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Aviation History
1956
1956 - 0790.PDF
792 FLIGHT, 15 June 1956 STUDENT'S PROGRESS (continued from page 772) And so, along these three main streams of individual and groupstudy, the second-year work progresses. The sight of an Anson with a swept wing mounted atop thefuselage is the sort of thing one comes to accept without surprise at Cranfield, as is that of a Lancaster similarly dressed. Theformer, one learns, is involved in a student's thesis investigation of the effect of sweep and Reynolds number on transition, whilethe latter is being flown under an M.o.S. research contract investi- gating the effect of Reynolds number and incidence on transition.Another unusual type soon to appear at the College for research flying is the aero-isoclinic Short Sherpa. While the second-year students, whom we left one paragraphago, continue their work, we may visit the main departments to look briefly at some of their facilities and equipment. Cranfieldis exceptionally well equipped for its task, as those who visited the College on its recent Open Day will agree. The Aerodynamics Department has a wide range of wind tunnels,from the recently completed 8ft x 6ft low-speed tunnel to con- tinuous and intermittent supersonic tunnels capable of Mach 2.5and 3.0 respectively, in addition to several low-speed demonstra- tion tunnels. Most spectacular of the Design Department's facilitiesis the demonstration laboratory, containing specimens of aircraft components, systems—and complete aircraft, including the SaroS.R.A./l flying-boat fighter and the Messerschmitt Mel63. The structural laboratory houses a large selection of testing machines,with undercarriage drop-test rig (having a rotating flywheel for drag and side-load effects) and water tank for pressure-testing;while representative pneumatic, hydraulic, air-conditioning and de-icing systems are exhibited in the installation laboratory. In the Propulsion Department's test-house area are located testbeds for piston engines, turbojet and turboprop units, and rocket motors, in addition to various smaller rigs. A compressor plantis used to supply air for investigations into combustion problems, gas flow and heat transfer in ramjets. Other laboratories aredevoted to fuels, hydraulics, other rig tests, and a demonstration section covering all types of powerplants. In many respects a pioneering organization in this country, theDepartment of Economics and Production possesses facilities which are the equal of any in Britain. The equipment includesan industrial laboratory (with machinability and forming sec- tions), standards and metrology room, work-study laboratoryand business-systems laboratory. The Department's facilities are now used by the Work Study School as well as by students of theCollege of Aeronautics. In the youngest full Department, that of Electrical Engineering, there are laboratories containing speciallydesigned instructional equipment and concerned with circuits, machines, high-frequency work, and electronics. The students'research laboratory has a general-purpose analogue computer. Towards the end of the second year, the utilization of thesefacilities is increased—and the lights in students' rooms in Lan- chester remain on until 3 and 4 a.m. again—as the tempo of workincreases. During the Easter term, however, a pleasant interlude is provided when firms' and Ministries' representatives visit theCollege and dangle various incentives in front of the prospective employees. For the students, it is good to feel wanted again. Itis also pleasant to envisage a reasonable future income, most non- Service students having existed at a marginal level on variouslocal, State, Ministry and independent awards and scholarships during their two years at the College. In spite of the pressure of work, time is somehow found for theorganization of the students' annual Presentation Ball, an ambitious celebration which, coming as a grand finale to the course, is heldon the evening of Presentation Day. Before that, however, there are theses to be completed, handedin, and given professorial consideration. Typical recent subjects, quoted at random, have been: Flutter of wings of low aspect-ratio; possibilities of the high-speed tail-first aircraft; power controls; theoretical analysis of the buckling of circular cylindricaltubes in bending; application of memo-motion to industrial opera- tion; manufacture of unsymmetrical integral structures; inert-gasgeneration for purging fuel-tanks; compressor-blade vibration; a synthetic trainer for hyperbolic navigation; and methods ofbinary/decimal data conversion, using saturable reactors. The process of handing-in theses, on a specified date at thebeginning of June, can be an informal or a ceremonial occasion, depending on the nature of the second year concerned. Deliveryof theses has been variously made in dustbins on to the desks of departmental heads, in a coffin carried in a hearse-like vehicle,and individually through the windows of the Board room. But, whatever the gimmick, they get delivered—and the tennis courtsthen become fully booked until the end of term. Too soon, it seems, the course results are announced and, soonafter, it is Presentation Day. This is an Important Occasion which brings Important People from the Ministries and theindustry to the College. If you are one of the men receiving the College diploma on this occasion, a lot of words about trainingfor technology will be spoken at you, very few of which you will remember. What you will remember, however, after joining or