As you know, the speed of experienced fighters in the early 1940s exceeded the 700-kilometer line, and its further growth was restrained by both insufficient power of the piston engine and a propeller. For the further progress of the Soviet aviation a turbojet engine was required, but it just did not exist, just as there was no light piston engine with a power of more than 2000 hp.
At the same time, there was a certain groundwork for the development of liquid-jet and direct-flow engines (pulsating WFDs appeared later, after the Soviet Union received the captured German materials). These circumstances led to a revival of the idea of designer A.Ya. Shcherbakov on the combined power plant of the aircraft (piston and jet engines). First of all, LREs were considered as accelerators, since very problematic ramjet engines required additional research and development.
Certain hopes were pinned on the LRE RD-1, developed in the Kazan Special Department of the NKVD under the leadership of V.P. Glushko and tested on the flying laboratory Pe-2 with the participation of the joint venture. Queen. The basis for the development of combat vehicles with a combined power plant was the resolution of the GKO from 22 May 1944. According to this document, along with the planes of other designers it was proposed to install the RD-1 on La-5FN. With standard La-5FN armament, the maximum speed of the semi-reactive fighter should have been at least 780 km / h at an altitude of 7000 meters. It should have climbed 5000 meters in 3 minutes (the time of LRE operation) with the range on the main engine - 300 km. The aircraft was required to be built in triplicate, with the first by September 1944 of the year, and the last, with a laminar wing profile, by January 1945 of the year.
Work in this direction began almost simultaneously at the branch of the OKB Lavochkin (Plant No. 81), organized in accordance with the NCAA's order from 22 March 1944, on the territory of the Moscow Plant No. 381, and in Kazan under the supervision of SM. Alekseeva and SP. Queen respectively. Korolev, having taken the La-5FN as a basis, proposed two variants of the “VI” high-altitude fighter: one with three RD-1 LREs installed in the fuselage and wing consoles, and the other with one three-chamber RD-3. According to Sergei Pavlovich, for “VI” it was required to increase the wing area, install a pair of turbochargers TK-3 and four machine guns of the sun X XUMUM caliber mm.
It was expected that the speed increase of the first version of the fighter will be 100 — 140 km / h, and the second — 215 — 290 km / h, the ceiling will increase by 4000 and 6500 m, respectively. In this case, the duration of the flight at an altitude of 14 km using a piston engine will be within 15 — 20 minutes. But all these projects remained on paper.
At the end of 1943 of the year, the Moscow branch of the design bureau urgently began to refine the La-7 under the liquid-propellant rocket engine V.P. Glushko. The first La-7-1 was built in October, 1944, at plant number 381. In its tail part there was a LPD RD-1, created under the direction of V.P. Glushko, with a pumping system for supplying fuel components driven by the main engine ASH-82FN. The oxidizer tank, containing 270 kg of nitric acid, was located in the center section, and the fuel (60 kg of kerosene) was in the right wing console. At the same time, the supply of gasoline was reduced to 210 kg. The rocket engine control was carried out, like the ASH-82FN - with the help of the gas sector lever and the starting valve (valve).
Factory tests La-7-1 began in late October. A few days later (tentatively at the beginning of November) test pilot A.V. Davydov performed on his first flight. The pace of testing can be judged by the fact that before 24 February 1945, only 15 flights took place, five of them with the inclusion of LRE, after which the aircraft needed repair.
Engine reliability left much to be desired. The reasons for this were enough. First of all, despite the use in the power plant of such acid-resistant materials as pure aluminum and its alloys, as well as stainless steel, aggressive acid, falling on some units and assemblies, mercilessly corroded them, resulting in disrepair.
Flight tests of the La-7-2 with the RD-1 engine began on 26 on January 1941 of the year and continued until March on 27. During this time, 19 flights were performed with an engine equipped with air-to-air ignition. Within two months, the LRE launched 45 times, six of them - in the air, and only two flights made platforms with the removal of the characteristics of the machine.
From 45, the RD-1 launches failed 15 times, of which six were caused by ignition, the combustion chambers changed twice.
