Non-rigid airship
Encyclopedia
Airship
An airship or dirigible is a type of aerostat or "lighter-than-air aircraft" that can be steered and propelled through the air using rudders and propellers or other thrust mechanisms...
without an internal supporting framework or keel. A non-rigid airship differs from a semi-rigid
Semi-rigid airship
Semi-rigid airships are airships with a partial framework. These often consist of a rigid, or occasionally, flexible, keel frame along the long axis under the aerodynamic hull envelope. The partial framework can also be located inside the hull...
airship and a rigid airship
Rigid airship
A rigid airship is a type of airship in which the envelope retained its shape by the use of an internal structural framework rather than by being forced into shape by the pressure of the lifting gas within the envelope as used in blimps and semi-rigid airships.Rigid airships were produced and...
(e.g., a Zeppelin
Zeppelin
A Zeppelin is a type of rigid airship pioneered by the German Count Ferdinand von Zeppelin in the early 20th century. It was based on designs he had outlined in 1874 and detailed in 1893. His plans were reviewed by committee in 1894 and patented in the United States on 14 March 1899...
) in that it does not have any rigid structure, neither a complete framework nor a partial keel, to help the airbag maintain its shape. Rather, these aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
rely on both a higher pressure of the lifting gas
Lifting gas
Because of the Archimedes' principle, a lifting gas is required for aerostats to create buoyancy. Its density is lower than that of air . Only certain lighter than air gases are suitable as lifting gases.- Hot Air :...
(usually helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
) inside the envelope and the strength of the envelope itself.
The term "blimp" refers only to free-flying aircraft. The term is sometimes erroneously used to refer to the tethered craft known as moored balloon
Moored balloon
A moored balloon is an inflated fabric structure, often shaped like an airship and usually filled with helium, that is restrained by a cable attached to the ground or a vehicle. Moored balloons differ from airships and free balloons in that it is not free-flying.Moored balloons are sometimes...
s. While often very similar in shape, moored balloons have no propulsion and are tethered to the ground.
Principle
Since blimps keep their shape with internal overpressure, typically the only solid parts are the passenger car (gondola) and the tail finsEmpennage
The empennage , also known as the tail or tail assembly, of most aircraft gives stability to the aircraft, in a similar way to the feathers on an arrow...
. A non-rigid airship that uses heated air instead of a light gas (such as helium) as a lifting medium is called a hot-air airship
Thermal airship
A thermal airship is an airship that generates its lift via the difference in density due to a temperature differential between the gas inside its envelope and the ambient air. Currently all thermal airships use hot air, as used in a hot air balloon, as their lifting gas...
.
Volume changes of the lifting gas, due to temperature changes, is balanced using ballonet
Ballonet
A Ballonet is a air-filled flexible container that is located inside the envelope of a non-rigid or semi-rigid airship. Such an airship can have one or more ballonets, commonly one fore and one aft...
s (air bags), in order to maintain the overpressure. Without sufficient overpressure, the blimp loses its ability to be steered and top speed is degraded. The propeller air stream can be used to inflate the hull. In some models, such as the Skyship 600
Skyship 600
The Skyship 600 is a modern airship, originally designed by British company Airship Industries, and now owned and operated by Airship Management Services and Skycruise Switzerland AG.The first Skyship 600 made its maiden flight on 6 March 1984....
, differential ballonet inflation can provide a measure of pitch trim
Flight dynamics
Flight dynamics is the science of air vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are the angles of rotation in three dimensions about the vehicle's center of mass, known as pitch, roll and yaw .Aerospace engineers develop control systems for...
control.
The engines driving the propellers are usually directly attached to the gondola, and in some models are partly steerable.
Blimps are the most commonly built airships, because they are relatively easy to build and easy to transport once deflated. However, because of their unstable hull, their size is limited. A blimp with too long a hull may kink in the middle when the overpressure is insufficient or when maneuvered too fast (this has also happened with semi-rigid airships with weak keels). This led to the development of semi-rigid
Semi-rigid airship
Semi-rigid airships are airships with a partial framework. These often consist of a rigid, or occasionally, flexible, keel frame along the long axis under the aerodynamic hull envelope. The partial framework can also be located inside the hull...
s and rigid airship
Rigid airship
A rigid airship is a type of airship in which the envelope retained its shape by the use of an internal structural framework rather than by being forced into shape by the pressure of the lifting gas within the envelope as used in blimps and semi-rigid airships.Rigid airships were produced and...
s.
Modern blimps launch somewhat heavier than air (overweight), in contrast to historic blimps. The missing lift is provided by lifting the nose and using engine power. Some types also use steerable propellers or ducted fan
Ducted fan
A ducted fan is a propulsion arrangement whereby a fan, which is a type of propeller, is mounted within a cylindrical shroud or duct. The duct reduces losses in thrust from the tip vortices of the fan, and varying the cross-section of the duct allows the designer to advantageously affect the...
s. Operating in a state heavier than air avoids the need to dump ballast
Buoyancy compensator (aviation)
The static buoyancy of airships during a trip is not constant. It is therefore necessary to take measures to control the buoyancy and thus the altitude, the so-called buoyancy compensation.-Changes which have an effect on buoyancy:...
at lift-off and also avoids the need to lose costly lifting gas on landing.
Etymology
Balloon
A balloon is an inflatable flexible bag filled with a gas, such as helium, hydrogen, nitrous oxide, oxygen, or air. Modern balloons can be made from materials such as rubber, latex, polychloroprene, or a nylon fabric, while some early balloons were made of dried animal bladders, such as the pig...
