Soviet rocketry

RD-107 rocket engine

Soviet rocketry spanned the entire history of the Union of Soviet Socialist Republics (USSR) (1922-1991). Its scientists and engineers contributed to the development of rocket and jet engine propulsion systems, which were first used for artillery and later for fighter aircraft, bombers, ballistic missiles, and space exploration. Progress was greatly augmented by the reverse engineering of German technology captured by westward-moving troops during the final days of World War II and the immediate period following.

Liquid Fuel: The early contribution

Konstantin Tsiolkovsky

Traditionally, the Russian military had used only solid fuel (generally black powder).[1] Russian involvement in rocketry began in 1903 when Konstantin Tsiolkovsky published a paper on liquid-propelled rockets (LPREs).[2] Though the idea of rockets was as old as the 1600s, what made Tsiolkovsky's idea so radical was the fuel type. This work began to inspire young minds in Russian science. The use of liquid fuels challenged traditional thought and sparked a revolution in science that was overshadowed by the Bolshevik Revolution, which embraced new ideas in rocket technology.[3]

Members of GIRD. Left to right: standing I.P. Fortikov, Yu A Pobedonostsev, Zabotin; sitting: A. Levitsky, Nadezhda Sumarokova, Sergei Korolev, B.I. Charanovsky, Friedrich Zander.

One of the early leaders in Russian rocket engine development was Friedrich Zander, a German-born spaceflight enthusiast. Zander was the head of a group of rocket researchers called GIRD, the Russian acronym for "Group for Research of Reactive Propulsion," which was created in 1931. Zander, who idolized the Russian scientist Konstantin Tsiolkovsky and the German rocket scientist Hermann Oberth, oversaw the development of Russia's first liquid fueled rocket, the GIRD 10, which was launched successfully in 1933 and reached an altitude of 1300 feet. Zander died before the test took place.[4]

Two research groups played exceptionally important roles in the early development of Soviet Cold War era jet propulsion: The Leningrad Gas Dynamics Laboratory (GDL), and the Group for Research of Reactive Propulsion (GIRD). The GDL was formed in 1928, initially focusing primarily on the development of solid-fuel rockets for military use, such as anti-aircraft and anti-tank weapons, though it branched out into liquid-fueled rocket engines in May 1929. These rockets were developed to be used as engines for aircraft instead of conventional artillery. It was primarily through the work of the GDL that the OR and ORM series of rocket engines were developed, which would become the backbone of early Russian jet development.[5] The GIRD began as the Jet Engine Section of a larger civil defense organization known as the Society for the Promotion of Defense and Aerochemical Development; GIRD's role was to deliver practical jet engine technology to be employed in aerial military applications. MosGIRD worked on the development of space research, liquid-propellant rockets, rocket design as it pertained to aircraft, and the construction of a supersonic wind tunnel (used for the aerodynamic testing of the aircraft that they developed), whereas LenGIRD developed solid-fuel rockets used for photographing the upper atmosphere, carrying flares, and atmospheric sounding.[6]

Because of their similar objectives and parallel existence, there was some overlap between GDL and GIRD, and the two organizations were eventually merged. Generally speaking, however, while the GDL focused primarily on the development of rocket-propelled engines, the GIRD was involved with the engineering design, construction, and testing of the craft that would be powered using the engines that the GDL developed.[7] Although branches of GIRD were established in major cities all throughout the Soviet Union, the two most active branches were those in Moscow (MosGIRD, formed in January 1931) and in Leningrad (LenGIRD, formed in November 1931).[8]

Early pioneers in the field began to postulate that liquid fuels were more powerful than solid fuels.[9] Some of the early fuels used by these scientists were oxygen, alcohol, methane, hydrogen, or a combination of those.[10] There were two schools of thought; the GIRD which supported liquid propulsion, and the GDL, which supported solid fuel. A bitter rivalry developed between the researchers of these institutes.[11]

