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Buoyancy compensator (aviation)
Encyclopedia
The static buoyancy
of airship
s 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.
For example, the LZ 126
spent on the flight from Friedrichshafen to Lakehurst 23,000 kg gasoline and 1300 kg of oil (an average consumption of 290 kg/100 km). During the landing the airship had to release approximately 24,000 cubic meters of hydrogen to balance the ship to land it. An airship with the size of the LZ 129 Hindenburg
spent on a flight from Frankfurt am Main to Lakehurst approximately 54 tonne
s of diesel with a buoyancy equivalent of 48,000 cubic metres hydrogen which amounted for about a quarter of the used lifting gas at the start of the flight (200,000 cubic metres). After landing the jettisoned hydrogen was replaced with new hydrogen.
The Zeppelin NT
has no special facilities to offset the extra buoyancy by fuel consumption. Compensation takes place by using a start-weight that is higher than the buoyancy lifting level at the start and during the flight, the extra dynamic buoyancy needed for lift-off and flight is produced with engines. If during the trip the ship gets lighter than air caused by fuel consumption, the swivel
engines are used for down pressure and landing. The relatively small size of the Zeppelin NT and a range of "only" 900 kilometers compared to the historical Zeppelins allowed the waiver of a ballast extraction device.
and LZ 129
to use part of the lifting gas as a propellant
without much success, later ships filled with helium lacked the option.
was a common propellant for airships, it is named after its inventor the Augsburg
er chemist Hermann Blau
who produced it in the Augsburger Blau gas plant. Various sources mention a mixture of liquefied
propane
and butane
. In density it was 9% heavier than air. The Zeppelins used a different gas mixture of propylene
, methane
, butane, acetylene (ethine), butylene and hydrogen.
The LZ 127 Graf Zeppelin
had bi-fuel engines and could use gasoline
and gas as a propellant. Twelve of the gas cells were filled with a propellant gas instead of lifting gas with a total volume of 30,000 cubic metres, enough for approximately 100 flight hours.
The fuel tank
had a gasoline volume of 67 flight hours. Using both gasoline and Blau gas could give 118 hours cruise.
and LZ 129 Hindenburg
rain gutter
s were attached to the trunk to collect rainwater to fill the ballast water tanks during the trip. However, this procedure is weather dependent and is therefore not reliable as a standalone measure.
described how during World War I
Zeppelins would land on the sea and pick up temporary ballast water. In 1921 the airships LZ 120 "Bodensee" and LZ 121 "Nordstern" tested the possibility on Lake Constance
to use lake water to create ballast. These attempts, however, showed no satisfactory results.
method was tested on the LZ 129 to extract water from the humid air to increase weight. The project was terminated.
The most promising procedure for ballast extraction during the journey is condensation
of exhaust gas
ses from the engines which consist mainly of water (steam) and carbon dioxide. The main factors affecting gainable water are the hydrogen content of the fuel and humidity. The necessary exhaust gas coolers for this method had repeated problems with corrosion in the early years.
The first trials on the DELAG -Zeppelin LZ 13 "Hansa"
(1912–1916) were conducted by Wilhelm Maybach
. The trials were not satisfactory, resulting in an abandoned project.
The United States Navy
reports the USS Shenandoah (ZR-1)
(1923–25), a helium-filled rigid airship, as the first airship with ballast water from the condensation of exhaust gas. The LZ 126/ZR-3
USS Los Angeles was refitted with helium as a lifting gas after arrival in the U.S. Exhaust gas coolers were used to prevent jettisoning of the costly helium.
Buoyancy
In physics, buoyancy is a force exerted by a fluid that opposes an object's weight. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus a column of fluid, or an object submerged in the fluid, experiences greater pressure at the bottom of the...
of airship
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...
s 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
- Changes in air temperature (and thus the density of air)
- Changes in the lifting gasLifting gasBecause 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 :...
temperature (for example by heating of the hull by the sun). - Accumulation of additional ballast (for example, precipitation or icing on the envelope)
- Changes in ballast (for example, during a flight maneuver or the dropping of ballast)
- Changes by consumption of fuel, especially in the large historic airships like the ZeppelinZeppelinA 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...
s the problem of change in the buoyancy balance by consumption of fuel needed attention.
