Written by Aleksandr Shirokopad; Originally appeared at Zvezdaweekly, translated by AlexD exclusively for SouthFront
For the first time in history a projectile with an air-jet engine was demonstrated in 1942
For many years now, designers have been working on any creative tricks to increase the firing range of the 152-155-mm guns if only by one kilometre. One of the novelties that caused furor at the international exhibition Eurosatory in June 2018 in Paris was the layout of a 155-mm artillery shell with a direct-flow air-jet (DFAJ) engine, presented by the Norwegian-Finnish company Nammo. The new DFAJ projectile can easily overcome both the 120 and even the 150-kilometre barrier. With it, the conventional 155-mm howitzer can solve tasks that are feasible for tactical missiles corps and even front-line command.
Novelty? Here I remember the comical situation of 50s and 60s, as told to me by employees of at least three design offices. The director at the solemn meeting: “Our design bureau is the first in the world to create it…” A storm of applause in the hall. He is repeating the same phrase at the evening banquet. And then instead of applause there is a snide question: “Did the Germans have any?”
Alas, here the Germans were the first. Work on the active rocket projectiles began in Germany already in 1934. In 1938-1945, several types of projectiles of up to 280-mm in calibre were supplied with miniature jet engines. For example, in 1939, the R.Gr.19 150-mm active-jet projectile was developed for the 18 and 18/40 heavy field howitzers. After tests, the projectile was adopted for service.
And in 1936, the engineer Wolf Trommsdorff suggested replacing the powder accelerator with a shell… with an air-jet direct-flow engine. In 1942, the shell with liquid fuel, which was a mixture of carbon disulphide and diesel fuel, was tested. The oxidiser was naturally atmospheric oxygen. The projectile flew at 920 m/s, which is about 3 mach. This is the first time in history that a supersonic jet engine flight has been demonstrated. Trommsdorff did not stop there and developed shells for 105-mm (E2), 122 (E3) and 150 (E4) calibers during the Second World War. The latter developed a speed of up to 4.5 mach, using the same carbon disulphide as fuel.
In 1943, the C1 projectile was created for a 210-mm cannon. Of the 90 kg weight of this shell, 6 kg were accounted for by rocket fuel. Thanks to the direct-flow engine, the speed of C1 reached 1,475 m/s, with a range of 200 Km.
Dr Trommsdorff’s most powerful projectile was the 28-cm C3 for the K5(E) railway cannon. The weight of the projectile was 170.4 kg, the weight of the rocket fuel was 16.3 kg, and the weight of the explosives was 9.6 kg. The straight-through motor was accelerating the projectile to a speed of 1,860 m/s. The maximum firing range was 350 km, i.e., longer than that of the V-2 ballistic missile and the V-1 cruise missile. Thus, the K5 cannon could have fired on London from France.
In May 1945, Trommsdorff found himself in the Soviet occupation zone. The Soviet authorities created two missile institutes in the deepest secrecy: “Berlin”, on the premises of the Berlin Gema factory and “Nordhausen”, at a base created by a group of Soviet specialists headed by B.E. Chertok from the Rabe Institute in Bleicherode.
The main task of Design Bureau 4, which was part of the Research Institute “Berlin”, was to finish the Trommsdorff shell. N.A. Sudakov became the head of the Design Bureau, and Wolf Trommsdorff himself became the leading designer. They were to complete the development of the technical design of the 283-mm direct-flow jet projectile, to produce working drawings of the projectile, drawings of models for bench tests and to make them, as well as to produce samples of the projectile and test them in the period from October 1946 to early 1947.
According to the staff there were to be 36 German and 21 Soviet specialists in Design Bureau 4, but in fact in July 1946 there were 17 Germans headed by Trommsdorff and 4 Soviet specialists. By mid-August, two more Soviet specialists had joined the ranks.
The author could not find out how Trommsdorff’s work in Design Bureau 4 ended. It is only known that Design Bureau 4 had performed only the following works: the technical design of the projectile with the DFAJ was developed, the drawings of the models of the projectile and three models for blowing in the supersonic aerodynamic channel were made.
Someone started a rumour that the designer was killed in a plane crash of the Soviet military transport aircraft at the end of 1946. The rumours, of course, did not go through the secular salons of Moscow, but in the secret missile design bureaus. Later, it became know that in 1956 the seriously ill Trommsdroff moved from the USSR to Germany and died the same year.
Why were shells with the DFAJ not adopted in the USSR? It took quite a long time to create them. But in 1955, Khrushchev forbade all work on the creation of long-range artillery.
Thus, for example, at the end of 1955 the production of the world’s long-distance cannon S-23 was stopped, and four years later Khrushchev shut down the leading artillery design bureau headed by V.G. Grabin.
However, the DFAJ projectile experiments were useful in February 1958 during the design of the 3M8 (Krug) surface-to-air missile equipped with DFAJ.
It is a very promising case
And now 75 years later, the Norwegian-Finnish company Nammo has installed a direct-flow jet engine in a 155-mm shell under the Extreme Range programme. The minimum initial speed of 2.5-2.6 mach is required for the DFAJ launch, and the muzzle speed of a 155-mm shell fired from a howitzer with a barrel length of 52 calibre is 3 mach.
The direct-flow motor is a self-regulating motor that maintains a constant speed regardless of the flight altitude. The speed of about 3 mach is maintained for about 50 seconds, while the traction is provided by NTR3 fuel (hydrogen peroxide concentrate) with additives. The advertisement says that the range of the DFAJ projectile exceeds 100 km.
Nammo plans to conduct the first ballistic tests in late 2019-early 2020. Since the increased range results in an increase of an order of magnitude in the circular probable deviation, Nammo is working with a number of companies in parallel to the GPS/INS guidance system for this projectile.
It would be interesting to know where the Norwegians will place the homing head. Fortunately, it is impossible to place it in the nose near the air inlet.
It is clear that the weight of the DFAJ explosive will be significantly lower than that of a standard 155-mm projectile. So, Nammo said that the weight of the warhead “will be about the same as in a 120-mm shell”. In accordance with the requirements of the Norwegian Armed Forces, Nammo plans to start serial production of this projectile in 2024-2025.
The development of the corrected 152-155-mm DFAJ projectiles is very promising. However, the designers will probably have to face a number of problems. Among them is the uneven operation of the DFAJ in flight, the impact on the engine of large overloads in the barrel channel, and, most importantly, the higher cost of such a DFAJ projectile compared to standard ammunition.