Luftschiff / Airships
Few efforts in the history of world armaments may be said to parallel in their intensity the creation of the airship fleet by the use of which Germany intended to become supreme in the air and so attain the mastery of the world. Despite repeated setbacks, involving huge monetary losses, to which the war added severe casualties, the forging of this weapon wrent on unabated for ten years-till the armistice spelled the doom of Germany's mighty aerial armada.
The magnitude of this effort may be appreciated from the fact that between 1908 and 1918 Germany launched and commissioned a total of 140 war airships, of which number 14 were at hand when the war broke out and 109 were built during the period of hostilities. Of the latter all but three airships were of the rigid type and of a size vastly exceeding anything the Allies produced in this line, the capacity of these vessels running from 800,000 cubic feet to 2,400,000 cubic feet, the horsepower from 630 to 2,000, the maximum speed from 52 m.p.h to 77 m.p.h.; and the useful load from 9 tons to 52 tons.
From 1897 on, experiments were conducted by Count B'erdinand von Zeppelin of the German Army on an immense airship to carry five men. It consisted of a rigid cylindrical aluminum framework with pointed made a speed oí 18 miles per hour ??? traveled 3% miles before an accident to the steering gear forced it to descend. A second airship, whose two motors developed 85 horsepower, was built in lOOTi, but was wrecked in a storm. A third ship, built in 1906, traveled around Lake Constance and reached a speed of 36 miles per hour, remained in the air for several hours, carrying a number of passengers. A fourth airship, of similar design but more powerful motors, in 1908 succeeded in traveling 250 miles in 11 hours, but was wrecked when on land and burned at Echterdingen. Subscriptions were at once raised to help Zeppelin build another, and from this beginning grew Germany's fleet of monster airships which were used in bombing raids and for purposes of observation in the European war.
Other dirigibles were the Parseval, developed by Major von Parseval of the Bavarian army, whose airship was of a collapsible type without a rigid frame, which could be readily transported by an army and inflated in the field from cylinders of compressed gas or generators ; the Gross airships, designed by Major von Gross of the German army, of a semi-rigid type; the Schutte-Lanz, a rigid airship with wooden frame and large gas capacity ; the Suchard, built for long distance travel, but not used for the ocean flights for which it was designed.
The Zeppelin was considered the supreme war dirigible, but with the increasing defensive ability of the anti-aircraft guns and the armored aeroplanes the destructive power of the big rigid airships has beer, greatly reduced. Many Zeppelin raids on London and other towns in England were undertaken during the European war. nt first with success but later with disastrous results to the huge airships, some of which containing from 750,000 to 2,000,000 cubic feet of gas, and costing from $1,000,000 to $2,500,000, were captureJ by the British forces. Toward the end of 1917 tho Zeppelin had been discarded for the heavier-than-air machines, and squadrons of bomb-carrying aeroplanes took up the work of raiding.
The constructional features of these ships as well as their production figures formed a strict secret during the war and the Germans even succeeded in withholding much valuable information until recently. As a consequence much of the data published initially was only approximately accurate, while some of it is absolutely inaccurate.
The German Empire attempted and achieved improved performance, now by adding a gas cell, now by increasing the horsepower, now by lightening the construction, until, having exhausted every possible means of improvement for a given type, they were forced to seek further progress in a much larger type of ship. And as soon as the latter would pass its acceptance tests and be put into production, the same process of detail improvements would be applied to it.
As a result of this policy which was applied only to the rigid Zeppelin and Schutte-Lanz ships-the number of basic types was kept down to a minimum and airship construction became strictly a production problem. With reference to the Zeppelin airships it may be seen from the table that there were actually but three production types, namely, those having a diameter of 49 feet, 61 feet and 79 feet, respectively, the Z.XII-L.9 class being an experimental one. The advantages of this system from the viewpoint of production are particularly obvious in the case of the Zeppelin airships, where the framework is composed of punch pressed duralumin rails and webs which are assembled into triangular girders. As these girders run longitudinally and transversely, the latter forming on the 79-foot diameter type a number of 25-sided polygons, the importance of having a minimum of standard parts becomes evident. This is further emphasized by the fact that each gas cell-that part of the framework comprised between two or three polygon frames-is braced by a large number of diagonal and radial wires, for which again a standard length is desirable.
Another reason which prompted the Germans to adopt a small number of standard diameters was the limit in height of their airship sheds. It is a curious fact that even the Germans-who are often assumed to foresee everything-did not think far ahead enough to provide housing facilities for the inevitable increase in size of their airships. They built, it is true, sheds wide enough to hold two ships side by side, but tor their larger Zeppelins these sheds were not high enough. As a consequence, all through the war the Germans experienced much inconvenience in concentrating Zeppelin squadrons and many of their ships were lost through fire or collision owing to crammed quarters and restricted maneuvering space in front of them. Thus, on one occasion, four of their largest and most modern airships were destroyed by a fire which started in the big shed at Ahlhorn, while at another time two ships collided and burnt up in attempting to enter the Tondern shed.
During the war the Germans strove with all their might to remedy this situation by building additional sheds, but in fact this work never kept up with their airship production, for about ten Zeppelins would be built in the time it took to erect a single shed of large size.
Zeppelin
With reference to the Zeppelin airships, the L.3 type represents pre-war design, the first ship of the series being completed just before the war. This type hud a long cylindrical hull of poor aerodynamical shape, cellular rudders and elevators of high resistance, and four propellers mounted on outriggers on the sides of the hull which were driven through bevel gear shafts leading to the cars in which the engines were housed.
While this type was in production the Zeppelin Co. built the first ship of an experimental type, the Z.XII, in which an effort was made to reduce the large amount of head resistance offered by the cellular control surfaces and the propeller drive. The control and stabilizing surfaces were combined in a cruciform tail and the forward outriggers were suppressed, the forward engine being made to drive, tnrough a gear box and a disc clutch, a single propeller fitted at the end of the car. The performance of this experimental type was so conclusive that when the authorities required the laying down of a type embodying a larger useful load, higher speed and higher ceiling, the Zeppelin engineers decided to adopt the new propeller drive and the cruciform tail for the new ships. At the same time it was realized that the performance could still be improved by giving this type a smaller fineness (length/ diameter) ratio and so it came about that the first war production type, the L.10, was only a few feet longer than the preceding type, whereas its diameter was 12 feet larger. The lineness ratio was thus reduced from 10.0 to 8.8 and the performance, owing to the better streamline of the hull, was notably improved. The outrigger propeller drive was retained for the rear car, but this now housed three engines, one of these driving a stern propeller, and another stern propeller was mounted in the forward car. When, in the summer of 1915 the new Maybach 240 hp. engine became available, it was substituted for the old 210 hp. type, resulting in a slight increase in speed of these ships.
Before the close of that year a new problem came up, however. The greatly improved climbing ability of the Allied airplanes and the greater accuracy of anti-aircraft guns now made it imperative for the German airships not only to climb higher than heretofore, but also to climb faster. The naval nnd military authorities of Germany therefore demanded a greater margin of useful load to allow for carrying extra ballast. The Zeppelin engineers temporarily solved the problem by adding a gas cell to the L.10 type, whereby the useful load was increased by about a ton and a half. The resulting L.20 type was, however, soon to be replaced by a vastly improved vessel and when this made successful trials, the production program of the L.20 type was stopped with the sixth vessel of the series, which was then in process of construction.
The new airship, the L.30, was the first of the so-called "super-Zeppelins"- as they were referred to during the war. In the design of this type the Zeppelin engineers once more used the familiar procedure of increasing the diameter at a greater rate than the overall length, and by so doing they reduced the fineness ratio to 8.2, producing a ship of notably clean lines. The most remarkable innovation found on the L.30 type is, aside from its huge size, the propeller drive. The power plant consisted of six 240 hp. Maybach engines which drove six propellers disposed as follows: Two astern of the main cars, two on outriggers aft, and two amidships on small "wing cars," fitted on either side of the hull, which served as engine rooms only. Owing to the head resistance of the outriggers and the interference of several propellers with one another, the performance of this heavily engined airship did not entirely come up to expectations, and steps were accordingly taken to "clean up" the design.
First the number of engines was reduced to five, the stern propeller of the after car being dispensed with together with its engine. Then, on another type, the outriggers were also suppressed so that the number of propellers was reduced to three, that is, one astern of the forward car and two on wing cars. The latter were however fitted with two engines each, either or both of which could drive the propeller through a suitable gear box and clutch arrangement. This scheme, which was intended to provide for emergencies, proved so satisfactory that the principle was incorporated in the final design of the modified L.30 (or L.48) type. In the latter there were four propellers disposed In a quadrilateral, two being in the center line and two in wing cars, and the rear main car housed two engines, one to be used for emergencies. The saving in head resistance which the suppression of the outrigger propellers represented enabled these ships to have a much better performance than the L.30 type, although their power plant was smaller. The great reluctance the Zeppelin engineers displayed in parting with the outrigger drive may be understood when it is known that this system was their own invention, whereas the wing cars had been originated by the rival Schutte-Lanz firm, which has used this drive on all of its ships ever since 1914.
