In that moment, Tang Yue seemed to have returned to the era of Yuri Gagarin and Alan Shepard a hundred years ago, when engineers tried their best to build hundreds of tons of launch pads and use nearly 30 tons of R-7 and redstone rockets to send those 70 kilograms of payload into space.

This is a huge asymmetry between mathematics and physics, and such a huge amount of resources are ultimately aggregated in a small individual.

After a long time, people have the ability to build a space station, the ability to go to the moon, the ability to go to Mars, they have forgotten the past caution and step-by-step, the earliest liquid oxygen alcohol engine low earth orbit carrying capacity of less than three tons, the first manned spacecraft is only two meters long.

But this was the beginning of human spaceflight.

When the old cat resolutely said, "We only need this fraction", the times went back in an instant, to the moment when Korolev said "no spacesuit", to the moment when von Braun said "the countdown begins" at the Kennedy Space Center, and the engineers spent tons and tons of scratch paper, gram by gram, calculating the weight, just for that small fraction.

The glory of human space flight has been won step by step from this small fraction.

"It's not just the Eagle spacecraft that's going to enter the atmosphere, it's Orion, right?" Tang Yue asked.

"Yes." The old cat nodded, "Orion is the lifeboat, Aquarius of Apollo 13." ”

Orion II Earthfire Transfer Spacecraft.

One of the largest spaceships ever built by man, and the reason for adding this 'one' is because Orion-1 is as big as it. They are not so much spaceships as they are powered space stations, and in order to provide enough living space for a crew of six people and store enough supplies and living resources, the Orion spacecraft is completely different from the configuration of regular spacecraft.

Its main body is a three-section spliced truss with a length of 88 meters.

At the front of the truss are 8 solar panels with a width of 60 meters, which are power and energy modules.

The middle part is the command compartment and the living compartment, there are a total of eight cabins, which are docked in turn and arranged on the main truss around, which is the central module.

At the end of the truss is a huge propellant tank with nine Raptor 10D liquid oxygen methane high-pressure refueling engines, the propellant tank can be refilled multiple times, and the engine can be reused, which is the power module.

The Orion spacecraft is a rather fragile structure by design, consisting of three sugar gourds strung together on a thin stick, unable to enter the gravitational sphere of Earth or Mars. Once subjected to gravity, the main truss will undoubtedly not be able to bear the weight of the passenger compartment and the engine, and will immediately twist and break.

The day it enters the atmosphere is when it is scrapped and decommissioned.

The Orion spacecraft was born in space and returned to Earth.

"You're going to get Orion into the atmosphere with the Eagle spacecraft?" Tang Yue asked, "Is this ...... Is this possible? ”

As a person who has a little understanding of aerospace engineering, Tang Yue feels that this idea is too crazy and too many problems to solve.

Intuitively, the Orion spacecraft will inevitably disintegrate in a high-speed fall, burning and exploding.

"Sometimes...... "the old cat waved his paws," "technology is the craziest." ”

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"The length of the Orion II spacecraft is eighty-eight meters, which is the length of its main truss." The old cat pinched its pen and began to explain the plan to the two of them, "If we ......"

"Throw it down." Mai Dong and Tang Yue both knew what the cat was going to say next.

“…… Yes, if we throw it down, into the atmosphere, 100 percent it will disintegrate and crash. The old cat pinched the pen and crossed it above the table, "It can't come down like this, but if we turn it in the other direction......"

The old cat put the pen in his paw up.

"Let it go down like this, then it is possible to ensure the integrity of the structure, which is determined by the material and structure of the truss, which has five to six times the load capacity in the vertical direction and the lateral one, and decelerates during the landing, and the force on the truss is squeezed rather than stretched...... As long as we keep it vertical during landing, then it can stick firmly to the end! ”

"But how do we keep it vertical?" Tang Yue asked, he couldn't imagine how he could keep an eighty-meter-long thin stick standing tall in the air.

