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Aviation History
1956
1956 - 0557.PDF
FLIGHT, 11 May 1956 55? The Supersonic TOMORROW'S PROBLEMS—AND SOME SOLUTIONS TWELVE years have now passed since the aircraft gas turbinefirst reached the operational stage with the British andGerman air forces. During this period the turbojet has completely dominated the whole field of military aircraft propul- sion, and the impact which it has made on aircraft design cannot be exaggerated. Little purpose could be served by attempting to outline the progress made over the past dozen years in the design of military aircraft and engines. Although this is one of the world's greatest stories of technological achievement in pushing back long-estab- lished boundaries of both accomplishment and basic knowledge, it is, from our British viewpoint, clouded by a sorry string of immense opportunities which have been lost. To a high degree this has resulted from our own outlook on problems and, in particular, from our cautious approach to the so-called sound barrier. In the decade between 1944 and 1954, our fastest aircraft progressed from Mach 0.80 to Mach 0.95 while, over the same period, American aeroplanes explored the entire flight spectrum up to Mach 2. Our only supersonic experience was obtained in dives, in which some of our aircraft could get just beyond sonic speed for a few seconds. No responsibility for this poor progress can be laid at the door of our powerplant manufacturers. They have served us well and, if our structural and aerodynamic teams have the ability and courage to match their products to the power which will be made available to them, the next twelve years will see advances even more startling than those of the twelve years just completed. Nevertheless, the vast supersonic realm now open to us is challenging in the extreme. It has often been said that, once Mach 1 is passed, nothing much happens until the so-called heat barrier makes itself noticeable at something over Mach 3. From the propulsion viewpoint this is very far from the truth. Even now, thousands of engineers are engaged in a bitter combat with the thermodynamic, aerodynamic and structural problems occa- sioned by the jump from Mach 1.5 to Mach 1.8 or 2. It is easy to juggle with Mach numbers on paper, but in practice 2.0 can be quite different from 1.90. Turbojets are still the dominant form of powerplant. It is worth recalling that, a dozen years ago, it was widely considered that the turbojet would probably not be able to propel operational military aircraft at speeds much beyond that of sound. Several authorities, in fact, suggested that the ramjet would begin to be pre-eminent in the vicinity of Mach 1.5. Yet events have shown that the conventional turbojet is capable of doing useful service over a much wider spectrum. Already combat-type aircraft are flying close to Mach 2 solely on turbojet power, and present indications are that by 1960 there will be several types of aircraft, wholly or principally powered by turbojets, capable of Mach numbers of up to 2.5 or 2.7. Performance of this order—double that of the fastest aircraft at present in service—requires propulsive power which, by past standards, is stupendous. The efficient provision of such power presents as great a challenge as any ever placed before an aero- engine industry. Yet, on paper at least, it can be done; and, perhaps surprisingly, better with the turbojet than with the ramjet or rocket. In the succeeding pages some of the factors influencing the design of advanced turbojets are examined in the simplest terms. . CONTINUED OVERLEAF
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