Trapped on the fourth day of Mars.

The Earth is still silent.

"Good morning...... Mr. Tang Yue. Mai Dong greeted Tang Yue weakly, his face was a little pale, and his hair was unkempt.

"Good morning." Tang Yue was wearing pants, wrapped in a blanket, sitting on a chair like an old monk meditating and participating in Zen, the table in front of him was a dinner plate and a water cup, today's breakfast was canned yellow peaches and compressed biscuits, plus one hundred milliliters of fresh water, canned yellow peaches were rich in water, so Tang Yue could bear it if he drank less water.

Today he also tried to wash with 190 milliliters of water, but unsurprisingly failed, and finally the toothpaste stuck to his front teeth.

It seems that two hundred milliliters is the bottom line.

"You don't look like you have much energy, didn't you sleep well last night?"

"Hungry." The girl stared straight at the food on Tang Yue's table, it seemed that the food was close at hand, as if she could reach out and touch it, and she couldn't wait to plunge into the screen.

"I'm so hungry—" Mai Dong's eyes were about to glow green, and she let out a desolate wail, "I—really—well—hungry—ah——! ”

Tang Yue was taken aback.

"I want to eat everything I see now." The girl hit her head on the camera, "Mr. Tang Yue, Mr. Cat, if your supplies are not sent over, I will go to gnaw on the space station......"

"I'll send it tomorrow! I'll send it tomorrow! ”

Tang Yue divided five by two, stuffed all the food into his mouth, then took a sip of water, jumped up and ran to wear the Mingguang armor.

Halfway through the run, Tang Yue turned around and shouted at the camera:

"Miss Mai Dong, don't gnaw on the space station, if you gnaw through the space station, it's all over!"

The old cat is on the ramp of the lander, inspecting the ascent rocket of the Eagle spacecraft.

The ascent rocket is the key to everything.

Whether the Eagle spacecraft can successfully re-enter orbit and rendezvous and dock with the joint space station depends on whether the ascent stage is powerful, the ascent stage of the lander has a total of two stages of rockets, the first stage is two Raptor 3C twin combustion chamber engines, a total of four nozzles, can provide more than 120 tons of thrust,

This stage of the engine is the workhorse, which is responsible for putting the lander into orbit.

The old cat meticulously checked the state of the rocket engine, it knew very well that this was a matter of human life, and the rocket of the descending stage would not be used anyway, and if it was broken, it would be broken, and it didn't matter how much it was tossed, but the rocket of the ascending stage would be the boat of life, the only hope for the little girl on the space station, and if something went wrong, it would be all over.

The Raptor 3C rocket used in the ascent stage and the Raptor 3D of the descending stage are products on the same line, but the models are different, the same engine produced by SpaceX, from the design structure to the assembly process is very similar, yesterday the old cat dismantled the engine of the descending stage, and the control system of the Raptor rocket was clearly figured out, just to prepare for today's inspection of the ascent stage.

The old cat was covered with a variety of tools, from ultrasonic flaw detectors to X-ray machines, and he examined the Eagle spacecraft inch by inch, like a conscientious doctor.

The main structure of the ascending stage of the lander is two huge propellant tanks, which hold tens of tons of liquid oxygen and methane as propellants for the engine.

Liquid oxygen and methane are both low-temperature propellants, the boiling point of liquid oxygen is only 90K, that is, minus 182 degrees Celsius, and the boiling point of methane is slightly higher, but it is only 110K, that is, minus 160 degrees Celsius, at room temperature and pressure, they will immediately boil and vaporize, how to store these low-temperature propellants for a long time is also a big problem, after all, the duration of Mars missions is often more than one or two years.

The problem of the preservation of liquid oxygen methane in orbit is easy to solve, because the temperature in space is extremely low, and as long as you are careful not to be exposed to direct sunlight, the temperature can basically be kept below the boiling point of the propellant.

The average temperature on Mars is about minus 60 degrees Celsius, and it can be as low as minus 80 degrees Celsius at night, but the temperature can rise to about zero degrees Celsius when there is sunshine in the summer.

This temperature is extremely low for humans, but it still does not keep oxygen and methane in a liquid state.

So the engineers had to make every effort to ensure that the temperature inside the tank was below the boiling point of the propellant, and the propellant tank of the Eagle spacecraft was a large aluminum alloy tank, but the inner wall of the tank was insulated with multiple layers of polyisocyanurate material, coupled with the powerful TVS system (Thermodynamic vent system), the TVS was like the refrigeration system of a refrigerator, which could keep the temperature inside the tank below the boiling point of the propellant.

Despite this, liquid oxygen and methane continue to evaporate, so the propellant on the Eagle spacecraft actually decreases over time, and normally the expedition should be on its way back before the amount of propellant drops to the red line.

"Old cat, how's your situation over there?"

Tang Yue pulled out the cart from the garage, and he was about to start carrying the supplies.

The old cat packed more than a dozen large boxes of food for Mai Dong, and these boxes together weighed a ton, and Tang Yue was also doing other work this afternoon, and moving the boxes would keep him busy until dark.

"Everything works."

The old cat's eyes are staring at the terminal display of the flaw detector, there can be no cracks in the main structure of the lander, porosity or desoldering, if there are cracks on the propellant tank, then it may lead to liquid oxygen or methane leakage, and the consequences are unimaginable.

The waveform shown on the flaw detector is stable, indicating that the reflected ultrasonic waves are very orderly, and the internal structure of the Eagle spacecraft is smooth and stable.

"Propellant tank OK."

The old cat put down the flaw detector and breathed a sigh of relief.

"No problem with the tank?" Tang Yue asked.

"There is no guarantee that there will be no problems at all." The old cat shook his head, "We can't disassemble the entire spaceship, under the current conditions, the parts I can inspect are actually quite limited, and I don't know if there are problems with other parts that I can't reach." ”

"What should I do?"

"You have to trust them." The old cat said, "Trust those people on the planet, believe that their designs will not go wrong." ”

"Damn." Tang Yue shook his head, "You want to make me believe that the most tasteless people in this world?" Do you know that there are a few bastards in Jiuquan who owe me two meals and don't pay me back, and if I hang on Mars, then they won't have to pay it back...... Oops, oops! ”

"What's wrong with you?" The old cat asked.

"Damn, I'm stuck! I'm stuck in the airlock doorway! ”

The old cat turned his head to look over, and sure enough, he saw a writhing ass outside the airlock cabin door.

"Come and do me a favor!" Tang Yue called for help, "Old cat! ”

The old cat put it on the gangway, walked over and kicked Tang Yue's ass hard.

"it!"