• Build an indoor hot air balloon made out of a plastic film dry cleaner bag
  
• Demonstrate how hot air expands a balloon and a cold air one contracts it
  
• Make a Hot air Balloon from a Teabag
  
• Hot Air Balloon Laboratory for Lesson Plans and Science Fair Projects
  
• Build a Hot Air Balloon from Paper
  
• Hot air balloon construction 1
  
• Hot air balloon construction 2
  
• Make your own solar-powered hot air balloons out of black trash bags
  
• Automated Hot Air Ballooning
  
• Radio Controlled Hot Air Balloons
  

See also Balloons

Hot air balloon in flight

The hot air balloon is the oldest successful human-carrying flight technology, dating back to its invention by the Montgolfier brothers in Annonay, France in 1783. The first flight carrying humans was made on November 21, 1783, in Paris by Jean-François Pilâtre de Rozier and François Laurent d'Arlandes.

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 commonly, 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 a source of heat. 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 rising hot air only exerts pressure on the upper hemisphere of the balloon to provide lift. 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.

Recently, balloon envelopes have been made in fantastic shapes, such as hot dogs, rocket ships, and the shapes of commercial products.

History

Premodern Balloon

A Kongming lantern, the oldest type of hot air balloon.

Unmanned hot air balloons are popular in Chinese history. Zhuge Liang of the Shu Han kingdom, in the Three Kingdoms era, used airborne lanterns for military signaling. These lanterns are known as Kongming lanterns (孔明灯).^[1][2]

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.^[3]

First recorded manned balloon flight

This 1818 technical illustration shows early balloon designs.

The first clearly recorded instances of balloons capable of carrying passengers used hot air to obtain buoyancy and were built by the brothers Joseph-Michel and Jacques-Etienne Montgolfier in Annonay, France. These brothers came from a family of paper manufacturers and 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 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. Officially, the first flight 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 Jean-François Pilâtre de Rozier and the Marquis Francois d'Arlandes successfully petitioned for the honor.^[4][5][6] 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, although this was infrequent.

Military use

A model of the Montgolfier brothers balloon at the London Science Museum

The first military use of aircraft in Europe 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 (town gas) or hydrogen.

The first modern day hot air balloon to be built in the United Kingdom (UK) was the Bristol Belle in 1967.

Today

Today, hot air balloons are used primarily for recreation. There are some 7,500 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 metres (69,849 feet). He took off from downtown Bombay, India and landed 240 kilometres (149 miles) south in Panchale.^[7] The previous record of 19,811 m (64,997 ft) had been set by Per Lindstrand on June 6, 1988 in Plano, Texas. As with all registered aircraft, oxygen is needed for all crew and passengers for any flight that reaches and exceeds an altitude of 12,500 ft (3,810 m).

The Virgin Pacific Flyer capsule on a frozen lake in the Canadian tundra after the first and only crossing of the Pacific in a hot air balloon. Most of the giant jettisonable propane fuel tanks are no longer attached. One still hangs in front of the two-man sealed pressurized capsule. The flight holds the distance record for a hot air balloon.

The furthest that a hot air balloon has ever been flown is 7,671.91 km (4,767.23 mi). 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 cubic metres (2,600,000 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 highest ground speed for a manned balloon at 245 mph (394.3 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.^[8]

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. The basket is usually made of wicker and rattan, but can be made of aluminium. 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 light-weight and strong synthetic fabrics such as ripstop nylon, or dacron (a polyester).^[9]

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. Vertical rows of triangular panels that are referred to as gores. Envelopes can have as few as 4 gores or as many as 24 or more.^[10]

Envelopes often have a crown ring at their very top. This is a hoop of smooth metal, usually aluminum and approximately 1 ft (0.3 m) in diameter, to which vertical load tapes attach.

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.^[11] It is often the degradation of this coating and the corresponding loss of impermiability 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 used as a 'rag bag': cold inflated and opened for children to run through. Products for recoating the fabric are becoming commercially available.^[12]

Envelope sizes

A range of envelope sizes is available. The smallest, one-person, basket-less balloons (called "Hoppers" or "Cloudhoppers") have less than 1,000 m³ (35,000 ft³) of envelope volume (for a perfect sphere this would mean a radius of around 13.3 m (43.6 ft)). 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 m³ (600,000 ft³). However, most balloons are roughly 2,500 m³ (100,000 ft³) and carry 3 to sometimes 4 people.

