The old cat quickly figured out what was going on, there was a problem with one of the sensors on the Eagle spacecraft, it gave the lander computer a false signal, and the computer mistakenly thought that it had reached the predetermined orbit, so it shut down and abandoned the first stage rocket early, which was twenty seconds earlier than the scheduled shutdown time.

That is, the Eagle spacecraft turned off its engines in the first hundred and eighty seconds after launch.

This mistake could have been avoided, as long as the Kunlun station and the Eagle spacecraft kept in touch, the Kunlun station was able to correct its mistake in time, but unfortunately the communication between the two sides was interrupted when the computer went wrong, and no one came to stop the lander's system from nerving.

Turning off the engine early was an extremely serious mistake, and the result was a failure to enter orbit.

The Eagle spacecraft did not enter the intended parking orbit at all, it entered an elliptical orbit with an apogee of 280 kilometers and a perigee of 110 kilometers, which was simply derailed.

The old cat grabbed his ears in frustration and pinched them...... Hell, I just praised this kid for being obedient, why did something go wrong in a blink of an eye? This is a big problem.

Tang Yue hugged the antenna and came back staggeringly.

He put the antenna on the floor and sat down to gasp for air: "How? Did that kid succeed? ”

The old cat turned around, "Successful fart, your son is about to be shot by the German devils." ”

Tang Yue was taken aback, "What? How? ”

He didn't even have time to take off the bright light armor, and even crawled to the ground and leaned in front of the computer screen, exuding cold air all over his body.

The computer has shown two tracks, one is the predetermined track of the outer circle, indicated by a red dotted line.

The other is the actual orbit of the Eagle spacecraft, which is indicated by a solid blue line.

It is clear that the height of the real orbit is lower than the predetermined height of the mooring orbit.

"Now the altitude of the Eagle spacecraft is only two hundred and eighty kilometers." The old cat pointed to the cursor on the computer, "But it should have been three hundred and fifty kilometers high." ”

"Is it troublesome?"

"It's a lot of trouble." The old cat nodded, "This little thing did not enter the correct docking orbit, which means that our previous plans are all nullified, and the subsequent orbit changes and rendezvous procedures have to be redesigned, and we have to expend more propellant to accelerate because the altitude of the initial orbit is too low...... But that's not the most troublesome. ”

The old cat neatly dragged the mouse, enlarged the image, and then pointed to Tang Yue at the other end of the orbit, "This is the perigee of the orbit, that is, the lowest altitude, its height should have been one hundred and fifty kilometers, but it is only one hundred and ten kilometers now...... This height is too low. ”

"One hundred and ten kilometers have entered the atmosphere, and although the atmosphere at this altitude is very thin, there is still resistance." "Every time the Eagle spacecraft passes perigee, it will consume energy due to the drag of the atmosphere, and its altitude will continue to decrease, and the final result will be ......"

The old cat pressed the enter key, and the computer gave the simulation results.

The result is a tight blue spiral that looks like a mosquito coil, which means that the orbit is decreasing in altitude and getting closer to the surface of Mars, eventually plunging headlong into the atmosphere and everything will burn to ashes.

Tang Yue opened his mouth and was stunned for a long time before realizing that he was shocked into a cold sweat.

"We've got to get it off track as soon as possible!"

"I want to, too, but we can't let the Eagle ship accelerate recklessly." "Don't forget that we don't have enough propellants, and the consequence of indiscriminate acceleration will only be to turn the payload bay of the lander into a piece of garbage in space." ”

"How much longer?" Tang Yue asked, "How long is the lander?" ”

"The current cycle of the Eagle spacecraft is fifty-three minutes, and it orbits Mars every fifty-three minutes." The old cat replied, "It can still orbit Mars before it is lowered to the lowest safe altitude......

The old cat entered the parameters into the computer, and the computer quickly gave the result.

"Sixteen laps."

Sixteen laps.

Fifty-three minutes in one lap, then the Eagle spacecraft has fourteen hours left.

They had to get the lander to change orbit and get out of the orbit that would eventually lead to death within fourteen hours, and the time was very short, but hell it was a rush to do so.

Tang Yue and the old cat both stared at the Eagle spacecraft on the screen, the old cat zoomed out the image slightly to bring the second orbit into their field of vision, and another cursor slowly moved on the orbit - this is the orbit of the Joint Space Station, an elliptical orbit with a higher position of 380 kilometers at a perigee and 480 kilometers at an apogee.

The Joint Space Station operates in one hour and twenty minutes, or 14 hours, which is only enough time for it to orbit Mars ten times.

"Within 14 hours, there were only seven suitable windows for changing orbits." The old cat said that it stretched out its paws and pointed to the apogee of the lander's orbit on the screen, "The lander's flight line speed at the apogee is 3.2 kilometers per second, and according to the normal orbit change method, it should accelerate at the apogee and then enter a new orbit......

The old cat tapped on the keyboard, and the system computer of Kunlun Station gave the calculation results.

A new large circle was drawn, marked in a striking bright yellow, and placed on the outside of the Eagle spacecraft's elliptical docking track, which was cut inward into it.

The place where the two circles tangentially meet is where the lander accelerates its transfer.

To put it more simply, if the Eagle spacecraft accelerates at the apogee of the parked orbit and ignites the upper-stage rocket, it will enter a circular orbit more than 280 kilometers above the earth, but it will not be able to dock with the Joint Space Station in this orbit, because the latter's orbit is still at a higher place, and the perigee of the Joint Space Station's orbit is as high as 380 kilometers.

Therefore, the Eagle spacecraft also needs to undergo a secondary orbit change.

Accelerate again.

The second acceleration allowed the upper stage rocket to push the Eagle spacecraft one more time before the lander jumped into orbit on the space station.

This is the most secure method, using two intermediate orbits and two accelerated orbit changes, which is the most widely used orbit change method.

"But it's risky." The old cat shook his head, "Using two intermediate tracks and changing orbits twice seems the safest, but it also consumes the most propellant, if we take this decision...... Then we will use up all the propellants of the Eagle spacecraft. ”

"If we do two orbit changes, how many times will we be able to rendezvous and dock at the end?"

The old cat pricked up a paw and said slowly.

"Once, only once at most."

Once.

Tang Yue's hands and feet were a little numb, and he only had one chance to try, so the success rate was only five percent.

If you don't succeed, you will be benevolent.