RUSSIA’S TROUBLED START

The development of rocket planes in Russia before the war followed a very similar path as in Germany, with spaceflight enthusiasts developing rocket motors and later incorporating them into simple gliders. However, whereas in Germany rocket plane development was not deemed to be very urgent until the situation took a turn for the worse in 1943, in Russia it was the complete opposite. When German forces invaded the Soviet Union, Russia was ill prepared and its forces were initially easily overrun. The Luftwaffe pilots were able to accumulate individual scores of hundreds of Soviet planes shot down. Russia needed a ‘wonder weapon’ quickly. The development of an operational rocket propelled interceptor became an instant priority. As the situation improved, military support for rocket plane development actually lessened in Russia, while at the same time in Germany the need for such aircraft rapidly increased.

The history of rocket planes in Russia starts with a club of rocket enthusiasts led by rocket engine developer Fridrikh Tsander called GIRD, the Russian abbreviation for ‘Group for Research of Reactive Propulsion’. Working without financial support, the members jokingly explain that the name of their organization actually means ‘Group of Engineers Working without Money’. Inspired by the Russian theoretician Konstantin Tsiolkovsky and the German rocket pioneer Hermann Oberth, Tsander is a prominent advocate of spaceflight but he doesn’t agree that other planets should be reached by expendable rockets. In an article ‘Flights to Other Planets’ published in the journal Tekhnika I zhizn in 1924 he explains that parachutes are less than optimal for landing a rocket on a planet which has an atmosphere, or indeed for returning a spacecraft to Earth, as parachutes do not offer the possibility of landing in a precise location. He continues: “For descending to a planet having sufficient atmosphere, using a rocket, as proposed by K. E. Tsiolkovsky, will also be less advantageous than using a glider or an aeroplane with an engine, because a rocket consumes much fuel during the descent, and its descent will cost, even if there is only one person in the rocket, tens of thousands of rubles, whereas descending with an aeroplane costs only several tens of rubles, and with a glider, nothing at all.” In 1933 GIRD manages to launch the first Soviet liquid propellant rocket (called the GIRD 10) to an altitude of 400 meters (1,300 feet). The rocket and its engine were mostly designed by Tsander, but sadly he died shortly before the test.

Another prominent GIRD member was Sergei Korolev, who would go on to become famous as the chief designer of the early Soviet space rockets. During the Cold War Korolev was the Russian equivalent of Wernher von Braun, and was responsible for the launches of Sputnik in 1957 and cosmonaut Gagarin in 1961 that began the space race and caused President Kennedy to direct NASA to beat the Russians to a manned landing on the Moon.

Shortly after the creation of GIRD in 1931, Korolev approaches Tsander with an idea for a rocket plane. He proposes to base this RP-1 on the existing BICh 8 tailless flying-wing glider and to power it using Tsander’s OR-2 rocket motor, which used gasoline and liquid oxygen and delivered a thrust of about 500 Newton. Later it is decided that the BICh 11 glider is better suited. In May 1932, Korolev becomes the director of GIRD and continues the design of the RP-1 and a successor called the RP-2. His work on the RP-1 and RP-2 designs evolves into the more ambitious RP – 218, a two-seat rocket plane for high-altitude research equipped with a pressurized cabin. A fixed main landing gear is planned initially, but this is soon changed to a retractable undercarriage. The RP-218 was to be taken to altitude by a carrier

Concept for Korolev’s RP-218.

airplane and released to boost itself to an altitude of 80 km (50 miles) or higher; to the edge of space, in fact. The plane is never built, partly because no rocket motor with the requisite thrust and weight is available. Interestingly, the envisaged mission scenario was very similar to that of the US X-15 rocket plane of the 1960s.

In 1935 Korolev designs the much simpler wooden SK-9 two-seater glider, which he intends to serve as a test bed for rocket motors. The RNII Rocket Scientific Research Institution, a new professional organization created by the merging of GIRD and the Gas Dynamics Laboratory in Leningrad in September 1933, sets out to transform the glider into a rocket plane by equipping it with an OR-2 engine. Being optimized to fly at relatively low speeds, modified gliders are useful for testing low-thrust engines such as this but they are not normally aerodynamically and structurally designed for the loads that come with powerful engines and high velocities. Otherwise gliders are well suited for conversion to rocket planes because they are fairly cheap and easy to modify, they do not have engines in the nose that need to be removed, they can be towed into the air by another airplane prior to starting the rocket engine, and they are able to glide to a safe landing once the propellants have been consumed. But great care has to be taken to ensure that the balance of the original design is not disturbed too much; hence most of the added weight has to be located near the original center of gravity. An added complication is that the weight of the propellant will decrease as the engine runs, whilst the fixed weight of the added structures, tanks and engine will remain unchanged. If this is not properly taken into account, an aircraft that is nicely balanced at take-off can become unstable as the flight progresses.

