THE very word airship implies a craft that will * plow the air, much as a large ship plows the sea. From the beginning, the principles of marine navigation have governed the design of dirigible airships. Those who dreamt of great aerial crafts journeying from one inland port of call to another, and voyaging over housetops and forests, were unquestionably inspired by the performances of sailing vessels, and later, of giant steamships. There were difficulties which no engineer seemed able to overcome in placing aerial navigation upon the same sure footing as traveling by sea. The gas bag seemed too much like a huge, unwieldy soap bubble, which might be easily pricked and which could not weather a storm with the same facility as a great liner. The last ten years have witnessed a remarkable change in the attitude of the engineering world toward the dirigible. There is no reason, as experience has taught, why the dirigible cannot be made stout enough to weather any storm. Indeed, we have lately seen that the giant Zeppelins are far safer in the air than they are on the ground simply because of the impossibility of training two hundred men to act in harmony when it become lt's necessary to guide the huge gas bag into a shed. It soon became apparent that if the dirigible was to be speedy and was to have great endurance, it must be made larger than heretofore. Th8 dirigibles of our day are some of them six times the size of the first airships that were considered practical. The larger they grew the safer they became in the air. And the larger they grew the more like the ocean steamship they became in their appointments. A modern Zeppelin or Parseval, with its huge railed-in engines, its board floor, its brass fittings, its comfortable chairs, is astonishingly like a well-equipped trans-Atlantic liner. Modern air travel has driven home the theoretical truth that as you make a dirigible larger it also grows smaller in a sense, a paradox which even engineers have only lately admitted. The problem of transportation consists in handling the largest load with the smallest amount of machinery possible. It is far cheaper to convey 40,000 tons in one steamer than in two, to haul a huge load by a single 425-ton locomotive than by two 250-ton locomotives. If the dirigible is ever to become a faetor in the commercial transportation of cargoes it must be big. The dirigible can be increased in every direction, with a corresponding increase in lift. The aeroplane can be increased in size only in one or two planes, and then at the risk of obtaining surfaces so huge that they cannot be properly supported or easily managed. The bigger the dirigible airship can be made, the greater are its advantages. First of all, there must be considered the increased radius of action with a single charge of fuel; secondly, there is increased speed; thirdly, there is a relative diminution of gas losses; fourthly, there is the possibility of ascending to great heights, and of profiting by wind changes at different levels; fifthly, there is the assurance that rain, snow, sleet, can have no serious effect upon the structure; sixthly, there is obtained a surface so tough and stout that no sheds are required; seventhly, there is greater safety at anchor; and eighthly, there is more comfort to passengers. First of all we must show how the size of the airship can be increased without weakening the structure or increasing its weight inordinately, and, next. how and why the eight different advantagcs enumerated are attained, and finally, why dirigibles of large size are more safely handled near the ground than small vehicles. A giant dirigible could be constructed, to my mind, by combining tens, and even hundreds, of dirigibles of the present size, and bundling them into the proper shape. It is obvious that this bundle can weigh no more than the sum of the weights of which it is composed. If this “bundle could be propelled by the By Carl Dienstbach combined force of the motors of these small dirigibles, it would obviously move much faster through the air than if each small dirigible flew singly. Why? Because the placing of many dirigibles behind on2 another will decrease the head-on resistance, so that the surfaces behind the bow would meet with no resistance but skin friction. It is true that skin friction is nowadays considered a serious obstacle to high speed; but a bundle of dirigibles will have less skin friction than all the dirigibles flying singly, simply because in a bundle only parts of the surfaces of the outer dirigibles are exposed to the atmosphere. The scheme could be carried out far more easily than may appear at first blush. The load in fuel, motors, propellers, rudders, and ballast, must be s.o distributed that each gas bag has principally one kind to carry. The dirigibles on the outer side of the bundle would alone be provided with propellers and rudders (and the rudders would be confined exclusively to the bow and stern). These propellers and rudders would be distributed over about one-third of the outer surface. One large rudder would be excessively heavy if sufficiently strong; therefore, a large number of small rudders must be installed instead. Within the bundle