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Aviation History
1956
1956 - 0648.PDF
648 FLIGHT The Truth about German Guided Weapons Reflections on the Recent Munich Symposium By A. R. WEYL, A.F.R.Ae.S. WHEN Hitlerite Germany collapsed eleven yean ago, the Alliesfound a wealth of accomplishment in the guided-weapons field,which was unsuspected even after the evidence of V-l and V-2. Attempts were made to gather in all this information; but for variousreasons, personal and material, the reports into which much of it was condensed were often of little value, incomplete and, occasionally,directly misleading. One cannot do much with an official report describ- ing ballistic experimentation which confounds one with "driving mirror"where the German expert meant "sabot," or with "undernourished bodies" where "slender shapes" are intended! Besides, "Security"clamped down on many reports, thus denying to many workers the information to which they were entitled. When Western Germany joined NATO a year ago, Professor Dr.Theodore Von Karman, an eminent scientist and also founder-chairman of the Advisory Group of Aeronautical Research and Developmentwithin NATO, proposed to establish, once and for all, the advances which the Germans had made in the guided-weapons field. It is no usedenying that, despite immense efforts, the Western powers have pro- duced few, if any, new ideas; nearly all current developments are basedupon German work, whatever ministers and publicity departments may assure the public. The work done with so much money and men hasproduced nothing more than unproved manufacture and testing tech- niques, better detail design with some new features, and a collection ofpractical experience. There is, therefore, a very good cause for review- ing the German work thoroughly, notwithstanding the fact that it isnow at least eleven years old. Beyond that, Von Karman intended to promote a get-together ofexperts on the Western side for a frank and personal exchange of opinions on basic problems (unchanged since 1945). In this respect,too, the symposium was successful, although it was sad to note that, officially, this country had seen fit to despatch only about three people,whilst the U.S. contingent was more than ten times as strong. Delegates from Britain, Belgium, Denmark, France, Western Germany, Holland,Italy, Norway, Spain, Switzerland, Turkey and the U.S.A. attended, with the Americans and the Germans forming the majority. "Security"was not in evidence. Between April 23 and 27 no less than 27 papers were scheduled, allrendered in English, French and German. A paper by Secretary of State Professor L. Brandt, an eager spirit in West German aviation,was not read; Dr. W. Von Braun, too, was missing, but his paper was read for him (according to German dailies, Von Braun had been refused-security clearance to attend). Most lecturers, all authorities in their field, came from Germany; seven came from the U.S.A. (mostly fromRedstone Arsenal); two from France; one from Britain (R.A.E.); and one from Spain. Preparations for the symposium had been made by the Wissenschaft-liche Gesellschaft fur Luftfahn (WGL), the German equivalent of the Royal Aeronautical Society. The organization worked admirably, beingsmooth and efficient. The few social events—an evening in a beer hall, and a delightful night cruise on the beautiful Starnberger See—werethe more enjoyable for being unencumbered by after-dinner orators. Discussions were short, to the point and unafflicted by the liking of someBritish learned societies for calling upon V.I.P.s to vent their inability to express themselves. A few brief opening addresses were given, amongthem one by the West German Defence Minister, Herr Theodor Blank, who pointed out that the German war effort should be well exploitedto arm NATO. Projectiles and Aircraft Dr. Th. Benecke, a Bonn official and an organizer of the meeting, saidthat guided missiles owed their origin to the blending of projectiles with aircraft. When aerodynamic experience, accomplishment of automaticaircraft control, and modern high-frequency technique came together, practical guided missiles were possible. The V-2 emphasized the pro-jectile, V-l and Hs293 the aircraft, aspects of such a merger. Related to the controllable glide bomb (SD. 1400-X, alias Fritz-X, the "X" because ofthe'cross-wing arrangement). Later developments against Allied bombers included weapons such as WasserftUl, Rheintochter, Enzian, Schmetter-ling (Hsll7), and "X-4." The first two were supersonic, and the X-4 fighter rocket was wire-guided. The idea of the V-2 was, originally, scheduled as a replacement forthe heavy artillery which the Versailles Treaty prohibited. The deci- sion to develop such a weapon was taken in 1929, but experimentationbegan in 1932, when Dornberger and, later, W. Von Braun (as assistant of H. Oberth) were installed at the Kummersdorf proving ground.The first V-2 (more correctly, A.4) reached 56 miles' altitude and 5,000 ft/sec on October 3, 1942, from a vertical ascent—a feat neverequalled by any gun in the world. The weapon became operational in September 1944; altogether, 1,115 were fired against England, andanother 2,050 against Belgian cities. Proposals to develop the V-l flying bomb had originally been turneddown because of its poor accuracy. Later, it was taken up as a weapon of retaliation. Within two years, not only had the development beencompleted but trials and training had been conducted, and mass pro- duction was in hand, with 5,000 missiles already in store. The Fritz-X controlled glide-bomb dates from 1938, when the D.V.L.was charged with the problem; the final trials were made in Italy. The wing spoiler control gave a surprisingly high accuracy: 50 per cent hitswere obtained inside a 16Jft square, from altitudes between 13,000 and 23,000ft. Operational use brought early successes