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Twenty-five years after the U. S. Navy discarded its last “gas bag,” it is about to develop a new series of lighter-than-air (LTA) vehicles. The driving factor in this Program is the need for long-range detec-
veloping naval airships. The industry leaders include Boeing, Goodyear Aerospace, Lockheed Missiles and Space, Westinghouse, and Britain’s Airship Industries Ltd.
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Their efforts have emphasized the long-range surveillance role, although some considered an antisubmarine warfare (ASW) platform, usually towing a hydrophone array through the water as well as using moored and floating sono- buoys. (A discussion of maritime missions for airships is found in Ben B. Levitt, “The Rigid Airship in the Sea Control Mission,” Proceedings, January 1977, pp. 112-114.) Some “black bag” studies examined the use of airships in clandestine intelligence collection roles.
In addition, helicopter pioneer Frank N. Piasecki developed the “helistat” for
Competing for the Navy’s AEW airship contract are Westinghouse- Airship Industries’ updated Skyship 600 and Goodyear’s high-tech ZPG-3W derivative.
bon of aircraft and antiship cruise misses attacking U. S. forces at sea.
The concept of using airships for airborne early warning (AEW) is not new. In the early 1950s, a Navy ZPG-2 airship 1343 feet long and 97 feet high) was modified for AEW, the first of a series of such airships employed by the Navy in that role. The electronically transparent gas bag could provide an ideal position for a search radar antenna; the production ^PG-3W airships, in service 1957-61, "'ere 404 feet long and carried a 41-foot, r°tating antenna.
However, the AEW airships were short-lived. The cost of supporting the re*atively small airship community, improvements in fixed-wing AEW aircraft, and—most significant—the high cost of jhe Polaris and aircraft carrier programs the Navy to decide in 1961 to discard 'be airships.
. During the 25-year interlude, interest !n airships continued in several ways: Airship buffs, led by Vice Admiral E. Rosendahl, U. S. Navy, until his .ath in 1977, avidly promoted airship feintroduction, producing scores of articles for a variety of publications.
The aerospace industry has produced bumerous studies and proposals for de-
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The U. S. Navy was a latecomer to airships, trailing behind the other major world powers and the U. S.
Army. The Navy ordered its first blimp—a non-rigid airship—in 1915. This notably unsuccessful craft, designated DN-1, did not make its first flight until April 1917, the month the United States entered World War I.
By the end of the war in November 1918, the Navy had many blimps in service, several of which were flying antisubmarine patrols in Europe. These blimps’ crews sought out U-boats visually. In the fall of 1917, the British began testing hydrophones lowered from blimps to detect submarines. Just before the war ended, hydrophones were ordered for all British blimps.
Most historians believe that the term “blimp” derived from the British Model B “limp.” But more authoritative sources credit Lieutenant A. D. Cunningham, Royal Navy, who on 5 December 1915 pressed his thumb into the gas bag of the airship Sea Scout No. 12, resulting in a “blimp” sound that rapidly became part of the airman’s lexicon.
Blimps had no supporting structures to maintain their shape. However, the nose was stiffened by a ribbed structure similar to that of an umbrella. A gondola was suspended below to house the crew and support the engines. Later, when non-explosive helium (a U. S. Government monopoly) replaced the explosive hydrogen as a lifting medium, the gondolas, or control cars, were attached to the gas bag.
In 1921, the U. S. Army Air Service took responsibility for coastal patrol with blimps, or non-rigid airships, and the Navy concentrated on rigid airships for long- range scouting in support of the fleet. The Navy was allowed to retain only those non-rigids necessary for training and experiments. One of the experimental blimps was the ZMC-2, a pressure-type airship like other blimps, but fitted with a thin metal skin. First flown in 1929, the ZMC-2 flew for ten years—the only airship of its type ever built.
The success of the German Navy’s Zeppelin airships in World War I awakened the U. S. Navy to the potential of those large, graceful, rigid airships. Zeppelins— named for airship builder Count Ferdinand von Zeppelin—were real “flying ships,” with separate gas containers inside a rigid metal framework covered with fabric.
Shortly after the war, the U. S. Navy adopted the term LTA (lighter-than-air) for both blimps and rigid airships. The prefix letter “Z” was established for LTA, e.g., ZP for airship patrol squadron, ZJ for airship utility squadron, and AZ for an auxiliary airship tender (of which there were none).
