Balloon (aircraft)

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Balloons are a type of lighter than air aircraft that remain aloft due to their buoyancy. Balloons travel by moving with the wind. They are distinct from airships which are buoyant aircraft which can be propelled through the air in a controlled manner. They are also distinct from aerostats which are balloons that are moored to the ground rather than free flying.

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Types of balloon aircraft

There are four main types of balloons:

  • hot air balloons obtain their buoyancy by heating the air inside the envelope. They are the most common type of balloon aircraft.
  • gas balloons filled with an unheated gas such as:
    • hydrogen - not widely used for aircraft since the Hindenburg disaster because of high flammability except for some sport balloons as well as nearly all unmanned scientific and weather balloons.
    • helium - the gas used today for all airships and most manned balloons in the United States
    • ammonia - used infrequently due to its caustic qualities and limited lift
    • coal gas - used in the early days of ballooning, high flammability
  • Rozière balloons use both heated and unheated lifting gases. The most common modern use of this type of balloon is for long distance record flights such as the recent circumnavigations.
  • superpressure balloons that allow the lifting gas to be pressurized in flight [with the objective of limiting or eliminating the loss of gas from day-time heating]

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History

The hot air balloon was first developed as a children's toy round about the 2nd or 3rd century AD in China.

It has been proposed that some ancient civilisations developed manned hot air balloon flight. For example it has been proposed that the Nazca lines (which are best seen from the air) presuppose some form of manned flight, and a balloon was the only possible available technology that could have achieved this. Julian Nott designed and built a balloon using woven cotton fabric and a Torta reed gondola, both readily available to the peoples who made the Nazca lines. Heating the air in the balloon with a wood fire, Nott flew over the Nazca Plains. Nott comments that there is no evidence of any kind that that ancient peoples did fly but this flight proved beyond doubt that most early civilizations could have flown: all they needed was a loom and fire.

In 1709 in Lisbon, Bartolomeu de Gusmão made a balloon filled with heated air rise inside a room. He also made a balloon named Passarola (Port. Big bird) and attempted to lift himself from Saint George Castle, in Lisbon, but only managed to harmlessly fall about one kilometre away.

Following Henry Cavendish's work on hydrogen, of 1766, Joseph Black proposed that a balloon filled with hydrogen would be able to rise in the air.

The first recorded manned balloon flight in history was made in a hot air balloon built by the Montgolfier brothers on November 21, 1783. The flight started in Paris and reached a height of 500 feet or so. The pilots, Jean-François Pilâtre de Rozier and Francois Laurent (the Marquis of d’ Arlanders) covered about 5 1/2 miles in 25 minutes.

Only a few days later, on December 1, 1783, Professor Jacques Charles and Nicholas Louis Robert made the first gas balloon flight. Like the first hot air balloon flight, this flight left from Paris as well. The hydrogen filled balloon flew to almost 2000 feet, stayed aloft for over 2 hours and covered a distance of 27 miles, landing in the small town of Nesle.

Once flight was shown to be possible, the next great challenge was to fly across the English Channel. The feat was accomplished on January 7, 1785 by Jean-Pierre Blanchard, a Frenchman, and American John Jeffries, who sponsored the flight.

Blanchard went on to make the first manned flight of a balloon in America on January 9, 1793. His hydrogen filled balloon took off from a prison yard in Philadelphia, Pennsylvania. The flight reached ascended to about 5,800 feet and landed in Gloucester County in New Jersey. It is interesting to note that George Washington observed the take off.

Gas balloons became the most common type from the 1790s until the 1960s.

The first steerable (also known as a dirigible) balloon was attempted by Henri Giffard in 1852. Powered by a steam engine it was too slow to be effective. Like heavier than air flight, the internal combustion engine made dirigibles, especially blimps, practical, starting in the late nineteenth century.

Ed Yost reinvented the design of hot air balloons in the late 1950s using rip-stop nylon fabrics and high powered propane burners to create the modern hot air balloon. His first flight of such a balloon on October 22, 1960 in Bruning, Nebraska His flight lasted 25 minutes and covered 3 miles.

Yost's improved design for hot air balloons triggered the entire modern sport balloon movement. Today, hot air balloons are much more common than gas balloons.

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Balloons as flying machines

A balloon is conceptually the simplest of all flying machines. The balloon is a fabric envelope filled with a gas that is lighter than the surrounding atmosphere. As the entire balloon is less dense than its surroundings, it rises, taking along with it a basket, attached underneath, that carries passengers or payload.

The first balloons capable of carrying passengers used hot air to obtain buoyancy and were built by the brothers Josef and Etienne Montgolfier in Annonay, France.

Balloons using the light gas hydrogen for buoyancy were flown less than a month later. They were invented by Professor Jacques Charles and first flown on December 1, 1783. Gas balloons have greater lift and can be flown much longer than hot air, so gas balloons dominated ballooning for the next 200 years. In the 19th century, it was common to use town gas to fill balloons; it was not as light as hydrogen gas, but was much cheaper and readily available.

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The third balloon type was invented by Pilâtre de Rozier and is a hybrid of a hot air and a gas balloon. Gas balloons have an advantage of being able to fly for a long time and hot air balloons have an advantage of being able to easily change altitude so the Rozier balloon was a hydrogen balloon with a separate hot air balloon attached. In 1785, Pilâtre de Rozier took off in an attempt to fly across the English Channel but the balloon exploded a half-hour into the flight. This unfortunate accident earned de Rozier the title "The First to Fly and the First to Die". It wasn't until the 1980s that technology once again allowed the Rozier balloons to become feasible.

