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Hot air balloon

2007 Schools Wikipedia Selection. Related subjects: Air & Sea transport

   Hot air balloon in flight
   Enlarge
   Hot air balloon in flight

   Hot air balloons are the oldest successful human flight technology,
   dating back to the Montgolfier brothers' invention in Annonay, France
   in 1783. The first flight carrying humans was made on November 21,
   1783, in Paris by Pilâtre de Rozier and the Marquis d'Arlandes. Hot air
   balloons that can be propelled through the air rather than just being
   carried along by the wind are known as airships or, more specifically,
   thermal airships.

   Attractive aspects of ballooning include the exceptional quiet (except
   when the propane burners are firing), the lack of any perceptible
   feeling of movement and the birds-eye view. Since the balloon moves
   with the wind, the passengers feel absolutely no wind, except for brief
   periods during the flight when the balloon climbs or descends into air
   currents of different direction or speed.

   A hot air balloon consists of a bag called the envelope that is capable
   of containing hot air. Suspended beneath is the gondola or wicker
   basket (in certain, long distance or high altitude balloons, a capsule)
   which carries a source of heat capable of producing a sufficient
   temperature gradient between the air inside the envelope and the
   surrounding air mass to give enough lift to keep the balloon and its
   passengers aloft. Unlike gas balloons, the envelope does not have to be
   sealed at the bottom since the rising hot air only exerts pressure on
   the upper hemisphere of the balloon to provide lift. In today's sports
   balloons the envelope is generally made from nylon fabric and the mouth
   of the balloon (closest to the burner flame) is made from fire
   resistant material.

   Recently, balloon envelopes have been made in fantastic shapes, such as
   hot dogs, rocket ships, and the shapes of commercial products.
   Hot air balloons at night
   Enlarge
   Hot air balloons at night

History

   Unmanned hot air balloons are mentioned in Chinese history. Zhuge Liang
   in the Three Kingdoms era, Shu Kingdom, used airborne lanterns for
   military signaling. These lanterns are known as Kongming lanterns
   (孔明灯).

   There is also some speculation that hot air balloons were used by the
   Nazca Indians of Peru some 1500 years ago as a tool for designing vast
   drawings on the Nazca plain.
   Enlarge

   The first clearly recorded instances of balloons capable of carrying
   passengers used hot air to obtain buoyancy and were built by the
   brothers Josef and Etienne Montgolfier in Annonay, France. They were
   from a family of paper manufacturers who had noticed the ash rising in
   fires. After experimenting with unmanned balloons and flights with
   animals, the first balloon flight with humans on board took place on 19
   October 1783 with the physician Pilâtre de Rozier, the manufacture
   manager, Jean-Baptiste Réveillon and Giroud de Villette, at the Folie
   Titon in actual Paris. Officially, the first fly was 1 month later, 21
   November 1783. King Louis XVI had originally decreed that condemned
   criminals would be the first pilots, but a young physicist named
   Pilâtre de Rozier and the Marquis Francois d'Arlandes successfully
   petitioned for the honour. The first hot air balloons were basically
   cloth bags (sometimes lined with paper) with a smoky fire built on a
   grill attached to the bottom. They had a tendency to catch fire and be
   destroyed upon landing.

   The first military use of aircraft took place during the French
   Revolutionary Wars, when the French used a tethered Hydrogen balloon to
   observe the movements of the Austrian army during the Battle of Fleurus
   (1794). Hot air balloons were employed during the American Civil War.
   Though the military balloons used by the Union Army Balloon Corps under
   the command of Prof. Thaddeus S. C. Lowe were limp silk envelopes
   inflated with coke gas or hydrogen, the Confederate Army did attempt to
   counter with a rigid Montgolfier style hot air, or "hot smoke balloon."
   Captain John R. Bryant inflated his rigid cotton balloon with a fire of
   oil-soaked pine cones. The balloon was soon captured by Union forces as
   the Confederate's techniques of balloon handling were not competent.

Revival

   The first modern hot air balloon was designed and built in 1960 by Ed
   Yost. He made the first free flight of such an aircraft in Bruning,
   Nebraska on 22 October 1960. Initially equipped with a plastic envelope
   and kerosene fuel, Yost's designs rapidly moved onto using a modified
   propane powered "weed burner" to heat the air and lightweight nylon
   fabric for the envelope material.

   Today, hot air balloons are used primarily for recreation. There are
   some 7,000 hot air balloons operating in the United States.

   Hot air balloons are able to fly to extremely high altitudes. On
   November 26, 2005, Vijaypat Singhania set the world altitude record for
   highest hot air balloon flight, reaching 21,290 meters (69,852 feet).
   He took off from downtown Bombay, India and landed 240 km (150 miles)
   south in Panchale. The previous record of 19,811 meters (64,980 ft) had
   been set by Per Lindstrand on June 6, 1988 in Plano, Texas.