The maximum speed increase was about 95 km / h at an altitude of 2600 m. The tests ended on March 27 with a LRE explosion. On that day, the plane, piloted by G.M. Shiyanov, at the height of 6000, the auxiliary engine did not start. Having declined to 3000 m, Georgii Mikhailovich tried again, but an explosion was heard, apparently because of the components of the fuel that had accumulated in the combustion chamber. The elevators suffered the most from the explosion, from which only the rags remained. Slightly better looked steering wheel.
But trouble does not come alone. The cockpit of an almost uncontrollable aircraft was filled with poisonous nitric acid vapors. Only by a miracle the pilot saved the wounded car. More than two weeks it took to repair the La-7Р-2, but the LRE, modified during this time, still did not want to run at high altitudes. Only the use of RD-1 HZ with chemical ignition allowed the launch problem to get off the ground, but it was not possible to increase the reliability of the LRE.
Understanding the failures with this engine was only possible by the middle of summer, and from July 11 to November 16 1945 completed 14 flights on La-7Р-2. During this time, four combustion chambers and two pumps were changed, 49 start-ups were made, eight of them were in the air. LRE refused to 23 times, of which the fault of the ignition - twice. In five flights, it was possible to perform horizontal platforms with the removal of the aircraft’s speed data. In particular, they registered the maximum speed of 795 km / h at an altitude of 6300 meters. However, it was not possible to make a combat vehicle with LRE 7 from a wooden one.
In the 1945, the “120” aircraft was the faster and therefore the preferred fighter for installing the LRE. However, before installing the RD-1HZ on it, the car had to be thoroughly repackaged and completely replaced the tail part of the fuselage with plumage. In particular, the tank with the oxidizer, as well as on the La-7P, was placed in the center-section, and one of the guns HC-23 was replaced with B-20. The motor AL-83 for centering was shifted forward by 70 mm. Moved to other places battery, oil tank and air tank. There were other, smaller changes.
The “120P” tests were held in parallel with the tests of the La-7Р-2. In addition to fine-tuning the LRE had to tinker with the refinement of the fuel and oil systems of the fighter. Virtually all of the semi-reactive OKB-301 fighters have become flying rocket engine testing laboratories. Even on the last car of sixteen flights with a working rocket engine could only make seven. In one of them, the speed of 725 km / h was recorded, receiving a gain of 103 km / h.
The third aircraft built was a semi-active La-7Р with a single-chamber LRE LS Dushkina RD-ZV. The car was ordered to pass on flight tests in August 1945 of the year, but documents that shed light on its biography could not be found.
Culminating in stories with "120P" became the flight of the pilot A.V. Davydov at the air festival in Tushino in 1946. The “120Р” flights ended on August 13, when due to the ignition of a mixture of fuel components in the engine compartment, the tail rotor of the fuselage and tail unit burned. By this time, the ASH-83 resource was almost exhausted, and the airframe was spoiled by nitric acid.
Thus ended the biography of the 120 aircraft, but the idea of using the LRE on the aircraft was not buried. There were no fighter jets in the Soviet Union yet, and the threat from the capitalist world was so great that in order to fight the potential enemy bombers, it was necessary to continue the development of fighters with a combined power-plant.
The last attempt to create an aircraft with the LRE was a project of an all-metal fighter "130Р" with an ASH-82FN engine based on the projected La-9. The layout of the aircraft largely repeated the predecessor - “120P”: in the tail section was installed LRE RL-1HZ, tank with oxidizer - in the center section, and with kerosene - in front of the cockpit. In order to preserve the required reserves of stability and controllability, they increased the area of the tail, and the steering wheel cover and heights were replaced by metal. Of the weapons left only two guns NA-23 with 160 ammunition ammunition. There were other differences from the 130, due to the installation of the auxiliary engine.
In this form, the aircraft began to be built at the experimental plant OKB-301, but in 1946, this topic was closed, though not quite. Ten years later, LRE tried to use interceptors with TRD. But even at the end of the 1950s, when the LRE seemed to be brought on, their “indomitable temper” continued to be felt. In aviation, the “services” of rocket engines had to be abandoned once and for all, except for the American space shuttle vertically taking off. But that's another story.
