shenzhou No. 5.

The astronauts were holding the movable dashboard with both hands, and their expressions were concentrating on checking the operation information of the spacecraft at this time.

Like the orbit change, the return of the spacecraft does not actually require the astronauts to operate it personally.

The previous four unmanned spacecraft were also directly controlled by the ground to complete the entire process.

However, some investigation results show that the landing point of the Soyuz spacecraft in May was offset because the control instructions issued by the ground did not match the information received by the spacecraft.

Therefore, a step was added on Shenzhou V.

"Shenzhou V report, the spacecraft is operating normally!"

Soon, the astronaut's full voice sounded.

Compared with before the launch, the more than 20 hours of space travel did not seem to have much impact on him.

This shows that the entire life support system of the spacecraft should be very in line with the requirements.

Two minutes after capturing the target, Yuanwang-3 issued the first data instruction of the return program.

The spacecraft then began to adjust its attitude.

At 5:36, the return capsule separated from the orbital capsule and lightly completed a 180° turn, so that the heat-insulating bottom of the tail was facing forward in the direction of flight, and then the brake rocket engine was ignited to complete the deorbit operation procedure...

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.

Therefore, although everything seems to be in order, the action of lowering the spacecraft's orbit must be fast enough.

In just a few breaths, the speed had dropped from 340km to about 250km.

Correspondingly, the image on the big screen also began to shake violently, almost the same as the situation during the rocket launch yesterday.

Soon, Shenzhou V left the measurement and control range and entered the last measurement and control blind area before returning.

Fortunately, the images in the cabin were still not cut off, allowing people on the ground to directly observe the basic situation of the astronauts.

It was not until 5:59 that the propulsion module separated and the return module began to enter the inertial flight phase, and the entire picture finally returned to calm.

Shen Junrong, who had barely even breathed in air, leaned back on the back of his seat, took off his blue work cap, and casually combed his half-gray and half-white hair:

"It seems... the maneuvers during the return process were still a little too intense..."

"The time is too tight... there's nothing we can do about it."

Not to mention Shen Junrong, who was watching this for the first time, even Chang Haonan, who had watched the documentary in his previous life, was really nervous just now, and he was just pretending to be calm at this moment:

"When the relay communication technology matures in the future, it should be possible to enter the attitude adjustment process earlier..."

Some problems in manned space flight cannot be simulated no matter how many times the unmanned spacecraft is tested.

So no matter which country, astronauts who undertake the mission for the first time have extremely special treatment.

The time to relax did not last too long.

In the next five minutes, the trajectory of Shenzhou V crossed the North Indian Ocean and South Asia, and finally entered the territory of China, and was captured by the radars of several tracking and control stations.

And its altitude is basically close to the atmosphere...

At 6:04, the trajectory information displayed on the screen and extending forward suddenly disappeared.

This means that the spacecraft has entered the black barrier area——

At an altitude of 35 to 80 km from the ground, due to the intense friction between the reentry body and the air, the high temperature will cause the air around the spacecraft to ionize and form plasma, shielding all electromagnetic waves.

Although some optical systems can still be observed, the radar and communication signals are all ineffective, which 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 most risky part of the entire return process.

In fact, the entire black barrier stage is only about 3-4 minutes.

But for everyone on the scene, it can be said that every second is like a year.

Until 6:08, the command hall finally regained the target data.

At this time, the return capsule had arrived over the Baiyunebo 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.

As expected, good news came one after another.

The command and control hall had just confirmed the status of the spacecraft when it received a report from the search and rescue recovery unit in front:

"I am helicopter No. 743, and the return capsule has been found!"

After the report, the picture taken by the helicopter quickly appeared on the big screen.

On the grassland where the morning light was just beginning to appear, the semi-oval return capsule of Shenzhou V had already thrown away the insulation bottom and was slowly descending in the air with a huge parachute.

Because the altitude was too low at this time, most of the measurement and control methods had failed.

The staff in the command and control hall were relatively idle.

Therefore, when this scene appeared, many people began to applaud.

Even the commander-in-chief sitting on the command platform did not interfere.

It has come to this point, and a little celebration is not considered to be opening champagne in advance.

However, Shen Junrong was not among them.

"Although it is the fifth time, every time I see the spacecraft passing the black barrier, my heart still can't stop beating..."

He said to Chang Haonan while gently pounding his chest.

When people relax suddenly 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 have an idea."

Shen Junrong just picked a topic to relieve his stress, but Chang Haonan's answer was serious:

"If the flight angle and aerodynamic shape of the reentry body are controlled at the same time, so that the reentry process changes 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?"

"Ah?"

The former was just talking casually, and his attention was completely on the slowly falling spacecraft.

As a result, he suddenly heard Chang Haonan say "normal communication in the black barrier area".

The whole person was shocked immediately.

But he didn't hear the first half of the content clearly, so he was stunned.

Chang Haonan also saw the other party's embarrassment and immediately repeated what he had just said.

This time, Shen Junrong must have heard it clearly.

But for a while, he didn't know how to answer.

Communication in the black barrier is actually a topic that has been studied for a long time.

It's just that a solution with high operability in engineering has not been found.

Seeing this, Chang Haonan further explained:

"The so-called black barrier is essentially due to the chemical equilibrium in the stagnation area, the non-equilibrium ionization process caused by the diffusion of fluid to the conical front end of the aircraft, chemical freezing, chemical reaction surface enhancement, aircraft surface ablation, the introduction of additional particles and free electrons, and the deposition of surface net charge, free electrons in the gas and ions interact, resulting in the formation of a plasma sheath around the aircraft."

He wrote a series of formulas in the notebook:

"When electromagnetic waves propagate in plasma, the imaginary part of the wave number determines the absorption of waves by plasma. If we reduce the electron density at a certain point in this sheath, we can improve the transmittance of electromagnetic waves at this position. For example, changing the blunt head structure to a pointed cone structure can 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 astonishment to curiosity, and then to contemplation.

It was not until more than ten minutes later, when the spacecraft landed smoothly and there was applause like a tsunami around him, that he woke up from his thoughts again...