) with a finger. Although there is some disagreement among historians, credit for coining the term is usually given to Lt. A.D. Conningham of the British Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...
in 1915.
A 1943 etymology published in the New York Times confirms the British origin during the First World War when the British were experimenting with lighter-than-air craft. The initial non-rigid aircraft was called the A-limp; and a second version called the B-limp was deemed more satisfactory.
A different derivation is given by Barnes & James in Shorts
Short Brothers
Short Brothers plc is a British aerospace company, usually referred to simply as Shorts, that is now based in Belfast, Northern Ireland. Founded in 1908, Shorts was the first company in the world to make production aircraft and was a manufacturer of flying boats during the 1920s, 1930s, and 1940s...
Aircraft since 1900:
An oft-repeated, but false, etymology is that the United States military initially had two classes of aircraft: A-rigid and B-limp, hence "blimp". In fact,
Use
The B class blimps were patrol airships operated by the United States Navy during and shortly after World War I. The Navy learned a great deal from the DN-1DN-1 (airship)
-See also:...
fiasco. The result was the very successful B-type airships. Dr. Jerome Hunsaker was asked to develop a theory of airship design, Lt. John H. Towers returned from Europe having inspected British designs, the Navy sought bids for 16 blimps from American manufacturers. On 4 February 1917 the Secretary of the Navy directed that 16 nonrigid airships of Class B be procured. [1] Ultimately Goodyear built 9 envelopes, Goodrich built 5 and Curtiss built the gondolas for all of those 14 ships. Connecticut Aircraft contracted with U.S. Rubber for its two envelopes and with Pigeon Fraser for its gondolas. The Curtiss-built gondolas were modified JN-4 fuselages and were powered by OX-5 engines. The Connecticut Aircraft blimps were powered by Hall-Scott engines.
In 1930 a former German airship officer, Captain Anton Heinen, working in the US for the US Navy on it dirigible fleet attempted to design a build a four place blimp called the family air yacht for private fliers which if placed in production the inventor claimed would be priced below $10,000 and easier to fly than a fixed wing aircraft. It was unsuccessful.
Examples of non-rigid airships
There are several blimps worldwide. Some examples include:- TC-3Tc-3The TC-3 and the TC-7 were the two US Army Corps non-rigid blimps used for parasite fighter trials conducted in 1923-24. A single Sperry Messenger biplane was equipped with a skyhook to engage the temporary trapeze mounted to the control carriage of the blimp itself. The first successful docking...
and Tc-7, two US Army Corps non-rigid blimps used for parasite fighter trials during 1923–24. - SSSS class blimpSS class blimps were simple, cheap and easily assembled small non-rigid airships that were developed as a matter of some urgency to counter the German U-boat threat to British shipping during World War I...
, SSPSSP class blimp|-See also:-External links:* *...
, SSTSST class blimp|-See also:-External links:* *...
, SSZSSZ class blimp|-See also:-External links:*...
and NS class blimpNS class blimpThe British NS class blimps were the largest and last in a succession of non-rigid airship designs that served with the Royal Naval Air Service during World War I; developed from experiences gained with earlier classes to operate off the east coast of Britain on long-range patrols...
s, convoy escort blimps used by the UK in World War IWorld War IWorld War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
. - G class blimp and L class blimp, US training blimps built by Goodyear during World War IIWorld War IIWorld War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. - K class blimpK class blimpThe K-class non-rigid airship was a class of blimps built by the Goodyear Aircraft Company of Akron, Ohio for the United States Navy. These blimps were powered by two radial air-cooled engines mounted on outriggers on the side of the control car that hung under the envelope...
and M class blimp, US anti-submarine blimps operated during World War IIWorld War IIWorld War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. - N class blimp (the "Nan ship"), used for anti-submarine and as a radar early-warning platform during the 1950s.
- Goodyear BlimpGoodyear BlimpThe Goodyear Blimp is the collective name for a fleet of blimps operated by Goodyear Tire and Rubber Company for advertising purposes and for use as a television camera platform for aerial views of sporting events...
s, a fleet of blimps operated for advertising purposes and as a television cameraProfessional video cameraA professional video camera is a high-end device for creating electronic moving images...
platform. - Skyship 600Skyship 600The Skyship 600 is a modern airship, originally designed by British company Airship Industries, and now owned and operated by Airship Management Services and Skycruise Switzerland AG.The first Skyship 600 made its maiden flight on 6 March 1984....
, a private blimp used by advertising companies - P-791P-791The Lockheed Martin P-791 is an experimental aerostatic/aerodynamic hybrid airship developed by Lockheed Martin corporation. The first flight of the P-791 was on 31 January 2006 at the company's flight test facility on the Palmdale Air Force Plant 42. It has a unique tri-hull shape, with...
, an experimental aerostatic/aerodynamic hybrid airshipHybrid airship"A hybrid airship is an aircraft that combines characteristics of heavier-than-air technology, fixed-wing aircraft or helicopter, and lighter-than-air , aerostat technology."[1]Examples include helicopter/airship hybrids intended for heavy lift applications and dynamic lift airships intended for...
developed by Lockheed-MartinLockheed MartinLockheed Martin is an American global aerospace, defense, security, and advanced technology company with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It is headquartered in Bethesda, Maryland, in the Washington Metropolitan Area....
corporation. - SVAM CA-80, an airship manufactured by the Shanghai Vantage Airship Manufacture Co in ChinaChinaChinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
External links
- Popular Mechanics, June 1943, "Gas Bags Go On Patrol" detailed article on antisubmarine blimps during World War Two
- "How The First Sea-Air Rescue Was Made", October 1944, Popular Science first air-to-sea rescue without aircraft landing first