"The following work is very complicated. I need to explain it to you in detail, Miss Mai Dong."
Old Cat sat up straight and looked serious.
"Yes, yes. I'm listening, Mr. Cat." Mai Dong floated in front of the camera, looking like a good student who was listening attentively.
Tang Yue sat on the side, not knowing what to say. He stared at the pen and paper on the table in a daze. He knew that there was no hope. Using the Eagle to return to Kunlun Station was completely unrealistic. Whether or not the rocket engine was installed, the lander could not successfully land.
The Raptor 10D engine on the Orion II spacecraft was not designed for landing. Even the Orion II spacecraft itself could not re-enter the atmosphere. The huge and fragile propellant tanks on its body could not withstand the overload, and re-entry into the atmosphere would cause the structure to rupture.
As for dismantling the rocket engine, it was even more wishful thinking. It could be done with a team of workers driving a crane, but to let a young girl like Mai Dong hold a wrench was a joke. The huge rocket engine nozzles on Orion were thicker than Mai Dong's entire body.
Whether it was himself or Old Cat, the only answer they could give Mai Dong was, "There's no hope, Miss. We can't do it."
"We still have hope."
Tang Yue was stunned. What?
He turned his head to make sure that he had not heard wrongly. What was the cat saying?
There was still hope?
What hope was there?
It had just completely rejected his plan and said that there was no way out.
Now, the topic had changed. How could there be hope?
"Miss Mai Dong, you should have a basic understanding of a spacecraft re-entry into the atmosphere. In general, it is a process of deceleration and landing. Although the public likes to describe it as very complicated and dangerous — of course, it is indeed extremely dangerous — in essence, it is a process of deceleration."
Old Cat said, "As long as we can successfully decelerate and reduce the speed enough … many problems will be solved."
"Yes, yes."
Tang Yue's eyes widened. Looking at the situation, the Old Cat didn't seem to be joking. Did it really have a solution?
"Deceleration requires power. As long as we have enough power, we can solve those seemingly unsolvable problems very simply and crudely."
"Orion's engine?" Mai Dong asked.
Old Cat nodded.
"Old Cat, you just said that dismantling the engine was impractical!"
Tang Yue yelled. "You said it yourself that all the simulations you did failed. None of them were able to exceed ten thousand meters!"
"Of course it's impractical to dismantle the engine." Old Cat rolled his eyes. "Have you seen the rocket engine on Orion?
Was that thing something that could be dismantled by human strength?
Miss Mai Dong does need to take the Eagle, but the Eagle isn't the key … Think about Apollo 13. Was the lifeboat that saved everyone's lives the command module? "
Apollo 13?
Tang Yue was stunned. Following that, his scalp tingled.
His train of thought had indeed made a mistake. The Eagle was a lander, so Tang Yue subconsciously believed that it was the crux of everything.
Everything revolved around the Eagle lander. That was why he wanted to dismantle the engine and install it on the lander. That was why he racked his brains on how to stabilize the lander.
But the thing that could really save Mai Dong's life … was never the Eagle!
"We don't want to dismantle the rocket engine," Old Cat whispered. "We want to dismantle the Eagle lander and Orion!"
Tang Yue suddenly understood. This was another crazy plan. It was even crazier than the previous attempt to capture the lander in the space station. They couldn't land successfully because there wasn't enough thrust. If there wasn't enough thrust, they would increase the power. If one engine couldn't satisfy their needs, they would use all nine engines!
He didn't know if this idea was inherited from the Falcon Heavy or the N1.
If it was the former, Tang Yue could be at ease.
If it was the latter …
"You said that Orion will crash when it enters the atmosphere!" Tang Yue grabbed Old Cat.
"That's right." Old Cat's expression was cold. "What we want is for it to crash!"
A robot was a robot. When it went crazy, it wasn't human.
Later, Old Cat said:
Ninety-nine percent of the problems humans face in aerospace engineering are caused by insufficient power. As long as there is enough power, these are not a problem.
The last one percent is the system's responsibility as usual.
·
·
·
"We all know that if an object is dropped from a high altitude on Earth, it will move in a state close to free fall, but it won't be a true free fall."
"Because of air resistance?" Mai Dong said.
"Yes, this object will continue to accelerate, but it won't accelerate forever."
Old Cat said, "At a certain point in its descent, gravity and air resistance will balance out. Then, it will fall at a uniform speed."
Mai Dong and Tang Yue both nodded. This was easy to understand. It was the content of high school physics class.
"This is affected by the density of the air. In physics, there is a term called 'ballistic coefficient.' The ballistic coefficient in the Martian atmosphere is very low. In other words, it is difficult for the atmosphere to give you enough resistance to allow you to reach a state of equilibrium."
Old Cat continued, "If we drop the unpowered Eagle spacecraft, its deceleration will be very slow. When the altitude drops to 40,000 meters, its speed will still exceed 15 times the speed of sound. The surface temperature will rise to 2,000 degrees Celsius. This is why we need heat-resistant tiles."
"In the last century and at the beginning of this century, many Mars probes broke down because of this. The speed was too fast to descend."
Old Cat shrugged.
The most typical example of a Mars probe that crashed during the landing process was ESA's Beagle 2. The poor lander was still lying in the wilderness.
"The lander's normal landing process is like this: At an altitude of 125 kilometers, it will begin to enter the atmosphere. At this time, its speed will be about 5 kilometers per second."
Old Cat demonstrated to the two of them again with a pen. It raised the pen in its hand high and then plunged it down. "After 85 seconds, the deceleration air cushion will be opened and the first deceleration will be carried out. In these 85 seconds, its altitude will drop by 90 kilometers and it will survive the most severe heat barrier."
"The deceleration air cushion will reduce the speed of the Eagle spacecraft to less than two times the speed of sound. This is an acceptable Mach number for opening the parachute. At an altitude of 10,000 meters, the lander will open a 30-meter canopy parachute."
Old Cat opened its paw at the end of the pen to indicate the parachute. "The parachute will reduce the speed of the Eagle spacecraft to less than the speed of sound until the lander's altitude is less than 1,000 meters. Then, it will abandon the parachute and turn on the rocket engine to adjust its attitude. It will reverse the deceleration and finally land vertically."
Old Cat slowly placed the pen vertically on the table.
Mai Dong and Tang Yue knew all of this. During the training before the mission, the people on the ground had explained in detail how the spacecraft worked.
Old Cat repeated it again today.
"Why is this process so complicated?" Old Cat asked. "Why is it so complicated?"
Before Mai Dong and Tang Yue could speak, Old Cat answered.
"Because we don't have enough power. We can't use the rocket engine to reverse the entire process. The efficiency of a chemical rocket is too low."
Old Cat said, "More than half of the engine's thrust is used to propel itself. Thousands of tons of mass is fuel, and the remaining fraction is used as a load."
"During a normal landing process, it's impractical to use the rocket to reverse the entire process. That way, the Eagle spacecraft would have to fill the cargo bay and command module with propellant, and the lander would become a flying fuel tank."
Old Cat continued, "But that's under normal circumstances. We are going to make an abnormal landing … We don't care about efficiency, cost, or a few hundred tons of fuel. We just want that fraction!"
Old Cat raised its paw and pointed at Mai Dong on the screen.
It said, "A fraction of 60 kilograms!"