The next step in improving the L.30 class consisted in generally lightening the construction. Thus the stern was deprived of its gas bag, it being deemed that the lift derived from it was out of proportion to Its weight. Then, In the summer of 1917, came a much more radical innovation. The L.48 type, or L.30 type with the standard propeller drive, was entirely redesigned in detail, as a result of which the length of the gas cells was increased from 33 feet to 49 feet and their number was reduced from 18 to 14. The saving in dead weight amounted to a ton and the ceiling of the ships was improved in proportion, while maneuvering became more convenient owing to the lesser number of gas bag controls. Against this advantage was the drawback that the hull, having now two intermediate transverse girders between the main, stress-taking, frames, proved less resistant than the old design and required frequent overhauling. The introduction of a new high resistance aluminum alloy only partly solved this problem.
Another danger against which the Zeppelin engineers had to provide in this L.53 type was the surging of the gas against the high side of the ship or against the wire wall of a gas cell that might accidentally become deflated. To provide against this contingency, which might have serious consequences owing to the large amount of gas contained in each bag- about 200,000 cubic feet in those located in the parallel portion of the hull-each gas bag was not only securely fastened to the framework by wires, but it was also internally trussed by radial wires.
Having reduced the number of gas cells in the improved L.30 type, the Zeppelin engineers were once more at liberty to increase its size for special requirements by the addition of further gas cells. Thus in the L.57 type, which was produced for special long range scouting, the capacity was Increased to 2,400,000 cubic feet and the useful load to over 52 tons, with a corresponding decrease in speed and ceiling. Only two ships of this type were built, one of which made a 4,500-mile flight from Yamboli, Bulgaria, to the Soudan and return In an attempt to deliver 12 tons of medical supplies to the German forces in East Africa. Before the airship could reach its destination, however, it was recalled by a radio, the German forces In question having surrendered in the meantime. This flight is the longest non-stop voyage made by an airship to date. In the winter of 1918 it became increasingly evident that unless the German airships could show a much better speed and climb they would, one after the other, be brought down by Allied airplanes and anti-aircraft guns. In an endeavor to solve this problem the Zeppelin engineers first fitted the L.53 type with the 290 hp., or super-compressed, Maybach type engine, and later produced the L.70 type, which was the most heavily engined airship ever built. It had seven 290 hp. engines, four of which were mounted in wing cars, and developed a speed of over 77 m.p.h., but its ceiling was already inadequate, for British aviators brought the ship down in flames In the North Sea on one of its enrly raids. The sisterships were thereupon modified by removing the reserve engine from the rear car, which increased their ceiling by 2,000 feet, and plans were laid down for the construction of a much larger series. The latter, L.100 type, was ordered before the armistice, but construction had not begun when hostilities ceased.
The German company Luftschiffbau Zeppelin, owned by Count Ferdinand Graf von Zeppelin, was the world's most successful builder of rigid airships. Zeppelin flew the world's first untethered rigid airship, the LZ-1, on July 2, 1900, near Lake Constance in Germany, carrying five passengers. The cloth-covered dirigible, which was the prototype of many subsequent models, had an aluminum structure, seventeen hydrogen cells, and two 15-horsepower (11.2-kilowatt) Daimler internal combustion engines, each turning two propellers. It was about 420 feet (128 meters) long and 38 feet (12 meters) in diameter and had a hydrogen-gas capacity of 399,000 cubic feet (11,298 cubic meters). During its first flight, it flew about 3.7 miles (6 kilometers) in 17 minutes and reached a height of 1,300 feet (390 meters). However, it needed more power and better steering and experienced technical problems during its flight that forced it to land in Lake Constance. After additional tests conducted three months later, it was scrapped. Zeppelin continued to improve his design and build airships for the German government. In June 1910, the Deutschland became the world's first commercial airship. The Sachsen followed in 1913. Between 1910 and the beginning of World War I in 1914, German zeppelins flew 107,208 (172,535 kilometers) miles and carried 34,028 passengers and crew safely. At the beginning of World War I, Germany had ten zeppelins. During the war, Hugo Eckener, a German aeronautical engineer, helped the war effort by training pilots and directing the construction of zeppelins for the Germany navy. By 1918, 67 zeppelins had been constructed, and 16 survived the war. During the war, the Germans used zeppelins as bombers. On May 31, 1915, the LZ-38 was the first zeppelin to bomb London, and other bombing raids on London and Paris followed. The airships could approach their targets silently and fly at altitudes above the range of British and French fighters. However, they never became effective offensive weapons. New planes with more powerful engines that could climb higher were built, and the British and French planes also began to carry ammunition that contained phosphorus, which would set the hydrogen-filled zeppelins afire. Several zeppelins were also lost because of bad weather, and 17 were shot down because they could not climb as fast as the fighters. The crews also suffered from cold and oxygen deprivation when they climbed above 10,000 feet (3,048 meters). At the end of the war, the German zeppelins that had not been captured were surrendered to the Allies by the terms of the Treaty of Versailles, and it looked like the Zeppelin company would soon disappear. However, Eckener, who had assumed the company's helm upon Count Zeppelin's death in 1917, suggested to the U.S. government that the company build a huge zeppelin for the U.S. military to use, which would allow the company to stay in business. The United States agreed, and on October 13, 1924, the U.S. Navy received the German ZR3 (also designated the LZ-126), delivered personally by Eckener. The airship, renamed the Los Angeles, could accommodate 30 passengers and had sleeping facilities similar to those on a Pullman railroad car. The Los Angeles made some 250 flights, including trips to Puerto Rico and Panama. It also pioneered airplane launch and recovery techniques that would later be used on the U.S. airships, the AkronandMacon. By 1920 the equipment at the Zeppelin Airship company's factory on the outskirts of Friedrichshafen comprised three good-sized factory buildings, the new laboratory, two airship sheds and a flying field. At that timee no construction was going on, the men who had been retained being engaged in clearing up old stock and in making other aluminum goods than airships, but the managers of the company were all set to go the minute that new construction or the operation of an airship transportation line on a large enough scale to be worth their while is permitted, and they were seeking orders in all directions. At that time the company employed two hundred men, a reduction from four thousand during the war. The airship sheds were occupied by the Nordstern and the Bodensee, without their gasbags in place. The Nordstern had never been inflated.
When the various restrictions imposed by the Treaty of Versailles on Germany were lifted, Germany was again allowed to construct airships. It built three giant rigid airships: the LZ-127 Graf Zeppelin, LZ-l29 Hindenburg, and LZ-l30 Graf Zeppelin II. The Graf Zeppelin is considered the finest airship ever built. It flew more miles than any airship had done to that time or would in the future. Its first flight was on September 18, 1928. In August 1929, it circled the globe. Its flight began with a trip from Friedrichshaften, Germany, to Lakehurst, New Jersey, allowing William Randolph Hearst, who had financed the trip in exchange for exclusive rights to the story, to claim that the voyage began from American soil. Piloted by Eckener, the craft stopped only at Tokyo, Japan, Los Angeles, California, and Lakehurst. The trip took 12 days-less time than the ocean trip from Tokyo to San Francisco. During the 10 years the Graf Zeppelin flew, it made 590 flights including 144 ocean crossings. It flew more than one million miles (1,609,344 kilometers), visited the United States, the Arctic, the Middle East, and South America, and carried 13,110 passengers. When the Hindenburg was built in 1936, the revived Zeppelin company was at the height of its success. Zeppelins had been accepted as a quicker and less expensive way to travel long distances than ocean liners provided. The Hindenburg was 804 feet long (245 meters), had a maximum diameter of 135 feet (41 meters), and contained seven million cubic feet (200,000 cubic meters) of hydrogen in 16 cells. Four 1,050-horsepower (783-kilowatt) Daimler-Benz diesel engines provided a top speed of 82 miles per hour (132 kilometers per hour). The airship could hold more than 70 passengers in luxurious comfort and had a dining room, library, lounge with a grand piano, and large windows. The Hindenburg's May 1936 launch inaugurated the first scheduled air service across the North Atlantic between Frankfurt am Main, Germany, and Lakehurst, New Jersey. Its first trip to the United States took 60 hours, and the return trip took only a quick 50. In 1936, it carried more than 1,300 passengers and several thousand pounds of mail and cargo on its flights. It had made 10 successful roundtrips between Germany and the United States. But that was soon forgotten. On May 6, 1937, as the Hindenburg was preparing to land at Lakehurst, New Jersey, its skin caught fire from electrical discharges in the atmosphere because the paint used was flammable. Then, gas cells one and two exploded. The accident killed 35 of the 97 people on board and one member of the ground crew. Its destruction, seen by horrified spectators in New Jersey, marked the end of the commercial use of airships. Germany had constructed one more large airship, the Graf Zeppelin II, which first flew on September 14, 1938. However, the start of World War II, coupled with the disaster that had befallen the Hindenburg earlier, kept this airship out of commercial service. It was scrapped in May 1940. http://www.centennialofflight.gov/essay/Lighter_than_air/zeppelin/LTA8.htm Airships: DJ's Zeppelin Page: http://www.airships.net. The Zeppelin Museum. http://www.zeppelin-museum.de/ Balloons had been used in wars prior to the First World War, notably by the Americans in the civil war and the French during the siege of Paris in 1870. This technology had been advanced by the development of dirigibles - cigar shaped airships with frames, containing many gas balloons. Powered with multiple engines, these craft could be flown in specific directions rather than just follow the direction of the wind. Germany had two dirigible manufacturers, the Schutte-Lanz Company, and the larger and better known