AERONAUTICS 101 are carefully guarded. After many years of experiment Dr Wolfert When the resistances have been reduced to the lowest budt and experimented with in Berlin, in 1897, a cigar-shaped balloon driven by a gasoline motor. An explosion took place in possible minimum by careful design, the attainable speed the air, the balloon fell, and Dr Wolfert and his assistant were will depend upon .the efficiency of • the propeller and the killed. It was also in 1897 that an aluminium balloon was built relative lightness of the motor. It seems not unlikely that from the designs of D. Schwarz (then deceased) and tested in Berlin. It was driven by a Daimler benzine motor, and attained a 30 miles per hour can be attained in the near future; but greater speed than “ La France” ; but a driving belt slipped off its the commercial uses will be small, as the balloons must pulley, and in coming down the balloon, was injured beyond repair. remain housed when the wind aloft is brisk. The sizes From 189/ to 1900 Count Zeppelin, of the German army, was will be great and costly, the loads small, and the craft frail •engaged in constructing an immense balloon, truly an air ship, of and short-lived, yet dirigible balloons constitute the proper most careful and most intelligent design, to carry five men. It was first tested in June 1900, when it attained a speed of 18 miles an type for Governments to evolve, until they are superseded hour and travelled a distance of 3J miles before an accident to the by efficient flying machines. steering gear necessitated the discontinuance of the experiment. While the flying machine is still inferior to the balloon In 1901 M. Santos Dumont carried out some more or less success- in performance and safety, it has made more progress since ful experiments with a dirigible balloon in Paris. 1888 than during the preceding three centuries. The principles which govern the design of the dirigible Investigation has turned from flapping wings and balloon may be said to have been evolved. As the lifting from sustaining screws to the aeroplane type, and power grows as the cube of the dimensions, and the encouraging results have been obtained not only with resistance approximately as the square, the advantage lies models but with full-sized machines. The flights have been with the larger sizes of balloons, as of ocean steamers, up very short and hazardous, but the speeds have been much to the limits within which they may be found practicable. greater than with balloons. The danger involved in the Count Zeppelin may have reached the limit as to practicable proximity of fire to gas being absent, Maxim, Langley, size. He has gained an advantage by attaching his pro- Ader, and others have produced steam motors weighing pellers to the balloon, instead of to the car as heretofore; 10 lb or less per horse-power. This, it is true, is exclusive but this requires a rigid framework and a great increase of of fuel and water, and the engines work nearly to the limits weight. Le Compagnon endeavoured, in 1892, to substi- of endurance; but the automobile industry is developing tute flapping wings for rotary propellers, as the former can gasoline motors which are nearly as light, and these may be suspended nearer the centre of resistance. Danilewsky prove better adapted to aerial propulsion. Knowledge has followed him in 1898 and 1899, but thus far without been greatly increased as to the laws of flight. Professor remarkable results. Dupuy de Lome was the first to Marey has furnished new data concerning bird locomotion, estimate in detail the resistances to balloon propulsion, and Professor Langley has elucidated the problem of air but experiment showed that in the aggregate they were reactions on oblique planes. Physicists still computed, greater than he calculated. Renard and Krebs also found down to 1891, the normal pressures upon oblique planes that their computed resistances were largely exceeded, as varying in the ratio of the square of the sine of the and after revising the results they gave the formula angle of incidence or, at best, in the ratio of the sine of R — 0’01685 D2Y2, R being the resistance in kilograms, that angle. Langley showed, by extensive experiments, H the diameter in metres, and V the velocity in metres that this normal had nearly twice the assigned value, and per second. Reduced to British measures, in pounds, feet, that Duchemin’s empirical formula and miles per hour, R = 0‘0006876 D2V2, which is somewhat N = P 2sina2 in excess of the formula computed by Dr Pole from De 1 + sin a Lome’s experiments. The above coefticient applies only which was proposed about 1838 but not adopted, was to the shape and rigging of the balloon “ La France,” and correct for oblique planes. More than this, combines all resistances into one equivalent, which is equal approximately Lilienthal showed, about the same time, that concave birdto that of a flat plane 18 per cent, of the “master section.” like surfaces afforded from three to seven times as much This coefficient may perhaps hereafter be reduced by onesupport as planes at acute angles of incidence, and gave half through a better form of hull and car, more like a fish also a small propelling component, so that former views and than a spindle, by diminished sections of suspension lines modes of calculating the surfaces and power required for and net, and by placing the propeller at the centre of resistance. To compute the results to be expected from Principal Experiments with Flying Machines. new projects, it will be }(referable to estimate the resistances in detail. The following table shows how this was done by De Lome, and the probable corrections which Inventor. Motor. should have been made by him:— Resistances—De Lome's Balloon. Computed by De L6me. V=2'22 m. per sec.
More Probable Values. V=2-82 m. per sec.
Part.
Hull, with- 172-96 1/30 0-665 out net. Car 3‘25 1/5 Men’s bodies 3-00 1/5 Gas tubes . 6‘40 1/5 Small cords 10-00 1/2 Large cords 9-90 1/3
3-830 1/15 0-875 10-091 0-432 0-400 0-850 3-325 2-194 11-031
1/5 1/2 1/2 1/2 1/3
0-569 124-375 2-887 21 -984
W 1879; Tatin.
Ft. Sq. ft. 6-2 7-5
1885, Hargrave 5-5 26-0 1889j / (No. 16) ! 18931 Phillips . i 22-0 136-0 18941 Maxim* j 50'0 4000-0 1896 Langley . | 12-0 70-0 18971 Tatin and ! 21-0 86-0 Richet 1897! Ader* I 49-0 270-0 1895! Lilienthal* j 23-0 151-0 1896[ Pilcher* 1 . 23-0 ! 170-0 1890j Chanute* I 16-0 ! 135-0
lb. .Mis. Ft. 3-85 0-51 i 18 100? Compressed 5-00 0-19 j 10 343 402-00 I 3-00 ! 28 500? Steam 8000-00 2-00 i 36 300?! „ 30-00 0-43 J 24 4000 „ 72-00 0-83 40 460 i „ 1100-00 4-00 : 50? 100?; „ 220-00 1-46 i 23 1200 Gravity 200-00 1-17 : 25 900 178-00 1-31 i 22 360
3 Pho 5P.
0-03 110?
0-06 79 5-6 ! 72? 363-00 28 1-00 30 140-00 27 22-00 100 2-00 89 3 flight have been quite revolutionized. Experiments have 7 therefore been more intelligent and more successful than 1 The pounds sustained per horse-power in the last three experiments will probably be reduced one-half when an artificial motor is substituted for gravity.