The rear seat of the SK-9 is replaced by a tank for 10 kg (22 pounds) of kerosene and two tanks for 20 kg (44 pounds) of fuming nitric acid. The rocket motor and its nitrogen pressurization system are installed in the aft fuselage, with the nozzle exit under the slightly modified rudder. The resulting RP-318 rocket plane has a take-off weight of 660 kg (1,460 pounds), a wingspan of 17 meters (56 feet) and a length of 7.4 meters (24 feet). The test phase begins with ground firing tests, initially with the OR – 2 controlled from the cockpit but separated from the plane by an armor plate (in case it blows up) and later with the engine installed in the aircraft. More than 30 test firings are performed. In April 1938 the plane is deemed ready for flight but then the notorious ‘purges’ of the paranoid Soviet leader, Josef Stalin, take their toll. Already, in 1937, the director and the chief engineer of the RNII institute (now called

NII-3) were executed. But a war with Germany is looming and Stalin finally realizes that shooting Russian aircraft engineers is detrimental to the quality of his air defenses. By locking them up in development center prisons instead, it will be possible to keep an eye on them while they help to design planes for the war effort. Valentin Glushko, the chief engine designer, is sent to the Butyrka prison and works in a special design bureau for “subversive elements”. When in June 1938 Korolev himself is declared an “enemy of the people” and sentenced to ten years’ hard labor in the horrible Kolyma gold mines in which temperatures regularly drop to minus 38 degrees Celsius (minus 36 degrees Fahrenheit), the development of the RP-318 halts. Although Korolev is soon transferred to a prison design bureau on the request of famous aircraft pioneer Sergei Tupolev (himself in prison) he is not permitted to work on rocketry except at night in his own time.

Only near the end of 1938 is the RP-318 project resumed at NII-3, now under the leadership of Arvid V. Pallo and without the involvement of Korolev. It is decided to repair and modify the existing prototype into the RP-318-1, involving the rebuilding of the tail section that was damaged during the ground tests, the installation of a new landing ski, and the fitting of a shock absorber to the tail skid. The most important change is the replacement of the OR-2 engine by the more powerful ORM-65 rocket engine designed by Glushko and Leonid Pushkin. But concern soon arises about this choice. The ORM-65 has been ground tested many times and flown nine times on the winged experimental RP-212 cruise missile designed by Korolev, but it is not really suitable for a reusable piloted aircraft. The engine can only be ignited on the ground and, once operating, cannot be turned off. Also the heat of the combustion degrades the engine to such an extent that it will be dangerous to attempt to use it for several flights. The design is therefore modified to make it compatible with a manned rocket plane. The resulting RDA-1-150 engine is 2 kg (4 pounds) lighter, has an improved cooling system and redesigned propellant injectors, can be ignited in flight in a low thrust regime in which only about 10% of the normal amount of propellant flows into the combustion chamber, and its operating thrust can be regulated between 700 and 1,400 Newton. The new engine is ground tested over 100 times, including 16 times while installed in the actual aircraft.

The flight test program with Vladimir Pavlovich Fedorov as pilot begins in early February 1940 at a grassy airfield in Podlipki near Moscow. It starts with unpowered glide flights using a dummy engine for mass balance and with the plane being towed to altitude by an R-5 biplane. On the first flight the propellant tanks are empty, on the second they are half filled, and on the third the full tanks are slowly drained to mimic propellant consumption by the engine. In February 1940 three low-power flights are conducted during which the engine is run in the low-thrust ignition regime. Fedorov reports that the engine can be clearly heard in his open cockpit, which means that its proper functioning can be monitored by its sound as well as by the instrumentation in the cockpit.

Finally the aircraft is ready for a full powered flight. On 28 February 1940 the RP – 318-1 is towed to an altitude of 2.8 km (1.7 miles) and released. It glides 200 meters (660 feet) down before Fedorov ignites the rocket engine. Gray smoke shows that the powder charge has fired to ignite the engine’s liquid propellant, then brown smoke shows that the engine is operating in its starting regime. As Fedorov further opens the propellant flow, a bright, almost smokeless flame nearly 1.5 meters (5 feet) long streaks from the nozzle. It pushes the RP-318-1 from 80 to 140 km per hour (50 to 90 miles per hour) in 5 seconds. Next, the plane climbs up to an altitude of 2.9 km (1.8 miles). When the engine stops after 110 seconds of continuous operation, Fedorov glides the aircraft to a safe landing. The plane makes another two successful powered flights on 10 and 19 March, after which the arriving spring melts the snow and turns the airfield into an unusable mire. In the autumn the plane is returned to NII-3 and dissembled. There are plans for further tests using another engine and a jettisonable wheeled dolly but these never take place due to other priorities within the institute. In August 1941 the German Army approaches Moscow, and as the institute prepares for evacuation to the safety of the Ural mountains the RP-318-1 is burned to prevent the Germans from finding it.

Meanwhile, in 1940 NII-3 makes a study of a plane primarily powered by wing – mounted ramjet engines and an RD-1400 rocket engine in the tail to propel the plane up to the speed required for the ramjets to start working. In the spring of 1941 a draft concept called the Tikhonravov 302 is put together under the leadership of Mikhail Tikhonravov. This is later approved by the director of the institute, Andrei Kostikov, and Tikhonravov leads a team of engineers in developing the detailed design. He also assumes responsibility for the necessary aerodynamic calculations.

Kostikov had become director of the institute after the execution of his predecessor and the imprisonment of Korolev and Glushko; all of which he seemingly engineered to advance his own career. When war breaks out with Germany and Stalin takes an interest in the new project, Kostikov decides to claim the design in the expectation that its success will raise his standing with Stalin. In November 1942 Stalin names him chief designer, and Tikhonravov’s revolutionary airplane concept becomes the Kostikov 302.

