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Buoyancy

Buoyancy

In physics, buoyancy is an upward force on an object immersed in a fluid (i.e. a liquid or a gas), enabling it to float or at least to appear to become lighter. If the buoyancy exceeds the weight, then the object floats; if the weight exceeds the buoyancy, the object sinks. If the buoyancy equals the weight, the body has neutral buoyancy and may remain at its level. If its compressibility is less than that of the surrounding fluid, it is in stable equilibrium and will, indeed, remain at rest, but if its compressibility is greater, its equilibrium is unstable, and it will rise and expand on the slightest upward perturbation, but fall and compress on the slightest downward perturbation. It was the ancient Greek, Archimedes of Syracuse, who first discovered the law of buoyancy, sometimes called Archimedes' principle: :The buoyant force is equal to the weight of the displaced fluid. Typically, the weight of the displaced fluid is directly proportional to the volume of their displaced fluid (Specifically if the surrounding fluid is of uniform density.) Thus, among objects with equal masses, the one with greater volume has greater buoyancy. Suppose a rock's weight is measured at 10 Newtons when suspended by a string in a vacuum. Suppose that when the rock is lowered by the string into water, it displaces water whose weight is 3 Newtons. The force it then exerts on the string from which it hangs will be 10 Newtons minus the 3 Newtons of buoyant force: 10 - 3 = 7 Newtons. Buoyancy is the underlying principle of many vehicles such as boats, ships, balloons, and airships.

Density

If the weight of an object is less than the weight of the fluid that the object would displace if it was fully submerged, then the object is less dense than the fluid and it floats at a level so it displaces the same weight of fluid as the weight of the object. An object made of a material of higher density than the fluid, e.g. a metal object in water, can still float if it has a suitable shape (e.g. a hollow which is open upwards or downwards) that keeps a large enough volume of air below the surface level of the fluid. In that case, for the average density mentioned above, the air is included also, which may reduce this density to less than that of the fluid.

Acceleration and energy

Although Archimedes' principle gives the force on a buoyant object, this does not determine the related acceleration of the object in the usual way over Newton's first law. This is for two reasons: Not only has the mass of the object to be accelerated but also the mass of the displaced fluid. One can compare the situation to a scale, where the weight on one side is given by the object, and the weight on the other side by the displaced fluid element. Depending on which of the two is heavier, one side of the scale will drop and the other rise, but since both sides are rigidly connected, both masses have to be accelerated together at the same rate (albeit in opposite directions). The second reason is that viscosity dissipates energy, so that, even taking into account the kinetic and potential energies of the object and the fluid (but ignoring heat energy), energy is lost to viscosity, a form of friction. It is obvious that without taking the displaced fluid element into account, energy would not be conserved during the buoyant motion of an object as it would gain both potential and kinetic energy when rising in the fluid.

Fluid

A subset of the phases of matter, fluids include liquids, gases, plasmas and, to some extent, plastic solids. Fluids share the properties of not resisting deformation and the ability to flow (also described as their ability to take on the shape of their containers). These properties are typically a function of their inability to support a shear stress in static equilibrium. While in a solid, stress is a function of strain, in a fluid stress is a function of rate of strain. A consequence of this behaviour is Pascal's law which entails the important role of pressure in characterising a fluid's state. Fluids can be characterised as:
- Newtonian fluids; or
- Non-Newtonian fluids, - depending on the way stress depends on strain and its derivatives. The behaviour of fluids is described by a set of partial differential equations, including the Navier-Stokes equations. Fluids are also divided into liquids and gases. Liquids form a free surface (that is, a surface not created by their container) while gases do not. The distinction between solids and fluids is not so obvious. The distinction is made by evaluating the viscosity of the matter: for example Silly Putty can be considered either a solid or a fluid, depending on the time period over which it is observed. The study of fluids is fluid mechanics which is then subdivided into fluid dynamics and fluid statics depending on whether the fluid is in motion or not.

Liquid

A liquid (a phase of matter) is a fluid whose volume is fixed under conditions of constant temperature and pressure; and, whose shape is usually determined by the container it fills. Furthermore, liquids exert pressure on the sides of a container as well as on anything within the liquid itself; this pressure is transmitted undiminished in all directions. If a liquid is at rest in a uniform gravitational field, the pressure

p

at any point is given by :

p=\rho gz

where

\rho

is the density of the liquid (assumed constant) and

z

is the depth of the point below the surface. Note that this formula assumes that the pressure at the free surface is zero, and that surface tension effects may be neglected. Liquids have traits of surface tension and capillarity; they generally expand when heated, and contract when cooled. Objects immersed in liquids are subject to the phenomenon of buoyancy. Liquids at their respective boiling point change to gases, and at their freezing points, change to a solids. Via fractional distillation, liquids can be separated from one another as they vaporise at their own individual boiling points. Cohesion between molecules of liquid is insufficient to prevent those at free surface from evaporating. It should be noted that glass at normal temperatures is not a "supercooled liquid", but a solid. See the article on glass for more details.

Weight

:See also weight function. For the 1994 album by the group Rollins Band, see Weight (album). In the physical sciences, weight is the interaction of matter with a gravitational field. It is equal to the mass of the object multiplied by the magnitude of the gravitational field. The word weight entered Old English sometime around the 9th century, and meant the quantity measured with a balance -- the same as mass in both common and scientific usage. In common usage, weight still means the same as mass.

Weight and mass

"Weight" is often used as a synonym for mass. For instance, when we buy or sell goods "by weight", we are interested in the amount of goods exchanged, not how hard it presses down on the table. Similarly, in measurements of body weight we are primarily interested in the amount of tissue (fat, muscle, etc.) present. Correspondingly, weight is often given in kilograms and other units of mass. In the physical sciences, people usually distinguish between weight and mass. Under most circumstances, this ambiguity is not a problem, because the weight of an object is directly proportional to its mass, and the constant of proportionality -- the strength of the gravitational field -- is approximately constant everywhere on the surface of the Earth (around 9.8 m/s²). For instance, a body will exert less force if it is located on the Moon than if it is on the Earth, since the gravitational field of the Moon is weaker; its mass, on the other hand, does not depend on position. Although terms such as "atomic weight", "molecular weight", and "formula weight" may still be encountered, such usage is often discouraged; terms like atomic mass are used instead. Mass is measured using a balance which compares an item in question to matter of known mass; this method is independent of gravity. Alternately, a spring scale or Hydraulic or pneumatic scale is used to measure force (which physicists call weight). Most scales measure weight using a spring. Related to the historical identification of mass and weight, the pound has been used both as a unit of mass and as a unit of force. In the United States, United Kingdom, and elsewhere, the pound is and always has been officially defined as a unit of mass. The corresponding force is called a pound-force, and similarly the weight of a kilogram of material on Earth is called a kilogram-force. However, the use of pounds to measure forces is still common in engineering, and it occurs in derived units like p.s.i. (pounds per square inch). In most countries, scientists have adopted SI units, which use kilogram for mass and newton for force non-interchangeably.

Weight as a force

The SI unit for weight is the newton (N), or kilogram metres per second squared (kg m s⁻²). The weight force that we sense is actually the normal force exerted by the surface we stand on, which prevents us from being pulled to the center of the Earth, and not the weight itself. This normal force, that we can call the apparent weight is the one that is measured by a weighing scale, not the weight itself. A good evidence of this is given by the fact that a person moving up and down on his toes does see the indicator moving, telling that the measured force is changing while his weight, that depends only on his mass, the Earth mass and the distance between his center of mass and the center of Earth obviously do not change. In contrast, in free-fall, there is no apparent weight because we are not in contact with any surface to provide such a normal force. The experience of having no apparent weight is known as weightlessness or microgravity.

Comparative weights on bodies of the solar system

The following is a list of the weights of a mass on some of the bodies in the solar system, relative to its weight on Earth: For weight variations on Earth, see gee, physical geodesy and gravity anomaly.

