When everyone who boarded the airship got the instructions about the airship, Chiba understood why this airship could be used for high-altitude navigation - this airship did have the ability to easily enter the stratosphere.

The density of helium is 0.1786 grams per liter, while the density of air is 1.293 grams per liter. At an altitude of 14,000 meters, the air pressure is about 14,000 pascals, and the density of air is less than one-seventh that of ground air, which is almost the same as the density of helium. That is to say, if it is a normal conventional design rigid airship of about 5,000 meters, it can only rise to a height of about 14,000 meters at most through the Archimedes principle, that is, it cannot rise again. And considering that it is impossible for the airbag to fill every part of the airship, and it also needs to maintain a large amount of residual buoyancy to support the non-airbag area, it is very rare for this airship to reach the bottom of the stratosphere of about 12,000 meters in the extreme float.

But the supership, called the Pearl Tree, has a rather interesting design - its essence is a keel hoisted by airbags, which are soft airships in the airship's living quarters, but with an unusually large hard skeleton installed on the outside, which is protected by a layer of skin covering the soft and fragile airbags inside.

This design has two advantages.

The first is in terms of load: if you compare, the airship has such parts - the service function area where passengers are infested; air sacs for holding helium; power maintenance area for power support; Those passengers will not show up, and only infrequently used areas may need to be visited during maintenance. The rigid airship fills all of these areas with one standard atmosphere of air, while the Pearltree airship's non-normal areas are not filled with standard air pressure, only a rarefied atmosphere similar to the surrounding environment. An airbag equivalent to a pearl tree airship does not need to hold up air in an unusual area like a hard airship.

The second point is in terms of providing buoyancy (in fact, this is also the most important aspect): the rigid airship is limited by the fixed size and shape, so that the expansion of the airbag itself is limited to a certain range, while the airbag of the pearl tree airship can expand to a considerable extent with the surrounding air due to its completely ventilated external environment. With a little bit of physics calculations, it can be seen that this design allows the airbag to expand freely at a considerable height and continue to provide as much buoyancy as it would otherwise only be available at low altitudes. (Author: Helium with a mass of 4A expells air with a mass of 29A forever and creates buoyancy of 25A without volume limitation.) ）

And now, they are visiting this interesting design in the company of Jiroyoshi Suzuki and the housekeeper.

"Won't the airbag be destroyed?" In the rising elevator, Qian Yu asked the accompanying staff. "Could it be that some kind of protection has been added to the outside?"

"We have set up a cross air intake slot at the air intake of the airship, and if any tangible flying object hits inward from the air intake above the cross, it will only hit headlong into the foreign object storage slot below and be thrown out of the airship within a few minutes; Only air is fed into the airship through the true air intake grooves on the left and right sides of the cross. Of course, in addition to this cross air intake slot, there are many subsequent filter devices, which can effectively ensure the structural safety of the airbag.

"This huge skeleton structure is also reserved for the expansion of this airbag, right?" Conan asked, looking at the space inside the airship that was still empty after a large number of airbags were placed.

"yes," the staff nodded. "This skeleton reserves about 15 times the expansion space for these airbags, so that the airbags can be fully deployed, which also makes the maximum practical cruising altitude of the airship reach an unprecedented 14,000 meters - if the power system can be further improved to overcome the problem of thin air, the theoretical ceiling can even reach more than 18,000 meters after further modification in the future."

"At 246 meters long and 42.178 meters wide, both in length and width, it is exactly one meter more than the famous Hindenburg in those days." The Pearl Tree is the world's largest airship in every sense of the word! After the staff explained, Jiroji Suzuki said proudly.

"What is the approximate speed of this airship?" Qian Yu suddenly remembered something and asked.

If Chiba's observations and inferences are correct, the open structure of the Pearltree means that the thin atmosphere will be trapped by the shell of the Pearltree, which will increase the burden of the Pearltree's flight, which will have a considerable impact on the Pearltree's maneuverability.

"Uh......" The staff member fell into a rare hesitation and was about to say something, but was interrupted by Jiroji Suzuki.

"Speed is really not Pearltree's strong suit," says Jiroyoshi Suzuki, who is very calm. "After all, the airship itself is sold by its altitude, and we sacrificed a lot of speed for that – but a cruising speed of 115 kilometers per hour is enough for basic needs." (For comparison, the Hindenburg completed a round trip from Frankfurt, Germany, to Lakehurst, 6,250 kilometers away, in less than 99 hours in July 1936, with an average speed of more than 126 kilometers per hour.) The pearl tree chose an open layout for high-altitude performance, and the speed compromise was the price that had to be paid. ）

At this moment, the elevator has risen to the top. As the elevator doors opened, a gorgeous hall appeared in front of everyone's eyes. And the most conspicuous thing is a huge astronomical telescope.

"I have to admit that this hall has put a lot of thought into the designer, but it is all worth it." Jiroji Suzuki said proudly and led everyone out of the elevator. "After all, astronomical observations on the ground can't be as good as those on this side anyway."

"Is it such a big telescope...... "A look of surprise immediately appeared on Chiba's face - such a telescope weighs at least 10 tons, which is quite a burden for an airship the size of the Hindenburg."

(The Hindenburg's lift is 232 tons, while its dead weight is 220 tons, and the free buoyancy is only 12 tons.) ）

"yes, it's a big 16-ton guy," the staff member nodded. "When I first made the design drawings, I took a long time to make sure that this big guy wouldn't destroy the stability of the entire airship!"

"Are you the designer of this airship?" Maolilan realized it later.

"He's the chief designer," Jiroyoshi Suzuki said with a smile after glancing at the staff. Because this was the first time he had put it into practice, he had to stay on the airship so that he could quickly close the loopholes if something went wrong. After the big guy flies a few times, he will be able to enjoy a very comfortable vacation. ”