A hot air balloon is a lighter-than-air aircraft consisting of a bag, called an envelope, which contains heated air. Suspended beneath is a gondola or wicker basket (in some long-distance or high-altitude balloons, a capsule), which carries passengers and a source of heat, in most cases an open flame caused by burning liquid propane. The heated air inside the envelope makes it buoyant, since it has a lower density than the colder air outside the envelope. As with all aircraft, hot air balloons cannot fly beyond the atmosphere. The envelope does not have to be sealed at the bottom, since the air inside the envelope is at about the same pressure as the surrounding air. In modern sport balloons the envelope is generally made from nylon fabric, and the inlet of the balloon (closest to the burner flame) is made from a fire-resistant material such as Nomex. Modern balloons have been made in many shapes, such as rocket ships and the shapes of various commercial products, though the traditional shape is used for most non-commercial and many commercial applications.
The hot air balloon is the first successful human-carrying flight technology. The first untethered manned hot air balloon flight in the world was performed in Paris, France, by Jean-François Pilâtre de Rozier and François Laurent d'Arlandes on November 21, 1783, in a balloon created by the Montgolfier brothers. Hot air balloons that can be propelled through the air rather than simply drifting with the wind are known as thermal airships.
History
Premodern and unmanned balloons
A precursor of the hot air balloon was the sky lantern (). Zhuge Liang of the Shu Han kingdom, during the Three Kingdoms era (220–280 CE), used these airborne lanterns for military signaling., cited in Joel Serrão, Dicionário de História de Portugal, Vol III. Porto: Livraria Figueirinhas, 1981, 184–185. The Mongolian army studied Kongming lanterns from China and used them in the Battle of Legnica during the Mongol invasion of Poland in the 13th century.Joseph Needham (1965). Science and Civilisation in China: Volume 4, Physics and Physical Technology, Part 2, Mechanical Engineering; rpr. Taipei: Caves Books Ltd. This is the first time ballooning was known in the western world.
In the 18th century the Portuguese Jesuit priest Bartolomeu de Gusmão in colonial Brazil envisioned an aerial apparatus named , which was the predecessor of the hot air balloon. The was intended to serve as an air vessel in order to facilitate communication and as a strategical device.Arquivo Nacional da Torre do Tombo. "Cartas Consultas e Mais Obras de Alexandre de Gusmão" (páginas do manuscrito 201–209). In 1709 John V of Portugal decided to fund Bartolomeu de Gusmão's project following a petition made by the Jesuit priest, and an unmanned demonstration was performed at Casa da Índia in the presence of John V and the queen, Maria Anna of Austria, with the Italian cardinal Michelangelo Conti, two members of the Portuguese Royal Academy of History, one Portuguese diplomat and one chronicler serving as witnesses. This event would bring some European attention to this event and this project. A later article dated on October 20, 1786, by the London Daily Universal Register would state that the inventor was able to raise himself by the use of his prototype. Also in 1709, the Portuguese Jesuit wrote (Short Manifesto for those who are unaware that is possible to sail through the element air); he also left designs for a manned air vessel.
In the 1970s, balloonist Julian Nott hypothesized that the Nazca Lines geoglyphs' creation two millennia ago could have been guided by Nazca leaders in a balloon, possibly the earliest hot air balloon flights in human history. To support this theory, in 1975 he designed and piloted the Nazca Prehistoric Balloon, claiming to have used only methods and materials available to the Pre-Inca Peruvians 1,000 years ago.
First manned flight
The French brothers Joseph-Michel and Jacques-Étienne Montgolfier developed a hot-air balloon in Annonay, Ardèche, France, and demonstrated it publicly on September 19, 1783, making an unmanned flight lasting 10 minutes. After experimenting with unmanned balloons and flights with animals, the first balloon flight with humans aboard, a tethered flight, performed on or around October 15, 1783, by Jean-Francois Pilatre de Rozier, who made at least one tethered flight from the yard of the Reveillon workshop in the Faubourg Saint-Antoine. Later that same day, Pilatre de Rozier became the second human to ascend into the air, reaching an altitude of , the length of the tether.Tom D. Crouch (2009). Lighter Than Air. The first free flight with human passengers was made a few weeks later, on November 21, 1783. King Louis XVI had originally decreed that condemned criminals would be the first pilots, but de Rozier, along with Marquis François d'Arlandes, petitioned successfully for the honor. The first military use of a hot air balloon happened on June 26, 1794 during the battle of Fleurus, when the French used the balloon for observation.
