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Message: <blockquote data-quote="Austin" data-source="post: 1145" data-attributes="member: 37">Moscow's Air Defense's, Part II: A Parade of Missilesby Michal Fiszer Dec. 9, 2004edefenseonline.com<img src="http://edefenseonline.com/article_images/12_09_2004_IF_illus.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />Illustration by Igor SzablewskiJoseph Stalin died on March 2, 1953, and his death caused a lot of changes in the Soviet Union. Initially, Nikita Khrushchev, Georgiy Malenkov, and Lavrentiy Beria shared authority over the country. But soon Krushchev, Malenkov, and Marshal Georgiy Zhukov – the World War II hero – decided to remove Beria and other "Stalin people." On June 26, 1953, during a session at the Kremlin, Zhukov and Col. Gen. Kiryl Moskalenko, commander of the Moscow Air Defense District, arrested Beria. Moscow Air Defense officers were selected for the operation, since they were deemed the most reliable. Beria was placed for a week at the Moscow Air Defense District's HQs encasement and was later imprisoned in a freshly built empty bunker belonging to the HQs of 1st Special Purpose Army, the main operator of Berkut system. He was kept here until a short trial was conducted December 18-23, 1953. Almost immediately after the trial, Beria was executed by Lt. Gen. Pavel F. Batiskiy, deputy commander of the Moscow Air Defense District. Beria's son Sergei, one of the Berkut's principle architects, was arrested in early July 1953 and placed under house arrest. He was tried and sentenced to banishment from the European part of the Soviet Union. The court also changed his name to Alexandr S. Gegechkoriya, his mother's maiden name. Alexandr Gegechkoriya was sent to Sverdlovsk, where he worked as a senior engineer at a factory for the next 10 years under close supervision by the KGB. Pavel Kuksenko, Sergei Beria's partner, was also relieved of his position but was kept on at KB-1 as secretary of the scientific and technical assembly, a totally unimportant job. In 1955 KB-1 was reorganized under the directorship of S.M. Vladimirskiy. It was divided into three Special Design Bureaus (SKBs). SKB-30, headed by Alexandr A. Raspletin, was responsible for all air-defense systems, including the Berkut. SKB-31, headed by Grigoriy Kisunko, was responsible for strategic anti-missile defense systems. SKB-41, headed by A. A. Kolosov, was responsible for guidance systems for anti-ship and some air-to-air missiles. <img src="http://edefenseonline.com/article_images/12_09_2004_IF_Raspletin.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />In 1955 KB-1 was reorganized into three Special Design Bureaus (SKBs). SKB-30, headed by Alexandr A. Raspletin, shown here, was responsible for all air-defense systems, including the Berkut, as the S-25 program was then known. Soviet intelligence reported that US strategic bombers had been equipped with chaff dispensers that would render the S-25's B-200 fire-control radar ineffective. To solve the problem, system designers provided the S-25 with a moving-target-indicator (MTI) mode. The effort was conducted between 1955-1957, under the direction of Raspletin. The MTI equipment was integrated into the B-200 radar during by 1959. Raspletin often found himself walking a fine line between what Soviet commanders wanted and what was technically possible.AlmazOne of the results of these changes was that Moscow's air-defense system lost the designation Berkut in favor of "Sistema 25" (System 25, or S-25). The system was introduced into service with two types of missiles: the 205 and 207. Both were developed by OKB-301 in Khimki under the lead of Semion Lavochkin. All the missiles of S-25 system were referred to, in general, as V-300s, but product numbers were commonly used by the armed forces to distinguish between versions. The First MissilesThe 205 was the first version of the V-300 missile to enter series production. It was a single-stage missile powered by an Isayev SO9.29A single-chamber (divided into four sub-chambers) liquid-fuel rocket motor generating nine tons of fixed thrust. The engines were produced by No. 456 State Factory in Khimki, No. 586 State Factory in Dnepropetrovsk, and No. 66 State Factory in Zlatoust. The fuel tanks accommodated 460 kg of TG-2 aviation kerosene and 1,740 kg of nitric acid as an oxidizer. The fuel and oxidizer were injected into the engine by pressurized air (the VAD system). The missile's warhead, developed by NII-6 of the Agricultural Machinery Ministry (presently the Federal Chemistry and Mechanics Center) in Moscow, was a blast-fragmentation type, weighing 235 kg. It was controlled by a Doppler-type radio fuze developed by NII-504. The missile was controlled by an APV-301S autopilot with the assistance of "Product 555" radio-guidance equipment after a control nozzle for the initial phase of flight was jettisoned a few seconds after launch. In terms of layout, the 205 missile featured four stabilizers in front and four ailerons on the delta wings mounted at the lower-middle part of the missile body, all controlled by pneumatic servo-mechanisms. The missile weighed 3,570 