Читать книгу Sky Ships - William Althoff - Страница 10

Introduction

Lighter-than-air (LTA) craft are mankind’s oldest aircraft. In 1783, the first air passenger was carried aloft in a French balloon—more than a century before the Wright brothers’ heavier-than-air (HTA) machine. The new science of ballooning evolved slowly during the next hundred years. But the invention of reliable, lightweight engines transformed aeronautics. By the early 1900s, experimental power-driven balloons, or dirigibles, were being flown successfully by a host of pioneers in a number of countries.

The stimulus for the United States Navy’s lighter-than-air program dates to the early 1900s and to Germany. The first Zeppelin airship (LZ-1) made its maiden flight in 1900. In 1909, Count Ferdinand von Zeppelin, inventor of the rigid airship, founded the first commercial aerial transport company; one year later, passenger service was inaugurated. Between 1910 and 1914, the fledgling—and very lucky—airline established an all-but-forgotten record: nearly sixteen hundred flights, almost thirty-two hundred hours in the air, and more than ten thousand paying passengers without an injury.¹

The German military authorities were also attracted to this new vehicle. Commercial Zeppelin airships were chartered to train personnel. Both the army and navy ordered Zeppelins built and equipped for military service before the First World War. By its outbreak, German preeminence in lighter-than-air aeronautics was firmly established. The Zeppelin organization was promptly integrated into the national war effort. Years of design and experiment were compressed into each year of the conflict. The Allies scrambled to learn as much as possible regarding German airship “trade secrets,” but their technology lagged well behind that of their opponent.

The use of this novel weapon for offensive bombing of enemy cities provided an irresistible temptation. Zeppelin raids, it was assumed, would bring the war home to civilian populations, undermine national morale, and possibly force termination of hostilities. The first air raid using Zeppelins was conducted against Antwerp in August 1914. By 1916, these attacks were receiving enormous attention from the world’s press.

Zeppelin is a new word of terror which supplements the vocabularies of both England and France. These monster airships have destroyed the boasted security of the English people, based on isolation of the island. England has spent her millions to maintain master[y]of the seas, only to find the airships of Germany have free passage, against which no safeguards can be raised.²

Despite these exaggerations, the military results of the raids were a disappointment. The more effective use of Zeppelins as naval scouts over the Baltic and North Seas was far less known—but of intense interest to both Britain and the United States. Rigid airships flew scouting and defensive reconnaissance missions for the German navy, contributing materially to intelligence gathering. In terms of reconnaissance and mine-spotting, German airships also proved effective in the grim at-sea game of mine warfare between Britain and Germany.

The Allied powers were obliged to take note. As one U.S. Navy observer wrote, “It seemed evident that a new weapon had appeared and that the United States should consider its possibilities carefully.”³ Naval attachés abroad were instructed to furnish information relative to the construction and use of rigid airships. Consequently, samples from Zeppelins brought down by the Allies, as well as photographs and considerable hearsay, were passed on to Washington. Much of this intelligence was useless, but samples of their girders helped unlock the secret of the German aluminum alloy duralumin. The experience and resources of the Aluminum Company of America were enlisted to duplicate the alloy. Similarly, samples of gasbag fabric, which comprised the interior cells of rigid airships, were examined. Although the German process was never duplicated, a substitute method of manufacture was finally developed. These two efforts were to be essential to the American experiment with large airships.

The United States was still not at war, but U.S. observers in Europe were enthusiastic regarding Zeppelin airships as a weapon system. The U.S. Navy was interested. The rigid airship’s primary use appeared to be naval, but coastal defense also involved the Army. Thus, a Joint Army and Navy Airship Board was formed to address questions of policy. Efforts were initiated in 1917 to procure an airship from abroad while, concurrently, design work was begun by the Navy’s General Board.

