Nelson thought for a moment and said, "By the way, Tony, show Mr. Philip our inner chamber structure design to see what problems are still there, and solve them all together." ”

The twenty-five-six-year-old designer hurriedly found the design of the bore structure of the 30 mm barrel of the Vulcan cannon from a thick pile of drawings, and then cautiously walked over and handed it to Philip.

Philip looked down, although some of the design is not too reasonable, but the whole design drawing is very fine, the rigorous work attitude of the Germanic people has been very obvious here, you must know that the drawings of this era are all using relatively primitive tools, compared with the later computer-aided design, I don't know how many times more complicated, and every detail of the drawings must be drawn by hand, sometimes even need to be modified many times to meet the requirements.

Philip couldn't stop nodding while looking at it: "Mr. Nelson, it seems that the basic work of our R&D center is still very good!" Although there are still some problems in the design, from the drawing of the design drawing, our R&D center has reached a very high level. From the point of view of the design of the rifling, I think there are still some problems, you choose the relatively simple process of equal rifling, which is more beneficial to shorten the development time and mass production in the future, but the angle of equal alignment rifling is a constant, which is equivalent to expanding the inner chamber into a plane, and the rifling becomes a straight line. Of course, its advantage is that it is easy to process, but the disadvantage is also quite obvious, when the projectile moves in the chamber, the force of the guide belt acting on the rifling guide side is relatively large, and the change law of this force is the same as the change law of the chamber pressure, that is to say, the maximum force is close to the starting part of the rifling with the most serious ablation wear, which has a very adverse impact on the life of the body. ”

Nelson smiled bitterly: "Philip, we can't help it!" At the current level of technology, it is difficult to process complex rifling. ”

Philip looked up, thought for a moment, and said, "You can use a hybrid rifling design." In addition to the equal rifling, the gradual rifling is indeed very complex in the manufacturing process, because its entanglement is a variable, the entanglement angle in the initial part of the rifling is very small, or even zero, and gradually increases in the direction of the muzzle, and the design is also more complicated, it needs to use different curve equations to adjust the force on the rifling guide side, which reduces the initial winding angle of the starting part, which is conducive to reducing the wear of the rifling in this part, but it is indeed very complex in the manufacturing process. However, we can completely absorb the advantages of equal rifling and mixed rifling, that is, the gradual rifling is used at the beginning of the rifling, and the equal rifling is used at the mouth, so that the shape of the rifling becomes composed of a curve and a straight line, which can not only reduce the wear of the starting part of the rifling, improve the life of the body tube, but also greatly simplify the manufacturing process than the gradual rifling, and can completely realize batch manufacturing. ”

Nelson patted his head and suddenly realized, "yes, why didn't I think of that!" Philip, tell me what else you have to ask, so let's change the design immediately. ”

Philip looked at the designers who were listening intently and continued: "There are many factors that affect the life of the barrel of the gun, including the design of the barrel, the design of ammunition and the design of the outer trajectory. For example, when designing rifling winding, it is necessary to meet the requirements of service life and ensure the requirements of external ballistics for muzzle winding, so it is necessary to choose a reasonable rifling structure and rifling curve equation. The basic task of rifling design is to determine the winding degree, which is an important parameter that directly affects the flight stability of the shell, and the muzzle winding degree needs to be determined in combination with the external ballistics and the shell design. After the rifling type is determined, it is necessary to select the width, depth and number of rifling, as a high rate of fire automatic cannon such as a rotary tube gun, the depth of the rifling should be 1 percent to 1 percent of the caliber, for example, our 30 mm Vulcan cannon, the depth of the rifling can be 0.3 mm, and the number of rifling should be a multiple of 2, preferably 4 or 8. ”

Philip exclaimed, "It's not so easy to design a good rotary tube gun! The longevity of the barrel alone is a big problem. This is especially true of the high rate of fire, the high temperature, high pressure gunpowder gas and the repeated action of the projectile guidance part on the body barrel during firing cause the ablation and wear of the rifling, once the projectile reaches the abnormal forward movement speed and rotation speed, the body tube is scrapped. ”

Due to the large gap between the level of materials and manufacturing technology in this era and later generations, Philip also knew that there were still great difficulties in making the Vulcan Cannon achieve a higher life, and first of all, it was necessary to work in the direction of improving the life as much as possible in the design. Due to the use of wear-resistant materials, the 20mm caliber M61A2 "Vulcan" aviation cannon of the United States has good cooling, thermal erosion resistance and wear resistance of the barrel, which improves the life of the barrel to more than 20,000 rounds. As for Bofors' Vulcan cannon, Philip estimates that it is already a miracle that it can reach a life of 10,000 rounds.

Of course, the overall life of the rotary tube gun is definitely longer than that of a normal rapid-fire gun. Because the life of small-caliber rapid-fire guns is prominently reflected in the ablation and wear of the barrel and the fatigue breakage of the stressed parts. The rotary tube gun solves this contradiction very well, because it uses multiple barrels and multiple sets of cores to bear the total number of projectiles, which is much longer than the full gun life of single-barreled or double-barreled small-caliber rapid-fire guns. Moreover, due to the use of external energy power, the rotary tube gun will not stop firing when encountering blind fire, and the failure rate is an order of magnitude lower than that of ordinary small-caliber rapid-fire guns, because its various shooting cycles are all mechanically mandatory, and the reliability is obviously much higher than that of automatic guns driven by gunpowder gas.

Nelson said happily: "Philip, you don't have anything to say now!" Just now you said that you only know a little bit about the surface, but you have solved the biggest problem we encountered in the design, so let's tell us what problems need to be paid attention to in the shell design of the rotary tube gun, so that we can also make design modifications together. ”

Philip put the drawings on the table and said confidently, "Not bad! If there is only a good launcher, but not a good shell, then this artillery weapon is also a failure. The design and calculation of artillery shells are closely related to the design of the barrel, and they must be put together for system design. Because when the shell is fired, the warhead moves along the chamber and bears a variety of loads, under the action of these loads, the parts of the warhead will be deformed, especially for the shells equipped with complex precision fuzes, these deformations must be controlled within a safe range to ensure safe launch and effective action on the target. If the gap between the projectile and the cannon and the size of the cartridge belt are properly designed, the projectile dispersion of the warhead can be improved and the life of the body tube can be improved. ”

Tony eagerly asked, "So what fuse should we use when designing anti-aircraft shells?" Is it better to trigger the fuse or the mechanical time fuse? ”