Human weight in the medical sciences and ordinary language

Although many people prefer the less-ambiguous term body mass to body weight, the term weight is overwhelmingly used in daily English speech and in biological and medical science contexts. Body weight is measured in kilograms throughout the world. Most hospitals in the United States use kilograms for calculations, but use kilograms and pounds simultaneously for other purposes (a pound is 0.45 kg). Many people in the United Kingdom still measure their weight using the stone equal to 14 lb (6.35 kg).

Sports usage

Participants in sports such as boxing, wrestling, judo, and weight-lifting are classified according to their body weight, measured in units of mass such as pounds or kilograms. See, e.g., wrestling weight classes, boxing weight classes, judo at the 2004 Summer Olympics, boxing at the 2004 Summer Olympics. In horse racing, weight is used to handicap horses. A weight also refers to the physical objects used in weight-lifting and other sports such as the hammer throw.

Unstable

Instability in systems is generally characterized by some of the outputs or internal states growing without bounds. Not all systems that are not stable are unstable; systems can also be marginally stable or exhibit limit cycle behavior. In control theory, a system is unstable if any of the roots of its S-function has real part greater than zero. This is equivalent to any of the eigenvalues of the state matrix having real part greater than zero. In structural engineering, a structure can become unstable when excessive load is applied. Beyond a certain threshold, structural deflections magnify stresses, which in turn increases deflections. This is can take the form of buckling or crippling. The general field of study is called structural stability.

Fluid instabilities

Fluid instabilities occur in liquids, gases and plasmas, and are often characterised by the shape that form; they are studied in fluid dynamics and magnetohydrodynamics. Fluid instabilities include:
- Ballooning mode instability (some analogy to the Rayleigh-Taylor instability); found in the magnetosphere
- Baroclinic Instability
- Benard Instability
- Drift mirror instability
- Kelvin-Helmholtz instability (similar, but different to the diocotron instability in plasmas)
- Rayleigh-Taylor instability

Plasma instabilities

Plasma instabilities can be divided into two general groups (1) hydrodynamic instabilities (2) kinetic instabilities.
- Bennett pinch instability (also called the z-pinch instability )
- Beam acoustic instability
- Bump-in-tail instability
- Buneman instability (same as Farley-Buneman instability?)
- Cherenkov instability
- Chute instability
- Coalescence instability
- Collapse instability
- Counter-streaming instability
- Cyclotron instabilities, including: :
- Alfven cyclotron instability :
- Electron cyclotron instability :
- Electrostatic ion cyclotron Instability :
- Ion cyclotron instability :
- Magnetoacoustic cyclotron instability :
- Protron cyclotron instability :
- Nonresonant Beam-Type cyclotron instability :
- Relativistic ion cyclotron instability :
- Whistler cyclotron instability
- Diocotron instability (similar to, but different to the Kelvin-Helmholtz instability).
- Disruptive instability (in tokamaks)
- Double emission instability
- Drift wave instability
- Farley-Buneman instability
- Fan instability
- Filamentation instability
- Firehose instability (also called Hose instability)
- Flute instability
- Free electron maser instability
- Gyrotron instability
- Helical instability (helix instability)
- Helical kink instability
- Hose instability (also called Firehose instability)
- Interchange instability
- Ion beam instability
- Kink instability
- Lower hybrid (drift) instability (in the Critical ionization velocity mechanism)
- Magnetic drift instability
- Modulation instability
- Non-Abelian instability
- Non-linear coalescence instability
- Oscillating two stream instability, see two stream instability
- Pair instability
- Parker instability
- Pinch instability
- Sausage instability
- Slow Drift Instability
- Tearing mode instability
- Two stream instability
- Weak beam instability
- Weibel instability
- z-pinch instability, also called Bennett pinch instability

External links

- [http://www.efluids.com/efluids/pages/gallery.htm eFluids Fluid Flow Image Gallery] Category:Control theory Category:Systems theory

Syracuse, Italy

. Map also shows mainland Italy, Tunisia, and the islands Sardinia and Corsica.]] Syracuse (Italian Siracusa; ancient Syracusa; see also List of traditional Greek place names) is a city on the eastern coast of Sicily and the capital of the province of Syracuse, Italy. Once described by Cicero as "the greatest Greek city and the most beautiful of them all", the ancient core of Syracuse is part of the UNESCO World Heritage List.

History

Syracuse was founded in 734 BC by Greek settlers from Corinth, who called it Sirako ("swamp"). The settlers found the land to be fertile and the native tribes to be reasonably well-disposed to their presence. The city grew and prospered, and for some time stood as the most powerful Greek city anywhere in the Mediterranean. In the 5th century BC Syracuse came to be ruled by tyrants, who ruled until 211 BC, with some interruptions. In the late 5th century, Syracuse found itself at war with Athens, which sought more resources to fight the Peloponnesian War. The Syracusans enlisted the aid of a general from Sparta, Athens' foe in the war, to defeat the Athenians, destroy their ships, and leave them to starve on the island (see Sicilian Expedition). In 401 BC, Syracuse contributed a force of 3000 hoplites and a general to Cyrus the Younger's Army of the Ten Thousand. Not long after, in the early 4th century BC, the tyrant Dionysius managed to fight a war against Carthage and keep that power from capturing the whole of Sicily. Carthage Perhaps the most famous Syracusan was the natural philosopher Archimedes. Among his many inventions were various military engines including the claw of Archimedes, used to resist a Roman siege. The city held out for three years, but fell in 212 BC to Marcus Claudius Marcellus. Another siege in AD 878 inaugurated two centuries of Muslim rule. In 1085 the Normans followed and in 1194 Henry VI of Swabia occupied Syracuse. Under Frederick II the city and the whole of Sicily flourished again. In the struggle between the Anjou and Aragonese monarchies, Syracuse sided with the Aragonese and defeated the Anjou in 1298, receiving from the Spanish sovereigns great privileges in reward. The city in the following centuries was struck by two ruinous earthquakes in 1542 and 1693, and in 1729 by a plague. More destruction was caused by the Allied and the German bombings in 1943. Syracuse today has about 125,000 inhabitants and numerous attractions for the visitor interested in historical sites (such as the Ear of Dionysius). Nearby places of note include Catania, Noto, Modica and Ragusa.

Namesakes

External links

- [http://www.italianvisits.com/sicily/siracusa/ ItalianVisits.com] Category:Ancient Roman enemies and allies Category:World Heritage Sites in Italy Category:Coastal cities Category:Colonies of Magna Graecia Category:Corinthian colonies Category:Cities in Sicily Category:Sicilian Baroque ko:시라쿠사 ja:シラクサ nb:Siracusa

Vehicle

:This article is about the means of transport. For the political meaning, see electoral vehicle. For the economical meaning, see economic vehicle Vehicles are non-living means of transportation. They are most often man-made (e.g. cars, motorcycles, trains, ships, and aircraft), although some other means of transportation which are not made by man can also be called vehicles; examples include icebergs and floating tree trunks. Vehicles may be propelled by animals, e.g. a chariot or an ox-cart. However, animals on their own, though used as a means of transportation, are not called vehicles. This includes humans carrying another human, for example a child or a disabled person. Most land vehicles have wheels. Please see the wheel article for examples of vehicles with and without wheels. Movement without the help of a vehicle or an animal is called locomotion. The word vehicle itself comes from the Latin vehiculum. AVL stands for Automatic Vehicle Location.

Types of vehicles

- Aircraft
- Cars
- Auto rickshaws
- Boats
- Buses
- Coaches
- Motorcycles
- Trains
- Ships
- Vans
- Bicycles
- More...

External Links

- [http://www.epa.gov/greenvehicles/ Green Vehicle Guide]
- [http://www.nhtsa.dot.gov/cars Vehicle Information] Category:Transportation simple:Vehicle

Boat

A boat is a watercraft, usually smaller than most ships. Some boats are commonly carried by a ship or on land using trailers. A boat consists of one or more buoyancy structures called hulls and some system of propulsion, such as a screw, oars, paddles, a setting pole, a sail, paddlewheels or a water jet.