In order to obtain maximum military benefit, the Red Army's chief-of-staff Marshal Mikhail Tukhacheskii merged the GIRD with the GDL to study both fuel types. This institute was given the designation RNII.[12] Before the merge, the GDL had conducted liquid fuel tests and used nitric acid, while the GIRD had been using liquid oxygen.[13] A brilliant though often confrontational Sergei Korolev headed the GIRD when it merged into RNII and was originally RNII's deputy director. Korolev's boss was a hard-nosed man from the GDL by the name of Kleimenov. Bitter in-fighting slowed the pace and quality of the research at RNII. Despite the unproductive infighting, Korelev began to produce designs of missiles with liquid fueled engines. By 1932, RNII was using liquid oxygen with kerosene as a coolant as well as nitric acid and a hydrocarbon.[14] By 1933, the Soviets had successfully developed a rocket engine, the GIRD 09. The engine was tested on a glider, which reached a propelled altitude of 1300 feet before its thrust chamber failed.[15]

Applications in early aircraft

Sergei Korolev (1907–1966) as a young adult had always been fascinated by aviation. In his college years, his fascination grew towards rocketry and space travel. He continued on to become one of the most important rocket engineers of Soviet aircraft technology and became known as the "Chief Designer" of the Soviet space program.[16] In the early stages of Soviet rocketry science, Korolev was the one who initiated the program in Moscow called the Group for the Study of Reactive Motion, abbreviated as GIRD in Russian. As a renowned aeronautical engineer and the director of GIRD, he and his colleagues were enthusiasts of Russia's race to space and their focus was aimed at using liquid propellant to push their rockets into the atmosphere.[17] GIRD was later combined with the organization known as the Gas Dynamics Laboratory, abbreviated as GDL, in 1933 which was renamed the Rocket Scientific Research Institution or RN II. The GDL was interested in the use of solid propellant fuel for their rockets while GIRD's research involved the use of liquid fueled rockets. When the two institutes combined, they brought together two of the most exceptional and successful engineers in the history of Soviet rocketry. Sergei Korolev teamed up with propulsion engineer Valentin Glushko and together they excelled in the rocket industry, pushing the Soviet Union ahead of the United States in the space race. But remarkably through all of his achievements, Korolev's identity actually remained a Soviet secret up until his death in 1966.[18]

Sergei Korolev was a vitally important member of GIRD, and later became the head of the Soviet space program. Eventually, Korolev would play a crucial role in both the launch of Sputnik in 1957 and the mission which put Yuri Gagarin in space in 1961. In 1931, Korolev had come to Zander with a conceptual design for a rocket powered plane called the RP-1.[19] This craft was essentially a glider, to be powered with one of the GDL's rocket motors, the OR-2. The OR-2 was a rocket engine powered with gasoline and liquid oxygen, and produced a thrust of 500 Newtons. In May 1932, about a year before Zander died, Korolev became the director of GIRD. At this point, he continued developing his design for the RP-1, an updated version called the RP-2, and another craft that he called the RP-218. The plan for the RP-218 called for a two-seat rocket powered plane, complete with a pressurized cabin, a retractable undercarriage, and equipment for high altitude research. The design was never realized, though, because at the time, there was not a rocket powerful enough and light enough to make the RP-218 practical.[19]

In September 1933, GIRD was combined with the Gas Dynamics Laboratory, and the conglomerate was named the RN II Rocket Scientific Research Institution. Instead of pursuing the RP-218, in 1935, Korolev and RN II began developing the SK-9, a simple wooden two-seat glider which was to be used for testing rocket engines.[20] The rear seat was replaced with tanks holding kerosene and nitric acid, and the OR-2 rocket motor was installed in the fuselage. The resulting craft was referred to as the RP-318. The RP-318 was tested numerous times with the engine installed, and was deemed ready for test flights in April 1938, but the plane's development halted when Joseph Stalin performed a purge of RN II, executing the director and chief engineer, and imprisoning Korolev to the Kolyma gold mines for 10 years.[21]

World War II

The Soviets began to redesign the thrust chambers of their rocket engines, as well as investigate better ignition systems. These research endeavors were receiving more attention and funding as Europe began its escalation into the chaos of World War II. The Soviet rocket program had developed rocket engines with two stage ignition and variable thrust nearly two years before Germany rolled out their Me-163.[22] However, the Soviet engine was only on gliders for testing and was not available for full-powered flight. Also, the engine had too low of a thrust output, and pressure build ups were causing system failure. 1942 was an important year for Soviet research teams. The Soviets had finally produced a combat ready and tested engine, the D-7-A-1100. This engine utilized a nitric acid liquid fuel with a kerosene coolant. However, the Nazi invasion had the Soviet high command centered on other matters, and the engine was never produced for use.[23]

