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Aviation History
1957
1957 - 1204.PDF
292 FLIGHT, 30 August 1957 BLOODHOUND . . . > it would require the rate-sensing capacity o£ an autopilot to meet thesituation. Once the principle of movable wings has been accepted, theirdifferential operation is a foregone conclusion. In a missile their advantages are considerable. Essentially, the whole power-pack andoperating mechanism can be grouped in the middle of the aircraft, thus avoiding the necessity for external linkages to tail or nose guidancesurfaces. The process of Thinking by which this original configuration wasreached must have been somewhat this way. Symmetry is highly desirable in a missile, to ease control and to reduce sensitivity toattitude. In the case of a rocKet, two-plane symmetry is a "11310X31" with the small nozzle easily accommodated in the tail ot the body. Thelarger-diameter ramjet is more ot a piooiem: to obtain optimum efficiency, tne direct approach is essential tor air intake and jet outlet—so tne ramjet must be mounted clear of the luseiage boundary layer. There are several possibilities, such as the wing-tips, but that chosenfor the Bloodhound is about as neat as it is possiDle to imagine. From this louow two tactors. The side aiea oi the missile boay plusthat oi the two 1'hor ramjets is sulhcient, when suitably disposed about the e.g., to provide full static and dynamic stability in yaw, withoutthe need for any fans. Steering is, theretore, entirely by roil and pitch. Tne main pianes have thin doubie-weage aeioious, with sharp lead-ing and trailing edges; the line of maximum thicJsness is at about 4a per cent ol the mean chord and, according to a Bristol drawing,is swept back 5 deg. The taper is almost equai on leading and trailing edges, but is disguised by the cut-back "Mach angle" tips. (It may berecalled that the Miles M.52 supersonic project, "axed" in 1947, had just this lorm of wing tip.) Tne wing tapers in thickness from rootto tip, the latter havmg a maximum depth of about an inch. The all- moving surface—it is pivoted about a tubular spar just aft of the mid-chord point—is known to have excellent anti-flutter and supersonic control characteristics. The tailpiane is a "flat plate" with leading- and trailing-edge wedgesand of constant chord and thickness. As in most supersonic nns of this shape, the wedges are inversely tapered, i.e., the angle is flatterat the ioot tnan tne tip. Maximum tnickness is about an inch. The forebody, over half the length of the vehicle, is truly cylindricalbehind the sharply pointed ogivai nose. The afterbody is a fructum, tapering at the tail to half its base diameter. The mounting necks of the Thors vary in detail between the missileshown, photographs and the Bobbin RJTV displayed at Paris. In the round snown at Futon the forward part was a box structure, the rearsimply a vertical plate on the centreline. At the forward end was a projecting cylindrical ram-air scoop. It may be recalled that twoitems shown by Bristol at last year's S.B.A.C. Display were a ram-air hydraulic p-unp and a ram-air fuel turbo-pump. It is natural to compare the Bloodhound aircraft with the otherknown ramjet SAM, the Boeing IM-99 Bomarc—particularly in view of the technical agreement between the companies. It would appear thatBristol obtained (mainly) ramjet operating know-how from America, but this saved something like two years in development time. Itis noticeable, too, that both missiles have the distinctive cut-back wing-tips. There, however, all resemblance ends, for the Bomarc hasa near-delta high wing with all-moving tips, a tin and rudder, under- slung ramjets and integral booster rocket. Power Units. The Thor ramjet is fairly well known. It is, how-ever, worth pointing out that the centrebodies in the accompanying photographs are "security dummies" : they would indicate a speed ofMach 4—if they did not choke the intake! Fabricated, mainly by welding, from 18-8 commercial stainless steel, the Thors are quiteroughly finished externally, except for the intake lips, which are pre- cisely finish-ground. The arguments for the ramjet as a supersonic powerplant are fairlyfamiliar, but a few points made by Mr. Nedham are significant. Kero- sine was chosen for tne Thor to give safe handling, but wide-cut orOther hydrocarbon fuel would work as well. A fully automatic, pres- sure- and temperature-compensated stoichiomctric mixture control withan override gives, it is claimed, easier thrust control than can be obtained with a rocket The rocket take-off boost and the ramjet make"a happy combination," since it can be accelerated well into the economical operating regime. The most efficient speed zone is aboutMach 2.5, in which a practical pressure ratio is about 15 to 1. The ramjet's fuel consumption is about one-sixth of the