"The propellants are fueled by ethanol (alcohol) and liquid oxygen, and they are introduced through the line in a certain proportion to the combustion chamber to burn violently and power the rocket, and because they are so dangerous, we usually only inject them before launch." Braun pointed to the sergeant in full protective clothing in the distance, "Once the rocket cannot be successfully ignited during launch, the professional sergeant needs to empty the liquid as soon as possible, otherwise it is easy to explode." ”

Hoffman frowned: "Sounds troublesome and dangerous, is there a better way?" ”

Braun shook his head: "We've experimented with a lot of fuels, and the current recipe is the most stable and efficient, and it's easy to obtain, but the disadvantage is that it's a little less safe." Maybe we'll find a better recipe in the future, but it will take time. ”

"There's no rush."

Major General Dornberg added: "Rocket propellant can be divided into liquid fuel and solid fuel, the A-4 rocket is a typical liquid fuel, and Rheinmetall-Bosg undertook the development project of multi-stage solid fuel rocket, according to the technical parameters its overall weight is about 1,700 kilograms, can carry about 1,200 kilograms of warheads, and the maximum range is more than 200 kilometers, we call him 'Rheinland messenger' internally." Compared with liquid fuel, solid fuel can make the missile body smaller, and it can also realize the storage of fuel for a longer time in advance, but it is more technically difficult and is currently inferior to the A-4 project in terms of overall progress. ”

Hoffman nodded, he knew the trend of rocket development: solid fuel later became mostly missiles, and liquid fuel switched to the task of launching satellites.

"Three minutes to prepare." Hoffman and others were introduced into a special observation trench at a distance where the state of the rocket could be fully observed and danger avoided, even if the rocket exploded on the spot, safety could still be guaranteed in this trench. Hoffman remembered the launch site and monitoring center he saw on the TV screen in later generations, and was very impressed by the power of scientific and technological development, but now the Penemünde base is the pioneer of the rocket industry for all mankind.

"One minute to prepare."

"Ready, launch!" The last 10 seconds of the countdown had not yet been introduced, and when the time was up, the technical sergeant next to Braun pressed the button heavily to activate the radio signal, only to see the huge A-4 rocket immediately spew blazing flames from the tail, reflecting half of the sky red, with a kind of earth-shaking roar, the rocket soared into the air, soaring faster and faster, drawing a track in the air and gradually disappearing from everyone's field of vision.

"At the tail end of the rocket is placed a metal plate called a gas rudder, through which it can change the air flow to induce the rocket to go in the right direction, and it can also be used to change the forward course." Braun said, "There are our observers near the scheduled landing point of the rocket, and they will pass the data on. ”

"How do you implement the guidance of the rocket? Or rather, how do you get a rocket to hit its target accurately? ”

Braun drew a schematic diagram that explains it in the most succinct terms: "The rocket is guided by inertia, climbs vertically or almost vertically after launching, and when the fuel is burned, the thruster pushes the rocket to a certain altitude and speed, which is about 80-100 kilometers above the ground in the air - that means that it has broken out of the atmosphere, and the rocket that has lost power will continue to shoot along the parabola at the apex of this altitude according to inertia and gravity." Due to factors such as air flow and wind direction, the moment received by the rocket during launch is not uniform, so it is difficult to ensure that the real range is consistent with the design range, we have installed a gyroscope on it for attitude adjustment, to ensure that the landing point will not deviate too much to improve the accuracy - we call it circular probability deviation, the current deviation is still about 5 kilometers, we are trying to install the rocket with the radio guidance method used on the aircraft, hoping to help reduce the hit error......"

Gerhard Degenkoby, Speer's right-hand man in the Ministry of Armaments, who had been in charge of the production of locomotives at Krupp and Henschel, had more than tripled the output of the two companies in half a year, and was now coordinating the production of tank armaments for the Third Reich.

"If the cost of development is not amortized, the cost of each piece is currently about 150,000 marks, and after mass production, the cost can be reduced to 120,000 marks or less." Braun couldn't say the question, but Major General Dornberg answered it for him.

Hoffman said noncommittally "um", but in fact he was pondering: 120,000 marks is equivalent to 1 tank No. 4, considering that more than 8,000 V2s were manufactured, if it was replaced by tank No. 4, it was only afraid that the Third Reich would have more than 10,000 tanks, and the results of the two seemed to be clear at a glance.