Towards the end of 1938, work had resumed on the RP-318 at N II-3, which was the new title for the Rocket Scientific Research Institution. The aircraft was repaired and modified, the most important modification being the addition of a new, more powerful engine to replace the OR-2. The new engine (the ORM-65) had been originally designed for a use in a single-launch cruise missile, but was adapted so that it could be employed in a multi-use aircraft.[24] For comparison to the OR-2, the new ORM-65 could produce a variable thrust between 700 and 1400 Newtons. After extensive testing, on February 28, 1940, the new RP-318-1 was successfully tested in a full-powered flight; the craft attained a speed of 90 mph, an altitude of 1.8 miles, 110 seconds of operation, and was landed safely when the fuel was expended. Although this was a hugely momentous occasion in Russian jet development, further plans to enhance this aircraft were shelved, and when the German Army neared Moscow in August 1941, the RP-318-1 was burned to keep it away from the Germans.[25]

It was the German invasion of Russia in the summer of 1941, however, that led to an acute sense of urgency for the Soviets to develop practical rocket-propelled aircraft. The Russian conventional air force was dominated by the Luftwaffe, with scores of their planes being shot down by individual German fighters.[26] Therefore, the Russians needed a superior weapon to counter the German air forces, and they looked to rocket-powered interceptor craft as the solution to their dilemma. Therefore, in spring of 1941, Andrei Kostikov (the new director of N II-3, previously RN II) and Mikhail Tikhonravov began the design of a new rocket-powered interceptor, which became known as the Kostikov 302.

The Kostikov 302 became the first Russian jet that would have many features that resemble modern fighter aircraft. It was designed mainly out of wood with some aluminum, but it included a pressurized cockpit and retractable landing gears. Another key aspect of the Kostikov 302 was that it was equipped with hydraulic actuators which allowed the pilot to steer the aircraft with more ease. Without these actuators, which in effect are the equivalent of power steering in one's car, the pilots of early jets had to steer them manually. Additionally, because of the ongoing war with Germany, Russian officials strove to make the Kostikov aircraft a functional military asset as quickly as possible. This entailed outfitting it with armored glass, armored plates, several 20 mm cannons, and the option of a payload of either rockets or bombs under the wings. Although it had limited range, this aircraft became a serviceable tool for the purpose of brief forays, like intercepting enemy aircraft. However, by 1944, the 302 was unable to reach the performance requirements Kostikov desired, in part because the rocket engine technology was not keeping pace with the aircraft development.[27]

German impact

V-2 rocket in flight

By 1944, Nazi Germany was crumbling underneath a two front war. Both American and Soviet forces were in a race for precious German Rocket facilities. The Soviet army occupied the bombed out rocket facility of Peenemünde on May 2, 1944. Realizing the magnitude of their capture, the Soviets began immediate salvage and repair to the facility. They also began an equivalent operation to Operation Paperclip in order to catch German scientists; the name of this operation was never disclosed. Although the Soviets missed Wernher von Braun's research group, they did capture Helmut Gröttrup and 200 rocket specialists.[28] Also, as part of the Peenemünde occupation, the Soviets obtained the V-2 rocket platform, the A-9/A-10 ocean range rockets, the Rheinbote surface-surface missile, and the R-4/M air to air missile. These represent a few of the notable platforms mostly intact and operational when captured. Gröttrup's team swelled to 5500 personnel and put Peenemünde back into full production. However, not satisfied with the results, Stalin ordered that the facility and its personnel be moved back to the USSR, where the scientists were distributed to various facilities.[29]

