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Korolyev RP.218 / RP.318
The RP-318 or RP-318-1 was Russia's first rocket-powered aircraft or Rocket Glider (Rocketny Planer or Raketoplan) which "RP" stands for in Russian language. Beginning in early 1936 it was firstly known as RP-218-1 or "Objekt 218" before it was changed to RP-318-1 in 1938 due to inner reforms of Rocket Science And Research Institute.
According to the proposal of Marshall Tukhachevsky the Revolutionary Military Board established on 21 September 1933 a brand new institution – RNII. The activities of the new institute began on October 31 by merging of GDL and GIRD. In the beginning the works on a rocket-glider were not a part of RNII activities and also the development of rocket engines using a liquid propellant was also not in the focus of activities - the main activities were focused on military rockets, using solid fuel.
He understood well, that the idea of creation of the rocket plane simply by putting a rocket engine into usual airframe was wrong. He stressed, that there are differences in flight characteristics, trajectories and weights. The development of necessary airframes could be possible on condition, that there was a reliable and powerful rocket engine. These conclusions he pointed at the conference about utilizing of rocket-powered aircraft for use in the atmosphere, which was held on 2-3 March 1935 in Moscow.
The chief designer was S.P.Korolev and his deputy was E.S.Schetinkov. The original design was a single-seater and a pressurised cabin was not in consideration, instead the pilot was provided with a space suit. The empty aircraft was to be very light: 240kg airframe, 200kg fuel system, 200kg compressed air system (used for life support and to displace fuel components toward the engine), 50kg for engine. The rocket engine should have thrust of 19.6kN and the take-off should be assisted by solid fuel boosters. After a steep climb (at angle of 60°) to an altitude 32km, and the aircraft would glide at the speed of up to 2500km/h, covering 220km in 18min.
Some changes were introduced in the design. Now it was a two seater, high-altitude experimental aircraft with pressurized cockpit, equipped by a rocket engine (developed by the 1st department of liquid rocket engines, managed by V.P.Glushko). It was obvious that such a complicated aircraft can not be successfully built without simpler manned technology demonstrator. S.P.Korolev was ready for this: he already built a strengthened glider SK-9, specially intended to fly with a rocket engine. On June 16 1936 the board of RNII decided to proceed with a “supplement" to the Object 218. It would be an experimental aircraft equipped by a low-output rocket engine, named RP-318, essentially a SK-9 fitted with ORM-65 engine and fuel system. The engine selected, Glushko’s ORM-65, a nitric acid/kerosene engine capable of generating between 50 and 175 kg of thrust, was already under development for the 212 winged missile.
Built in 1936 by Sergei Korolev as an adaptation of his SK-9 glider, it was originally designed as a flying laboratory to test rocket engines and ORM-65 (RDA-1-150) designed by Valentin Glushko was the one selected to be used. Arvid Pallo took the work on installation into the SK-9 rear fuselage, and the tanks for nitric acid and kerosene occupied the former rear cockpit. The whole powerplant weighed 136.8 kg, the fuel 75 kg. The engine could run for 112 seconds. Ground fire tests began at February 1939, until October more than 100 firings were done.

In late 1938, when both Korolev and Glushko were arrested in suspicion of Anti-Soviet activity, new RNII Director B.M.Slonimer transferred the "Rocket-Glider" project with remains of the team to the new department (head - L.S.Dushkin). A.V.Pallo was put in charge for the RP-318. Development of the RP-318-1 was continued by Alexei Scherbakov (Щербаков, Алексей Яковлевич) and Arvid Pallo (Палло, Арвид Владимирович), culminating in the first powered flight on Feb. 28, 1940 by test pilot Vladimir Fedorov. The rocketplane took off towed by a Polikarpov R-5; at 2800 m altitude it released, Fedorov set up 80 km/h speed and then fired the engine. After 5-6 seconds the speed increased to 140 km/h; Fedorov established climbing flight with 120 km/h speed and held it during all time the engine worked (110 seconds); he climbed 300 m during this time. The speed increase after engine start was smooth, vibrations didn’t appear. On March 10 and March 19, 1940 two more successful rocket flights were performed.