While waiting for the experimental data to arrive, Dornberg took Hoffmann and others on a tour of the next project, which was also a rocket project with the internal development number Fischler Fi-103 (V1 missile precursor), designed by a design team led by Robert Russel, an engineer at Gerhard Fisler AG in the Kassel region. The rocket body is spindle-shaped, with a mid-monowing design, the front main wing and tail are rectangular straight wings, with a maximum diameter of 0.82 meters, a wingspan of 5.3 meters, and a length of about 8 meters. Outwardly, it looks like an ordinary airplane, except that a barrel-shaped engine nacelle is mounted on the upper part of the vertical tail and connected to the fuselage, and a ramjet engine is installed in the cabin.

"This is the Argus Thrust Device, which fires on an inclined trajectory, is equipped with a pre-defined guide and guides the rocket in a specified direction, all the way through the atmosphere and not at a high altitude above the ground, which is significantly different from the A-4 rocket," Dornberg said, pointing to something like a chimney at the back of the projectile. The total weight of the rocket is expected to exceed 2000 kg, and the warhead section is designed to install Amato high-energy explosives of about 800 kg. Its advantages and disadvantages are equally prominent, the engine can only work at lower altitudes and repair and maintenance is difficult, and at the same time, the air intake flap is quickly penetrated by wear. But from the point of view of a single-use weapon, this seemingly rudimentary engine has great advantages: it is simple, inexpensive, has a high thrust (it can reach more than 270 kilograms), and it uses low-grade gasoline as fuel instead of valuable high-octane jet fuel. ”

"What about his speed and range?" Hoffman pointed to the body of the missile and said, "It looks like a small unmanned plane, I don't know what the advantage is over the plane?" ”

"There is no need for a pilot, it is faster than a conventional bomber, and it is cheaper to build - these are the three main advantages. Its cruising speed after launching is about 650 km/h, and the range is more than 240 km, if it is launched from the French coastline, it is more than enough to hit the south of England, and it may not be a problem to hit London. It's not that we don't install more fuel, it's because this engine only works for so long. "This project is progressing faster than the A-4 rocket, and is almost close to success, basically an unmanned jet that also relies on a set of gyroscopes to maintain flight stability, a magnetic compass to control the bearing, and an additional barometric altimeter to control its flight altitude." The current problem is to improve the stability of the flight attitude and the accuracy of attacking the target. ”

Speer asked, "What about its security?" ”

"It's more reliable and safe than the A-4 rocket, after all, there's only gasoline in it." Dornberg explained, "This one has been fueled, and we will show it to the Führer later, and its disadvantages are that it is not fast in flight, and the landing accuracy and flight attitude stability are not good, and we are still working on improving it." ”

At this time, the news of the successful launch of the A-4 rocket came: the rocket flew at an altitude of 96.5 kilometers, flew for a total of 296 seconds, flew a total of 201 kilometers during this time, exploded when it was still 4 kilometers away from the intended target, and the maximum speed before the explosion reached 5280 kilometers / h (about 4.8 times the speed of sound), which exceeded the speed of any known vehicle or even artillery shells, and everyone began to applaud, and at the same time was curious about the launch test of the second project.

Under the watchful eye of the observers, the test rocket, which was refueled and scrutinized in its entirety, lay quietly on a specially designed slide-rail wheeled launcher, waiting for the final launch command. It is a 48-metre-long wooden ramp-shaped launch frame that uses a steam catapult system with a piston slot in which dumbbell-shaped pistons are inserted during launch, and the rocket is placed into the piston groove by a trolley and secured with safety pins to prevent it from slipping out. The system consists of a reactor chamber and two chemical tanks: hydrogen peroxide (HO) and potassium permanganate (KMnO4) particle catalysts, respectively, which are connected by tubes to the tail end of the piston tank at the bottom of the launch frame. During launch, hydrogen peroxide is extracted from potassium permanganate, and a chemical reaction occurs in the reaction chamber and a large amount of hot vapor is generated, which accumulates neatly to a certain pressure, which will push the dumbbell-shaped piston to make the trolley move forward quickly to ensure that the rocket obtains a valuable initial velocity.

The interesting launch process is about to begin.