Vents

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 center. (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.

Burner

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

The burner unit gasifies liquid propane, mixes it with air, ignites the mixture, and directs the flame and exhaust into the mouth of the envelope. The unit may consist of one or more individual burners of which the pilot may use one or more at a time to generate the desired heat. Each burner is characterized by a metal coil of propane tubing through which the flame shoots in order to preheat the incoming liquid propane.

The burner unit may be suspended from the mouth of the envelope, or rigidly supported over the basket. The burner unit may be mounted on a gimbal to enable the pilot to aim the flame and avoid overheating the envelope fabric.

The pilot actuates a burner by opening a propane valve, called a blast valve. The valve may be spring loaded so that it closes automatically, or it may stay open until closed by the pilot. The burner has a pilot light to ignite the propane and air mixture. The pilot light may be lit by the pilot with an external device, such as a flint striker or a lighter, or with a built-in piezo electric spark.^[13]

A burner may have a secondary propane valve that releases propane more slowly and thereby generates a different sound. This is called a whisper burner and is used for flight over livestock to lessen the chance of spooking them. It also generates a more yellow flame and is used for night glows because it lights up the inside of the envelope better than the primary valve.

Burners can generate heat on the order of 30 million BTUs (31,651,677 kilojoule).^[14]

Fuel tanks

Propane fuel tanks are usually cylindrical pressure vessels made from aluminum, stainless steel, or titanium with a valve at one end to feed the burner and to refuel. They may have a fuel gauge and a pressure gauge. Common tank sizes are 10 (38), 15 (57), and 20 (76) US gallons (litres).^[11]

The pressure necessary to force the fuel through the line to the burner may be supplied by the vapor pressure of the propane itself, if warm enough, or by the introduction of an inert gas such as nitrogen^[13]. Tanks may be preheated with electrical heat tapes to produce sufficient vapor pressure for cold weather flying.^[15] Warmed tanks will usually also be wrapped in an insulating blanket to preserve heat during the setup and flight.

Instrumentation

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.^[16] A GPS receiver can be useful to indicate ground speed (traditional aircraft air speed indicators would be useless) and direction.

Combined mass

The combined mass of an average system can be calculated as follows

• the envelope: 250 lb, 113 kg
• basket: 140 lb, 63.5 kg
• burner: 50 lb, 22.7 kg
• 3 fuel tanks with fuel: 3 × 135 lb = 405 lb, 184 kg
• 5 passengers: 5 × 150 lb each = 750 lb, 340 kg
• the air in the envelope (100,000 ft³ at 0.062 lb/ft³ = 3.1 tons, 2,812 kg) - but at 120 °C, the density of dry air is 0.898 kg/m³ which is 0.056 lb/ft³, giving a weight of 2,551  kg

For a total of 3,538 kg or about 3.9 tons^[11] (or 3,227 kg with the adjustment above)

Theory of operation

Generating lift

A pair of Hopper balloons.

Raising the air temperature inside the envelope makes it lighter than the surrounding (ambient) air. This causes the balloon and its payload to rise. 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 (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.

A Virgin hot air balloon flying over Cambridge.

For typical atmospheric conditions, a hot air balloon requires about 3 m³ 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.^[17]

A note on the physics: according to Archimedes' principle, the uplift on a balloon is equal to the weight of unheated air displaced by the balloon. As the density of air at 20 °C is about 1.2 kg/m³ (see density of air) which is 0.07476 lb/ft³, the uplift for a balloon of 100,000 ft³ would be 7476 lb, or 3398 kg. This should be compared with the total mass stated in the previous section.

Hybrids

The Rozière type of hybrid balloon, called after its creator, Jean-François Pilâtre de Rozier, has a 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.

Solar

Solar balloons are hot air balloons that use just solar energy captured by a dark envelope to heat the air inside.^[18]

Safety equipment

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

In the basket

In order to relight the burner, in case the pilot light goes out and the optional piezo ignition fails, the pilot should have ready access to a flint spark lighter.

Many systems, especially those that carry passengers have completely redundant fuel and burner systems: two fuel tanks, connected to two separate hoses, which feed two distinct burners. This enables a safe landing in the case of a clog somewhere in one system or if a system must be disabled because of a fuel leak.