Zeppelin Company. The latter was headed by Ferdinand von Zeppelin, the world's foremost designer of airships. To this day his name remains synonymous with dirigibles in general. Airships of his design had already proven themselves capable of flying as far as England and back. This fact was not lost on the Allies, who from the very outset targeted the airship sheds. It was also not lost on the British public, where rumours and reported sightings of Zeppelins were frequent, though unfounded, throughout 1914. At the outbreak of the war the German army had six operational dirigibles, and the navy had one. The army was quick to experiment with them - bombing Liege and Antwerp - despite the fact that at this stage no specially designed aerial bombs existed. But the army's initial experience was not encouraging - they lost three airships in the first months of the war to anti aircraft fire. Despite this the navy was very enthusiastic. They saw the Zeppelin as a solution to their reconnaissance problems. If the army traditionally used the cavalry for reconnaissance, the navy traditionally used the light cruiser. Germany had very few such ships, and an airship was viewed as being cheaper and less vulnerable. Under the command of Korvettenkapitan Peter Strasser the navy quickly acquired more airships. Throughout 1914 these were used for reconnaissance patrols over the North Sea, but the German Admiralty was pressing for permission to use them for attacks against England. The Kaiser, somewhat reluctantly, granted such permission and on the 19th of January the Germans carried out the first Zeppelin raid against Britain, killing two and injuring sixteen. This was the first of many raids, which continued at a rate of about two per month, in parallel with the continuing reconnaissance patrols. The German Admiralty was very enthusiastic about the results, and asked for permission to bomb London. This was only granted by the Kaiser after a series of raids by French bombers on German cities. On the 31st of May 1915 the first raid was carried out against London, killing seven and injuring thirty five. The most successful Zeppelin raid on London in the entire war was on the 8th of September 1915. This raid caused more than half a million pounds of damage, almost all of it from the one Zeppelin, the L13, which managed to bomb central London. This single raid caused more than half the material damage caused by all the raids against Britain in 1915. On the night of 6-7 June 1915 Rex Warneford, a lieutenant in the RNAS, flying a Morane-Saulnier, was on a bombing mission against the Zeppelin sheds at Evere. When he spotted a Zeppelin returning from a bombing raid against London he decided to attack it. He tried shooting his carbine at it, his only armament, but he was driven off by the Zeppelin's defensive machine guns. The airship began climbing, leaving the little plane behind, but Warneford, unbeknown to the Zeppelin crew, continued the pursuit, climbing slowly over two hours to an altitude of 13,000 feet. At this stage the airship began to descend in the direction of Brussels, and seizing his opportunity Warneford, now above the Zeppelin, dived towards it and from about two hundred feet above he dropped his six bombs on its roof. The resultant explosion destroyed the Zeppelin, and almost destroyed Warneford's fragile monoplane. He was forced to put the plane down, behind enemy lines, but he managed to make sufficient emergency repairs to take off again and return to his base. LZ 37 was the first Zeppelin brought down by an airplane. Warneford was awarded the Victoria Cross by the British, and the Knight's Cross of the Legion d'Honneur by the French, but his triumph was short-lived. He was killed ten days later in a flying accident. This was an isolated incident. Throughout the remainder of 1915 the Zeppelins raided London frequently, and with impunity. They flew too high for most planes, and when they were intercepted by aircraft the ammunition in use at the time had little effect. Despite this impunity the material effect of the raids, with the exception of L13's success, was relatively slight. Navigation was very primitive, and as the war progressed the British use of blackouts made it even harder. Bomb aiming was far from accurate. It is estimated that only 10% of the bombs dropped from Zeppelins actually hit their target. The psychological impact of these raids, however, was enough to cause the British to tie up 12 squadrons on home defence. The Germans also bombed Paris. The first raid was on 21st of March, when two Zeppelins caused 23 deaths and injured 30. Although the Zeppelins continued to raid Paris, London was actually a preferred and easier target. The nearest Zeppelin base to Paris was at Metz, which meant flying close to 320 km (200 miles) over French territory each way, giving the defending airforce and anti-aircraft guns much more time to organize. Raids against London had to cover nearly twice the distance, but most of the approach was over friendly territory and the sea. Paris was also protected by barrage balloons, a measure only taken by the British later in the war. 1916 did not start well for the Zeppelins. Four of them were lost carrying out bombing raids during the Battle of Verdun, and this marked the last use of airships for tactical bombing. But Strasser remained confident. The Zeppelin factory was producing a new generation of airships - larger, more powerful, and with more engines. But it was also a year of change on the British side as well. Disappointment with the RNAS' failure to stop the Zeppelins resulted in the responsibility of home defence being given to the RFC. Happily for them this coincided with the arrival of improved amm Towards mid 1916 the British planes were armed with a mixture of explosive and incendiary bullets. This mixture would prove to be deadly to the airships: the explosive bullets could pierce the Zeppelin's tough outer skin and cause leaks on the inner gas bags. The incendiary bullets could set those leaks on fire, and once on fire a Zeppelin was doomed. William Leefe-Robinson, flying a BE2c, was the first to shoot down a dirigible over Britain, on the 2nd of September, 1916. The massive fire of the burning airship was visible for over a hundred miles. This was during a raid of twelve naval airships which were, somewhat unusually, accompanied by four army airships. Leefe-Robinson became an instant hero. He survived the war, only to die a month later in the influenza epidemic. Strasser's confidence remained unshaken. Leefe-Robinson had shot down the SL11. It was an army airships, not one of Strasser's, and moreover an old Schutte-Lanz dirigible with a wooden frame. But Strasser's confidence was misplaced. Three weeks later he was to lose two airships, out of a total of twelve taking part in a raid. There were no comforting explanations. They were naval airships. They were the most up to date Zeppelins available. The L33 had been hit by anti aircraft fire. She did not catch fire, but she was forced to land in England. The crew all survived, and set her alight before capture. The L32 was shot down by a plane, and as in the case of Leefe-Robinson's SL11, it caught fire. Nor were these the last losses in 1916. Despite flying almost four times as many sorties as in 1915, and dropping almost five times as many bombs, Strasser's fleet caused only about two thirds as much damage as they had in 1915. The German military was becoming disillusioned with the Zeppelins, and began using the new Gotha and Giant bombers to attack Britain, but Strasser remained convinced. The answer was to fly higher, above the defending aircraft. Thus was conceived the third generation of Zeppelins, the "Height Climbers", airships capable of reaching an altitude of 20,000 feet. In order to reach these heights defensive armaments were reduced, as was the strength of the frame. Flying at such altitudes produced a whole new set of problems. The extreme cold and thin oxygen affected both the engines, and the crew's capability to function. Bomb aiming and navigation became even harder. But with the renewed immunity the height seemed to offer, it seemed worth the price. Indeed, when on the night of October 19th 1917 a fleet of eleven Height-Climbers crossed the English coast they were too high to be heard, and their raid was a total surprise. But on the return journey, over the European mainland, almost half the airships were shot down by British and French fighter aircraft as they descended towards landing. The L55 had attempted to avoid this risk by keeping at 20,000 feet till it had cleared the western front, but this caused other problems. The morning sun heating the hydrogen forced the L55 to a record-breaking 24,000 feet. With most of the crew disabled by oxygen deprivation it was a struggle to bring her under almost partial control. The L55 crash landed in central Germany. The total amount of material damage caused by the airships in 1917 was less than 90,000 pounds. 1918 started badly for the beleaguered airship fleet, when a series of unexplained explosions at the airship base in Ahlhorn blew up four Height-Climbers, one Schutte-Lanz airship, and four sheds. German manufacturing by this time had been greatly reduced, and they could not replenish such losses. On the 5th of August Strasser himself led the last big raid against Britain, leading a fleet of five Height-Climbers. Strasser was flying in L70 - his most advanced airship, capable, he hoped, of flying bombing missions against New York. But by this the British had aircraft that could operate at about 20,000 feet as well, and L70 succumbed to a two maDH4 piloted by Egbert Cadbury. (He was a member ofthe famous chocolate manufacturing famil The fatal shots were fired by his gunner, Robert Leckie, whose hands were almost frozen because he had not had time to put on gloves when he and Cadbury had scrambled to chase the Zeppelins. The rest of the airships dropped their bombs on what they thought were "targets of opportunity", but in fact they dropped them in the sea. The Zeppelin attacks had a profound psychological impact on the Allies. The Germans were ordered, under the treaty of Versailles, to hand over all their airships, but their crews preferred to destroy as many of them as they could. The need to tie up numerous squadron in home defence can be marked as the Zeppelin's greatest achievement, for as a weapon of war they proved themselves unsatisfactory. Of the 115 Zeppelins employed by the Germans, 53 were destroyed and a further 24 were too damaged to be operational. Strasser's crews suffered a 40% loss rate. The cost of constructing those 115 Zeppelins was approximately five times the cost of the damage they inflicted. Article contributed by Ari Unikoski Photographs courtesy of Photos of the Great War website Zepplins After Brigadier General Ferdinand Zeppelin, a German aristocrat, retired from the German Armyin 1891 he devoted himself to to the study of aeronautics. In 1894 the German government rejected his proposals for a lighter-than-air flying machine. Although now aged sixty, Zeppelin decided to invest all his own money in a company producing airships. By 1898 Zeppelin, with a team of 30 workmen, had assembled his first airship. The main principle of Zeppelin's invention was that hydrogen-filled gas-bags were carried inside a steel skeleton. The airship, which weighed 