The vessel was propelled at 60 miles an hour in still air—by means of six Maybach-Mercedes gasoline engines of 240 horse-power each, or 1,440 horse-power in all. Each had six vertical cylinders with overhead valves and water cooling, and weighed about a thousand pounds. They were connected each to a propeller shaft and also to a dynamo used either in lighting or for furnishing power to the wireless installation. One of these engines with its propeller was placed at the back of the large forward gondola; two were in the amidships gondolas, and three were in the after gondola. In the last case one of the propellers was in the centre line of the ship, and the shafts of the two others were stayed out, one on either side. The gasoline-tanks had a capacity of two thousand gallons, and the propeller shafts were carried in ball bearings.
Forward of the engine-room of the front gondola, but separated from it by a small air space, was first the wireless-operator’s cabin and then the commander’s room. The latter was the navigating platform, and in it were concentrated the controls of the elevators and rudder at the stern, the arrangement for equalizing the levels in the gasoline and water tanks, the engine-room telegraphs, and the switchboards of electrical gear for releasing the bombs. Nine machine-guns were carried. Two of these, of half-inch bore, were mounted on the top of the vessel, and six of small caliber were placed in the gondolas—two in the forward, one each in the amidships ones, and two in the aft one. The ninth was carried in the tail.
The separate gas-bags were a decided advantage over the free balloon and earlier airships, which carried all the gas in one compartment; for if the latter sprung a leak for any reason it had to descend, whereas the Zeppelin could keep afloat with several of the separate compartments in a complete state of collapse.
Since the Zeppelin, like all airships, is buoyed up by hydrogen gas—which weighs one and one-tenth pounds per two hundred cubic feet as compared with sixteen pounds which the same amount of air weighs—the dirigible is sent up by the simple expedient of increasing the volume of gas in the envelopes until the vessel rises. This was done by releasing the gas for storage-tanks into the gas-bags. In order to head the nose up, air was kept in certain of the rear bags, thus making the tail heavier than the forward part, which naturally rose first. Steering was done by means of rudder or the engines, or both, and the airship was kept on an even keel by use of lateral planes. The airship could be brought down by forcing the gas out of the bags into the gas-tanks, thus decreasing the volume, and by increasing the air in the various compartments.
This airship had a flying radius of 800 miles, could climb to 12,000 feet, could carry a useful load of 30 tons, and could remain in the air for 50 hours.
Because so many Zeppelins were lost to Germany and because so much time and money were necessary to construct the enormous airships, many people have jumped to the conclusion that the rigid dirigible was an absolute failure even as an offensive war weapon. Yet despite its bulk and the fact that it could not fly faster than seventy miles an hour, and though more than a hundred Zeppelins raided England at some time or another during the war, only two were shot down by aeroplanes and only a few by antiaircraft guns. Most of them were destroyed because they ran out of fuel and consequently became unmanageable and were blown out of their course and forced to land or had to descend so low that they came within easy range of aircraft guns of the land batteries or the naval guns.
This record is truly surprising when we stop to consider that the Zeppelin had to navigate entirely by compass and mostly at night over hundreds of miles of hostile sea and land, opposed by the guns of a huge Allied fleet and thousands of antiaircraft guns, without lights or landmarks to aid them and often with untrained and inexperienced pilots to guide them! No wonder that some of these airships met disaster—like the L-49, which had to land in France; or the L-20, which was forced to land on the Norwegian coast near Stavanger; or others, which came down so low over the North Sea that they became easy targets for the British torpedo-boat guns.
But this is judging the Zeppelins purely as offensive weapons of war. Even as such they forced the British Empire to maintain a large standing army and a huge armament of guns and aeroplanes in England by threatening to land a mammoth army of invasion there from Belgium. What they did to spread terror in Belgium and to keep the German army informed by wireless of the conditions behind the British and French and Belgian lines in the first advance to the Marne is a matter of history. Also what they performed in disorganizing the armies and in disconcerting the people of Antwerp and Bucharest, not to mention many Russian cities and Paris itself, during the Hun advance against those cities, is almost too horrible to relate. Over the Rumanian capital alone they descended so low—because there were no antiaircraft guns to defend the city—that they scarcely flew clear of the buildings as they rained down hundreds of tons of high explosives on the frightened inhabitants, and even bombed a part of the imperial palace, where the Queen was nursing the Crown Prince.
This unlawful use of these giant aircraft does not detract from what they demonstrated could be done in the way of aerial navigation and transportation under the frightful opposition of war, and it is only an augury of what will be accomplished when the same vessels of the air will be put to carrying man up and down the aerial highways of the heavens, which know no barriers, obstructions, or hostile opposition.
Their greatest service to the Germans was as aerial scouts rather than as ethereal battleships or cruisers; and if these rigid dirigibles had performed no other feats for the Huns, from the Teutonic point of view at least, their work in planning and directing every move of the German high-seas fleet in the great naval battle off Jutland amply repaid Germany for the time and money and effort expended in building those air cruisers.