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

Hard? Zhang Jun asked subconsciously.

Yu Chengwu nodded and responded: "In fact, 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 is very heavy, even if it is empty without fuel. If you use parachute landing and recovery, it means a large set of parachutes.

However, in this way, the weight of the umbrella bag has increased significantly. As you know, in terms of rocket load, it is all about restraint, and suddenly adding such a large umbrella bag means that the carrying capacity of the rocket will be greatly reduced.

And this breeds another problem, if the carrying capacity of the rocket is weak, then the weight of the satellite or other payload that can be carried is very limited.

Not only will this make the use of the rocket very limited, but it will also greatly increase the cost of the rocket, so that even if it can be reused, it will not be cost-effective. ”

Speaking of this, Yu Chengwu paused, and then continued: "Then there is the recycling technology. The use of parachutes is of course simpler and less expensive than the thrust reverser landing of SPX's Falcon rockets.

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

Moreover, with this parachute landing recovery method, it is easy to be affected by the wind speed in the air, thus changing the landing site. This not only invisibly increases the risk of landing and recovery, but also increases the difficulty of recovery.

Finally, the core and most troublesome technical problem is still in the rocket engine. Different from disposable rockets, this kind of recyclable and repetitive rocket has more stringent requirements for the quality and various indicators of the engine.

At present, this kind of recyclable rocket mainly recovers only the first stage of the rocket, and the second stage is too difficult and generally not recovered. Boosters can also be recovered, but boosters are not required to provide additional thrust for regular launch missions.

Now SPX's Falcon rocket is back in the process of recovering the fairing, but we're not considering that at the moment.

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

Generally, rockets only need to consider these more than 200 seconds, and even if they are rich, more than ten seconds will not be too much. Therefore, the entire rocket body structure, system, engine, and materials are designed and manufactured in accordance with this standard.

But what we consider about this retractable rocket body is not only the short 200 seconds, but thousands of seconds, or even tens of thousands of seconds. This has more stringent requirements for the structure, system, engine, and materials of the entire rocket body.

Only in this way will we be able to bring the cost under control so that it can be launched at a cheaper price than a single-use rocket. ”

"Is it that hard?" This time, an entourage who came with Wu Hao and them couldn't help asking.

Yu Chengwu glanced at this person, then nodded and said with a wry smile: "It's several times or even dozens of times more difficult than you think."

I'll just give you two simple examples, and you'll know when you're done.

First of all, in the structural design and material processing and manufacturing of the rocket body, because it is necessary 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 and manufacturing. However, this will invisibly increase the weight of the rocket body, which will not only have a huge adverse impact on the carrying capacity of the rocket, but also bring trouble to the recovery of the rocket.

Increasing the weight of the rocket body will affect the carrying capacity of the rocket, which will undoubtedly greatly increase the cost of a single launch, which is not conducive to market competition.

Similarly, increasing the weight of the arrow means that it will be much more difficult to recover when landing. Not only should the parachute be larger, but the thrust reverse, just before landing, should be increased, which brings a series of problems.

However, if the rocket body is not strengthened, this will certainly solve many problems, but it will cause huge problems in recovery. Even if the parachute and landing thrust reverser technology are used, it will still bring irreversible damage to the fragile rocket body when landing, thus making the recovery fail and lose the role of reuse.

The second is in the rocket engine technology, in the rocket launch, the engine has to withstand thousands of degrees of high temperature and high pressure when the fuel is injected.

Traditional single-use rockets also have high requirements for this, but the requirements are much lower than those of this recyclable rocket. It only takes into account the 200 seconds of working time, and nothing else.

Therefore, there is no need to be so harsh on the overall structural design, materials, and manufacturing technology of the engine. Recyclable rockets are different because they have to be used multiple times, which means that the engine used must not only be structurally strong, but also have harder and more durable materials, and the manufacturing technology also has higher requirements.

At present, it seems that the only country and enterprise that has mastered this rocket engine technology is the Falcon rocket of Lao Mi's SPX company.

I heard that our National Aerospace Group has also been engaged in it in recent years, but the outside world still doesn't know how it is progressing.

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

"In that case, why don't we concentrate on developing an easier disposable rocket, and why do we have to make this kind of time-consuming, labor-intensive and not necessarily successful recyclable rocket?" In the crowd of people who were there to listen, someone questioned.

Hehe, Yu Chengwu smiled and shook his head: "Disposable rockets are easy, but they are already very common. Even if we come up with a more reliable and cheaper one-piece 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 each other, not to mention that the other party is still a national character.

Second, it is more difficult to retract rockets now, and the cost of research and development is relatively high. But once the 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 space vehicles and spacecraft we design and develop in the future. ”

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