12 tons and contained 400,000 cubic feet of hydrogen, was driven by propellers connected by two 15-hp Daimler engines. After the Zeppelin LZ made its first flight on 2nd July 1900, the German government decided to help fund the project. Ferdinand Zeppelin continued to improve his airship and in March 1909 the German Army purchased the Zeppelin Z1. By the outbreak of the First World War they owned seven of these airships. These Zeppelins could reach a maximum speed of 136 kph and reach a height of 4,250 metres. They had five machine-guns and could carry 2,000 kg (4,400 lbs) of bombs. In the early part of the war Zeppelins were used for bombing raids. A Zeppelin bombed Liege in Belgium on 6th August, 1914 but was forced to land after encountering artillery-fire. Three more Zeppelins were destroyed by ground forces over the next two weeks. Although easy to hit, the Germans continued to use them on attacks on France. In January 1915, two Zeppelin navel airships 190 metres long, flew over the east coast of England and bombed great Yarmouth and King's Lynn. The first Zeppelin raid on London took place on 31st May 1915. The raid killed 28 people and injured 60 more. Zeppelins were used at Verdun but four were brought down by ground-fire. This brought an end to their use over the Western Front, but they continued to bomb England. British fighter pilots and anti-aircraft gunners became very good at bringing down Zeppelins. A total of 115 Zeppelins were used by the German military, of which, 77 were either destroyed or so damaged they could not be used again. In June 1917 the German military stopped used Zeppelins for bombing raids over Britain and instead used them for transporting supplies. After the war Zeppelins were used for luxury passenger transport. The Graf Zeppelin, which flew round the world in twenty days, included separate passenger cabins, lounges and dining-rooms. The construction of hydrogen-filled airships with rigid keels was abandoned after several disasters including Britain's R.101, that burst into flames over France in 1930. After Brigadier General Ferdinand Zeppelin, a German aristocrat, retired from the German Armyin 1891 he devoted himself to to the study of aeronautics. In 1894 the German government rejected his proposals for a lighter-than-air flying machine. Although now aged sixty, Zeppelin decided to invest all his own money in a company producing airships. By 1898 Zeppelin, with a team of 30 workmen, had assembled his first airship. The main principle of Zeppelin's invention was that hydrogen-filled gas-bags were carried inside a steel skeleton. The airship, which weighed 12 tons and contained 400,000 cubic feet of hydrogen, was driven by propellers connected by two 15-hp Daimler engines. After the Zeppelin LZ made its first flight on 2nd July 1900, the German government decided to help fund the project. Ferdinand Zeppelin continued to improve his airship and in March 1909 the German Army purchased the Zeppelin Z1. By the outbreak of the First World War they owned seven of these airships. These Zeppelins could reach a maximum speed of 136 kph and reach a height of 4,250 metres. They had five machine-guns and could carry 2,000 kg (4,400 lbs) of bombs. In the early part of the war Zeppelins were used for bombing raids. A Zeppelin bombed Liege in Belgium on 6th August, 1914 but was forced to land after encountering artillery-fire. Three more Zeppelins were destroyed by ground forces over the next two weeks. Although easy to hit, the Germans continued to use them on attacks on France. In January 1915, two Zeppelin navel airships 190 metres long, flew over the east coast of England and bombed great Yarmouth and King's Lynn. The first Zeppelin raid on London took place on 31st May 1915. The raid killed 28 people and injured 60 more. Zeppelins were used at Verdun but four were brought down by ground-fire. This brought an end to their use over the Western Front, but they continued to bomb England. British fighter pilots and anti-aircraft gunners became very good at bringing down Zeppelins. A total of 115 Zeppelins were used by the German military, of which, 77 were either destroyed or so damaged they could not be used again. In June 1917 the German military stopped used Zeppelins for bombing raids over Britain and instead used them for transporting supplies. After the war Zeppelins were used for luxury passenger transport. The Graf Zeppelin, which flew round the world in twenty days, included separate passenger cabins, lounges and dining-rooms. The construction of hydrogen-filled airships with rigid keels was abandoned after several disasters including Britain's R.101, that burst into flames over France in 1930. Count Ferdinand Zeppelin, a German army officer, began developing his ideas on airships in 1897. The first Zeppelin flew on 2nd July 1900. The LZ-3 Zeppelin was accepted into army service in March 1909. By the start of the First World War the German Army had seven military Zeppelins. The Zeppelin developed in 1914 could reach a maximum speed of 136 kph and reach a height of 4,250 metres. The Zeppelin had five machine-guns and could carry 2,000 kg (4,400 lbs) of bombs. In January 1915, two Zeppelin navel airships 190 metres long, flew over the east coast of England and bombed great Yarmouth and King's Lynn. The first Zeppelin raid on London took place on 31st May 1915. The raid killed 28 people and injured 60 more. Many places suffered from Zeppelin raids included Gravesend, Sunderland, Edinburgh, the Midlands and the Home Counties. By the end of May 1916 at least 550 British civilians had been killed by German Zeppelin. Zeppelins could deliver successful long-range bombing attacks, but were extremely vulnerable to attack and bad weather. British fighter pilots and anti-aircraft gunners became very good at bringing down Zeppelins. A total of 115 Zeppelins were used by the German military, of which, 77 were either destroyed or so damaged they could not be used again. In June 1917 the German military stopped used Zeppelins for bombing raids over Britain. According to Col. William N. Hensley, Jr., in the New York World in 1919, the German General Staff made complete plans to bomb New York City from the air about Thanksgiving, 1918. He asserts that the L-72 was constructed for the raid. The L-72 measures 775 feet, and is equipped with six engines of 260 H. P. each. It was capable of carrying five tons of high explosives and incendiary material. Colonel Hensley adds: "Action for every hour and minute of the trip was foreseen, every possible contingency of weather, fuel exhaustion, damage to ship or machinery failure had been reckoned. Weather charts of the Atlantic were gathered, files of the German admiralty were combed and the records of the merchant marine searched. Three hundred and sixty-seven times the voyage was made on paper. The chances of real success were 367 to 1."
THE SCHUTTE-LANZ AIRSHIPS
The Schutte-Lanz airships were originally built of laminated wood girders trussed with wire stays. In appearance they were dissimilar to the Zeppelin ships in that they had streamline hulls long before the Zeppelins had them, just as they used the quadrilateral propeller drive in advance of their rivals, and originated the internal passage way. As the war progressed, however, there came a visible merging of the two designs, until finally the Schiitte-Lanz Company even gave up the most distinctive feature of its design, the wooden framework. This had first been chosen because in theory it worked out at a lesser weight than the duralumin construction and because it was more easily constructed and repaired. The wooden framework would also have an amount of springiness to take up shocks with little injury such as would gravely damage a Zeppelin.
Practical experience did not fully bear out these assumptions. It is true that after several years of effort the SchiitteLanz ships carried for the same capacity a larger useful load than the Zeppelins and that their ability to stand punishment was also greater. On the other hand the wooden framework had the serious drawback of getting out of alinement under the influence of the weather and its assembling required much more time and painstaking work than that of a Zeppelin. The want of weather-proofness of the S.L. ships explains why the German navy always looked askance at this type of construction and the manufacturers finally admitted this drawback themselves, for the S.L. 20, the last of their war series, had a framework of duralumin tubes instead of being built up of laminated wood. The experience of this firm in metal construction was too recent, however, to enable them to compete on even terms with the Zeppelin Company, which accounts for the superior performance of the latter's ships.
Parseval Non-rigid Airships
Of Germany's non-rigid airships only the Parseval types deserve special mention. Although only a limited number were built owing to the acute rubber shortage Germany experienced, the later Parseval ships were remarkable tor the large useful load they carried. They greatly exceeded in this respect their rigid contemporaries of the same size, but their speed was inferior. The most serious objection that came up against their use in warfare was the difficulty of keeping the envelope taut and so maintaining the shape of the hull when the ship was under way at high speed. This experience bears out the pre-war assumption that there is a limiting size beyond which it is not practical to build airships that depend on internal pressure for keeping their form, because the high internal pressure required demands a very heavy fabric;-which detracts from the useful load-and also because such ships are particularly liable to mishaps owing to failing pressure.
The last two Parseval airships built during the war differed from the well-known pre-war types in that a long metal girder was slung under the envelope in order better to distribute the disposable loads, such as gasoline, ballast, etc. Two wing cars were stayed to this girder amidships, while two more engine cars and a control car, forward, were suspended from it in the centerline. These large Parseval ships have thus, like the Schiitte-Lanz vessels, five separate cars, which system has the advantage of removing all noise and vibration from the control car, where the radio cabin was located.
Toward the end of the war the Parseval Company started experimenting with various aluminum alloys with a view to determining whether medium size airships could not be built more economically on the rigid principle than on the pressure system. These experiments dealt in particular with duralumin tubing, which, it is said, the company intends to use in the framework of an experimental airship.
The Gross airship, M.IV, was a pre-war product, having been built by the dissolved Balloon Battalion of the Prussian army. The ship is not particularly notable, except perhaps for the fact that it affords the only record of German experiments with mooring airships to a mast, and that it belonged to the original German semi-rigid type. This was characterized by an underslung metal girder, from which two cars were suspended, a scheme which-as we have said above-was later incorporated with several improvements in the later Parseval airships. For this reason the latter were strictly speaking semi-rigid ships and not non-rigids, as the Germans called them.
