Finally when Tupolev got the new Tu-4 scheme that applied a lot of new technologies, there was another moth in the engine, and the Ash-73TK piston engine was in short supply for a while because the demand was too strong, and at this time the General Armament Department saw the potential of jet power, and suddenly a new idea came up - it seems good to build a jet bomber.

As a result, the new Tu-4 project, which had just had an eyebrow, died halfway again, and the Military Commission ordered Tupolev to replace the new Tu-4 with jet power, so as to make the maximum flight speed reach about 650 kilometers as much as possible.

Good guys, this almost killed Tupolev, maybe in the eyes of the Military Commission, the new Tu-4 is nothing more than a matter of changing the engine, the jet engine is so powerful, it is simply too easy to go up at speed.

But the truth is that this is a nonsense idea, because the need for speed broke through the sky (which seemed to be the case at the time), and in order to meet the need for speed, the aerodynamics of the aircraft inevitably had to be overturned. This is tantamount to asking Tupolev to work on a new Tu-42.0 project. Anyway, it took the life of this meritorious designer.

There may be comrades who want to ask, it is impossible not to see that this is nonsense at the level of a certain immortal, and it is not a good thing in the military industry to change the order and blindly try to be greedy. So why didn't he stop it?

It's not that Li Xiaofeng can't stop it, but he can't stop it, because the one who is the most cheerful in this regard is Sverdlov, and in the eyes of the future leadership core, the Soviet Union has reached the time to catch up with Britain and the United States, and any weapon and equipment will inevitably overwhelm these potential enemies.

And his thinking was very much in line with the ****** atmosphere that existed in the Central Military Commission at that time, because the situation was very good after successive victories on the battlefield. This made some people a little dizzy and lost their self-knowledge, thinking that the Soviet Union was really capable of beating all opponents. Under this complacency, they could not listen to all the words of loyalty, and it was greatly inflated. So in this paragraph, there are signs of recklessness in all aspects.

The coverage of this kind of atmosphere is quite large, even Li Xiaofeng can't suppress it at all, and in desperation, he can only let reality pour cold water on this group of hot-headed guys.

For example, the new Tu-4 project encountered countless troubles at the beginning, first of all, the poor reliability of the jet engine and the high fuel consumption, which led to the fact that the new Tu-4, which originally existed as a strategic bomber project, had a shorter range than the Tu-3. Of course, if it is not a strategic bomber, but as a front-line bomber, its performance is not bad, and the maximum speed can reach 700 kilometers, which is faster than most German fighters. But the question is, have you ever heard of a four-engine front-line bomber?

Anyway, the performance of the prototype is very embarrassing, and basically there is no possibility of improvement, if you want to fill it with more fuel, it will naturally squeeze the bomb load, and an important mission of this aircraft is to drop the bulky atomic bomb. At that time, four or five tons of atomic bombs were not something that front-line bombers could afford.

In June 1944, the new Tu-4 project was declared a failure, and Li Xiaofeng also took this opportunity to beat the dizzy heads of the group of people in the Military Commission. Then Tupolev received a new task, the first was to return to the design of the new Tu-41.0 version, and the second was to pre-develop a twin-engine medium jet bomber.

After returning to version 1.0, the disadvantages that plagued the Tu-4 project naturally disappeared, and it took only three months for Tupolev to fly the original Tu-4 prototype into the blue sky. However, it was not until 1945 that the Tu-4 would actually enter production.

For Li Xiaofeng, this is still quite disappointing, but fortunately, on the other hand, he has gained a lot of money. That was the liquid rocket project led by Korolev. It has been said before that Li Xiaofeng ordered the development of Soviet ballistic missiles on the basis of the V-2, and Korolev moved very quickly in this regard. The piracy work was completed at the beginning of 1944, and by July 1944, the pirated V2 R-2 missile had been tested five times with three successes and two failures.

Note that this is not a negative statement, because it is a good result. Because the two failures belong to the first two, and the last three are successful. However, Li Xiaofeng did not rush to order the Soviet version of the V-2 to be put into production, because the performance of this missile is limited, the maximum range is only more than 400 kilometers, and the weight of the warhead is less than one ton.

The problem was that for the USSR, missiles were not needed to bombard large cities, and long-range aviation was enough to complete the task, so the Soviet version of the V-2 looked like a chicken. But in any case, this is a good start, and with this foundation, Korolev is ready to show his strength.

How do you show your skills? He was ready to go beyond the V-2 and develop a new liquid rocket that would not only have a longer range but also be able to carry a larger warhead, because Korolev was clearly told at the time that the new ballistic missile would have to increase the payload to 3 tons. It is clear that this was the preparation for the first generation of atomic bombs in the USSR.