The Soviet State Defense Committee gives Kostikov only one year to get the 302 into the air. He duly promises that it will be able to fly for 20 minutes at an altitude of 8 km (26,000 feet) at a speed of 800 km per hour (500 miles per hour). A budget is allocated for the construction of two prototypes by NII-3’s OKB-55 experimental production facility headed by Matus R. Bisnovat, and a series of flight tests. The 302 is mainly wood but the elevators are made of aluminum alloy. The straight, tapered, low-slung wings have a shght dihedral for enhanced roll stability. It has a pressurized cockpit, an undercarriage with retractable main wheels and a retractable tail wheel, and hydraulic actuators to help the pilot to handle the expected large forces on the control surfaces (normally fighter planes of that time were operated by muscle power alone, which could make steering a plane at high speed with high aerodynamic forces very ‘heavy’). Because of the war, the test phase is to be minimized and the airplane turned into an operational fighter as soon as possible. Hence the 302 prototypes are equipped with armored glass in the canopy, an armor plate under the instrument panel and four ShVAK 20-mm cannon; two in the nose and two in the forward belly of the plane. In addition, the aircraft would be able to carry rockets on rails under its wings, or two 125 kg (276 pound) bombs for ground targets. The ramjets were to have been installed under the wings but development difficulties lead to the decision

to cancel them altogether and operate the plane by rocket power alone, as the 302P (‘Perekhvatchik’, Russian for Interceptor).

The lack of ramjets greatly reduces the potential range of the aircraft but it is still valuable as a short-range interceptor for fast, short-duration attacks on enemy aircraft (essentially giving it the same role as the German Me 163). The new engine chosen for the plane is the RD-2M-3V developed by Dushkin and Glushko. Like the engine developed for the German Me 263 (and for the same reason) it has two combustion chambers: a large one with 11,000 Newton of thrust for take-off and ascent, and a smaller 4,000 Newton chamber for more economical cruise flight (these numbers are the thrust given at sea level; at higher altitudes the thrust is slightly greater because atmospheric pressure hinders the outflow of the exhaust). The propellant load for this engine consists of 505 kg (1,110 pounds) of kerosene and 1,230 kg (2,710 pounds) of 96% concentrated nitric acid; a nasty and dangerous substance. These propellants are not hypergolic, so an igniter is required to initiate combustion. The pumps providing the propellant to the combustion chambers operate using 80% concentrated hydrogen peroxide and provide gas at high pressure by the process of decomposition.

In the spring of 1943 the first of the two prototypes built by OKB-55 is sent for testing in the large T-104 wind tunnel of the TsAGI institute. Glide test flights begin in August 1943 with the 302P prototype being towed by a Tupolev SB bomber to its release altitude. V. N. Yelagin is the engineer responsible for these test flights, with pilots Sergey N. Anokhin, Mark L. Gallai and Boris N. Kudrin (the nation’s oldest

One of the Kostikov 302 prototypes.

active test pilot). The twelve tow flights reveal serious stability problems at speeds over 200 km per hour (120 miles per hour), which is of course a major hurdle for a plane that is one day expected to fly at transonic speeds. Modifications are made and another series of glide flights are conducted in which the 302P is towed by Tupolev SB, Tupolev Tu-2, and North American B-25 bombers (the latter one of the planes donated by the US to help the Russians in their fight against Germany). This time the 302P proves to be exceptionally stable and rather easy to fly and land while gliding, so expectations for its handling under rocket power are high. However, development of the rocket engine is lagging far behind. In early 1944 it is still not able to reach the performance required to make the 302P the effective interceptor that Kostikov promised.

With the ram engines deleted, the plane is now expected to be able to fly at 8 km (26,000 feet) altitude for only 5.3 minutes instead of the specified 20 minutes, and at 725 km per hour (450 miles per hour); some 75 km per hour (50 miles per hour) less than originally specified. If the 302P were to fly at the original altitude and speed, it would run out of propellant in just 2.5 minutes. The absolute top speed also dropped from 900 km per hour (560 miles per hour) to 800 km per hour (500 miles per hour). The machine is still expected to be able to shoot up to 9 km (30,000 feet) in only 2.8 minutes but the military value of the plane as an interceptor is now highly doubtful. Moreover, whereas at the start of the project the Soviet Union was being overrun and overflown by the Germans, by early 1944 the need for an advanced interceptor plane is less urgent. In March 1944 it is decided to cancel the entire program, although one powered flight of the first 302P prototype remains in the planning. In the winter of 1944 it is fitted with skids and makes its first and final flight powered by an RD-2M3 rocket engine. Details are scarce but eyewitnesses say the flight was a success, even though one of the undercarriage ski legs failed at touchdown and caused the plane to slew into a snowdrift. However, the failure of the 302P as an effective weapon has dire consequences for Kostikov. Despite having the ‘Hero of Socialist Labor’ medal and the Stalin Prize, he is sent to prison on 15 March 1944 for obstructing the war effort and is not released until 1945.

During 1942 Aleksandr Yakovlev, the famous designer of Russian fighter aircraft, worked on the design of a concept very similar to the 302. It was to be based on his Yak-7, but instead of a piston engine and propeller it was to be driven by two ramjets mounted under the wings and a Dushkin D-l-A liquid propellant rocket motor in the rear fuselage. The result would be the Yak-7R (the ‘R’ standing for ‘Reaktivnyy’, meaning ‘Reaction-propelled’). But the project never left the drawing board owing to the lack of reliable ramjets.