Another major factor in the development of modern Russian aircraft was the technology that was obtained from the German scientists and facilities after the end of World War II. In his article, "Russians in Germany: Founding the Post-War Missile Programme," Asif Siddiqi says that after the end of the war, the USSR exacted heavy fines from the defeated Axis Powers as reparations for damages done to their country. Since most of the Axis Powers were in no condition to repay the billions of dollars that they supposedly owed, the Soviets deployed "trophy brigades" whose task it was to confiscate all equipment, materials, and technology that would be of scientific use to the USSR.[30] Siddiqi points out that the Soviets obtained models of multiple jet fighters, jet engines, and a wealth of technical information concerning much equipment related to aviation. By the summer of 1945, the Soviet Union had control of 600 German aviation plants, which constituted more than 50% of all of Germany's aerospace industry. In fact, the Soviet Commissariat of Aviation Industry (NKAP) sent Russian aviation engineers to Germany in order to study in-depth details of German aircraft design: topics like wing design, rocket propulsion, and electronic systems were of particular interest.[31] Therefore, German expertise about reactive propulsion played a considerable role in the progression of Soviet development of both jet aircraft and rocket-powered spacecraft. Major General Nikolai Petrov, who headed a commission sent by the NKAP to examine German research facilities, informed the trophy brigades in Soviet occupied Germany that their task involved:

"... the removal, safekeeping and shipment to Moscow of all German experimental aircraft and engines of all types; aviation equipment, components and all materials associated with their design and production; scientific research materials; laboratory installations; wind tunnels; instrumentation; libraries; and scientific archives. The Commission must work on the scene immediately after Soviet troops capture appropriate locations, scientific centers and industrial regions of Germany."[32]

By 1953, the Soviet Union had developed their own version of the V-2. This system was called the R-11 missile. The R-11 was operational by 1955, had a range of 270 kilometers, and had an engine with a thrust of 8300 kgf. This system, inspired by the German V-2, became the basis for Submarine Launched Ballistic Missiles (SLBM). However, this application required a change of fuel from the land based fuel of Nitric acid with kerosene to the actual V-2 fuel using a graphite gas jet.[33]

Advances in military systems

Over the course of the Cold War, the Soviet Union developed an estimated 500 LPRE platforms in rocketry. The Soviets in 1982 began testing of the RD-170. This nitric acid and kerosene propelled rocket was capable of producing more thrust than any engine available. The RD-170 had 4 variable thrusters with staged combustion. The engine experienced early technical difficulties. The engine experienced massive damage as it was shut down in stages. To remediate this, Soviet engineers had to reduce its thrust capacity. The engine was officially flight tested successfully in 1985.[34]

The need for mobile nuclear forces began to increase as the Cold War escalated in the early 1950s. The idea of naval launched tactical nuclear weaponry began to take hold. By 1950, the USSR had developed submarine launched ballistic missiles. These missiles were multi stage, but due to fuel constraints, they could not be launched from underwater. The initial missile system used land based armaments. The USSR is the only known nation to utilize LPRE fueled engines for its SLBMs.

Katyusha Rocket Launcher in Action.

Aside from the nuclear aspect of rocket propelled missiles, USSR scientist sought to harness this technology for other weapon systems. As early as 1938, the Soviets were capable of using rockets for anti-personnel. This technology had been honed into the Katyusha Rocket used extensively against the Nazis during the German invasion.[35] During World War II, there is no record of any liquid fueled weapons being either produced or designed.[36] From 1958 to 1962, the Soviets researched and developed LPRE propelled anti-aircraft missile systems. These rockets primarily used nitric acid ratioed with a hypergolic amine for fuel.[37]

Andrei Tupolev

Tupolev TU-16 Bomber, the First Soviet Jet Bomber.

Andrei Tupolev was a leading aircraft designer of Soviet Russia. Tupolev was part of a company that specialized in all metal military aircraft. Tupolev recruited and formed TsAGI which was the Soviet aviation research institute. From 1920s to the early 1930s, Tupolev and his group worked on design and production of Soviet aircraft until 1937. In 1937, Tupolev was arrested by Stalin during the Great Purge. While in prison at Bulshevo Prison in Moscow, Tupolev was recruited by the NKVD to run TsKB-29. This organization utilized political prisoners to produce aircraft for the Soviet state. While in prison, Tupolev began to focus on bomber design and produced the Tu-2 which became the premier Soviet bomber during World War II.[38]