Parts of a Boat

The roughly horizontal but cambered structures spanning the hull of the boat are referred to as the "deck". In a ship, there would be several but a boat is unlikely to have more than one. The similar but usually lighter structure which spans a raised cabin is a coarch-roof. The "floor" of a cabin is properly known as the sole but is more likely to be called the floor. (A floor is properly, a structural member which ties a frame to the keelson and keel.) The underside of a deck is the deck head. The vertical surfaces dividing the internal space are "bulkheads". Some are important parts of the vessel's structure. The front of a boat is called the bow or prow. The rear of the boat is called the stern. The right side is starboard and the left side is port. It is somewhat risible in modern practice to call the command area of a large boat the "bridge". It is the cockpit or wheelhouse, depending on its design. The compartments housing a toilet, and the toilet itself, are known as the "heads", and a trip to this area is a "head call". In the old days, cordage intended for the delicate hands of a yacht's owner was of linen, later cotton. Therefore cordage used to control a sailing boat, tends to be referred to as "line" rather than rope. Most have specific names, but in general, lines used for raising things like sails and flags are "halyards" while the principal ones for adjusting the positions of the sails are called "sheets". All the lines and wire collectively are referred to as "rigging". That which is set up in the yard and left is standing rigging. That which is adjustable in use is running rigging. For example, a forestay is standing rigging and a sheet or a halyard is part of the running rigging.

Types of Boats

water jet
- Bangca
- Bateau
- Barge
- Cabin Cruiser
- Canoe
- Catamaran
- Cape Islander
- Catboat
- Coracle
- Cruiser
- Cutter
- Dhow
- Dinghy
- Dory
- Durham Boat
- Dutch Barge
- Felucca
- Ferry
- Folding boat
- Go-fast boat
- Gondola
- Houseboat
- Inflatable boat Inflatable boat]
- Jetboat, Jetski
- Jonsboat
- Junk
- Kayak
- Ketch
- Lifeboat
- Log boat
- Luxemotor
- Motorboat
- Narrowboat
- Norfolk wherry
- Outrigger canoe
- Padded V-hull
- Pinnace
- Pirogue
- Powerboat Powerboat
- Raft
- Rigid-hulled inflatable boat (RIB)
- Rowboat, rowing boat
- Sailboat, sailing boat
- Sampan
- Schooner
- Scow
- Sharpie
- Skiff
- Sloop
- Submarine
- Swift boat
- Tjalk
- Trimaran
- Tugboat
- U-boat
- Water taxi
- Whaleboat
- Yacht
- Yawl Yawl

Unusual types of boats

Unusual floating vehicles have been used for sports purposes as well. For example, the Bathtub Boat is used in "bathtub races" in many cities, although it originated in Nanaimo, BC, Canada.

Unusual uses of the word "Boat"

- Often in rowing as a racing-type competitive sport, "boat" means the crew and "shell" means the craft. So a university might refer to its first boat, meaning the rowers who make up their best team, rather than their best piece of equipment.
- A submarine is generally referred to as a boat rather than a ship. This dates from the early days of submarine warfare, when submarines were essentially motor torpedo boats which could submerge. In the modern combat environment where a typical attack submarine is the size of a destroyer and equipped with either a nuclear reactor or air independent propulsion which can allow it to stay submerged for months or weeks (and boomers are even larger, on the order of old-style battleships), this use is something of an anachronism.
- A ship can be informally known as a boat, especially by its crew. This use is uncommon in the case of a warship.
- In Great Lakes shipping, "boat" refers to any vessel, even one which would normally be considered a "ship" on the ocean.
- In some versions of cockney rhyming slang, "boat" means face, from "boat race".
- The term "gravy boat" is used to describe a small jug used to dispense meat gravy at the dining table. Similarly: "sauce boat".
- A boat can also be one of the massive cars manufactured in America from the 1950s through the 1970s.
- A boat, short for full-boat is another term for a full-house in the card game poker.

External links

- [http://www.boatingdir.com Boating Directory]
- [http://www.cronab.demon.co.uk/china.htm The Rise and Fall of 15th Century Chinese Seapower]
- [http://www.barges.org DBA - Dutch Barge Association] Living aboard ex-commercial barges or any other type of broad-beam inland waterways craft Category:Vehicles Category:Water transport
- ja:船 simple:Boat

Balloon

::For the impedance converter, see the article on balun. baluns.]] A balloon is a flexible bag normally filled with air or gas. Some balloons are purely decorative, others are used for specific purposes. Early balloons were made of dried animal bladders. Modern balloons can be made from materials such as rubber, latex, chloroprene or a nylon fabric.

Usage of Balloons

- small balloons (volume of a few litres)
- toy balloon
- decoration
- solar balloon
- balloon mail as part of a balloon flight competition or to spread information
- Balloon helicopter
- Demonstration of rocket propulsion by letting the gas stream away (balloon rocket)
- Ceiling balloon
- medium balloons (volume of hundreds to thousands of litres)
- transport of bombs (in World War II, FUGU-Balloon)
- transport of propaganda (in World War II and in the Cold War)
- Ceiling balloon
- Weather balloon used with a Radiosonde
- as fixed balloon
- for carrying advertising signs
- to carry antennae for LF and VLF
- party balloon
- large balloons (volume up to 12000 cubic metres)
- fixed balloon
- as manned observation post (before World War II)
- barrage balloon
- observation balloon for military reconnaissance
- positioning atomic bombs for bomb tests in the atmosphere
- free flying balloons
- lifting people, usually with a hot air balloon
- airship actually a buoyant aircraft rather than a balloon
- research balloon with instrumentation, also to carry telescopes
- rockoon
- balloon satellite for space research.
- espionage balloon for military reconnaissance espionage balloon

Balloons as flying machines

Large balloons filled with hot air or buoyant gas have been used as flying machines since the 18th century. See Balloon (aircraft) and Hot air balloon Such balloons, which lift a payload using buoyancy, should not be confused with balloons in space, launched with a rocket, which are simply large deployable structures. Balloons are sometimes used in form of a rockoon as carrier for rockets. Examples:
- Echo satellite
- Decoys accompanying ICBMs in midcourse, see also countermeasure

Balloons as decoration or entertainment

countermeasure Party balloons are mostly made of natural latex tapped from rubber trees and can be filled with air, helium, water, or any other suitable liquid or gas. The rubber makes the volume adjustable. Filling with air is done with the mouth or with a pump. When rubber balloons are filled with helium so that they float (restrained by ribbons or strings) they can hold their shape for only a few hours. The enclosed air or helium escapes through small pores in the rubber. If helium is used the gas escapes quicker than in the case of air because the helium atoms are much smaller than the nitrogen and oxygen molecules in air. Even a perfect rubber membrane eventually loses the gas to the outside, and its contents are contaminated by oxygen and nitrogen migrating inward from the outside. The gases in question actually dissolve in the rubber on one side and are released from solution on the other. The process by which a substance or solute migrates from a region of high concentration, through a barrier or membrane, to a region of lower concentration is called diffusion. The inside of balloons can be treated with a special gel (e.g. "Hi Float" brand) which coats the inside of the balloon to reduce the helium leakage, thus increasing float time. Latex rubber balloons are completely biodegradable, but cannot safely be released into the environment: they are a serious hazard to birds and wetland animals that confuse the balloons for food. Beginning in the early 1990s, some more expensive (and longer-lasting) helium balloons have been made of thin, unstretchable, impermeable metallized nylon films. These balloons are often mistakenly called Mylar balloons. These balloons have attractive shiny reflective surfaces and are often printed with colour pictures and patterns. The most important attributes of metallized nylon for balloons are its light weight, increasing buoyancy and its ability to keep the helium gas from escaping for several weeks. However, there has been some environmental concern, since the metallized nylon does not biodegrade or shred as a rubber balloon does, and a helium balloon released into the atmosphere can travel a long way before finally bursting or deflating. Release of these types of balloons into the atmosphere is harmful to the environment. Partygoers sometimes entertain each other by untying a balloon and inhaling the helium. Because the speed of sound in helium is about twice that in air, the helium causes the vocal tract to become more responsive to high-pitched sounds and less responsive to lower ones. The result is a voice that sounds high-pitched (and usually very funny). Balloon artists are entertainers who twist and tie inflated tubular balloons into sculptures (see also balloon animal). The balloons used for balloon sculpture are made of extra-stretchy rubber so that they can be twisted and tied without bursting. Since the pressure required to inflate a balloon is inversely proportional to the diameter of the balloon, these tiny tubular balloons are extremely hard to inflate initially. A pump is usually used to inflate these balloons. Decorators may use dozens of helium balloons to create balloon sculptures. Usually the round shape of the balloon restricts these to simple arches or walls, but on occasion more ambitious "sculptures" have been attempted with great success. The balloon decorating industry offers everything from simple balloon columns to stunning, very large and detailed sculptures. Water balloons are thin, small rubber balloons intended to be easily broken. They are usually used by children, who throw them at each other, trying to get each other wet - see practical joke.