Airships all had about the same strucural efficiency, measured by empty weight/gas-volume ratio) despite differences in size, design concept, year of develment, and lifting gas. The insensitivity ttoo ss~i zze Iissa a reflection of the airship "cube-cube law" (i.e., both the lifting capability and the structural weight increase in proportion to the cube nf the principal dimension for a constant shape). Since fixed-wing heavier-than-air craft follow a "square-cube law," airships will compare more favorably with heavier-than-air craft as size is increased. Smaller airshios have tended to have nonrigid or semi-rigid construction, whereas the larger airships have been rigid, and this would be true of modern vehicles as well. In 1885 Gottlieb Daimler developed an internal combustion engine for dirigibles. Developing 2hp and boasting a single cylinder, it made a successful trial flight in August 1888. Subsequently, Daimler's attention was diverted to developing internal combustion engines for the early automobile; further refining of the internal combustion engine for dirigibles was carried on by Dr Karl Woelfert, who flew an airship powered by a two-cylinder, 6hp engine at the 1896 Berlin Trade Fair. This performance was witnessed by Kaiser WiIhelm II, who offered Woelfert facilities to continue development. The German interest in airships dates from this time. German airship development proceeded under the visionary leadership of the legendary Graf (Count) Ferdinand von Zeppel in. He successfully tied airship development to German national pride, obtaining the Kaiser's support and the German press' enthusiastic backing. Commencing with the launching of his first airship, the Luftschiff Zeppel in No 1 (LZ1) in July 1900, German airship development grew apace. The LZ1 was 420 feet long, 38.5 feet in diameter, and capable of 20 mph. By 1908 German airship enthusiasm had grown such that von Zeppel in and his partner, Hugo Eckener, founded Deutsche Luftschiffahrts Aktien Gesellschaft (DELAG), which operated a fleet of five airships from dirigible airports all over Germany. By the eve of World War I in August 1914, DELAG had made more than 1600 passenger flights, logging over 100,000 mi les and carrying over 10,000 passengers. Thanks largely to von Zeppel in and DELAG, Germany was the best-prepared belligerent at the start of the war with respect to airships. By requisitioning the DELAG airships, the German Army and Navy fielded a total of nine dirigibles. Germany placed a great deal of reliance on her Zeppelins. Those huge dirigibles, capable of lifting a useful load of thirty-eight tons and of traveling at the rate of seventy miles per hour, seemed ideally suited to carry German frightfulness into the very home of the Briton. But they were afraid - these great airships - afraid of the little battleplanes that attacked them. The airplanes traveled so fast and dodged so quickly that the Zeppelin's guns could not find them. They would mount above the airship where the huge gas-bag hid them from the gunners. Even when guns were mounted on top of the balloon, the Germans had reason for dread because the battle-planes fired incendiary bullets, and it needed but one of these to penetrate the skin of the Zeppelin and set fire to the hydrogen gas it contained. The Zeppelin commander's position was about as enviable as would be that of a naval commander who went forth to war in a boat molded out of TNT. He was afloat under two million cubic feet of highly inflammable gas. which needed but to be mixed with a suitable quantity of air to become a powerful explosive. By 1912, the Germans were touting the zeppelin as a bomber, although French aviators derogatorily referred to it as a "soap bubble" that they obviously planned to pop in a future war. Fred Jane wrote in his "Fighting Airships" (1913) : "A single aeroplane should be able to disable or destroy without very great difficulty the finest dirigible yet built (supposing it able to find the airship in the vastness of the air)." In the case of zeppelins, these costly monsters were quickly removed from combat over the western front, first from daylight sorties, then sorties on moonlit nights, and ultimately altogether, as they made irresistible targets for gunners. They thereby fulfilled the unheeded prewar warning of German ballistics expert General Rohne that dirigibles would be vulnerable to incendiary shells. The zeppelins continued to serve successfully as scouts for the German navy, and then they were launched against Britain in the first strategic air raids of the war. They ultimately failed in the strategic assault as aircraft and antiaircraft defenses drove them so high that they became vulnerable to galeforce winds that would blow returning dirigibles all over the European continent and occasionally further. Luftschiff Zeppelin 59 In 1917 a German aircraft departed Bulgaria on a 3,600 nautical-mile flight carrying 30,000 pounds of medical supplies and ammunition for a beleaguered army unit in Africa. When it landed 95 hours later it still had 64 hours of fuel remaining- enough to have flown to San Francisco had it taken a great circle route west instead of flying south. Nonstop flights from Bulgaria to San Francisco carrying that large a payload could not have been accomplished by a B-29 thirty years later. In 1917, it was closer to the realm of science fiction. What type of aircraft was this and how was it possible in 1917? It was the German Luftschiff Zeppelin 59 (LZ 59), a rigid airship. During the flight most of the weight of the ship was held aloft by buoyant lift, the difference in weight between the air displaced by its gas envelope and the hydrogen contained within. As a result, all the engines of the Zeppelin had to do was overcome the drag of the vessel as it passed through the air. The engines on a conventional aircraft must do that as well, but must also overcome the additional drag from the wings lifting the weight of the aircraft. LZ-127 Graf Zeppelin In August 1929, the German airship Graf Zeppelin flew around the world in four stops carrying twenty passengers and forty-one crew. The longest leg was a nonstop flight between Friedrichshafen, Germany and Tokyo, a distance of over 7,000 miles covered in 100 hours. Not only was a flight like this unthinkable by an airplane in 1929, the passengers made the flight in accommodations unavailable to the commercial air traveler even today. The spacious dining room of the Graf Zeppelin makes another point about airships. Because the gas envelope is necessarily many times larger than the fuselage of an airplane of comparable gross weight, they tend to have much more volume available for passengers and cargo. It is much more difficult to bulk-out an airship than an aircraft. The vehicle is lifted by the buoyancy of the lifting gas and all the engines must do is overcome parasitic drag to move the vehicle through the air. This explains the remarkable performance of airships such as the LZ 59 and Graf Zeppelin given the limited performance of the internal combustion engines available at the time. The engines only had to move the airship, not lift it, and since the airships were relatively slow even the parasitic drag component was small. The culmination of Zeppelin development was the Graf Zeppelin and Hindenburg airships, unquestionably outstandinq engineering achievements for their day. The early airships were designed primarily by empirical methods, and the only company to accumulate sufficient experience to design successful rigid airships was the Zeppelin Company. Two areas in which there was a serious lack of knowledge were aerodynamic loads and design criteria. But it is generally acknowledged today that past conventional, fully buoyant airship designs were very nearly optimum for this class of vehicle in terms of aerodynamic shape and fineness ratio. The frames of most of the past rigid airships consisted of built-up rings and longitudinal girders stabilized with wire bracing. The rings and longitudinals were typically made of aluminum alloy and the bracing was steel. This structure was very light and efficient, even by present standards. However, this construction was highly complex and labor intensive. The operation of the 1930's airships was as labor intensive as their construction. Control operations of the 1930s are best grasped by appraising the crew sizes. The rigids had very large crews. The Graf Zeppelin had a crew of 44, the Hindenburg 38. Likewise, military rigids had large crews: the USS Akron had 76 crewmen, the 51 USS Shenandoah 43, the USS Los Angeles 45, and the USS Macon 76. The reason for such large crews was the lack of sophisticated flight support systems. In flight large onboard crews were required to constantly monitor and adjust the trim of the ship and maintain nearly neutral buoyancy. Trim and neutral buoyancy were maintained by one or more of the following procedures: valving lifting gas, dropping ballast, transferring fuel or other materials within the airship, collecting water from the atmosphere and engine exhaust, and moving crew members within the airship. Also, it was not unusual to repair the structure and the engines in flight. Engine controls of the rigid airships consisted of an engine telegraph that transmitted engine control commands from the helmsman to an engine mechanic, who would then manually make the required engine control changes. 1931 attempt by Sir Hubert Wilkins to be the first to cross the Arctic Ocean in a submarine (the Nautilus) by way of the North Pole and rendezvous there with the famous German airship Graf Zeppelin. The only significant past commercial airship operations were those of the Zeppelin Company and its subsidiary DELAG. None of these commercial operations can be considered a financial success and most were heavily subsidized by the German government. For example, the transatlantic service with the Graf Zeppelin in 1933-1937 required a break-even load factor of 93-98%, a value seldom achieved, despite carrying postage at rates over ten times higher than 1975 air mail rates. Throughout most of these commercial operations, there was little or no competition from heavier-than-air craft. However, airplane technology was making rapid strides and airplane speed, range, and productivity were rising steadily. Airships and airplanes are difficult to compare because of the remoteness of the time period and the limited operational experience. By the time of the Hindenburg disaster in 1937, it seems clear that the most advanced airplane, the DC-3, had lower operating costs as well as higher cruising speeds than the most advanced airship, the Hindenburg. Of course this tended to be offset by the Hindenburg's luxury and longer range. Nevertheless, it is clear that although the burning of the Hindenburg hastened the end of the commercial airship era, it was not the primary cause; the airship had become economically uncompetitive. Germany built and flew the Graf Zeppelin around the world. The Germans then built an even larger airship, the Hindenburg. After a successful season on the North Atlantic run, it went up in flames over Lakehurst, New Jersey, in 1937. That disaster was a turning point. The Graf Zeppelin was removed from commercial service. While German airships were successful on the Atlantic crossing, airship disasters and the appearance of fast, long-range American flying boats such as the Boeing Clipper meant their days were numbered. Germany built one last ship, the Graf Zeppelin II, a sister to the Hindenburg. Its designers hoped America would relent and allow the export of helium. When relations with the United States worsened, any possibility of reviving commercial airships vanished. In the summer of 1939, however, Germany discovered another mission for the technology, electronic warfare. Flying along the North Sea coast of England, the airship searched for emissions from British radar home chain stations. But its receivers were tuned to the wrong frequency and found nothing. The project was abandoned. The Graf Zeppelin, launched in September, 1928, had five 530hp Maybach engines, an unrefuelled range of 6250 miles, cruised at 70mph, and carried 64 people. The Hindenburg, launched seven years later (March, 1936) had four 1050hp Daimler-Diesel engines, a top speed of 81mph, a similar range to the Graf Zeppel in, and carried 100 people. the Hindenburg, was launched in 1936. The giant of the species, she was over 800 feet long, 135 feet in diameter, and had a maximum speed of 81mph. Like her sister ship, the Graf Zeppel in, she was a flying hotel, with a lounge, dining salon, accommodations for 72 passengers, a smoking room and bar, and even boasted an aluminum grand piano. Fourteen months after her maiden voyage, she exploded over Lakehurst, New Jersey, while docking. The circumstances were suspicious, leading to theories its destruction may have been politically motivated rather than due to any fundamental unsoundness in her construction. Of the 97 people aboard, 62 survived; of the 35 fatalities, 23 were crewmen. The 12 passengers who died on the Hindenburg were the only fare-paying 16 passengers ever to die in an airship accident. laid the keel for the Graf Zeppel in 1926. Called the "most beautiful airship of them all", she was 775 feet long, 100 feet in diameter, developed a speed of 70mph, and had a 6,250 mile unrefuelled range. She carried a crew of 44, with accommodations for 20 passengers, and had a dining room and saloon. Launched. in September, 1928, she made over 650 flights, 144 of them across the North and South Atlantic, logged over a million miles, and carried more than 18,000 passengers. A typical east-west crossing from Friedrichshafen to Lakehurst took about 79 hours, with a return journey averaging about 60 hours due to favorable winds. In 1929, she circumnavigated the globe, traveling 31,000 mi les in 21 days, 12 hours. In 1931 she undertook an aerial survey of the Arctic, carrying out several maritime stopovers in the process. She was retired from service in 1937. The conception of the Graf Zeppelin's Arctic cruise of 1931 dated to 1926 and the foundation of the Aeroarctic Society. In its first form the plan was for a crossing of the Arctic from the European to the American side under the leadership of Nansen. The plan failed to mature, largely on account of the extremely high rates of insurance expected for a dirigible navigating so far north. Nansen's sudden death in 1930 brought a further postponement until the election of Dr. Hugo Eckener to the presidency of Aeroarctic later in the same year.
