ZMC-2
The airship operated by the US Navy under the designation ZMC-2 from 1929 to 1941 was a test model of an all-metal airship for testing this type of construction. In contrast to conventional airships, its hull was not made of a fabric, but of 0.24 mm (0.0095 inch ) and 0.2 mm (0.008 inch) thick duralumin sheet . The shell was also a gas cell. This design and its compact form, it also received his nickname Tin Bubble or Tinship (German: sheet bladder or sheet ship ).
All-metal airship concept
The concept of an all-metal airship was already devised by Konstantin Eduardowitsch Ziolkowski , who published some theoretical studies on steerable all-metal airships in the 1880s. In front of the ZMC-2, only an airship with a metal outer skin rose into the sky. It was David Schwarz's airship . On November 3, 1897, it made only one journey on Tempelhofer Feld near Berlin, and when it landed it was irreparably damaged. This ship was the first application of the then new material aluminum , which was only presented at the Paris World Exhibition in 1889, in aviation .
1926, around the same time, in the ZMC-2 was started Thomas Benton Slate in a hall of the airfield of Glendale in California , USA, to build from private drive an all-metal airship. Slate used aluminum checker plate , which he riveted to a rigid shell . A steam turbine drive system that was supposed to generate negative pressure was provided at the bow for propulsion . The already filled airship was pulled out of the hall several times before completion. During construction, Slate invited fathers to bring their children and watch him build the ship. Tens of thousands also came. On December 19, 1929, the “City of Glendale” named airship was displayed under the impressed eyes of several hundred people. However, it should never experience a journey. The sun was shining on the float and the hull began to bulge . The rivets tore with a loud bang that was reminiscent of gunfire and the gas escaped. When the ship was listed, the onlookers ran away fearing that the hydrogen-filled airship might turn into a ball of fire. However, it just fell to the floor with a loud clang. The reason for this debacle is not entirely clear. A faulty pressure relief valve is mentioned. The ship was too badly damaged to repair. Almost the entire shell would have had to be dismantled and reassembled. The project was abandoned and the Glendale era of airships ended.
ZMC-2
The US Navy designation ZMC-2 is divided into the letters Z, MC and the number 2. The US Navy used the Z as the first letter to classify all of its airships and lighter-than-air devices. The MC was for Metal Clad , about to German metallbeplankt . The 2 resulted from the lifting gas volume of around 200,000 cubic feet , exactly 202,200.
The aluminum thickness of 2 mm (0.08 inch) given in various sources and the resulting weight per unit area are too high in relation to the available buoyancy to have been used for large parts of the ship.
Development and construction
The plans for ZMC-2 were developed by the American engineer Ralph Hazlett Upson, who also drove the first B-class impact airship in Goodyear's service , from around 1922. He founded his own company for his development, the Aircraft Development Co. In 1926 the US Navy ordered a test model. This design was made possible by the development of a riveting machine by Edwin J. Hill, who was able to join the thin aluminum sheet in a gas-tight manner using new sealing materials . The riveting machine built for this purpose could set 5000 rivets with a diameter of 0.9 mm per hour. It drilled three rows of rivets at the same time and was operated by two people. The rivets were placed in the bores of the machine from endlessly fed wire and provided with rotating cams with heads. As a sealant was bitumen used.
As early as 1924 the US military was offered an "MC-0.8" (an all-metal airship with a volume of 80,000 ft³, around 2266 m³). It was to be built on the Scott Airfield. It is reported that an "MC-1" was partially manufactured, but material tests showed corrosion and embrittlement of the duralumin. A hull section measuring 8.8 x 10.4 m (29 x 34 ft) weighing 181 kg (400 lbs) was tested to destruction to verify design assumptions. The gas tightness was also examined and found to be lower than expected. Further experiments concerned the behavior of the gas envelope in the event of a pressure drop inside. The material was wrinkled and it looked like it would stay deformed forever, but after increasing the internal pressure, the material returned to its old shape and it was no longer possible to see where the wrinkles had been before. After these attempts, the decision was made to use "Alclad" aluminum, which was manufactured by the Aluminum Company of America . It was a sandwich material . The core consisted of duralumin (Dural 17S, later Alcad 24S), which was coated with pure aluminum.