Balloons in medicine

Angioplasty is a surgical procedure in which very small balloons are inserted into blocked or partially blocked blood vessels near the heart. Once in place, the balloon can be inflated to clear or compress arterial plaque, and to stretch the walls of the vein. A small stent can be inserted in its place to keep the vessel open after the balloon's removal. See myocardial infarction. Certain catheters have balloons at their tip to keep them from slipping out, for example the balloon of a Foley catheter is insufflated when the catheter is inserted into the urinary bladder and secures its position.

Records

Maximum flight heights

Manned Balloon The altitude record for manned balloons is 34668 metres. It was made by Malcolm D. Ross and Victor E. Prather over the Gulf of Mexico in 1961. Unmanned Balloon The altitude record for unmanned balloons is (1991 edition of Guinness Book) 51.8 kilometres. The vehicle was a Winzen-Balloon with a volume of 1.35 million cubic metres, which was launched in October 1972 in Chico, California, USA. This is the greatest altitude ever reached by a flying object requiring the surrounding air. Higher altitudes can only be reached by ballistic vehicles such as rockets, rocket planes or projectiles.

Balloon tank

See Atlas (rocket).

Usage of Balloons on other planets

In 1984 the Russian space probe Vega released two aerobots into the atmosphere of Venus, from which signals were received for two days.

Balloons in movies

- The Balloonatic (1923)
- The Wizard of Oz (1939)
- Trottie True (1949)
- Globex's messy break (1954)
- Around the World in Eighty Days (1956)
- The Red Balloon (1956)
- Stowaway in the Sky (1960)
- Mysterious Island (1961)
- Five Weeks in a Balloon (1962)
- The Great Race (1965)
- Those Magnificent Men in Their Flying Machines, or How I Flew from London to Paris in 25 hours 11 minutes (1965)
- Charlie Bubbles (1967)
- Chitty Chitty Bang Bang (1968)
- The Great Bank Robbery (1969)
- The Muppet Movie (1979)
- The Chipmunk Adventure (1987)
- Batman (1989)
- Around the World in 80 Days (2004)

External links

- [http://www.art-of-balloon-animals.ask-the-monkey.com Work of a typical balloon artist]
- [http://www.mbfloyd.com/ Balloon art instructions and gallery] Category:Parties ja:風船

Airship

1931]] An airship is a buoyant aircraft that can be steered and propelled through the air. Unlike aerodynamic aircraft which stay aloft by moving an airfoil through the air in order to produce lift, airships stay aloft primarily by means of a cavity (usually quite large) filled with a gas of lesser density than the surrounding atmosphere. Airships are also known as dirigibles from the French dirigeable, meaning "steerable". The term airship is sometimes informally used to mean a machine capable of atmospheric flight. The term zeppelin is a genericized trademark that originally referred to airships manufactured by the Zeppelin Company. In modern common usage, the terms zeppelin, dirigible and airship are used interchangeably for any type of rigid airship, with the terms blimp or airship alone used to describe non-rigid airships. In modern technical usage however, airship is the term used for all aircraft of this type with zeppelin referring only to aircraft of that manufacture and blimp referring only to non-rigid airships. In the early days of airships, the primary lifting gas was hydrogen. Until the 1950s, all airships, except for those in the United States continued to use hydrogen because it offered greater lift and was cheaper than helium. The United States (until then the sole producer) was also unwilling to export helium because of its rarity and the fact it was considered a strategic material. However, hydrogen is flammable when mixed with air, a quality that has caused disasterous effects. The buoyancy provided by hydrogen is actually only about 10% greater than that of helium. So the issue became one of safety versus cost. American airships have been filled with helium since the 1920s and modern passenger-carrying airships are, by law, now prohibited from being filled with hydrogen. Some small experimental ships still use hydrogen. Other small experimental airships are filled with hot air in a fashion similar to a hot air balloon. They are sometimes called hotships. In contrast to airships, balloons are buoyant aircraft that generally rely on wind currents for movement, though vertical movement can be controlled in both.

Types

balloon
- Rigid airships (for example, Zeppelins) have rigid frames containing multiple, non-pressurized gas cells or balloons to provide lift. Rigid airships do not depend on internal pressure to maintain their shape.
- Non-rigid airships (blimps) use a pressure level in excess of the surrounding air pressure in order to retain their shape.
- Semi-rigid airships, like blimps, require internal pressure to maintain their shape, but have extended, usually articulated keel frames running along the bottom of the envelope to distribute suspension loads into the envelope and allow lower envelope pressures.
- Metal-clad airships have characteristics of both rigid and non-rigid airships, utilizing a very thin, airtight metal envelope, rather than the usual rubber-coated fabric envelope. Only two ships of this type, Schwarz's aluminium ship of 1897 and the ZMC-2, have been built to date.
- Hybrid airship is a general term for an aircraft that combines characteristics of heavier-than-air (airplane or helicopter) and lighter than air technology. Examples include helicopter/airship hybrids intended for heavy lift applications and dynamic lift airships intended for long-range cruising. It should be noted that most airships, when fully loaded with cargo and fuel, are typically heavier than air, and thus must use their propulsion system and shape to generate aerodynamic lift, necessary to stay aloft; technically making them hybrid airships. However, the term "hybrid airship" refers to craft that obtain a significant portion of their lift from aerodynamic lift and often require substantial take-off rolls before becoming airborne.

History

The development of airships was necessarily preceded by the development of balloons. See balloon (aircraft) for details.

Airship Pioneers

Airships were among the first aircraft to fly, with various designs flying throughout the 19th century. They were largely attempts to make relatively small balloons more steerable, and often contained features found on later airships. These early airships set many of the earliest aviation records. In 1784 Jean-Pierre Blanchard fitted a hand-powered propeller to a balloon, the first recorded means of propulsion carried aloft. The first person to make an engine-powered flight was Henri Giffard who, in 1852, flew 27 km (17 miles) in a steam-powered airship. Charles F. Ritchel made a public demonstration flight in 1878 of his hand-powered one-man rigid airship and went on to build and sell five of his aircraft. Paul Haenlein flew an airship with an internal combustion engine on a tether in Vienna, the first use of such an engine to power an aircraft. In 1880, Karl Wölfert and Ernst Baumgarten attempted to fly a powered airship in free flight, but crashed. In the 1880's a Serb named Ogneslav Kostovic Stepanovic also designed and built an airship. However the craft was destroyed by fire before it flew. In 1883, the first electric-powered flight was made by Gaston Tissandier who fitted a 1-1/2 horsepower Siemens electric motor to an airship. The first fully controllable free-flight was made in a French Army airship, La France, by Charles Renard and Arthur Krebs in 1884. The 170 foot long , 66,000 cubic foot airship covered 8 km (5 miles) in 23 minutes with the aid of an 8-1/2 horsepower electric motor. In 1888, Wölfert flew a Daimler-built petrol engine powered airship at Seelburg. In 1896, a rigid airship created by Croatian engineer David Schwarz made its first flight at Tempelhof field in Berlin. After Schwarz's death, his wife, Melanie Schwarz, was paid 15,000 Marks by Zeppelin for information about the airship. In 1901, Santos Dumont, in his airship "Number 6", a small blimp, won the Deutsch de la Meurthe prize of 100,000 francs for flying from the Parc Saint Cloud to the Eiffel Tower and back in under thirty minutes. Many inventors were inspired by Santos-Dumont's small airships and a veritable airship craze began world-wide. Many airship pioneers, such as the American Thomas Scott Baldwin financed their activities through passenger flights and public demonstration flights. Others, such as Walter Wellman and Melvin Vaniman set their sights on loftier goals, attempting two polar flights in 1907 and 1909, and two trans-atlantic flights in 1910 and 1912. The beginning of the "Golden Age of Airships" was also marked with the launch of the Luftschiff Zeppelin LZ1 in July of 1900 which would lead to the most successful airships of all time. These Zeppelins were named after the pioneer Count Ferdinand von Zeppelin. Von Zeppelin began experimenting with rigid airship designs in the 1890's leading to some patents and the LZ1 (1900) and the LZ2 (1906). At the beginning of WW1 the Zeppelin airships had a cylindrical aluminium alloy frame and a fabric-covered hull containing separate gas cells. Multi-plane tail fins were used for control and stability, and two engine/crew cars hung beneath the hull driving propellers attached to the sides of the frame by means of long drive shafts. Additionally there was a passenger compartment (later a bomb bay) located halfway between the two cars.