After World War II, Tupolev was assigned to working on reverse engineering scavenged US B-29 bombers. From his work, he produced the Tu-4. As the Cold war began to take shape, the emphasis began to turn toward speed of aircraft. By 1950, Tupolev's group produced the USSR's first turboprop, the Tu-95. Production and design progressed rapidly and by 1952 Tupolev had produced the first Soviet jet bomber, the Tu-16. The Tu-22 quickly followed as a twin engine jet bomber. The Tupolev group merged more into civilian jet aircraft until his death in 1972.[38]

Pavel Sukhoi

Pavel Sukhoi was a senior designer at the Central Aerohydrodynamics Institute in Moscow. This design group was under the control of Tupolev's TsAGI. In 1939, Moscow ordered Sukhoi to head a new scientific research group called OKB. This organization was based in modern-day Kharkiv, Ukraine. This new organization under Sukhoi's direction began research and design of round attack aircraft. The first of these was these was the Su-6. The onslaught of the Nazi invasion disrupted fighter development for the OKB. Following the end of World War II, Stalin directed Sukhoi to begin investigations into jet aircraft.[39] Early development issues combined with political prejudice doomed the first Soviet jet fighter, the Su-9, to never being put into production. Stalin thought the group's designs were too close to captured German jet aircraft. As a result, the design bureau was closed and moved back to Tupolev's department in Moscow.[39]

Sukhoi's luck changed again in 1953 when Stalin died. The new government permitted him to create another independent jet fighter design group. By 1954, the group was named OKB-51 which remains to this day an active research group. The early 1950s and 1960s yielded tremendous results in the form of the Su-7 and delta wing Su-9. These two fighters were individually updated with new technology to later become the Su-11 and Su-15 fighter interceptors. Upon his death in 1975, Pavel Sukhoi's name was added to the bureau name in recognition of his services.[39]

Development of MiG aircraft

MiG-17 fighter jet

One of the premier fighter jet aircraft that was employed by Russia throughout the duration of the Cold War was the MiG. In a Britannica Academic article, Siddiqi explains that in 1939, Joseph Stalin called for the creation of a new jet aircraft for use in the Russian military. The men chosen to lead the design of this new fighter were Artem I. Mikoyan and Mikhail I. Gurevich; the abbreviation MiG is a conjunction of the last names of these men. The first aircraft that they designed was originally called the I-200. The I-200 was a single engine jet designed to operate at high altitudes and at speeds high enough to intercept enemy bombers. This aircraft was first flown in 1940 (only 1 year after Stalin's declaration) and was later renamed the MiG-1. Eventually, the improved MiG-3 was developed, and by 1942, Mikoyan and Gurevich's team was made an independent design bureau, known informally as MiG but formally as OKB-155 (which stands for Experimental Design Bureau in Russian).[40]

Throughout the Cold War, OKB-155 churned out some of Russia's most important jet aircraft. According to Siddiqi, technical information captured from defeated Germany played a substantial role in OKB-155 rolling out the USSR's first jet fighter, the MiG-9, in 1946. Other prominent jets designed and produced by this group include the MiG-15, the MiG-17, the MiG-19, the MiG-21, the MiG-23, and the MiG-25. The MiG-15 through the MiG-21 were produced in the mid-1940s into the latter part of the 1950s. The MiG-23 and MiG-25 were not developed until the 1960s. Each of these aircraft offered unique capabilities to the Soviet military. The MiG-15 was employed primarily against American forces during the Korean War, and proved to be highly successful. The MiG-17, 19, and 21 continued to improve upon this design, as each model reached progressively speeds; The MiG-19 was Russia's first supersonic jet to be produced in industrial quantities, and the MiG-21 attained speeds in excess of two times the speed of sound. Finally, the MiG-23 was the Soviet Union's first variable-sweep wing fighter aircraft, and the MiG-25 was Russia's first jet capable of reaching Mach 3.[40]

Space age advances

Sputnik I, the first artificial Earth satellite

Sputnik 1 was the first artificial Earth satellite ever launched. On Oct. 4, 1957, the USSR launched Sputnik 1 into orbit and opened communications with it.[41] Sputnik 1 was designed to be the forerunner for multiple satellite missions. The technology constantly underwent upgrades as the weight of the satellite increased. The first notable failure occurred during Sputnik 4. The engine designed for exiting orbit malfunctioned and fired the vehicle into deep orbit where it burned. This failure spurred development for more reliable engines.[42] The success of Sputnik 1 was followed by the launch of 175 meteorological rockets in the next two years. In all, there were ten of the Sputnik satellites launched.

