All about Hot Air Balloon

Hot air balloon is a sort of aircraft. It is lifted byhot air inside the balloon. There is a light busket is hangingunder the balloon to carry passengers. The heated air inside theballoon makes it afloat since it has a lower density than the cold air outside the balloon.

The passengers and the pilot standin the basket, which is attached to the balloon by ropes. The basket isusually made of wicker.

History

The hot air balloon is the oldest form of flying technology that can successfully carry people. At an early age in ancient China, hot air uses to make objects fly. Paper lanterns were sent into the air for signaling.

The Montgolfier brothers were the first prepared Hot air balloon to carry a person. On 19 September 1783, they demonstrated their invention for King Louis XVI and Queen Marie Antoinette at the French court in Paris. The passengers were a sheep, a duck and a rooster. They flew for 480 meters. The first flight carrying a person was on 15 October 1783. It carried Jacques-Etienne Montgolfier. The balloon was attached to the ground by a rope. The first free flight, without being attached to the ground, was a few weeks later, on 21 November 1783. It carried Marquis François d’Arlandes and Pilatre de Rozier.

Today

Modern hot air balloons, with an onboard heat source, were developed by Ed Yost, beginning during the 1950s; his first successful flight was 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.

Record

Presently, hot air balloons are used primarily for recreation. Hot air balloons are able to fly to extremely high altitudes. On November 26, 2005 VijaypatSinghania set the world altitude record for highest hot air balloon flight, reaching 21,027 m (68,986 ft). He took off from downtown Mumbai, India, and landed 240 km (150 mi) south in Panchale. The previous record of 19,811 m (64,997 ft) had been set by Per Lindstrand on June 6, 1988, in Plano, Texas.

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 7,671.91 km (4,767.10 mi) from Japan to Northern Canada. With a volume of 74 thousand 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 245 mph (394 km/h). 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 300 miles (480 km) south of Cairo. The two men exceeded distance, endurance, and time records, traveling 19 days, 21 hours, and 55 minutes. Steve Fossett, flying solo, exceeded the record for briefest time traveling around the world on 3 July 2002 on his sixth attempt in 320 h 33 min. FedorKonyukhov 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 272h 11m, as of 17 September 2016 awaiting official confirmation as the new record.

Hot Air Balloon First in Bangladesh

On December 28, 2011, the new chapter in the balloon flying history of Bangladesh is added. The first hot air balloon flying exhibition was held in the afternoon on the south side of the Bangabandhu National Stadium. State Minister for Youth and Sports Ahad Ali inaugurated the flying exhibition. At that time the country’s first balloon pilot was Mr. ShahjahanMridhaBenu general secretary of the Bangladesh Kite Federation.

The balloon has been named ‘Joy Bangla’ after the war of liberation. This is the name of the balloon request for registration in Civil Aviation.

Different Types of Balloons

There are many different types of balloons. They come in many shapes and sizes depending on their intended purpose – transport, play, Monitoring or even medicine. Here are some of them:

Hot air balloon is an oldest type of flying machine. It has an envelope that holds heated air and, most often, a gondola or a wicker basket underneath it which carries passengers. Hot air is lighter than cold which lifts the balloon.

Gas balloon is filled with a gas that is lighter than air – helium or hydrogen. Different balloons can be gas balloons, and this type has a lot of subtypes.

Cluster balloons are clusters of helium-inflated rubber balloons which also can have gondola or a harness that carries a pilot. Cluster balloons are controlled in flight by jettisoning or deflating balloons or by jettisoning the ballast.

Hopper balloon (or just Hopper) is a small, one-person hot air balloon, very similar to standard hot air balloons but with one seat or a harness. Because of their size, their flights last only 1 to 1.5 hours.

Airship or dirigible is a type of a lighter-than-air steerable balloon that uses engines to move through the air. They can have rigid, semi-rigid and non-rigid bodies.

Solar balloon is a balloon, usually made out of material that is light and black or dark balloon material, that gains buoyancy when the air inside is heated by the sun’s radiation.

Fire balloon was a type of balloon used by Japan during World War II. It was a hydrogen balloon which carried bombs.

Research balloons are balloons that are used in scientific research. They carry instruments that do meteorological, atmospheric, astronomic, and military research and are usually unmanned. Some of them were even used on other planets (Vega 1 and Vega 2 on Venus in 1984).

Barrage balloon, or a blimp, is a non-rigid balloon tethered with metal cables, used to defend against aircraft attacks making the approach of airplanes more difficult.

Observation balloon were usually hot air balloons or blimps with a gondola that were used for intelligence gathering and artillery spotting.

Ceiling balloon is a type of meteorological balloon that is used to determine the height of the base of clouds above ground level. They are filled with gas, and its ascent rate is known, so the height of clouds is determined according to the time the balloon needs until it reaches the cloud.

Rozière balloon

A rozière is balloon used for the records of distance by its large autonomy, it is constituted by two compartments, which using the functioning of the gas balloon and the hot-air balloon.

A compartment seals containing a lighter gas than air, generally helium, and an open compartment containing of the air that we warm with a burner which works generally with propane. The gas balloon assures the floatability and the hot air part modifies the altitude by controlling the temperature.