Airships in the First World War

WW1 The prospect of using airships as bomb carriers had been recognised in Europe well before the airships themselves were up to the task. H. G. Wells described the obliteration of entire fleets and cities by airship attack in The War in the Air (1908), and scores of less famous British writers declared in print that the airship had altered the face of world affairs forever. On 5 March 1912, Italian forces became the first to use dirigibles for a military purpose during reconnaissance west of Tripoli behind Turkish lines. It was World War I, however, that marked the airship's real debut as a weapon. Count Zeppelin and others in the German military believed they had found the ideal weapon with which to counteract British Naval superiority and strike at Britain itself. More realistic airship advocates believed the Zeppelin was a valuable long range scout/attack craft for naval operations. Raids began by the end of 1914, reached a first peak in 1915, and then were discontinued after 1917. Zeppelins proved to be terrifying but inaccurate weapons. Navigation, target selection and bomb-aiming proved to be difficult under the best of conditions. The darkness, high altitudes and clouds that were frequently encountered by zeppelin missions reduced accuracy even further. The physical damage done by the zeppelins over the course of the war was trivial, and the deaths that they caused (though visible) amounted to a few hundred at most. The zeppelins also proved to be vulnerable to attack by aircraft and antiaircraft guns, especially those armed with tracer bullets. Several were shot down in flames by British defenders, and others crashed 'en route'. In retrospect, advocates of the naval scouting role of the airship proved to be correct, and the land bombing campaign proved to be disastrous in terms of morale, men and material. Many pioneers of the German airship service died bravely, but needlessly in these propaganda missions. They also drew unwanted attention to the construction sheds which were bombed by the British Royal Naval Air Service. Meanwhile the Royal Navy had recognised the need for small airships to counteract the submarine threat in coastal waters, and beginning in February 1915, began to deploy the SS (Sea Scout) class of blimp. These had a small envelope of 60-70,000 cu feet and at first utilised standard single engined planes (BE2c, Maurice Farman, Armstrong FK) shorn of wing and tail surfaces as an economy measure. Eventually more advanced blimps with purpose built cars, such as the C (Coastal), C
- (Coastal Star), NS (North Sea), SSP (Sea Scout Pusher), SSZ (Sea Scout Zero), SSE (Sea Scout Experimental) and SST (Sea Scout Twin) classes were developed. The NS class, after initial teething problems proved to be the largest and finest airships in British service. They had a gas capacity of 360,000 cu feet, a crew of 10 and an endurance of 24 hours. Six 230 lb bombs were carried, as well as 3-5 machine guns. British blimps were used for scouting, mine clearance, and submarine attack duties. During the war, the British built over 225 non-rigid airships, of which several were sold to the Russia, France, the US and Italy. Britain, in turn, purchased one M-type semi-rigid from Italy whose delivery was delayed until 1918. Eight rigid airships had been completed by the armistice, although several more were in an advanced state of completion by the wars end. The large number of trained crews, low attrition rate and constant experimentation handling techniques meant that at the wars end Britain was the world leader in non-rigid airship technology. Royal Navy Airplanes had essentially replaced airships as bombers by the end of the war, and Germany's remaining zeppelins were scuttled by their crews, scrapped or handed over to the Allied powers as spoils of war. The British rigid airship program, meanwhile, had been largely a reaction to the potential threat of the German one and was largely, though not entirely, based on imitations of the German ships. Royal Navy]]

Airships in the Inter-war period

Airships using the Zeppelin construction method are sometimes referred to as zeppelins even if they had no connection to the Zeppelin business. Several airships of this kind were built in the USA and Britain in the 1920s and 1930s, mostly imitating original Zeppelin design derived from crashed or captured German World War I airships. The British R33 and R34, for example, were near identical copies of the German L-33, which crashed virtually intact in Yorkshire on September 24 1916. Despite being almost three years out of date by the time they were launched in 1919, these sister ships were two of the most successful in British service. On July 2 1919 R34 began the first double crossing of the Atlantic by an aircraft. It landed at Mineola, Long Island on July 6, 1919 after 108 hours in the air. The return crossing commenced on July 8 because of concerns about mooring the ship in the open, and took 75 hours. Impressed, British leaders began to contemplate a fleet of airships that would link Britain to its far-flung colonies, but unfortunately post-war economic conditions lead to most airships being scrapped and trained personnel dispersed, until the R-100 and R-101 commenced construction in 1929. Another example was the first American-built rigid dirigible ZR-1 "USS Shenandoah" , which flew in 1923, while the Los Angeles was under construction. The ship was christened on August 20 in Lakehurst, New Jersey and was the first to be inflated with the noble gas helium, which was still so rare at the time that the Shenandoah contained most of the world's reserves. So, when the Los Angeles was delivered, it was at first filled with the helium borrowed from ZR-1. The Zeppelin works were saved by the purchase of what became called the USS Los Angeles by the United States Navy, paid for with "war reparations" money, owed according to the Versailles Treaty. The success of the Los Angeles encouraged the United States Navy to invest in larger airships of its own. Germany, meanwhile, was building the Graf Zeppelin, the first of what was intended to be a new class of passenger airships. Interestingly, the Graf Zeppelin burned un-pressurised blau gas, similar to propane, as fuel. Since its density was similar to that of air, it avoided the weight change when fuel was used. Initially airships met with great success and compiled an impressive safety record. The Graf Zeppelin, for example, flew over 1 million miles (including the first circumnavigation of the globe by air) without a single passenger injury. The expansion of airship fleets and the growing (sometimes excessive) self-confidence of airship pilots gradually made the limits of the type clear, however, and initial successes gave way to a series of tragic rigid airship accidents. In fact, with the exception of the Graf Zeppelin, most of the world's most famous airships eventually crashed. propane Although USS Los Angeles flew successfully for 8 years, the U.S. Navy eventually lost all three of its American-built rigid airships to accidents. USS Shenandoah flew into a thunderstorm over Ohio in 1925 and broke into pieces. USS Akron was caught by a microburst and driven down into the surface of the sea off the shore of New Jersey in 1933. Both storm-related losses led to great loss of life. USS Macon broke up after suffering a structural failure in its upper fin off the shore of Point Sur in California in 1935. All but 2 of the 83 people aboard Macon survived the crash thanks to the issue of life jackets and inflatable rafts in the interval since the Akron disaster. Britain suffered its own airship tragedy in 1930 when R 101, a ship far advanced for its time but rushed to completion and sent on a trip to India before she was ready, crashed in France with the loss of 48 out of 54 aboard. Because of the bad publicity surrounding the crash, the Air Ministry grounded the competing R 100 in 1930 and sold it for scrap in 1931. The most spectacular and widely remembered airship accident, however, is the burning of the Hindenburg on 6 May 1937, which caused public faith in airships to evaporate in favour of faster, more cost-efficient (albeit less energy-efficient) airplanes. What is generally not remembered is that of the 97 people on board, 62 got out alive. There were 36 dead: 13 passengers, 22 aircrew, and one American groundcrewman. Most probably, the airplane became the transport of choice also because it is less sensitive to wind. Aside from the problem of manoeuvring and docking in high winds, the trip times for an upwind versus a downwind trip of an airship can differ greatly, and even crabbing at an angle to a crosswind eats up ground speed. Those differences make scheduling difficult.

