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Aviation History
1929
1929 - 0263.PDF
FEBRUARY 7, 1929 THE SLATE ALL-METAL AIRSHIP THE construction was just recently partially completed at Glendale, Calif., U.S.A., of an all-metal airship, designed by Thomas B. Slate, of the Slate Aircraft Corp. This airship constitutes a radical departure from any hitherto designed, not only in being constructed entirely (including the envelope) in metal, but in the power plant employed and the system of propulsion. Apart from this, however, it is also remarkable in other ways, and we hope, therefore, that the accompanying notes and illustration will be of interest. As indicated above, the hull, or " envelope," of the Slate dirigible is of metal and not only serves as the container for the gas—being made gas-tight for this purpose—but also is so constructed to form the main structure of the complete airship. In other words, there is no main framework of longitudinal girders and transverse members—as usual in other rigid airships—but the strength of the hull is built into the cover itself. The latter is composed of corrugated strips of duralumin mounted longitudinally on circular transverse " ribs " located In the Slate dirigible, the power system consists of a genera-ting plant comprising a high-pressure flash-type "boiler" made up into two to four units, with condenser. Only5 gals. of water are used in the entire plant, which gives about 600 lbs./sq. in. pressure, and it is. stated that but 1 gal. ofwater is consumed for every 1,000 miles of travel. The entire power plant is divided into seven units, com-prising that number of steam turbines of various sizes, giving a total of about 600 h.p. The main turbine, of 400 h.p.,is connected directly to a centrifugal " blower " mounted in the nose of the hull, and is supplied with steam from agenerator in the cabin. We will explain the purpose of this blower presently. Two other power units, each developingabout 40 h.p., are mounted one on each side of the cabin, at the forward end, and drive ordinary airscrews. The otherturbines include two of about 10-h.p. for operating cargo, etc., elevator hoists ; one of 8 h.p. for operating electricgenerator for wireless, lighting, etc. ; and one supplying power for, we understand, the operation of the generating THE SLATE ALL-METAL AIRSHIP : Our picture shows a novel American airship, constructed entirely of metal (including envelope) by the Slate Aircraft Corporation of Glendale, California, being brought out of its shed for an airing prior to the fitting of its steam power plant. at intervals along the full length of the hull. In this way, it is claimed, a very light but strong structure is obtained, the corrugations permitting expansion and contraction of the metal without developing strains. In fact, the designer claims that this metal-shell type of construction is three times stronger and one-third lighter than any other form of con- struction previously employed. The hull, which is of good streamline form, has an overall length of 212 ft., and a maximum diameter of 58 ft. The total volume is 330,000 cub. ft., giving, with hydrogen, a total lift of approximately 21,000 lbs., and a pay load of 7,000 lbs. Immediately beneath, and flush with.the hull, at the forward end, is a long car, with the control station in front and the passengers' cabin aft. Not the least interesting feature of this airship is the power plant, and method of propulsion. Steam is employed for the power plant—a medium which, though never yet successfully put to practical use in the propulsion of aircraft, possesses (in theory, at any rate) several desirable qualities for this purpose. plant (water pumps, etc.). The total weight per horse power of the entire plant comes out at about 3 lbs. It is stated that two kinds of fuel are used—natural or ordinary commercial gas, and refined crude oil. Thus, it is claimed, a perfect weight balance is obtained, the gaseous fuel lifting the weight of the liquid fuel, thereby relieving the gross lift of the airship of fuel weights ; it is also possible for the airship to gain or lose altitude by burning one or other of the fuels, or to maintain even altitude by burning an equal quantity of both ! • We now come to the novel method of propulsion employed in the Slate airship, which is as follows : the " blower " in the nose, previously mentioned, and which is 4 ft. 10 in. dia- meter, draws in air from the front of the airship and throws it back along the surface of the hull. A partial vacuum is thereby created ahead, inducing a suction effect on the air- ship, while the air-stream flowing backwards gives rise to a positive pressure at the rear, which drives the airship forward. The air stream also assists the effective operation of the tail control surfaces. The blower rotates at a speed of 4,000 to 6,000 r.p.m., 101
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