And to do all this, Korolev believed that it was necessary to surpass the V-2, and it was necessary to have more powerful and efficient engines. But to make all this clear, we must first start with the engine of the V-2, and we cannot talk about the engine of the V-2 without mentioning the Von . Braun, the rocket genius, led a team at the age of 22 to start a rocket research project called the A-1, using an engine named Arthur. Rudolph designed a 300 kgf liquid rocket engine with liquid oxygen as an oxidizer and 75% alcohol as fuel. Of course, at that time von. Braun also considered other fuels, such as kerosene, but ultimately decided that alcohol would be easier to obtain, so he ended up using alcohol.

The A-1 rocket was a success, but was abandoned due to its extreme unreliability. Feng. Braun, for his part, continued to develop the A-2 rocket. This A-2 rocket is very groundbreaking, even if it is not much different from the A-1 in appearance, but the content is completely different!

This A-2 rocket broke new ground with the use of a squeeze cycle on a liquid rocket for the first time. Secondly, in order to improve flight stability, the gyroscope that controls the attitude of the rocket was moved from the warhead to the middle of the missile body (A-1 will become more and more top-heavy as the propellant is consumed).

The second improvement will not be discussed in detail, but the focus will be on the first extrusion cycle. Many comrades may not know what a squeeze cycle is and what it is for. As we all know, rockets are divided into solid and liquid, solid rockets are relatively simple and can be seen as a large artillery battle, while liquid rockets are quite complex.

To understand how liquid rockets work, we must first start with how they circulate. Why start with a circular approach? Because the engine alone is not enough to systematically summarize the propulsion device of a liquid rocket.

The propulsion system of a liquid rocket actually consists of two parts, one is the engine, and the other is the propellant pressurized delivery system (that is, the circulation mode). And the cycle mode can be said to be the basic element of the thrust generated by the liquid rocket engine. And what are the recycling methods?

That's a lot, such as the extrusion cycle mentioned above, as well as the gas generation cycle, staged combustion cycle, expansion cycle and so on. The earliest and easiest way to circulate is the extrusion cycle. And to understand this cycle is also very simple, in junior high school physics we should have been exposed to "water rockets". Making a water rocket is simple, it is enough to add a rubber sealing plug to a Coke bottle. Fill a part of the bottle with water (not too much, not too little) before launching, use a pump to inject air into it, and then the pressure in the bottle reaches a certain level, and then the compressed air in the bottle will squeeze out the water to form a reaction force to push the water rocket to fly.

And this is a typical extrusion cycle. It is conceivable that even water at room temperature can contain so much energy, what if the bottle is filled with water vapor instead of water? The high temperature and high pressure of water vapor through the nozzle for proper expansion can produce greater energy, the power of the boiler explosion of the steam engine comrades should be well known.

However, this method is not applicable to the rocket, because it takes energy to heat the water, so you can't install a boiler for the rocket, right? And it takes a long time to heat the water, and the weight of the water itself is too large, even if it is possible to boil the water into high-pressure steam on the rocket, I am afraid that the rocket will not be able to fly very high.

Speaking of which, it is necessary to touch on a concept that is often used in rocket engines - specific impulse. To put it simply, the specific impulse is the impulse produced by consuming one unit of propellant. This impulse is a process quantity, i.e., the cumulative effect of the action of the force on time, that is, the integration of the force on time. For rockets, we not only have to be "powerful" enough, but also the time to give force is too short, and even more so if it consumes too much propellant.

Back to Feng. Braun's A-2 rocket was designed to increase the specific impulse of oxygen and alcohol rockets, so the only way was to pressurize the propellant and increase its flow rate. That is, the role of the pump in the water rocket in front. Feng. After Braun chose to remove the gyroscope from the head of the rocket, he installed a pressurized nitrogen cylinder (i.e., a pressure accumulator) in this position, which injected nitrogen into the propellant storage tank to form an air pillow, squeezing liquid oxygen and alcohol to form a boost. This is the squeeze cycle.

By the time of the A-3 rocket, von . Braun went one step further and innovated on the basis of the A-2. He buried the pressurized nitrogen cylinder in the liquid oxygen storage tank, which was arranged concentrically. Since the boiling point of liquid nitrogen is lower than that of liquid oxygen, nitrogen cylinders surrounded by liquid oxygen can be kept at a very low temperature. With this design, a smaller cylinder can hold more nitrogen, which can make the engine work longer and save space inside the projectile. And this layout was also inherited by later generations of large launch vehicles and ballistic missiles.