Jean-Pierre Blanchard made the first piloted balloon flight in North America on January 9, 1793. Although a balloon has no propulsion system, a degree of directional control is possible through making the balloon rise or sink in altitude to find favorable wind directions.

Both the hot-air, or Montgolfière, balloon and the gas balloon are still in common use. Montgolfière balloons are relatively inexpensive as they do not require high-grade materials for their envelopes, and they are popular for balloonist sport activity.

Light gas balloons are predominant in scientific applications, as they are capable of reaching much higher altitudes for much longer periods of time. They are generally filled with helium. Although hydrogen has more lifting power, it is explosive in an atmosphere full of oxygen. With a few exceptions, scientific balloon missions are unmanned.

There are two types of light-gas balloons: zero-pressure and superpressure. Zero-pressure balloons are the traditional form of light-gas balloon. They are partially inflated with the light gas before launch, with the gas pressure the same both inside and outside the balloon. As the zero-pressure balloon rises, its gas expands to maintain the zero pressure difference, and the balloon's envelope swells.

At night, the gas in a zero-pressure balloon cools and contracts, causing the balloon to sink. A zero-pressure balloon can only maintain altitude by releasing gas when it goes too high, where the expanding gas can threaten to rupture the envelope, or releasing ballast when it sinks too low. Loss of gas and ballast limits the endurance of zero-pressure balloons to a few days.

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A superpressure balloon, in contrast, has a tough and inelastic envelope that is filled with light gas to pressure higher than that of the external atmosphere, and then sealed. The superpressure balloon cannot change size greatly, and so maintains a generally constant volume. The superpressure balloon maintains an altitude of constant density in the atmosphere, and can maintain flight until gas leakage gradually brings it down.

Superpressure balloons offer flight endurance of months, rather than days. In fact, in typical operation an Earth-based superpressure balloon mission is ended by a command from ground control to open the envelope, rather than by natural leakage of gas.

For air transport balloons must contain a gas lighter than the surrounding air. There are two types:

  • hot air balloons: filled with hot air, which by heating becomes lighter than the surrounding air; they have been used to carry human passengers since the 1790s;
  • balloons filled with:

Large helium balloons are used as high flying vessels to carry scientific instruments (as do weather balloons), or even human passengers.

Cluster ballooning uses many smaller gas-filled balloons for flight (see An Introduction to Cluster Ballooning).

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Balloons in the military

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The first military use of a balloon was at the Battle of Fleurus in 1794, when it was used by French Revolutionary troops to watch the movements of the enemy.

The first major-scale use of balloons in the military occurred during the American Civil War with the Union Army Balloon Corps established and organized by Prof. Thaddeus S. C. Lowe in the Summer of 1861. Initially the balloons were inflated with coke gas from municipal services and then walked out to the battlefield, an arduous and inefficient operation as the balloons had to be returned to the city every four days for re-inflation. Eventually hydrogen gas generators, a compact system of tanks and copper plumbing, were constructed which converted the combining of iron filings and sulphuric acid to hydrogen. The generators were easily transported with the uninflated balloons to the field on a standard buckboard. In all Lowe built seven balloons that were fit for military service.

The first application thought useful for balloons was mapmaking from aerial vantage points, thus Lowe's first assignment was with the Topographical Engineers. General Irvin McDowell, commander of the Grand Army of the Potomac, realized their value in aerial reconnaissance and had Lowe, who at the time was using his personal balloon the Enterprise, called up to the First Battle of Bull Run. In a later exercise, Lowe's first military balloon the Eagle was called to act as a Forward Artillery Observer (FAO) from which aerial station he was able to call in artillery fire, by a set order of flag signals, from an unseen position onto a Confederate encampment. This was a first for this method of artillery fire and the FAO is still used today from either ground or aerial positions.

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With his ability to inflate balloons from remote stations, Lowe had his balloon the Washington and two gas generators loaded onto a converted coal barge the George Washington Parke Custis. As he was towed down the Potomac, Lowe was able to ascend and observe the battlefield as it moved inward on the heavily forested peninsula. This would be the military's first claim of an aircraft carrier.

The Confederate Army made some relatively successful use of balloons, but they were gravely hampered by supplies due to the embargoes. They were forced to fashion their balloons from gaily colored silk dress-making material, and their use was limited by the infrequent supply of gas in Richmond. By the Summer of 1863, all balloon reconnaissance of the Civil War had ceased.

Image:Balloon sub hunting.jpg Hydrogen-filled balloons were also widely used during World War I (1914-1918) to detect enemy troop movements and to direct artillery fire. Observers phoned their reports to officers on the ground who then relayed the information to appropriate destinations. Because artillery was such an important factor in World War I, balloons were frequent targets of opposing aircraft. Though balloon companies of all combatants were protected by antiaircraft guns and patrolling fighters, casualties were frequently heavy.

The Aeronaut Badge was established by the United States Army in World War I to denote service members who were qualified balloon pilots. Observation balloons were retained well after the Great War, being used in the Russo-Finnish conflicts (1939-40 and 1941-45).

The Japanese launched thousands of balloon bombs to the US and Canada, carried in the jet stream; see fire balloons. Also, the British used balloons to carry incendiary devices to Germany between 1942 and 1944, see Operation Outward.

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See also

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ko:기구 it:Mongolfiera ja:気球 pl:Balon pt:Balão ru:Аэростат vi:Khí cầu zh:气球

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