At 8.35 a.m., the morning of July 24, the monstrous bulk of the Graf Zeppelin began to move slowly out of its Friedrichshafen hangar; and a few minutes later we were headed northward towards Berlin, on a course northward for Helsingfors, thence east for Leningrad. The Arctic Circle was crossed at 7 p.m on July 26. The wind, which had been light from the northeast all day, suddenly shifted to east-northeast and increased to a fresh breeze almost coincident with reaching the Arctic Sea. As the dirigible progressed farther north, the thermometer dropped to 2" C., and the ship gradually emerged into clear atmosphere and bright sunshine. The Graf Zeppelin stopped at Templehof field for a half hour, then left for Friedrichshafen, the final destination, which was reached at 5 a. m., July 31, 1931.
One of the most important contributions of the Graf Zeppelin expedition was the correction of existing maps. The subject of photogrammatic survey in Franz Josef Land was, particularly, Alexandra Land and a portion of Prince George Land. In Novaya Zemlya the northern and southern limits of the inland ice were photographed with the mapping cameras, as also were unrecorded mountain peaks that protrude through the ice along the meridional ridge of the island in its northern part.
The Graf Zeppelin expedition, unlike all other aircraft explorations of the Arctic, was made during midsummer, a season usually attended with much fog and low visibility. However, it seemed that given certain winds and pressure conditions this handicap could be avoided. It was designated as a preliminary cruise to a longer flight to take place either in the summer of 1932 or 1933. The U.S. Coast Guard, with its International Ice Patrol researches, was for one much interested in these airship investigations in the Arctic. It hoped to see a successful flight along the iceberg-glacier fronts of Baffin Bay and to realize a camera study of the iceberg distribution in West Greenland waters.
"http://www.uscg.mil/history/articles/GeographicalReviewArticle1932.pdf">Report of the Preliminary Results of the Aeroarctic Expedition with "Graf Zeppelin," 1931 Lincoln Ellsworth; Edward H. Smith Geographical Review, Vol. 22, No. 1. (Jan., 1932), pp. 61-82. H.G. Wells wrote The War in the Air in 1907, which featured German drakenships that attacked the U.S. Navy and pulverized cities from the sky. The zeppelin Hindenburg was destroyed while landing at Lakehurst Naval Air Station in New Jersey May 6, 1937. Of 61 crew and 36 passengers, 22 crew and 13 passengers died in the explosion along with a ground crewman, Navy Linesman Allen Hagaman. Longer than three Boeing 747s, the Hindenburg and her sister-ship, Graf Zeppelin II, were the two largest aircraft ever built - 804 feet long and 135 feet in diameter. They had cabins for 50 passengers (upgraded to 72 in 1937) and a crew of 61. The Hindenburg was designed to be filled with helium, but a U.S. embargo forced the Germans to use highly flammable hydrogen. The popular perception is that the Hindenburg was destroyed on its maiden voyage. Unlike the Titanic, the zeppelin had flown for over a year before the disaster. In 1936 the Hindenburg flew 191,583 miles carrying 2,798 passengers and 160 tons of freight and mail. In that year the ship made 17 trans-Atlantic flights with 10 to the United States and seven to Brazil. It also made a record-breaking Atlantic double-crossing in five days, 19 hours and 51 minutes. "Oh, the humanity," cried a radio announcer on May 6, 1937, as the German airship, the Hindenburg, exploded in flames while landing outside New York City. For many people this is all they know of airships - that category of "lighter than air" craft which includes dirigibles and blimps. For a few years in the late 1930s airships flew passengers around the world in luxury, and some aviation experts speculated they would be the future of worldwide passenger aviation. With the Hindenburg disaster covered widely by radio and newsreels, and the improvement of long-range airplanes, the airship's days were numbered.
LZ-129 Hindenburg
The age of the airship ended on 6 May 1937, the day of the Hindenburg disaster. The gaseous explosion of Germany's greatest zeppelin killed 36 people-of whom 13 were passengers; the only passengers ever lost in 20 years of commercial travel by airship-and the tragedy became one of the greatest news events of its time. Stark public memory of the big dirigible going down in flames at its mooring at Lakehurst, New Jersey, and of the extraordinarily emotional live reporting of an eyewitness radio announcer, guaranteed the death of LTA flight as the losses of the Roma, Shenandoah, Akron, and Macon had not. The Hindenburg was just one of a number of hydrogen airships that met with an accident involving the hydrogen lift gas. Of 129 hydrogen airships in the early 1900's, over one-third met with that type of accident. The most well known accident event with a hydrogen dirigible was the Hindenburg disaster. Until that time, commercial German airships had a flawless safety record. The Graf Zeppelin airship alone had flown around the world, and had logged over a million passenger miles with no injuries to passengers. This value is perhaps small by today's standards, but in that era most dirigibles carried on the order of 50 passengers, so the value did represent many airship miles flown. The Hindenburg, airship LZ-129, was the largest airship ever built, at 135 feet in diameter, and 803 feet long. It held over 7 million cubic feet of hydrogen in sixteen gas cells (Toland, 1972). Sixteen compartments each contained a gas cell made from a cotton fabric, then a hydrogen impermeable layer of rubberized 'film', then another cotton fabric layer. Hydrogen gas pressure in each cell was on the order of 0.5 to 1 inch of water gauge (124.3 to 248.6 Pa above atmospheric pressure). The diffusion rate was about 1 liter of hydrogen per square meter of gas cell fabric per 24 hours. The airship outer skin was a linen fabric that was then coated with cellon 'dope' and aluminum powder mixture for weather protection. The outer fabric skin protected the gas cells and made the airship more aerodynamic. The dope (i.e., varnish) was used to waterproof and tauten the fabric cover. For ultra violet light protection, the inner surface of the fabric on the upper part of the airship was coated with red paint. The frame was built with aluminum-copper alloy girders. Girder rings were connected by straight section girders to form the characteristic ellipsoid shape. Wire cables were used to provide internal support for each ring. The gas cells were located between each girder ring. The frames of the Hindenburg were numbered in meters from the aft forward; frame 2 was near the tail and frame 247.1 was at the nose. The Hindenburg was originally designed for helium usage, but Germany was unable to purchase helium from the US. The US had passed a Helium Control Act in 1927. The helium supply was small and the US government did not believe that the new German government at that time had strictly peaceful intentions (Schlager, 1994). The Zeppelin Transport Company of Germany was forced to use hydrogen to fill the dirigible. The ship was fitted with precautions for hydrogen use. All crew ladders and catwalks were rubber encased to eliminate possible sparking, crew uniforms for use when inspecting the gas cells and ship's structure were made from asbestos without any metal (no metal fasteners, buttons, zippers, snaps, tabs, etc.) to eliminate static electricity generation and discharge. The crew shoes were either sneakers or felt boots to preclude static buildup. The axial passageway along the length of the airship and vertical shafts between gas cells were well ventilated, including use of natural draft air movement. Passengers were allowed to smoke tobacco, but only in designated smoking rooms that were under positive air pressure to ensure no hydrogen admission. Crew members helped passengers light their smoking products, and no passengers were allowed to possess matches or lighters during their voyage. Gas pressure sensors indicated pressure in each gas cell to the control car. The sensor elements were diaphragm pressure onto a spring loaded plunger within a wire coil (24 VDC, 100 ohms). A cell could lose only about 200 to 300 cubic meters of gas before the sensor readout would show a problem; this is only a very small portion of cell volume (a cell was about 12,500 cubic meters) (Knight, 1937). The Hindenburg performed well, making thirty-four Atlantic crossings to Lakehurst, New Jersey and Rio de Janiero, Brazil in 1936 at an average crossing time of two and three days, respectively. The ship weathered storms well; passengers did not generally know how severe the weather was and they did not suffer from motion sickness because the airship had good stability in rough weather (Toland, 1972). On May 6, 1937, the Hindenburg was due at Lakehurst, New Jersey at 6:00 am, having departed Frankfurt Germany two days earlier. Wind and rainy weather slowed the airship, it diverted around the worst of the storm. The Hindenburg passed New York City at 3 pm. The airship hovered along the coast to wait out a thunderstorm and allow for ground preparations. Because of the size of ground crew needed, only two times were scheduled to receive airships, 7 am and 7 pm (Toland, 1972). The