“… so, the initial concept was to draw in air from the front of the propulsion system, combust it in this internal combustion chamber, and use that force to rotate the blades attached at the rear. Those blades would then transfer their rotational force to the propulsion propeller.”

When Jang Yeong-sil finished his explanation, Hyang couldn’t close his gaping mouth.

What is this monster! A turboprop? Is he really not a freaking alien?

“Your Majesty?”

Snapping back to his senses at Jang Yeong-sil’s voice, Hyang asked:

“What do you estimate are the chances of success?”

To Hyang’s curiosity-filled question, Jang Yeong-sil bowed his head with a troubled expression.

“Though I am humbled to report this, the probability of realization is extremely low, Your Majesty.”

“What are the reasons?”

Jang Yeong-sil explained why the probability of success was so low.

• First: The fuel is problematic. Coal has too many limitations for properly utilizing the combustion chamber concept. They tried using powdered coal to resolve this, but proper combustion still couldn’t be achieved.
• Second: The material for constructing the engine is problematic. They had tried all the iron types they’d developed, but durability was far too low under high-temperature, high-pressure conditions.

“… While there’s no major issue with multi-blade engines using steam from steam engines as they only need to withstand steam heat, the combustion chamber’s heat is problematic. To generate proper power, it would need temperatures hot enough to melt iron at minimum.”

“I see. So it’s impossible right now?”

“Yes, Your Majesty.”

Hyang silently nodded at Jang Yeong-sil’s response. Inwardly, however, he was sighing with relief.

That’s right! This is how it should be! Imagine if a proper turboprop engine came out of this! That would be alien technology, not human!

While Hyang was internally sighing with relief, Jang Yeong-sil became restless. This was because Hyang maintained his silence.

Finally, Jang Yeong-sil brought out “Plan B.”

“I have thought of something new, Your Majesty!”

“What is it?”

“Using Divine Fire Arrows instead!”

“Divine Fire Arrows? You mean using gunpowder as fuel?”

“Yes, Your Majesty!”

After thinking briefly about Jang Yeong-sil’s answer, Hyang immediately began pointing out issues.

“Do you remember why we retired all Divine Fire Arrows except the small ones used by the military for emergency communications?”

“Because of the explosions from the gunpowder used as propellant, Your Majesty.”

“And you haven’t forgotten that despite considerable efforts to resolve that issue, we ultimately failed and had to retire them?”

At Hyang’s observation, Jang Yeong-sil’s head drooped.

The gunpowder rockets symbolized by the Divine Fire Arrows were extremely unstable devices.

At the crossroads between instantaneous explosion and sustained combustion, many experiments were needed to maintain the latter.

The result of those experiments was to create a conical iron cap covered with a paper body packed with gunpowder. When the cap was removed, the conical space would serve as the combustion chamber.

While this method enabled minimally stable launches, the risk of explosion remained quite high due to gunpowder’s properties. In particular, the large Divine Fire Arrows using massive amounts of gunpowder were far more dangerous than their smaller counterparts.

Moreover, using gunpowder – and large quantities of it – as fuel made both manufacturing and maintenance costs considerably expensive.

Therefore, when artillery performance greatly improved through Hyang’s enthusiasm, and when Flying Thunder Bombs and long rifles were developed and mass-produced, the large and mountain-type Divine Fire Arrows were retired.

However, retirement didn’t mean complete disappearance.

-Development of suitable fuel for Divine Fire Arrow propulsion. -Development of methods to control Divine Fire Arrow thrust.

Such problems were registered in the challenge records. Of course, they were classified as Supreme grade, termed “Moving Mountains.”

Hanging his head at Hyang’s points, Jang Yeong-sil carefully offered an alternative.

“What if we made the body from iron instead of paper, Your Majesty?”

“Would that structure and material work with that body attached?”

“I think we could use iron instead of wood.”

“Then the weight would increase, requiring larger Divine Fire Arrows, which would make the wings heavier too – have you forgotten the term ‘vicious cycle’?”

“Ah…”

“And what about the thrust control problem registered in the challenge records?”

At Hyang’s points, Jang Yeong-sil finally raised the white flag.

“I apologize, Your Majesty. My thoughts were too unrealistic. Your Majesty’s kindness has made me too proud.”

Seeing Jang Yeong-sil’s self-reproach, Hyang smiled and consoled him.

“In my opinion, it’s not unrealistic at all. We simply lack too many things to realize it now. If our descendants maintain unbroken continuity[1], they will surely be able to make your ideas reality.”

“I can only pray it will be so. Then this humble one shall complete construction according to Your Majesty’s blueprint.”

“I’m counting on you.”

As Hyang was about to leave after finishing their conversation, he suddenly stopped and turned back to Jang Yeong-sil.

“I have something to ask you. Perhaps…”

After carefully considering Hyang’s subsequent words, Jang Yeong-sil soon nodded.

“I believe it would be possible.”

“Then proceed with that as well.”

“I shall obey your command.”

After concluding his meeting with Jang Yeong-sil and leaving, Hyang inwardly sighed.

Whew~ I barely saved him from disappearing after the palanquin incident, and he nearly caused an even bigger accident!

