USS Akron
USS Akron (ZRS-4) was a helium-filled rigid airship commissioned by the United States Navy, serving as the lead ship of her class and the Navy's first such vessel from October 1931 until her loss in April 1933.[1] Constructed by the Goodyear-Zeppelin Corporation in Akron, Ohio, she measured 785 feet in length with a maximum diameter of 132.5 feet and a height of 152.5 feet, accommodating 6,500,000 cubic feet of lifting gas.[1] Designed for long-range scouting and reconnaissance, Akron featured innovative engineering, including an internal hangar capable of housing and launching fixed-wing aircraft via a trapeze mechanism, marking an early experiment in airborne aircraft carrier operations.[1] During her brief career, Akron conducted multiple operational flights from Naval Air Station Lakehurst, New Jersey, including search exercises with the Scouting Fleet in January 1932 and a deployment to the West Coast in May 1932, where she successfully tested aircraft recovery with Curtiss F9C-2 Sparrowhawk fighters.[1] Her complement typically numbered around 89 officers and enlisted men, supported by eight engines providing a maximum speed of 72 knots.[1] Despite early mishaps, such as a tail damage incident in February 1932 and a mooring accident in May 1932 that claimed two lives, Akron demonstrated the potential of rigid airships for extended patrols and contributed to advancements in lighter-than-air aviation.[1] Akron met her end on 4 April 1933 during a routine radio calibration flight off the New England coast, when severe weather—a powerful downdraft in a thunderstorm—caused her tail to strike the water, leading to structural failure and rapid flooding.[1] Of the 76 aboard, including Rear Admiral William A. Moffett, Chief of the Navy's Bureau of Aeronautics, only three survived after enduring frigid waters without life jackets or sufficient exposure gear; the disaster remains one of the deadliest in early aviation history, prompting congressional scrutiny of dirigible safety but affirming weather as the primary causal factor over inherent design flaws.[1][2]Design and Construction
Technical Design and Innovations
The USS Akron (ZRS-4) featured a rigid airship structure composed of duralumin girders forming 17 main rings spaced approximately 50 feet apart, with longitudinal girders providing rigidity without the radial wiring typical of earlier Zeppelin designs.[3] This innovation, developed by the Goodyear-Zeppelin Corporation, utilized deeper main frames for enhanced strength, supported by three internal keels—one dorsal and two at 45-degree angles—for structural integrity and crew access. The envelope, made of doped cotton fabric, enclosed a nominal gas volume of 6,500,000 cubic feet of non-flammable helium, enabling safer operations compared to hydrogen-filled predecessors, though requiring a larger volume to achieve equivalent lift.[1] [4] A key innovation was the integration of an internal hangar deck, measuring 75 feet long, 60 feet wide, and 16 feet high, capable of housing up to five Curtiss F9C Sparrowhawk fighter aircraft for scouting missions. Aircraft recovery and launch occurred via a T-shaped ventral opening equipped with a trapeze mechanism, allowing planes to hook onto the airship in flight and be reeled into the hangar, extending the fleet's reconnaissance range while minimizing exposure of the slow-moving airship to enemy threats.[4] [1] Propulsion was provided by eight Maybach VL-2 diesel engines, each delivering 560 horsepower, mounted internally and connected via long shafts to swiveling outrigger propellers extending 16 feet from the hull. These propellers could rotate up to 90 degrees for vectored thrust, improving directional control and enabling vertical maneuvers not possible with fixed propellers. The design achieved a maximum speed of 72 knots and cruising speed of 50 knots, with overall dimensions of 785 feet in length, 132.5 feet in maximum diameter, and 152.5 feet in height. Heated crew quarters, utilizing engine cooling water, addressed comfort in varying altitudes, supporting a complement of 89 personnel.[4] [1]Construction Process
Construction of the rigid airship USS Akron (ZRS-4) began on October 31, 1929, at the Goodyear-Zeppelin Corporation's facility in Akron, Ohio.[1] The Goodyear-Zeppelin Corporation, a joint venture between the Goodyear Tire & Rubber Company and Germany's Luftschiffbau Zeppelin GmbH, was established to leverage German expertise in rigid airship design while adapting it for American use with non-flammable helium.[5] The construction site was the newly completed Goodyear Airdock, a massive hangar measuring 1,175 feet long, 325 feet wide, and 107 feet high, designed specifically for building large airships like the Akron and its sister ship USS Macon.[6] The assembly process started with the erection of the airship's rigid framework, composed of lightweight duralumin girders formed into 17 main rings and 28 intermediate frames, connected by longitudinal longerons.