   The furthest that a hot air balloon has ever been flown is 7,671.91 km.
   On January 15, 1991, the Virgin Pacific Flyer balloon completed the
   longest flight in a hot air balloon when Per Lindstrand (born in
   Sweden, but resident in the UK) and Richard Branson of the UK flew from
   Japan to Northern Canada.

   With a volume of 74,000 m³ (2,600,000 ft³), the balloon envelope was
   the largest ever built for a hot air craft. Designed to fly in the
   trans-oceanic jetstreams the Pacific Flyer recorded the highest ground
   speed for a manned balloon at 245 mph (394 km/h).

   The longest duration hot air balloon flight ever made is 50 hours and
   38 minutes made by Michio Kanda and Hirosuke Tekezawa of Japan on
   January 2, 1997.

Construction and theory of operation

   A hot air balloon is partially inflated with cold air from a
   petrol-driven fan, before the propane burners are used for final
   inflation.
   Enlarge
   A hot air balloon is partially inflated with cold air from a
   petrol-driven fan, before the propane burners are used for final
   inflation.

   A hot air balloon for manned flight uses a single layered, fabric gas
   bag (lifting "envelope"), with an opening at the bottom called the
   mouth. Attached to the envelope is a basket, or gondola, for carrying
   the passengers. Mounted above the basket and centered in the mouth is
   the "burner" which injects a flame into the envelope, heating the air
   within. Raising the air temperature inside the envelope makes it
   lighter than the surrounding (ambient) air. This causes the balloon and
   its payload to rise.

   Modern hot air balloons are usually made of synthetic fabrics such as
   ripstop nylon, a light weight fabric of high strength. During the
   manufacturing process, the material is cut into panels and sewn
   together, along with structural load tapes (webbing) that carry the
   weight of the gondola or basket. The heater or burner is fueled by
   propane, a liquefied gas stored in pressure vessels, similar to high
   pressure forklift cylinders.

   The amount of lift (or buoyancy) provided by a hot air balloon depends
   primarily upon the difference between the temperature of the air inside
   the envelope and the temperature of the air outside the envelope. For
   most envelopes made of nylon fabric, the maximum internal temperature
   is limited to approximately 120 °C (250 °F). It should be noted that
   the melting point of nylon is significantly higher than these maximum
   operating temperature — about 230 °C (450 °F). However the lower
   temperatures are generally used because the higher the temperature, the
   more quickly the strength of the nylon fabric degrades over time. With
   a maximum operating temperature of 120 °C, balloon envelopes can
   generally be flown for between 400 and 500 hours before the fabric
   needs to be replaced. Many balloon pilots operate their envelopes at
   temperatures significantly below the maximum in order to extend the
   longevity of their envelope fabric.

   For typical atmospheric conditions, a hot air balloon requires about 3
   cubic meters of envelope volume in order to lift 1 kilogram (50
   ft³/lb). The precise amount of lift provided depends not only upon the
   internal temperature mentioned above, but the external temperature,
   altitude above sea level, and humidity of the surrounding air. On a hot
   day, the balloon cannot be loaded as much as on a cool day, because the
   temperature required for launch will exceed the maximum sustainable for
   nylon envelope fabric.

   In the lower atmosphere, the lift provided by a hot air balloon
   decreases about 3% for each 1,000 meters (1% per 1,000 ft) of altitude
   gained.
   A pair of Hopper balloons.
   Enlarge
   A pair of Hopper balloons.

   A range of envelope sizes is available. The smallest, one-person,
   basket-less balloons (called " Hoppers" or " Cloudhoppers") have less
   than 1,000 cubic meters (35,000 ft³) of envelope volume. At the other
   end of the scale are the balloons used by large commercial sightseeing
   operations that carry well over two dozen people and have envelope
   volumes of up to 15,000 cubic meters (600,000 ft³). However, most
   balloons are roughly 2,500 cubic meters (100,000 ft³) and carry 3 to 4
   people.

   The Rozier type of hybrid balloon, called after its creator,
   Jean-François Pilâtre de Rozier, has separate cell for helium as well
   as a cone below for hot air (as is used in a hot air balloon) to heat
   the helium at night.

   The direction of flight depends on the wind, but the altitude of the
   balloon can be controlled by changing the temperature of the air inside
   the envelope.
   The inside of a hot air balloon's envelope, seen from the gondola.
   Enlarge
   The inside of a hot air balloon's envelope, seen from the gondola.