The most famous Soviet rocket plane of the Second World War is the Bereznyak – Isaev BI. This story begins in the spring of 1940, when the Zhukovsky Institute in Moscow (TsAGI) hosted a conference on ramjet and rocket propulsion. It is probable that the meeting was inspired, at least partially, by the advanced rocket and aircraft developments in Germany, which they knew of because Soviet intelligence had been able to recruit Willy Lehmann, a German Gestapo officer who kept them informed. Among the attendees were Viktor Fedorovich Bolkhovitinov, head of design bureau OKB-293, and Aleksandr Ya. Bereznyak and A. M. Isaev, two of his top engineers. Both Bereznyak and Isaev were very excited by the idea of rocket propelled aircraft and convinced Bolkhovitinov to let them start to design one. In the autumn of 1940 they showed fellow engineer Boris Chertok a preliminary design of what they called ‘Project G’. It was a concept for a compact plane built of wood and duralumin (an aluminum alloy) with a take-off weight of 1,500 kg (3,300 pounds). To serve as an operational interceptor it was to have four machine guns; two 12.7­mm and two 7.6-mm caliber. The engineers intended to power their plane with a new

14,0 Newton rocket engine burning low-grade kerosene and red fuming nitric acid that was under development at NII-3 by a team led by Leonid Dushkin (who had also designed the RDA-1-150 that powered the RP-318-1). Since the thrust of the engine was close to the maximum weight of the plane, which would decrease as it burned propellant, it would be able to climb almost vertically once airborne. The top speed was estimated at 850 to 900 km per hour (530 to 560 miles per hour). According to the designers the most important selling points were the incredibly fast climbing rate (enabling it to reach enemy planes quickly and intercept them by surprise), its high speed (making it virtually invulnerable to enemy fighters), and the inherent simplicity of the rocket in terms of manufacturing and maintenance when compared to high-performance piston engines.

Bereznyak, Isaev and Chertok visited NII-3 in March 1941 to check on the status of the rocket engine, called the D-l-A-1100. This was state-of-the-art at the time. It weighed 48 kg (106 pounds) and consisted of several large forged-steel sections (the conical head with 60 propellant injectors, the cylindrical combustion chamber and the nozzle) joined using bolts and copper gaskets. Cooling was provided by pumping the kerosene fuel through the double-walled combustion chamber and the nitric acid oxidizer through the double-walled nozzle. The engine was ignited using a glowing plug of nichrome; later replaced by silicon carbide. But this marvelous technology was not working yet, mostly due to problems with Dushkin’s innovative turbopump driven by hot gas and steam produced by a small combustion chamber that was fed a mixture of water and the same propellant as the main rocket combustion chamber; an efficient but complicated affair. Furthermore, the engine was not going to deliver the specified 14,000 Newton of thrust: the prediction was that it would deliver no more than 11,000 Newton. On 21 June Isaev proposed running the engine’s turbopump on compressed air instead; it would result in a heavier rocket engine but would be much simpler.

The very next day Germany invaded the Soviet Union and the need for the rocket propelled interceptor instantly became very urgent. Bereznyak and Isaev set to work on a new, more detailed design. They finished it in only three weeks and on 9 July, together with Bolkhovitinov, met with the head of NII-3, the earlier mentioned Andrei Kostikov. Although Dushkin was not happy with the idea of altering his fuel pump, Kostikov agreed that the urgency of the situation meant that using compressed air made sense. A letter was sent to the Kremlin, and it was even shown to Stalin personally. The Project G team went to Moscow to report on their design and were ordered to build the plane in only 35 days. The engineers were given leave to visit their families, then literally lived in the factory to meet the extremely demanding deadline. The same order tasked NII-3 to finish the development of the D-1-А-1100 engine as soon as possible, and make it capable of multiple restarts in flight as well as thrust variation in the range 4,000 to 11,000 Newton.

The new design was called the BI for ‘Blizhnii Istrebitel’ (Close-range Fighter) and also the first letters of the two inventors Bereznyak and Isaev, although whether this was deliberate is unclear. It was now a sleek low-wing machine with a length of only 6.4 meters (21 ft) and a wingspan of 6.5 meters (21 ft). The take-off weight was 1,650 kg (3,640 pounds), of which 710 kg (1,570 pounds) was propellant. This made the BI a very diminutive fighter aircraft; smaller and lighter than the Me 163B. For comparison the conventional German Messerschmitt Bf 109G fighter had a length of

9.0 meters (29 ft), a wingspan of 9.9 meters (33 ft) and a maximum take-off weight of 3,400 kg (7,500 pounds), and was still regarded as being a relatively small fighter. The BI was kept as simple as possible so that it could be produced in short order and in sufficient numbers to overcome the German invasion of Soviet airspace. The four machine guns planned earher were replaced by two more powerful 20-mm ShVAK cannon. The BI would have a wooden frame and a 2 mm (0.08 inch) plywood skin covered by a bonded fabric, and it would be easy to mass produce. The wings were to be relatively short to limit drag whilst still providing sufficient lift at the planned high flight speeds (lift is a function of both the area of the wings and the flight speed, so at higher speeds smaller wings are sufficient). However they were not particularly well designed for transonic flight phenomena (something that will result in a serious accident, as we shall see). The ailerons, elevators and rudder were covered by fabric but the flaps were duralumin. Ten tanks with compressed air (held at a pressure of 60 atmospheres), five in the forward section and five in the aft section, were required for the rocket engine’s turbopump, to retract and deploy the landing gear, and to power the cannon. The forward section also housed two kerosene fuel tanks while the aft section had three tanks of nitric acid oxidizer. The air tanks were made from a high – strength steel (Chromansil) that was great for making light pressure vessels but not very resistant to corrosion. Their proximity to the extremely corrosive nitric acid was thus rather hazardous and required the acid tanks to be replaced periodically in order to ensure that no leaks could develop.

