Legendary Captain

Chapter 251 Prototype SST-001 (Seeking monthly votes!)

As Xu Qing's son, Xu Zijing possessed an excellent knowledge of aircraft; he could identify the funnel-shaped mist surrounding the aircraft with just one glance.

The sonic boom cloud, also known as the Prandtl-Glaue condensation cloud effect, occurs when an aircraft transitions from subsonic to supersonic speed. The sudden drop in air pressure behind the shock wave causes a significant decrease in temperature, leading to water vapor condensation and the formation of a cone-shaped cloud that spreads evenly outward from the leading edge of the wing, with the aircraft as the central axis.

This is a visual phenomenon observed when breaking the sound barrier. Sonic boom clouds can occur during most supersonic events, but this isn't absolute. Relatively speaking, any transonic event will almost always produce a shock wave.

Sonic boom clouds are more likely to form in environments with high air density or high humidity. Therefore, sonic boom clouds are more likely to form when an aircraft flies low over water to break the sound barrier.

"Dad, is that a fighter jet?" In Xu Zijing's mind, only fighter jets could break the sound barrier, but Xu Qing just said something about "the future of civil aviation." Is the future of civil aviation fighter jets? That doesn't make sense.

Xu Qing: "Why would I show you fighter jets?"

"It's not a fighter jet, but it's a sonic boom." Xu Zijing frowned. "Dad, you don't mean a supersonic passenger plane, do you?"

"Take a good look." Xu Qing said, taking out earplugs from his pocket and handing two to Xu Zijing: "It might be a bit noisy later, so wear them. By the way, stand firm, it'll be quite windy."

"Huh?" Xu Zijing took the earplugs, puzzled. "What? This is so strange."

Xu Qing didn't answer Xu Zijing's question, but instead took out a walkie-talkie and said, "Let's do another lap, fly lower."

"Huh?" Xu Zijing didn't know who his father was talking to, but he quickly realized. He squinted and looked up at the sky, and sure enough, just as he had expected, the plane had returned.

This time the plane flew much lower than before, and Xu Zijin could now clearly distinguish the details of the plane.

This was a delta wing configuration, and it appeared to lack a horizontal tail. The fuselage was extremely slender, and he couldn't find any obvious engine nacelles; in fact, Xu Zijing couldn't see the specific location of the engines. It seemed as if the engines had been integrated into the wings.

"Dad, is this a supersonic passenger plane?" Xu Zijing asked as soon as she did.

As soon as Xu Zijing finished speaking, the afterburner in the engine of the aircraft in the air suddenly activated, and an unimaginable amount of thrust propelled the aircraft back into the transonic phase.

That's right, this aircraft's engine is equipped with an afterburner, a feature unique to fighter jets. In fact, even without the afterburner, this aircraft can still accelerate to supersonic speeds, but its fuel efficiency is actually lower than when it has an afterburner.

Just as the plane was about to break the sound barrier, the sonic boom cloud reappeared. This time, because the plane was at a lower altitude, Xu Zijing could see the intermittently appearing sonic boom cloud more clearly, and its visual impact was even more stunning.

"Turbojet engine!" Xu Zijing's body trembled. Before he could react, a sonic boom instantly enveloped him, with the force of a thunderbolt from the heavens. Even with earplugs, Xu Zijing was still stunned.

"Dad, it's going too low!" Xu Zijing complained, covering her ears. "Why didn't you warn me? What if you go deaf?"

Xu Qing chuckled and took off her earplugs: "This must be your first time hearing a sonic boom, right? I thought you'd like it, but it turns out you just find it too noisy!"

Xu Zijing also took off her earbuds and cleaned her ears: "This is my first time hearing a sonic boom, but you don't have to go this low and be this close, do you?"

"Only when you're close can you hear clearly and truly appreciate it!"

"What's so great about that?" Xu Zijin pouted. "By the way, does this plane use a turbojet engine?"

"That's right!" Xu Qing nodded: "At high speeds, especially under supersonic conditions, the drag of turbofan engines is too great. If this problem cannot be solved, then we can only use turbojet engines."

Almost all large passenger aircraft today use turbofan engines. There's no other way; turbofan engines are far superior in terms of efficiency and economy, and the key lies in reducing exhaust velocity.