will be found auxiliary machinery, dynamos, ventilators, living quarters, store rooms, and fuel tanks. Externally, the bundle will appear as a giant torpedo, with no huge car suspended below. Whatever cars there may be will be more in the nature of a continuous saloon, forming practically part of the under surface of the bundle, so as to cut down head-on resistance. Some projections there will be, such as promenade decks, bridges, observatories, wireless antennr, and the like-all too small, however, to break the general outline. Indeed, the only projections that might cause comment (aside from the lifting horizontal aeroplane rudders) are the hundreds of propellers studding the entire surface, ranged, in rows around the entire outer surface in spirals of small pitch, not unlike the rifling that runs within the bore of a modern gun. Such a spiral arrangement avoids interference of many propellers with one another, so that each may work in undisturbed air. Only the bottom surface of the bundle, to which the saloon is attached, is free from propellers. In principle, these propellers are like those which Zeppelin bas so effectively employed. They will be mounted as he mounts his, except that those near the bow and stern are to be swiveled so that they can be swung in any direction to exert a steering effect, and to assist the rudders, especially in landing. Horizontal rudders of the multi-plane type used by Zeppelin are distributed along the flanks of this huge dirigible. “Vertical rudders of the sam8 type are dustered around bow and stern. Most important of all are the internal arrange- ments of this mammoth airship. The Zeppelin compartment system of storing gas is developed to the utmost. There will be hundreds of gas cells, many “inside cars” or small gas-tight compartments to accommodate motors, machinery, stores and passengers. Special ventilating apparatus will be required to keep the air free from hydrogen so as to prevent the formation of an explosive mixture. The machinery must be so distributed that its weight will be carried by certain groups of gas ceUs. The walls of the gas cells are designed to form tunnels so as to provide passageways between the “inside cars.” Piping and electric wiring (suitably protected) runs through the whole interior structure. In more or less close proximity to the outer skin the gas cells are traversed by chafting from the many motors, and by transmission gears to operate the many rudders. It goes almost without saying that the rigid system will be used in the .onstruction of this aircraft. Theoretically, the entire complicated fabric might be held without buckling by balloonettes kept distended by blowers. Tn practice, however, it will be difficult indeed to use any but the rigid system. There is this point gained, however, that with this “honeycomb system” rigid construction is less wasteful of weight than in a Zeppelin. The frame does not need to be so strong, as the bnoyancy of the gas itself braces the whole structure, for the bracing effect which in a spherical balloon the gas exerts only on the upper part of the envelope, is here extended over the entire structure. Nevertheless a dirigible built along these lines is subject to certain limitations as regards size. The frst point which has to be considered is the necessity of keeping the balloon right side up. This forbids us to distribute the weight quite uniformly throughout the whole structure, for of course there must be an excess of weight at the bottom. This requirement introduces an element of weakness in very large dirigibles. We have here a very good illustration of a general principle, namely, that as a structure is increased in size, its weight and strength do not increase in the same proportion. For even if we only consider the ropes by which the balancing weight is attached to the envelope, as the sb:e of the airship is increased, these ropes must be made both thicker and longer. Now their strength is proportioned to the thickness, their weight, on the other hand, to the product of their thickness into their length. Another limiting factor is found in the internal stresses set up during any sudden acceleration or retardation. It has been tacitly assumed that each gas cell is proportioned only to take care of the inertia or momentum of the load which it has itself to carry. As a matter of fact, it must, in addition to this , bear the cumulative strain of the loads of the entire row of cells in front or behind, as the case may be. This difficulty, however, is not as serious as at.first sight appears, for the mass of the outer envelope and the inner framing is so large in proportion to the surface, that very abrupt motions of the ship are practically out of the question. A third limiting factor which suggests itself, would seem to lie in the fact that the thrusts of hundreds of propellers would have to be borne entirely by a single prow, which would either be unable to sustain this stress, or else would have to be made stronger and heavier than would correspond to the individual dirigibles of which we have imagined our bundle to be composed. As a matter of fact this objection also is fallacious, and the thrust of the numerous propellers