In May 1927 the Aircraft Development Corporation began construction of a 37 × 55 × 37 m (length × width × height - 120 × 180 × 120 ft) large airship hangar at Detroit's Grosse Ile Airport , which was completed in September. ZMC-2 was supposed to be built there. For flight operations they set up a 914 m (3000 ft) circle north of the hangar. This concrete field is still preserved between the runways of the airfield.
Construction of ZMC-2 began on March 7, 1928 with the first rivet in the bow section. The airship was built in two vertical halves similar to two eggshells that were joined together in February 1929. In June the motors were installed in the nacelle, it was attached to the airship body in July. The following August, ZMC-2 was filled with helium . In contrast to other airships, however, it was not possible to fill an empty folded envelope or gas cell; instead, the air inside the airship body had to be replaced by helium. For this purpose, the float was first filled with carbon dioxide (CO 2 ) from below and the air was let out at the top. Then helium was poured in from above and the CO 2 was discharged from below. When a helium-carbon dioxide mixture was measured, the remaining CO 2 was started to be filtered out using a gas scrubber .
construction
The metal shell held together by around 3.5 million rivets, which was supported inside the mold by 24 longitudinal straps and 12 ring profiles, had a gas loss of around two liters per square meter per day and had a similar quality to the one used at the time. B. Goldschläger skin used for the gas cells at Zeppelin , but it was not resistant to aging. In order to maintain the shape of ZMC-2, an overpressure had to be constantly maintained in the float. Therefore it was classified by the Navy as an impact airship despite the rigid metal construction . Internal pressure was maintained by two ballonets with a maximum volume of 640 cubic meters (22,600 ft³) in the front and 793 cubic meters (28,000 ft³) in the rear ballonet.
The lifting gas volume of ZMC-2, excluding the ballonets, was around 5,727 cubic meters (202,200 ft³) of helium. The ship was 45.52 meters (149 ft, 4 in) long, with a largest diameter of 16.03 meters (52 ft, 7 in). This corresponded to the size of smaller impact airships, but the comparatively small aspect ratio was striking. The eight relatively short tail fins at the stern, which were provided with movable control surfaces and had a total area of 40.9 m² (440 ft²), were also exceptional .
The curb weight was 4,135 kg (9,115 lb). The payload in addition to the two pilots, the ballast and the supplies was about 340 kg (750 lbs). Compared to impact airships of a similar size, this is only a relatively low value, but it was a test vehicle that was supposed to test the construction method for larger models.
The drive consisted of two nine-cylinder radial engines of the Wright J-5 Whirlwind type , which were attached to the left and right of the nacelle and each powered a two-blade metal propeller with a diameter of 2.8 m (9 ft, 2 in) as a pulling propeller. The engines had an output of 164 kW (220 hp) each. The top speed was up to 113 km / h (62-70 mph; with 440 hp drive power), the cruising speed was around 84 km / h (50-52 mph with 220 hp drive power). The range at cruising speed is just over 1000 km (approx. 675 mi) with a flight duration of up to 11 hours, the maximum range in calm conditions was around 1610 km (1000 mi). The airship was steered by a crew of two.
business
The maiden voyage of 49 minutes and 55 seconds took place on August 19, 1929 at Detroit's Grosse Ile Airport . Pilots were U.S. Army Air Corps Capt.William J. Kepner and flight engineer MSgt Joseph Bishop. In the following days, further trips were made, including a 30-hour inspection trip. On August 25, the airship visited the National Air Races over Cleveland . The Aviation magazine then praised the low-vibration airship, which did not require any adjustments or changes after a total of 9 hours of flight.
