Chapter 57: Dynamic Equilibrium

Having work to do was the best news. Director Chen, whose sharp ears had caught wind of activity in this area, gave a few instructions and made his way over. Director Chen appeared to be in his forties, which in the aerospace field was considered the prime of life.

“See over there? That’s Director Chen. He’s in charge of the full-engine testing here. They still have some work left, but not much—just a matter of ten days or so for you.”

Taking advantage of the time before Director Chen arrived, Director Li gave a brief introduction. When Director Chen came over, Li was about to introduce Yang Hui, but Yang Hui was proactive and spoke up first.

“Hello, Director Chen. I’m Yang Hui, and this is my colleague, Zhong Jianshe. We’re from the same project team, working on micro turbojets. We’re here today to trouble you for some testing.”

Seeing this young man introduce himself, Director Chen extended his hand to shake with Yang Hui, then reached out to Zhong Jianshe as well.

“Hello, I’m Chen Li. I oversee the full-engine testing in this area.”

Now that the two had connected, Director Li didn’t say much more. One of the devices nearby was undergoing major repairs, and he needed to go oversee the work on site.

“Alright, take your time. I have to head back; there’s something going on over there.”

“Okay, go ahead, Old Li. I’m here, don’t worry.” “Thank you, Director Li.” Yang Hui and Director Chen responded differently.

Director Chen glanced at the boxes still on the trolley, then led the way, bringing Yang Hui and Zhong Jianshe to the full-engine testing center. They put down the trolley, carefully unloaded the boxes, and opened them to reveal the parts inside.

“Still just parts? Then we have to assemble first.” Seeing the heap of turbojet parts in the box, Director Chen, seasoned in scientific research, found it quite unusual. This must be the first time someone brought parts for full-engine testing, planning to assemble on site.

Since Director Chen wasn’t pleased with the turbojet in its parts state, Yang Hui said nothing and began assembling.

He fixed the diffuser, guide vanes, bearing supports, and combustion chamber to the inner wall of the casing. Then he affixed the centrifugal impeller onto the bearing, inserted it through the bearing support hole from the intake direction, and finally secured the turbine at the other end of the bearing. The general shape began to emerge—the guide cone and fuel lines were simpler, finished in a few moves.

Watching the micro turbojet come together with such fluidity, Director Chen felt as if his eyes were deceiving him. Could this turbojet really spin up? That was his chief concern.

The last component, the starter—a small electric motor—was mounted in front of the intake with a bracket. The motor’s output shaft meshed with the turbojet’s main shaft via gears, completing the assembly.

“This is the turbojet you designed? How much thrust can it produce?” Director Chen clearly wasn’t optimistic. For someone accustomed to engines measured in tons of thrust, this little thing hardly warranted attention.

“We’re aiming for eight to twelve kilograms. The actual result will depend on your testing, but I’m confident there won’t be any issues.”

“Alright, leave it here for now. Assemble another rotor and take it over for dynamic balancing. Once that’s finished, put it together, add lubricating oil, and bring it here for testing.”

Following Director Chen’s instructions, Yang Hui assembled another rotor and brought it to the dynamic balancing machine for calibration. Dynamic balancing is essential for turbine machinery; without it, the consequences are simple—catastrophic failure and injury.

Dynamic balancing aligns the rotor’s center of mass with its axis of rotation, minimizing centrifugal force fluctuations during operation. Simply put, it ensures the rotor outputs smoothly and operates steadily.

Yang Hui’s micro turbojet was truly tiny. He handed it to the staff, who mounted it on the machine, corrected any imbalances, and quickly completed the dynamic balancing.

With the balanced rotor reassembled and the other parts installed, the turbojet was ready. Now, it was time to put a month’s work to the test.

“Jianshe, assemble the remaining rotors and take them over for dynamic balancing.”

He instructed Zhong Jianshe, who had been idle, to finish the remaining rotors. Yang Hui then went to find Director Chen to begin testing.

“This little thing really doesn’t fit in here. All our testing equipment is for big engines; testing something this small will require us to modify the setup.”

Holding the turbojet Yang Hui had brought over, Director Chen personally mounted it onto the test stand—though now, “test rack” was more accurate. To test Yang Hui’s tiny engine, he had to improvise with brackets to secure it. The micro turbojet was perched on the rack, earning its new title.

This was a simple test run; as long as it could operate smoothly, it would be considered a success. There were no extra equipment lines installed.

Though he had little hope for the small engine’s thrust, people were genuinely interested in whether it could run. The design was so simple that success would mark a major milestone in turbojet development. As a result, everyone involved in the test was attentive; witnessing such a small engine was a novelty.

“Ah, I made it just in time.”

“At least I’m not late.”

A crowd gathered—the entire project team except for Zhong Jianshe, who quickly joined them.

“Leader Yang, there’s a specialist handling dynamic balancing over there. I came over after assembling the rotor.”

“Alright, let’s watch the test together.”

The team was clearly invested; as soon as they heard about the test, they all rushed over.

“Alright, Director Chen, let’s begin. We’re in the safety zone, no issues here.” Yang Hui led everyone to the designated area, confirmed their safety, and signaled to start the test.

“Young man, did you build this?”

A stranger’s voice made all six turn, facing a man in his fifties, thick glasses perched on his nose—an old hand at design, clearly deserving respect.

“Yes, we designed this simple turbojet engine for a model aircraft. The only notable feature is its low cost. Today is its first test run.” The quick-tongued Xie Lianfa replied, faster than anyone else.

“Young people are indeed capable. I, Old Wen, have been at this for years, and it’s the first time I’ve seen a turbojet designed for model aircraft. This is pioneering work.”

Old Wen immediately recognized the engine’s significance. As the first to break ground, their names would be recorded in history. Turbojet engines for model aircraft wouldn't appear until 1993, when an obscure French company released one. Yang Hui and his team were truly trailblazers.

“No, no, this was all proposed by Leader Yang. The whole model aircraft project was his idea.”

The modest Xie Lianfa quickly credited Yang Hui, feeling unworthy of such high praise.

“Test preparations underway. Connect starter power.”

At Director Chen’s command, the small starter motor in front of the turbojet was powered up, spinning the main shaft and impeller, compressing air into the combustion chamber. Of course, the little motor couldn’t achieve the highest RPM, so the airflow was limited. Luckily, ignition was with propane, so the compressed air was just sufficient.

“Introduce propane. Prepare for ignition.”

Watching the complicated startup of the micro turbojet, Director Chen felt a pang of helplessness. The little engine looked unimpressive but was tricky to operate—unlike the larger engines in the facility, which started at the push of a button.

With propane introduced, Director Chen personally pressed the spark plug switch. A faint current flowed to the plug, and an instant spark ignited.

That tiny spark ignited the restless propane-air mixture in the combustion chamber, triggering intense combustion. The confined space forced the fiery plume toward the guide vanes and then to the turbine.

The raging flame assaulted the turbine, gradually increasing its speed, driving the centrifugal impeller past the starter motor’s RPM. In that moment, the engine had successfully launched.

Disconnecting the starter power, the turbojet continued to spin smoothly, marking an auspicious beginning.