While continuing his work on the spaceship, Jin decided to start with the relay stations, as he already had a clear plan for their design.
The core concept involved a series of relays using the manacam.
Each unit would receive an incoming transmission and retransmit it directly without converting it back into audio. However, since simply relaying the signal would only incrementally extend the range, he planned to use directional communication to improve efficiency.
Because these retransmissions only needed to travel in a fixed direction—specifically, toward Hourai Island—he could focus the signal into a beam. This concentration should significantly increase the transmission distance.
That was Jin’s basic concept. Determining how to locate Hourai Island and managing attitude control were challenges to be solved next.
"Conversely, the return signal should just be pointed back toward the source of the incoming transmission."
Developing new magic tools like this was enjoyable, especially since he wasn't building a weapon of destruction.
The direction of Hourai Island—or rather, the planet Ars—could be calculated by sight if they were close enough, or by the position of the stars if they were far away. As for attitude control, he already had a proven track record with the Watchers.
Within about three hours, Jin had completed two prototypes and finished their communication tests.
"As I thought, the carrier waves travel in a straight line..."
As a test, he tried to contact Sky 34, an Air Force golem stationed on the far side of the planet. It appeared the free ether waves were penetrating directly through the planet’s core.
"I suppose the free ether contained within the ground and the planet itself acts as the medium."
Jin proposed the hypothesis to himself.
『My Lord, that possibility is high,』 Laojun replied.
In any case, the system seemed practical. Jin left the production of the flight-ready units to Laojun and the Smiths and moved on to his next project.
"Father, you finished those quite quickly, didn't you?" Reiko remarked.
"Yeah. It's better for one's peace of mind to start with the easier tasks."
Even during exams, people often spent too much time on difficult problems and ran out of time for the rest. Jin’s philosophy was always to solve the easy ones first. Of course, one had to be careful; if a seemingly easy problem turned out to be difficult and you abandoned it for another that was also hard, it became a total waste of time.
Jin found himself recalling the test-taking advice his classmates from his part-time high school days used to share.
"That is true. It feels good to see the visible results of completing a task," Reiko said, picking up on his line of thought.
"Yeah, exactly, Reiko."
Jin smiled at her words. Then, he announced his next objective.
"Next up is the missile."
This was a pure weapon of destruction. However, as No. 700672 had pointed out, if they encountered obstacles in the path of their spaceship, failing to use such weapons without hesitation could mean their own destruction.
"When it comes to explosions, the first thing that comes to mind is..."
"A Mana Explosion, isn't it?" Reiko finished his sentence for him.
"Right. Which means a mana bomb."
A mana bomb was a device that utilized the Mana Explosion spell.
"I just need to use that as the warhead."
Because of this, the weapon was relatively simple to design. It was less a guided missile and more a rocket or a high-explosive shell.
The real issue was launching a projectile from the pressurized interior of the ship into the vacuum of outer space. The shell would have to cross that boundary eventually, and Jin wanted to ensure they didn't lose any air in the process.
"Father, why not simply store the ordnance in a vacuum section from the beginning?"
"Hmm, but then we wouldn't be able to restock them manually, right?"
"There is no issue; golems do not breathe."
"Ah, right..."
Realizing he could simply leave the reloading to the golems, Jin quickly assembled a prototype shell.
"Now, I need to know its exact yield."
Since these were intended to destroy meteorites and space dust, it would be dangerous if the power was insufficient, yet wasteful if it was excessive. He used a single one-gram magi-stone as the standard for the explosive charge. By Jin's estimation, it should be capable of shattering a rock about ten meters wide.
"Father, why don't we use force generators to float a rock and use it for target practice?"
"I suppose that's the best way..."
Since it would be a disaster if the weapon failed in an emergency, he took Reiko's suggestion and prepared for an experiment.
Avoiding Tatsumi Bay where the fish pens were located, they headed to the north side of Hourai Island. There, he had the Mermaid unit use force generators to suspend a large boulder fifty meters above the sea.
The plan was for Reiko to take a shot at it.
"Reiko, I only have one prototype, so don't miss. The launch velocity only needs to be the bare minimum."
"Yes, Father. Leave it to me."
Reiko loaded the shell into her favorite magi-cannon and took aim.
"Laojun, are the recording preparations ready?"
『Yes, My Lord.』
Jin intended to record the event to use the data for future refinements.
"Ready? Three, two, one... Fire!"
Launched at only about three percent output—nowhere near its full capacity—the shell flew at subsonic speed and struck the boulder with perfect accuracy. Immediately upon impact, the magi-sequence triggered the Mana Explosion.
The detonation followed instantly.
"Oh, success!"
The ten-meter granite boulder was obliterated, reduced to over a hundred scattered fragments.
"The yield is exactly as calculated, too."
Jin decided that, using this as a baseline, he should create several tiers of shells categorized by their destructive power.
Then, Laojun offered a suggestion.
『My Lord, instead of going through the trouble of firing them with a magi-cannon, perhaps we could simply deploy them to the target via a transporter?』
"Ah, I see. If we do that, we don't even have to worry about airlocks."
The only potential problem was the control brain required to transport objects accurately. With the current transporters, only Laojun possessed the processing power to fully control them, as a tiny error at the point of origin would result in a massive deviation at the destination.
『I believe it will be fine as long as the spaceship's control brain is sufficiently high-performance.』
Since the targets would generally be within visible range, it likely wouldn't require processing power on Laojun's level.
"Still, the position measurement needs to be as accurate as possible."
Jin figured that if he placed sensors at both poles of the 300-meter-diameter spherical spaceship, he could achieve a high degree of precision.
"Ah, right. I should link this with the radar system."
This led Jin to begin considering the object radar No. 700672 had recommended.
"Hmm, how did radar work again...?"
You send out radio waves, then catch the ones that bounce back... Jin muttered to himself, lost in thought.
"Father, please stop for today and have dinner."
Before he knew it, the sky was fading into dusk. Knowing that nothing good came from overworking himself, Jin obediently followed Reiko's advice.
"Jin-nii, welcome back."
"Hey, Elsa."
When Jin returned to the house, he found that Elsa had also come back from Kaina Village.
"Dinner is ready, so go wash your hands."
"Yeah, got it."
As he headed to the washroom, Jin thought to himself that this kind of life was quite nice, too.