For example, the LZ 126
USS Los Angeles (ZR-3)
The second USS Los Angeles was a rigid airship, designated ZR-3, that was built in 1923-1924 by the Zeppelin factory in Friedrichshafen, Germany, where it was originally designated LZ-126...
spent on the flight from Friedrichshafen to Lakehurst 23,000 kg gasoline and 1300 kg of oil (an average consumption of 290 kg/100 km). During the landing the airship had to release approximately 24,000 cubic meters of hydrogen to balance the ship to land it. An airship with the size of the LZ 129 Hindenburg
LZ 129 Hindenburg
LZ 129 Hindenburg was a large German commercial passenger-carrying rigid airship, the lead ship of the Hindenburg class, the longest class of flying machine and the largest airship by envelope volume...
spent on a flight from Frankfurt am Main to Lakehurst approximately 54 tonne
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...
s of diesel with a buoyancy equivalent of 48,000 cubic metres hydrogen which amounted for about a quarter of the used lifting gas at the start of the flight (200,000 cubic metres). After landing the jettisoned hydrogen was replaced with new hydrogen.
Compensation measures
- Particular use of the dynamic buoyancy, see liftLift (force)A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...
and dragDrag (physics)In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...
. - Increasing buoyancy by dropping ballastBallast-Objects:* Ballast tank, a device used on ships and submarines and other submersibles to control buoyancy and stability* Ballast weights, metallic plates used to bring auto racing vehicles up to the minimum mandated weight...
. This is done mostly by the jettisoning of ballast water similar to the dropping of sandbags in ballooningBalloon (aircraft)A balloon is a type of aircraft that remains aloft due to its buoyancy. A balloon travels by moving with the wind. It is distinct from an airship, which is a buoyant aircraft that can be propelled through the air in a controlled manner....
. - The reduction of buoyancy by jettisoning liftgas or adding ballast.
- Changing the density of the lifting gas by heating (more buoyancy) or coolingCoolingCooling is the transfer of thermal energy via thermal radiation, heat conduction or convection. It may also refer to:-Techniques:* Air conditioning* Air cooling* Computer cooling* Cryogenics* Conduction * Infrared solar cells* Laser cooling...
(less buoyancy). - The use of vacuum/air buoyancy compensator tanks
- The use of thrust vectoringThrust vectoringThrust vectoring, also thrust vector control or TVC, is the ability of an aircraft, rocket or other vehicle to manipulate the direction of the thrust from its engine or motor in order to control the attitude or angular velocity of the vehicle....
using ducted fans or propellers.
The Zeppelin NT
Zeppelin NT
The Zeppelin NT is a class of airships being manufactured since the 1990s by the German company Zeppelin Luftschifftechnik GmbH in Friedrichshafen. The initial model is the NT07...
has no special facilities to offset the extra buoyancy by fuel consumption. Compensation takes place by using a start-weight that is higher than the buoyancy lifting level at the start and during the flight, the extra dynamic buoyancy needed for lift-off and flight is produced with engines. If during the trip the ship gets lighter than air caused by fuel consumption, the swivel
Swivel
A swivel is a connection that allows the connected object, such as a gun or chair, to rotate horizontally and/or vertically. A common design for a swivel is a cylindrical rod that can turn freely within a support structure. The rod is usually prevented from slipping out by a nut, washer or...
engines are used for down pressure and landing. The relatively small size of the Zeppelin NT and a range of "only" 900 kilometers compared to the historical Zeppelins allowed the waiver of a ballast extraction device.
Buoyancy compensation
With a Zeppelin two main strategies are pursued to avoid the jettisoning of lifting gas:- 1. The use of a fuel with the same density as air and therefore no increase in buoyancy caused by consumption.
- 2. Adding water as ballast by extraction during the trip.