Airships in the Second World War

The greatest number of airships in use during the Second World War were blimps used to form anti-aircraft defences. Thousands were put up tethered to the ground by steel cables to form obstacles to German aircraft flying on bombing missions over England. American construction of airships for civilian purposes was halted in the 1930s by a series of fatal crashes. However, military development of airships was continued in the US. While Germany determined that airships were obsolete for military purposes in the coming war and concentrated on the development of airplanes, the United States pursued a program of military airship construction even though it had not developed a clear military doctrine for airship use. At the Japanese attack on Pearl Harbor on 7 December 1941 that brought the United States into World War II, it had 10 non-rigid airships:
- 4 K-class : K-2, K-3, K-4 and K-5 designed as a patrol ships built from 1938.
- 3 L-class : L-1, L-2 and L-3 as small training ships, produced from 1938.
- 1 G-class built in 1936 for training.
- 2 TC-class that were older patrol ships designed for land forces, built in 1933. The US Navy acquired them from Army in 1938. Only K and TC class airships could be used for combat purposes and they were quickly pressed into service against Japanese and German submarines which at that time were sinking US shipping in visual range of US coast. US Navy command, remembering the airship anti-submarine success from WWI, immediately requested new modern anti-submarine airships and on 2 January 1942 formed the ZP-12 patrol unit based in Lakehurst from the 4 K airship. The ZP-32 patrol unit was formed from 2 TC and 2 L airship a month later, based at US Navy (Moffet Field) in Sunnyvale in California. An airship training base was created there as well. In the years 1942-1944, approximately 1400 airship pilots and 3000 support crew members were trained in the military airship crew training program and the airship military personnel grew from 430 to 12400. The US airships were produced by the Goodyear factory in Akron, Ohio. From 1942 till 1945, 154 airships were built for the US Navy (133 K-class, 10 L-class, 7 G-class, 4 M-class) and 5 L-class for civilian customers (serial number L-4 to L-8). The primary airship tasks were patrol and convoy escort near the US coastline. They also served as an organisation center for the convoys to direct ship movements and course, and were used during naval search and rescue operations. Rarer duties of the airships included aerophoto reconnaissance, naval mine-laying and mine-sweeping, parachute unit transport and deployment, cargo and personnel transportation. They were deemed quite successful in their duties with the highest combat readiness factor in the entire US air force (87%). They were extremely successful in their primary goal of anti-submarine warfare as the below numbers illustrate: During the war some 532 ships were sunk near the coast by submarines.
- 1942: 454 ships sunk near the US coast, 4-13 airships in service
- 1943: 65 ships sunk near the US coast, 17-53 airships in service
- 1944: 8 ships sunk near the US coast, 56-68 airships in service
- 1945: 3 ships sunk near the US coast, 53-48 airships in service Not a single ship of the 89,000 or so in convoys escorted by blimps was sunk by enemy fire. Airships engaged submarines with depth charges, or rarely from other on-board weapons. They were very successful since they could match the slow speed of the submarine and bomb it until its destruction. Additionally, submerged submarines had no means of detecting an airship approaching. Only one airship was ever destroyed by U-boat: on the night of 18/19 July 1943 a K-class airship (K-74) from ZP-21 division was patrolling the coastline near Florida. Using radar, the airship located a surfaced German submarine. Due to the failure of the depth charge release mechanism, the airship was unable to release the bombs during the bombing run and the German returned fire. The (K-74) received serious damage and was forced to make a water landing. The crew was rescued by patrol boats in the morning, but one crewman died from a shark attack. The U-Boat responsible was sunk a few hours later. Some US airships saw action in the European war theater. The ZP-14 unit operating in the Mediterranean area from June 1944 completely denied the use of the Gibraltar Straits to Axis submarines. Airships from the ZP-12 unit took part in the sinking of the last U-Boat before German capitulation, sinking U-881 on 6 May 1945 together with destroyers Atherton and Mobery. The Soviet Union used a single airship during the war. The W-12, built in 1939, entered service in 1942 for paratrooper training and equipment transport. It made 1432 runs with 300 metric tons of cargo until 1945. On 1 February 1945 the Soviets constructed a second airship, a Pobieda-class unit (used for mine-sweeping and wreckage clearing in the Black Sea) which later crashed on 21 January 1947. Another W-class - W-12bis Patriot was commissioned in 1947 and was mostly used for crew training, parades and propaganda.

Continued use

Although airships abandoned carrying passengers, they continued to be used for other purposes. In particular, the US Navy as above. 1945 In recent years, the Zeppelin company has reentered the airship business. Their new model, designated the Zeppelin NT made its maiden flight on September 18, 1997. There are currently three NT aircraft flying. One has been sold to a Japanese company, and was planned to be flown to Japan in the summer of 2004. However, due to delays getting permission from the Russian government, the company decided to transport the airship to Japan by ship. An airship was flown over Athens during the 2004 Summer Olympics as part of security anti-terrorism measures. Blimps continue to be used for advertising and as TV camera platforms at major sporting events. Several companies, such as Cameron Balloons in Bristol, UK, build hot-air airships. These combine the structures of both hot-air balloons and small airships. The envelope is the normal 'cigar' shape, complete with tail fins, but is not inflated by helium, but by hot air (as in a balloon), which provides the lifting force. A small gondola, carrying the pilot (and sometimes between 1 and 3 passengers), a small engine and the burners to provide the hot air is suspended below the envelope, below an opening through which the burners protrode. The advantages with the hot-air airship are that is costs less to buy and maintain than a standard modern blimp and it can be quickly deflated at the end of a flight, meaning it is easily transported on a trailer or truck, without the need for expensive storage arrangements. Such craft usually are very slow moving, with a typical top speed of 15-20 mph. They are used mainly for advertising, but several have been used in rainforests for wildlife observation, because they could easily be transported into remote areas.

Present-day research

Recently, several companies have begun exploring the possibilities of airships with their potentially huge lifting capacities, near-VTOL (Vertical Take-Off and Landing) capabilities, and potentially lower freight costs, though none has demonstrated economic viability yet. In addition to the research on conventional blimp designs, several unconventional prototype designs continue to be investigated. One example is a design commissioned by the United States Military for a massive solar powered spy and communication blimp, 25 times larger than the Goodyear Blimp, which it is hoped will be able to carry tons of payload far above the range of antiaircraft weapons. The company developing the design, JP Aerospace, claims to have long-range plans to develop an "orbital airship" capable of lifting cargo into low earth orbit with a marginal transportation cost of $1 per short ton per mile of altitude. Contracts are underway with Lockheed for high-altitude airships (HAAs). Airships are being investigated as a possible alternative to LEO (low Earth orbit) satellite communications. One proposed system involves sending unmanned airships high above cities at 70,000 feet (21 km). These aircraft would provide cellular voice and data service to a city with service similar to what LEOs provide. Due to the fact that these would be located in the stratosphere, one company currently working on this calls their proposed airships "Stratellites". With the September 11 terrorist attacks, the U.S. military has been forced to reassess threats and evaluate strategies for aerial defence. Two major defense contractors are pitching the zeppelin as a potential piece in the homeland security jigsaw. Military planners envision unmanned airships as high-altitude radar platforms keeping watch for anything threatening U.S. airspace. In February 2005, the US Department of Defense announced a research program named the WALRUS HULA [http://www.darpa.mil/tto/programs/walrus.html] [http://www.defenseindustrydaily.com/2005/10/us-cbo-gives-ok-to-hula-airships-for-airlift/index.php] to explore the development of very large airships. The primary goal of the research program is determine the feasibility of building an airship capable of carrying 500 short tons (450 metric tons) of payload a distance of 12,000 miles (20,000 km) and land on an unimproved location without the use of external ballast or ground equipment (e.g. masts.)