Between the past and the future
Alternative to LRE could be direct-flow engines (ramjet). Unlike the former, they did not need an onboard supply of oxidizer. If we consider that these liquids (with the exception of liquid oxygen) are very aggressive and toxic, then the operation of the WFD is greatly simplified. In addition, the overall weight of the power plant and fuel decreased, and the duration of the flight increased. But the "forward flow", ready to be installed on the aircraft, was not yet, and those that existed required a long tune.
During the war years, small design teams led by I.A. Merkulov and M.M. Bondaryuk. The first was practicing DM-4 on the Yak-7B fighter, and the BD-1 WFD-3 was to be investigated on the LaGG-1942 flying laboratory of the 105 release of the year with the M-XNUMXPF engine.
I don’t need to stop on the principle of operation of the ramjet, I think it’s not necessary, it is described in literature sufficiently. Note that the studied WFD-1 had a length of 2,15 meter and a diameter of a diffuser 0,14 meter with a weight of 16 kg. About the magnitude of the engine thrust is not known, but recall that it is directly related to the velocity of the air at its entrance.
Before the start of flight tests, the ramjet engine was tried several times on the ground, using another LaGG-3 as a fan. However, the unevenness of the airflow velocity field and the insufficient velocity head allowed to do this only twice, and it was not possible to determine the engine parameters.
Flight research of the engines, which took place in August 1942, was carried out by test-pilot GA. Mishchenko. The speed increase when turning on the ramjet engine turned out to be small, about 15 km / h. Since the task of obtaining maximum speed was not set when the ramjet was turned on, there were no requirements for the aerodynamics of its attachment points to the wing, which “ate” 35 — 40 km / h. The flights showed that before installing a ramjet on a combat aircraft, it is necessary to ensure stable combustion of the fuel with automatic control of the composition of the mixture and the launch of ramjet at high altitudes.
Research and development of the Pndr-430 Bondaryuk engines (WFD-430 with a diameter of 430 mm) was delayed for almost two years. In the spring of 1944, the first option was to install a pair of such engines on an 120 aircraft, and then on the 126 fighter, designated as 164.
Flight tests last began in June 1946. For two months with a little A.V. Davydov and A.A. Popov made a flight on the 164 34 aircraft and in 30 of them launched a ramjet. The reliability of the improved engines, though increased, but they still malfunctioned and required
vodka. At the same time, improving the aerodynamics of the junctions of direct-flow engines with a wing, together with their increased pressure, made it possible to increase the speed increase compared to an aircraft with a disconnected ramjet engine to 104 — 109 km / h, depending on the flight altitude. In relation to the aircraft without additional engines, this increase was within 62 — 64 km / h.
Compared with the flying laboratory LaGG-3, this was significant progress, especially since it was possible to slightly reduce the drag of the combination of the wing and the power plant. The simplicity of operating the machine was very captivating, and the flight characteristics with operating accelerators remained, as with the 126 aircraft. All this led to recommendations for installing the WFD-430 on the promising fighter "130", which later received the designation "138". In accordance with the resolution of the Council of Ministers of the USSR, the 138 aircraft was supposed to reach a maximum speed of 660 km / h (590 km / h with disconnected ramjet) and 760 km / h at 6400 m (660 km / h - without ramjet), recruit 5000 m in 6 minutes. At the same time, its range must be at least 1100 km in flight at an altitude of 1000 m, and the takeoff and run length must be within 450 meters.
The aircraft was still on paper, and in May 1947 of the year, by order of the ministry, they were obliged to participate in the Lavochkin air parade to complete the flight testing of two copies of the 138 aircraft and to prepare them for July 27. At the same time, the plant manager No. 21 was also instructed to equip ten more La-9 with RD-430 jet accelerators.
The weight of an empty aircraft with constant gun armament increased by almost 200 kg.
