After a short break for lunch, Goh and Rubina go to the workshop. Meltze continues to teach Elsa how to behave.

"Well, let's build an engine.

"Yes. We'll make one for this plane: ......

Then Jin, who was accompanying us, says something.

"You'd better make it with standardization in mind.

"Oh, in consideration of future commercialization.

"...... is a pain in the ass."

"Rubina, I don't say that. This is also the role of an engineer."

"Yes, ......."

After such an exchange, Jin returned to the house because he didn't want to interfere too much.

Goh and Rubina worked out the specifications of the engine.

"To fit this plane, ...... it should be about 50 centimeters in diameter, right?"

"Well, considering the number of ......2 engines and the power, I think it might be possible to make it a little smaller.

"Well, let's try 30 centimeters.

"About that size, I guess. That's probably about right.

"That's right, that's what standardization is all about."

The <>, although less powerful than the <>, does not have thrust that is easy for humans to handle.

The project to make it into a general-purpose engine still has a long way to go.

"First, let's make a basic model."

"Right."

The two engineers worked together to create an engine of with a familiar hand.

They then set about testing the engine on the test bench.

Ruby and Ames, the five-colored golem maids, continue to provide support.

"We'll start with a very low ...... output and test it."

"Yes, it's dangerous to increase the power too quickly. ......"

"......We should consult Jin-sama for such tests."

Goh and Rubina consulted with each other as they prepared for the test.

If we are going to do a full-scale full-power test, it would be dangerous to do it here, so we will borrow facilities on Horai Island.

When Jin later hears about this from the golem maid, he thinks that this is the right decision.

He was pleased to see how the two had grown.

Regardless, the < that the two had built was working well.

At 10% of its operation, it was producing 10 kN (=1020 At this rate, the thrust at full power is 10 kN (=1020 kgf).

At this rate, if the thrust at full power is 100 kN, it will be about twice that of a modern earth jet engine (about 50 kN at full power). At this rate, if it can produce 100 kN of thrust at full power, it can be said to have about twice the performance of a modern earth jet engine (about 50 kN at full power).

"I don't think our test bench can hold much more than this.

"I guess so. We don't want any accidents during development, so let's not overdo it.

I agree.

So, the engine test is not finished at ......, and the data is taken at less than 10% output.

"Ease of use at low output is very important, isn't it?"

"That's true. So, if we take the time to collect control data, it will be useful later.

"Oh, so we can use the same data if the specifications are the same then, right?

"That's true."

"Jin-sama's advice also meant this: ......"

The two of them took another step up the ladder as engineers.

* * * *

"We spent the whole afternoon at ....... You were taking data."

Yes.

And you want to borrow the test bench at Horaijima tomorrow?

"Yes."

Hearing those words, Jin nodded his head in satisfaction.

"Of course, of course. The two of you who have been working so hard to create ...... especially Rubina, you've grown up."

"Heh heh, really?"

"Goh also realized the importance of basic data and the meaning of standardization.

"Thank you very much."

Both of them smile happily after receiving Jin's praise. Meltze saw this and smiled as well.

"So, how was your day, Mel-chan?

"Me?

"Yes. You learned a lot from Erza-sama, didn't you?

"Yes. ......, um... ......."

M?rze looked very contented as she recounted the day's events.

* * * *

The next day, the 10th, we rented a test bench at Horai Island.

"I knew this place was great!"

"Don't they have similar facilities on Onogoro Island?"

"Yes, at Dr. Marikka's."

Onogoro Island doesn't seem to have that many large test benches.

"Come on, let's test it!"

The engine is secured and ready for startup.

Support is provided by <7.

Jin does not help them directly, but watches them work together.

He nodded inwardly as he watched them fix the engine firmly and check it again and again.

"First, start slowly using yesterday's data.

"Yes, sir."

Goh is operating the control unit under Rubina's direction.

This is a preliminary step for the generalization of the control system, so that it is as easy to operate as possible, and they are building the control system by feeling it themselves.

"Five percent of the mana input."

"...... thrust is 450 kg."

This is done because it is easier to measure in kilograms.

"10 percent mana input."

Thrust is 1100 kg.

I knew it. It's not perfectly proportional.

"Yes, it is. How about from here on up?　...... 11 percent mana input.

Thrust is ......1205 kg.

"12 percent mana input."

Thrust is 1310 kilograms.

"13 percent mana input."

1,420 kilograms of thrust.

Oh, it's coming along nicely.

Yes, it is.

Goh and Rubina thought that by repeating these measurements and adjusting the control system to smoothly change the thrust when the mana was adjusted with the throttle, they would be able to create an aircraft that was easy to control.

After a full day of data collection, both Goh and Rubina were very satisfied that they could create a very easy-to-use configuration.