Five Raptor 10D engines can provide more than 400 tons of thrust, while the disassembled Orion spacecraft has a mass of 330 tons, and according to the conservation of momentum, the rocket engine must reverse eject a sufficient mass of high-speed working fluid to effectively counteract the high speed of Orion itself.

The Orion spacecraft's computer controls the engines precisely, and the old cat has written a fairly rigorous flight program, but it is impossible to reduce the deflection error of the stupid black and thick nozzle of the Raptor 10D to the millimeter arc second, and their original purpose is not to make the spacecraft land vertically - rockets that fall vertically like the Falcon 9 back then rely on keen sensors and special feedback adjustment mechanisms.

The old cat has none of this, and it can only resort to the simplest and crude way - to deflect the nozzle of the rocket engine as far outward as possible, to frantically expand the safety redundancy, and to let the Orion pestle in the air like a tumbler.

At this time, if someone looks up on the ground beneath the ship, they will see a huge cross drawn by the jet of the rocket high in the sky.

This is the Old Cat Cross.

12 seconds after entering the atmosphere.

"The track angle has been adjusted again! Attack Corner Matching! ”

"The Raptor-05 thrust is 85%, and the 01,03,07,09 flow increase curve is in line with expectations." Tang Yue reported, "Orion's speed is 4872.23 meters per second, and the old cat ...... The engine was under a lot of pressure and the speed was just too fast. ”

"Old cat?"

"I know." The old cat's voice was low, "I'm staring." ”

The cooling fan of the workstation was spinning violently, and Comrade CPU plucked up all his strength, saying that it was not only the Orion spacecraft that was under great pressure, but also its own pressure.

The five curves on the display climb upwards, indicating that the five Raptor engines are gradually increasing their thrust, and in order to save propellant, the nine engines of the Orion will be turned on in stages.

If this is a real landing, then at this moment Orion is hanging alone at an altitude of twelve kilometers, relying on the thrust reverser of the rocket engine to slow down and stabilize its posture.

Once out of orbit and into the atmosphere, it no longer has any way back.

Tang Yue and the old cat stared at the monitor, at this time they couldn't do anything but stare at it, once they entered the atmosphere, most of the control was in the hands of the Orion computer, and the people on the ground couldn't interfere at will, and they didn't have time to interfere.

Steady.

Steady.

Tang Yue said softly.

Enter the atmosphere for 35 seconds.

The Orion spacecraft is steadily descending.

Kunlun Station was silent and dull, only the hurried and short voices of Tang Yue and the old cat sounded.

"Note that the IMU (Inertial Measurement Unit) error is accumulating, and the gyroscope drift deviation is higher than estimated."

"The density of the atmosphere on the windward side increases, and the drag coefficient increases."

As the thickness of the atmosphere gradually becomes denser, the situation faced by the Orion spacecraft and the workstation begins to become complicated, flying in a vacuum is completely different from the atmosphere, for the Orion spacecraft, the air does not play any role in slowing down, it will only make the environment complicated and tricky, for the workstation, the fluid simulation is very computing power, and the computer's CPU is starting to keep up.

Tang Yue's gaze swept over every parameter on the screen, and the combination of these seemingly insignificant numbers and charts was a complete spaceship, flying in his brain.

The altimeter on the monitor was beating wildly, and if it were a mechanical watch, the gears would have rubbed and sparked, not so much as a landing for Orion, but a deliberate and controlled crash.

The HP workstation cannot accurately simulate the environment of the Orion spacecraft when it enters the atmosphere, and the huge size of the Orion constellation, which is tens of meters long, and the force situation and working environment are extremely complex, it is really difficult for the workstation to simulate it - it is not a supercomputer covering an area of hundreds of square meters after all.

The old cat actually simplifies the task of the workstation, and some details are temporarily taken directly to the fixed ideal value, and then taken out separately for testing in the future, which is not safe or meticulous, but this is a helpless move, otherwise the computer may blow itself up in protest.

"The GNC system should be more adaptable and robust." The old cat frowned and tapped his toes on the table, "The RCS three-axis attitude stability can be optimized, and it can be optimized again......"

75 seconds after entering the atmosphere.

Mai Dong lay quietly on the chair, raising his hand from time to time to look at the time.

Tang Yue told her that when she actually landed, she would experience a very terrifying sharp deceleration after entering the atmosphere, and the huge overload would press Mai Dong on the chair and unable to move, and she would not be able to raise her arms during this time, and she would not be able to move her body until the deceleration was completed and the spacecraft entered a constant motion.

That six-minute deceleration was a matter of life and death, and if something was going wrong with the Orion spacecraft, it was probably in this time.

"Tang Yue?"

"Hmm." Tang Yue replied, "I'm here." ”

"Am I still alive?"