The ability to launch Sputnik 1 came from the nuclear arsenal of the Soviet Union. The Vostok engine (RD-107) for ICBMs was utilized for the launch vehicle for Sputnik. The first Vostok version had 1 core engine and 4 strap-on stage engines. The engines were all vectored thrust capable. The original Vostok was fueled by liquid oxygen and kerosene. There were a total of 20 engines each capable of contributing 55,000 pounds of thrust.[43] The Vostok engine was the first true Soviet design. The technical name was the RD-107 and later the RD-108. These engines had two thrust chambers. They were originally mono-propellants that used hydrogen peroxide. This family of engines were utilized not just on the Vostok, but also on the Voskhod, Molniya, and Soyuz launch vehicles.[44]

By 1959, the space program needed a 3-stage engine platform, so the Vostok engine was adapted accordingly for launching Moon probes. By 1963, the Vostok was equipped for 4-stage applications. This platform was used for the first multi-manned flight.[45] As 1964 began, the Soviets introduced a new engine into its booster engine repertoire, the RD-0110. This engine replaced the RD-107 in the second stage boost in both the Molniya and Soyuz launch vehicles. These engines were liquid oxygen propelled with kerosene coolant. The RD-0110 had four variable thrusters. What was unique about this engine is that it initially was started by a solid fuel propellant, but was fueled, once in flight, by liquid oxygen.[46]

This development caused a new problem for the Soviet scientific community, however. The Vostok was too powerful for newer satellites trying to reach low Earth orbit. The space community turned once again to the Soviet missile command. The new Intermediate Ballistic Missiles (IBRM) systems provided two engine options: the Sandal (1 stage) or the Skean (2 stage). Both systems were upgraded to a new RD-111 engine. Following these upgrades, the largest satellite called Proton I was launched in 1965.[47] The type of engine used for Proton I was the RD-119. This engine provided nearly 3,000,000 lbs. of thrust, and was ultimately used to execute low Earth orbit.[47]