kg and was 11.6 meters long and 0.65 meters in diameter, with a wingspan of 2.7 meters. The maximum speed of the missile was 1,000 m/sec. (3,600 kmph), and it could engage a target traveling at up to 1,000 kmph. Minimum engagement range was 8 km, and maximum range was 30 km. The engagement altitude was between 5,000 m and 25,000 m. A total of 2,894 V-300 Type 205 missiles were produced by several state factories from 1952 through 1954. In addition, a modified 205A version was manufactured equipped with a hollow-charge warhead However, this was not regarded as a successful variant, and production was quickly terminated.Even as the 205 missile moved toward production, development of additional versions was ongoing. The 206 missile, carrying the unusual designation V-300K3, differed from the basic 205 by using SO9.29B and SO9.29D engines. The first was equipped with a pyrotechnic system for injecting fuel to the engine (PAD system), while the latter was equipped with a gas generator to achieve the same purpose (the ZhAD system). Both engines were tested on stands and were unsuccessful. In the case of the SO9.29B engine, the fuel tanks were destroyed by excessive pressure created by the pyrotechnic system, while the SO9.29D engine experienced severe vibrations. Therefore, no prototype 206 missile was ever built.Development of the 207 missile started in 1952, as the trials with 205 missile were underway. The 207 was powered by an Isayev S2.260 four-chamber rocket motor, generating nine tons of take-off thrust and 4.5 tons of sustained thrust, which was achieved by turning off two of the engine's chambers. This was not the only change in the 207 missile. During one test of the 205 missile, Marshal Mitrofan Nedelin from the Main Missile and Artillery Directorate of the Soviet Ministry of Defense (MoD) was present. (He later served as commander of Strategic Missile Forces and became famous when killed in a R-16 missile disaster at Tyuratam on Oct. 24, 1960.) When the test 205 missile was launched, the jettisoned nozzle-control units fell rather close to Nedelin's observation position. He became angry: "What the hell was that?" When it was explained to him that the nozzles provided control at full thrust during the early stages of flight before the aerodynamic control surfaces could take over take over, Nedelin emphasized that the missile was specified to be single-stage, and in his interpretation, that meant nothing jettisoned after launch to fall to the ground. After all, the outskirts of Moscow were where important Soviet officials had their homes and gardens. At the request of Marshal Nedelin, OKB-301 adopted a new type of nozzle-control unit. The units were made of a special composite that gradually burned out after launch. A smooth transition from gas-dynamic control to aerodynamic control was thus secured, and no missile parts had to be jettisoned after launch. Version 207 missiles were produced in relatively small numbers, since they were soon followed by subsequent variants. A total of 1,137 missiles were produced between 1954-1955. S-25 State TrialsAfter Lavrentiy Beria was arrested, the MoD gained much more control over weapons development for Moscow's air-defense system. Military commanders also got better access, and they immediately demanded so-called "control trials" of the system to be conducted in accordance with standard requirements for state trials. It was expected that comprehensive system trials that had been conducted through September 1953 would form the basis for a decision on accepting the system into service. There was a little room for any radical changes, since S-25 facility construction had already started in 1951. And this was a tremendous job. All the launch pads were built as permanent, with an underground hydraulic erector supplied with pressure by a special compressor, underground electric and control cables, fuel lines for refueling the missile on a pad, concrete roads to every pad, more than 500 km of new connecting roads, bunkers, staff buildings, depots, maintenance facilities, barracks and other facilities for soldiers, HQ bunkers, and A-100 radar positions. An enormous amount of money was spent for the infrastructure, not counting the S-25 system equipment itself: A-100 radars, 56 B-200 radars, more than 3,000 V-300 missiles, as well as command and control, communications, and other equipment. Moreover, the surface-to-air-missile (SAM) positions were connected with two ring-type concrete roads, called Betonka-1 (inner ring) and Betonka-2 (outer ring). On the road maps of the Moscow region they are called A-107 and A-108, respectively. <img src="http://edefenseonline.com/article_images/12_09_2004_IF_207A.