On the occupants

At a minimum the pilot should wear flame resistant gloves. These can be made of leather or some more sophisticated material, such as nomex. These will enable the pilot to shut off a gas valve in the case of a leak even if there is a flame present. Quick action on the pilot's part to stop the flow of gas can turn a potential disaster into an inconvenience.

At a minimum the pilot should wear clothes made of natural fibers. These will singe and not burn readily if brought into contact with an open flame. Many synthetic fibers, unless especially formulated for use near flame or high temperatures like nomex, will melt onto the wearer and can cause severe burning.

Some balloon systems, especially those that hang the burner from the envelope instead of supporting it rigidly from the basket, require the use of helmets by the pilot and passengers.

On the ground crew

The ground crew should wear gloves on their hands whenever the possibility of handling ropes or lines exists. The mass and exposed surface to air movement of a medium sized balloon is sufficient to cause rope burns to the hands of anyone trying to stop or prevent movement.

The ground crew should also wear sturdy shoes and at least long pants in case of the need to access a landing or landed balloon in rough or overgrown terrain.

Maintenance and repair

As 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.

Maintenance

To ensure long life and safe operation, the envelope should be kept clean and dry. This prevents mold and mildew from forming on the fabric and abrasion from occurring during packing, transport, and unpacking due to contact with foreign particles. In the event of a landing in a wet (because of precipitation or early morning or late evening dew) or muddy location (farmer's field), the envelope should be cleaned and laid out or hung to dry.

The burner and fuel system must also be kept clean to ensure safe operation on demand. Damaged fuel hoses need to be replaced. Stuck or leaky valves must be repaired or replaced.

The wicker basket may require occasional refinishing or repair. The skids on its bottom may require occasional replacement.

Repair

In the case of a snag, burn, or rip in the envelope fabric, a patch may be applied or the affected panel completely replaced. Patches may be held in place with glue, tape, stitching, or a combination of these techniques. Replacing an entire panel requires the stitching around the old panel to be removed, and a new panel to be sewn in with the appropriate technique, thread, and stitch pattern.

Licensing

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.

Balloons

In the USA, balloons below a certain size (empty weight of less than 254 pounds or 115 kg) can be used as an ultralight aircraft and cannot carry passengers, except for pilot training. Anything larger than that must be registered (have an N-number), have an airworthiness certificate, and pass annual inspections.

Pilots

In the United States, a pilot of a hot air balloon must have a pilot certificate from the Federal Aviation Administration (FAA) and it must carry the rating of "Lighter-than-air free balloon", and unless the pilot is also qualified to fly gas balloons, will also carry this limitation: "Limited to hot air balloons with airborne heater".

In order to carry paying passengers for hire (and attend some balloon festivals), a pilot must have a commercial pilot certificate. Commercial hot air balloon pilots may also act as hot air balloon flight instructors.

A pilot does not need a license to fly an ultralight aircraft, but training is highly advised, and some hot air balloons meet the criteria.

While most balloon pilots fly for the pure joy of floating through the air, many are able to make a living as a professional balloon pilot. Some professional pilots fly commercial passenger sightseeing flights, while others fly corporate advertising balloons.^[19]

See also

• Airship
• Aviation
• Balloon (aircraft)
• Balloon satellite
• Barrage balloon
• Cinebulle
• Cluster ballooning
• Espionage balloon
• First flying machine
• Gas balloon
• High altitude balloon
• Hopper balloon
• Hot air balloon festivals
• Hot air ballooning
• Lighter than air
• List of balloon uses
• Montgolfier brothers
• Non-rigid airship (Blimp)
• Observation balloon
• Research balloon
• Skyhook balloon
• Solar balloon
• Thermal airship (Hot air airship)
• Zeppelin

Notes

References

• Needham, Joseph (1986). Science and Civilization in China: Volume 4, Physics and Physical Technology, Part 2, Mechanical Engineering. Taipei: Caves Books Ltd.

External links

Wikimedia Commons has media related to:

Hot air balloon

Construction techniques

• XLTA.org - A site focusing on building your own hot air balloon
• Hot Air Balloon Reference - Background, History, Raw Materials, and the Manufacturing Process

History

• Possible prehistoric Nazca hot air balloon
• Balloon History - More information about the history of hot air balloons
• History of Ballooning (Student Essay) - Student Essay on History of Ballooning

Misc

• Hot Air Balloon Simulator - learn the dynamics of a hot air balloon on the Internet based simulator
• The Biggest Italian Balloons Festival, in Ferrara
• Hot Air Ballooning
• Balloon quotations
• High-resolution hot air balloon photos
• Balloon photo database
• Hot Air Balloon Newspaper Video and Picture Europa

Hot air balloon pilot and passenger in basket

Hot air ballooning is the activity of flying hot air balloons. Attractive aspects of ballooning include the exceptional quiet (except when the propane burners are firing), the lack of a feeling of movement, and the bird's-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.