airship approached the landing field at 6:00 pm, maneuvered to dock. Part of the docking procedure was to vent hydrogen and ballast as needed to steady the craft at the docking mast altitude and maintain gas cell pressure for differing barometric pressures at changing altitudes. The Hindenburg vented hydrogen from the five forward gas cells twice for 15 seconds while still decelerating from 73 to 27 mph, and decreasing from about 590 feet to 393 feet altitude. Hydrogen was vented once for 5 seconds while traveling at about 27 mph on approach to the landing field. There was a 6 knot variable wind from the east. The airship then dropped a total of about 2,425 pounds of water ballast from frame 77 to trim the ship in preparation to dock (Knight, 1937). The airship passed through a small rain 38 shower and a light rain was falling; the airship had successfully maneuvered around the heart of the thunderstorm. Spectators on the ground noted that the ship appeared to be slightly tail heavy as it approached. Then six members of the airship crew were sent to the bow to use their body weight as a means to help trim the craft even after the water ballast had been dropped. Crew movement for trim was an uncommon, but not unknown, practice for a large zeppelin. The airship captain noted some light rain and that there was a distant storm with lightning activity to the south and southwest. The sun had not set, so there was ample light for docking. As the ship approached the docking mast, it performed a sharp turn (varying testimony about how sharp the turn was) to face into the wind, which was shifting. Some ground crew noted that when Dr. Eckener piloted airships, he brought them in straight into the wind, slowed and "stopped on a dime". This captain performed a spectacular high speed, low altitude pass over the crowd of spectators and then a sharp turn to line up with the docking mast (Toland, 1972). The engines were run at full speed astern for about a minute to slow the airship. Then, with the Hindenburg about 200 feet above the ground, two 2-inch diameter manila rope lines from frame 244.5 (i.e., near the bow) were dropped to begin securing the airship. Dust came from the lines as they dropped to the ground, but the lines wetted in the light rain. The procedure was that a steel cable would moor the airship nose to the docking mast, and the manila ropes hold the airship into the wind and also prevent it from over-riding the mast. Only the port line had been attached to a ground winch used for drawing the airship down to ground level for disembarking passengers and cargo. The starboard line was being handled by ground crew at the time of the fire (Knight, 1937). The nose cable had been lowered about 50 feet but was not connected to the docking mast when the fire began. The airship never got closer than 700 feet (horizontal) to the docking mast. Ground crew saw the outer cover at the tail of the airship fluttering, and the skin of the airship seemed to be rippling. Since the propeller slipstream was far below that area, the ship had little headway, and the wind was light, the only reasonable explanation for the cover flutter is that hydrogen was leaking from a gas cell and causing the cover to move. At 6:25 pm, just after the port line had grown taut, a small tongue of flame emerged from where the skin had been fluttering. Ground crew then noted a red glow. Seconds later, burning hydrogen burst from the top of the airship. Photographs and witness testimony allowed investigators to conclude that the fire did start at the top of the craft, near gas cells 4 and 5. The fire spread down the rear sides of the craft. The stern of the craft was engulfed in flame and began dropping. As the airship bow began pointing skyward, hydrogen flames shot up through the bow "like a blowtorch". The entire craft was afire and the frame collapsed. About 32 seconds had elapsed from the time the ground crew noted the red glow until the ship lay smoldering on the ground. Secondary fires, mainly of diesel fuel used for the propeller engines, burned for another three hours. The combustion was a rapidly burning fire, not a deflagration explosion. Post-accident photographs show that the docking mast was intact, and the few injuries to the nearby ground crew and spectators show that it was not an overpressure event, only a fire. While the flames "shot up through the bow like a blowtorch", this is to be expected when a fire 39 is introduced on a slope, since the flame radiant heating more easily preheats combustible materials (the hydrogen and the fabric) on a slope. Pre-heating combustible materials allows faster flame spread, and flame upward buoyancy would also allow easy propagation into unburned material. As the Hindenburg continued to settle by the stern, the slope continued increasing, allowing faster and faster flame spread. As shown in Chapter 2, hydrogen does not radiate as much heat as other materials, but the Hindenburg cover fabric and gas cell materials were also burning, which contributed to pre-heating the unreacted hydrogen. Fortunately, Captain Pruss allowed the airship to settle. The first instinct was to release ballast to trim the craft. Had he done so, the airship would have remained at too high an altitude and more lives would have been lost. There was some speculation that the Hindenburg was sabotaged but there is no conclusive proof that any sabotage occurred. The German investigation of the accident concluded that, while definitive causes could not be found, the most probable cause was that a leak developed in gas cell 4 or 5, possibly caused by a failed support wire inside the airship, possibly due to the sharp turn during landing. Sometimes support wires did fail, but they usually did not cause any leaks. The wreckage was too damaged to determine anything about the hull internal support wires. The leak caused a flammable hydrogen-air mixture to form in the upper part of the ship's stern. The gas mixture was ignited either by (a) a brush discharge after the ship was electrically grounded or (b) the airship frame grounded quickly through the port manila line but the wet outer fabric cover did not ground as quickly, allowing a voltage potential difference to develop and create a spark between the fabric and the aluminum alloy frame. The German investigators, including Dr. Eckener, favored scenario (b). The American investigation included witness testimonies and photographic coverage of the accident, as well as investigation of the remains on the field. One witness from the port bow landing party of the ground crew discussed the flutter he saw in the fabric on the top port side of the airship. The German airship design and operations expert (and member of the German investigation team), Dr. Hugo Eckener, stated that a leak of hydrogen on the order of 40 to 50 cubic meters per second could cause the sort of fabric flutter described by the witness. He also stated that this leakage rate would not immediately be noticed on instruments in the control car. US investigators constructed an airship master diagram and marked eyewitness locations of fire origin. From that diagram the investigators concluded that the first open flame was on the top of the ship forward of the entering edge of the vertical fin over gas cells 4 and 5. The investigators believe that there was no detonation explosion after the fire began, just a very rapid burning of the hydrogen as it escaped from the gas cells. The investigators determined that the gas cell was not damaged by a propeller blade fragment; the propellers were recovered from the wreckage and shown to be intact when the craft impacted the ground. A plausible cause for the leakage was the fracture of a shear wire in the airship hull; a wire might have snapped during the last sharp turn to line the airship nose up with the mast and face into the wind. Possible gas combustion ignitors were discussed, including 40 the pressure sensor, outgoing radio transmissions (transmissions ended 15 minutes before docking), mechanical friction heat from the airship structure, chemical reactions, electrical energy, and drive engine exhaust. Electrostatic energy seemed the most promising cause. Tests on the manila (hemp) rope showed that for conditions existing at the time of the accident, the airship could electrically discharge by 90% in a period of 0.6 to 170 seconds of the rope contacting the ground. A theory was advanced that a brush discharge from the airship fabric to the grounded part of the airship occurred because of the voltage potential gradients that existed at the field after thunderstorm passage. A brush discharge was proven to be able to ignite hydrogen in tests, and this discharge could not be seen in daylight. The American investigation concluded that a leak in the vicinity of gas cell 4 or 5 formed a combustible mixture, and it was probable that a brush discharge ignited the mixture. The Hindenburg accident claimed the lives of 13 of the thirty-six passengers, 22 of the sixty-one crew members, and 1 ground crewman. While more people perished in the R- 38 and R-101 accidents, the public outcry was worse with the Hindenburg disaster. In the aftermath of the Hindenburg fire, all airships were grounded, and commercial airship travel ended later in May 1937 because of the perception on the part of companies and passengers that it