The hot air balloons at Zhenyuan Escort Agency are basically black, and with curtains underneath, the enemies outside the city cannot see them at all.

The hot air balloon floated out of Yuguan City silently.

Now is the season when the north wind is prevalent. After the hot air balloon takes off, it flies south along the wind.

However, there was only one chance of sneak attack. In order to maximize the value, Mr. Liu Tie and Tian agreed that Dongman was the first target, so that the hot air balloon could kill Dongman commander first, or burn the other party's grain warehouse.

So after the hot air balloon flew out of Yuguan City, even if it flew over the Jin and Barbarian coalition forces, it did not launch an attack, but continued to rise to look for other wind directions.

The wind directions are different at different heights at the same location.

However, when the hot air balloon rose to nearly a thousand feet, there was still no suitable wind direction.

There are two pilots on the hot air balloon, one of which is responsible for mastering the stove and controlling the lifting and lowering of the hot air balloon, and is considered the main controller.

The other one is responsible for preparing hot oil and some auxiliary work, and is considered a deputy.

The deputy lifted the curtain and looked out, his brows frowned.

With the current technology of Xihewan, it is impossible to make instruments for measuring height, so pilots usually use ropes and visual inspections to determine height.

On the outside of the hanging basket, there is a plate of thin rope with heavy objects hanging on it. The rope has a scale. As long as you put the rope down, you will roughly know the current flight altitude.

Now they are flying above the enemy's heads, and they will definitely not be able to use ropes to measure, so they can only use visual inspection.

This is also the basic skill of all pilots.

Although they couldn't see clearly at night, their deputy judged through the bonfire on the ground that their current flight altitude was at least more than nine hundred feet.

War is the best catalyst for industrial development.

Jin Feng's power has developed so rapidly that hot air balloons and grenades are the top priority, so hot air balloons and grenade technologies are also the fastest-growing ones.

At the beginning, Jin Feng needed to experiment and prepare gunpowder by himself, and then hand it over to the death row prisoner for production.

Later, Wei Laosan rebelled and blew up the gunpowder warehouse with a hot air balloon. Almost all the dead prisoners recruited from Xichuan City were killed.

When rebuilding the gunpowder workshop, Jin Feng arranged for the Man Warehouse to use assembly line operation method, and divided the process of making gunpowder into several steps. Each workshop was only responsible for the production of one of the raw materials.

After all the raw materials are processed, they are sent to the mixing workshop for the last step of production.

In this way, even if someone rebels, he only knows the production process, but not the complete process.

And the production speed is many times faster than before.

Gunpowder is a very dangerous thing. Tang Xiaobei was afraid of the danger of Jin Feng, so he joined forces with Guan Xiaorou and refused to agree to Jin Feng continuing to test gunpowder.

To this end, Tang Xiaobei also spent a lot of money to recruit a group of people and set up an explosives laboratory in the old forest in the back mountain to test gunpowder.

Jin Feng was so troubled by them that he had no choice but to agree to hand over the job to the people recruited by Tang Xiaobei.

Jin Feng didn't have much expectations for these people.

In his opinion, these people were almost too poor to go, so they were willing to risk being bombed to participate in this life-long job. They had no literacy, and they didn't understand the principle of gunpowder. They could be worthy of it.

What new explosives came out?

But Jin Feng underestimated the power of money.

When Tang Xiaobei recruited them, he said that whoever can study the more powerful gunpowder ratio or other methods to make grenades can get a large reward.

In order to get this reward, these people really prepared a new explosive in the third month of the laboratory's establishment.

Although the power is not much higher than Jin Feng's previous matching method, it means that these people have really understood the principle of gunpowder.

Jin Feng himself was not very interested in explosives, so he simply stopped caring about it.

He believed that with Tang Xiaobei's prudence, there was no need to worry about these people leaking the secrets.

As for how Tang Xiaobei formulated the confidentiality process, Jin Feng was too lazy to ask about it.

The same is true for the hot air balloon workshop. Now there is no need for Jin Feng to take care of it, and there is a dedicated person to take charge.

Facts have proved that once the seeds of knowledge are sown, they will thrive.

Although Jin Feng rarely cares about hot air balloons, because of the war needs, Zhang Liang attached great importance to hot air balloons before the airship appeared.

After such a long time of development, Xihewan's technology for producing hot air balloons has become very mature.

The Eagles and the others first experimented with hot air balloons, with an extreme height of only three hundred feet, and later they slowly began to rise to four hundred feet and five hundred feet.

Until now, the hot air balloons produced in Xihewan can fly up to a thousand feet.

In fact, if you really want to fly upwards, the hot air balloon can still fly, but once you reach a height of thousands of meters, not only will the temperature drop rapidly, but the oxygen content in the air will also drop rapidly.

At that time, the pilot will develop hypoxia syndrome.

In order to prevent accidents from pilots, Jin Feng issued an order to the flight team, stipulating that except for tests, hot air balloons can only fly up to one thousand feet. If someone flies up further, they will be disqualified from flying.

Even if the test is done, it must be reported.

The flying height of this hot air balloon is probably more than one thousand feet now.

When he found that the main controller was still flying up, the deputy hesitated for a moment and reminded him: "Brother Wen, we are flying too high, it seems to have exceeded one thousand feet... The gentleman said, we can't fly that high...

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But before he finished speaking, he was interrupted by the main controller: "Who said it was a thousand feet? I think it was only less than five hundred feet!"

Upon hearing this, the deputy glanced at the main controller's hand speechlessly, but he didn't say anything else.

The main controller poured a scoop of hot oil into the stove, and the hot air balloon rose faster.

When both pilots felt a little breathless, they finally found the right wind direction.

The hot air balloon sways toward the north.

At this time, a smile finally appeared on the face of the main controller.

The time Haidongqing attacked the airship, the two of them happened to take a break and did not get on the airship.

As a result, their companions never came back after that day.

Although the main controller knew that this was not his fault, whenever the night was late, he would always think of his comrades who had trained with him and felt like a deserter.

Now that he can finally avenge his comrades!

The hot air balloon was very fast. After more than ten minutes, it flew over Yuguan City again, entered the grassland, and successfully found the camp of the Dongman people.

But when they arrived above the camp, they were stunned.

The Dongman's camp was too big and it was too dark.

Even though there was a telescope and the flight altitude was lowered, the two pilots still couldn't find where the main account of the Dongman was.
Chapter completed!