The U. S. Navy’s first rigid airship was the ZR-1.
The 1916 design was subsequently modified to incorporate German features. Assigned the name Shenandoah, the ZR-1 made her maiden flight in 1923. The 680-foot airship had a brief, unsuccessful career, crashing in a storm in September 1925. The ZR-1 made 57 flights, among them a 9,317-mile double crossing of the United States. (The British R.38 was to have been transferred to the U. S. Navy as the ZR-2, but she broke up on trials.)
Three more rigid airships followed. The Los Angeles (ZR-3) was a German-built, commercial airship, which made her 5,060-mile delivery flight from Germany to the Navy’s airship base in Lakehurst, New Jersey, in October 1924. The Los Angeles made 331 flights before retiring in 1932.
The most notable Navy rigids were the 785-foot flying aircraft carriers Akron (ZRS-4) and Macon (ZRS-5), commissioned in 1931 and 1933, respectively. Each could carry four Curtiss F9C-2 Sparrowhawk biplane fighters and launch and recover the fighters while in
the heavy-lift role. After more than a decade of development, he completed his flight demonstrator—the engines and rotor systems of four SH-34J Seabat helicopters attached to a ZPG-2 airship gas bag. But this craft crashed early in its test program on 1 July 1986. Piasecki’s next- generation helistat was to incorporate four CH-53D Sea Stallion systems with a larger airship, but further development of this concept appears doubtful.
Another unusual heavy-lift craft employing airship technology is the Magnus Aerospace Corporation LTA 20-1 being developed in Canada. It combines several aerodynamic principles to lift about 60 tons. A scale model of the Magnus craft was demonstrated at the U. S. Naval Academy on 20 November 1984.
► Several studies and projects have been undertaken by the Navy and Coast Guard, other military services, and other government agencies. Most of these efforts have concentrated on unmanned aerostats (the subject of a future “The U. S. Navy” column).
Studies and proposals have been made for both manned and unmanned naval ocean-surveillance airships. But once discarded, manned airships seemed more difficult to resurrect. The Coast Guard has periodically investigated the possible use of manned airships for surveillance, search and rescue, and even for boarding ships and craft under investigation. (The search team would climb down a rope ladder or rappel, neither means having the promise of success, especially with small craft.)
A significant step was taken in 1980 when the Coast Guard and NASA agreed to jointly sponsor development of a manned airship employing the latest synthetics and adhesives for the gas bag, automated controls, and ground/ship recovery systems, which would reduce the large ground crews required to land and tether blimps. In 1983, the Coast Guard evaluated a British-built Airship Industries Skyship 500 manned airship at the Naval Air Test Center Patuxent River, Maryland; 250 flight hours were flown.
(The deflated skyship 500 was flown to the United States in a C-141 transport.)
By 1985, the Coast Guard was ready to lease a larger Skyship 600 airship for at least five months of operational service. Dubbed PACE, for patrol airship concept evaluation, the program envisioned an LTA vehicle that would fly a variety of patrol/surveillance missions, carrying a crew of six on missions lasting at least 48 hours. (The French Navy was already evaluating a Skyship 600, but apparently no procurement decision has been made.)
The Navy’s formal entry into the LTA program and fiscal problems caused the Coast Guard to cancel its manned LTA efforts in September 1985. The Coast Guard announced that the “large scale multi-year LTA program recently launched by the Navy would overshadow [the Coast Guard’s] project research effort. Continuation of the Coast Guard program would duplicate the Navy research and would be less comprehensive.” Instead, the Coast Guard has concentrated on unmanned aerostats.
flight. The airships were to scout ahead of the fleet; the fighters were to fend off enemy attackers. The rigids’ range was rated at 9,200 miles.
The Akron crashed at sea in April 1933, as did the Macon in February 1935. These losses ended the Navy’s rigid airship program. The rigids were in commission and on the Navy List, the same as surface ships and submarines.
In 1937, the Army transferred its airships to the Navy, which then became the world’s exclusive operator of military airships. This fleet grew to 167 units during World War II. These were used mostly for ASW patrol, and were considered highly effective. After the war, the effectiveness of long-range patrol aircraft reduced the 'niportance of blimps, and most were discarded.
