I ask you to build tractors, but you build rockets?

Although ARCA has been established for a long time, it can be said that its style of painting is unique and it is an outlier among many private aerospace companies.

Freeman is absolutely right about their game-playing nature. This company has never taken advantage of investors' money, nor has it developed commercial projects. It just likes to play with crooked things.

In addition to the projects funded by NACA in the last century, they are probably the only ones who have invested a lot of energy in researching air-tip engines. Later, they even developed the heresy of water engines.

As for why they were targeted by NACA and pushed Pratt \u0026 Whitney to conduct mergers and acquisitions, the reason has to be traced back to the Long March 18th.

Before the latter became a permanent member, NACA had officially confirmed that XAP had not only actually established the project but had also made considerable progress, which attracted John's great attention.

Whether it is the current director Robert or the former director Claire, they have made it very clear to John: the practicality of the Long March 18 is completely out of proportion to the investment, and it can only be used for special missions such as the Jiu Zhang, while NACA has hundreds of them. Methods can achieve the same effect, and there is no need to force benchmarking.

But John doesn’t understand aerospace, and members of Congress don’t understand aerospace either. They also know that a large number of people also don’t understand aerospace, but they understand that the criterion for judging the superiority of a rocket is which one is bigger, heavier, and more powerful.

Even if technical experts continue to explain, as long as people compare the size of the rocket, an intuitive impression will be left in their hearts that cannot be erased.

Therefore, a large number of congressional senators strongly demanded the construction of a more powerful rocket to surpass the Long March 18, and flipped the "Hailong" with a larger take-off weight, putting tremendous pressure on NACA.

Robert also had to seriously consider the possibility of realizing the Sea Dragon rocket, and then quickly overturned it. The reason was the same as the anxious Aerospace Development Committee - the launch guarantee was too complicated, and even if it was built, it would be difficult to launch.

You must know that the first stage of the Sea Dragon is a liquid oxygen kerosene engine. Just one engine would have a thrust of 30,000 tons, so it was quickly rejected.

But it is more difficult to connect multiple engines in parallel. Even a 680-ton thrust F1 engine requires 44 units to have the same thrust. The bottom resonance and fuel pipeline alone are enough to make people’s scalp numb. The Long March 18 has 39 280-ton hydrogen engines. The oxygen machine is basically the limit of parallel connection of multiple machines. No matter how many machines are connected in parallel, the difficulty of controlling them will increase exponentially, and the trouble of parallel F1 machines will be much greater.

So is there a rocket engine with particularly large thrust, low manufacturing difficulty, and most importantly, low cost?

Only then did ARCA enter NACA's field of vision. Their LAS 25DI engine uses electric heating to heat water that is pressurized to 250 degrees Celsius, heats it to a supercritical state, and ejects it. It takes advantage of the large weight of water molecules to easily achieve 7,000 tons. Thrust, and the engine size is still very small. It is not much larger than F1 but the thrust is 10 times higher.

Although the LAS 25DI is ridiculously bad and has a short working time, it is indeed extremely cheap and not without practical application value.

When a rocket flies into space, the stage where it needs to overcome the maximum gravity is the period where it accelerates from zero and reaches an altitude of less than 10,000 meters.

This stage consumes the most energy and faces the greatest air resistance. After this stage, the rocket's pressure will be much smaller.

For example, the Saturn V rocket has a launch mass of about 3,000 tons, a LEO carrying capacity of 118 tons, and an overall carrying coefficient of 3.93%; but if the mass of the first stage is subtracted, the remaining part is only 788 tons, and the carrying coefficient of this part is reached A staggering 16.4%.

The important indicator of a rocket's first stage is the thrust-to-weight ratio, and the upper stage is the specific impulse, so it doesn't matter if the first stage has a bad specific impulse. As long as the thrust-to-weight ratio is sufficient, the upper stage can be sent to a predetermined height and reach a certain speed.

NACA approached ARCA and asked them to design a water engine with a thrust of more than 40,000 tons and a specific impulse of at least 150 seconds.

According to NACA's calculations, the fuel and rocket body mass required for a water engine with a thrust of more than 40,000 tons is about 16,000 tons. The upper stage, with a total weight of 5,000 tons, is powered by hydrogen and oxygen, and the thrust is only 3,300 tons. 10 ready-made RS68 engines are enough. If it can be satisfied, the difficulty of such a design will be much lower.

The ARCA company lived up to expectations and instead proposed a more radical LAS88N (88 million pounds of thrust, atomic power) engine.

The LAS88 has an extremely simple structure with only three parts, namely the combustion chamber, the reactor, and the water tank.

The water tank is still pre-filled with water at 250 degrees Celsius. Since there is ultra-high pressure inside the water tank itself, LAS88 directly omits the turbine pump mechanism and directly allows the superheated water to enter the reactor core.

Under the high temperature of the high-pressure first-stage reactor core in the water tank, the superheated water directly turns into supercritical water vapor with a temperature exceeding 700K and a pressure exceeding 22Mpa. It rapidly expands and ejects in the bell-shaped combustion chamber, directly generating thrust.

The heating capacity of a nuclear reactor is far more powerful than that of electric heating. It can easily double the specific impulse. It also solves the problem of battery quality and makes the reactor lighter.

Since the thrust-to-weight ratio of the new Hailong rocket exceeds 1.9, it is bound to produce a huge water hammer effect when taking off. The water in the water tank will be squeezed downwards more violently under the action of acceleration, resulting in higher pressure, and will also increase with the rocket. The constant acceleration is getting bigger and bigger, and the pressure entering the core can be maintained even if the amount of water continues to decrease.

The total working time of LAS88N is only 52 seconds, but it can accelerate the rocket to 1,690 meters per second and separate at a height of 40 kilometers. The remaining upper stage can send at least 600 tons of payload into a 300-kilometer progress orbit.

A major feature of the new Hailong rocket's first stage is that its cost is very low. It is much easier to store 250-degree superheated water pressure than liquid hydrogen and liquid oxygen fuel. The existing stainless steel (non-aerospace grade) can easily handle it, and it can be used up. Just throw it away without any burden.

The combustion chamber can also be thrown away. Only the middle reactor needs to be thrown out as a module and then recovered by parachute into the sea. Except for the expensive reactor, the other parts of the first stage may cost less than 5 million US dollars in total.

As for water contamination through the combustion chamber? Since the reactor only needs to provide high temperature, NACA believes that Dr. Freeman can make the radiation content of the ejected water vapor meet atmospheric emission standards.

This water vapor will basically become clouds in the rocket flight area, and the radiation level is far less than that of a hydrogen bomb nuclear test. Since the Hailong is also launched from the water, there are many uninhabited areas in the two vast oceans.

The LAS88N engine was finally approved by NACA, and then ARCA was forced to "confirm" and start serving NACA. These researchers who were just playing around were also very excited, thinking that finally someone with a "smart eye" discovered these lonely geniuses.

After understanding this, Freeman had to lament NACA's amazing imagination. However, the LAS88N project is indeed unusually reasonable. It is a typical representative of "big efforts can produce miracles". Apart from the reactor, I really can't choose any other design. Reasonableness.

"Okay, I will take care of the reactor part, but please don't launch this thing on the east and west coasts, not even the Bay of Mexico."

Stringer: "If possible, it would still be launched in the South Pacific, near Tuvalu, which would be great."