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />Two Type 207A missiles for S-25 on display. One missile has its nose painted black, which was done in order to deceive of Western analyzers of satellite photos as to the nature of the seeker. The deception apparently worked, because Western sources claimed that late versions of the V-300 missile were semi-active radar guided. This was incorrect for the simple reason that the B-200 fire-control radar did not support such a guidance method. All S-25 missiles were radio-command controlled. AlmazThus, even if the S-25 didn't meet MoD standards, it was fairly apparent that the system would be accepted into service anyway, given the huge expenditure that had been made. For its part, the MoD said it simply wanted to discover all of the flaws and quirks of the system so that it could force Soviet industry to take care of them before delivery to the armed forces. The control trials were the most complex and difficult tests ever conducted with the S-25 system. For example, generals required that not only parachute-target imitators and slow-moving Tu-4 bombers be used but also the newest Il-28 jet bombers, which were much smaller. Again, no suitable drone was available, and the same technique was adopted for Il-28 targets as for Tu-4 targets but now pilots were to eject at speeds of 800-900 kmph. As might be expected, the first control trials conducted in September-October 1953 did not satisfy the military. During these trials, 33 launches of Version 205 missiles were conducted, which, among others, destroyed four Tu-4s and four Il-28 bombers. Also, a test of simultaneous engagement of four targets was conducted against parachute imitators, with all four being destroyed. But this was not enough for the military commanders, who demanded full-scale state trials, with the use of the serial B-200 radar. A suitable construction at the Kapustin Yar range took some time, and the launching of state trials became possible a year later. In the meantime, training of the system's personnel began. Training Unit No. 2 was temporarily established in October 1952 to conduct the training of thousands of soldiers, non-commissioned officers, and officers. The unit was reformed into the 1st Special Purpose Air Defense Army in December 1954. The official state trials of the 205 missile started on Oct. 1, 1954, and with the 207 missile on Oct. 30, 1954. The state-trials commission was supervised by Marshal of Artillery Nikolay D. Yakovlev. He had just been released from prison after serving a term for his negligence in supervising the S-60 57mm anti-aircraft (AA) gun program. The guns sent to the Korean War in 1951 showed numerous malfunctions, and Yakovlev was accused by Stalin of being at fault. After being released, he was rehabilitated by Krushchev but remained very cautious and supervised the S-25 trials extremely thoroughly. One of the most difficult tests demanded by the military was the simultaneous engagement of 20 targets, which was the maximum capability of the B-200. Twelve Tu-4 bombers dropped 24 parachute-target imitators, and 20 of them were to be destroyed. The test took place in December 1954 and was mostly run by regular military personnel already trained on the system under the new training program. The first attempt at dropping targets by 12 bombers was unsuccessful, when the aircraft formation leader approached the zone from the wrong direction, and they had to make another pass. This annoyance was compounded when one of the 20 missiles took off with no launch command and had to be destroyed. Marshal Yakovlev became very upset. However, the aircraft made a second pass and dropped the targets. The 19 remaining missiles were launched and 18 targets were successfully shot down. It was a good result, and one of the KB-1 representatives, Igor Illarionov, said to Yakovlev, "Did you see it, sir? The system is really good, and the accidental launch is a trifle." Yakovlev replied: "Have you ever been in jail? I have, and it was all for trifles." The cause of the accidental launch turned out not to be so mysterious. It was found that a launch button in the operator room of the B-200 radar was broken in the "pressed" position, so as soon as the power supply to the control panels was turned on, the broken button sent the launch signal. The button had been broken by soldiers cleaning the room that morning who were playing with the launch buttons. The buttons were subsequently redesigned in such a way that, when broken, they disconnected rather than connected the circuit. The S-25 state trials were taken so seriously that four new Tu-16 jet bombers were used as radio-controlled targets and were all shot down, along with 10 Il-28s and 10 Tu-4s. One Il-28 and one Tu-4 target dropped dipoles (chaff) to simulate passive jamming. The S-25 system had not yet been equipped with a moving-target indicator, and it was not easy task to distinguish between real and false targets. But finally the live-firing program ended in December 1954. The military demanded one more trial, this time in a position near Moscow. A randomly selected radar was to pass 24 hours of continuous operation, and every now and then during the test, an aircraft was to approach to enable the crew to conduct simulated engagements. <img src="http://edefenseonline.com/article_images/12_09_2004_IF_S25.