"Korolev Cross!" The old cat replied, "Or, rather, imitate the Korolev Cross!" ”

Korolev Cross? Tang Yue frowned, he vaguely remembered that this word was to describe the Alliance Rocket Release Booster.

"We have nine Raptor 10D engines, nine swinging nozzles, and each one has enough thrust." "It's not as difficult to erect this stick in the air as you might think, and the total weight of the Orion spacecraft is four hundred and nine tons, of which three hundred and twenty-nine tons are propellants and engines, which means that its center of gravity is at the bottom end - because the engines are facing down when landing." ”

"As long as the four engines maintain thrust in all four directions, then the stick will stand firmly in the air." The old cat put the pen in his hand on the tip of his claws, "The lower head is heavy, the upper head is light, and the center of gravity is low, so as to maintain stability, if it is reversed, it will not work, of course, it cannot be subjected to any lateral thrust in the process, this is also thanks to the fact that there is no atmosphere on Mars, and the earth cannot do this, and there is a big crosswind." ”

"Hot ...... What about thermal barriers? Mai Dong asked.

"Don't worry about heat barriers, silly girl." Tang Yue pinched his chin and muttered for a few seconds, "This cat has to push back and land all the way to control the falling speed, but is the propellant on Orion enough?" ”

“Bingo！ This is the point. The old cat snapped his fingers, "Propellant is the key to the whole plan, we have a total of nine Raptor 10D engines, and there are still three hundred tons of fuel in the propellant tank of Orion, if the propellant is not enough, everything is in vain, then we can settle an account." ”

Mai Dong and Tang Yue nodded.

Hope lies in the old cat's account.

"The vacuum thrust of one Raptor 10D engine is 900 kN, that is, ninety tons, and the total thrust of nine engines is more than eight hundred tons." "The average Raptor engine consumes fuel at a rate of 60 gallons per second, which translates to 227 liters in metric units, and the total mass of 227 liters of liquid methane and liquid oxygen is 202 kilograms. ”

The old cat pointed to the sky above his head, "That is to say, the engine of that spaceship, a Raptor 10 rocket, will burn 202 kilograms of propellant in one second, and we have a total of three hundred tons of propellant to consume, nine engines are started together, how long is so much propellant enough to last?" ”

"One hundred and sixty-five seconds." Mai Dong immediately gave an answer, "Less than three minutes." ”

Tang Yue was shocked.

One hundred and sixty-five seconds is definitely not enough.

To descend safely from a 125-kilometer orbit, 165 seconds is absolutely not enough.

"That's obviously not enough time." "The spacecraft will run out of fuel at tens of thousands of meters in the air, and then fall down and crash." ”

"What should I do?" Tang Yue asked, "You said there was hope." ”

"We want to thank the designers of the Raptor 10D engine, one engine has a thrust of 90 tons, and it supports the landing of a 400-ton spacecraft, do we need to turn on all nine engines?" The old cat smiled.

Tang Yue immediately understood.

The total weight of the spacecraft is four hundred and nine tons.

The thrust of one engine is ninety tons, so as long as five engines are driven, a total thrust of four hundred and fifty tons can be generated.

"We can use throttling technology, control the thrust of the engines, and only turn on five engines, then you will do the math." The old cat said, "How long is propellant enough to hold up?" ”

"Two hundred and ninety-seven seconds." Mai Dong's voice trembled, "At least two hundred and ninety-seven seconds." ”

"Yes, at least two hundred and ninety-seven seconds, the real situation should be much greater than this number, because the gravity of Mars is only two-fifths of that of Earth, so the weight of more than four hundred tons of the Orion spacecraft is only one hundred and sixty tons here." The old cat nodded, "So the engine consumes less propellant than we calculated, and in fact Orion has enough fuel for twelve minutes." ”

"In twelve minutes, we were able to control the average landing speed of the spacecraft at 173 meters per second, which is less than Mach 1."

Tang Yue was stunned.

Mai Dong's eyes began to redden.

"You can come down." The old cat turned his head, shook his ears at Mai Dong on the screen, and smiled, "Miss Mai Dong." ”