Working around the clock (with local furniture makers supplying the wood-and – fabric airframe) the team delivers the first prototype on 1 September 1941. A second prototype is also being assembled. However, Dushkin’s engine is still not available. The first prototype, BI-1, is towed into the air by a Pe-2 bomber on 10 September with test pilot Boris Kudrin at the controls. Following release, he glides back to the airfield and makes a successful landing. Another fourteen unpowered flights follow and establish that the plane behaves well at low speeds. Interestingly, rival aircraft designer A. S. Yakovlev had the prototype towed to the TsAGI T-104 wind tunnel for testing. This alarmed the BI team because Bolkhovitinov had a rather rocky history with Yakovlev, but Yakovlev himself, and his aircraft designer, Ilya Florov, studied the results and gave the team good suggestions for improvements. In this way a yaw instability was corrected by enlarging of the rudder and adding two circular vertical plates at the tips of the horizontal stabilizer.

In addition to the problems with the engine, the BI project was delayed by the evacuation of both OKB-293 and NII-3 in October 1941 (in preparing for which, as mentioned above, the RP-318-1 rocket plane was burned). Most of Moscow’s vital war industries were moved deep into the Ural mountains to ensure they would not be overrun by the rapidly advancing Germans. The BI team was stationed in Bilimbay but Dushkin’s team ended up 60 km (37 miles) away in Sverdlovsk. Near their new accommodation the team built a test stand for their aircraft on the shore of the frozen Lake Bilimbay. It comprised a cradle that could hold the plane during engine tests, as well as measure the thrust. But there was still no engine to install. Dushkin was now increasingly absorbed by other projects (including NII-3’s own Kostikov 302 rocket plane) but he assigned his engineer Arvid Pallo to oversee the installation and testing of the rocket engine. When the static test campaign finally begins in early 1942 it becomes immediately clear that the nasty nitric acid is trouble: it corrodes parts of the airplane as well team members, causing skin burns and respiratory irritation. Tanks of sodium carbonate solution have to be kept handy to neutralize the all-too-frequent acid spills. For these tests the new test pilot Grigory Yakovlevich Bakhchivandzhi (Kudrin was ill) operates the engine from the cockpit: a method fraught with risk, as we have seen with the He 112 which almost killed Erich Warsitz during a ground test. Indeed, on 20 February the BI-l’s engine explodes, blasting the nozzle section into the lake. The forward assembly of the engine smashes through the airframe and strikes the rear of Bakhchivandzhi’s seat, knocking him against the instrument panel. Fortunately his injuries are minor. Nitric acid spraying from a broken propellant line drenches Pallo. Luckily his eyes are saved by his protective glasses and the rest of his face is partly spared by alert mechanics who dunk him head-first into a tank of soda solution. His scars serve as a grim reminder of the dangers of rocket testing. A study of the engine debris reveals that the combustion chamber had succumbed to corrosion fatigue. In pushing on with the testing phase despite a shortage of engines, the one D-l-A-1100 available had been operated too many times and for too long. After the test bench is rebuilt and the engine’s propellant supply system improved, static firing tests resume, with the undeterred Bakhchivandzhi performing three of them. A 5.5 mm (0.22 inch) steel plate is added to the rear of the pilot’s seat as protection.

By April 1942 the BI-1 is deemed ready for flight testing at the nearby Koltsovo airfield (now the main airport of the city of Sverdlovsk). Interestingly, in spite of the obvious danger, the nitric acid for the engine is actually transported to the airfield in glass bottles and there poured into the containers from which it will subsequently be fed into the plane’s tanks. All of this is done without any protective clothing.

On 2 May Bakhchivandzhi takes the controls of the BI for a short, low-thrust hop one meter above the ground. Then on 15 May he prepares for the first real test flight. Like the Me 163, the BI could explode if it were to make a hard landing before all the propellant was consumed, so it is loaded with only 240 kg (530 pounds) of nitric acid and 60 kg (130 pounds) of kerosene. He arrives wearing a new leather coat and shiny boots but when he climbs into the cockpit he is wearing his old flying gear: he explains that if he doesn’t survive the flight the new coat and boots will be useful for his wife… she could make some money by selhng them! Taking off under rocket power, he leaps into the air and quickly reaches an altitude of 840 meters (2,800 feet) and a speed of 360 km per hour (220 miles per hour) with the thrust limited to 8,000 Newton. Another safety measure, a fairly standard one for the early flights of new airplane prototypes, is that the undercarriage is kept down. After one minute, an indicator lamp reports the rocket is overheating, so he shuts the engine off. Gliding in to land, the plane descends too rapidly owing to insufficient forward speed and the resulting lack of lift. The touchdown is hard and breaks the undercarriage but the plane is not significantly damaged. Bakhchivandzhi lives to wear his new coat and boots another day.