Notes

  1. Siddiqi, Asif (July 2003). "The Rockets' Red Glare". Technology and Culture. 44 (3): 473.
  2. Siddiqi, Asif (July 2003). "The Rockets' Red Glare: Technology, Conflict, and Terror in the Soviet Union". Technology and Culture. 44 (3): 474.
  3. Siddiqi, Asif (July 2003). "The Rockets' Red Glare". Technology and Culture. 44 (3): 474.
  4. Van Pelt, Michel (2012). Rocketing into the Future: The History and Technology of Rocket Planes. New York: Springer Business and Science Media. p. 120.
  5. Stoiko, Michael (1970). Soviet Rocketry: Past, Present, and Future. New York, Chicago, and San Francisco: Holt, Rinehart, and Winston. pp. 43–44.
  6. Stoiko, Michael. Soviet Rocketry. pp. 51–53.
  7. Stoiko, Michael. Soviet Rocketry. p. 46.
  8. Stoiko, Michael. Soviet Rocketry. p. 51.
  9. Sutton, George (Nov–Dec 2003). "History of Liquid-Propellant Rocket Engines in Russia, Formerly the Soviet Union". Journal of Propulsion and Power. 19 (6): 2.
  10. Sutton, George (Nov–Dec 2003). "History of Liquid-Propellant Rocket Engines". Journal of Propulsion and Power: 2–3.
  11. Siddiqi, Asif (July 2003). "The Rockets' Red Glare". Technology and Culture. 44 (3): 476.
  12. Siddiqi, Asif (July 2003). "The Rockets' Red Glare". Technology and Culture. 44 (3): 478.
  13. Siddiqi, Asif (July 2003). "The Rockets' Red Glare". Technology and Culture. 44 (3): 481.
  14. Sutton, George (Nov–Dec 2003). "History of Liquid-Propellant Rocket Engines". Journal of Propulsion and Power. 19 (6): 3.
  15. Sutton, George (Nov–Dec 2003). "History of Liquid Propellant Rocket Engines". Journal of Propulsion and Power. 19 (6): 4.
  16. West, John (2001). "Historical Aspects of the Early Soviet Russian Manned Space Program". Journal of Applied Physiology: 1501–1511.
  17. Siddiqi, Asif (July 2003). "The Rockets' Red Glare". Technology and Culture. 44 (3): 470–501. doi:10.1353/tech.2003.0133.
  18. West, John (2001). "Historical Aspects of the Early Soviet/Russian Manned Space Program". Journal of Applied Physiology: 1501–1511.
  19. 1 2 Van Pelt, Michel. Rocketing into the Future: The History and Technology of Rocket Planes. p. 120.
  20. Van Pelt, Michel. Rocketing into the Future: The History and Technology of Rocket Planes. p. 121.
  21. Van Pelt, Michel. Rocketing into the Future: The History and Technology of Rocket Planes. pp. 121–122.
  22. Sutton, George (July 2003). "History of Liquid-Propellant Rocket Engines". Journal of Power and Propulsion. 19 (6): 15.
  23. Sutton, George (July 2003). "History of Liquid-Propellant Rocket Engines". Journal of Power and Propulsion. 19 (6): 6.
  24. Van Pelt, Michel. Rocketing into the Future: The History and Technology of Rocket Planes. p. 122.
  25. Van Pelt, Michel. Rocketing into the Future: The History and Technology of Rocket Planes. p. 123.
  26. Van Pelt, Michel. Rocketing into the Future: The History and Technology of Soviet Rocketry. p. 120.
  27. Van Pelt, Michel. Rocketing into the Future: The History and Technology of Rocket Planes. pp. 123–125.
  28. Stoiko, Michael. Soviet Rocketry. p. 71.
  29. Stoiko, Michael. Soviet Rocketry. pp. 71–72.
  30. Siddiqi, Asif (Dec 2004). "Russians in Germany: Founding the Post-War Missile Programme". Europe-Asia Studies. 56 (8): 1134.
  31. Siddiqi, Asif (Dec 2004). "Russians in Germany: Founding the Post-War Missile Programme". Europe-Asia Studies. 56 (8): 1135.
  32. Siddiqi, Asif (Dec 2004). "Russians in Germany: Founding the Post-War Missile Programme". Europe-Asia Studies. 56 (8): 1135–1136. doi:10.1080/1465342042000308893.
  33. Chertok, B. (2004). "German Influence in USSR". Acta Astronautica. 55: 735–740. doi:10.1016/j.actaastro.2004.05.025.
  34. Sutton, George (Nov–Dec 2003). "History of Liquid-Propellant Rocket Engines". Journal of Propulsion and Power. 19 (6): 15.
  35. Siddiqi, Asif (July 2003). "The Rockets' Red Glare". Technology and Culture. 44 (3): 493.
  36. Chertok, B. (2004). "German Influence in USSR". Acta Astronautica. 55: 738.
  37. Sutton, George (July 2003). "History of Liquid-Propellant Rocket Engines". Journal of Propulsion and Power. 19 (6): 25.
  38. 1 2 Siddiqi, Asif. "Tupolev". Brittanica Academic. Encyclopedia Brittanica. Retrieved April 4, 2016.
  39. 1 2 3 Siddiqi, Asif. "Sukhoy". Brittanica Academic. Encyclopedia Brittanica. Retrieved April 4, 2016.
  40. 1 2 Siddiqi, Asif. "MiG". Brittanica Academic. Encyclopedia Brittanica. Retrieved April 4, 2016.
  41. Stoiko, Michael (1970). Soviet Rocketry. p. 79.
  42. Stoiko, Michael (1970). Soviet Rocketry. pp. 84–87.
  43. Stoiko, Michael (1970). Soviet Rocketry. p. 93.
  44. Sutton, George (2003). "History of Liquid-Propellant Rocket Engines". Journal of Propulsion and Power. 19 (6): 10.
  45. Stoiko, Michael (1970). Soviet Rocketry. p. 95.
  46. Sutton, George (2003). "History of Liquid-Propellant Rocket Engines". Journal of Propulsion and Power. 19 (6): 19.
  47. 1 2 Stoiko, Michael (1970). Soviet Rocketry. p. 97.

Bibliography

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