However, everything has its advantages and disadvantages. While the additional fan on the turbofan engine does make more efficient use of energy, it inevitably increases the air intake, which in turn increases wind resistance. This disadvantage is especially noticeable at high speeds.

Furthermore, air efficiency is poor at high altitudes, which limits the significance of high-bypass turbofan engines, resulting in poor high-altitude performance.

Therefore, turbojet engines are only suitable for certain specific models and operating environments.

Turbojet engines are great in every way, except for their high fuel consumption—and not just a little bit. Just looking at the massive amounts of hot gas ejected from the exhaust nozzle of a turbojet engine is enough to tell you just how inefficient it is.

In the civil aviation industry, economic efficiency is a very important criterion. Based on this criterion alone, oil-guzzling behemoths like turbojet engines simply cannot be considered for civil aviation.

However, due to the unique nature of supersonic cruise, most of the cruise phase takes place at altitudes exceeding 50,000 feet, while the normal cruise altitude for commercial airliners is around 30,000 feet.

Supersonic passenger planes cruise at the true stratosphere, at which altitudes the Earth's curvature can be observed with the naked eye.

At an altitude of 50,000 feet, turbofan engines are no longer well-suited to such an operating environment, especially high-bypass turbofan engines, which are at a greater disadvantage.

"Turbojet engines? Are they suitable? Are turbojet engines really practical for commercial airliners?" Xu Zijing asked doubtfully. "Didn't we have supersonic airliners before? They were just flashy but impractical! Dad, are you really sure?"

The concept of supersonic passenger aircraft has existed for a long time, and it has gone beyond just a concept, with prototypes and commercial models already in existence.

Moreover, there were not just one, but two supersonic passenger aircraft at the time. However, these two epoch-making models were ultimately lost in the long river of history, only causing ripples but failing to become a trend of the times.

The reasons for grounding these two supersonic passenger aircraft are complex, including unresolved noise and environmental issues, as well as profitability problems. Also, because the operating environment for supersonic flight differs drastically from that of ordinary civilian flight, these two aircraft incorporated many new-era technologies. The more new technologies are used, the more likely uncontrollable problems will arise.

However, these were only indirect causes. The most fatal factor was that both of these supersonic aircraft types were involved in serious air disasters, resulting in extremely heavy casualties.

An air crash is devastating for any aircraft model, especially a new one. Whenever an air crash occurs, people inevitably begin to question the safety of that aircraft.

Even if the designers can provide countless data and materials to support the safety of the aircraft, it will not eliminate the fear of an air crash in people's minds, at least not in the short term.

However, the technological environment is different now than before. Problems that the two supersonic models couldn't solve before are not so unsolvable in today's technological environment.

Civil aviation has been stuck in subsonic speeds for too long, and it's time to break the sound barrier; at least the technology is now sufficient to support doing so.

Indeed, for short to medium-distance operations, current subsonic flight speeds are sufficient. Introducing a supersonic passenger aircraft may not be a suitable solution, and it's highly likely that the costs will not be recouped.

However, Xu Qing felt that even if they didn't need it for the time being, they should still have it.

"I know that turbojet engines are indeed unsuitable. The research lab is currently focusing on low-bypass turbofan engines to replace turbojet engines." Xu Qing narrowed his eyes slightly. "My hope is that I will live to see the birth of this new engine."

If a model is to operate for a long time, the issue of profitability is unavoidable, but as long as it is equipped with a turbojet engine, this problem is almost unsolvable.

The turbojet engines currently installed on the prototype aircraft are 50% more efficient than those on the previous two supersonic aircraft, but they are only just breaking even.

In many cases, short-term losses or even no profit are acceptable because the future prospects are still bright. However, the fuel consumption problem of supersonic passenger aircraft engines is a fatal flaw. As long as this problem is not solved, the supersonic passenger aircraft project will likely remain a vanity project with limited commercial value.

Therefore, developing a low-bypass turbofan engine suitable for supersonic aircraft is a hurdle that must be overcome. Equipping a turbofan engine with a low-bypass turbofan engine means slightly sacrificing some speed advantage. After all, no matter how small the bypass, it can't be smaller than a turbojet engine with a zero bypass ratio. Increased drag inevitably means some compromise in terms of speed.

