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Aviation History
1964
1964 - 2140.PDF
FLIGHT Internationa/, 23 July 1964 161 possible: if dispersion were no problem, it could be fired upwards. Ignition of the Cuckoo is effected by a timing mechanism, with back-up signalling provided by a Phillips ionization valve (a device extremely sensitive to the presence of any atmosphere). There remains the problem of separating the test body from the spent second stage, in order that the former may be studied in isolation. Assuming the number of Imp motors fitted to the sabot suffice to impart an additional downward velocity of 400ft/sec, then to achieve a vertical separation of 20,000ft the head-separation must be initiated 50sec before the event under investigation. Ideally, the Cuckoo should cease burning less than a second earlier still. It is therefore likely that the second stage will burn out at between 1,000,000 and 750,000ft, and immediately afterwards the sabot ring, together with the re-entry body, will be disconnected and blown off downwards by the sudden jerk from the Imps. The sabot remains connected to the second stage by means of an undrawn nylon lanyard, and when this has stretched sufficiently it pulls the sabot clear of the re-entry body and allows the latter to continue falling by itself. Both the Cuckoo burn and the spurt of flame from the Imps can be seen by the ground optics. Peak head velocity occurs at about 200,000ft, by which time the head should be at least 20,000ft below any debris. Velocity from 200,000 down to 150,000ft is usually approximately constant, depending upon the shape of the body, and it is over this stretch of trajectory and down to 100,000ft that the most important readings are obtained. The telemetry works throughout the mission, providing information on guidance, control, propulsion and other parameters, but the critical measurements on the re-entry head are recorded on magnetic tape. One of the great advantages of the Woomera Range is that after each firing everything not burnt up during re-entry falls on land and can be recovered. It is therefore possible to armour and thermally insulate a tape recorder to enable it to survive re-entry (if necessary, even after disintegration of the vehicle carrying it) and subsequent hard landing on the ground. This enables continuous readings to be obtained throughout the period of re-entry during which a heavy ionization cloud surrounding the body may blanket telemetry transmission. The recorder is made in industry to a design by the R.AE Instruments and Electrical Engineering Department. The tape has multiple channels recording head erosion, temperatures and signals from accelerometers and rate-gyros. It is basically a steel sphere in an ablating (Durestos) cover. Ground impact may be some 60 miles down range. Ground instrumentation is also used to track the head and study both it and the ionized wake behind it. Details of the equip- ment used are given presently. Programme Development Until the demise of Blue Streak as a missile the Black Knight programme was purely a British defence exercise. Subsequently discussions were held with the US Government which confirmed the substantial advantages of co-operation between the two nations in the field of re-entry research. In some of the first Black Knight firings the re-entry ionization gave rise to unexpected glows and other optical effects, and one of the first fruits of co-operation was the Gaslight programme, which brought specialized US equipment to Woomera to study the re-entry glow. In 1961 a more far-reaching agreement between the US, Britain and Australia was proposed; it was put into effect as Project Dazzle in 1963. This agreement bears witness both to the excellent suit- ability of Black Knight for re-entry research and to the clear skies and overland recovery at the Woomera Range. Under the terms of Dazzle, Australia provides WRE ground personnel, range equipment and flight data for subsequent analysis; Britain provides all flight hardware and co-ordinates the programme. Data are shared between Britain, Australia and the US, and the US provides special ground instrumentation. Cognizant authority in the US is the Advanced Research Projects Agency of the Department of Defense. Nevertheless, Dazzle is not part of ARPA's existing Project Defender, and does not duplicate current American research. In the UK the programme is co-ordinated by Ministry of Aviation Director/Space, Mr C. J. Stephens. Shapes and materials of test re-entry bodies are agreed between Britain and the US, and manufactured in the former country. The Dazzle programme can be regarded from either an offensive or defensive viewpoint and, while it could provide data which would be needed in the development of British re-entry Black Knight tape recorder and protective case vehicles, it also produces the essential information on re-entry phenomena necessary to a ballistic-missile defensive system. The main purpose behind the Black Knight experiments appears to be purely scientific, and everything possible is being done to find out more about what actually happens during re-entry, and to explore the complex and constantly varying conditions. Flow around the body may be laminar or turbulent; dissociation and re-association of gas molecules gives rise to chemical changes; ablation and progressive disintegration of the body causes high- temperature particles to separate from the body and be left behind in the wake; and the layer of ionized gas around the body blankets radio transmission. Research is also in hand on the re-entry of differently shaped bodies; spherical heads are used as a datum, but warheads tend to be more or less conical. It is also essential to investigate heat-sink bodies and those of the ablative type, and in the latter case to evaluate the properties of different classes of eroding materials. It is practically impossible to predict or calculate re-entry phenomena, and exceedingly difficult to study them in a range or laboratory tunnel. The Royal Armament R & D Establishment at Fort Halstead, Kent, is carrying out a series of small-scale experi- ments in their hypervelocity range, while more ambitious trials have been undertaken by CARDE at Valcartier, Quebec (some under US contracts). These data will provide basic information essential to a full understanding of the Dazzle flight results. Further support has come from the RRE at Malvern, which has overall responsibility for the interpretation and analysis of all radar data obtained during re-entry. Possibly the most outstanding piece of ground instrumentation in the Dazzle programme is a very special high-power radar developed by Stanford Research Institute, of Menlo Park, Calif. Its purpose is purely diagnostic: to study the properties of the head and wake on re-entry, and find out everything that can be learnt by electromagnetic measurement. It has an 86ft dish, and two aerial systems simultaneously on 55 and 153Mc/s. It can lock-on to the re-entering head, and is located on the Woomera range near Mount Eba. The other major contribution from the US is a pair of electro- optical laboratories produced by Barnes Engineering Co, of Stamford, Conn. Each of the latter includes a Nike Ajax radar mount carrying 8001b of instrumentation which includes radio- meters, ultra-violet photometers and spectrometers, with automatic data-recording. Each instrument can be slaved to radar or IR acquisition systems, or to a visual telescope, and can be trained manually via a joystick. Both the SRI radar and the Barnes trackers must be helped on to the target. To overcome target dispersion within the very limited time available, the target is tracked by a pair of FPS-16 high- accuracy radars, one at Red Lake and the other at Mirkata, which lock-on to a C-band transponder on the second stage. Ideally the transponder should be on the head, but it would spoil the re-entry shape; accordingly, it is essential to extrapolate for the difference in altitude between the second stage and the head. Once acquired, the head is tracked automatically by the SRI radar, and the Barnes electro-optics are slaved either to this or to the manual controllers with their telescopes. Six Dazzle rounds remain to be fired. Beyond this there is no formal agreement, although the investment in special facilities would make a new agreement between the MoA and ARPA appear
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