Compared to today’s test flying, taking up a plane for the first time was in those days a truly scary business, especially if it was powered by a rocket engine. Modern airplane prototypes have already been exhaustively tested by sophisticated computer simulations long before metal is cut. The designs are based on an enormous database on subsonic, transonic and supersonic aerodynamics, control theory, materials and so on. Engines are tested hundreds of times before being deemed sufficiently reliable to be fitted into an airplane. All of this ensures that the question to be answered by the first flight is not whether it will fly, but rather how well it matches the performance predictions.

In contrast, pilots taking up revolutionary barely tested machines like the Me 163, Syusui and BI were really pushing very experimental technology into the unknown. Rather than wondering how the planes would fly, their minds were probably more occupied with the question how these new beasts were going to try to kill them. And unlike modem pilots, these pioneers did not have teams of engineers monitoring the flight on the ground, ready to help in case of trouble; once in the air, they were truly on their own. Last but not least, they had no ejection seat to instantly boost them out of a hairy situation.

The BI’s first flight lasted only 3 minutes and 9 seconds but was judged a success, with Bakhchivandzhi reporting, “the aircraft performed stable decelerations, gliding and handhng like any ordinary aircraft”. The State commission in charge of assessing the BI project delightedly noted: “The take-off and flight of the BI-1 aircraft with a rocket motor used for the first time as the aircraft’s main engine has proved the practical feasibility of flight based on a new principle; this opens up a new direction in the development of aviation.” This flight is sometimes hailed as that of the world’s first operational rocket fighter plane, but this is somewhat of a stretch. Even though the BI was designed as an operational weapon, it was still very much experimental. It is certainly true that it flew before the first Me 163B in Germany, but the DFS 194 and Me 163A predecessors of that machine had taken to the air long before the first BI flight.

Encouraged, Stalin authorizes the production of a batch of 30 BI interceptors for operational military service. These are enhanced with racks for small bombs that can be dropped onto enemy bomber formations by flying above them, causing damage by a combination of shock waves and shrapnel. The decision to declare the BI ready for military service after only a single low-speed flight soon proves to be premature.

In July, Pallo is recalled to NII-3 by Dushkin to help him with the institute’s own Kostikov 302 rocket plane. Isaev takes over management of the BI’s rocket engine in OKB-293. To help get started, he goes to learn the tricks of the trade from Valentin Glushko in the Butyrka prison design bureau. Glushko shows Isaev how to improve the engine, and Isaev starts to work on what will become the RD-1 rocket engine that will later be incorporated in the BI aircraft.

After its first and only flight, the BI-1 is deemed too damaged by nitric acid spills for safe flight and it is retired. Testing continues using the second prototype. On 10 January 1943 Bakhchivandzhi flies the BI-2 for the first time. He still limits the D-l – A-l 100’s thrust to 8,000 Newton and the speed to 400 km per hour (250 miles per hour) and hence achieves an altitude of only 1,100 meters (3,600 feet). This time the undercarriage, with skids instead of wheels for taking off from the snowy airfield, is retracted, resulting in a smoother flight with aerodynamics more representative of a BI interceptor in operational use.

The second BI prototype.

A third flight (the second with the BI-2) is made two days later by another pilot, Konstantin Gruzdev. (Bakhchivandzhi was at that time visiting NII-3 to check upon progress with the Kostikov 302; there was clearly a great deal of interaction between the rocket plane teams of NII-3 and OKB-293.) This time the propellant flow is fully opened, allowing the engine to provide its full thrust of 11,000 Newton. At the peak altitude of 2,190 meters (7,190 feet) Gruzdev achieves a speed of 675 km per hour (420 miles per hour). When he extends the undercarriage one of the skids breaks off but he manages to land safely. Asked about the flight, Gruzdev comments, “It’s fast, it’s scary, and it really pushes you in the back. You feel like a devil riding a broom.” Henceforth the ‘devil’s broomstick’ nickname is used by everyone who works on the BI project. Film of this flight has survived, showing the BI accelerating quickly over the frozen lake, taking off and shooting up. The less than perfect landing was also captured, with the plane toppling forward because of the broken skid and performing a ground loop as it skidded across the ice. If such a thing had happened on a grassy airfield the plane would probably have burrowed its nose in the ground, with a much more severe outcome.

On his return Bakhchivandzhi takes over from Gruzdev and flies the refurbished ski-equipped BI-1 prototype on 11 and 14 March 1943, and on the 21st he takes off in the third BI prototype (also on skids) and climbs at a maximum rate of 83 meters (272 feet) per second; this is about half the rate of an Me 163B but still at least five times better than contemporary Russian piston-engine propeller fighters. On the 27th Bakhchivandzhi makes another low-altitude test flight. After 78 seconds, as he opens the throttle to push the plane beyond its speed record, the BI-3 suddenly goes into a 50 degree dive and smashes into a frozen lake instantly killing the pilot. The BI team has discovered the infamous transonic ‘Mach tuck’ phenomenon the hard way. This is confirmed by tests in TsAGI’s new T-106 high-subsonic wind tunnel. The BI – 3’s onboard recording instruments were too badly mangled by the crash to give accurate data on the final speed, but estimates range from 800 up to an astonishing 990 km per hour (500 to 620 miles per hour). This disaster prompts the Air Force to cancel the pre-production order. For his achievements and ultimate sacrifice Bakhchivandzhi is posthumously awarded the ‘Order of Lenin’. (In 1973 he gained the more prestigious ‘Hero of the Soviet Union’.)