ZMC-2 then left Detroit for its future home base, the US Naval Air Base Lakehurst , where it arrived the next day, September 12th, after a 16-hour, nearly 1000 km (600 mi) uninterrupted journey and the U.S. Navy was handed over. It was given the marine serial number A-8282 . In the following days, various holes were found in the shell. ZMC-2 had to take several hits from the rifles of cocky Americans on its journey.
Trips across New York City and the Atlantic Ocean were made on September 16 after the top speed tests were completed. All flight attempts were successfully completed by September 25th. ZMC-2 fulfilled all contractually stipulated requirements and had already passed all tests in the first attempt with small safety reserves.
In May 1930, ZMC-2 and ZR-3 USS Los Angeles were guests at the New York Aircraft Salon and the demonstrations of naval aviators.
In the next period many trips were made around Lakehurst. 9-hour journeys were common. For a time, the ship was operated from the US Army's airship base, Langley Airfield. On May 31, 1931, it took part in the New York Fleet Parade with K-1 , a naval impact airship.
At the end of 1933 the lifting gas was released for the first time in order to inspect the ship from the inside. The metal surface was in good condition and the airship was put back into service. However, there were only occasional trips. It is reported that it was in the air on August 19th every year for his "birthday". After the last overhaul in December 1938, the ship only completed 5 hours of flight.
In Lakehurst, ZMC-2 also met the large rigid airships of that time and even carried out trips with them (e.g. with the USS Los Angeles ), or was accommodated in the same hall when LZ 129 “Hindenburg” visited .
After just six years, the airship had covered around 92,000 kilometers on 752 journeys in over 1,400 flight hours. In the meantime it also got a new set of engines. Some sources indicate a drive power of 300 PS (224 kW) in contrast to the original 220 PS. Presumably the new engines (also Wright J5) were more powerful. The airship was in service with the US Navy until it was decommissioned after its planned useful life in 1941 and had been in the air for 2,256.6 hours by then, which is a testament to the capabilities and robustness of this test model. The last trip took place (not entirely by chance) on August 19, 1939 for the 10th anniversary, after which further tests were carried out on the ground.
Admiral Moffett had already described the main function of the airship in his annual report in 1926: ... a purely experimental ship, intended to test the applicability of the new type of construction in which it was created. The ship was therefore mainly used for experiments, but was also involved in various training, relief, rescue and disaster missions. The airship could only be steered unsatisfactorily in bad weather and at slow speed, but this was mainly attributed to its small size and not to the design principle. Another problem was the temperature of the envelope, it could fluctuate greatly between ground level and flight altitude.
The nacelle was saved from scrapping at the request of the commanding officer of the Lakehurst naval air base and handed over to the airship school in Lakehurst as a fully equipped training object, including the engines.
Other Projects
The Metalclad Airship Co. , which won a tender for the construction and design of all-metal airships against the ZMC-2 manufacturer Aircraft Development Co. , had already been awarded a contract for the development of all-metal airships by the US Department of Aviation in 1932.
In online archive directories there are entries about bid documents and drawings of Metalclad Airship Corp. for a sixth US Navy Rigid Airship under the designation ZMC-12. There is also a note about a lifting gas volume of 1,200,000 cubic feet, almost 34,000 m³. This is roughly six times the size of the ZMC-2. Two further entries concern offers from this company for all-metal airships with the designations MC-20 and MC-74 from the years 1934 and 1935.
At the beginning of the 1970s, Dornier AG developed a concept study for a passenger and a cargo airship , which should also have had an aluminum shell. However, the study was never carried out.
In 1985 Wren Skyships announced in Great Britain that they would build a 128 m long all-metal airship, called RS.1, as a prototype for larger transport airships .
Overall, no more airships of this type were made. The ZMC-2, the airship built by David Schwarz, and the “City of Glendale” have therefore remained the only airships with a metal hull, despite the promising concept.