"Alive." Tang Yue said, "You are landing safely, and the current altitude is 35,887 meters. ”

"You heard you say before, 10,000 meters is a hurdle?"

"The old cat said that if the density of the atmosphere increases below 10,000 meters, the environment will become very complicated, which is not conducive to the attitude stability of the spacecraft." Tang Yue said, "But don't worry, the Orion spacecraft has enough ability to maintain stability...... We still have a lot of fuel and the engine is reliable. ”

"Raptor-01, 03, 07, 09 shut down! Attention, Raptor-01, 03, 07, 09 are powered off! The computer self-test is normal, all departments pay attention! "The old cat is snorting across the monitor," 02, 04, 06, 08 start! ”

As soon as the old cat finished speaking, the system showed that four engines were turned off, and at the same time, the other four engines were turned on.

It's time to hand over the baton, for the Raptor engine of the Orion spacecraft, this 120-kilometer landing is a relay race, the previous engine has completed its task, can take a break, they handed over their baton, the next 30,000 meters of altitude will be finished by the next batch of engines.

"If this mock test is successful, I will probably regret it." Mai Dong said.

"Regret what?"

"I regret that I didn't really go down." The girl smiled, "Isn't it a pity that the success rate is so low, and it is not easy to succeed once, but it is just a mock test, and it can't be counted?" Anyone would think so...... Ah, if only I took advantage of this opportunity to go down, right? ”

"No mock test is a representation of real practice, and the workstation has limited capabilities to fully simulate real-world situations." Tang Yue shook his head, "The flight control system of the Orion spacecraft still has big flaws and flaws, and we can't let you land rashly ......in this case."

As he was talking, a pop-up window suddenly popped up on the screen in front of Tang Yue's eyes, and he was taken aback.

"Code 1028 Alarm!"

"Code 1029 Call the Police!"

"Code 1170 Call the Police! Old cat! ”

"Roger." The old cat buried his head in the monitor, "Received...... 1029 is a structural strength alarm, 1170 is a posture stability alarm, hell, something is wrong, there is a problem with Orion. ”

"Questions?" Tang Yue was stunned, and it was less than half a minute before the alarm pop-up pop-up popped up, and the parameters of the full screen began to scurry wildly, one after another, and the speed was so fast that it was too late to react.

"Old cat! Red all over! Tang Yue shouted.

"I'm red all over here, too." The old cat crackled on the keyboard, thinking that the screen in front of it was also layered with red warnings, and a white cat face was reflected red, "The RCS attitude of the Orion spacecraft has collapsed steadily, it has given the computer an error signal, the computer is commanding the engine nozzle to deflect the direction, trying to stabilize the attitude of Orion, the spacecraft is deviating from the central axis, I am looking for the source of the fault, I am looking for the source of the fault!" ”

The most worrying thing happened, the ship was unable to stabilize its posture, and it was slowly capsizing.

Before the test, the old cat repeatedly emphasized that the deviation angle of the spacecraft could not exceed five degrees, and once it exceeded five degrees, the fragile hull structure of Orion was at risk of collapsing.

At this moment, the spacecraft is gradually approaching the limit of five degrees.

"Can you get it back?" Tang Yue roared, "The deviation angle is two degrees and thirty points!" ”

"I'm working on it!" The old cat said viciously.

"The deviation angle is three degrees fifty minutes! Three degrees and fifty-two minutes! Haven't found the source of the problem yet? ”

"I'm troubleshooting bugs and sensors, and fixing engine control commands ......"

"The deflection angle is four degrees and forty-seven minutes! Four degrees fifty minutes! Four degrees and fifty-five minutes! Tang Yue sweated profusely, "The strength coefficient of the main truss structure is approaching the limit, and the structure of the spacecraft will not be able to hold it!" ”

Mai Dong quietly listened to Tang Yue and the old cat roaring in the channel, she raised her hand to look at the time, 267 seconds had passed since the re-entry into the atmosphere, and according to the normal progress, the spacecraft was approaching an altitude of 10,000 meters at this time.

Despite the busyness underneath, it was still dark and quiet inside the lander.

"The deflection angle is five degrees and thirteen minutes! The structure coefficient is 77%! Old cat, if you don't hurry up, the spaceship will crash! The spaceship is about to crash! ”

"Five degrees and twenty-seven minutes, the structural coefficient is 80%!"

"Five degrees and forty-three, the structural coefficient is 88%!"

"Six degrees, 93%! 95％…… 97％！ 98！ 99！ ”

"Found it! Damn, a little logical problem! When the system is correcting-" The old cat slapped the table, Tang Yue got up at the same time as it, pushed the keyboard violently, and interrupted it with a loud voice, "The main truss of the Orion spaceship broke and disintegrated. ”