For information on hot air balloons, see the related article.

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.[1]

First recorded flight

A model of the Montgolfier brothers balloon at the London Science Museum

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 October 19, 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 flight 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 honor. 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.

Military use

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.

Modern 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 in flight

Today, hot air balloons are used primarily for recreation. There are some 7,500 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. However, like all registered aircraft, oxygen is needed for all crew and passengers for any flight that reaches and exceeds an altitude of 12,500 feet.

On January 15, 1991, a balloon carrying Per Lindstrand (born in Sweden, but resident in the UK, and Richard Branson of the UK flew from Japan to Northern Canada, completing 7,671.91 km. This record was shattered on March 21 1999 when the Breitling Orbiter 3 touched down in Egypt, having circumnavigated the globe and set records for duration (19 days, 21 hours and 55 minutes) and distance (46,759 km).

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).

Flight techniques

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

Preflight preparation

Before a safe hot air balloon flight can begin, the pilot must check the weather and select a suitable take-off point. The current and forecast weather must have sufficient visibility for the pilot to see and avoid obstructions (little or no fog or low clouds) and sufficiently slow winds to allow take off and landing (less than 5 or 10 mph depending on skill and experience of pilot, passengers, and ground crew).

The take-off point must be large enough to lay out and inflate the envelope and clear of obstructions such as power lines and poles, trees, and buildings to allow lift-off under the predicted wind conditions. Finally, the take-off point must be situated such that the predicted winds will move the balloon in the direction of suitable landing sites. Taking off from a location that is directly up wind of a hazard, such as a large body of water, a large metropolitan area, or a large uninterrupted forest, without sufficient fuel to pass over the hazard is not safe.

Set up

Hot air balloon being inflated by its propane burners prior to a dawn launch.

The next step in a hot air balloon flight is unpacking the balloon from its carrying bag, laying it out on the ground, and connecting it to the basket and burner. A fan (often gasoline-powered) 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 twofold: one is to prevent the envelope from excessive sway, and two is to prevent the envelope from rising before 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.

The crew then pack up inflation equipment and follow the balloon with the retrieve vehicle (also called a chase vehicle).

Flight

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.

Control

The inside of a hot air balloon's envelope, seen from the gondola.

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 pilot may open one or more burner blast valves to increase the temperature inside the envelope, thereby increasing lift, and thus ascend or slow or stop a descent. The pilot may also open a vent, if the envelope is so equipped, to let hot air escape, decreasing the temperature inside the envelope, thereby decreasing lift, and thus descend or slow or stop an ascent. Absent any action by the pilot, the air inside the envelope will slowly cool, by seepage or by contact with cooler outside air, and slowly provide less lift.

Delayed response

One of the tricks involved in flying a balloon is learning to deal with the delayed response. To slow or stop a descent requires the pilot to open a burner blast valve. This sends hot combustion exhaust through the mouth into the envelope where it expands and forces some cooler air out of the mouth. This lightens the total weight of the system and increases its buoyancy, but not immediately. From the time that the burner is lit until the balloon slows or stops its descent can take 30 seconds or more, depending on its rate of descent, how cold it has become, and how powerful the burner. This delay requires a great deal of anticipation on the part of the pilot.

Steerage

The ability to change direction with altitude is called steerage. In the ideal case, in the northern hemisphere, wind direction turns to the right with an increase in altitude. This is due to the Coriolis effect. Winds spiral clockwise, when seen from above, out of a high pressure system and counter clockwise into a low pressure system. However, air traveling close to the ground will tend to move in more of a straight line from high to low pressure due to drag with the ground. Thus, a pilot may hope to find a turn to the left during the descent to landing. In the southern hemisphere, the direction of the spirals are reversed. In reality, interaction with an uneven terrain may lessen or completely eliminate this phenomenon.

Level Flight

The burner is designed to create enough heat to warm up the balloon quickly. It is most efficient only when wide open. There is no good way to maintain the exact temperature required to maintain equilibrium.