See also
literature
English:
- Walker C. Morrow: The Metalclad Airships , private print, Grosse Ile 1987 USA, contains the original book World's first Metalclad Airship by Aircraft Development Co., ca.1930
- Carl B. Fritsche: THE METALCLAD AIRSHIP in FLIGHT, Part 1 in the May 22, 1931 issue; Pages 461–646 and Part 2 in the May 29, 1931 edition, pages 483–487; Available online in the flightglobal.com archive
Web links
- Mirko Baum: Essay on rigid airships and aluminum ( Memento from May 8, 2012 in the Internet Archive )
- oldbeacon.com/beacon/airships/zmc-2.htm (English)
- http://nasgi.org/zmc2.htm (English) u. a. Pictures from the construction
swell
Literature sources
English:
- US Navy: Kite Balloons to Airships ... the Navy's Lighter-than-Air Experience; (Edition on 75 Years of US Navy Aviation); Published by the Deputy Chief of Naval Operations (Air Warfare) and the Commander, Naval Air Systems Command, Washington, DC, Edited by Roy A. Grossnick, Designed by Charles Cooney, US Government Printing Office: 1983-187-029 ( online at Naval Historical Center or PDF download ( Memento from April 4, 2014 in the Internet Archive ))
- James R. Shock: US Navy Pressure airships 1915–1962, A history of US Navy Airships, (non-rigid, semi-rigid and metalclad) by individual airship M & T Printers, New Smyma Beach, Florida 1994 ISBN 0-9639743- 3-5
- G. Swanborough, PM Bowers: United States Navy Aircraft since 1911 , Naval Institute Press 1990, pp. 582-583
Individual evidence
- ↑ http://vintageairphotos.blogspot.de/2013/08/slates-strange-dirigible.html accessed on December 28, 2016
- ↑ Flight edition of February 7, 1929 pages 101 and 102; online in the archive of flightglobal.com ; accessed on December 28, 2016
- ^ Carl B. Fritsche: THE METALCLAD AIRSHIP in FLIGHT, Part 1 of the article in the May 22, 1931 issue; Page 462; available online in the flightglobal.com archive
- ^ First flights of the Metal-Clad Airship; John T. Nevill; Aviation; Issue of August 31, 1929 pp. 474–478; online behind the registration barrier in the Aviation.com archive , accessed on October 15, 2016.
- ^ Carl B. Fritsche: THE METALCLAD AIRSHIP in FLIGHT, Part 1 of the article in the May 22, 1931 issue; Page 463; available online in the flightglobal.com archive
- ^ ZMC-2 Flies toe Cleveland; Aviation; Issue of August 31, 1929 page 485; online behind the registration barrier in the Aviation.com archive ; accessed on October 15, 2016
- ↑ ZMC-2 Flown to Lakehurst; Aviation; Issue of September 21, 1929 page 621; online behind the registration barrier in the Aviation.com archive ; accessed on October 15, 2016
- ^ To Stage Air "Attack" During New York Show; Aviation; May 3, 1930 issue page 912; online behind the registration barrier in the Aviation.com archive ; accessed on October 15, 2016
- ↑ FEASIBILITY STUDY OF MODERN AIRSHIPS PHASE II, VOL. III; HISTORICAL OVERVIEW (TASK I); GOODYEAR AEROSPACE CORP .; AKRON, OH; AUGUST 1975; Pages 28 and 29; Online as PDF , accessed on October 15, 2016.
- ↑ J. Bleibler: The fifties and sixties - large airship projects in Germany and the USA . In: M. Meighörner (ed.): Airships that were never built . Verlag Robert Gessler, Friedrichshafen 2002, pp. 170 f., ISBN 3-86136-076-4 .
- ^ Flight, Wren proposes rigid airship; Edition: August 31, 1985; Page 15; online as PDF , accessed on December 26, 2016.