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />A Type 217 or 217M missile of the S-25 system. This missile represented an attempt to fix a possibly fatal flaw in the S-25's capabilities. The limitations of previous missiles would enable a supersonic strategic bomber to penetrate the system relatively easily. The Type 217 missile employed a turbo-pump-equipped, two-chamber rocket motor intended to produce more efficient sustained thrust for high-energy engagements. But the pressure was too great for the missile. The Type 217M used a modified engine that succeeded in increasing the missile speed to 1,550 m/sec. and enabled it to engage targets flying at speeds of up to 4,200 kmph. Jerzy GruszczynskiThis test only sounded simple. In fact, the initial radars were plagued by tuning problems and short-lived vacuum tubes. A whole family of vacuum tubes resistant to 15 g called Anod was developed especially for the S-25 system. Most of the Anod tubes were developed by NII-160 (presently the Istok company, which produces microprocessors) in Friazino under Nikolai V. Cherepin. The development was difficult, and at one stage, Lavrentiy Beria asked Cherepin, "How many people from NII-160 are to be executed ["rasstrelat," which means executed by gunshot] before the Anod vacuum tubes will be reliable?" All of the vacuum tubes for various military applications in the Soviet Union at that time were produced in enormous quantities by inexperienced factory workers and technicians new to the industry. The tubes tended to be of dubious quality and had a short lifespan. For example, most of the vacuum tubes for the B-200 radars had a life of only 500 hours, which meant that S-25 personnel in all 56 regiments had to replace half a million vacuum tubes every month. The tuning of the radar was the other major problem. Most of the military personnel had little experience in radio-technical jobs, and despite operating 24 hours a day, many radars were improperly tuned, with most of their engagement channels unusable. The biggest problem was synchronizing all 20 target tracks and calculating the guidance commands for each of the 20 channels. To solve the matter, No. 304 State Factory in Kuntsevo formed SMU-304, a special team that consisted of tuning specialists. Interestingly, V.I. Kyrshev, the present director of NPO Granit (the former OKB-304 of No. 304 Factory) and Vieniamin P. Efremov, general designer of the NPO Antey consortium, started their careers as "tuners" in SMU-304. Into Service, Flawed On May 27, 1954, the Country Air Defense Forces (Protivovozduszna Oborona Strany, or PVO-Strany) became an independent service within the armed forces, equal to the Army, Air Force, and Navy. Marshal Leonid Govorov was appointed as PVO-Strany's first commander. In 1955 he was replaced by Marshal Sergei Biriuzov, who remained at this post till 1962. PVO-Strany consisted of two districts: the Special Moscow Air Defense District, covering the area of the Moscow Military District; and the rest of the country's military districts. It consisted of five armies, each covering a key military district; and 13 independent air-defense corps, each covering less important military districts or some selected areas. The 1st Special Purpose Army, which operated the S-25 system, was created in December 1954. This was not the only air-defense organization in the region. Some other cities in the relatively large area encompassed in the Moscow Military District were protected by AA artillery and – years later – by S-75 and S-125 missile systems. Despite the fact that the S-25 system passed state trials successfully, military leaders did not want to accept it into service at once, feeling that such a huge and complex system had to be properly "brushed off." Hidden flaws had to be uncovered and corrected, and the personnel needed a lot of training to handle the system properly. So commanders insisted that the S-25 be accepted into service for an "experimental period," and only after that would full acceptance for regular service be conferred. The final S-25 test was conducted on April 2, 1955, when the system – manned only by military personnel, with no engineers or technicians from industry – successfully engaged a target at the Kapustin Yar shooting range. Nikita Khrushchev, not understanding the full nature of the system's complexity, ordered the system to be accepted to service thereafter, and this officially happened on May 7, 1955. The question of whether the S-25 was exported to the People's Republic of China in 1958 and to North Korea in 1961 remain unclear. Some sources indicate thus but do not provide any details. Certainly, in neither case was a complete system – or even a single ring – ever built. Probably only feasibility tests were conducted and some technologies incorporated into local air-defense networks. One of the first improvements introduced to the Soviet S-25 system occurred while it was still under construction and involved increasing the number of missiles on every engagement channel from a single missile to two or three missiles in order to increase kill probability. By late 1955, every S-25 regiment could conduct a simultaneous engagement of 20 targets with three missiles each, which meant the launching of 60 missiles in salvos of 20 at short intervals. Thus, each regiment had 60 launching pads. Every group of aircraft could be engaged at least twice – by a regiment