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Aviation History
1922
1922 - 0049.PDF
SEMI-RIGID v. RIGID AIRSHIPS' By UMBERTO NOBILE, Director of THERE exist today two types of airships which are contending for supremacy : the semi-rigid Italian type, and the rigid German or Zeppelin type. The former may be divided into two sub-types : one having an articulated longitudinal keel or backbone, the other a rigid one. While for small volumes the superiority of • the articulated keel type is generally recognised—and proved by the numerous requests from foreign Governments for trial airships of this typef—many experts maintain that, even for the larger airships, the Italian semi-rigid type can successfully compete with the rigid or Zeppelin type. Though there may be doubt concerning the articulated type, there can be none whatever as regards the rigid girder type, as shown by the brilliant success experienced with our first model " T " airship, the " Roma "—the general arrangement of which is shown in the accompanying diagrams. We are convinced that to whatever dimensions our "T " type may be increased— within practical limits—we shall always find that the par ticular characteristics which constitute its fundamentally good qualities are not only preserved, but even accentuated. Of course, I do not say that great increase in capacity can be made without giving rise to difficulties. When the volume exceeds 3,500,000 cubic ft., the problems of construction and assemblage take on a certain importance, but though these problems may be difficult of solution, they are never such as to lead to unfavourable conditions. We consider that the essential reason why our type is superior to the rigid Zeppelin lies in the conception of the rigidity itself. In the latter type, the whole of the external surface is made rigid, even where the natural pressure of the gas is sufficient to preserve the shape. In the Italian semi-rigid, only those parts are made rigid which really require it, thus greatly simplifying construction and assem bling,- which more than compensates for the slight disadvan tages of a less penetrating form. Moreover, as regards the preservation of the form, the rigid type does not appear to have much advantage over the Italian semi-rigid, since, with the rigid bow of the "T " type, the excess pressure of the gas in the envelope can be maintained relatively low, without fear of any inconvenience arising either during navigation or during mooring operations. The superiority of the Italian conception appears, however, not merely in simpler construction, but also and more especially in greater strength. This is evident when we compare the huge, delicate arrangement formed by the metallic framework of the Zeppelins with the strong, elastie * From an article published in GiornaU del Genio Civile. t The Italian Airship Factory have just completed one " M " type airship for Great Britain, and two ",0" types, one for the U.S.A., and one for the Argentine. Another " O " type is being built for Spain. This type of ship, derived from the " P " type (Crocco-Riccaldoni), may be considered as the most successful of Italian small capacity airships : it was designed by Engineers Pesce and Nobile. the Italian Government Airship Factory backbone formed by the longitudinal girder of the Italian type. This backbone is strong because its parts, being relatively small and exposed to great forces, have a resistance which we seek in vain in the framework of the Zeppelin. It is elastic, because its articulated joints—the peculiar characteristic of our longitudinal girder—give it an elasticity which enables the airship to withstand shocks and bumps, while the Zeppelin, as experience has proved, cannot support such shocks without serious damage. i! The "Roma" (U.S. Army) Italian semi-rigid airship in flight. r* 3 »-- io- ^^^S^ZEZEte= - The general arrangement of the Italian semi-rigid airship " Roma," which has been bought by the U.S. Govern ment. The envelope, which resembles somewhat the Astra-Torres type in cross-section, except that it has four " lobes," is divided by diaphragms into twelve compartments, and is attached to an articulated metal backbone. Capacity, 1,200,000 cu. ft. ; length, 412 ft. ; max. diam., 82 ft.; disposable lift, 16 tons ; six 400 h.p. Ansaldo engines, separate propellers ; speed, 68 m.p.h, ; range, 5,300 miles.
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