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Aviation History
1954
1954 - 0202.PDF
n FLIGHT PRESERVING HISTORIC AIRCRAFT . . . both the association and the types of aircraft concerned, it would bring in small but acceptable revenue. Yet another method of raising money could be an annual garden party with flying display, and/or an annual dinner and dance in London. I have already said that members would not receive much direct material benefit for their money; and that is why a low annual subscription would be necessary. The only benefits possible, as I see it, are: (1) The satisfaction of knowing that their money is helping to keep some fine old aircraft in existence; (2) reduced admission charges to flying displays at which asso ciation aircraft were appearing; (3) the right to inspect the collec tion free of charge and without unreasonable hindrance (4) admission to the garden party or other events organized by the association. Summing-up. In making the foregoing suggestions I have had in mind military aircraft of more recent vintage, because other classes are already catered for; the very early types are looked after by the Shuttleworth Trust and the Nash Collection; THE possible effect of cosmic rays on the human body is important, not only to would-be astronauts, but also to those interested in flight at extreme altitudes. In a paper delivered to the British Interplanetary Society on January 2nd —The Possibility of Cosmic-Ray Hazards in High-altitude Space Flight—Dr. L. R. Shepherd, the Society's chairman, reviewed our present knowledge of cosmic rays and the possibility of danger from them. Some 40 years ago V. F. Hess put forward the hypothesis that the increase in ionization with altitude was the result of radiation from outer space. From this simple beginning, said the lecturer, the study of cosmic rays had expanded until it was now one of the most important branches of physics. By taking up ionization chambers beneath balloons it was found that the intensity reached a maximum at a height of 20 4o 30 km and then fell off gradually at greater heights. Subsequently, rocket measure ments up to 160 km had shown that the ionization did not show any further increase. The mean intensity of ionization produced at sea-level was about 2 ion pairs/cm3/sec; at high altitude, at a latitude of 60 deg N, the value rose to 360 ion pairs/cm3/sec—an increase of nearly two-hundredfold. The Earth's magnetic field also had an influence on the intensity, since it deflected particles of under a certain minimum energy level. Thus at latitude 3 deg N the peak intensity was only about 100'ion pairs/cm3/sec. How ever, there was no increase in intensity with increase in latitude past 58 deg, which meant that no particles below an energy of 560 x 10s electron volts were present in space in the vicinity of Earth. One possible explanation of this phenomenon was that the Sun possessed a magnetic field which deflected all particles below this energy. It had been found that the majority of cosmic-ray particles were positively charged, and for a long time it was assumed that they were all protons—that is, hydrogen nuclei. In 1948 it was shown that some of the particles were in fact nuclei of heavier elements ranging from helium to iron. All of this radiation produced ionization in any material it traversed, and if the material was living tissue it would be damaged. The standard radiation dosage was the Rontgen or y-unit and was the amount of irradiation that would produce 2.1 x 10' ion pairs in a cubic centimetre of air at 0 deg C and 760 mm pressure. In this country the upper limit, or tolerance as it was known, PRODUCTIVITY was the main theme of a recent lecture before the Brough Branch of the Royal Aeronautical Society. The lecturer was Professor J. V. Connolly, Head of the Depart ment of Aircraft Economics and Production at the College of Aeronautics, Cranfield, and his views caused very considerable interest, subsequently bringing a great many questions. He said that in recent years sixty teams, each comprising twenty or so experts, had been to the United States to study various industries, and that their findings gave America, on average, a productivity rate of twice the British figure. The American worker, as a result of his high productivity per man-hour, earned on a comparative basis two-and-a-half to three times the wage of his British counterpart. Germany was also stepping up her productivity—as this country would learn to her cost in the next eighteen months or two years; there is a Vintage Aeroplane Club for, I believe, civilian types of the 1920s and early 1930s, and overlapping the whole lot is the National Aeronautical collection of the South Kensington Science Museum. To sum up, then, if we are to preserve our historic military air craft, it seems that the only solution is for the public to form an association and look after the veteran aircraft themselves. Some suggested details have been outlined. What form should the initial steps take? If these ideas appear workable, as shown by the reactions and constructive criticisms of readers of this article, then further steps must be taken to gauge the probable amount of public support. We shall then know whether or not the Air Ministry can be approached. The importance of adequate support from people interested in the idea cannot be too highly stressed. If an annual subscription of five shillings was decided upon, the association would need 4,000 members to bring in £1,000 per annum—a not very considerable sum for the job involved. Time is very short. Already the last Wellingtons are await ing the melting pot, and who knows what other fine old aircraft are in a similar predicament? was 0.5y per working week; no worker who was regularly exposed to gamma or X-radiation must repeatedly exceed this dosage. At the maximum measured rate of 360 ion pairs /cm" /sec it would require nearly five weeks to accumulate the allowable weekly dose of 0.5y and at first sight there would appear to be no danger to the human organism from cosmic radiation. However, this quoted tolerance of 0.5 applied to gamma and X-radiation only and could not, for example, be applied to neutrons or alpha-particles. In fact, for the same total dosage much more damage could be caused by a particle that produced a high ionization density along its path than one that produced a low density. Dr. Shepherd said that it was more or less certain that the lethal effect of ionizing radiation arose as a result of chemical actions. Excessive radiation could destroy cells almost immediately but the normal effect was to produce changes in the cells which led to their death when they attempted division. Most experimental work had been carried out on plant tissues and it had been found that the lethal effect appeared to be due to structural changes in the chromosomes. This lethal effect depended on the ionization density, i.e., on the number of ion pairs produced per unit length of the track of the ionizing particle. Below 100 ion pairs per micron the relative biological effectiveness was found to be con stant, rising rapidly between 100 and 1,000 and remaining constant thereafter. There were two main hypotheses for the actual mechanism of lethality. One was that the ionizing particle passed through or close to the chromosome, thus effecting direct chemical changes in it. The other was that the ionization produced hydrogen peroxide in the water of the tissue, thereby destroying the enzymes in the cells. Either of these hypotheses could be shown to account for the rapid rise in relative biological effectiveness with ionization densities between 100 and 1,000. It could be shown that the heavy primaries, and some of the secondary particles produced when the primaries entered the atmosphere, were the most dangerous biologically. The radiation hazard for flight in or just above the atmosphere was not thought to be great even for prolonged exposures. At great distances from the Earth conditions might be worse, and for long exposure- periods some form of shielding might have to be devised. These conclusions were, however, tentative and much more work both in the laboratory and in the upper atmosphere was needed. and Japan would provide some fierce competition in certain fields. In Britain any wage increase must be allied to greater produc tivity; the leaders of the engineering unions appreciated the impor tance of these economic factors. The stop-watch and not the rate- fixer was the standard of work-study in America, and Britain also must employ experts within her industries to raise the pro ductivity rate. To compete in world markets the productivity of all our industries must increase; this was a task and a chal lenge to both worker and management. Increase in machine-tool speeds was one of the matters men tioned by the lecturer; he remarked that high-pressure lubricants had, in some instances, enabled cutting speeds to be raised one hundred times. In the field of aviation Professor Connolly referred to the decrease in man-hours with quantity; typical figures were: one off, 16 man-hours per lb; 100 off, 7; 200 off, 4. COSMIC RAYS AND THEIR DANGERS —discussed in Interplanetary Society's Lecture PROBLEMS OF PRODUCTIVITY
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