The military-industrial scientific research system of the academic master.

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

Generally speaking, a returning spacecraft will begin 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 tracking and control points located near Africa were set up for this orbit adjustment.

Of course, in order to maintain the stable transmission of images inside 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 initial working mode of serving the sun-synchronous orbit.

At this time, no other irrelevant information was displayed on the screen in front of the command and control hall.

All that remains is a track map and the spacecraft status obtained during the last measurement and control connection.

Compared to twenty hours ago, this place is now much more spacious.

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

The comrades in charge of the recovery mission had already set off for the vicinity of the landing site.

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

Spacecraft return technology is inherently a huge technical difficulty.

Some early manned space missions would even abandon the spacecraft directly and eject the astronauts individually and land them using parachutes.

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

Therefore, before entering the orbit change procedure, the staff needs to make sure again and again that there are no mistakes.

At 5:33 a.m., the command and control center finally received a new message:

"Changjiang No. 3 report, target found!"

Changjiang No. 3, also known as the Yuanwang No. 3 survey ship, is on standby in the South Indian Ocean.

Just a few seconds after the words were spoken, half of the area on the big screen was divided to show the images inside the Shenzhou V cabin.

The astronaut was holding the movable dashboard tightly with both hands, checking the spacecraft's current operating information with a focused expression.

Just like changing orbit, the return of the spacecraft does not actually require the astronauts to operate it personally.

The previous four unmanned spacecraft also completed the entire process directly under ground control.

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

Therefore, an additional step was added on the Shenzhou V.

"Shenzhou V reports that the spacecraft is operating normally!"

Soon, the astronaut's powerful voice was heard.

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

This means that the entire life support system of the spacecraft should be very suitable for the requirements.

Two minutes after capturing the target, Yuanwang-3 issued the first data command for the return procedure.

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 pointed forward in the direction of flight, and then the braking rocket engine was ignited to complete the deorbiting operation procedure...

Due to the limitation of the tracking and control range, this series of actions must be completed within just a few minutes, otherwise the spacecraft will leave the tracking and control range of Yuanwang-3.

Therefore, even though everything appears to be in order, the spacecraft's orbit lowering action must be rapid enough.

In just a few breaths, the speed was reduced from the original 340km to around 250km.

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

Soon, Shenzhou V left the tracking and control range and entered the last tracking and control blind spot before returning.

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

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

Shen Junrong, who had barely even breathed a breath, leaned back in his chair, took off his blue work cap, and casually smoothed his half-gray, half-white hair:

"It seems... the maneuvers during the return journey were a bit 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 now he was just pretending to be calm:

"Once the relay communication technology matures, we should be able to enter the posture adjustment process earlier..."

There are some problems in manned space flight that cannot be simulated no matter how many times unmanned spacecraft are tested.

Therefore, no matter which country they are from, astronauts who undertake a mission for the first time receive extremely special treatment.

The time of relaxation did not last 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 radars of several tracking and control stations.

And its height 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 re-entry 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 observe, the radar and communication signals are all ineffective, which is 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 part of the entire return process.

In fact, the entire blackout phase only lasts about 3-4 minutes.

But for everyone at the scene, every second felt like an age.

It was not until 6:08 that the command center finally regained the target data.

At this time, the return capsule had arrived over the Bayan Obo area in Inner Mongolia Province.

Once you pass the black barrier, you have actually passed the gates of hell.

Although there are still risks in the following steps, they are completely different.

Sure enough, good news came one after another.

The command and control center had just confirmed the status of the spacecraft when they received a report from the search and rescue recovery unit ahead:

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

After the report, images taken from a helicopter quickly appeared on the big screen.

On the prairie at dawn, the semi-oval return capsule of Shenzhou V had already jettisoned its thermal insulation bottom and was slowly descending in mid-air, dragging a huge parachute.

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

The staff in the command and control hall, on the contrary, became relatively idle.

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

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

It has come to this point, and a little celebration is not like popping champagne in advance.

However, Shen Junrong was not among them.

"Although this is the fifth time, every time I see a spaceship passing through the black barrier, my heart still beats fast..."

He spoke to Chang Haonan while gently pounding his chest.

When people relax after being tense for a long time, they often show a stronger desire to express themselves.

Even veteran experts are no exception to this.

"I suddenly had an idea."

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

"If we can control the flight angle and aerodynamic shape of the reentry body at the same time, so that the reentry process changes from omnidirectional ablation to directional ablation, then the plasma area can be limited to part of the surface. Can we achieve normal communication in the blackout area?"

"what?"

The former was just speaking casually, but now his attention was completely focused on the slowly descending spacecraft.

As a result, I suddenly heard Chang Haonan say "normal communication in the blackout area".

The whole person was shocked immediately.

But I didn't hear the first half clearly, so I just stood there in a daze.

Chang Haonan also noticed 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 moment I didn't know how to answer.

Communication in blackout is actually a topic that has been studied for a long time.

But we have not been able to find a solution that is highly feasible in engineering.

Seeing this, Chang Haonan further explained:

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

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 the wave by the plasma. If we reduce the electron density at a certain point in the sheath, we can improve the transmittance of the electromagnetic wave at that position. For example, by changing the blunt-tip structure to a pointed cone structure, we 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...