propellant consump-tion for a rocket missile of equal capability. A curve shown suggested that below a 20-mile range the rocket gives the lighter vehicle. Structure. As far as external examination can show, the Blood-hound is a fine piece of expendable engineering. The body appears to be of thick-skinned anodized light-alloy con-struction, with some riveting but with the sections assembled by close-pitched mushroom-headed screws. Bristol's known use ofRedux-bonding suggests that this might be used for internal stiffening —of which there is little rivet-line evidence. The glass-fibre ogivainose-cap—which must have posed immense structural and electronic problems—is attached to a welded cylindrical metal action, and thereare fourteen external strakes where the latter (oins the forebody. These strakes are closely set above and below but absent at the sides(i.e., the structure has maximum reinforcement in the line of the pitch- ing moment) and obviously hold quick-release fasteners. The wing is fabricated; knowing that Bristol have worked extensivelywith Durestos, one might hazard a guess that it is filled with that material. That it certainly has an internal structure is revealed bynine spanwise and five chordwise rows of rivets. The wing-tip of the Filton model appeared to be filled with multi-ply. Structure of thetailplane, and of the booster fins, is similar, the latter showing clear evidence of spot welding of skin to structure. The tailplane halves areattached by a spigot spar fitting to a sturdy mounting ring let into the main body. Launching Equipment. Arrangement of the quadruple concentricboosters is simple. Each ten-foot case is fitted with a massive machined thrust-ring at its base and a ring-bracket with a W-shapedfoot at its conical nose. The thrust-ring has pinned to it the fin and is itself attached by two pins to two forks on a central mounting ring, whichfits round the tail bulkhead of the missile body. The front bracket has two curved lugs that slide under fore-and-aft lugs on the body. The slope of the afterbody of the missile means that the boosters havean outward cant of 3 deg, but to aid separation there are two tiny trim vanes (about two inches square) attached to the front ring-bracket ofeach booster. The action (confirmed by a film) is that, at burn-out, the cessation of thrust causes the booster assembly to slide back acouple of inches, when the nose brackets are released and the cases hinge outward (like an umbrella), to form a cross and be whipped awayby their high drag. This umbrella action is the reason for the cut-away trailing-edge roots of the rectangular booster fins, which are necessaryfor clearance. Rapid assembly is an important factor in a missile, and this boosterassembly is put together with one-inch-diameter headed pins, locked in place by "hairpins" on the castings which slip into annular groovesin the pin-heads. The launching angle of 45 deg is fixed, but the turntable is hydraulic-ally operated and closely resembles that for a gun. There is no aircraft practice here; it is sturdy, weatherproof shipyard stuff, although it isworth noting that the support frame is made from box girders formed by welding two steel channels face-to-face-^-a fairly common aircraftjig practice. The lower end of the supporting cradle has a hydraulic raising and lowering ram, while the truss supporting the upper end hastriple hinge-knuckles, which are manually locked by removable pins. Armoured leads to a screw "breech unit" at the base of thelauncher connect to the self-sealing couplings in the tail of the missile. There are high- and low-pressure hydraulic supplies, plus a gyro air-supply—the gyros coast after launching. A multiple electric connector— about 6in x 3in—under the tail is palpably that for all services. Thisconnector is surrounded by a rubber shield on the principle that the Bloodhound is an all-weather weapon which may stand at the ready fordays on end. Bristol Aircraft, who have been given M.o.S. permission to offerthe Bloodhound system to Commonwealth and NATO air forces, refer to it as an un-manned VTO fighter requiring no aerodrome. Thelauncher is not much more than six feet in diameter and obviously lends itself to mounting in dispersed, easily camouflaged bases. Onephotograph shows how small the trailer is in relation to a Land-Rover —perspective distortion in this picture over-emphasizes the size of thebooster fins. J.H.S. Dimensional Data: Span, 9ft 3in; length, 22ft 2in; body diameter,lft 9in; ramjet diameter, lft 3.75in; ramjet length, 8ft 4in; tail span, 4ft 8in; tail aspect ratio, 1-6; wing area (approx) 24.4 sq ft; wingaspect ratio 3-5. An indication of the mobility and relatively light weight of Bloodhound is afforded by this picture of the weapon being towed by a Land-Rover.
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