Genius is just the threshold for me!

Lin Dong returned home around 5 p.m.

Because Lin Dong wasn't home for dinner, Zhang Xiali was preparing to go out with Lin Weiliang.

Upon seeing Lin Dong return, Zhang Xiali pointed to the two gifts on the table and carefully explained their contents.

"Xiao Dong, when you go over there later, don't forget to bring the two gifts from the living room table. They're Qingling's birthday presents from your dad and me."

"understood."

Lin Dong casually agreed, his mind preoccupied. He changed his shoes, went into the study, took out his laptop, and logged into Wang Xingguo's email.

"Let's go..."

Seeing this, Lin Weiliang knew what Lin Dong was thinking. He stopped Zhang Xiali from saying anything more and gestured for her to leave so as not to disturb them.

Zhang Xiali nodded without saying anything more. The two changed their shoes, gently opened the door, and went outside together.

"The original data for the wing is sufficient..."

Lin Dong saw the latest email from Engineer Cai, opened the data inside, took out paper and pen, and calculated seriously for more than ten minutes before finally determining three sets of precise values ​​for rigidity and elasticity.

Three groups, each corresponding to a wing design scheme.

One option is the variable-sweep wing design of the Tu-160.

One option is the double delta wing design of the Sukhoi T-4.

The last option is the delta wing design for the Dassault Mirage IV bomber and the Vulcan bomber.

In terms of technological maturity, the first variable-sweep wing is undoubtedly the most mature.

With its variable wing structure, the wings can be adjusted between 20° and 65°. The wings can be deployed during low-speed takeoff and landing to generate greater lift, and retracted during high-speed penetration to minimize drag, ultimately achieving low-speed stability and supersonic penetration.

The relationship between the wing angle and speed can be likened to the arms of a human wingsuit flyer.

When a wingsuit flyer's arms are fully extended, with the angle between the arms and the horizontal direction of the body being zero, the arm span is at its maximum, the lift provided by the wingsuit is at its strongest, and low-speed takeoff and landing will be more stable, but the drag will be at its greatest.

As you pull your arms towards your body, the angle between your arms and the horizontal direction relative to your body increases. At this point, your arm span decreases, the lift provided by the wingsuit decreases, but the drag is smaller, and you will be faster.

According to modern aviation research, it is almost impossible for a swept-wing bomber to break the supersonic barrier if the angle is less than 40 degrees.

Because at this speed, the shock wave drag will be very large, unless the engine is used to forcefully push the vehicle forward regardless of fuel consumption.

If you want to design a supersonic aircraft, the swept wing angle must be above 55 degrees. This will result in a smaller shock wave drag surface, making it easier to break through the supersonic barrier.

However, with an increased wing angle and a decreased wingspan, lift at low speeds will decrease, requiring higher speeds for takeoff and landing, which will reduce the stability of takeoff and landing.

For a large bomber weighing over 200 tons, higher takeoff and landing speeds and lower takeoff and landing stability undoubtedly pose a terrifying hidden danger...

"But while the variable-sweep wing design is mature, its drawback is that it can't provide any experience for the future..." Lin Dong thought for a moment, then picked up his pen and crossed out the first set of parameters.

The variable-sweep wing design is currently the most mature and stable heavy bomber design, and all bombers with a payload of more than 30 tons worldwide use this design.

However, in the current view, the biggest advantage of this approach has become its biggest disadvantage, leaving no way forward. Apart from building a large bomber, it offers no help whatsoever for exploration and research in other fields.

In addition, the massive variable mechanical structure will increase the fuselage empty weight by more than 10 tons, and there are also many mechanical maintenance issues.

The large gap at the junction of the wing root and the fuselage can also create a strong radar reflection source, increasing the design difficulty of stealth solutions.

"The Sukhoi T-4's double delta wing, and the Dassault Mirage IV bomber and the Vulcan bomber's large delta wing..." Lin Dong looked at the remaining two options.

Compared to the variable-sweep wing design, neither of these two designs is as mature in the field of large bombers, because so far there are only concepts and prototypes, and no concrete mass production plans.

The double delta wing achieves supersonic penetration by using a pair of large swept inner wings and adds a pair of small-angled outer wings to increase lift, thus achieving a balance between the two.

But if you try to do both, it means you're not proficient in either.

The Sukhoi T-4's supersonic performance is inferior to that of the Tu-160, and its low-speed takeoff and landing stability is also inferior to that of the Tu-160.

Ultimately, the Soviet Union built a prototype, conducted some test flights, and then abandoned it, deeming it useless.

The Phantom's large delta wing, consisting of only one pair of large swept-back delta wings, is specifically designed for high speeds.

However, because it only has one pair of large swept delta wings, its low-speed takeoff and landing performance is very poor, which requires the use of a blown flap technology.

By blowing air into the flaps, the adhesion of the airflow to the flaps is increased, thereby improving the stability of low-speed takeoff and landing.

However, the blow-out flap technology requires the air to be drawn from the engine, which can affect engine performance.

Meanwhile, the air gaps in the flaps will create strong radar reflection sources, and the air-blowing structure will also encroach on the fuel tank space inside the wing.

This is undoubtedly an unacceptable point for strategic bombers where range is a priority over payload.

"Every solution has its advantages and disadvantages... Even I can't change the laws of physics; I can only maximize the advantages and minimize the disadvantages by choosing the most suitable solution."