on the outer ring and then, if necessary, by a regiment on the inner ring. Despite all of these efforts, though, the S-25 system was accepted into service with a flaw, perhaps a fatal one. It was vulnerable to jamming – even to the most widespread forms of passive countermeasures. Even officers working on S-25 system used to have a verse: Pod Moskvoi na ravnom myestye, Stoit stantsya B-dvyestye. U nyeyo odin ogryekh, Nyet zashchiti od pomyekh! Roughly translated, this means: "Near Moscow on a flat surface, there is a radar B-200. It has a major setback – no resistance to jamming!" Soviet intelligence reported that US strategic bombers had been equipped with chaff dispensers that would render the S-25 ineffective. To solve the problem, system designers provided the S-25 with a moving-target-indicator (MTI) mode. The effort was conducted between 1955-1957, under the direction of A. Raspletin. Some of the elements of the MTI equipment for the S-25 radar were developed by the OKB-304 Design Bureau, at that time belonging to No. 304 State Factory in Kuntsevo, near Moscow. The MTI equipment was integrated into the B-200 radar by 1959. At the same time, coherent-frequency generators and synchronizers replaced quartz-frequency stabilization of all guidance and tracking channels. The generators proved to be much more stable, and tuning requirements were significantly reduced. More Missiles OKB-301 developed the 207A missile during 1953-1954, with production starting in 1955. It was officially accepted into service the following year. The development of 207A was initiated by availability of the new Isayev S2.7151B single-chamber rocket motor. It still had nine tons of continuous thrust, but it burned fuel more efficiently, thus enabling longer burn times. The S2.7151B accelerated the missile to a speed of 1,100 m/sec., and the missile's engagement range increased from 30 to 35 km. The 207A also received a lighter and more effective autopilot, radio-command receiver, and control system. Maneuverability was slightly increased, but the real improvement was a lowering of the minimum engagement altitude from 5,000 m to 3,000 m. More compact and lighter autopilot and guidance equipment enabled an increase in the size of the warhead from 235 kg to 324 kg. The warhead was also of a hollow-charge type that functioned differently from hollow-charge anti-tank warheads. The proximity fuze detonated the warhead not as it passed targets but while the target was 50 m or less in front of it. The warhead explosion was directed toward the front hemisphere instead of spreading out in a spherical pattern. During live-fire tests against Tu-4 aircraft, it was discovered that such a warhead was significantly more effective than traditional blast-fragmentation warheads. <img src="http://edefenseonline.com/article_images/12_09_2004_IF_Pad.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />A launch pad for a V-300 missile of the S-25 system. As modernization of the program progressed, there was some concern that the launch pads would not be able to accommodate the higher launch thrust of more powerful missile versions that were being introduced. This was no small matter, because each regiment had 60 such launch pads, and there were 56 regiments defending Moscow -- 3,360 launch pads, all set in concrete. But the equipment turned out to be up to the task.Jerzy GruszczynskiAll three S-25 missile factories produced 207A missiles, and it can be estimated that nearly 7,000 were delivered between 1955-1957, representing a full system compliment of 3,360 missiles, plus reload stocks and test articles. The 207A3 missile was an alternative version of 207A, equipped with an experimental warhead producing a directional fragmentation blast towards the target based on information from a proximity fuze. The warhead proved complicated and unreliable, however, and was not adopted. The 208 missile was basically similar to the 207A but was powered by a new rocket engine developed by OKB-3 of NII-88, led by Dominic Sevruk. Fuel was injected into the missile by means of pyrotechnically created gases. But, like a similar engine developed for the 206 missile described above, there were frequent fuel tank cracks, and these led to missile explosions. In 1954 work on 208 missile was terminated. <img src="http://edefenseonline.com/article_images/12_09_2004_IF_Trailer.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" />A late version of the V-300 missile on a PR-3M3 transport trailer during the S-25 system's operational period. Already in the late 1970s, some Soviet military commanders raised the prospect of replacing the S-25 as Moscow's air-defense system. It was obvious that the system had exhausted its modernization potential, and it remained unable to engage very low targets, such as the Air Launched Cruised Missiles and Tomahawks that were about to enter service with US forces.AlmazTo increase the effectiveness of the S-25 air-defense system in repulsing mass air raids, the system had to be adapted to engage group targets rather than individual aircraft. Commanders were afraid that large groups of bombers could still break through to