   The top of the balloon usually has a vent of some sort. The most common
   type of vent is a disk-shaped flap of fabric called a parachute vent.
   The fabric is connected around its edge to a set of "vent lines" that
   converge in the centre. (The arrangement of fabric and lines looks
   roughly like a parachute -- thus the name.) These "vent lines" are
   themselves connected to a control line that runs to the basket. A
   parachute vent is opened by pulling on the control line. Once the
   control line is released, the pressure of the remaining hot air pushes
   the vent fabric back into place. A parachute vent can be opened briefly
   while in flight to initiate a rapid descent. (Slower descents are
   initiated by allowing the air in the balloon to cool naturally.) The
   vent is pulled completely open to collapse the balloon after landing.

   An older, and today less commonly used, style of vent is called a
   "Velcro-style" vent. This too is a disk of fabric at the top of the
   balloon. However, rather than having a set of "vent lines" that can
   repeatedly open and close the vent, the vent is secured by "hook and
   loop" fasteners (such as Velcro) and is only opened at the end of the
   flight. Balloons equipped with a "Velcro-style" vent typically have a
   second "maneuvering vent" built into the side (as opposed to the top)
   of the balloon.

   Some hot air balloons have turning vents which are side vents which,
   when opened, cause the balloon to rotate. Such vents are particularly
   useful for balloons with rectangular baskets in order to align the
   wider side of the basket for landing.

Hot air balloon manufacturers

   The largest manufacturer of hot air balloons in the world is Cameron
   Balloons of Bristol and part owned subsidiary company, Lindstrand
   Balloons of Oswestry, England. Aerostar International, Inc. of Sioux
   Falls, South Dakota is North America's largest balloon manufacturer and
   is a close second in world manufacturing (note: Aerostar will no longer
   be building balloons beginning January 2007). Firefly Balloons,
   formerly known as The Balloon Works, is another popular manufacturer of
   hot-air balloons located in Statesville, North Carolina. Another long
   time producer of hot air balloons is Head Balloons, Inc., located in
   Helen, Georgia.

   Cameron Balloons, and another English balloon manufacturing company,
   Thunder and Colt (since acquired by Cameron), have been the main
   innovators and developers of special shaped balloons. These hot air
   balloons use the same principle of lift as conventional inverted
   teardrop shaped balloons but often sections of the special balloon
   envelope shape make no contribution to the balloon's ability to stay
   afloat. They have been produced in great variety and with eye-popping
   invention and wit.

Flight techniques

   Hot air balloon being inflated by its propane burners prior to a dawn
   launch.
   Enlarge
   Hot air balloon being inflated by its propane burners prior to a dawn
   launch.
   Early Morning Departures
   Enlarge
   Early Morning Departures

   Most hot air balloon launches are made during the cooler hours of the
   day, at dawn or two to three hours before sunset. At these times of
   day, the winds are typically light making for easier launch and landing
   of the balloon. Flying at these times also avoids thermals, which are
   vertical air currents caused by ground heating that make it more
   difficult to control the balloon. In the extreme, the downdrafts
   associated with strong thermals can exceed the ability of a balloon to
   climb and can thus force a balloon into the ground.

Sequence

   A hot air balloon flight starts with unpacking the balloon from its
   carrying bag. A gasoline-powered fan is used to blow cold (outside) air
   into the envelope. The cold air partially inflates the balloon to
   establish its basic shape before the burner flame is aimed into the
   mouth heating the air inside. A crew member stationed opposite the
   mouth, holds a rope (crown line) tied to the apex (crown) of the
   envelope. The "crown-man" role is two fold, one is to prevent the
   envelope from excessive sway and two is to prevent the balloon rising
   until it is sufficiently buoyant. Once the balloon is upright, pilot
   and passengers climb into the basket. When the pilot is ready for
   launch, more heat is directed into the envelope and the balloon lifts
   off.
   Setting up and taking off
   Enlarge
   Setting up and taking off

   During the flight, the pilot's only ability to steer the balloon is the
   ability to climb or descend into wind currents going different
   directions. Thus, it is important for the pilot to determine what
   direction the wind is blowing at altitudes other than the balloon's
   altitude. To do this, the pilot uses a variety of techniques. For
   example, to determine wind directions beneath the balloon a pilot might
   simply spit or release a squirt of shaving cream and watch this
   indicator as it falls to determine where possible turns are (and their
   speed). Pilots are also looking for other visual clues such as flags on
   flagpoles, smoke coming from chimneys, etc. To determine wind
   directions above the balloon, the pilot will obtain a weather forecast
   prior to the flight which includes upper level wind forecasts. The
   pilot will also send up a helium pilot balloon, known as a met-balloon
   in the UK and pibal in the USA, prior to launch to get information
   about what the wind is actually doing. Another way to determine actual
   wind directions is to watch other hot air balloons, which are the
   equivalent of a large met-balloon.