Fiction

Airships were a popular theme in scientific romance (prototypical science fiction) and adventure fiction published in the late 19th century and the earliest years of the 20th century. The theme of aeronautical exploration was most famously explored in this period by Jules Verne (The Clipper of the Clouds) and H. G. Wells (The War in the Air). After the invention of the airplane, airships were largely forgotten by mainstream fiction, and today appear mainly in historical fiction and alternate history (particularly the steampunk genre and the work of Michael Moorcock, most notably The Warlord of the Air). In his "Anome" trilogy (The Anome aka The Faceless Man, The Brave Free Men, and The Asutra), Jack Vance depicts a system of airships tethered to unmanned monorail dolleys which keep them on fixed courses. In Philip Pullman's trilogy His Dark Materials (The Golden Compass, The Subtle Knife, and The Amber Spyglass), which takes place in a parallel universe, airships are the only method of air travel. Airships' strengths and weaknesses are well portrayed in these novels: their great lifting capacity makes them valuable for transporting supplies and soldiers, but they are easily destroyed. In Theodore Judson's post-apocalyptic Fitzpatrick's War, the neo-feudal Yukon Confederacy makes heavy use of airships as military and civilian transports. Kim Stanley Robinson in his Mars Trilogy envisages rigid airships being used as a major form of transport for the emerging settlements of Mars. Kenneth Oppel's novel Airborn, a young adult adventure set in an alternate history in which airship travel is common, won the 2004 Governor General's Award for children's literature. [http://www.airborn.ca/ www.airborn.ca]. There is also a sequel, Skybreaker. In Philip Reeve's Hungry City Chronicles , which takes place in the distant future, airships are the primary form of travel because of the mobile nature of cities in the books. In the series, it is mentioned that airship technology had advanced beyond the imaginations of the "Ancients". Airships include freighters, sky yachts, fighter airships and immense air destroyers. In Jasper Fforde's Thursday Next series the airship is a significant and popular form of transport. David Brin's 1990 Hugo nominated near-future, post global-warming science fiction novel, "Earth" (set in 2038), portrays a future where there is regular use of airships for passenger transportation. China Miéville's Bas Lag novels (Perdido Street Station, The Scar, Iron Council) feature airships ("dirigibles") as a common mode of transport; they are used as taxis and military scouts. The Scar featured two large war airships controlled by the pirate city of Armada: The Arrogance (a captured New Crobuzon airship used as a crow's nest) and the Trident. Philip Jose Farmer's Riverworld novels feature a giant rigid and several non-rigid airships which are used to reach the north pole of the Riverworld More than a few video games, such as Crimson Skies, Skies of Arcadia and the Final Fantasy series, utilize airships in their fictional worlds as a major mode of transportation. (In some cases (most notably in the Final Fantasy series), the "airship" is actually a ship with wings, propellers, etc..) Also, in Command & Conquer Red Alert 2, the Soviets' most lethal conventional weapons are their extremely tough but slow Kirov Airships, which drop incredibly powerful bombs.

References

- Rich Archbold and Ken Marshall,Hindenberg, an Illustrated History, 1994 ISBN 0446517844
- William F. Althoff , USS Los Angeles: The Navy's Venerable Airship and Aviation Technology , 2003, ISBN 1574886207
- Peter Brooks , Zeppelin: Rigid Airships 1893-1940 , 2004, ISBN 0851778453
- Charles P. Burgess, Airship Design, (1927) 2004 ISBN 1410211738
- Wilbur Cross, Disaster at the Pole, 2002 ISBN 1-58574-496-4
- Arthur Frederick et al., Airship saga: The history of airships seen through the eyes of the men who designed, built, and flew them , 1982, ISBN 0713710012
- Manfred Griehl and Joachim Dressel, Zeppelin! The German Airship Story, 1990 ISBN 1-85409-045-3
- Gabriel Alexander Khoury (Editor), Airship Technology (Cambridge Aerospace Series) , 2004, ISBN 0521607531
- Alexander McKee, Ice crash, 1980, ISBN 0312403828
- Andrzej Morgała, Sterowce w II Wojnie Światowej (Airships in the Second World War), Lotnictwo, 1992
- Ces Mowthorpe, Battlebags: British Airships of the First World War, 1995 ISBN 0905-778-138
- US War Department , Airship Aerodynamics: Technical Manual, (1941) 2003 , ISBN 1410206149

External links

General

- [http://spot.colorado.edu/~dziadeck/airship.html Airship Home Page] - Provides a list of airship related websites. Also contains airship mailing list.
- [http://www.hotairship.com/ Airship and Blimp Resources] - This site focuses more on how to build your own airship with a particular focus on hot air airships (a.k.a "hotships")
- [http://lists.sculptors.com/mailman/listinfo/airships Airships Mailing List] - A forum for the discussion and design of lighter-than-air craft.

Associations

- [http://www.airship-association.org/ The Airship Association] - British based association for people interested in all things to do with airships.
- [http://www.blimpinfo.com/ Lighter than Air Society] - US based association for people interested in all things to do with airships.
- [http://www89.pair.com/techinfo/ABAC/abac.htm The Association of Balloon and Airship Constructors] - Maintains an extensive technical library on airship technology old and new.

Historical

- [http://www.nlhs.com/ Navy Lakehurst Historical Society] - airship history with a focus on activities at the historically most active airship base in the US.
- [http://www.aht.ndirect.co.uk/ Airships Online] - website of the Airships Heritage Trust. It contains an extensive history relating British Airships from 1900 to the present day.
- [http://www.history.navy.mil/branches/lta-m.html US Navy Airship History]
- Ferdinand von Zeppelin, US [http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=/netahtml/srchnum.htm&r=1&f=G&l=50&s1=621,195.WKU.&OS=PN/621,195&RS=PN/621,195 621,195] Patent, "Navigable Ballon". March 14, 1899.
- [http://specialcollections.wichita.edu/collections/ms/99-01/99-1-bio.html Harold G. Dick Airship Collection] - biography of Harold G. Dick
- [http://specialcollections.wichita.edu/exhibits/haldick/haldickpostcards.html Postcards from Harold G. Dick Airship Collection]
- [http://specialcollections.wichita.edu/exhibits/haldick/haldick.html The Golden Age of the Great Passenger Airships: The Collection of Harold G. Dick]
- [http://www.centennialofflight.gov/essay/Lighter_than_air/Beginning_of_the_Dirigible/LTA6.htm US Centennial of Flight Commission]

Manufacturers and commercial operators

- [http://www.airship-association.org/net.html Airship Association Net Links Page] for a comprehensive list of companies throughout the world focusing on the development of airships.
- [http://www.americanblimp.com American Blimp Corporation] In association with The Lightships Group, this company builds and operates the world's largest fleet of airships.
- [http://www.gefa-flug.com GEFA-FLUG GmbH - The Air Company] -- makers of hot air airships
- [http://www.zeppelin-nt.com/index_e.htm Zeppelin Luftschifftechnik GmbH] -- The Zeppelin Company and the Zeppelin NT.
- [http://www.goodyearblimp.com/ The Goodyear Blimps] -- The most famous modern airships. These aircraft are owned and operated by the Lockheed Martin Corporation.
- [http://www.airshipman.com/ Airship Management Services] -- Operators of several type-certified airships including the Fuji Blimp. These aircraft were originally built by the Westinghouse Corporation with the designation Skyship 600. They also own and operate a sightseeing airship in Switzerland under the name [http://www.skycruiser.co.uk/ Skycruiser Switzerland]
- [http://www.cameronballoons.co.uk/airships.htm Cameron Airships] -- Hot air airships manufactured by Cameron Balloon - the world's largest manufacturer of hot air balloons.
- [http://www.lindstrand.co.uk/Airship.html Lindstrand Airships] - Hot air airships manufactured by hot air balloon company Lindsrand - a subsidiary of Cameron Balloon.
- [http://aas.augurballoons.com/ Augur Aerostatic Systems] -- Russian company making both gas and hot air airships

Experiments, prototypes and one-offs

- [http://www.21stcenturyairships.com 21st Century Airships Inc.] Developers of spherical, finless airships. From June 12, 2003 until December 13, 2004, a 21st Century Airship craft held the absolute FAI altitude record for airships of 6,234 m (20,450 ft).
- [http://www.aerosml.com/main.htm Aeros Corporation] - In addition to producing several small airships, this company is one of the winners of Phase I funding from DARPA for Project WALRUS.
- [http://www.usairships.com/ USA Airships]
- [http://www.myairship.com/database/whitedwarf.html White Dwarf] - A small, human-powered airship
- [http://www.endlessflyers.com/nice-calvi.htm Zeppy] - Human powered airship -- website in French.