Add to that the fact that when a hot air balloon is not actively being heated, it is cooling off. This means that it is in perfect equalibrium only momentarily. The rest of the time it is either too warm or too cool and so either climbing or decending.

These two facts together mean that under most conditions level flight is anything but. The goal of the pilot is to light the burner at the right interval and for the right duration (a few seconds) to keep the balloon slowly drifting up and down about the desired altitude.

An exception is made when flying close to the ground, as in an approach to a landing. Then the burner may be lit for very short bursts at a much higher frequency, thus sacrificing efficiency for accuracy.

Chase

A typical chase vehicle with room for the equipment, chase crew, pilot, and all passengers.

While it is certainly possible to enjoy the sport of hot air ballooning without a chase vehicle, returning from the landing site by foot, bicycle, or hitch hiking, many balloonists opt to be followed by their ground crew in some sort of chase vehicle. Crew at the landing site can aid with the landing itself, by catching a drop line and guiding the balloon into a tight space; with extracting the balloon system from a remote location, such as deep in a farmer's field; and with packing up all the equipment.

There are two primary options in chase systems: with a trailer or without. A trailer can provide a lot more room but at the cost of being more difficult to maneuver, especially when turning around in tight locations. A pickup truck or van by itself can be a lot more maneuverable but at the cost of squeezing all the equipment, crew, pilot, and passengers into a single vehicle. Many chase vehicles are fitted with a cargo liftgate to aid in loading heavy equipment into the cargo space (the envelope itself can weigh 250 lbs or more).

Communication between the balloon and chase vehicle can be accomplished by two-way radio, mobile phone, or even shouting, when they are close enough together.

Landing

The Virgin Pacific Flyer capsule on a frozen lake in the Canadian tundra after the first and only crossing of the Pacific in a hot air balloon. Most of the giant jettisonable propane fuel tanks are no longer attached. One still hangs in front of the two-man sealed pressurized capsule. The flight holds the distance record for a hot air balloon.

Most pilots try to perform as smooth a landing as possible. This becomes difficult if the air at ground level is moving at more than 5 mph or so. If the balloon is moving at this speed or more when it contacts the ground, the basket (which usually does not have wheels of any kind on the bottom) may drag for a bit or even tip over. Even the presence of ground crew may not help much. The combined weight (for an average passenger-carrying system as calculated above) can easily exceed the weight of a large automobile. (It is best not to be on the downwind side of a landing balloon to avoid being pinned between it and a hard place.) Pilots can improve the situation by landing in a spot protected from the wind, such as behind a line of trees or in a small valley.

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 may be separated and all components are packed into the retrieve vehicle.

Competition

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.

A balloonist prepares to drop a marker on a competition target, in this case the centre of a road intersection.

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. One of the most common causes of serious ballooning accidents in the US is power line strikes.^[1] 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.

Of the 11 accidents involving fatalities recorded by the NTSB between 1997 and 2007, 4 involved contact with power lines, 3 involved falling after hanging onto the outside of a rising balloon, 3 involved striking an object on landing (boulder, wall, or tree), and 1 involved an equipment failure (an eyebolt).^[2]

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.

Night flight

Hot air balloons at night

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.

Winter flight

The ability to fly hot air balloons in the winter is limited mostly by the ability of the participants to withstand the cold. The balloons themselves fly well in cold air. Because the temperature difference between inside and outside the balloon, not the absolute inside temperature, determines the lift it develops, a much lower internal temperature is sufficient to fly in cold weather.

However, if the liquid propane in the fuel tanks is too cold (0°C/32°F or less) it does not generate sufficient vapor pressure to adequately feed the burner(s). This can be overcome by charging the fuel tanks with inert gas such as nitrogen^[3] or by warming them, with electric heat tapes for example, and insulating them against the cold.^[4]

Tethering

Sometimes, especially at balloon festivals or other special events, balloons will be flown while still tied to the ground by ropes, referred to as tethers. This enables the pilot to provide shorts rides to many passengers instead of drifting with the wind away from the event with just one load of passengers. There are a variety of tethering techniques, depending on the balloon manufacturers instructions and current wind conditions. Tethers can be attached to the basket, burner support, the top of the envelope, or any combination thereof. Even though tethered, a registered aircraft is considered to be flying as soon as it leaves the ground, and is subject to all the appropriate rules and regulations.

