Under the gaze of everyone, the rocket drew a white line of smoke in the blue sky. As the breeze blows, the smoke line begins to dissipate.

As for the rocket, the higher and higher it flies, in the end only a flashing bright spot remains. If it weren't for the clear and transparent sky, it would have disappeared from everyone's field of vision.

"At 21070 meters, the rocket is starting to fall!"

"The optical tracking observation team reported that the heat shield on the top of the rocket had been detached and the guidance parachute had been thrown."

"Pay close attention to the rocket landing attitude!"

"The grid board is open, and the attitude is normal!"

“21000、20000、19000……”

As the numbers on the air gradually fell, everyone once again clearly saw the figure of the rocket's whereabouts. Like a daytime meteor, the rocket dragged a faint wake and fell to the ground.

"16000, the main umbrella throws!"

"The optical tracking and observation team reported that the three main parachutes were all open and in normal condition."

Bang Bang Bang ...... The crowd in the control center and outside watching the scene applauded enthusiastically. As long as the main parachute is opened, this means that the entire re-entry experiment is more than half successful, and the rest of the experiment is waiting for the rocket to land.

And Wu Hao and they could also see through the naked eye that the rocket dragged three huge red and white parachutes and began to descend slowly. At this moment, the people in the control center also ran out, and everyone looked up at the sky and watched the figure of the rocket slowly descending.

"Affected by the rising wind speed at high altitude, the rocket began to drift in a northwesterly direction."

"How much offset?"

"It's expected to be about a kilometer."

"Continue to observe closely, notify the ground recovery team, and prepare to go to the relevant area to prepare for the fall of the rocket."

Hearing this order, Wu Hao beckoned and said, "Let's go, let's go to the scene too." ”

Zhang Jun nodded, then boarded an off-road vehicle with Wu Hao and sped towards the crash site of the rocket.

And behind their car, there were many other vehicles as well. Yu Chengwu sat in the car and urged the driver to hurry up, while holding the walkie-talkie and said: "Any situation can happen when the rocket lands, and there is still a lot of fuel left inside the rocket, which is to prepare for the landing sign thrust reversal and speed reduction." Therefore, inform everyone to keep a safe landing distance to avoid possible dangers.

When it landed safely, a fence line was set up immediately, and no one was allowed to approach it except professionals. Especially Mr. Wu and Mr. Zhang, hold him, protect their safety, and don't let them get close. ”

After saying this, Yu Chengwu yelled at the driver in front of him: "Hurry up!" ”

Wu Hao: To be honest, they didn't feel good in the car, and while leaning over the window to watch the rockets descending in the sky, they had to endure the bumps of the vehicle driving on the sand dunes.

Zhang Jun couldn't stand it after a few bumps, his face turned pale, and he was holding back.

Fortunately, this did not last long, and the vehicle stopped on top of a high sand dune. A number of vehicles have been parked on the dune, all of whom are members of the ground recovery team.

At this moment, the rocket is already very close to the ground, and there is still an altitude of eight or nine hundred meters in visual inspection. And the place where they probably landed was about one or two hundred meters in front of them.

At this distance, everyone can no longer continue to move forward, who knows if there will be a problem with the height of five or six hundred meters.

"Mr. Wu, why are you running so fast." Yu Chengwu got out of the car panting, and then said anxiously at Wu Hao.

"Hehe, I just want to go to the scene and see it for myself. You're busy, don't worry about us, we'll take care of ourselves. Wu Hao replied with a smile, and then glanced at Zhang Jun, who had already vomited and was drinking water.

"It's coming down, it's coming down." Someone shouted.

And this shout focused everyone's attention on the rockets and parachutes that were getting bigger and bigger overhead.

Zhang Jun, who was pale, also walked to Wu Hao's side at this moment, and then looked at the rocket above his head with a serious face.

I saw that the rocket was slowly falling under their gaze, and everyone's hearts were also raised to their throats.

The ignition and thrust reverser of the rocket engine before landing is crucial, and if it fails, the rocket will crash due to excessive speed, even if there is a parachute.

According to the design, when the main parachute is opened, the rocket will descend at a speed of 9 meters per second. Although this speed is much slower than that of a freefall, it is still very fast.

While it is possible to further increase the area of the parachute and thus further reduce the landing speed, this can also cause some other problems.

First of all, the increase in the area of the parachute means that the volume of the parachute when folded increases, and the weight will also increase. This also means that the rocket will carry more extra weight, which will increase the cost of launch.

Second, the larger the area of the parachute, the greater the wind surface and the greater the influence of air currents. In this way, the rocket is more sensitive to air currents when landing. The wind speed is a little stronger, and the rocket may be blown away by the parachute. This will affect the landing accuracy and may even lead to recovery failures and other problems.

Therefore, the size of the parachute and the weight of the rocket must be controlled at a relatively balanced point, and the landing should be neither too fast nor too slow.

To this end, scientists have installed a rocket thrust reverser at the tail end of such a returnable spacecraft. In order to start the rocket to boost and decelerate at the moment before the spacecraft lands. When the spacecraft lands, it can reach a low speed that can be tolerated, and protect the spacecraft from falling to the ground and being damaged by excessive speed.

For example, the first-stage rocket body of the returnable rocket they test-fired this time will instantly ignite the engine about 10 meters above the ground, and make the thrust of the engine reach the maximum in an instant.

However, this is certainly not enough for the original engines, and the design team also has three small solid-fuel rockets on the rocket's three landing gears to provide additional thrust.

The height of ten meters is still very high for us, but it is also the height of the rocket itself. And the speed at which the rocket descends is nine meters per second, which means that the rocket has only one second of reaction time.

At this second, the rocket engine must be fully ignited. This will not only have very demanding requirements for the rocket body control system, but also for the reliability of the rocket.

Either all the ignition was successful and the rocket landed safely, or the ignition failed and the rocket landed and crashed.

At the same time as Wu Hao was in a trance, a huge parachute appeared in front of him, and the rocket under the parachute descended rapidly under the gaze of everyone.

Then, when it was about to touch the ground, the tail engine suddenly ignited and erupted a huge flame, and this flame also rolled up a huge amount of sand and dust on the ground, mixed with the smoke produced by the combustion, and instantly enveloped the rocket.