   The crew then pack up inflation equipment and follow the balloon with
   the retrieve vehicle.

   Once the balloon has landed, the envelope is deflated and detached from
   the basket. The envelope is then packed into its carrying bag. The
   burner and the basket are separated and all components are packed into
   the retrieve vehicle.

Control

   The top of a hot air balloon generally has a flap of fabric (often
   referred to as a parachute) that can be pulled partially open (via a
   long line connecting the parachute device to the gondola or basket) to
   allow the balloon pilot to release hot air in an emergency or for
   better control of descent. The flap is pulled completely open to
   collapse the balloon after landing.
   Hot air balloons in flight
   Enlarge
   Hot air balloons in flight

   In competition, the pilots need to be able to read different wind
   directions at different altitudes. Balloon competitions are often
   called "races" but they're most often a test of accuracy, not speed.
   For most competitive balloon flights, the goal is to fly as close as
   possible to one or more exact points called "targets". Once a pilot has
   directed the balloon as close as possible to a target, a weighted
   marker with an identifying number written on it is dropped. The
   distance between a pilot's marker and that target determines his or her
   score. During some competitive flights, pilots will be required to fly
   to 5 or more targets before landing. To assist with navigation,
   topographic maps and GPS units are used. Another common form of
   competition is the "Hare and Hound" race. The Hare balloon takes off a
   set amount of time before the Hound balloons and typically flies with
   multiple altitude changes to make it more difficult for the chasing
   balloons to match its flight path. After a set amount of flight time,
   the Hare will land and typically lay out a target cross for the Hounds
   to drop their weighted markers near. As above, the distance between a
   pilot's marker and the target determines his or her score.

   Some experienced pilots are able to take a flight in one direction then
   rise to a different altitude to catch wind in a returning direction.
   With experience, luck, and the right conditions, some pilots are able
   to control a precision landing at the destination. On rare occasions,
   they may be able to return to the launch site at the end of the flight.
   This is sometimes called a box effect, usually when flying in valleys
   with drainage winds.

Hazards

   The dangers of the sport include excessive (vertical or horizontal)
   speed during landing, mid-air collisions that may collapse the balloon,
   and colliding with high voltage power lines. It is the last of these,
   contact with power lines, that poses the greatest danger. For instance,
   roughly 90% of serious ballooning accidents in the US involve power
   line strikes. One reason for the high frequency of such incidents is
   the fact that pilots often attempt to land their balloons on or near
   roads in order to reduce the amount of off-road driving necessary to
   recover the balloon. However, in most rural areas where balloons fly,
   roads usually have power lines running along them.

   The recent advent of vertically aerodynamic sport balloons which can
   climb and descend at twice the rate of a conventional balloon (1500
   ft/min as opposed to 700 ft/min) has significantly increased the danger
   posed by collision or accidental ground impact during competition. Many
   pilots have also reported strange aerodynamic performance during very
   aggressive climbs, such as greatly reduced air resistance at vertical
   speeds over +1500 ft/min, resulting in a sudden, unexpected
   acceleration. At present there is little research into high
   vertical-speed balloon flight to understand this phenomenon.

   The FAA requires balloons to fly under visual flight rules. If equipped
   with lights that make it visible to other aircraft, balloons can fly in
   the dark. However, such flights are usually limited to either "dawn
   patrol" flights that begin before sunrise with landings made after
   there is sufficient light to see any obstacles or to race/record
   flights that typically go throughout the night and the landing again
   made during daylight hours.

   Tethered balloons are sometimes inflated at night, an event called a
   "night glow" for the impressive visual effects. At such events, pilots
   will usually operate the liquid valve known as the whisper burner (or
   sometimes called the cow burner) on the burner creating a spectacular
   bright orange flame instead of the main valve which creates the more
   typical (and efficient) blue flame.

Events

   There are many regular gatherings of balloons and balloonists around
   the world. Most of these events are held on annual basis. The
   festivities provide both a place for balloonists to interact as well as
   a venue for entertaining spectators. Events range in size from a few
   balloons and no spectators to hundreds of balloons with hundreds of
   thousands of spectators.

Gallery

   PREPARING FOR FLIGHT: This large wicker balloon basket holds 16
   passengers. The pilot is climbing out after his pre-flight tests

   FINAL INFLATION: Firing the propane burners to complete inflation

   LANDING: An unusual top view of the basket, after tipping onto its side
   during landing at dusk

   RETRIEVAL: The envelope is packed back into its bag for storage until
   the next flight
   Retrieved from " http://en.wikipedia.org/wiki/Hot_air_balloon"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