is not really cumulative, for the resistance against rapid flight arises chiefly from fkin friction. Hence the thrust of each propeller is taken up mostly just at the point where it is applied-along the fanks. Nevertheless, such limiting factors as these do unquestionably preclude an indefinite increase in 186 size of the balloon. Yet the dimensions which are permissible are almost incredibly large. Moreover, a great advantage can be gained by neutralizing the crushing effect of any local wind pressure. This can be effected by the simple expedient of providing suitable vents through which the air pressure produced by the wind finds its way instantly into the interior of the structure. In thIs way the pressure against the prow in rapid flight is taken up quite as much by the rearmost internal gas cells as by the forward ones. The pressure from within is rendered equal to the pressure from outside. (The small and flimsily constructed captive balloons known in Germany as “kite balloons” are built on this plan and have weathered hurricanes that tore them from their cables but were powerless to crush them.) The vents should be well proportioned and provided with valves, as it might be found best to limit the pressure of the wind, with the result that the strain on the side of the structure would be eliminated in spite of the hundreds of revolving propellers. The thrust of the air resistance in front is neutralized (in the material) by the pull of the suction in the rear. Thus, for instance, we may have a pressure of ten pounds per square foot upon the outside of the prow; the vents might provide a pressure of fve pounds per square foot on the inside, leaving fve pounds per square foot to be taken up by the material along the sides. But the vents also provide fve pounds per square foot on th"3 inside of the stern, and this pressure is not opposed by any counter force from outside, but on the contrary is assisted by a suction. This results in a pull along the sides in. the material, which exactly compensates for and eliminates the compression. As it has been conclusively shown how that the “bundle” of balloons moves faster than the component dirigibles singly, the radius of action, or the fuel supply carried, may be much increased by making the power plant weaker than the sum of the component dirigibles' aggregate power. A further decrease in power (without much lowering the speed) and in the load carried, will secure the additional advantage that the ship may be floated with partially inflated gas cells, and, supported by its aeroplane rudders, allowed to ascend to the highest levels. The larger the volume of the dirigible, the smaller is its surface in proportion to its lift, or to the gas carried. If the air space between the outer skin or envelope and the interior gas bags, which has proved so useful in Zeppelin airships, is introduced into the design of a mammoth dirigible, it will completely eliminate all troubles arising from variations in the lifting power caused by a change in temperature under the influence of the sun's rays, or of darkness or shadows. Furthermore, it is obvious that the adventitious load which may collect upon a dirigible in the form of min, snow or sleet, or ice, .is proportional to the surface area. If this area is small as compared with the lift of the balloon, the effect of such unwelcome 'allast is correspondingly reduced, and the mammoth dirigible approaches in this respect the sea-going vessel, which is practically quite unafected under similar conditions. The numerous propellers will incidentally serve a useful function by blowing a strong blast of air along the surface of the car, whereby any snow or rain will be swept of. An obvious improvement which suggests itself would be to heat the air space around the gas bags with the exhaust from the motors, thus preventing ice from forming upon the outer envelope. By fushing this space with hot exhaust gas, or cool air, as the case may be, the balloon gas within may be rendered entirely independent of outside infuences. The volume of the air space is comparatively very small, and there is enough exhaust to infate it in a few minutes. The task is much facilitated through the fact that all the motors are in comparatively close proximity to the outer envelope, and are distributed more or less evenly over the whole structure. TJis device should be of great assistance in adding to the lifting power of the mammoth dirigible. For it will keep the temperature of the gas much above that Of the frigid air at an altitude of three miles, for example. It is, of course, well understood that this circumstance increases the buoyancy. One objection which perhaps arises in the reader's mind, is the danger from fre. As a matter of fact, the problem of guarding against this is no greater than that daily faced in coal mines. The Davy wire gauze screen must be used to the fulest extent of its possibilities. Its weight need be but small. First and foremost the carbureters must be inclosed in absolutely proof gauze baskets. In addition to this the entire engine room should be similarly protected. All electric insulations must be as perfect as those near the powder magazine of a warship. Exhaust tubes must be water-jacketed, asbestos-lined and inclosed in wire gauze, and the same applies to the mufers. The gasoline tanks should be placed at SCIENTIFIC AMERICAN the very core of the ship, far from the engines, and the fuel should be forced under pressure through elender but strong tubes of annealed copper, which would stand any vibration or shock. All joints must be we.ded by the autogenous process. 