And this is the basic principle of the extrusion cycle, which is different from other liquid rocket cycles, which do not require a turbopump. Although this results in lower performance, it is not completely without benefits. For example, reliability is improved, mechanical components are reduced to a minimum, and the propellants do not meet before being fed into the thrust chamber, thus avoiding the possibility of residual fluid freezing.

However, the problem of squeezing circulation is also significant, as the pressurization effect becomes worse over time as the pressurized gas is injected into the propellant storage tank. If the working time of the rocket engine is to be extended, it is necessary to carry more propellant, and at the same time the amount of pressurized gas must be increased, and the result will inevitably lead to the carrying of a huge pressurized gas cylinder, and as a pressure vessel, its mass can be imagined. To make matters worse, the extrusion cycle will put pressure on the propellant storage tank, and in order to ensure the safety of the propellant storage tank, its structure will inevitably be strengthened, which will also lead to a spike in weight.

That is to say, the extrusion cycle will eventually fall into a vicious circle of adding more water and more water and then adding noodles, and its effectiveness is really limited. So is it possible to jump out of this dead end?

The answer is yes. The method of pressurizing the liquid rocket engine has been thought of for a long time, for example, the bellows are a good way to pressurize. In the era of the steam revolution, in order to enhance the combustion efficiency of the boiler, engineers thought of a method of strong pressure ventilation, to put it bluntly, to add a blast pump to the boiler.

Tsiolkovsky, a Russian aerospace pioneer, was the first to realize that in order to give full play to the propulsion efficiency of liquid rockets, it was necessary to increase the pressure of liquid propellants. In 1903, the pioneer of space created a concept map of a liquid rocket.

Tsiolkovsky's sketch of the rocket was egg-shaped, with a crew compartment in the front and a propellant compartment in the rear, divided into liquid oxygen storage tanks and hydrocarbon fuel tanks, and an elongated liquid rocket engine located on the central axis of the rocket. Considering that the rocket engine would release a lot of heat when it worked, he thought of making the engine out of heat-resistant materials and diverting a part of the cryogenic liquid oxygen to cool the engine, so the Russians insisted that Tsiolkovsky was the first to propose the idea of cooling liquid rocket engines. Even the pioneer conceived that liquid oxygen would not only act as an oxidizing agent for propellants, but also supply members to breathe after vaporization. The only pity is that Tsiolkovsky's small piston pump, which was used to boost the propellant, did not give a source of power for its operation (this is important).

After Tsiolkovsky, an American took over the baton. In 1914, Goddard prepared to install a gasoline-powered piston pump on a liquid rocket. However, after a series of tortuous trials, the design was not reliable.

Returning to the Soviet side, after Korolev was not satisfied with the extrusion cycle, the pump pressure cycle was a viable solution. So the rocket engine giant Valentin. Petrovic. Grushko stepped forward. In the thirties and forties of the twentieth century, the design bureau of Grushko came up with the RD-1 engine, which was a very popular hybrid engine in the USSR at that time. The piston engine diverted a part of the power through the gearbox to drive the pump of the RD-1 to boost the propellant. However, Grushko's preference for combustion-stable nitric acid oxidizers makes the corrosion resistance of oxidizer pumps very difficult. It was not until 1944 that Grushko solved this problem relatively well.

Let's put it this way, Goddard's plan was to use a small piston machine to drive a large rocket, and Grushko used a large piston machine to drive a small rocket, but their attempts were not very successful. The one who really pushed the pump pressure cycle was the genius Feng mentioned earlier. Braun.

When designing the A-4 rocket, which later became known as the V-2 missile, von . Braun jumped out of the box of the extrusion cycle and introduced a lot of new technologies, the most important of which was naturally the pump pressure cycle, and he naturally thought of using the pump to deliver the propellant directly, but what power to use to drive the pump was a big problem. Do you think that every penny of a missile's weight is precious, and you can't always fit a dead piston engine as a power source, right?

The solution to this problem was not in von Braun, but in the hands of another German engineer, Helms ******. This person was helping the German Navy to develop advanced submarines, and he was mainly responsible for power.

As we all know, conventional submarines are limited by the level of batteries, and they have to float up and turn on the diesel engine to drive the generator to charge the battery after a while. So is there a way to get submarines out of this restriction?

The best way to do this was naturally nuclear power, but it was not realistic at that time. For this reason, engineers have thought of a lot of ways, such as simply carrying a little more oxidant, we can also open diesel engines on the bottom of the sea to generate electricity, for example, the Soviet Union tried to store liquid oxygen in World War II, but the danger of liquid oxygen stored at low temperature is too great, and if it is not good, it will explode, and the natural Russians have failed.

