"Yoo-hoo!"

Rubina's spirited voice echoed through the workshop.

She was sulking a little because Jin had somehow developed the , a reproduction of an ancient technology, all by himself.

He said that he was an adult and would not be offended by such things. .......

However, according to his grandmother, Amanda, he is still a child.

Aside from that, Rubina and Goh worked together to build a prototype engine.

It is a cylinder about 5 cm in diameter and 10 cm long, hemispherical at one end and shaped like a <>.

It is like a basic rocket engine.

"So, where would you like to engrave the <> formula here?"

"That's difficult. ...... I think it would be better to experiment and decide the best position here."

There are two possible locations to carve.

One is the hemispherical tip.

The other is the inner circumference of the cylinder. Which side of the inner circumference is best will also be decided by experimentation.

The results showed that none of them were good enough.

"Well, I thought it would have a little more power..." "Yeah..." "I know..." "I know..." "I know..." "I know..."

"Well, I thought it would have a little more power. ......I guess it's not the combustion chamber of the engine ...... but ......<>.... I'd like to write in the center there."

"Goh is right. That area seems to be the most efficient."

"...... I guess we have to draw in a spherical <> and support it with three or four support girders."

"Yes, let's try ......."

The first experiment did not produce the results they had hoped for, and the two were a little less excited, but they still proceeded with their work quickly.

As Elsa watches over them, she smiles at the ups and downs of their moods, thinking that they are still children after all.

Under Elsa's watchful eye, they built the second prototype engine.

And then they conducted an experiment.

"...... We did it!"

"It's more powerful than the last one.

"I'm sure it will be better with some adjustments."

"Yeah."

So Elsa decides to offer a little advice.

"The inside?　I think the air flow would be smoother if the jet side was a cone instead of a sphere.

"Oh, I see!　Thank you, Miss Elsa!

I'll try it right away.

"Good luck."

With Erza's advice, the two managed to shape the by lunchtime that day.

* * * * *

After lunch, Jin finished writing the draft of the report and checked the progress of the two.

Rubina gives her report proudly.

"Well, you are doing quite well.

"We're going to do a detailed output test this afternoon!"

"Good, I'll be there."

"Yes, watch me, Jin-sama!"

Jin and his team moved to the wind tunnel room and immediately started the experiment.

"Oh, it's looking good, isn't it?

Isn't it?

"I am honored by your praise!"

From Jin's point of view, the prototype engine created by Goh and Rubina was a good one.

"If I had to give it a grade, I would give it a 95.

"That seems like a very high score, but where's the minus?"

"Did you name the inside ......<>?　The cross-sectional shape of the support structure that holds it up is round."

"Oh ......!　I should have streamlined the cross section there too!"

"That's what I meant. The other thing is the surface roughness inside the engine. It's a little rough for a prototype, don't you think?"

"Yes, that's right. It's a prototype, so it should impede air flow as little as possible.

"That's all I need to know. If you look at the whole thing, it passes without question.

"Yes!"

Rubina jumps up and down and Goh looks happy.

"Now let's fly the model with this thing on it, shall we?"

"I'll do it!　<!"

Rubina is very excited by Jin's praise.

Rubina and Goh go to the workshop together. They immediately start to build the aircraft.

"Oh, wait!"

Meltze followed them.

Even though she can't use engineering magic, she seems to enjoy just looking at them.

Rubina and the others are building the series, which will probably be a delta wing. I expect that they will be quite good this time, too.

Jin is also looking forward to it.

"Thank you, Elsa.

"Yes."

Jin then thanked Elsa for supervising them.

"After we take a break, I think I'll try my hand at building a new Magi rocket engine.

"That's just like my brother Jin."

The two returned to the house for an early tea break.

Daikie, Cocona, and Amanda were with them.

The tea was sencha green tea and sweet potato dumplings.

"Jin-sama, is she all right?

Amanda looks a little worried, but Jin answers with a smile.

Don't worry about Rubina. She is developing into a good engineer. And while she's here, I hope she'll become a good daughter as well.

"That's what worries me the most. ...... She's a bit of a brat, you know."

"So she can stay here and meet all kinds of people."

"Is it okay if I stay here ......?"

"Sure. Hey, Daikki, Cocona.

"Of course. It's so much fun to have you here every day, isn't it, honey?

"Yes, it is. Rubina and Merce have become good friends of Goh.

Daikie and Cocona both smiled softly, knowing that they were saying these words from the heart.

"Thank you. ......"

With that, Amanda bailed.

Amanda bailed out.

"Well, then, I'll be on my way.

He thought of going to the workshop in the basement of Reuthert, but it was too cramped there, so he moved to Horai Island for a while.

I will be back before nightfall in Loisart, and I have asked the old man to contact me.

"Father, where would you like to start?"

"Well, first I will make my own prototype.

Goh and Rubina had already worked out the theory to some extent, so there would be no problem.

A cylinder with a diameter of 5 cm, a length of 10 cm, and a hemispherical shape at one end is made. So far, we are the same as Goh and his colleagues.

"Goh and the others made a , but I will not.

In the first place, when you release a <>, you do not release it from the palm of your hand.

In most cases, the <> as a phenomenon occurs from a place about 5cm away from the palm of your hand ......, the source of mana. The phenomenon <> occurs from a place about 5cm away from the source of mana .

In other words, there are parameters that determine the place and direction of occurrence.

It would be unreasonable to ask such things of two people who are not <>.

That is why Jin did not mention this point earlier.

"Well, let's see how much propulsive force we can get out of this.

After building the prototype in 5 minutes, Jin sets it on the test bench and starts to measure the propulsive force.

"Okay, <>."

The prototype engine spits out wind.

"Okay. I knew it wasn't an explosion, so the force generation is slow.

Jin continues to gradually increase the power output.

Now comes the test of strength: .......