At present, there are three ways to recover rockets in the world, the first is to use the parachute group to let the detached core-stage rocket land under the deceleration of the parachute group; The second is to "install" wings on the rocket body, which is actually borrowed from the idea of the American space shuttle; As for the third way, it is the vertical landing method.

In November last year, Huaxia successfully used the parachute method to successfully recover the first-stage core-stage rocket body of an experimental rocket, and Russia has also used a similar method to successfully recover the first-stage core-stage rocket body.

But whether it is the first way or the second way, for the rocket body, it is a hard landing, because even if the parachute is large, no matter how big the wings installed on your rocket are, the rocket body does not have any buffer at the moment of landing, so these two recovery methods are still relatively large for the overall structure of the rocket body.

If you think about it, you can think of it, when people use parachutes, the speed of landing is still 7 meters / second, and in the same way, if you catch up with the landing technology, you can still fall and break your arm, not to mention the dozens of tons of arrow body! Even if the rocket body lands at a speed of 5 m/s during landing, it is equivalent to a hard fall! And whether it is a parachute or wing-based recovery method, the body of the arrow is landed horizontally!

But to adopt the method of vertical landing, this problem of damaging the overall structure of the rocket body does not exist.

When the Falcon 9 landed vertically, when the four supports at the bottom of the rocket touched the ground, the flames spewed out from the rocket engine had well offset the acceleration generated by the rocket body due to the free fall movement, especially when the rocket body landed, the landing speed of the rocket body was even lower than 1 m/s, and the four brackets themselves also had a cushioning effect. Therefore, the overall structural damage to the rocket body is almost negligible by adopting this method.

But again, the use of vertical landing method is also the most technically demanding. This is also why Musk's Star Exploration Program failed in the first three recycling experiments, and only succeeded in the fourth time.

However, once this vertical landing technique is mastered. Then the recovery of rockets in the future will no longer be a pipe dream.

In fact, among the vertical landing technology, there is another key technology, that is, the back-stroke jet thrust technology.

The so-called back-stroke jet thrust technology is, to put it bluntly, the technology that slows down the rocket body. When the first-stage core rocket is detached, there is still a certain amount of fuel inside it, which is used to provide recoil thrust for the final recoil range injection.

When the first-stage core-stage rocket body begins to fall in the form of a free-fall body at an altitude of more than 100 kilometers, if there is no reaction force, then the rocket body will reach 4.15 times the speed of sound at the moment of landing, that is, the terrifying 1414 meters.

And if the rocket body of the first-stage core-stage rocket weighing nearly 70 tons smashes to the ground at this speed. It was undoubtedly a disaster, and the consequence of it was that small meteorites had to be smashed to the ground even a few times. Therefore, in the process of the rocket body falling, the rocket engine should be ignited at a certain node, and the high-energy flame ejected by the rocket engine should be used to slow down the rocket body.

Then the question arises, when to start the rocket engine, and at what altitude to carry out this operation. And even if the rocket engine is ignited, it will definitely not be able to resist such a large falling force at one time. Then it must be designed, such a heavy rocket, how long the rocket engine needs to work continuously, how much buffer height needs to be left for the rocket body, and how much fuel is left in the rocket body, which must be implemented after extremely strict calculations.

Just like the body of the New Shepard first-stage rocket with an empty weight of less than ten tons recovered by Blue Origin. The rocket opened the deceleration plate at an altitude of about 6,100 meters above the ground, and then started the main engine of the rocket at an altitude of about 5,000 feet from the ground, that is, about 1,500 meters, and finally successfully decelerated the rocket body weighing about 10 tons to 2.1 m/s at an altitude of about 15 meters above the ground. The result is a safe and successful landing.

However, if the first-stage core-stage rocket body of Star-1 wants to successfully achieve a soft landing, it must not start decelerating at that altitude like the New Shepard, and the first-stage core-stage rocket of Star-1 needs to be slowed down at a higher altitude, so that the heavier Star-1 first-stage core-stage rocket body can land safely.

In fact, it is true, at an altitude of 12,000 kilometers from the ground, the six deceleration baffles located in the upper part of the first-stage core rocket body have been successfully opened under the control of the program, and the role of the deceleration baffle is beyond doubt.

Then, at an altitude of seven thousand meters above the ground, accompanied by the electronic sound of the control center, the voice prompt of "main engine start", everyone present saw that the main engine of the Star-1 first-stage core rocket suddenly lit up, and a large number of high-energy flames erupted from the four nozzles of the four main engines of Star-1 again.

The speed of the Starry Sky No. 1 first-stage core-stage rocket body, which was originally falling rapidly, suddenly decreased at a speed visible to the naked eye.

But at this time, after nearly 100 kilometers of falling, the gravitational potential energy carried by the huge arrow body is still not something that the powerful thrust of the engine can resist.

At this time, the engine is ignited in order to further provide recoil force to the rocket body, and try to consume the huge gravitational potential energy on the rocket body, but the effect of this recoil force is not very large, after all, this recoil force is achieved by relying on air.

In order to make the recoil force generated by the rocket engine really work, it is still necessary to reach the height of about 50 meters close to the ground, because at that height, the high-energy flame flow ejected from the engine can directly act on the ground, so that the recoil force obtained by the rocket body is greatly improved.

Under the gaze of countless pairs of eyes in the control center and on the banks of the Indian River in Titusville in the distance, the huge Starry Sky No. 1 first-stage core rocket body quickly descended to the height of the interaction between the engine flame flow and the ground, and the rocket body that was originally falling rapidly at an unstoppable speed miraculously paused, and at this time, the four huge landing brackets also quickly opened.

In the space near the flame stream, a large air mass similar to that of a tornado landing was generated, which was caused by the turbulence of the air flow caused by the high temperature and high energy flame flow when it hit the ground and reflected it. The next moment, a large cloud of smoke suddenly rose from the concrete landing site below the rocket.

The next moment, after a few shakes at a height of about a few meters above the ground, the huge rocket body finally landed on the ground slowly under the worried gaze of everyone (to be continued). )