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First ramjet rocket blasts off
In May 1939, a group of Soviet engineers leaped decades ahead of their time with a rocket propelled by a futuristic jet engine.
Previous chapter: Rocket 212
Above: A VR-3 rocket is being prepared for launch at the beginning of 1939.
Into the unknown
During the 1930s, Soviet trial-and-error efforts to develop new methods of rocket propulsion tested an experimental engine burning onboard propellant with the help of air sucked from the atmosphere. As a result, the vehicle would not need an onboard supply of oxidizer, however it would depend on another propulsive force for its initial acceleration. Known today as a ramjet, this propulsion system still remains on the cutting edge of aerospace technology, promising one day to revolutionize both aviation and space travel.
The original concept of the ramjet engine was proposed in France between 1907 and 1913. By 1928, in the USSR, Boris Stechkin, a leading aviation propulsion expert, had completed theoretical studies showing the promising performance of the ramjet engine at supersonic speed. Moreover, in 1931, A.G. Crocco showed that a ramjet vehicle could accelerate its payload to orbital velocity! (701) Obviously, there was no aircraft at the time capable of such a tremendous acceleration to test the concept. To resolve the problem, engineers at Moscow's Group of Studies of Jet Propulsion, GIRD, decided to fire the engine from a cannon! At GIRD, Yuri Pobenostsev led the development of a small ramjet vehicle fitted inside a 76-millimeter artillery shell, which could fly two times faster than the speed of sound, Mach 2. The engine was designed to burn white phosphorus fuel.
The first "flight" took place in September 1933. Two other series of firings were made in 1934 and 1935. Unfortunately, tests showed that the engine could hardly provide enough trust to overcome the air resistance to the projectile. When the ramjet was beginning firing at a speed of 630 meters per second, the vehicle had 42 kilograms of frontal resistance. Upon reaching a thrust of 23 kilograms, the vehicle still had to overcome around 19 kilograms of frontal resistance. After the third (most successful) test trials in 1935, the efficiency of the ramjet engine was estimated at just 16 percent. (701)
Despite all the challenges, work on the air-breathing rocket continued in 1934 in Moscow at the Stratospheric department of the Osoaviakhim, a government-sponsored society for the support of defense, aviation and chemical development. Igor Merkulov, who led the 3rd Brigade of the stratospheric department, took charge of the project. Still in his 20s, Merkulov was a ardent space travel enthusiast from his school days and already a GIRD veteran.
After several years of difficult theoretical studies, Merkulov's team felt confident enough to try a small experimental rocket with a new ramjet engine. The vehicle would blast off with the help of a solid-propellant charge in the tail, but once airborne and its solid fuel exhausted, an air-breathing ramjet would fire, also burning the powder propellant. Preliminary calculations showed that its thrust would be greater than the air resistance on the vehicle. (699) The team also believed that it would be able overcome all the challenges of stable flight and of a safe separation of a two-stage vehicle in flight. (700)
Despite a very positive response from Merkulov's colleagues and superiors, the project lingered for almost a year in the Directorate of Military Inventions. However Merkulov did not waste time, proposing a modified design. Now, it would be a truly two-stage rocket with a fully autonomous solid booster and a second-stage ramjet rocket. It became known as VR-3 or RV-3 (some sources identified it as R-3). The vehicle looked like a traditional rocket of the time but with its nose tip "cut off." In reality, the "cut" was an inlet for the air, which facilitated combustion.
A total of three batches of 16 test articles were reportedly built.
The historic launch
A series of preliminary tests apparently started in February 1939 at the Planernaya airfield, which at the time was still on the northwestern outskirts of Moscow. During a firing on March 5, engineers confirmed with certainty that their ramjet indeed helped to accelerate the rocket. (701)
On May 19, the official test flight attended by the members of the Narkomat (ministry) of the aviation industry was scheduled. (699) Preparations for launch, which included the integration of the ramjet vehicle with its first-stage booster took the entire day. It was already dark by the time Merkulov gave the command for ignition from behind a makeshift protective wall made of metal panels. The rocket's solid booster fired with a loud bang and the vehicle blasted into the air from its launch rails. After the rocket's fiery tail withered for a moment with the separation of the booster three seconds into flight at an altitude of 250 meters, a new bright flash of light marked the ignition of the ramjet.
A team of astronomers from Moscow Planetarium tracking the flight with their most advanced instruments from nearby hills reported that the vehicle had climbed to an altitude of 1,808 meters and had successfully accelerated to 224 meters per second with the help of a revolutionary ramjet motor and then fell 300 meters from the launch site. (700) However the rocket apparently fell short of its projected nine-kilometer flight ceiling.
The test paved the way to the development of a new version of the ramjet engine, which would serve as an auxiliary thruster (or DM in Russian abbreviation) for propeller-driven military aircraft. (699) In just six months, on Jan. 26, 1940, an I-15 fighter equipped with a pair of ramjet boosters took to the air. This larger ramjet engine used benzene instead of powder fuel.
Several experimental ramjet rockets were also apparently planned, however World War II was blamed for interrupting this work.
Next chapter: Hypersonic vehicles
The VR-3 rocket in numbers*:
*Original specifications. Some mass savings were achieved in later versions of the rocket (701)
Page auhtor: Anatoly Zak, Last update: May 19, 2014
Page editor: Alain Chabot, Last edit: May 19, 2014
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A scale model of Merkulov's experimental ramjet rocket. (The first-stage solid motor mounted between tail fins of the rocket is not shown). Copyright © 2001 Anatoly Zak
Preparations of the VR-3 rocket for launch.
A VR-3 rocket ready for launch.