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Aviation History
1942
1942 - 0610.PDF
2fi0 F LI G H I MARCH 19TH, 1942 Correspondence The Editor does not hold himself responsible for the views expressed by correspondents. The names and addresses of the writers. not necessarily Jor. publication, must in a t cases accompany letters. ~\ NO NATIONAL MONOPOLY Exaggerated Claims are Bad Policy T HE recent letter in Flight on the subject of American pub licity for their DomOers and fighters is a very timely one. There must be many people here who, owing to their lack of knowleige of aeronautical affairs, believe this high-pressure American publicity., The worst offenders are the daily newspapers, which often print aeronautical " newb " of the moat inaccurate and ridicu lous kind without, apparently, submitting it to their aero nautical correspondent for his comments before publication. (Even Flight sometimes passes exaggerated claims for American aircraft without comment; see my letter in the issue of J une 5II1, 1941.) Lord Beaverbrook's broadcast, at the end of 1940, in which he declared that the Curtiss P.40 was equiva lent in performance and speed to the Spitfire (figures released later on showed that the Tomahawk was not nearly as fast as the Spitfire) is another example of the kind of statement which does no good to anyone and is unfair to the British industry. The Flying Fortress f is the classic example of American propaganda run wild. This aircraft, with no power-operated turrets, is far less of a flying fortress than our old Wellingtons and Whitleys; yet it received the most exaggerated praise from the Press. Gross over-praising of American aircraft, or ours for that matter, does no good to us or the United States, and it lays us open to the jeering derision of our enemies who soon find out the true worth of the aircraft (jpposed to them. The R.A.F. need and deserve the very best machines we can give them; and to expect them to fly aircraft which are inferior to our own is not only unfair to them but is bad policy. But we shall not get better operational aircraft from the United States by extravagant praise of those already delivered. The Anglo-American war effort is a matter of life and death, not a mutual admiration society The fact that our greater experience of air warfare enables us to offer more constructive criticism of American aircraft than they can give to ours should not deter us from asking for machines more worthy of the men who have to fly them. E. N. B. BENTLEY, A'.F.R.Ae.S. LUNAR SPACE VESSEL Vertical Escape from the Earth AS might be expected, there is not complete agreement among the members of, the British Interplanetary Society, but I shall content myself with differing from Mr. R. A. Smith's recent article in Flight on one point only—the vertical escape from the earth. 1 favour a more gentle acceleration around the earth's circumference, in the stratosphere, in which case the take-off becomes a simpler matter with the aid of fins, which can also start the axial rotation during the initial flight, and may be jettisoned. Some time befoie the war the B.I.S. had an arrangement with its American and German counterparts whereby all three journals were sent out to the members of each. To the best of my knowledge there are now four such societies in England, but one doubts if the German one survived the "purges" ! They are as follows :— British Interplanetary Society ("The Journal ot ") (dispersed on National Service). Manchester Interplanetary Society ("The Astronaut"), 41, Longford Place, Victoria Park, Manchester, 14. Manchester Astronautical Association, 683, Ashton New Road, Manchester, 11. Astronautical Development Society (see Correspondence in Flight, October 30th, 1941). American Rocke* Society ("The Journal of "), 3t, West 86th Street, New York City.. E. V. Fortschrittliche Verkehrstechnik ("Das Neue Fahrzeug"), Berlin, S.W.29, Bergrfiannstrasse 51. It would be a good thing if Flight were instrumental in bringing about more co-operation. Finally, I should like to draw attention to the following note which appeared after a letter printed in Flight July 25th, 1935 •— [A member of the staff of Flight has watched a demonstra tion of Mr. Verschoyle's apparatus. He reports that there is no doubt whatever that the "levitors"—which are small paper cylinders containing simple electrical apparatus—do rise in the air when the potential is applied to them by the thin wire, which they actually tend to lift also. The experiments appear to be convincing, though probably of more interest to the electrical engineer than to the aeronautical engineer at the present stage of progress.—ED.] I think I can say on behalf of all interested in Space Travel that the hospitality accorded by Flight is exceedingly appre ciated. R. C ABEL. JET PROPULSION OF AIRCRAFT Pressure Variation "See-Saw" ]\<r \Y I draw your attention to what I consider to be a funda- lVx mental objection to any scheme of jet propulsion of aircraft, in which the object is to increase the momentum of a jet of air by introducing heat energy into it, by fuel jets or burners? When air is flowing through any system or arrangements of pipes, nozzles or jets, there will generally be, by Bernouilli's theorem, a variation of pressure along the line of flow. The air will lose momentum, as it flows against the pressure and gain an equal amount as it flows with it. No DISCHARGE.. matter how complicated the system of pipes, etc., there can be no resultant gain in momentum. Suppose now that heat is added at B in the accompanying diagram. This will produce an increase in the temperature and the pressure, both increases being due to an increase in the random molecular energy of the air. There will be no • change in the general momentum. The change in pressure due to the addition of heat will modify the pressure distribu tion, inside the jet propulsion apparatus, as shown. In travelling down the pressure gradient from B to C the air will undoubtedly gain momentum, but, on the other hand, it will lose an equal amount in travelling up the gradient from A to B. The whole idea appears to me to be analogous to an attempt to propel a vehicle by placing hills in its path in the hope that the momentum gained coming down the hill will more than offset the momentum lost in climbing it. The only air jets I can imagine functioning satisfactorily are those fed by an airscrew or air compressor, in which cases the air is "lifted" up the pressure gradient by the airscrew blade or the compressor piston. It might be asked, "How, then, can a steam turbine function? " The answer lies in the fact that the medium used is forced into the boiler (up the pres sure gradient) in a concentrated form (i.e., liquid) agA used as a propellant in a highly expanded or gaseous conditio^ If there is an error in my reasoning or any points that I have overlooked I would appreciate enlightenment. R. M. HELSDON, B.Sc. [If the conclusions of our correspondent mean that, in his view, propulsion by jet reaction is not feasible, the actual flight of the Caproni Campini aircraft is sufficient answer.— ED.]
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