Early the next morning, the old cat drove the Martian stray dog out and stopped at the edge of the Eagle spacecraft.

Tang Yue stood on the sand wearing Mingguang armor, looking up at the descending stage of the tall lander, although the upper upgrade had been launched, the Eagle spacecraft was still the tallest and most conspicuous object in the Kunlun station.

The original white paint was burned black by the tail flame of the rocket engine, Tang Yue walked around the lander several times, the ground under his feet was covered with a layer of gravel, the sand is brown-red, which shows that they are rich in hematite, and under the sand is hard basalt, Mars is a near-dead planet, geological activity has been silent for a long time, these ancient rocks were formed three billion years ago, they gradually broke under the long wind and sun, turned into sand and then turned into dust.

The old cat pushed the car door open and jumped out of the cab.

Tang Yue lightly tapped the hard shell of the lander, "How much propellant is there in this?" ”

"There should still be a part left, and the propellant of the downgrade engine is redundant, and there is a high probability that it has not burned out." The old cat crossed his waist and looked up at the Eagle spaceship, "But how many there are, you have to open this shell to know." ”

The Raptor 3C rocket engine of the descending stage of the Eagle spacecraft uses methane and liquid oxygen as propellants, and junior high school students know that the product of methane and oxygen combustion is carbon dioxide and water, and one mole of methane and two moles of oxygen can react to produce one mole of carbon dioxide and two moles of water, which is an excellent source of fresh water.

This is Tang Yue's plan, using the propellants in the lander and relying on their reaction to get fresh water.

The old cat returned to Kunlun Station and came back with a toolbox.

There was no gangway for the descendant, and the old cat had to use the Martian Stray Dog as a stepping stone, and he climbed onto the roof of the rover and approached the shell of the Eagle spacecraft, full of wrenches and taper screwdrivers.

Although it is easy to say, it is not easy to get the methane and liquid oxygen sealed in the propellant tank, they cannot smash through the propellant tank to release the fuel, then the methane and liquid oxygen will leak out in a short time, and the only opening that can be drained is the pressure relief valve - the liquid methane and liquid oxygen in the tank are constantly evaporating, and if there is no pressure relief valve, the air pressure in the tank will be higher than the danger line.

In order to successfully utilize the fuel in the lander, methane and oxygen must be slowly and safely drawn out of the tank and finally mixed combustion.

For Lao Mao and Tang Yue, this is a very complicated project, they first need to disassemble the fairing of the lander.

This kind of delicate work is inconvenient for Tang Yue to do with Mingguang armor, so he can only be helped by the old cat.

The old cat held a screwdriver in his mouth, opened the access port of the lander, squinted his eyes, and found the pressure gauge.

"How?" Tang Yue asked at the bottom, "How much propellant is left?" ”

"Hmm...... It's a little less than I expected, probably because of the continuous evaporation of the propellant, and we still have about two hundred kilograms of methane. The old cat frowned, "With so much methane, it can only produce four hundred and fifty kilograms of water at most, but so much water should be enough to grow tomatoes and carrots." ”

"Can these four hundred and fifty kilograms of water be directly replenished into the water tank?" Tang Yue asked.

"Nope." The old cat shook his head, "This water can't be drunk directly until it's been treated and purified...... But how do you collect this water? Methane and liquid oxygen are burned to produce water vapor. ”

"Don't worry, I'll take care of the collection."

Tang Yue was confident.

At two o'clock in the afternoon, the old cat removed the fairing of the lander, so that the entire propellant tank and rocket engine were exposed, and then they began an intensive transformation plan, Tang Yue found two long rubber tubes and a glass Y-shaped tube from Kunlun Station, these bits and pieces of gadgets were used by the previous scientific expedition team members for experiments, and now they were all put away by Tang Yue.

The old cat put rubber tubes on the pressure relief valve of the propellant tank, one to transport methane and the other to transport oxygen, and tied it tightly with iron wire to make sure that it would not cause leakage.

“OK！” The old cat stood on the roof of the Martian stray dog and waved his paws.

Tang Yue stood at the bottom, picked up two rubber tubes, put them on the two manifolds of the Y-shaped glass tube, and tightened them with iron wire, when the methane and oxygen would be mixed and burned in this glass tube, producing carbon dioxide and water vapor.

Tang Yue felt like he was back in high school doing chemistry experiments.

“OK！” Tang Yue raised his hand and signaled, "Old cat, you can come and try!" ”

The old cat nodded, grabbed the wrench, slowly twisted the throttle valve, one mole of methane can react with two moles of oxygen, in order to avoid the waste of propellant, to ensure the full combustion of methane, the old cat must carefully adjust the flow rate of fuel and oxidizer, it stared at the pressure gauge, the expression was very solemn.

"Attention ——!" The old cat reminded, "I opened the valve!" ”

Tang Yue took out the arc igniter, leaned in front of the glass tube, snapped, and lit methane.

A small pale yellow flame fluttered at the end of the glass tube, and the high-temperature water vapor touched the cold atmosphere outside, and immediately condensed into small droplets, turning into a curling white mist.

The source of fresh water has fallen.

"Old cat! It worked! ”

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The old cat and Tang Yue stood on the sand, and the two looked down at the glass tube on the ground.

After many experiments, the two finally proved that the methane inside the lander could be safely burned - without a sudden explosion and sending them back home.

The next question is how to efficiently collect the water vapor from combustion.

"You said you had a way to collect the water vapor." The old cat said, "What way?" I'll tell you in advance that we don't have condenser tubes, and the big lab kits are either broken or all taken away, and we can't even find a glass tube long enough to make a condenser tube. ”

"We don't use condenser tubes, which are too slow." Tang Yue shook his head, "Use such a thin glass tube to collect four hundred kilograms of water, we have to collect it until next year." ”

Tang Yue really didn't plan to use a conventional condenser tube to collect fresh water, this method is very commonly used in the laboratory, but it is inconvenient on the surface of Mars with wind and sand, the glass is too fragile, the long glass tube is even more fragile, and the collection speed of the condenser tube is too slow, if the speed is accelerated, it is easy to cause waste.

"And what method are you going to use?" The old cat asked.

Tang Yue turned around and returned to the garage, and a few minutes later, he came back with a long-handled shovel in one hand.

Tang Yue threw a shovel to the old cat.

The old cat held the shovel and looked at it for a long time, looking dazed.

"Shovel?"

Using a shovel to collect fresh water?

"Yes!" Tang Yue nodded and waved the shovel in his hand, "Let's use the shovel to collect fresh water!" ”