Some balloons are used as decoys during the war. They are shaped like tanks or some other real item of military equipment, and its purpose is to deceive the enemy.

Types of Scientific Balloons

Scientific balloons can lift up to 8000 lbs. (3600 kg), which is approximately the weight of three small cars!

NASA’s Balloon Program Office uses multiple types of balloons to lift scientific payloads into the atmosphere. The Balloon Program Office supports numerous space and Earth science research missions, and different balloons may be more beneficial to different payloads. The two types of balloons currently used by the NASA Balloon Flight program are zero-pressure and super-pressure. Though either balloon can be used for any flight type, zero-pressure balloons typically are used for short flights, whereas a super pressure balloon is required for an extended flight. The design of a zero-pressure balloon does not allow for extended flights except during the summer in the Polar Regions. Various balloon sizes with corresponding capabilities are available.

Zero-Pressure Balloons

These balloons are open at the bottom and have open ducts hanging from the sides to allow gas to escape and to prevent the pressure inside the balloon from building up during gas expansion as the balloon rises above Earth’s surface. The duration of this type of balloon is limited because of gas loss, mostly due to the day/night cycling of the balloon.

Super-Pressure Balloons (ULDB – Pumpkin)

These ultra-long distance balloons, or ULDBs, are completely sealed with no open ducts. Gas cannot escape the balloon and pressure builds up as the gas expands. Because gas loss is minimized in this balloon, super-pressure balloons can fly for longer durations than zero-pressure balloons. Because of their shape, they are called the Pumpkin. More about Super-Pressure Balloons

Both types of balloons are made of thin plastic film, called polyethylene. The thickness is similar to that of plastic sandwich wrap. The most common size of NASA’s balloons is 40 million cubic feet, or a volume equivalent to more than 195 Goodyear blimps (a Goodyear Blimp measures 202,700 ft). When fully inflated, a football stadium could fit inside the balloon. Technicians inflate the balloons using helium gas. The balloons then float at altitudes around 120,000 feet, or more than twice as high as commercial airplanes.

“You can fit 195 Goodyear Blimps inside the largest Standard NASA Zero-Pressure Balloon!”

A balloon in free-flight may encounter significant operational restrictions across a range of projected mission types.

These restrictions may include:

       (a) need to avoid high population centers for safety reasons for long duration missions;

       (b) need to avoid regions restricted for geopolitical reasons;

       (c) desired over flight of a specific region;

       (d) desire to recover payload in acceptable areas; and,

       (e) desire to enable new science, particularly for Earth Science.

NASA’s Balloon Operational Support Capability chart.

Credits: NASA/BPO

Planetary Ballooning

The Balloon Program in collaboration with other NASA centers and private industry continued to investigate the feasibility of balloon missions on other planets and space bodies. Current NASA missions of interest are targeted for Mars, Venus and Titan. Balloons will enable in-situ measurements at different altitudes that are currently not feasible with other platforms such as satellites and rovers.

A conceptual planetary balloon mission to Mars.

Credits: NASA/Wallops BPO

Hot Air Balloon 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 1 ft (0.30m) 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 600 cubic meter (21,000 cu ft) of envelope volume; for a perfect sphere the radius would be around 5 m (16ft). 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 17,000 cubic meter (600,000 cu ft).The most-used size is about 2,800 cubic meter (99,000 cu ft), and can 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.

An older, and presently less commonly used, style of top 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. Another common type of top design is the “Smart Vent,” which, rather than lowering a fabric disc into the envelope as in the “parachute” type, gathers the fabric together in the center of the opening. This system can theoretically be used for in-flight maneuvering, but is more commonly used only as a rapid-deflation device for use after landing, of particular value in high winds. Other designs, such as the “pop top” and “MultiVent” systems, have also attempted to address the need for rapid deflation on landing, but the parachute top remains popular as an all-around maneuvering and deflation system.

Shape

Besides special shapes, possibly for marketing purposes, there are several variations on the traditional “inverted tear drop” shape. The simplest, often used by home builders, is a hemisphere on top of a truncated cone. More-sophisticated designs attempt to minimize the circumferential stress on the fabric, with different degrees of success depending on whether they take fabric weight and varying air density into account. This shape may be referred to as “natural”.Finally, some specialized balloons are designed to minimize aerodynamic drag (in the vertical direction) to improve flight performance in competitions.

Basket

Baskets are commonly made of woven wicker or rattan. These materials have proven to be sufficiently light, strong, and durable for balloon flight. Such baskets are usually rectangular or triangular in shape. They vary in size from just big enough for two people to large enough to carry thirty.Larger baskets often have internal partitions for structural bracing and to compartmentalize the passengers. Small holes may be woven into the side of the basket to act as foot holds for passengers climbing in or out.

Baskets may also be made of aluminium, especially a collapsible aluminium frame with a fabric skin, to reduce weight or increase portability.These may be used by pilots without a ground crew or who are attempting to set altitude, duration, or distance records. Other specialty baskets include the fully enclosed gondolas used for around-the-world attemptsand baskets that consist of little more than a seat for the pilot and perhaps one passenger.