In May 1943, with OKB-293 relocated to Moscow following the German retreat, Bolkhovitinov writes a detailed report on the experiences with the BI prototypes. He emphasizes the need to study the shock effects that had caused the BI-3 to crash, and in order to investigate transonic and supersonic flight dynamics he recommends the development of a rocket plane capable of 2,000 km per hour (1,200 miles per hour).

No BI flights are made for over a year, probably in part because the urgent need for an operational rocket interceptor has lessened considerably, but also because time is required to build new airplanes. In 1944 five more prototypes are readied. BI – 6 is given a pair of ramjet engines instead of a rocket engine. It is towed into the air on three occasions but the test pilot never manages to get the engines to work properly. The other prototypes are to be fitted with the new RD-1 rocket engine designed by Isaev, the first example of which is completed and tested in October 1944 (it should not be confused with the smaller RD-1 engine of Dushkin and Glushko).

BI prototype number 5.

The general layout of the engine is similar to that of the D – 1-А-1100 and also has a maximum thrust of 11,000 Newton, but Isaev has introduced numerous improve­ments, including a more reliable electric-arc igniter instead of the glow plug, and new injectors designed to improve the fuel and oxidizer mix in the combustion chamber. The BI-7 is fitted with the Isaev RD-1 and flown by test pilot Boris Kudrin on 24 January and 9 March 1945. The maximum speed attained is 587 km per hour (365 miles per hour), which is well short of the dangerous transonic flight regime. These flights reveal a problem of excessive vibration in the tail. Gliding tests using the BI-5 and BI-6 are made to investigate the problem but the pilots are unable to recreate the vibration. However, by this point the war is nearly over and there is no operational requirement for the BI interceptor, so work is halted. The ‘devil’s broomstick’ is never flown in combat but its developers have gained valuable experience that will be put to good use after the war in developing new rocket propelled aircraft.

No examples of the BI survive but a reasonably accurate replica can be seen in the Russian Federation Air Force Museum in Monino. At the airport of Sverdlovsk, a monument of a BI replica shooting into the sky commemorates the rocket aircraft’s first flight from that location.

Another rocket plane that however never progressed as far as the BI was the ‘Malyutka’ (Little One), the final aircraft designed by famous aviation pioneer N. N. Polikarpov. The construction of a prototype started in early 1944 and was nearly complete by the middle of the year. However, all work was suddenly stopped when Polikarpov died of a heart attack on 30 July of that year, and his facilities were absorbed into the rival Lavochkin design bureau. Work on the project was never resumed.

The Malyutka was initially planned to use a D-l-A-1100, the same rocket engine as powered the BI, but it was later decided to use a dual-chamber RD-2M-3V, which was the same engine as intended for the Kostikov 302P. The combined thrust of the two chambers was expected to be sufficient for a top speed of 845 km per hour (525 miles per hour). As the propellants were consumed, the changing center of gravity of the aircraft would cause stability problems. The solution was to equip the plane with a tank from which water could be discharged in order to compensate for the changing weight balance; simple but not very elegant. The fuselage would be made of wood, but unlike any previous Polikarpov fighter the wings and tail section would be lightweight aluminum alloy. The aerodynamic control surfaces would be operated by a pneumatic system, the cockpit would be pressurized for high-altitude flight, and the armament would comprise two powerful VYa-23 23-mm cannon. In contrast to the conventional undercarriage of the 302P and the BI, the Malyutka would employ an undercarriage and a retractable nose-wheel instead of a tail wheel. A plane with a tail wheel (a so-called ‘tail-dragger’) has its nose angled up whilst taxing, which makes such an undercarriage a good choice for a machine driven by a propeller that has to clear the ground. However, a jet or rocket aircraft has no need for a large ground clearance of its nose and so can be equipped with a nose wheel in order to align the plane more horizontally on the runway. This gives the pilot a much better view of where he is going during taxiing and the take-off run. Furthermore, with the plane in a horizontal position there is less danger of jet or rocket engine exhaust melting the runway. While most propeller fighter aircraft of the two world wars had tail wheels, nearly all jet fighters employ so-called tricycle undercarriages, with wheels under the wings and the nose.

The idea of adding rocket engines onto existing piston-engined airplanes (like the Germans with the Heinkel 112) was also explored as a stop-gap while waiting for the rocket and jet airplanes. The 3,000 Newton thrust Dushkin and Glushko RD-1 engine was fitted to various types of aircraft to boost their performance. On 1 October 1943 tests began with the engine in the aft fuselage of a Petlyakov Pe-2 dive bomber, with the turbopump driven by one of the two standard piston propeller engines. The tests with the Pe-2RD prototype revealed problems with the RD-l’s electrical ignition, so it was replaced by a chemical ignition system. Both the RD-1 and the RD-lKhZ (the improved engine) were also flown on two Lavochkin La-7 fighters (the La-7R1 and La-7R2), an older La-7 prototype airframe (the La-120, converted into the La-120R), a Sukhoi Su-7 high-altitude interceptor (the original Su-7, not the jet fighter that was introduced in the 1950s with the same designation) and a Yakovlev Yak-3.