'hese tubes run through small tunnels continuously flushed by a current of fresh air. The principal safeguard against fre is the elaborate ventilation system which instantly dissipates any escaping gas or gasoline fumes at any portion of the interior. The weight of these safety devices is but trifling. Tn point of ventilation the airship has this great advantage over the ship traveling by water, that it receives the relative wind always from the same quarter and with a never lagging force while under way. The mechanical blowers receiving the air (from the vents) already partially compressed are thus relieved of a considerable portion of their work. When the balloon is stationary the main motors become available for driving the ventilating engines: At the moorings in the harbor compressed air for the safety ventilation is taken from fxed mains 'through a flexible hose. A great air harbor 0[ the future will include a blower plant similar to that of a foundry. The complicated system for the circulation of water, air, steam and for the distribution of electricity, so 'familiar on large ocean vessels of our day, is not only a convenience, but becomes a vital necessity in the dirigible of the future. This safety ventilation, on the other hand, tends to increase the gas losses. If the entire structure were one great gas space, the volume of gas would be so great in proportion to the surface, and the outer envelope so thick, that the loss would be insignificant. The captive balloon at the Paris Exposition, with 25,000 cuNe meters capacity, has proved this. But in the practi()al airship here .described, the proportion of the total surface of the gas cells to their volume is jast as great as for a single one of the individual cells of which it is composed, nor are the walls any. thicker. However, the gas loss by slow flltration through the envelope is even in the balloons of the pres(mt day more than compensated for by reduction in fuel weight, and as a matter of fact, troublesome gas losses occur only through expansion by ascension or under the influence of the sun's rays. This last source of loss is completely overcome in the dirigible of the future. In order to avoid having to blow off gas when the fuel supply (ballast) rUll low, the gas itself should ,be used as fuel, and not run to waste: The cost of housing a very large airship would be a serious difficulty. But there is no reason why a balloon should not be moored in the open, provided that two conditions were complied with, botlr of which ale fulfllled -y the mammoth dirigible. The frst requirement is sufficient toughness of the outer envelope, so that neither min nor snow nor sun could harm it. The second condiHon is sufficient strength of structure to withstand the pressur.e of a gale. (As the air offers nowhere a real harbor in the same sense as a sheet of water, but only open anchorages, in an excessively severe storm Ian airship must simply take the same steps as would be adopted by a steamer in the open sea-raise anchor and get up steam.) The second condition is obviously fulfUed if the normal speed of the ship is equal to that of a storm. The anchor cable must of course be attached to the bow, in such way that th entire frame acts toward tension stresses as an elongation of a eable. In a severe hurricane propellers can be started to ease the strain on the cable. The strength of the structure in proportion to its bow area and the vent system provide ample margins of safety. Absolute safety will be secured by anchoring a ship to a high tower, around which it would swing freely as a weather vane. But the Zeppelin method of holding the bow close to the ground and allowing the stern to foat and swing, relying on the jamming of the wind between the hull and the ground to prevent a fatal collision with the ground, also holds great promise and has the advantage of simplicity. It certainly has proved efective in very high winds. After leaving the dockyards a mammoth dirigible must remain afoat as steadily as a ship in order to be manageable. This problem presents no difculty at the present time, being solved in the Parseval airships by the daily injection of small quantities of fresh gas. If this is efective in an airship with a single gas space,, it would be even” more so in a multi-cellular ship, in which the gas in the cells may be completely renewed by emptying and infating cells alternately without decreasing the fotation more than cal be readily allowed for in the harbor. In the same way entire, gas cells may be removed and new ones inserted while the ship remains afoat. It may even be possible to devise a method for eliminating the air from deteriorated gas, extracting the _ latter from the cells and returning it to them regenerated. A mammoth dirigible provides all