As it already occur several times in Soviet pre-WWII history, purges and re-organizations added new problems. RNII lost its Flight-Trials Grounds. There were no more experienced test-pilots (S.P.Korolev was in prison). It was necessary to find an organization within Aviation-Industrial complex capable to carry out flight trials of the aircraft. Help came from the OSK Factory N°1 NKAP. A.Ya.Scherbakov, head of the OSK was involved with "Project 218" as a designer of pressurized cabin. Glider-pilot V.P.Fedorov was invited as a test-pilot. The aircraft was carefully evaluated. Tail section (damaged by acid) was rebuilt. New landing ski was installed. Rigid tail skid got a shock absorber. New cowling for fuel tanks was developed.
Flight trials of RP-318-1 (designation of rebuilt RP-318) took place in November-December 1938 towed by R-5 biplane (pilot Fikson). The engine was replaced by its weight equivalent. First three flights were dedicated to the center of gravity studies: with empty tanks, 50% of fuel, 100% of fuel drained gradually to imitate its consumption by the engine.
After those flights RP-318-1 was installed in the L.S.Dushkin laboratory for engine installation and trials. Soon several problems with the ORM-65 engine were revealed. First of all, there were only three ORM-65s built, and two of them were allocated to the "Project 212" winged rocket (cruise missile). This brought some limitations on use of the engine for a RP-318: no provision for multiple start, overheating of the engine head, few unreliable sealings. Acceptable for a missile, ORM-65 needed to undergo serious modifications before it could be used on the manned aircraft.
Modified engine was designated RDA-1-150. It was 2kg lighter than the ORM-65, had improved cooling system. Number and design of injectors was changed. Intermediate 'starter' engine regime (fuel flow at 8...10% of normal) was introduced for the first time. Monitoring of the engine operation was improved. Though still very basic, it was a step forward from couple of ORM-65's wires burned by flames and disrupting the electric current to lights on the pilot's instrument panel.
Experiments with multiple ignition (additional air-hydrogen burner with electric start) were successful, but tight design limitations of the RP-318-1 created problems for its installation. Total number of engine firings was more than 100, including 16 after installation on the RP-318 (July 21, 1939). On October 3 A.Ya.Scherbakov sent to People's Commissar of Aviation Industry a request for permit to fly RP-318-1 with the rocket engine fired.
KB-29 NKAP airfield at Podlipki (Moscow Region) was chosen for trials. In November 1939 the aircraft was installed on the edge of the field, partly covered by birch and fir trees. The team had to perform systems tune-up and to work with kerosene and concentrated acid under deep freeze conditions, with very basic fuelling equipment and rudimentary accommodations: wooden package box used to transport the aircraft served as a "field laboratory and workshop".
More on-ground firings were performed and all were successful, but on January 3, 1940 supervising commission ordered more unpowered flights and demanded to perform more study of the airframe shape (the wooden SK-9 glider had been built in 1935). No damage or degradation of wooden parts were revealed, but speed was restricted by 150km/h.
Test pilot V. P. Fedorov (Владимир Павлович Фёдоров) was towed to 2,600 m and cast off at 80 km/h before firing the rocket engine and accelerating the aircraft to 140 km/h and an altitude of 2,900 m. In all, the RP-318 flew nine times before World War II ended development.
First flight with rocket engine fired at full power took place on February 28, 1940. It took since early morning until 5 p.m. to prepare the snow-covered airstrip, fuel the RP-318-1 (40kg of acid and 10kg kerosene), fill the nitrogen bottle to 130kg/m2, and check the fuel system for leakage absence. Flight crews were in cockpits: N.D.Fikson as a pilot of the R-5, A.V.Pallo as an observer and A.Ya.Scherbakov as a tag winch operator - in the rear cockpit of the R-5. V.P.Fedorov - pilot of the RP-318-1.
At 5:28 p.m. both aircraft took off, and 31 minutes later at altitude 2800m RP-318-1 was released. It took some time for N.D.Fikson to bring the R-5 into an optimal position for observation, and at altitude 2600m V.P.Fedorov fired the engine. First, grey smoke indicated ignition of the powder charge. Shortly its place was taken by blurred flame with brown smoke showing that the engine is running in the 'start' regime. And, finally - spear-shaped bright flame near 1.5m long with little smoke.
After gradual acceleration of the RP-318-1 left the observers far behind, and all efforts of the R-5 pilot to keep up with the experimental machine failed. Once it was out of sight, N.D.Fikson, A.V.Pallo and A.Ya.Scherbakov turned back to the airfield to meet the rocket-plane during its landing.
From V.P.Fedorov report:
Start of the ZhRD was normal, the glider speed was 80km/h. In 5...6sec speed was increased to 140km/h. During following climb speed was reduced to 120km/h. Engine was working during 110sec. During the climb altitude increased from 2600m to 2900m. Climb rate was 3m/sec. Handling and stability of the rocket-plane with fired engine are good. Start of the ZhRD does not deteriorate handling of the aircraft. Acceleration is smooth. Noise in the cockpit from the ZhRD is not irritating is is more muffled than during ground trials. The feel of acceleration and flight with the ZhRD fired is more appealing than on a prop-driven aircraft with the engine boosted to maximum power.
On March 10 and 19 two more flights were performed without an accident. During those flights the engine start was filmed from the R-5 observer's cockpit.
Than the Spring came. Melting snow made the airfield unusable and delivery of the acid to the plane virtually impossible. No more flights were performed. In the Fall of 1940 the RP-318-1 was transported back to the RNII and disassembled.
It was planned to continue trials with modified RDA-1-300 engine. Plans included rocket-powered takeoff using jettisonable wheel cart. But this project was pushed aside by RAS and RDD rockets. In 1941 priority was given to RDA-1-1100 engine for Bolkhovitinov's BI rocket fighter.
In August 1941 RP-318 was burned. The Rocket Institute was preparing for evacuation, and old wooden airframe was worthless.
Powerplant: 1 × RDA-1-150 rocket, 0.98 kN (220 lbf) thrust 100 kgf
Wingspan: 17.0 m (55 ft 9 in)
Wing area: 22.0 sq.m (237 sq ft)
Length: 7.44 m (24 ft 5 in)
Empty weight: 570 kg (1,257 lb)
Gross weight: 700 kg (1,543 lb)
Maximum speed: 140 km/h (87 mph; 76 kn)
Range: 220 km
Endurance: 18min
Ceiling: 32,000 m
Crew: 1
Engine: 4900 to 9800kN
Loaded weight: 1600 kg
Endurance: 15 to 20min
Ceiling: 50,000 m
Crew: 2
Powerplant: 1x Dushkin RDA-1-150 rocket engine, 1500 N maximum thrust 
Wing span – 17.0 m
Length: 7.44 m
Wing area: 22 sq.m
Normal takeoff weight: 637 kg
MTOW: 700 kg 
Vne: 160 km/h (limited by strength reasons)
"Object 218" in late 2-seater configuration

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