Modern balloons
Modern hot air balloons, with an onboard heat source, were developed by Ed Yost and Jim Winker, beginning during the 1950s; their work resulted in the first successful flight on October 22, 1960. The first modern hot air balloon to be made in the United Kingdom (UK) was the Bristol Belle, built in 1967. Presently, hot air balloons are used primarily for recreation.
Records Altitude On November 26, 2005 Vijaypat Singhania set the world altitude record for highest hot air balloon flight, reaching . He took off from downtown Mumbai, India, and landed south in Panchale.
The previous record of had been set by Per Lindstrand on June 6, 1988, in Plano, Texas.
Speed On January 15, 1991, Per Lindstrand (born in Sweden, but resident in the UK) and Richard Branson of the UK flew from Japan to Northern Canada in the “Virgin Pacific Flyer”. With a volume of 74,000 cubic meters (2.6 million cubic feet), the balloon envelope was the largest ever built for a hot air craft. Designed to fly in the trans-oceanic jet streams, the Pacific Flyer recorded the fastest ground speed for a manned balloon at .
Length The longest duration record was set by Swiss psychiatrist Bertrand Piccard (Auguste Piccard's grandson) and Briton Brian Jones, flying in the Breitling Orbiter 3. It was the first nonstop trip around the world by balloon. The balloon left Château-d'Oex, Switzerland, on March 1, 1999, and landed at 1:02 a.m. on March 21 in the Egyptian desert south of Cairo. The two men exceeded distance, endurance, and time records, traveling 19 days, 21 hours, and 55 minutes.
Briefest trip around the world Steve Fossett, flying solo, exceeded the record for briefest time traveling around the world on 3 July 2002 on his sixth attempt, Article by Konyukhov describing the experience. in 320 h 33 min. Steve Fossett and Fedor Konyukhov, both sub-class AM-15. Fedor Konyukhov flew solo round the world on his first attempt in a hybrid hot air/helium balloon from 11 to 23 July 2016 for a round-the world time of 268 h 20 min.
Construction
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.
Envelope Modern hot air balloons are usually made of materials such as ripstop nylon or dacron (a polyester).
During the manufacturing process, the material is cut into panels and sewn together, along with structural load tapes that carry the weight of the gondola or basket. The individual sections, which extend from the throat to the crown (top) of the envelope, are known as gores or gore sections. Envelopes can have as few as 4 gores or as many as 24 or more.
Envelopes often have a crown ring at their very top. This is a hoop of smooth metal, usually aluminium, and approximately in diameter. Vertical load tapes from the envelope are attached to the crown ring.
At the bottom of the envelope the vertical load tapes are sewn into loops that are connected to cables (one cable per load tape). These cables, often referred to as flying wires, are connected to the basket by carabiners.
Seams The most common technique for sewing panels together is called the French felled, French fell, or double lap seam. The two pieces of fabric are folded over on each other at their common edge, possibly with a load tape as well, and sewn together with two rows of parallel stitching. Other methods include a flat lap seam, in which the two pieces of fabric are held together simply with two rows of parallel stitching, and a zigzag, where parallel zigzag stitching holds a double lap of fabric.
Coatings
The fabric (or at least part of it, the top 1/3, for example) may be coated with a sealer, such as silicone or polyurethane, to make it impermeable to air. It is often the degradation of this coating and the corresponding loss of impermeability that ends the effective life of an envelope, not weakening of the fabric itself. Heat, moisture, and mechanical wear-and-tear during set-up and pack-up are the primary causes of degradation. Once an envelope becomes too porous to fly, it may be retired and discarded or perhaps used as a "rag bag": cold-inflated and opened for children to run through. Products for recoating the fabric are becoming available commercially.
Sizes and capacity A range of envelope sizes is available. The smallest, one-person, basket-less balloons (called "Hoppers" or "Cloudhoppers") have as little as of envelope volume; for a perfect sphere the radius would be around . At the other end of the scale, balloons used by commercial sightseeing operations may be able to carry well over two dozen people, with envelope volumes of up to . The most-used size is about , allowing to carry 3 to 5 people.
Vents
The top of the balloon usually has a vent of some sort, enabling the pilot to release hot air to slow an ascent, start a descent, or increase the rate of descent, usually for landing. Some hot air balloons have turning vents, which are side vents that, when opened, cause the balloon to rotate. Such vents are particularly useful for balloons with rectangular baskets, to facilitate aligning the wider side of the basket for landing.
The most common type of top vent is a disk-shaped flap of fabric called a parachute vent, invented by Tracy Barnes. The fabric is connected around its edge to a set of "vent lines" that converge in the center. (The arrangement of fabric and lines roughly resembles 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 open completely to collapse the balloon after landing.