Military Technology

Yu Chengwu nodded with a smile and said: "It can also be called the beggar's version, but the technical difficulty is not much lower. If it is really that simple, how can there be no rockets with this kind of technology?"

difficult? Zhang Jun asked subconsciously.

Yu Chengwu nodded in response: "Actually, the principle is very simple, and the technology is not too complicated, but it is difficult in some core technologies and manufacturing processes.

First of all, the rocket body of the rocket is very heavy, even the empty rocket body without fuel is very heavy. If the method of parachute landing and recovery is adopted, it means that a group of very large parachutes is required.

But in this way, the weight of the umbrella bag is greatly increased. As we all know, the weight of the rocket is all calculated. The sudden addition of such a large parachute means that the rocket's carrying capacity will be greatly reduced.

And this has created another problem. If the rocket's carrying capacity is weak, the weight of satellites or other loads that can be carried is very limited.

This not only makes the use of the rocket very limited, but also greatly increases the cost of the rocket, so that even if it can be reused, it is not cost-effective. "

Speaking of this, Yu Chengwu paused for a moment, and then continued: "Then there is the recovery technology. The method of using a parachute is certainly simpler than the reverse thrust landing of SPX's Falcon rocket, and the cost will also be lower. .

But it also has its difficulties and its shortcomings. For example, the large umbrella bag and weight mentioned above, this is a problem.

Moreover, the method of parachute landing and recovery is easily affected by the wind speed in the air, thereby changing the landing location. This not only increases the risk of landing recovery virtually, but also increases the difficulty of recovery.

Finally, the core and most troublesome technical problem is still the rocket engine. Unlike disposable rockets, this recyclable and repeatable rocket has stricter requirements on the quality and various indicators of the engine.

At present, this type of recoverable rocket mainly recovers only the first-level rocket body of the rocket, and the second-level rocket body is too difficult, so it is generally not recovered. The booster can also be recovered, but generally the conventional launch mission does not require the booster to provide additional thrust.

Now SPX's Falcon rocket has begun to explore and recover this fairing again, but we are not considering this aspect at present.

We are now mainly developing single-unit multi-set launch vehicles, so taking this as an example, the working flight time of most rocket stages is about 200 seconds, that is, more than three minutes.

Generally, the rocket only needs to consider the time of more than 200 seconds. Even if it is rich, it will not be too many more than ten seconds. Therefore, the entire rocket body structure, system, engine, and materials are designed and manufactured according to this standard.

But what our retractable rocket body considers is not just the short 200 seconds, but thousands of seconds, or even tens of thousands of seconds of working time. This has more stringent requirements for the rocket body structure, system, engine, and materials of the entire rocket.

Only in this way can we control the cost so that it can reach a launch and delivery price that is cheaper than disposable rockets. "

"Is it so difficult?" An entourage who came with Wu Hao and the others couldn't help asking this time.

Yu Chengwu glanced at this person, then nodded and smiled wryly: "It is several times or even dozens of times more difficult than you imagined.

Let me simply give two examples, and you will know when you are done.

First of all, in terms of the structural design and material processing and manufacturing of the rocket body, because of the need to consider reusable use, it is necessary to strengthen the structural strength of the rocket body.

This is not only from the structural design, but also from the material and processing. But in this way, the weight of the rocket body is virtually increased, which not only has a huge adverse effect on the rocket's carrying capacity, but also brings trouble to the recovery of the rocket.

Increase the weight of the rocket body, affecting the carrying capacity of the rocket,

This will undoubtedly greatly increase the cost of a single launch, which is not conducive to market competition.

Similarly, increasing the weight of the rocket body means that the difficulty of landing and recovering will also be mostly increased. Not only must the parachute be larger, but the reverse thrust before landing must also be increased, which brings a series of problems.

But if the rocket body is not strengthened, many problems will be solved, but it will cause huge troubles in recycling. Even if the parachute and impending reverse thrust technology are used, it will still cause irreversible damage to the fragile rocket body when it lands, which makes the recovery fail and loses the role of reuse.

The second is on the rocket engine technology. During rocket launch, the engine has to withstand the high temperature and high pressure of thousands of degrees during fuel injection.

Traditional one-time rockets also have high requirements for this, but compared with this kind of recoverable rocket, the requirements are much lower. It only needs to consider the working time of two hundred seconds, and the others don't need to be considered.

Therefore, the overall structural design, materials, and manufacturing technology of the engine do not need to be so harsh. Recoverable rockets are different because they need to be used multiple times, which means that the engines used not only have to have a stronger structure, but also have harder and more durable materials, and higher requirements for manufacturing technology.

At present, it seems that the only countries and companies that have mastered this rocket engine technology are the Falcon rockets of Lao Mi's SPX company.

I heard that our National Aerospace Corporation has also been doing it in the past few years, but the outside world does not know how it is going.

There are many other technologies like this, such as fuel formula, rocket sub-control system, and the most important grid plate rudder technology for recoverable rockets. "

"In this case, why don't we concentrate on developing easier one-time rockets, why do we have to make such time-consuming and labor-intensive recyclable rockets that may not be successful?" Some people in the listening crowd questioned.

Hehe, Yu Chengwu shook his head with a smile: "Disposable rockets are easy, but they are already very common. Even if we come up with a more reliable and cheaper integrated rocket, it will be difficult to break through in this field.

In this field, our domestic aerospace group can be said to have done very well, and it is difficult for us to compete with the other party, let alone the other party's national prefix.

Second, retractable rockets are relatively difficult at present, and the research and development costs are relatively high. But once the research and development is successful, it will bring huge benefits.

Moreover, we can apply this series of technologies to other space exploration missions in the future. For example, this reusable rocket engine technology can be applied to the spacecraft and spacecraft we design and develop in the future. "

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