Hydrogen
Different attempts were made on hydrogen airships, like the LZ 127LZ 127 Graf Zeppelin
LZ 127 Graf Zeppelin was a German built and operated passenger-carrying hydrogen-filled rigid airship which operated commercially from 1928 to 1937. It was named after the German pioneer of airships, Ferdinand von Zeppelin, who was a Graf or Count in the German nobility. During its operating life,...
and LZ 129
LZ 129 Hindenburg
LZ 129 Hindenburg was a large German commercial passenger-carrying rigid airship, the lead ship of the Hindenburg class, the longest class of flying machine and the largest airship by envelope volume...
to use part of the lifting gas as a propellant
Propellant
A propellant is a material that produces pressurized gas that:* can be directed through a nozzle, thereby producing thrust ;...
without much success, later ships filled with helium lacked the option.
Blaugas
Around 1905 Blau gasBlau gas
Blau gas was an artificial illuminating gas similar to propane, named after its inventor, Dr. Hermann Blau of Augsburg, Germany. It was manufactured by decomposing mineral oils in retorts by heat and compressing the resulting naphtha until it liquefied. It was transported in this condition, and...
was a common propellant for airships, it is named after its inventor the Augsburg
Augsburg
Augsburg is a city in the south-west of Bavaria, Germany. It is a university town and home of the Regierungsbezirk Schwaben and the Bezirk Schwaben. Augsburg is an urban district and home to the institutions of the Landkreis Augsburg. It is, as of 2008, the third-largest city in Bavaria with a...
er chemist Hermann Blau
Hermann Blau
Hermann Blau was a German engineer and chemist, and inventor of Blau gas.Blau, a student of the Nobel Prize winning chemist Adolf von Baeyer was originally a pharmacist but devoted himself in later life entirely to chemistry...
who produced it in the Augsburger Blau gas plant. Various sources mention a mixture of liquefied
Liquid gas
Due to the age of this content, you may be looking for:*Liquefaction of gases*liquid oxygen*liquid nitrogen*Liquid hydrogen*Liquid helium*paramagnetism *superconducting metals*ferromagnetism *liquified petroleum gas...
propane
Propane
Propane is a three-carbon alkane with the molecular formula , normally a gas, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as a fuel for engines, oxy-gas torches, barbecues, portable stoves, and residential central...
and butane
Butane
Butane is a gas with the formula C4H10 that is an alkane with four carbon atoms. The term may refer to any of two structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, butane refers only to the unbranched n-butane isomer; the other one being called "methylpropane" or...
. In density it was 9% heavier than air. The Zeppelins used a different gas mixture of propylene
Propylene
Propene, also known as propylene or methylethylene, is an unsaturated organic compound having the chemical formula C3H6. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons, and it is also second in natural abundance.-Properties:At room temperature and...
, methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
, butane, acetylene (ethine), butylene and hydrogen.
The LZ 127 Graf Zeppelin
LZ 127 Graf Zeppelin
LZ 127 Graf Zeppelin was a German built and operated passenger-carrying hydrogen-filled rigid airship which operated commercially from 1928 to 1937. It was named after the German pioneer of airships, Ferdinand von Zeppelin, who was a Graf or Count in the German nobility. During its operating life,...
had bi-fuel engines and could use gasoline
Gasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...
and gas as a propellant. Twelve of the gas cells were filled with a propellant gas instead of lifting gas with a total volume of 30,000 cubic metres, enough for approximately 100 flight hours.
The fuel tank
Fuel tank
A fuel tank is safe container for flammable fluids. Though any storage tank for fuel may be so called, the term is typically applied to part of an engine system in which the fuel is stored and propelled or released into an engine...
had a gasoline volume of 67 flight hours. Using both gasoline and Blau gas could give 118 hours cruise.