against Allied war- ships in the Mediterranean in August 1943. Shortly afterwards, thtHs293, also, became operational. This auxiliary-rocket-propelled glide- bomb had been developed inside 12 months; while Fritz-X was for useagainst armoured warships, the 500 kg mine bomb carried by Hs293 was effective only against vessels with little protection. For ranges up to7i miles, accuracy was about the same as that for Fritz-X; similar, too, was the maximum speed of 660 ft/sec. Not less than 40 per cent ofall operationally launched Fritz-X and Hs293 produced hits, despite purely visual guidance.Enemy interference with the radio control took place, but was entirely ineffective; operational versions of both weapons were prepared withwire-guidance, with ranges up to 11.2 miles, but proved superfluous. None of the other guided weapons became operational. VPasserfall,however, provided the basis for the American Nike development. In the discussion, the present writer (at one time in charge of G.W.development) briefly surveyed work done before the period covered by the lecturer. Reference was made to the efforts of Werner Siemens andWilhelm v. Siemens which culminated during the First World War in full-scale trials from airships and aeroplanes with nearly 90 wire-guidedglide bombs and airborne marine-torpedoes. Since 1910 Christian Wirth had demonstrated the coded radio-control of boats and airship models.The developments by the Reichswehr and Navy during 1925 and 1929 had anticipated some of the more recent achievements.Dr. Herbert Wagner (Van Nuys, California) described the Henschel missile development for which he had been responsible. He was askedin 1940 to design a steerable glide-bomb against shipping. Emphasis was laid upon a simple method for the control of such a bomb from alaunching aircraft. It was thought practical to neglect the phugoid and rely solely upon damping the short-amplitude incidence oscillation. Thus,longitudinally, automatic stabilization was unnecessary. The rudder was omitted. Air-brakes behind the wing tips prevented speeds exceed-ing M = 0.85, and care was taken to avoid inaccuracies in production. The first trials suffered from frequent electronic-valve failures and redguide flares with less smoke had to be adopted. The Hs293C and the larger Hs294 were torpedo-carrying glide bombs.They released marine torpedoes upon entering the water. A supersonic (M -1.5) guided missile, the Zitterochen, was under development. The Hsll7 Schmetterling of 1943 remained the only guided weaponfor which production orders had been given before the war ended. It was a swept-winged high-subsonic anti-aircraft missile. Two boosterrockets launched it, the lower rocket being fired somewhat in advance of the upper. Radio-control was on 40 cm waves; Wagner admittedthat enemy jamming might soon have rendered it operationally useless. An infra-red homing head was to be incorporated. Control Systems Dr. Max Kramer (now in California) gave a lively account of thedevelopment of his Fritz-X, X-4 and X-7 with their spoiler control. Dr. E. E. Fischel (Caldwell, U.S.A) had been working on automaticpilots for Siemens before taking over the telecontrol development of the Deutsche Forschungsanstalt fur Segelflugzeug between 1941 and 1945.This work reached from the mathematics of pursuit curves to the design and testing of guidance and stabilization apparatus. It was, so heclaimed, so important that his laboratories at Aiming had been exempted from bombing by the Allies so as to keep his files and equipment intact. Fischel developed simulator training-devices. Three guidance controlgroups were considered: three-point aiming by optically aligning the missile and target; television guidance; and beam-nder guidance. Thefinal simulator could suit subsonic and supersonic missiles, as well as those with plane wings and cross-wings (cartesian and polar controlled)by using electronic computers. He had also worked on the guidance of a turbojet-propelled V-l of improved accuracy, essentially with beam-guidance for initial direction. A command transmission of ultra-violet- ray impulses was immune to interference but was ineffective when thesun was shining upon the photocell. The problem of a gyro-stabilized telescope for bomb aimers could not be solved, neither could the pre-paration of an infra-red homing head for night effects. Dipl. Ing. H. Temme read a paper on the V-l control. A maximum(50 per cent) dispersion of + 2.8 miles at 140 miles range was demanded. Considerable difficulties were caused during trials, by the vibration fromthe pulsejet. DipL-Ing G. Ernst (now in France) discussed the spoiler control ofmissiles with Max Kramer on the X-missiles. He pointed out that spoilers had small control forces, but suffered from lag.Dr. Hermann H. Kurzweg (formerly Peenemunde's chief aerodyna- micist, now chief of the Aeroballistic Research Department of theU.S. Navy Ordnance Laboratory) described the supersonic research at Peenemunde for V-2 and Wasserfall. The latter was more difficultaerodynamically because its flight was subsonic as well as supersonic, the German experimenters often had to adopt inferior solutions tcavoid interfering with production. Dr.-Ing. Otto Muller (now in France) described the controls of thtV-2 rocket. The correct instant of burn-out (for control of range) was determined by radio signal using the Doppler effect; alternatively, theacceleration was integrated internally. For this, either the precession of a gyroscope under acceleration or an electrically fettered pendulum wasused, in combination with the charging of an electrolytic cell. The Doppler method proved at first more accurate; later, however, theintegration method yielded slightly reduced dispersion (values of about the same order as those quoted for V-l). To compensate the course
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