In the history before Hyang’s intervention, Jang Yeong-sil had vanished from history after taking responsibility for an accident where King Sejong’s palanquin broke. He had become a mysterious figure with even his birth and death records completely disappearing.

However, with Hyang’s intervention, Jang Yeong-sil had become a key figure in Area 51 and a celebrity known as one of the “Unfathomables”[2].

Yet if the wings built according to Jang Yeong-sil’s second plan caused an accident, it would be an even greater disaster than the palanquin incident.

Hyang’s thoughts suddenly took an unexpected turn.

What if he really is an alien and this was his aim?

Given Sejong’s or Hyang’s personality, if there were no casualties, it would surely end with just dismissal from office. Then he would again vanish beyond historical records.

Reaching this point in his thoughts, Hyang chuckled and shook his head.

“Nah~ That’s going too far.”

“Your Majesty? Do you have commands for us?”

Brought back to reality by the Chief Royal Secretary’s question after hearing Hyang’s self-talk, Hyang shook his head again and answered:

“Ah, no. Just had an absurd thought.”

One month later, a notice was posted at the unit operating the flying vessels.

“What’s this notice?”

“Recruiting volunteers?”

Soldiers crowded around to check the sudden recruitment notice.

• Area 51 has created a new device called “wings.” We need people to operate them. 

• Wings are flying devices like the flying vessels. 

• Recruiting volunteers from among flying vessel operators. 

• Welcome those with good eyesight, quick movements, strong physical strength, and great courage. 

• As this is a highly experimental device, it is extremely dangerous.

“Nah~ The flying vessels are dangerous, but they didn’t use the word ‘extremely.’ But here it says ‘extremely’? Better not go.”

“Right! My body is my fortune – if I become crippled, I’m the only one who loses!”

Yet despite such words, the soldiers couldn’t leave the notice.

The first reason was that these were soldiers who operated flying vessels. They knew better than anyone the allure of floating in the sky.

The second reason was the condition listed at the very end:

• Those who pass the test will receive double pay. In case of death or disability due to accidents, treatment will be equivalent to that of First-Class War Merit Recipients.

The pay was significant, but the “Merit Recipient” treatment was also important. First-Class War Merit Recipients were those who had built up achievements participating in both the “Defense of Uiju” and the “Battle of Liaoyang.”

Ultimately, within two days of the notice being posted, volunteers flooded in.

In the summer of Imperial Year 3 (1451).

After the rainy season ended, during the peak of heat, people gathered again along the Han River.

“What’s His Majesty showing us this time?”

“Something called wings, they say.”

“Wings? What’s that?”

“They say it’s a device that flies through the sky.”

“Isn’t that a flying vessel then?”

“They say it’s different from those.”

“Really?”

While curious citizens gathered and street vendors’ calls echoed from all directions, professors from Europe also gathered in one place, their eyes shining with excitement.

“‘Wings’… what should we call them?”

“We’ll have to see the actual thing first, won’t we?”

“The empire is good in every other way, but whenever they create something new, they only tell us the imperial name…”

“Isn’t it somewhat of an honor to determine the Latin name for these devices? By the way, the students still haven’t arrived…”

“I heard that almost none passed the first examination, so they’re taking it again.”

The professors all sighed at their colleague’s news.

“Whew~ We even sent letters asking them to carefully select candidates for the examination…”

“The empire’s standards are simply too high.”

Amid such conversations, loud music and citizens’ cheers began to erupt.

“His Imperial Majesty!”

“Long live!”

“Long live! Long live!”

Under the newly established protocol, citizens no longer had to prostrate themselves. Instead, they showed respect to the emperor through enthusiastic cheering.

This could be a show of respect, but it was also evidence of their strong loyalty to Hyang.

Hyang lightly raised his hand in response to the citizens’ cheers before ascending to the prepared platform.

As the court ministers took their seats behind Hyang, the demonstration began.

The subsequent demonstration of the wings shocked everyone except those involved.

Without gas chambers like those attached to flying vessels, these wings – with large biplane wings and propellers attached to a small leather vessel – took to the sky powered solely by human strength.

“It’s flying! It’s flying!”

“It flew! It flew!”

“Woooahhh!”

Amid people’s cheers, the wings rose about 20 jang (approximately 60 meters), circled once above Hyang’s head, then flew toward the downstream of the Han River.

After flying until out of sight, the wings returned after some time.

Through the skilled control of its operator, the wings’ flight ended with a smooth water landing on the Han River. Hyang rose from his seat and applauded vigorously.

“Magnificent! Truly magnificent!”

At Hyang’s praise, the two soldiers who had operated the wings prostrated themselves and exclaimed:

“We are overwhelmed by Your Majesty’s grace!”

That day, all the taverns and entertainment houses in Seoul recorded their highest sales.

Also, the professors from Europe wrote letters like mad.

“You must come see this immediately!”

“Flying through the sky!”

While many marveled at the wings’ flight, some did not.

These were Wan and the craftsmen he led.

“How deflating.”

“What have we been doing?”

While they had been fixated on flying vessels with steam engines, the Emperor and Jang Yeong-sil had created something entirely different.

As Wan and the craftsmen were feeling dejected, Hyang summoned them.