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    Hot air Balloon Experiments

    Hot air Balloon Background Information

    Definition

    A hot air balloon is a lighter-than-air craft in which air or gas heated by a flame is trapped in a large fabric or other materials bag.

    Basics

    The hot air balloon is the oldest successful human-carrying flight technology and is a subset of balloon aircraft.

    On November 21, 1783, in Paris, France, the first manned flight was made by Jean-François Pilâtre de Rozier and François Laurent d'Arlandes in a hot air balloon created by the Montgolfier brothers. Recently, balloon envelopes have been made in all kinds of shapes, such as hot dogs, rocket ships, and the shapes of commercial products. Hot air balloons that can be propelled through the air rather than just being pushed along by the wind are known as airships or, more specifically, thermal airships.

    A hot air balloon consists of a bag called the envelope that is capable of containing heated air. Suspended beneath is the gondola or wicker basket (in some long-distance or high-altitude balloons, a capsule) which carries the passengers and (usually) a source of heat, usually an open flame. The heated air inside the envelope makes it buoyant since it has a lower density than the relatively cold air outside the envelope. Unlike gas balloons, the envelope does not have to be sealed at the bottom since the air near the bottom of the envelope is at the same pressure as the surrounding air. In today's sport 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 such as Nomex.

    The first clearly recorded instance of a balloon carrying passengers used hot air to generate buoyancy and was built by the brothers Joseph-Michel and Jacques-Etienne Montgolfier in Annonay, France. After experimenting with unmanned balloons and flights with animals, the first tethered balloon flight with humans on board took place on October 19, 1783 with the scientist Jean-François Pilâtre de Rozier, the manufacture manager, Jean-Baptiste Réveillon and Giroud de Villette, at the Folie Titon in Paris. The first free flight with human passengers was on November 21, 1783. King Louis XVI had originally decreed that condemned criminals would be the first pilots, but de Rozier, along with Marquis Francois d'Arlandes, successfully petitioned for the honor.

    Modern hot air balloons, with an onboard heat source, were pioneered by Ed Yost, beginning in the 1950s; his work resulted in his first successful flight, on October 22, 1960. The first modern-day hot air balloon to be built in the United Kingdom (UK) was the Bristol Belle in 1967. Today, hot air balloons are used primarily for recreation.

    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 or throat. 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. The heater or burner is fueled by propane, a liquefied gas stored in pressure vessels, similar to high pressure forklift cylinders.

    A balloon may be outfitted with a variety of instruments to aid the pilot. These commonly include an altimeter, a rate of climb (vertical speed) indicator, envelope (air) temperature, and ambient (air) temperature. A GPS receiver can be useful to indicate ground speed (traditional aircraft air speed indicators would be useless) and direction.

    Generating lift: Thermal image showing temperature variation in a hot air balloonRaising the air temperature inside the envelope makes it lighter than the surrounding (ambient) air. The balloon floats because of the buoyant force exerted on it. This force is the same force that acts on objects when they are in water and is described by Archimedes' principle. 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 this 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 (250 °F), 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.

    Standard hot air balloons are called Montgolfiere balloons and rely solely on the buoyancy of hot air provided by the burner and contained by the envelope. This style of balloon was developed by the Montgolfier brothers, and had its first public demonstration on 4 June 1783 with an unmanned flight lasting 10 minutes, followed later that year with manned flights.

    The 1785 Rozière balloon, a type of hybrid balloon, named after its creator, Jean-François Pilâtre de Rozier, has a separate cell for a lighter than air gas (typically helium,) as well as a cone below for hot air (as is used in a hot air balloon) to heat the helium at night. Hydrogen gas was used in the very early stages of development but was quickly abandoned due to the obvious danger of introducing an open flame near the gas. All modern Roziere balloons now use helium as a lifting gas

    Solar balloons are hot air balloons that use just solar energy captured by a dark envelope to heat the air inside.

    To help ensure the safety of pilot and passengers, a hot air balloon may carry several pieces of safety equipment.