Control car from L-49 on display in Paris—one of eleven Zeppelins that attacked England in October 1917. Eager for German technology, the Allies investigated Zeppelins under the cloak of armistice, their bases disarmed. Forced down intact, L-49 became the design basis of the United States Navy’s first rigid airship (ZRs in naval parlance). Note the similarity between this car and that on page 32. D. H. Robinson

Engineers were recruited, and the myriad of technical problems attendant to airship design were examined. Important ancillary matters, such as hangars (“sheds” in Europe), production of lifting gas, and airship stations also were evaluated. America entered the war in April 1917. Impressed by the vulnerability of Zeppelins from their inflammable hydrogen, Britain pressed its ally to expand its helium-extraction facilities. The presence of commercial quantities of inert helium in natural gas in the Great Plains and the impetus of wartime demand would prove to be crucial—if an impediment—to America’s nascent LTA program.⁴

In July 1917 the recommendations of the Joint Board were presented. If American rigid airships were wanted for use in the European theater, they should be obtained in England. If operated in the continental United States, they should be constructed instead by Americans to establish the art. And in view “of the very evident use the navy might have for large airships,”⁵ the Navy Department was the logical organization to undertake all such development.

By early 1918 large airships were being mentioned before Congress in connection with wartime appropriations. The armistice intervened. Thus, the war ended before the United States Navy, starting from nothing, could build or procure a rigid airship. However, in July 1919, Congress authorized the Navy to establish a station to erect and operate large airships and to procure two aircraft. One ship was to be purchased abroad, a second built in the United States. This led to the purchase of the British R-38 (American ZR-2), the design and construction of “Fleet Airship No. 1,” known as USS Shenandoah (ZR-1), and the establishment of the Lakehurst naval air station.

Bodensee (LZ-120) at Friedrichshafen, home of Luftschiffbau Zeppelin. Preeminent in the airship arts, Germany’s first postwar Zeppelin, Bodensee, operated commercially August–November 1919 before being hangared by the Inter-Allied Control Commission. Though not a regularly scheduled service, excursions via rigid airship were popular with Germans. U.S. Naval Institute photo archive

What underlay the Navy’s strong interest in airships? In the military environment of the interwar years, the large naval airship represented an ideal long-range reconnaissance platform over vast ocean areas. Cruisers were the conventional scouts for the fleet. In 1919, it must be recalled, the aircraft carrier had yet to appear. Seaplanes and land-based aircraft, moreover, enjoyed a relatively poor (tactical) performance when compared to the large airship’s extraordinary lift, range, and endurance: platforms for strategic search. America is essentially an island nation bounded by two great oceans into which an enemy force might vanish. Hence it was logical that the Navy remained interested in large airships into the 1930s.

Development of the rigid airship would overshadow the smaller nonrigid type until the eve of the Second World War.⁶ Yet the U.S. Navy’s LTA program had begun with blimps. A contract for the first non-rigid airship had been awarded in June 1915. The result was the DN-1 (Dirigible, Nonrigid, No. 1). The ship was not ready for trials at the new Pensacola training station until the spring of 1917. It was not an auspicious beginning.

[DN-1] was so overweight that it could barely lift itself. Its envelope leaked and the power plant functioned badly. It did, however, actually fly—and since the firm had built the ship in good faith and at a cost greatly in excess of the contract price [$45,636], it was formally accepted. . . . After a few short flights it was hangared, deflated, and dismantled.⁷

The Navy Department was determined not to repeat this failure. Based in part on information from attachés regarding antisubmarine operations over the English Channel by British airships (facetiously called “blimps” by HTA aviators), a new design was prepared. The Navy’s B-type airship had an 84,000-cubic-foot envelope volume and a twelve-hour endurance. The aircraft was little more than an airplane fuselage suspended beneath an envelope or “bag.” The Secretary of the Navy (SecNav) approved the design in January 1917. Only a prototype had been planned, but relations with Germany were disintegrating, so sixteen were ordered immediately. The contracts were placed in March 1917. The first ship (B-1) flew in May, and the initial delivery was made to Pensacola that July. Contractor expertise was pooled to meet the order, placed only sixty days prior to the declaration of war.

This order was a thunderbolt, as delivery in any reasonable time was out of the question from existing facilities. No firms had knowledge or experience, and no time could be allowed for experiment and research. There was also no time to build one airship and prove the design; all 16 were wanted at once.⁸

Nine were built by the Goodyear Tire and Rubber Company. Its aeronautical credentials dated from 1911 and emphasized lighter-than-air craft. The firm also assumed all airship training for the Navy. A few miles outside Akron, Ohio, at Wingfoot Lake, a landing field, hangar, shops, hydrogen plant, barracks, and mess halls were constructed. The first class of twelve student aviators began their training in June 1917. Senior officer present: Lt. Lewis H. Maxfield, USN.