In the early 1950s, a ZPG-2 patrol airship was modified for the AEW role. The electronic equipment ineluded the AN/APS-20 search radar and AN/APS-62 height-finding radar, plus identification friend or foe and electronic countermeasure systems. The ZPG-2 had two Piston engines and a crew of 21. One set a record flying 8.216 miles without refueling. (Blimps were regularly refueled from aircraft carriers.)
By the end of World War I, the Navy had many blimps in service, some conducting ASW in Europe. The Navy’s first non-rigid airship was the DN-1, which was noted for its floating hangar and its short, unsuccessful career.
Subsequently, the ZPG-3W was ordered into production. The 404-foot airship had two piston engines that could push it over the sea at 85 knots. The world’s largest non-rigid airship, it was fitted with search and height-finding radars, and manned by a crew of 24. (Under the 1962 redesignation scheme, the ZPG-2W became the EZ-1B, and the production -3W models became EZ-lCs.)
These airships were intended to support the seaward extension of the distant early warning (DEW) line to provide warning of Soviet bomber attacks against the United States. However, the program was short-lived; the Navy’s last LTA flight was in August 1962.
The Navy acquired 241 non-rigid airships between 1917 and 1958, including 13 front allies during the World War I period—six from Britain, six from France, and one from Italy. Others were acquired from the U. S. Army. These were in addition to the four rigid airships.
Although the new LTA “vehicles” will be blimps, the Navy prefers the term “airship.” Of course, new jargon has been developed by the Navy: BASA, for battle surveillance airship system, will now be found in most Navy documents addressing blimps.
Note: This sidebar is based in part on Gordon Swan- borough and Peter M. Bowers, United States Navy Aircraft since 1911 (Annapolis, MD: Naval Institute Press, 1976).
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The current Navy program had several °rigins, including proposals by Charles iChuck) Myers, who had helped sell the reactivation of the Navy’s battleships, ^avy studies indicated that large, radarcarrying airships could provide early warning of approaching hostile aircraft and cruise missiles. In 1985, Secretary of the Navy John Lehman approved a formal airship development program.
Congress’s endorsement and Secretary Lehman’s support create a high probabil- 'ty that the Navy will proceed with the Program. Requirements and characteris- t'cs of the possible Navy LTA vehicle are n°w being determined, based on Navy study contracts awarded in 1985 to Goodyear, Westinghouse, and Boeing for air- I’hip concepts, and to Hughes, Westing- house, and RCA for radars. A suitable surveillance radar would require an airship at least the size of the ZPG-3W— some 400 feet long and a gas bag volume about 1.5-million cubic feet. A 30-day at'Sea endurance requires a much larger a,rship, probably with a gas-bag volume of slightly less than three-million cubic feet, a length of about 480 feet, and a 110-foot diameter. Both turboprop and reciprocating engines are being considered for propulsion, to provide a speed of perhaps 100 knots in no-wind conditions.
Assistant Secretary of the Navy for Research, Engineering, and Systems Melvyn R. Paisley said LTA vehicles “will provide a high-leverage payoff” for the Navy. With a fiscal year 1987 program start, Paisley contends that LTA is “another smart, simple solution” to a Navy requirement. Preliminary estimates call for 20-50 airships, although numbers up to 100 have been considered. A program of 20-50 units could cost $3 billion or more.
Their prime mission will be active and passive surveillance. Other missions considered include ASW and over-the-horizon targeting for ship-launched cruise missiles.
Goodyear and Westinghouse competed for a contract to build an operational airship demonstration model to be constructed and test flown by 1991. While Goodyear is basing its submission on the ZPG-3W, Westinghouse teamed with Airship Industries and is offering an upscaled version of Airship Industries’ Skyship series, called the Sentinel 5000. Various radars and other sensors are under consideration, including the General Electric APS-138/145 radar used in E-2C Hawkeye AEW aircraft, and the Westinghouse TPS-63.
Airships have long endurance, a high degree of survivability, and are expected to be comparatively inexpensive to operate. Computer technology, coupled with data links and automatic systems, will provide considerable mission flexibility. But there could be problems in supporting airships from Navy surface ships, which would provide relief crews, fuel, and supplies during the airship’s 30-day mission.
It appears that LTA’s time has come— again. Like the battleship, LTA proves that modem technology can make an “old” concept useful.