These tests proved the concept. For instance, on 11 May 1945 the rocket-equipped Yak-3, the Yak-3RD, reached a speed of 782 km per hour (486 miles per hour) at an altitude of 7.8 km (25,600 feet); some 130 km per hour (80 miles per hour) faster than the top speed of a conventional Yak-3. Indeed, it seems that a La-7R with an operating rocket motor successfully participated in the Moscow air displays of 1946 and 1947. However, on several flights the RD-1 exploded as kerosene fuel and nitric acid oxidizer came into contact outside the combustion chamber owing to leaks. The brave test pilots were usually able to land their damaged planes. One pilot of the sole rocket propelled Su-7 prototype was not so lucky, because while preparing the plane

The Sukhoi Su-7 with a tail-mounted rocket engine.

for the first post-war air display over Moscow in 1945 the rocket motor exploded, destroying the aircraft and kilhng him. On 16 August 1945 test pilot V. L. Rastorguev died when his experimental Yak-3RD crashed for unknown reasons.

It became clear that apart from reliable and safe rocket engines, Russia also lacked vital knowledge on the dynamics of transonic flight. By 1935 Aleksandr Moskalyov had already drafted a concept for a rocket propelled aircraft that he thought should be able to exceed the speed of sound. The planform for this plane was based on that of his SAM-9 ‘Strela’ (Arrow), a propeller aircraft that had a revolutionary ogival delta wing (also known as a Gothic delta because its shape resembles the arches in Gothic cathedrals). Moskalyov expected this type of wing to be well suited for transonic and supersonic flight, and this was later confirmed by the supersonic, ogival delta-winged British-French Concorde and Russian Tupolev 144 (‘Konkordski’) airliners. Piston engines and propellers were not going to show the full potential of his wing, but with a rocket engine he expected to be able to reach transonic speeds and beyond.

With Dushkin’s help for the propulsion part, in 1944 Moskalyov came up with the design for the SAM-29, also known as the RM-1 (for ‘Raketnyi Moskalyov’, Russian for Moskalyov Rocket). Like the Strela, it had an ogival delta wing and big vertical stabilizer, but no horizontal tail. The planned engine was Dushkin’s RD-2M – 3V. To comply with the military’s rather impractical demand that any new rocket plane must be armed to serve as an operational fighter, the experimental RM-1 would have two cannon in the nose. Unfortunately, at the end of the war the project

was deemed too futuristic and in January 1946 Moskalyov’s design bureau was closed. Had those in power understood the RM-l’s potential and continued their support, then either it or a close descendant might well have become the first aircraft ever to fly faster than the speed of sound.

More or less in parallel with the RM-1, the development of another dedicated research rocket aircraft concept started in 1943. Designer Ilya Florentyevich Florov led the project for the Russian Air Force, and his Florov 4302/4303 was a relatively small rocket plane made entirely of light alloy. Its exterior had a very smooth finish to minimize aerodynamic drag, but unlike the Me 163 and various other high-speed German designs it had straight wings rather than swept back wings or delta wings. It is unlikely that the benefits of swept wings for transonic flight were fully understood in Russia at that time. (Nor indeed, as we shall see in the description of the post-war X-l, was the concept of the swept wing understood in the United States). The fully horizontal wings of Florov’s design, which were set high on the fuselage, had down­ward angled ‘flippers’ at the tips. These effectively produced a negative dihedral in order to avoid ‘Dutch roll’, a stability problem common to high-winged aircraft that imparts an out-of-phase combination of ‘tail-wagging’ and rocking from side to side. (The German He 162 jet plane that flew near the end of the war also had a high wing and similar drooping wingtips, which the Germans called ‘Lippisch Ears’.) The pilot was housed in a small pressurized cockpit. Three aircraft were built. The first had a fixed undercarriage with a tail wheel (using parts from a Lavochkin La-5FN fighter plane) and was intended for low-speed gliding flights only. The other two aircraft were for powered flight and (like the German Me 163B) were to take off employing an ejectable tricycle dolly, then land on a skid and a tail wheel. Aircraft 2 would be a

Florov 4302 (top) and 4303 (bottom).

Florov 4302 with a nitric acid/kerosene RD-1 rocket engine designed by Isaev with a maximum thrust of 11,000 Newton at sea level. Plane number 3 would be finished as a Florov 4303 with the RD-2M-3V two-chamber engine (the same engine that was planned for the Kostikov 302P and the Polikarpov Malyutka) delivering a combined maximum thrust of 15,000 Newton at sea level.

However, the flight test phase only begins in 1946, well after the end of the war. Pilots A. F. Pakhomov and I. F. Yakubov are appointed and that year make 46 towed glide flights with aircraft number 1. After some taxi tests and a short hop, Number 2 is flown for the first time under rocket power in August 1947, with Pakhomov at the controls. He is towed to an altitude of 5.0 km (16,400 feet) by a Tu-2 bomber. After release, he ignites the rocket engine and quickly accelerates to a speed of 826 km per hour (513 miles per hour), which is rather daring in a new experimental airplane that has not previously been tested under power at lower thrusts and speeds. Afterwards Pakhomov reports that the plane behaved well in all respects, and there were no vibrations. Several more flights with the 4302 then follow, and on one occasion a propellant feed line ruptures and noxious acid vapors slightly intoxicate the pilot. But by late summer 1947 the concept of the Florov 4302/4303 was obsolete thanks to the new information on high-speed flight and aerodynamics obtained from the defeated Germans. Moreover, jet fighters were now reaching similar speeds as those for which the 4302/4303 were designed. It was therefore decided that sufficient data had been gathered from the testing and that it would be better to concentrate effort and funding on the more advanced MiG 1-270 rocket plane (described in the next chapter). When the 4302/4303 program was halted, aircraft number 3 was still awaiting its engine.