However, if the compromise on speed can be exchanged for a leap in economic efficiency, then it is well worth it.

The two supersonic passenger planes from long ago could cruise at Mach 2, more than twice as fast as ordinary passenger planes. If they had been equipped with low-bypass turbofan engines, their cruising speed might have been reduced to Mach 1.8. Although this was a decrease, the speed advantage was still extremely significant, and the reduction in fuel consumption could more than compensate for the speed loss.

However, such a low-bypass turbofan engine cannot be created simply by imagination. Because supersonic aircraft prioritize high-speed performance, they make compromises in their aerodynamic design. Supersonic passenger aircraft do not perform well aerodynamically at low speeds, requiring the engine to continuously output high power, thus increasing fuel consumption. If the bypass ratio is too low, fuel consumption will remain high at low speeds.

Therefore, how to balance the duct problem under high-speed and low-speed conditions is also a key area of ​​research.

As we all know, engine development is extremely time-consuming. Xu Qing wasn't joking when he said he'd be working on it in his lifetime.

Moreover, it's not just the engines that need to be changed; the aircraft's aerodynamic layout also needs to be altered.

As mentioned earlier, supersonic passenger aircraft sacrifice some aerodynamic performance at low speeds to accommodate high-speed conditions. Therefore, supersonic passenger aircraft have exceptionally high takeoff and landing speeds, sometimes reaching around 200 knots. This is 50 to 60 knots faster than the takeoff and landing speeds of current general aviation passenger aircraft.

It is precisely because of its insufficient aerodynamic performance in low-speed environments that it has to adopt high thrust and high speed to make up for its deficiencies in aerodynamic layout.

High takeoff and landing speeds are not necessarily a good thing, as they impose extremely stringent requirements on the length of the runway, which naturally limits the operating range of the aircraft.

A truly excellent aircraft should not make airports adapt to you, but rather you should be able to proactively adapt to most airports.

At the same time, the combination of high thrust and high speed naturally leads to very serious noise problems. The times have changed; people are far more concerned about their rights than before.

In the past, residents near the airport might have tolerated the noise of airplanes if it wasn't a serious problem. But things are different now. If the noise exceeds the standards, residents can easily sue the airport.

Once an airport gets involved in this type of lawsuit, it will inevitably consider restricting the operation of this type of aircraft. Therefore, the noise problem also needs to be addressed.

However, compared to the engine, the aerodynamic layout issues are relatively easier to solve. At least at the current pace of development, before Xu Qing passes away, all the structures except for the engine should be completed.

"Are we doing this as a family?" Xu Zijin asked in surprise. "Won't it be too much of a burden to research both the X10 and this model at the same time?"

Developing new models is inherently expensive, let alone developing two at once. Although Qingyuan Group has always been profitable, it couldn't withstand two money-devouring beasts opening their mouths at the same time.

Xu Zijin is somewhat interested in developing new models; otherwise, he wouldn't be visiting his family's research lab from time to time. However, he really feels that his father should act within his capabilities and not go too far, lest he squander the family fortune.

He didn't really care how much money Xu Qing would leave him, but it couldn't be too little. He needed enough to live comfortably for half a lifetime. However, given Xu Qing's current spending habits, he seriously doubted he'd need to work to earn money in his next life.

"The X10 doesn't use many new technologies, and its development cost is acceptable. The key is the one that flies in the sky, that's where the investment is huge. So far, its investment cost is almost twice that of the X10. But there have only been some breakthroughs in aerodynamic layout, and there hasn't been much progress on the engine." Even Xu Qing, who usually doesn't care about money, felt his heart skip a beat when talking about the investment cost of this supersonic aircraft.

Xu Zijing's face turned pale: "Dad, even if we have money, we can't spend it like this! This thing is too expensive. Let's do it one thing at a time. Once the X10 project starts to make a profit and we have more money, can we then work on a supersonic passenger plane? Trying to do two things at once is very risky."

"Don't worry, I know what I'm doing. Our family still has some savings, so we definitely won't go bankrupt. It just means you might get less money. You won't blame me, will you?" Xu Qing said.