Designs under development

- [http://www.lockheedmartin.com/wms/findPage.do?dsp=fec&ci=14477&rsbci=12972&fti=0&ti=0&sc=400 Lockheed-Martin HAA Project]
- [http://www.sanswire.com/ Sanswire Stratellite]
- [http://www.dynalifter.com/ Dynalifter]
- [http://www.atg-airships.com Advanced Technologies Group] Until August of 2005, when it went into receivership, this company was developing a range of products such as UAV's - Unmanned Aerial Vehicles, heavier-than-air airships and HAPS' - High Altitude Platform Stations for telecommunication.

Proposed designs

- [http://www.airship.org/ Vertical Airships]
- [http://rigid.tripod.com/english.html Airship Holland]
- [http://www.nagyairship.com/ Nagy High Speed Airship]
- [http://www.millenniumairship.com/ Millennium Airship]
- [http://www.quantumaerostatics.com/ Quantum Aerostatics]
- [http://www.hacinc.us/ Hybrid Aircraft Corporation]
- [http://www.ahausa.com/ Advanced Hybrid Aircraft] Category:Airships Category:Aeronautics ja:飛行船

Density

: For other senses of "density", see density (disambiguation). Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. The higher an object's density, the higher its mass per volume. The average density of an object equals its total mass divided by its total volume. A denser object (such as iron) will have less volume than an equal mass of some less dense substance (such as water). The SI unit of density is the kilogram per cubic metre (kg/m³) :

\rho = \frac

where :ρ is the object's density (measured in kilograms per cubic metre) :m is the object's total mass (measured in kilograms) :V is the object's total volume (measured in cubic metres) Under specified conditions of temperature and pressure, density of a fluid is defined as described above. However, the density of a solid material can be different, depending on exactly how it is defined. Take sand for example. If you gently fill a container with sand, and divide the mass of sand by the container volume you get a value termed loose bulk density. If you took this same container and tapped on it repeatedly, allowing the sand to settle and pack together, and then calculate the results, you get a value termed tapped or packed bulk density. Tapped bulk density is always greater than or equal to loose bulk density. In both types of bulk density, some of the volume is taken up by the spaces between the grains of sand. Also, in terms of candy making, density is affected by the melting and cooling processes. Loose granular sugar, like sand, contains a lot of air and is not tightly packed, but when it has melted and starts to boil, the sugar loses its granularity and entrained air and becomes a fluid. When you mold it to make a smaller, compacted shape, the syrup tightens up and loses more air. As it cools, it contracts and gains moisture, making the already heavy candy even more dense.

Other units

Density in terms of the SI base units is expressed in terms of kilograms per cubic metre (kg/m³). Other units fully within the SI include grams per cubic centimetre (g/cm³) and megagrams per cubic metre (Mg/m³). Since both the litre and the tonne or metric ton are also acceptable for use with the SI, a wide variety of units such as kilograms per litre (kg/L) are also used. Imperial units or U.S. customary units, the units of density include pounds per cubic foot (lb/ft³), pounds per cubic yard (lb/yd³), pounds per cubic inch (lb/in³), ounces per cubic inch (oz/in³), pounds per gallon (for U.S. or imperial gallons) (lb/gal), pounds per U.S. bushel (lb/bu), in some engineering calculations slugs per cubic foot, and other less common units. The maximum density of pure water at a pressure of one standard atmosphere is 999.972 kg/m³; this occurs at a temperature of about 3.98 °C (277.13 K). From 1901 to 1964, a litre was defined as exactly the volume of 1 kg of water at maximum density, and the maximum density of pure water was 1.000 000 kg/L (now 0.999 972 kg/L). However, while that definition of the litre was in effect, just as it is now, the maximum density of pure water was 0.999 972 kg/dm³. During that period students had to learn the esoteric fact that a cubic centimetre and a millilitre were slightly different volumes, with 1 mL = 1.000 028 cm³. (often stated as 1.000 027 cm³ in earlier literature).

Measurement of density

A common device for measuring fluid density is a pycnometer. A device for measuring absolute density of a solid is a gas pycnometer.

Density of substances

Perhaps the highest density known is reached in neutron star matter (see neutronium). The singularity at the centre of a black hole, according to general relativity, does not have any volume, so its density is undefined. The most dense naturally occurring substance on Earth is iridium, at about 22650 kg/m³. A table of densities of various substances:

Substance	Density in kg/m³
Iridium	22650
Osmium	22610
Platinum	21450
Gold	19300
Tungsten	19250
Uranium	19050
Mercury	13580
Palladium	12023
Lead	11340
Silver	10490
Copper	8960
Iron	7870
Tin	7310
Titanium	4507
Diamond	3500
Basalt	3000
Granite	2700
Aluminium	2700
Graphite	2200
Magnesium	1740
PVC	1300
Seawater	1025
Water	1000
Ice	917
Polyethylene	910
Ethyl alcohol	790
Gasoline	730
Aerogel	.003
any gas	0.0446 times the average molecular mass, hence between 0.09 and ca. 10.0 (at standard temperature and pressure)
For example air	1.2

Note the low density of aluminium compared to most other metals. For this reason, aircraft are made of aluminium. Also note that air has a nonzero, albeit small, density. Aerogel is the world's lightest solid.

Metal

:For alternative meanings see metal (disambiguation). metal (disambiguation) In chemistry, a metal (Greek: Metallon) is an element that readily forms ions (cations) and has metallic bonds, and metals are sometimes described as a lattice of positive ions (cations) in a cloud of electrons. The metals are one of the three groups of elements as distinguished by their ionisation and bonding properties, along with the metalloids and nonmetals. On the periodic table, a diagonal line drawn from boron (B) to polonium (Po) separates the metals from the nonmetals. Elements on this line are metalloids, sometimes called semi-metals; elements to the lower left are metals; elements to the upper right are nonmetals. Nonmetal elements are more abundant in nature than are metallic elements, but metals in fact constitute most of the periodic table. Some well-known metals are aluminium, copper, gold, iron, lead, silver, titanium, uranium, and zinc. The allotropes of metals tend to be lustrous, ductile, malleable, and good conductors, while nonmetals generally speaking are brittle (for solid nonmetals), lack luster, and are insulators. A more modern definition of metals is that they have overlapping conductance and valence bands in their electronic structure. This definition opens up the category for metallic polymers and other organic metals, which have been made by researchers and employed in high-tech devices. These synthetic materials often have the characteristic silvery-grey reflectiveness of elemental metals. The properties of conductivity are mainly because each atom exerts only a loose hold on its outermost electrons (valence electrons); thus, the valence electrons form a sort of sea around the close-packed metal nucleii cations. Most metals are chemically unstable, reacting with oxygen in the air to form oxides over varying timescales (iron rusts over years, potassium burns in seconds, silver tarnishes in months, although this is due to reactions with sulfur, although ozone, which is three atoms of oxygen bound together, can also play a part, as can hydrogen sulfide). The alkali metals react quickest followed by the alkaline earth metals, found in the leftmost two groups of the periodic table. The transition metals take much longer to oxidise (e.g. iron, copper, zinc, nickel), and palladium, platinum and gold do not react with atmospheric oxygen at all (which is why we make shiny jewelry from them). Some metals form a barrier layer of ox