was too dangerous (Schlager, 1994). Germany grounded the Graf Zeppelin, but also did construct the D-LZ130 airship in 1938. Again, the US did not supply helium for airship use, and the D-LZ130 used hydrogen. The D-LZ-130 was named the Graf Zeppelin, but it never flew passengers. After a few trial flights, the DLZ- 130 was disassembled for parts in 1940 as Germany was involved in World War II. By 1939, the first airplane carried a paying passenger across the Atlantic, although transatlantic travel was not routine until after World War II. Despite the fact that nearly two-thirds of the people aboard survived the Hindenburg airship fire, the name Hindenburg came to mean any sudden, tragic technological disaster (Schlager, 1994). The Hindenburg did not explode, even though the average person believes that it did. As stated earlier, this was a severe flash fire, not an explosion. If the Hindenburg had exploded, then the loss of life would have been much greater than actually occurred. Certainly the crew and passengers would have perished in the air. The ground crew would have suffered more than one fatality (wreckage did fall on one man) from the blast heat, overpressure, and debris missiles when 7 million cubic feet of hydrogen exploded. Spectators at the landing field would have had injuries and fatalities from the blast overpressure and heat exposure. While the Hindenburg was not the largest loss-of-life accident with an airship, it is the most memorable. Some reasons for this are the motion picture camera footage, the live radio broadcast, and the sensitivity of a foreign flag vessel having a catastrophic accident at a US port during a time of failing political relations with the country. http://books.google.com/books?id=8xNLAAAAYAAJ&pg=PA1576&dq=LZ125++airship&lr=&as_brr=4&cd=4#v=onepage&q&f=false http://books.google.com/books?id=8xNLAAAAYAAJ&pg=PA1576&dq=airship+LZ102&lr=&as_brr=4&output=text#c_top http://planearts.com/product.php?product=180
http://books.google.com/books?id=iUdFAAAAYAAJ&pg=PA726&dq=Ehrhardt+cannon&lr=&as_brr=4&cd=32#v=onepage&q=Ehrhardt%20cannon&f=false http://books.google.com/books?id=qU5LAAAAMAAJ&pg=PA65&dq=types+zeppelin&lr=&as_brr=4&cd=16#v=onepage&q=types%20zeppelin&f=false http://www.zeppelinfan.de/index_e.htm LZ-1: Length 128m (420'), Diameter 11.7m (38.5') LZ-4: Length 136m (446'), Diameter 13m (42.5') LZ-1 carried 11,300m3 of gas, while LZ-4 carried 15,000m3 http://www.airships.net/zeppelins http://www.pugetairship.org/zeppelins/list_2.html 1 cubic meter = 35.3146667 cubic feet 22,500 m³ = 800,000 ft³ Bodensee 50,000 m³ = 1,800,000 ft³ 60,000 m³ = 2,100,000 ft³ 100,000 m³ = 3,500,000 ft³ 135,000 m³ = 4,767,000 ft³ 22,500 m³ = 426 ft Bodensee 50,000 m³ = 520 ft 60,000 m³ = 545 ft 100,000 m³ = 620 ft 135,000 m³ = 666 ft http://books.google.com/books?id=8xNLAAAAYAAJ&pg=PA1576&dq=LZ125++airship&lr=&as_brr=4&cd=4#v=onepage&q&f=false http://www.pugetairship.org/zeppelins/list_1.html The "Bodensee" was 426.4 feet (130 meters) long, after she had been lengthened by 32.8 feet (10 meters). Her diameter was 61.3 feet (18.7 meters) and she carried 794,475 cubic feet (22,500 cubic meters) of hydrogen. Her useful load normally was 25,353 pounds (11,500 kilograms). Her four motors were of 260 horsepower each. They turned three direct-driven propellers, one in each of the port and starboard motor gondolas which hung from the sides of the ship. The third propeller was driven by two engines in the rear motor gondola. The propellers averaged from 1,300 to 1,400 revolutions a minute. The "Bodensee" was capable of making 80 miles an hour. Her cruising speed was 75 miles an hour. L16 = LZ50 L30 = LZ62 L49 = LZ96 L57 = LZ102 L59 = LZ104 L71 = LZ113 L71 = LZ114 Airship Envelope Design Volume(cu. ft.) UsefulLift(lbs.) Graf Zeppelin (LZ127) 3,700,000 62,300 34% Hindenburg (LZ129) 7,063,000 115,000 33% Graf Zeppelin II (LZ130) 7,063,000 127,000 36% LZ131 (proposed) 7,994,750 181,000 http://spot.colorado.edu/~dziadeck/zeppelin.html The Zeppelin Works evolved about that time the design of the LZ-125 class to be of about 3,500,000 cu. ft. capacity and nearly 800 feet long. This is the maximum size that could be built in the Friedrichshafen sheds. Except for size the design was similar to earlier ships. In spite of assertions to the contrary, work was never started on one of these large ships and the design appears to have been altered so as to be classed as a commercial ship and, as such, has been rather extensively advertised. The LZ129 and the LZ130 were the largest flying object ever built. The planned LZ131 and LZ132 would have been even bigger. After the German invasion of Poland started the Second World War on 1 September, the Luftwaffe ordered the LZ127 and L130 moved to a large Zeppelin hangar in Frankfurt, where the skeleton of LZ131 was also located. In March 1940 Göring ordered the destruction of the remaining vessels and the aluminum parts were fed into the German war industry. In May of that year a fire broke out in the Zeppelin facility which destroyed most of the remaining parts. The rest of the parts and materials were soon scrapped with almost no trace of the German 'giants of the air' remaining by the end of the year. The deadweight of the LZ129 was, by some accounts, about 118 tons, leaving 143,000 lbs. (72 tons) of its 380,000 lbs. of Hydrogen dead-lift to go towards cargo lift. As the LZ130 approached completion, weight-saving design changes relative to the LZ129 had been incorporated (structural hull changes, radiators & piping, electricalsystem, and in particular, a reduction in the scale of the passenger quarters), such that the LZ130 weighed 12,000 lbs less than the LZ129. Although never built, the specifications of the LZ131 were well-documented. It would have used the basic LZ129 design with an additional hull section, bringing the envelope volume to just under 8 million cubic feet. Of particular interest, this airship, with a 13% greater hull volume than the LZ129, would have weighed about 10 tons less than the Hindenburg. These weight savings would, in large part, have come through a new structural material, resembling American Alclad, which after heat treating, would have 25% better strength in compression. http://books.google.com/books?id=aCAfAAAAMAAJ&pg=PA198&dq=types+zeppelin&lr=&as_brr=4&cd=19#v=onepage&q=types%20zeppelin&f=false http://books.google.com/books?id=RLYqAAAAYAAJ&pg=PA410&dq=types+zeppelin&lr=&as_brr=4&cd=38#v=onepage&q=types%20zeppelin&f=false Miscellaneous inflation possibilities undoubtedly existed in the prospect of new gases to be discovered or in the utilization of ones now known but not employed, but whatever the advantages thus left to be secured it is certain that among them there will not be any material increase in lifting capacity, since hydrogen already affords nearly 44 of all the lift there is to be had, this factor being limited, as has been previously emphasized, not by the lightness of gases, but by the weight of air displaced. However, should helium, which is almost as light as hydrogen (11 units of lifting capacity against 12 with hydrogen), ever be commercially produced in quantity it is possible that it would be of advantage to use it because of its chemical inertness, which in general as well as military uses certainly would contrast favorably with the dangerous inflammability of hydrogen. By 1911, practically all the isolated helium in the world is the quantity of about 14£ cubic feet in the possession of the University of Leyden. Ammonia gas, which is almost as light as some illuminating gases -.04758 pound to the cubic foot-might appear to have some possible application to the inflation of balloons designed to be proof against incendiary projectiles. Its cost, difficulty of preparation with present portable facilities, its extremely irritating effect when respired, even in very small quantities, and its deleterious action on envelope coatings, are among the greatest objections to it. http://www.airshipmodeler.com/forums/index.php?s=165839e6f71e17f0fd7800e80dcce316
| L.Z. | Airship |
Length (ft.) |
Diameter (ft.) |
Capacity (cub.yads.) |
Lift (lbs.) |
Engines (H.P.) |
Air Speed (ft.per sec) |
ft. |
Notes | |
| 1 | L.3( L.7) | 518 | 48 | 29,430 | 19,180 | 3 | 210 | 69 | 6,560 | |
| L.Z.38 | L.10 | 536 | 61 | 41,725 | 34,390 | 4 | 210 | 85 | 9,185 | |
| L.Z.97 | L.20 | 585-1/2 | 61 | 46,825 | 39,240 | 4 | 240 | 84 | 10,500 | |
| 4 | L.30 | 643 | 78 | 71,940 | 62,830 | 6 | 240 | 88 | 12,470 | |
| 5 | L.60 | 643 | 78 | 73,050 | 87,300 | 5 | 240 | 100 | 19,680 | |
| 6 | L.71 | 743 | 78 | 89,595 | 112,435 | 6 | 260 | 111 | 21,650 | |
| 7 | L.100 | 781 | 96 | 141,260 | 180,780 | 10 | 260 | 121 | 30,180 | (Planned) |
Airship |
Length (ft.) |
Diameter (ft.) |
Capacity (cub.yads.) |
Lift (lbs.) |
Engines (H.P.) |
Air Speed (ft.per sec) |
ft. |
||
| 8 | S.L.3 | 513 | 64 | 42,375 | 29,100 | 4 | 210 | 74 | 7,870 |
| 9 | S.L.6 (S.L.7) | 534 | 64 | 45,780 | 34,835 | 4 | 210 | 85 | 8,530 |
| 10 | S.L.8 (S.L.10) | 571 | 65 | 50,615 | 42,990 | 4 | 240 | 85 | 11,485 |
| 11 | S.L.20 | 651 | 74 | 73,245 | 77,825 | 5 | 240 | 93 | 16,405 |
| 12 | P.L.19 | 302 | 51 | 13,080 | 7,275 | 2 | 180 | 71 | 8,200 |
| 13 | P.L.25 | 369 | 52 | 18,440 | 13,230 | 2 | 210 | 72 | 9,840 |
| 14 | P.L.27 | 515 | 60 | 40,740 | 39,685 | 4 | 240 | 82 | 14,765 |
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