[7] This skeletal structure, which measured 785 feet in length and had a maximum diameter of 133 feet, was built horizontally within the Airdock using cranes and scaffolding. By November 5, 1930, the framework was substantially complete, allowing workers to proceed with covering it in cotton fabric doped for weather resistance.[7] Internal components followed, including the installation of 20 helium gas cells made from goldbeater's skin, a gelatinous membrane derived from animal intestines, which provided the lift without the fire risks associated with hydrogen used in European zeppelins.[5] Subsequent phases involved fitting the eight 560-horsepower Maybach engines in external gondolas, constructing the control car at the bow, and integrating wiring, instrumentation, and living quarters for the crew.[1] The process required precise engineering to ensure structural integrity under varying pressures and loads, with innovations such as a monocoque-like design distributing stresses across the girders rather than relying on a continuous outer skin. Construction concluded in mid-1931, after which the airship underwent inflation with helium and ground tests prior to its maiden flight on August 25, 1931.[5]Key Engineering Challenges
The USS Akron's design and construction faced significant engineering hurdles stemming from its massive scale and departure from prior rigid airship precedents, requiring adaptations for helium's lower lift compared to hydrogen. With a gas volume of 6,850,000 cubic feet to achieve adequate buoyancy, the airship measured 785 feet in length and 132 feet, 11 inches in diameter, demanding robust structural innovations by the Goodyear-Zeppelin Corporation.[4][4] To enhance rigidity without traditional Zeppelin-style radial wiring, engineers employed deep main girders in place of standard rings, supplemented by three keels—one dorsal and two at 45-degree angles—for improved strength and internal access.[4] This configuration, devised by Goodyear-Zeppelin engineer Karl Arnstein, represented a radical evolution from earlier designs to accommodate the ship's scouting role and internal aircraft operations.[5] The duralumin alloy frame balanced lightness and durability for this unprecedented size, though fabricating and assembling the lattice under precise tolerances posed logistical challenges in the purpose-built Akron Airdock.[8] A primary innovation—and attendant challenge—was integrating an internal hangar measuring 75 feet long, 60 feet wide, and 16 feet high, capable of housing five scout aircraft, with a pioneering trapeze mechanism for mid-air launch and recovery.[4] This system required meticulous engineering to manage dynamic aerodynamic loads and ensure structural integrity during aircraft hook-ons, testing the limits of the girder framework. Propulsion added complexity, incorporating eight 560-horsepower Maybach VL-2 diesel engines with reversible propellers swiveling through a 90-degree arc for precise directional control, while crew quarters were heated via engine cooling water to maintain habitability.[4][4] Design iterations addressed visibility and stability issues through Change Order No. 2, which shortened and deepened the tail fin, relocated the control car 8 feet aft, and reduced fin attachments to two main frames, necessitating recalculations of altered loads across the structure.[4] Construction commenced on 31 October 1929, with hull erection beginning in March 1930, culminating in launch on 8 August 1931 after overcoming these technical obstacles through the collaboration of American and imported German expertise.[1][1]Specifications
Structural and Performance Details
The USS Akron's structure consisted of a rigid framework built from duralumin, an aluminum-copper alloy prized for its high strength-to-weight ratio, forming interconnected girders and rings that maintained the airship's shape under internal gas pressure.[9] This design, developed by engineer Karl Arnstein at Goodyear-Zeppelin Corporation, incorporated 17 main transverse rings spaced along the 785-foot length, connected by 28 longitudinal girders, enabling a non-rigid envelope supported by helium lift rather than external tension.[10] The envelope divided into 12 separate gas cells to mitigate risks from leaks or damage, with a total capacity of 6,500,000 cubic feet of helium providing buoyancy for a dead weight of 221,000 pounds and a useful load capacity of 182,000 pounds.[1] Key structural innovations included an internal hangar approximately 75 feet long, 60 feet wide, and 16 feet high, positioned amidships to accommodate up to five parasite fighter aircraft, along with a trapeze mechanism for in-flight launch and recovery to extend scouting range without compromising the airship's aerodynamics.[3] The control car, suspended beneath the hull, housed navigation and command facilities for a crew of 60, while defensive features comprised eight .30-caliber machine guns mounted at strategic positions.[11]| Specification | Detail |
|---|---|
| Length | 785 feet (239 meters)[1][11] |
| Maximum Diameter | 132.5 feet (40 meters)[1][10] |
| Height | 152.5 feet[1] |
| Engines | 8 × Maybach VL-2, 560 hp each[11][10] |
| Maximum Speed | 72 knots (83 mph)[1] |
| Cruising Speed | 50 knots[1] |
| Range | 5,940 nautical miles[11] |