Moscow, despite suffering losses of up to 40 aircraft per group in two engagements (a 100% kill rate). To eliminate this possibility, it was decided in 1955 to use nuclear-tipped missiles, with at least one deployed at every regiment. Initially, the intended nuclear warhead was too heavy, and it was planned that a special two-stage 225 missile would be developed, with the first stage powered by solid-fuel PRD-218 engine developed by Ivan Kartukov. In this case, there were no restrictions about "something falling down on inhabited areas," since such a missile was only to be fired in a serious emergency. But finally a 380-kg warhead was developed with a 10-kT yield that could be mounted on a standard 207A missile. Such a missile was developed under the designation 207T, later changed to 215, and accepted into service with the modernized S-25M system by 1962. The attending fire-control radar was designated the B-200M. The most unusual feature of the 215 nuclear missile was the fact that it had redundant guidance and control systems. It had two command receivers, two autopilots, two control systems, etc. One set was engaged at any time, and in the event of a failure or upon the operator's command, it could be switched to the other one, which was operating but not passing commands to the missile's control servo-mechanisms. To realize this configuration, two engagement channels on two different frequencies were used to guide a single 215 missile, which also served to counter enemy jamming. Such precautions were required because of the nuclear warhead and the consequences of lost missile control. The minimum engagement altitude for the nuclear-tipped missile was set at 8,000 m. On Dec. 31, 1957, the Soviet Council of Ministers authorized the production of production of 60 nuclear Type 215 missiles during the first quarter of 1958, but due to delays in production of the PIM-6 warhead trigger, missile delivery was not completed until the end of 1958. Interestingly, a live Type 215 missile test reportedly was conducted in January 1957 in Kapustin Yar. According to the book, USSR Nuclear Weapons Tests and Peaceful Nuclear Explosions: 1949 Through 1990, edited by V. N. Mikhailov and issued in 1996 by the Russian Ministries of Atomic Energy and Defense, only one nuclear test was conducted at Kapustin Yar in 1957. It took place on Jan. 19, 1957, and the yield was confirmed as 10 kT. During the test, two unmanned, radio-controlled Il-28 bombers flying in a wide formation were successfully destroyed at an altitude of 10,000 m.Three other nuclear tests were conducted with the use of Type 215 missiles in 1962. They were also launched from Kapustin Yar, which was actually a missile test range and not typically a nuclear range. Most Soviet nuclear tests were conducted on special nuclear ranges at Semipalatynsk in Kazakhstan or on the island of Novaya Zemlya in the Artic Ocean. But as the nuclear ranges did not have any facilities for launching S-25 missiles, Kapustin Yar was used instead. This time, a series of high-altitude nuclear-explosion tests were planned, probably related to studying electromagnetic-pulse (EMP) effects. KB-1 was tasked with providing missiles to carry a 300-kT warhead to altitudes of 20 km and 50 km. The 20-km test, called Operation Groza, was to use the 215 missile, while the 50-km test, known as Operation Grom, was to be conducted with the one of Kisunko's anti-ballistic missiles (ABMs). Both missiles were to climb vertically, and the warhead was to be detonated at a preset altitude by a barometric altimeter device. The first two tests ended in failure when the barometric altimeters triggered the nuclear warhead at 4 km instead of 20 km. The third test involving the 215 missile was successful, with the missile exploding at 20 km as planned. In 1954 it was decided that the Moscow air-defense system was to receive missiles capable of engaging supersonic targets. The limitations of the 205, 207, 207A, and 215 missiles would enable a supersonic strategic bomber to penetrate the system relatively easily. To enable the missile to intercept a fast-moving target, it was necessary to increase the speed of missile itself. Therefore, a much more powerful engine was needed, but such an engine would consume too much fuel. When the engine was fed with fuel by air pressure, it was not possible to adjust the engine thrust, so a turbo-pump was necessary. In 1954 Dominik Sevruk developed a series of turbo-pump-equipped, two-chamber rocket motors: the S3.40, S3.41, and S3.42. Each of these motors had a launch thrust of 17 tons and a sustained thrust of five tons. Tests of 217 missiles equipped with S3.42 engines started in 1957 but were mostly unsuccessful due to engine and missile explosions after launch. Sevruk blamed Lavochkin for errors in the design of the missile part of fuel system. After a severe dispute between both designers, Lavochkin decided to use only Isayev engines in the future, but soon the 217 missile program was terminated. Another attempt to build a fast missile for the S-25 system was undertaken shortly afterward. At Lavochkin's request, some documentation concerning the S3.42 engine