The solution that came to mind was hydrogen peroxide, which was safer than liquid oxygen. It can be stored at room temperature, and more importantly, hydrogen peroxide catalytic decomposition can grow oxygen-rich water vapor at a temperature of 500 degrees, which is enough to make hydrocarbon or alcohol fuels natural. In other words, whether it is direct catalytic decomposition of hydrogen peroxide or further combustion mixed with fuel, it is very suitable for driving turbines, which are called ****** turbines.

Of course, hydrogen peroxide has strong oxidizing properties, which is still quite dangerous. For example, in March 1934, when von Braun's assistant Dr. Wormke mixed hydrogen peroxide with alcohol, an explosion occurred, killing three people, including Wormke, on the spot, and the idea of hydrogen peroxide plus alcohol was banned.

Fortunately, the Luftwaffe soon experimentally proved that the injection of ******** salt solution as a catalyst into a high concentration of hydrogen peroxide could trigger a stable decomposition reaction, which allowed the Germans to pick up the ****** turbine again. For example, the V-2's turbopump is driven by hydrogen peroxide splitting, and since there is no combustion reaction in it, this pump can only be called a gas generator, not an ignition generator (very important).

V-2 has two storage tanks, A and B, where the ******** salt solution is used as a catalyst, and the B tank is 80% hydrogen peroxide. They meet in a gas generator and then there is a series of reactions, the main reaction is the catalytic decomposition of hydrogen peroxide, and since this is an exothermic reaction, and the reaction is quite violent, it is oxygen and water vapor that are generated. The side reaction is the decomposition of the ******** after being heated, and the generation is sodium permanganate, manganese dioxide and oxygen, and the side reaction increases the amount of oxygen generated, which is a big benefit.

The resulting gas pushes the turbine pump to output 580 hp at 3,800 rpm, driving the fuel pump and oxidizer pump, increasing the flow of alcohol and liquid oxygen to 58 kg/s and 72 kg/s respectively.

At that time, the V-2's propellant charge was 8,360 pounds of alcohol and 10,800 pounds of liquid oxygen, and the turbopump was actually only enough for the engine to work for a little more than a minute when it was working at full speed. And it was this ascent of more than a minute that was enough for the V-2 to fly three hundred kilometers with a warhead of almost a ton.

It seems that this is powerful, but for Korolev it is far from enough. The gas generator is still too small compared to the later ignition generator. Korolev's idea was to replace the gas generator on the V-2 with an ignition generator, making the turbopump more powerful!

Of course, at first Korolev and Grushko did not go that far, they intended to improve the design of the V-2. Prepare to replace the ******** salt solution with a silver-plated nickel mesh catalytic converter. They found that with silver-plated nickel mesh, 70% of the hydrogen peroxide decomposition products could reach a temperature of 233 degrees, while 90% of the hydrogen peroxide could reach 740 degrees. The only drawback, however, is that the catalyst is time-limited, only two hours.

After a series of tests, the original model of the new R-7 rocket with a solid catalyst was born. The RD-107/108 turbopump structure is more optimized than that of the V-2, in addition to driving the oxidizer pump and fuel pump, there are two auxiliary pumps with gear transmission, one of which is dedicated to supplying hydrogen peroxide to the gas generator, so that there is no need to use nitrogen extrusion in the hydrogen peroxide tank like the V-2.

There is no doubt that the prototype of the R-7 is out of the blue, achieving a high level of integration that the V-2 could not achieve. But Korolev and Grushko were not satisfied, because their work efficiency was really not high. So at that time, Korolev continued to refine the design of the R-7 on the one hand, and on the other hand, he was trying to break through the rules of the V-2.

Soon Korolev found an idea, and in his opinion the problem was hydrogen peroxide. Since the hydrogen peroxide catalytic decomposition reaction is very in the way, it is better to use the propellant used in the main combustion chamber and let it be mixed in a separate combustion chamber, but the working temperature can be controlled a little lower. Such an independent combustion chamber is the gas generator, which produces real gas. Only a small amount of compressed gas is required to blow the propellant into the gas generator, and once the gas generator starts driving the turbine, it can take over the work of pressurizing the propellant. How convenient is that!

Of course, in 1944 this was only a general idea, and even Korolev took it as a long-term plan. At present, his main focus is on the overhauled V-2, which is the Soviet R-7 rocket.

In October 1944, with the financial support of the KGB, the RD-107 engine was tested, which preliminarily verified its reliability. Over the next two years, this test will be carried out dozens of times, and only after it is fully mature, will the next round of tests, known as live-fire testing, begin.

For Li Xiaofeng, if all goes well, by 1950, he will be able to obtain missiles capable of dropping atomic bombs with a range of more than 8,000 kilometers (preliminary estimates), which is crucial for the future national security and international influence of the Soviet Union. (To be continued.) )