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Aviation History
1961
1961 - 1596.PDF
M t S SIL E S 196 1 solid-propellant motors arranged in tandem. Aerojet-General have chosen a cast polyure- thane/perchlorate composite solid propellant, with an aluminium additive to prevent un- stable combustion and increase specific im- pulse. To reduce the overall length of the vehicle each stage has four small nozzles, all provided with ring-like jetevators to control the trajectory in pitch, yaw and roll. Motor cases in the A-l missile are fabricated by precision-welding high-strength stainless- steel sheet. The second stage incorporates thrust-termination ports, and unusually com- plex ignition, destruct and safety systems are necessary for submarine use. Ignition takes place as soon as the missile breaks the surface of the sea. Actual underwater launchings have demonstrated the ability of the control system and jetevators to correct for exits as much as 40 from the vertical. During first-stage propulsion the missile is gradually tilted over towards the target, and the first stage burns out and separates at a height of about 12 miles. The second stage then ignites, and is cut off when the missile arrives on the correct trajec- tory at the exact speed for the range demanded. The warhead than separates. Yield of the original warhead is said to be 0.5MT, a modest figure which, coupled with revolutionary design, was instrumental in enabling the re-entry vehicle to be made very much smaller than any others. Although the nosecone is essentially of the heat-sink type, the re-entry configuration set a new standard which has since been followed by all the larger ablative models for the ICBMs. During the launch the nose is protected by a rigid plastic envelope, which burns up during re-entry. Notwithstanding the great difficulty of guiding a submarine-launched missile to a distant target, the circular error probability (accuracy) of Polaris is stated to be "of a high degree"; unofficial statements suggest that it 00 may be of the order of half a mile. To achieve such accuracy, the submarine must know its own position at the moment of firing and also the exact relative position of the target. The heart of the submarine's navigation system is SINS (ship's inertial navigation system), chief contractors for which are jointly NAA Auto- netics and Sperry. Several systems are inte- grated to provide cross-checks on each other, and gyroscopes and acceterometers not only continuously record position but also monitor the ship motion and attitude, for, even at a depth of 80ft, the vessel may pitch or roll slightly. General Electric, at Pittsfield, supply the fire-control system, which feeds a con- tinuous flow of co-ordinated information into the missile up to the moment of firing. The signals include position of the launch tube, true north, target location and trajectory to be flown. It can prepare missiles for launching at the rate of approximately one per minute. Major contractors for checkout equipment are Nortronics and Lockheed Electronics, while Interstate Electronics are a major supplier of instrumentation. Westinghouse Electric is the contractor for launching and handling systems, and the all-inertial airborne portion of the guidance system is being produced by two teams, led by GE and Hughes, the original system having been designed by MIT. Testing of the A-IX series of vehicles started in September 1958, and the first with a live second stage accomplished all test objectives on May 8, 1959. Three months later a missile was launched successfully from a ship-motion simulator at Cape Canaveral, and only two weeks afterwards another was successfully launched from a tube mounted on the surface ship USS Observation Island. Meanwhile, tests aimed at developing the ejection and under- water-launch capability were carried out off San Clemente Island and at other California locations. The Navy has suggested 45 as being the optimum number of submarines for the most efficient implementation of the Fleet Ballistic Launch of the Polaris A-l from submerged submarines is now a routine operation. In this photograph a missile is seen shortly after first-stage ignition, after pneumatic expulsion at a depth of 80ft FLIGHT, 2 November 1961 Missile System on a world-wide basis. To date, 29 submarines have been requested, the last ten being on an accelerated basis to enable all 29 to be operational by early 1965. The first five have a displacement of 5,400 short tons surfaced and 6,700 submerged, and are 380ft long. These submarines are USS George Washington, Patrick Henry, Robert E. Lee, Theodore Roosevelt and Abraham Lincoln, and all are in commission. The first-named con- ducted the two pioneer underwater launches on July 20 last year, and the first four ships are on what the Navy is pleased to call "peace patrol." The next class of ships, which are steadily being completed, are of 6,900/8,600 tons displacement, and are 410ft long. All the ships at present in commission are equipped to fire the A-l missile. Polaris A-2, with a design range of 1,500 n.m., differs externally from the earlier missile only in being 3ft longer. When the first five ships are over- hauled (probably three years from commis- sioning) minor modification will permit them to be re-armed with the longer-range missiles, bringing them up to the standard of the remaining 24 ships. Polaris A-2 has an entirely new second-stage motor case made of reinforced plastics. The Spiralloy process patented by Hercules Powder Co combines 267,930 miles of glass filaments and epoxy resin to produce a low-density shell of extreme strength. Similar designs of second- stage cases are made by Aerojet-General and B. F. Goodrich. The complete motor, assem- bled at Allegany Ballistics Laboratory, con- tains a new propellant of increased specific impulse, which is responsible for most of the extension in range. Flight trials of Polaris A-2 began on November 10, 1960. The programme has been intensive, no fewer than 10 A-2s having been launched by May 9, and the current total being approximately 17. Several of the most recent firings have been from the trials ship Observa- tion Island. Underwater launches have begun with firings from Ethan Allen, the first of the larger FBM submarines, which launched her first A-l missile on October 16, followed by an A-2 on October 23. At the time of writing, the ultimate firm Polaris development is the A-3, with a design range of 2,500 n.m. President Kennedy has requested that development of this weapon be accelerated, so that it may be available in 1964. Few details of its design have been divulged, apart from what was contained on page 414 of Flight for September 14 of this year. It was then reported that severe troubles had been encountered by Aerojet-General in attempting combustion conditions with the double-base fuel in the first stage of 6,300/ 6,600°F and 8OO/9OOlb/ sq in. These conditions are indeed ambitious, yet any reduction would be reflected in corresponding curtailment of range. The cases, however, appear to be relatively trouble-free, both being of filament- wound glass stressed to 80,0001b/sq in and weighing only 8001b (first stage) and 2001b (second). Proof pressure for these cases is 945 and 342lb/sq in respectively. SNARE THIS aerodynamic-cruise strategic weapon is no longer in service with the US Air Force. Details were given in our four previous reviews. SOVIET MISSILES PIECING together a picture of Soviet strategic weapons is always a bricks-without-straw operation. Practically all details of such weapons are closely shrouded by security, and part of what follows is necessarily deduction or even supposition. It is generally considered that all the Russian space launchings have been boosted by vehicles of a basically military nature, although the payload/vetotity per-
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