Dew and rainfall on the hull
In the airships LZ 127 Graf ZeppelinLZ 127 Graf Zeppelin
LZ 127 Graf Zeppelin was a German built and operated passenger-carrying hydrogen-filled rigid airship which operated commercially from 1928 to 1937. It was named after the German pioneer of airships, Ferdinand von Zeppelin, who was a Graf or Count in the German nobility. During its operating life,...
and LZ 129 Hindenburg
LZ 129 Hindenburg
LZ 129 Hindenburg was a large German commercial passenger-carrying rigid airship, the lead ship of the Hindenburg class, the longest class of flying machine and the largest airship by envelope volume...
rain gutter
Rain gutter
A rain gutter is a narrow channel, or trough, forming the component of a roof system which collects and diverts rainwater shed by the roof....
s were attached to the trunk to collect rainwater to fill the ballast water tanks during the trip. However, this procedure is weather dependent and is therefore not reliable as a standalone measure.
Water from the ground
Captain Ernst A. LehmannErnst A. Lehmann
Captain Ernst August Lehmann was a German Zeppelin captain. He was one of the most famous and experienced figures in German airship travel.- Pre-war experience :...
described how during World War I
World War I
World 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...
Zeppelins would land on the sea and pick up temporary ballast water. In 1921 the airships LZ 120 "Bodensee" and LZ 121 "Nordstern" tested the possibility on Lake Constance
Lake Constance
Lake Constance is a lake on the Rhine at the northern foot of the Alps, and consists of three bodies of water: the Obersee , the Untersee , and a connecting stretch of the Rhine, called the Seerhein.The lake is situated in Germany, Switzerland and Austria near the Alps...
to use lake water to create ballast. These attempts, however, showed no satisfactory results.
Silica-gel method
The silica gelSilica gel
Silica gel is a granular, vitreous, porous form of silica made synthetically from sodium silicate. Despite its name, silica gel is a solid. It is a naturally occurring mineral that is purified and processed into either granular or beaded form...
method was tested on the LZ 129 to extract water from the humid air to increase weight. The project was terminated.
Water from fuel combustion
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
of exhaust gas
Exhaust gas
Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline/petrol, diesel fuel, fuel oil or coal. According to the type of engine, it is discharged into the atmosphere through an exhaust pipe, flue gas stack or propelling nozzle.It often disperses...
ses from the engines which consist mainly of water (steam) and carbon dioxide. The main factors affecting gainable water are the hydrogen content of the fuel and humidity. The necessary exhaust gas coolers for this method had repeated problems with corrosion in the early years.
The first trials on the DELAG -Zeppelin LZ 13 "Hansa"
Zeppelin LZ13
The Zeppelin LZ 13 Hansa was a German civilian rigid airship first flown in 1912 with a volume of 18,700 cubic metres. It was first operated by DELAG to carry passengers and post and flew the first scheduled international passenger flights...
(1912–1916) were conducted by Wilhelm Maybach
Wilhelm Maybach
Wilhelm Maybach was an early German engine designer and industrialist. During the 1890s he was hailed in France, then the world centre for car production, as the "King of constructors"....
. The trials were not satisfactory, resulting in an abandoned project.
The United States Navy
United States Navy
The United States Navy is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. The U.S. Navy is the largest in the world; its battle fleet tonnage is greater than that of the next 13 largest navies combined. The U.S...
reports the USS Shenandoah (ZR-1)
USS Shenandoah (ZR-1)
USS Shenandoah was the first of four United States Navy rigid airships. It was built in 1922-1923 at Lakehurst Naval Air Station, and first flew in September 1923. It developed the Navy's experience with rigid airships, even making the first crossing of North America by airship...
(1923–25), a helium-filled rigid airship, as the first airship with ballast water from the condensation of exhaust gas. The LZ 126/ZR-3
USS Los Angeles (ZR-3)
The second USS Los Angeles was a rigid airship, designated ZR-3, that was built in 1923-1924 by the Zeppelin factory in Friedrichshafen, Germany, where it was originally designated LZ-126...
USS Los Angeles was refitted with helium as a lifting gas after arrival in the U.S. Exhaust gas coolers were used to prevent jettisoning of the costly helium.