An attempt to combine the piston range and speed of jet fighters in the 138 aircraft did not produce the desired result. The range really turned out to be quite good, but the speed left much to be desired. According to the calculation of the “direct flow”, Bondaryuk developed 220 kgf thrust near the ground at an air flow velocity of around 700 km / h. In fact, it was smaller because the 138 was not flying at that speed. Compared with the La-9, the speed at 3000 meters increased only by 45 km / h, although 70 — 100 km / h was expected to be added, but when the ramjet was turned off, it turned out to be 60 — 80 km / h. With all the engines running, the flight range did not exceed 112 km (with normal flight weight), and the duration was 10 minutes.
Factory flight tests of the 138, which ended in September 1947, showed that the 138 fighter could fight the B-29 and B-50 bombers, including during pursuit. But in a duel with enemy fighters, both piston and jet, his chances were slim. And although the ramjet engine remained in the experimental discharge, the experience gained during their design and fine-tuning was not lost and was subsequently used to create more powerful engines, including the La 17 unmanned target.
Another direction in the development of combined power plants was the use of two pulsating air-jet engines (DFD), D-9 and D-10, designed by VN on the La-13. Chelomey and intended for cruise missiles (in the terminology of 1940-ies - projectiles), analogues of the German V-1. It’s hard to say whose idea it was and what the authors intended for it. As opposed to ramjet engine, as the speed increases, the thrusters drop and you can only expect a political effect associated with the enormous noise level generated by their work.
The D-10 engines of 200 kgf each were first equipped with training trainers La-7. The first stage of the factory tests, which ended in August 1946 of the year, showed that at 3000 m height, the speed increased by 119 km / h compared to a machine with non-operational RFID. In this case, the maximum speed could not be determined due to the limitations on the velocity head associated with the strength of the aircraft. Yes, and the plane due to disrepair soon written off, continuing research on all-metal La-9. But at the same time, the D-10 engines equipped three Sparky 7 launchers, intended for the 1947 air parade of the year. But the taxpayer never saw them. In November, the 1945 year of testing continued.
The leading pilot for this car was N.V. Gavri-lov. But things did not go beyond the experiments.
Especially for the La-9 plant number 51 produced modified engines, received the designation D-13. The same company equipped them with 12 fighters. Additional engines were suspended on pylons attached to reinforced ribs of wing consoles. At the same time, the aircraft fuel system was modified, the horizontal tail and the mounting of the piston engine hoods were strengthened. At the same time, they removed the armor support and two guns, and to maintain the centering, they attached an 82-kilogram load to the ASh-60FN gearbox. Made a number of changes in the equipment of the machine.
In this form, the La 9 group was shown to the country's leadership and the public in Tushino 3 August 1947. Pilot test aircraft pilots NII VVS VI. Alekseenko, A.G. Kubyshkin, L.M. Kuvshinov, A.P. Manucharov, V.G. Masich, G.A. Sedov, P.M. Stefanovsky, A.G. Terentyev and V.P. Trofimov.
After the air parade, one of these dozens of La 9 (La 9РД) was tested at the Air Force Research Institute from November 21 1947 to January 13 on 1948 of the year. The leading test pilot was I.M. Dziuba Flew over the car and test pilot Olga Vladimirovna Yamshchikova. The increase in speed when the auxiliary engines were turned on in comparison with the “clean” 9 X-LUM made 70 km / h, while the installation of the PU-RND “eaten” to 57 km / h. The pilots noted strong vibrations and noise when turning on the scramjet. Engine mounts worsened the maneuverability and take-off and landing characteristics of the aircraft. Engine start-up was unreliable, the duration of the flight was sharply reduced (due to the high specific fuel consumption of the HRVD), operation became more complicated.
The work carried out benefited only in the development of engines intended for cruise missiles. Airplanes, participating in air parades, their roar made a strong impression only on the public.
In 1943, TsAGI considered several variants of fighters with motor-compressor air-jet engines (VRMC). Among them was La-5ВРДК, but he, like all the other projects proposed by the institute, only paved the way for the P.O. Sukhoi and I-105 A.I. Mikoyan.
Thus ended the story with the half-reactive fighters S.A. Lavochkin, gone in the past with piston engines. And the planes themselves were on the border between the past and the future of aviation.