    As with aircraft, hot air balloons require regular maintenance in order to remain airworthy. As aircraft made of fabric and that lack direct horizontal control, hot air balloons may occasionally require repairs to rips or snags. While some operations, such as cleaning and drying, may be performed by the owner or pilot, other operations, such as sewing, must be performed by a qualified repair technician and recorded in the balloon's maintenance log book.

    Depending on the size of the balloon, location, and intended use, hot air balloons and their pilots need to comply with a variety of regulations.

    The largest manufacturer of hot air balloons in the world is Cameron Balloons of Bristol, England, who also own Lindstrand Balloons of Oswestry, England.

    Topics of Interest

    A Zeppelin is a type of rigid airship pioneered by the German Count Ferdinand von Zeppelin in the early 20th century. It was based on designs he had outlined in 1874 and detailed in 1893. His plans were reviewed by committee in 1894 and patented in the United States on March 14, 1899. Given the outstanding success of the Zeppelin design, the term zeppelin in casual use came to refer to all rigid airships.

    Lighter than air refers to gases which are buoyant in air because they have densities lower than that of air (about 1.2 kg/m3, 1.2 g/l). Some of these gases are used as lifting gases in lighter-than-air craft, which include free balloons, moored balloons, and airships, to make the whole craft, on average, lighter than air. (Heavier-than-air aircraft include aeroplanes, gliders and helicopters.)

    A balloon satellite ("satelloon") is a satellite that is inflated with gas after it has been put into orbit.

    A barrage balloon is a large balloon tethered with metal cables, used to defend against low-level attack by aircraft by damaging the aircraft on collision with the cables, or at least making the attacker's approach more difficult. Some versions carried small explosive charges that would be pulled up against the aircraft to ensure its destruction. Barrage balloons were only regularly employed against low-flying aircraft, the weight of a longer cable making them impractical for higher altitudes.

    The Bristol International Balloon Fiesta is held during August in Bristol, England. Teams from the UK and other parts of the world bring their hot air balloons to the site and participate in mass ascents where as many as 100 balloons may launch at a time.

    The Cinebulle is a hot air balloon specially adapted for filming. It uses a propeller on the back like a microlight.

    An espionage balloon is a hot air balloon used for spying.

    High altitude balloons are unmanned balloons, usually filled with helium or hydrogen that are released into the stratosphere, generally reaching between 60,000 and 120,000 feet (18,000 - 36,500m). The most common type of high altitude balloons are weather balloons, other purposes may involve scientific groups and universities for conducting experiments in the upper atmosphere, and modern balloons generally contain electronic equipment such as radio transmitters, cameras, and sometimes satellite navigation systems, such as GPS receivers.

    A blimp, or non-rigid airship, is an airship without an internal supporting framework or keel. A non-rigid airship differs from a semi-rigid airship and a rigid airship (e.g., a Zeppelin) in that it does not have any rigid structure, neither a complete framework nor a partial keel, to help the airbag maintain its shape. Rather, these aircraft rely on both a higher pressure of the lifting gas (usually helium) inside the envelope and the strength of the envelope itself.

    Observation balloons are balloons that are employed as aerial platforms for intelligence gathering and artillery spotting. Their use began during the French Revolutionary Wars, reaching their zenith during World War I, and they continue in limited use today.

    Research balloons are balloons that are used for scientific research. They are usually (though not always) unmanned, filled with a lighter-than-air gas like helium, and fly at high altitudes.

    Skyhook balloons were balloons developed by Otto C. Winzen and used by the United States Navy Office of Naval Research in the late 1940s and in the 1950s for atmospheric research, especially for constant-level meteorological observations at very high altitudes. Instruments like the Cherenkov detector were first used on skyhook balloons.

    The Gatineau Hot Air Balloon Festival is a yearly festival, held in Gatineau, Quebec, Canada, and organized by the city, during which hundreds of hot air balloons are flown. It is normally held over several days in late-August and early September during the Labor Day Weekend.

    Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License and Creative Commons Attribution-ShareAlike License.)

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