was passed through NII-88 to Isayev's KB-2, where Nikolay I. Leontiev used it as the basis for the S5.1A engine. A Type 207A missile equipped with an S5.1A engine was designated the 217A. Tests of this configuration, conducted in 1959 and 1960, were more successful. But already decision-makers were saying that they wanted a more maneuverable missile for the S-25 rather than a faster one. Thus, work on the 217A was terminated in 1960. Second S-25 ModernizationIn the spring of 1958, Soviet intelligence reported on US plans to deploy F-101C Voodoo fighters to the 81st Fighter-Bomber Wing in the UK, and that the nuclear-armed aircraft were to have targets assigned in the eastern part of the Soviet Union, possibly including Moscow. Such strikes were to be one-way missions, and it was arguable whether such operations would ever be undertaken by the wing. Nevertheless, Soviet analysts concluded that the trend toward long-range tactical aircraft would continue and that it was only a matter of time before Moscow was truly under threat from fast and maneuverable fighter-bombers. Therefore, on June 4, 1958, a decision was issued to adapt the S-25M system so that it could engage tactical aircraft. Requirements specified that the system should have the ability to engage and destroy a "MiG-19-size" aircraft at altitudes between 1,500 and 30,000 m. The minimum altitude of 1,500 m was a compromise between designers and the military commanders, who wanted the requirement to read at any altitude up to 30,000 m. Raspletin told them that such a capability would not be possible without developing a totally new system. To meet the requirements, three options were considered: replacing radar antennas with bigger ones, using more sensitive receivers, or using more powerful transmitters. Under the direction of Aleksandr L. Mints, director of the Radio-Technical Institute of the Soviet Academy of Science, Nikolai Oganov from KB-1 developed a new transmitter with a power output five-times greater than the current one (10 MW instead of 2 MW). The second element of the program would be to develop faster and more maneuverable missiles capable of engaging supersonic, evading targets. Development of such missiles had been attempted earlier but failed due to engine problems. The Type 217A missile with the S5.1A engine was considered the most promising starting point, and it was decided to concentrate on purging the pairing of its flaws and shortcomings. The S5.1A engine was further developed to have more thrust and fuel. The new engine, called the S5.41, had controlled thrust in the range of 17 tons for take-off to three tons sustained and was equipped with a pneumatic/hydraulic turbo-pump. The engines were produced by No. 26 State Factory in Ufa and No. 13 State Factory in Ust-Katav. The use of the more powerful engine increased the missile's speed to 1,550 m/sec. and enabled it to engage targets flying at speeds of up to 4,200 kmph. The missile's range was increased to 43 km and the maximum engagement altitude to 30,000 m. Minimum engagement altitude was 1,500 m. In a special guidance mode, when a ballistic flyout was also used, the range was increasing to 56 km and the maximum engagement altitude to 35,000 m. Further changes were made to the warhead, which had a steerable sector of blast fragments and a new E-802M pulse-type radar fuze in place of the RV-515 Doppler-type fuze. For the first time, titanium was used in missile construction, which enabled it to maneuver at higher G forces. Aerodynamic controls were improved to work at higher speeds. In the beginning, the designers were worried about whether the existing launch pads would withstand the increased engine thrust of the 217M missile. Changing the launch pads would be a very difficult job, since their bases were put into concrete at the launch positions. However, tests showed that the launch pads were capable of withstanding up to 19 tons of thrust, and there was no need for change. Tests of 217M missile were conducted from 1959-1961. It was accepted to service in 1962, and its production started in Tushino in the same year. One of the two missile factories that had been dedicated to support V-300 missile production had been retooled to manufacture V-750 missiles for the S-75 (SA-2) system The Final Modernizations: S-25MA, S-25MAM, and S-25MR One of the main shortcomings of the previous modernization was its continued inability to engage low-flying targets, and in 1965 Soviet analysts concluded that US strategic bombers would be able to use low altitude for long periods of time while approaching targets. Another problem was the advent of nuclear attack missiles, such as the AGM-28 Hound Dog, which could also fly relatively low. One aspect of the effort to improve the low-level capabilities of the S-25 system was to lower the angle of the azimuth antenna. Also, more modern analog-type computing devices, as well as more advanced high-frequency amplifiers, were employed. As result, the kill probability for low-altitude engagements improved, although initially the lower engagement zone remained at 1,500 m because of ground clutter. Yet radar resistance to active jamming