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Aviation History
1949
1949 - 0205.PDF
The first aircraft to fly solely on ramjet power—a Lockheed F-60. RAMJETS Some Experimental Applications : America Goes Ahead F|EW devices have borne such a diversity of names asthe aircraft heat engine now generally called " ram-jet," but otherwise known as "athodyd" (aero-thermo dynamic duct); "propulsive duct"; "compressor- It, ^s thermal jet"; " Lorin duct" or " Lorin nozzle ''; "continuous thermal duct" ; or "aeroduct." The ramjet can be characterized as a continuous-firing duct, burning fuel with air compressed by the effect of ram, and expanding the products of combustion rearwards to produce thrust. Though capable of operation at sub- sonic speeds, it is relatively inefficient under these condi- tions, and, having no static thrust, must be accelerated to its initial operating speed by some independent means of propulsion, e.g., booster rocket. Being dependent upon an external source of oxygen, its output, like that of the turbojet, tends to decrease with height. A near-relation of the pure ramjet is the '' pulsejet'' (alias "pulsating," or "stuttering," athodyd; "resonance jet"; "intermittent-firing duct"; or "Argus tube"). In this unit, which is typified by the power plant of the German Fi 103 (" V-i ") flying bomb used in 1044 and 1945, the tubular body is fitted, at its forward end with a series of flat spring-loaded admission valves and fuel- injection nozzles. Air pressure on the nose forces the valves Northrop Black Widow with underslung ramjet of rectangular section. open, and the air is rammed into the duct, where it mixes with the fuel for combustion, and rapid expansion is pro- moted. By careful proportioning of the tailpipe, a rise in pressure is utilized to close the valves. Violent ejection of the gases creates a depression which, in conjunction with external air pressure, opens the valves to admit a fresh charge of air; thereupon the cycle is repeated. The unit fitted to the V-i operates at a frequency of about 2,800 cycles a minute, and the missile attained a speed of about 375 m.p.h. The aero-thermo-dynamic propulsive principle, that is a thermal duct without valves, was proposed as long ago as 1913 by a Frenchman, M. Lorin, but for many years air- craft speeds were so low that no practical work could be undertaken. At the Paris Salon d'Aviation in 1938, how- ever, a ramjet monoplane by another French engineer, Ren6 Leduc, was exhibited in model form, with a placard suggesting that a speed of 1,000 k.p.h. should be attained with an output of 14,000 h.p. On November 16th, 1946, a ramjet aircraft built along similar lines by Breguet, and designated Leduc 010, was first air-launched from a super- structure built on the fuselage of an Aerosudest Languedoc four-engined airliner. A successful glide descent was made from some 16,500ft, but since this occasion little informa- tion on progress has been forthcoming. In effect, the Leduc 010 has an inner and an outer fuselage shell, the inner housing a pilot and observer, and being surrounded by an annular duct which forms the ramjet. The pointed nose section is jettisonable in emergency, and the main airframe structure is provided with four parachutes for recovery. Since the war America has carried on experiments with improved ramjets. The U.S. Navy experi- mented with a 70-lb ramjet missile of 6-inch dia- meter; known as the Cobra, this was part of " Project Bumblebee," and a specimen was rocket- launched from a ramp at Island Beach, New Jersey, as t-arlv as June, 1945. Well over a year ago it
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