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 as it is designed to make a different sound when operating so as not to startle livestock) on the burner creating a spectacular bright orange flame instead of the main valve which creates the more typical (and efficient) blue flame.

Events

Main article: Hot air balloon festivals

There are many regular gatherings of balloons and balloonists around the world. Most of these events are held on an 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. One such event is the Albuquerque International Balloon Fiesta.

Traditions

Over the long history of ballooning, several traditions have developed.

Champagne

A common tradition among balloonists is to have a champagne toast upon landing. Legend has it that early French aeronauts carried champagne to appease angry or frightened spectators at the landing site.^[5] A champagne toast is now often included in commercial sight-seeing flights.

Toast

Along with the champagne, a popular toast among balloonists is: "soft winds and gentle landings."

Prayer

The toast may also consist of or be accompanied by the Balloonist's Prayer: "The winds have welcomed you with softness, The sun has blessed you with his warm hands, You have flown so high and so free, That God has joined you in laughter, And set you gently again, Into the loving arms of mother earth.".^[6]

In popular culture

In song

The song Blown By The Wind from the 1996 Alan Parsons release On Air captures the languid and ethereal spirit of flight without navigation.

Up, Up and Away is the debut album by American pop group The Fifth Dimension, released in 1967 (see 1967 in music). The title track, by Jimmy Webb was released as a single and became a major pop hit, reaching #7 on the Billboard chart.

In cinema

In The Wizard of Oz (1939), the wizard leaves the Emerald City in a hot air balloon.

In Around the World in Eighty Days (1956 film) a hot air balloon (featured on the movie poster) is used to cross the Pyrenees.

In Enduring Love (2004), a hot air balloon is involved in a tragic accident during the opening scene.

In literature

In Something Wicked This Way Comes (1962) by Ray Bradbury, a hot air balloon with the Dust Witch, is sent to find out and mark the location of the boys' homes.

In Phillip Pullman's trilogy His Dark Materials, which includes the novel Northern Lights (1995) which has been made into the film The Golden Compass (2007), characters use both balloons and zeppelins for transport. Background information about ballooning is frequently inserted into the story.

In television

On Dora the Explorer Benny the Bull, and often rides in a hot air balloon.

On Sir Arthur Conan Doyle's The Lost World, disaster strikes and their hot air balloon crashes in the uncharted Amazon jungle.

In V The Final Battle, humans defeated the alien visitors by dropping red dust from hot air balloons.

In advertising

RE/MAX balloon in flight.

RE/MAX, an international real estate company, uses a hot air balloon with their name on it as their main logo. They also sponsor a fleet of hot air balloons that make frequent appearances at hot air balloon festivals and other events.

In video games

In Donkey Kong Country 2: Diddy's Kong Quest players ride in a hot air balloon over Crocodile Cauldron.

In Chao (Sonic the Hedgehog), a Hero Chao and a Dark Chao float in front of the characters in a hot air balloon.

See also

• Hot air balloon
• Hot air balloon festivals
• List of balloon uses
• Montgolfier brothers

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	FLIGHT: A Virgin hot air balloon flying over Cambridge	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

References

• The Science and Art of Hot Air Ballooning by Jackson and Diehtl, Garland Publishing Inc, 1977
• How to Fly a Balloon by Stockwell and Kalakuka, Balloon Publishing Company, 1999
• Balloon Ground School Home Study Manual by Stockwell, and Kalakuka, and Grady, Balloon Publishing Company, 1997

External links

Organizations

Wikimedia Commons has media related to:

Hot air balloon

• FAI International Balloon Committee
• Balloon Federation of America
• International Aeronauts League
• Connecticut Lighter Than Air Society (CLAS)

General ballooning sites

• Hot Air Balloon Simulator - learn the dynamics of a hot air balloon on the Internet based simulator.
• AdventuresAloft.com Balloon Ride Directory
• Hot Air Ballooning - How balloons fly, list of balloon clubs, free classified ads for balloonists
• Hot Air Balloon Web Links
• E-Hot-Air-Ballooning Website
• Balloonsworld.com - Balloonsite and community for pilots world wide
• Make your own solar balloons, get them pre-built - all about solar-powered hot air balloons

History

• Possible prehistoric Nazca hot air balloon
• Balloon History - More information about the history of hot air balloons

Misc

• Balloon quotations
• High-resolution hot air balloon photos
• Balloon photo database