"The rest of the work is complicated, and I need to explain it to you in detail, Miss Mai Dong."

The old cat sat up straight, serious.

"Uh-huh, I'm listening, Mr. Cat." Mai Dong floated in front of the camera, looking like a good student listening carefully.

Tang Yue sat on the side and didn't know what to say, looking at the paper and pen on the table in a daze, he knew that there was no hope, it was completely impractical to use the Eagle spacecraft to return to Kunlun Station, whether it was to install a rocket engine or not, it was impossible for the lander to land successfully.

The Raptor 10D engine on the Orion II spacecraft was not designed for landing, and even the Orion II spacecraft itself could not be re-entered into the atmosphere, and its large and fragile propellant tanks could withstand low overloads, which could cause structural rupture when entering the atmosphere.

As for disassembling the rocket engine, it is even more wishful thinking, pulling a team of workers to drive a crane can still do it, and let a little girl Mai Dong copy the wrench, this is funny - the huge rocket engine nozzles on the Orion spacecraft are thicker than Mai Dong's whole person.

Whether it is himself or the old cat, the only answer that can be given to Mai Dong may be "There is no hope, girl, we can't do it".

"We still have hope."

Tang Yue was stunned, what?

He turned his head to make sure he heard correctly, what was the cat talking about? Is there any hope? What hope is there?

It had just completely rejected its plan, saying that it was completely out of line.

As soon as these words turned, how could there be hope again?

"Miss Mai Dong, you should have a basic understanding of the re-entry of the spacecraft, in general, it is a process of deceleration and landing, although the public likes to describe it as very complex and dangerous - of course it is extremely dangerous, but in essence it is a process of deceleration." The old cat said, "As long as we can successfully slow down, reduce the speed low enough...... Many problems will be solved. ”

"Uh-huh."

Tang Yue stared, seeing that the old cat didn't look like he was joking, could it really have any way?

"Slowing down takes power, and with enough power, we can solve seemingly unsolvable problems very simply and crudely."

"The engines on the Orion spacecraft?" Mai Dong asked.

The old cat nodded.

"Old cat, you just said that it is impractical to dismantle the engine!" Tang Yue shouted, "You yourself said that you have failed to simulate so many times, and none of them have been able to cross the height of 10,000 meters!" ”

"It's certainly not practical to dismantle the engine." The old cat rolled his eyes, "You've seen the rocket engine on the Orion, right?" Is that something that can be dismantled by a human being? Your thinking has fallen into a misunderstanding, Miss Mai Dong is indeed going to fly the Eagle spaceship, but the Eagle spaceship is not the key...... Think about Apollo 13 back then, was the space lifeboat that saved everyone's lives a command module? ”

Apollo 13?

Tang Yue was stunned, and then his scalp tingled.

His thinking did fall into a misunderstanding, the Eagle spacecraft was a lander, and Tang Yue subconsciously thought that the Eagle spacecraft was the key to everything.

Everything had to revolve around the Eagle lander, so he wanted to disassemble the engine and install it on the lander, so he thought hard about how to stabilize the lander's posture.

But what can really save Mai Dong's life...... It was never an Eagle ship!

"We're not dismantling rocket engines." The old cat whispered, "We're going to dismantle the Eagle lander, and Orion!" ”

Tang Yue suddenly understood, this is another really crazy plan, even crazier than the last time he drove the space station to catch the lander - unable to land successfully, the root cause is insufficient thrust, if the thrust is insufficient, then the power will be increased, one engine cannot meet their needs, so all nine engines will be used!

I really don't know if this idea is inherited from the Falcon Heavy of the year, or the N1.

If it was the former, then Tang Yue would still be at ease.

If it's the latter......

"You said that the Orion spacecraft would crash when it enters the atmosphere!" Tang Yue grabbed the old cat.

"That's right." The old cat's expression was grim, "What we want is for it to crash!" ”

Robots are robots, and being crazy is not human at all.

Later the old cat said:

Ninety-nine percent of the problems faced by mankind in space engineering are caused by insufficient power, and as long as the power is sufficient, these are not a problem.

The last one percent is the same as usual.

·

·

·

"We all know that if an object is dropped at a high altitude on Earth, then it will move in a state close to free fall, but it will not be truly free fall."

"Because of air resistance?" Mai Dong said.

"Yes, this object will keep accelerating, but it won't go on forever." The old cat said, "At a certain point when it falls, gravity and air resistance will balance, and the next thing is to fall at a constant speed." ”

Mai Dong and Tang Yue both nodded, this is very understandable, the content of high school physics class.

"This is affected by the density of the air, and there is a physical word called 'ballistic coefficient', and the ballistic coefficient in the Martian atmosphere is very low, which means that it is difficult for the atmosphere to give you enough resistance to reach equilibrium." "If we throw the unpowered Eagle spacecraft down, it will slow down very slowly, and when the altitude drops to 40,000 meters, it will still exceed fifteen times the speed of sound, and the surface temperature will rise to two thousand degrees Celsius – that's why we need thermal insulation tiles." ”

"In the last century and the beginning of this century, many Mars rovers failed because of this, and the speed was too fast to descend."

The old cat shrugged.

The most typical example of the Mars probe that crashed during the landing was ESA's Hound 2, the poor lander that is still in the wilderness.

"The normal landing process of the lander is like this: it begins to enter the atmosphere at an altitude of one hundred and twenty-five kilometers, and at this time its speed is about five kilometers per second." The old cat once again showed the two of them with a pen, it raised the pen in its hand high, and then plunged down, "After eighty-five seconds, open the deceleration cushion and perform the first deceleration, in which eighty-five seconds its altitude will drop ninety kilometers and survive the worst heat barrier." ”

"The deceleration air cushion will reduce the speed of the Eagle spacecraft to less than twice the speed of sound, which is an acceptable number of Mach numbers for parachuting, and at an altitude of 10,000 meters, the lander will open a ring parasail with a diameter of 30 meters." The old cat opened his paw at the end of the pen and signaled the parachute, "The parachute can reduce the speed of the Eagle spacecraft below the speed of sound until the altitude of the lander is reduced to less than a thousand meters, then it abandons the parachute, turns on the rocket engine to adjust the attitude, reverses the thrust and decelerates, and finally lands vertically." ”

The old cat finally slowly pestled the pen vertically on the table.

These Mai Dong and Tang Yue also knew that as early as the training before the mission, the people on the ground had explained in detail the working principle of the spacecraft.

The old cat repeated it again today.

"Why is this process so complicated?" The old cat asked, "Why is it so complicated?" ”

Before Mai Dong and Tang Yue could speak, the old cat answered by himself.

"Because we don't have enough power, we don't have enough power to use the rocket engine for thrust reverser from start to finish, and the efficiency of chemical rockets is too low." Lao Mao said, "Most of the thrust of the engine is pushing itself, thousands of tons of mass are fuel, and the remaining fraction can give the load." ”

"During a normal landing, it would be impractical to use rocket thrust reverser throughout the entire process, so the Eagle spacecraft would have to fill the cargo hold and command compartment with propellant, and the lander would become a flying fuel tank." "But that's normal, we're going to have an abnormal landing...... We don't care about efficiency, we don't care about cost, we don't care about hundreds of tons of fuel, we only need that fraction! ”

The old cat raised his paws, pointed to Mai Dong on the screen, and said word by word:

"Sixty kilograms!"