To be honest, it's only because Qingyuan Group has monopolized almost half of the domestic civil aviation market for nearly 20 years that they have accumulated enough wealth; otherwise, it wouldn't be enough for Xu Qing to cause so much trouble.

Research on new models can easily lead to the predicament of investing money without any return. The X10 project is better off, as it doesn't involve many new technologies and mostly utilizes mature technologies, so the risks are manageable and the cost investment is relatively clear.

The only references for developing supersonic aircraft are two failed examples from decades ago. There are too many new paths to explore, the risks are extremely high, and there is a great possibility that huge investments will go down the drain.

However, Xu Qing still decided to begin research and development. The conditions for developing a supersonic passenger aircraft are now ripe; it's not a matter of forcing things to happen. Furthermore, the demand for differentiated services is becoming increasingly apparent in today's society. The high-end market for supersonic passenger aircraft remains relatively optimistic; at least, the embarrassing situation of no one flying on board won't occur.

Xu Qing's idea is to miniaturize and refine supersonic aircraft, initially focusing on high-end consumers and aircraft enthusiasts, and then expanding the market after gaining operational experience.

The concept of high-end consumers is easy to understand. For example, some business people have very high time requirements, and high-speed aircraft perfectly meet their needs. Aviation enthusiasts are purely a group of people with a passion for the sport. They fly on supersonic aircraft not for transportation, but for the experience. Moreover, this subculture is relatively narrow, so as long as the quality is excellent, the brand effect can spread relatively easily within this group. Many aviation enthusiasts also have strong purchasing power. Without solid financial resources, it's simply impossible to develop this interest.

Hearing Xu Qing say that, Xu Zijing pouted and said, "You guys earn all the money, so you can decide how to spend it. Just don't let me go hungry."

Xu Qing laughed heartily: "You don't need to worry about that, your dad will definitely not let you go hungry."

"Dad, is this still a prototype? Does it have a code name yet?"

Xu Qing nodded: "Got it, codename SST-001, Supersonic Transport Program!"

"If—and I mean if—you're still interested in this, could you take over after I leave, if you'd like?"

Xu Qing was self-aware; except in certain special circumstances, technology progresses in a spiral, and technological explosions only exist as a gift from God.

Based on the normal technical progress, Xu Qing estimated that this model might not be finalized before he passed away, which is why he wanted Xu Zijing to take over his work.

Xu Zijing was taken aback for a moment, then said with difficulty, "Dad, this is my interest, not a responsibility."

"Haha, I was being unreasonable." Xu Qing laughed on purpose, but felt a little dejected inside.

Xu Zijin loves flying, but she won't make flying her career; that's the difference.

Star Travel Airlines.

After Xu Xian was pulled aside by Li Chuan and said a few words, the two parted ways. When Xu Xian went to the door of the squadron office again, Qin Zongyang and Lu Xinyu were no longer there.

"Have they all gone in?" Xu Xian scratched his head, not bothering to go into their office to look for them, since there was nothing else to do anyway.

After thinking it over, Xu Xian decided to go to the flight medical station in the flight preparation room to schedule a medical check-up. He didn't have much to do during this period, so it was best to get the check-up done as soon as possible. Otherwise, once his parents returned from their trip abroad, along with Xu Sheng, the four of them would need to get together properly, and there wouldn't be enough time.

That's right. Xu Sheng had taken Xu Xian's advice and specifically called Xu Jingyang and Huang Ying to ask them to stay abroad a little longer, and to his surprise, Xu Jingyang and Huang Ying agreed. However, they should be back in a few days.

Xu Xian was just going to schedule a time, so he didn't need to bring any documents and went downstairs to the preparation room empty-handed.

But as he turned into the flight preparation room, he suddenly noticed a familiar figure huddled near the medical bay.

Xu Xian clicked his tongue. This back view looked very familiar, but he just couldn't remember it.

Immediately, he tried to recall while leaning closer to look.

They were talking to the medic over there, and on the medic's right, there was a file folder on the medic's table, which seemed to have been brought by the medic.

"Who is it?!" Xu Xian muttered to himself. As he got closer, he saw Qin Yue's profile clearly. Xu Xian froze for a moment, then exclaimed, "Qin Yue?"

Double monthly votes! It's almost the end of the month, please vote! I'm aiming for 1000 monthly votes!

(End of this chapter)