was also improved. A new missile was also put into development for the modernized system. Semion Lavochkin died of a heart attack on June 9, 1960. In 1962 all authority for further development of V-300 missiles was passed to the OKB-82 Design Bureau of the Tushino factory, led by Alexandr V. Potapalov. All subsequent V-300 missile variants through the early 1980s carried the prefix "5Ya," according to new Main Missile and Artillery Directorate of Soviet General Staff (GRAU) regulations. Confusingly, the designation was not only in force for V-300 missiles (5Ya25 and 5Ya24) but also the V-750 missiles from the S-75 family (5Ya23 and 5Ya29), and further adding to the confusion, some missiles from other bureaus carried similar designations (5Ya26 and 5Ya27). The 5Ya25 entered development in 1965. The version received quicker servo-mechanisms and a new autopilot, with improved modes of stabilization and missile control. These increased the missile's maneuverability. The new Isayev 5D25 engine had the same thrust as the S5.41 but burned for longer time, thereby increasing missile energy, although the boundaries of the engagement zone did not change. The missile also received improved a 390-kg directional-fragmentation warhead. The 5Ya25 missile was also called 217MA at the design bureau. The last modernization of the S-25 was conducted in two phases. The first phase was run by OKB-304 (later known as NPO Granit) with the cooperation of the technical service of the 1st Special Purpose Army. The second phase was run by the military alone. During the first phase, new analog-digital computing blocks were added to the B-200MA radar that enabled signal processing to eliminate ground clutter. Now the lower engagement zone was limited only by the maneuver characteristics of the V-300 missiles, which could be prone to hitting the ground when maneuvering at very low altitudes due to the guidance-control software. Effective minimum altitude for the system was reduced to 800 m with the use of the 5Ya25M missile, which was introduced into service in 1976. It was lowered even further to 500 m with the introduction of the 5Ya24 missile in 1980. The modernized system was designated the S-25MAM, and it was declared operational 1979. During the second phase of the modernization, some new anti-jamming capabilities were added to the B-200 radar, including frequency agility and more advanced signal processing. After the modernization was completed in the early 1980s, the system was called the S-25MR. The S-25MR was also adapted for using the 5Ya24 and 44N6 (nuclear) missiles (see below). A modernized 5Ya25M missile received a new, more sensitive 5Kh48 radar fuze that was effective against targets with a radar cross-section of 0.3 sq. m. The fuze's capabilities matched those of the modernized radar for the detection of small-size targets flying at speeds of up to 4,300 kmph, such as the Short Range Attack Missile (SRAM). In the design bureau, the missile was also known as the 217MAM. It was produced by Tushino from 1975 through 1980. The last conventional version of the V-300 missile family entered production in 1980 and was produced until 1986. The missile had a new 5U31 jam-resistant guidance-command receiver that was able to change to pre-selected frequencies if facing strong radio-frequency jamming. The transmitter also changed to the next frequency in sequence if contact with the missile was lost. The missile also had a modified 5D25N engine that controlled thrust according to required maneuver characteristics. Improved maneuverability enabled the missile to attack more agile targets. The minimum engagement altitude was lowered to 500 m. The maximum engagement altitudes were 30,000 with start-to-finish command guidance and 35,000 m with an initial ballistic trajectory. Maximum engagement distance was 47 km and, with the use of a ballistic trajectory, up to 60 km. A small number of nuclear missiles were built for the modernized system, based on the 5Ya24 missile. The missile was designated the 44N6 and entered production in 1982. The warhead was of a nominal 10-kT yield and had a special device that reduced its yield when used at low altitudes. This enabled the nuclear-engagement zone to be reduced to 3,500 m. The remaining parameters were equal to 5Ya24 missile, in that the ballistic mode could be used to increase the engagement envelope. The 44N6 was also called the 219 in the design bureau. This was the last V-300 version to enter service with the S-25 system. Already in the late 1970s, some Soviet military commanders raised the prospect of replacing the S-25 as Moscow's air-defense system. It was obvious that the system had exhausted its modernization potential, and it remained unable to engage very low targets, such as the Air Launched Cruise Missiles (ALCMs) and the Tomahawks that were about to enter service with US forces. The decision was finally made in 1980, and the dismantling of the world's most extensive air-defense system started in 1984. As of 1993, the S-25 has been completely replaced by the S-300PT/PM.</blockquote>

Verification: What year did the first man go to space? (answer has 4 numbers)