rejoiningfirm, Ministry, squadron, research establishment or university, here or abroad, is something more worthwhile. It is the recollec-tion of two memorable, if at times exasperating, years; of a vigorous atmosphere which stimulates the receptive mind but which canoverpower the short-sighted; and of an Aviation College which is still in the early stages of forming its own unique tradition. Youare privileged to have been there. WESTCOTT SHOWS ITS WARES (continued from page 763) One of the largest A.T.O. motors is the Mayfly, which has a lengthof no less than 180in, and is widely employed in groups of four or more. For advanced g.w. trials the Mayfly has a standard rating of 15,000 lbfor 3.5 sec and accommodates 260 lb of cordite filling. Last week Flight's representative at Westcott watched a Mayfly firing in which theduration had been reduced to 2.7 sec, raising the thrust to 18,000 lb. Everything appeared to go excellently and subsequent examination ofthe test records showed what seemed to be well-nigh-perfect combus- tion, about 95 per cent of maximum thrust being reached within 1/50 secof the firing of the igniter and both the thrust and interior-pressure staying almost exactly constant until burn-out. The cases of suchmotors are re-usabk. R.T.V.-l.—Already well-known as the first standardized design oftest vehicle (and many times illustrated in our pages) this was shown as a cut-away display model, together with a small model of the originalform of the project (which was markedly different). The design was ascribed to the R.A.E./R.P.D. and the manufacture to Marston Excelsiorand Armstrong Whitworth Aircraft. The single sustainer chamber operated on liquid oxygen and alcohol/water and was rated at 1,075 lbfor 21 sec with a specific thrust of 188 Ib/sec/lb. The propellants were fed at 6.2 Ib/sec from tanks pressurized to 480 lb/sq in by gas from asolid charge; ooerating-chamber pressure was given as 325 lb/sq in and the total filled weight of the vehicle as 260 lb. N.K.I.—Very little has previously been revealed about this liquid-propellant motor, which seems to be the standard British unit for the development of chambers, feed systems and engineering details. Adisplay model showed an N.K.I mounted in a test vehicle for free-flight trials. The thrust is 3,500 lb and in this case burn-out was limited bythe vehicle design to 19 sec. Propellants are 98-per-cent red fuming nitric acid and kerosine inthe ratio of 4.25 : 1 by weight. These are contained in tanks of DTD.245 aluminium-silicon alloy, the centre section and diaphragmspace being sand cast and part-machined and the barrels being con- tinuously cast and fully machined. The tanks form an integral part ofthe structure of the vehicle, which has an empty weight, less motor, of 392 lb. The tank bore is 14.5in and the minimum wall thickness0.3in, the design tank pressure being 550 Ib/sq in gauge and the test pressure 900 lb/sq in. This pressure is generated by three 3.7in- diameter cordite charges inhibited by .O75in cellulose acetate—what isknown as a "cool cordite" charge. The motor itself was made of S.21 mild steel and had a specific impulse of 193 sec and a characteristiclength (chamber volume divided by throat area) of 5 Sin. The burner pressure was set at 430 lb/sq in and the chamber pressure at 280lb/sq in; the nozzles were of the 2 : 1 oxidant/fuel impingement type with fuel-film cooling in the chambers. With the associated valves andpipes the chamber weighed 50 1b. Experimental Chambers.—Also on display were numerous chambersdesigned for the N.K.I liquid-propellant motor described above. Some had refractory liners but the majority were all metal with regenerativecooling provided by the nitric acid. One chamber incorporated an 8in burner with like-on-like impingement nozzles, and was fabricated from14 Hydroformed segments welded together. Another chamber was manufactured from 14 equal pieces of mild-steel tube of ljin O.D.and 16 s.w.g., each piece being pleated and pressed to form a regenera- tively cooled segment, the portions being finally welded in a jig; thecharacteristic length of this chamber was 55in, the weight 23 lb and the operating pressure 310 lb/sq in gauge, coolant acid velocity at thethroat being 32i ft/sec. Yet another fabricated chamber was made of stainless steel (F.D.P. or Immaculate 5), the outer shell being of 14 or16 s.w.g. and the inner liner of 20 s.w.g., with axial corrugations spot- welded to provide multiple cooling passages; the operating pressure wasgiven as 280 lb/sq in gauge, the characteristic length 65in, the weight 24 1b and the throat coolant velocity 35 ft/sec. Miscellaneous.—The following were some of the new developmentson view: porous bronze sections used in conjunction with a hydrogen/ oxygen test rig to investigate this method of chamber cooling in subsonicand supersonic flows; an assortment of refractory nozzles, of which two of the best appeared to be a zirconium boride specimen and an exampleof a carbon nozzle coated with silicon carbide; a demonstration rig (in which vapour from a solution of a potassium salt was admitted to theair holes of a Bunsen burner) showing the effect of ionization in a flame upon the reception of microwaves—as are used to control certain typesof missile; protective clothing and equipment for handling corrosive fluids; a design of turbo-pump in which the bearings were sealed bycentrifugally restraining the fluid away from the shaft (a principle long used in rotary pumps for gases); and new forms of instrumentation.
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