After thinking carefully for a moment, Lin Dong picked up a pen and crossed out the second set of Sukhoi T-4 double delta wing designs.

The advantage of the double delta wing is its simplicity; the design is not complicated and the technology is not difficult. However, it pleases neither side and cannot satisfy either side.

At the same time, the solution to the takeoff and landing problem by adding a pair of small outer wings is a shortcut and cannot be further developed.

Then Lin Dong crossed out the third group of delta wing + blown flap technology and rewrote it as - tailless delta wing + variable cycle range extender + vector thrust!

"Unfortunately, with the current level of industrial technology, the cost and maintenance of tailless flying wing stealth designs are too expensive."

Otherwise, removing the tail fin of the delta wing, adding stealth design, and a variable-cycle range extender would be a complete, one-step solution for the H-20…”

Lin Dong looked at the finalized plan and muttered to himself.

Tailless delta wing – this can be considered a forward-mounted flight control version of the flying wing layout of the H-20 bomber and sixth-generation fighter jet more than a decade later.

Neither has a tail fin; however, the delta wing has a vertical stabilizer and a conventional rudder, while the flying wing does not.

Therefore, the flight control programs, aerodynamic designs, and flight data of the two are largely the same, which can provide a wealth of exploration experience for future sixth-generation fighters.

However, tailless delta wings have the same drawbacks as delta wings.

All of these issues stem from insufficient lift during takeoff and landing, inadequate stability, the impact of external munitions on the aerodynamic layout of the fuselage, and an inherently limited range.

However, these problems can all be solved through technology.

The triple-circuit design improves fuel efficiency and compensates for insufficient range.

External munitions affect aerodynamic layout, but this can be mitigated through better electronic control technology, flight control algorithms, and design.

"This approach relies too heavily on engine performance, and it also places higher demands on engine control and the matching of the airframe's flight control system..."

However, within the technical framework, the difficulties can be overcome; a few more tests and modifications to the engine design will suffice.

Lin Dong pulled out the original engine solution, took out paper and pen and checked it for a few minutes, then created a new email.

[Wang Xingguo]: Chief Engineer Jiao (624), please adjust several sets of engine tests according to the following data and provide specific test data.

Ding-dong-

The email had just been sent when a new email popped up.

[Chengfei Guo Engineer]: Engineer Wang, these are the accuracy and stress control data after the improvement of the large-scale welding process, based on the required workpiece size parameters...

Lin Dong glanced at the file, then clicked the mouse to open the attached file, where rows of data came into view.

"The precision and stress control are still somewhat lacking..."

Lin Dong frowned slightly.

Due to their massive size, most of the components of large bombers need to be forged using a 3-ton hydraulic press.

After forging, the weld seams are often seven or eight meters or even more than ten meters long, and they are required to be welded in one go with precise stress control.

Even the slightest oversight or defect could become a fatal weakness given the takeoff weight of over 200 tons and supersonic speed.

The immense weight or supersonic shockwave can directly crush weak points or tear them apart.

The industrial challenges behind these two issues can be addressed by a handful of countries worldwide.

"Looks like I still need to learn from others and find a master welder..."

Lin Dong thought for a moment, inquired about Wang Xingguo's standby status, found the email contact of the chief engineer of Institute 719, opened another email and began to compose.

[Wang Xingguo]: Mr. Wu, hello. Can the large submarine welding technology jointly developed by your institute and Bohai Heavy Industry meet the following welding process precision and stress control requirements...?

Ding-dong-

The person on the other end seemed to still be at get off work, sitting in front of their computer. I sent the email and received a reply in less than two minutes.

[Chief Engineer Wu of Institute 719]: Hello, Engineer Wang, this welding process requirement can be met, but the working environment is different, and some details need to be adjusted and improved.

[Wang Xingguo]: Thank you, Engineer Wu. I will submit a joint technology project to headquarters and arrange for someone to come to your place to learn from your experience. The relevant technical expenses will be settled through the project.

[Chief Engineer Wu of Institute 719]: Sure, once the project is assigned, I will arrange for personnel to follow up.

"Hmm, that's better than the electronics industry that's always holding us back... It seems like the domestic submarine research and manufacturing industry isn't too busy lately."

Upon seeing this reply, Lin Dong quickly switched interfaces and submitted a project application. He then sent the relevant information to Engineer Guo of Chengdu Aircraft Industry Group and copied it to Xu Ziming, asking the production and R&D department to arrange for professionals to travel to Chengdu to learn from their experience.

Ding-dong-

[Xu Qingling]: Dongdong, it's time to eat.

[Lin Dong]: Is Uncle Xu home?

[Xu Qingling]: He's at home. He didn't invite anyone this year; he's at home tonight.

When parents, especially fathers, are at home, the children tend to be more reserved.

When they have gatherings and need to invite friends over, Xu Ziming, Huang Xinhua, Xia Tianqiang, and others will go over to work overtime or go out to have tea or go fishing.

[Lin Dong]: It's fine if you're at home. I'll come over now.

Lin Dong replied, took a file folder containing the thermal protection solution for the combustion chamber of a rotary detonation engine, and then took the birthday gift that Zhang Xiali and Lin Weiliang had prepared for Xu Qingling before heading out to Xu Qingling's house...