An entire organization had to be created. The number of men in naval aviation barely exceeded two hundred, plus forty-eight officers. HTA training centers multiplied almost overnight to meet the wartime demand for flight personnel. LTA training centered in Ohio. The new curriculum would remain essentially unchanged through the 1930s: ground school instruction, then flight training commencing with observation balloons before progressing to free balloons and finally to blimps. The first naval aviators (dirigible) were designated in October 1917. These graduates were assigned to new patrol stations along the American East Coast or sent abroad to operate French airships from French bases. The focus for this patrol activity: German U-boat operations against Britain and France and the little-known campaign mounted against American shipping late in the war.

Floating hangar at Naval Air Station (NAS) Pensacola. Both the British and French had developed nonrigid airships (blimps) for antisubmarine patrol. In March 1915, Congress appropriated $1 million for U.S. Naval Aeronautics, after which the Navy Department completed specifications for its first airship. In 1917 a design competition resulted in DN-1, a humiliating disappointment. It flew, but logged only a few inconsequential flights before being stricken. C. E. Rosendahl Collection, HOAC/University of Texas

B-type nonrigid. Sixteen were ordered in March 1917 for training and for patrol against prowling German submarines. The ship was little more than an airplane fuselage suspended beneath an 84,000-cubic-foot envelope, or bag. Endurance: sixteen hours in a cramped, open car alive with engine noise and propeller blast. Lifting gas: hydrogen. U.S. Naval Institute photo archive

Antisubmarine patrols, convoy escort, and photographic missions were conducted from now-forgotten bases on both sides of the North Atlantic foreshadowing another naval war two decades later. The B-class ships flew more than thirteen thousand hours along the East Coast, but they had little direct combat experience and sunk no submarines. The Navy had chosen the flying boat as its priority air weapon against the submerged enemy. Nonetheless, as far as the LTA community was concerned, its wartime contribution was an important one.

The airship’s greatest value to the Allies during the past war was in convoy work. Indeed, it was common knowledge that a submarine would not attack a convoy escorted by airships. The value depended not so much on their ability to detect a submarine previous to its attack, but on the certainty of their locating the submarine after a torpedo attack, with the resultant destruction of the submarine by depth charges from either the airship or the surface escort.⁹

The Navy by 1918 had accumulated design and operational experience. The C-type was designed by the Bureau of Construction and Repair (Aircraft Division). Increased power and endurance granted loiter capability with convoys—and twin-engine reliability. The last of ten procurements was delivered in March 1919. In 1921, C-7 would log the first flight of an airship inflated with helium. U.S. Naval Institute photo archive

The Navy by 1918 had accumulated a measure of design confidence and operational experience. A wholly new aircraft, the C-type, was designed and thirty ships ordered. This was subsequently reduced to ten after the armistice. Twin engines were the principal design improvement, providing greater reliability, speed, and endurance for loitering with convoys. Envelope volume: 181,000 cubic feet. Further modifications to the C-class and entirely new designs were built and explored following the Great War. By fall 1922, and following flight trials of the new J-type, the blimp had evolved into a significant instrument of naval warfare.

But the rigid airship was destined to absorb the energies and resources of the new program. The blimp was relegated to training officers and crewmen for the big ships, which would dominate naval and also commercial lighter-than-air aeronautics to 1937.

However, by 1925 the military value of the large naval airship was itself being questioned. No one could foresee that the weapon system would not survive the politics and technological advances of the interwar period. This stumbling progress, moreover, would compromise the evolution of the nonrigid type and contribute significantly to the demise of the U.S. Navy’s entire lighter-than-air experiment. But these developments were in the future.

An aerology (meteorology) class, NAS Pensacola, 1922. Airship operations demanded knowledge of weather, particularly surface and lower-level winds. The U.S. Navy’s LTA program would help realize quantum improvements in weather analysis and forecasting. NARA