the comforts of a steamer. Staterooms would be located in the in- August !t, 19 J 1 terior, dining saloons, kitchens, stores, etc., near tho bottom, promenade decks on the top. It is interesting to note that elevators weigh less than slairs, especially those built on the plan of modified rope ladders. lurthermore, monorails with light cradle frames running over them weigh less than passageways with walking floors. A new system of rapid intercommunication must be introduced on board the dirigible of the future to save weight and insure comfort. Incidentally it would prevent the sudden shifting toward one point of the weight of many passengers. No doubt the mammoth dirigible will prove weaker if it collides with the ground than a dirigible of to-day. But similar objections hold in the case of ships on the water, and still their size is increasing' at a rat! which makes us smile at the “Great Eastern” of years ago. A rowboat is but little damaged by a collision. If the “Titanic” should drift at slow speed against a rock, its steel plates would crumble like paper. If the parts of a steamer are stronger than those of a dirigible, the total weight of a steamer, which determines the crushing force, is also greater in the same proportion. Ships are placed under much the same circumstances on the water and in the air, and in either .case must be jealously guarded against any possible collision. In the case of a dirigible, the danger is greatest while it is being handled near the ground, but the mammoth dirigible, after it is once launched from the dockyard shed (in absolutely quiet air, of course, as at the recent launching of the English naval dirigible), does not need to be handled near the ground because it does not enter a shed. It may be moored to a tower or upon a broad unobstructed plain by its own engine power, which is great enough to control very heavy winds. This means that with its propellers the ship can be held motionless against any wind. With the aid of the rndders even sudden gusts may be resisted, inasmuch as they cannot produce any jerky motions in a ,body of such large bulk. (To anchor in a severe storm is as inadvisable as it would be on the water-storms must be outridden.) ''he operation of landing on a plain would involve some very nice work of the horizontal rudders while the ship is driven energetically with reversed engines. The bow is dipped down toward the ground, anchor is cast, and the engines are reversed to their normal motion to ease the jerk on the anchor. Then the engines are reversed again and at the same time the anchor is hauled in. In this way the anchor is made to bite the ground so firmly that it will stIlI hold even after the cable has been shortened from 20 to 30 feet (this terminal portion of the cable being made twice as strong as the rest). The propellers are kept revolving until the anchor has been permanently secured. A flexible “gang plank” is dropped to the ground from the bow, while the ship's stern remains foating high in the air. “Very similar maneuvering has been successfully used on the Zeppelins. Keeping some of the propellers revolving with reversed motors is of C011rse an excellent way of guarding against any coUision of the bow with the ground, even in heavy and irregular gusts, while thus anchored. If the airship is to be made fast to a tower it must be skillfully brought near the top of the tower, best by drifting past with the wind, at a moment when the wind is fail'ly steady. Several attempts may be necessary before success is attained. In this case also it may be a good plan to keep some of the propellers revolving in the reverse direction. Fantastic as this mental picture of the giant airship of the future may appear to us with our present notions of aerial navigation, when we think of our sky scrapers and the 50,000-ton leviathans plying the sea, it appears that the picture here drawn is well in accord with the modern tendency, and in 'act it is to be expected that the 1,000-foot airship will make its appearance before very long. The Opium Problem in Parts of China SOME unexpec ted results are found fromm the m ovement against the production of oplUm in Chm a. In th( Yunnan, one of the provinces where opium was produced in large quantities and at a 10w price and where a great deal of it was consumed, it appears that the PO]PY is no longer cultivated, owing to the recent measures, and the poppy felds have quite disappeared, according to the statements made by Drs. Talbot and Rigaud. However, this has had a disastrous efect on the honey culture of the rngion. Tn fact, the honey from Yunnan was renowned 1or its Cuality, but as the bees fnd no more fowers, the production of honey is stopped as well. The new crops which replace the poppy, such as wheat or peas, are not such as will give a honey yield as well. On another side of .he question, it appears that the habits of the population are not suppressed by the present legislation, as some supposed would be the case, but according to' Dr. Talbot, opium-smo!dng is again on tbe increase.
This article was originally published with the title "A Study of the Giant Airship of the Future" in Scientific American 105, 9, 185-186 (August 1911)