Burner

The burner unit gasifies liquid propanemixes it with air, ignites the mixture, and directs the flame and exhaust into the mouth of the envelope. Burners vary in power output; each will generally produce 2 to 3 MW of heat (7 to 10 million BTUs per hour), with double, triple, or quadruple burner configurations installed where more power is needed.The pilot actuates a burner by opening a propane valve, known as 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.

Where more than one burner is present, the pilot can use one or more at a time depending on the desired heat output. Each burner is characterized by a metal coil of propane tubing the flame shoots through to preheat the incoming liquid propane. The burner unit may be suspended from the mouth of the envelope, or supported rigidly 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. 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.

Fuel tanks

Propane fuel tanks are usually cylindrical pressure vessels made from aluminium, 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 (liters).They may be intended for upright or horizontal use, and may be mounted inside or outside the basket.

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. Tanks may be preheated with electrical heat tapes to produce sufficient vapor pressure for cold weather flying.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 known as a variometer, 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.

 

The Manufacturing Process

Envelope

1. Envelope construction basically involves the sewing of the gores together. Whether done by hand or industrial sewing machine, there are three stitches. The double lap seam features two rows of parallel stitching along the folded over fabric seam. Preferred by manufacturers for its strength and lightness, the seam features about eight stitches in every inch (3 per cm). A few manufactures use a flat seam (straight parallel stitching holds two pieces of fabric together) and the zigzag (zigzag parallel stitching with a double lap of fabric). The load tapes and cords are also sewn in.
2. After the envelope is stitched, it is coated. The coating is applied mechanically and under pressure.
3. Finally, if the envelope is to be used for advertising purposes, an applique is attached with a slogan or name. It can be applied with acrylic spray paint, or ready-made adhesive letters or banners can be attached. If the artwork is large, it can be sewn into the envelope proper by being cut directly into the gores. This can be a complex, demanding process.

Basket

4. Baskets are manufactured base-first. On top of the plywood base with runners, a frame of cane is built up to 1 in (2.5 cm) in diameter. At the corner, the frame surrounds stainless steel wires and load frames. Around the frame, the rattan or willow is woven. Holes are left in the body of the basket for cylinder straps. The finished basket is coated with varnish to help maintain its shape and set the cane together. Finally, the edges are protected with sewn in rawhide, leather, or suede. The instrument/dashboard is built in as are the propane tanks for the burner unit.

Burner

5. Many balloon manufacturers outsource these components and assemble them between the basket and the envelope after the other parts are put together.

Combined mass

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

Using a density of 0.9486 kg/m³ for dry air heated to 210 °F (99 °C).

Generating lift

Increasing the air temperature inside the envelope makes it less dense 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 greater than this maximum operating temperature — about 230 °C (450 °F) — but higher temperatures cause the strength of the nylon fabric to degrade more quickly 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 less than the maximum to extend envelope fabric life.

The lift generated by 100,000 ft³ (2831.7 m³) of dry air heated to various temperatures may be calculated as follows:

The density of air at 20 °C, 68 °F is about 1.2 kg/m³. The total lift for a balloon of 100,000 ft³ heated to (99 °C, 210 °F) would be 1595 lb, 723.5 kg. This is just enough to generate neutral buoyancy for the total system mass (not including the heated air trapped in the envelope, of course) stated in the previous section. Liftoff would require a slightly greater temperature, depending on the desired rate of climb. In reality, the air contained in the envelope is not all the same temperature, as the accompanying thermal image shows, and so these calculations are based on averages.

For typical atmospheric conditions (20 °C, 68 °F), a hot air balloon heated to (99 °C, 210 °F) requires about 3.91 m³ of envelope volume to lift 1 kilogram (62.5 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 air surrounding. On a warm day, a balloon cannot lift as much as on a cool day, because the temperature required for launch will exceed the maximum sustainable for nylon envelope fabric. Also, 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.

Safety equipment

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

I’m Safe Checklist

In the basket

To relight the burner if 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.

A fire extinguisher suitable for extinguishing propane fires is a useful piece of safety equipment in a balloon. Most balloons carry a 1 kg AB:E type fire extinguisher.

A handling or drop line is mandatory safety equipment in many countries. It is a rope or webbing of 20 – 30 meters in length attached to the balloon basket with a quick release connection at one end. In very calm wind conditions the balloon pilot can throw the handling line from the balloon so that the ground crew can safely guide the balloon away from obstructions on the ground.

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. In addition, 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. Finally, 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.

Manufacturers

The largest manufacturer of hot air balloons in the world is Cameron Balloons Company of Bristol, England, which also owns Lindstrand Balloons of Oswestry, England. Cameron Balloons, Lindstrand Balloons and another English balloon manufacturing company, Thunder and Colt (since acquired by Cameron), have been 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 do not contribute to the balloon’s ability to stay aloft.

The second largest manufacturer of hot air balloons in the world is Ultramagic Company, based in Spain, which produces from 80 to 120 balloons per year. Ultramagic can produce very large balloons, such as the N-500 that accommodates as many as 27 persons in the basket, and has also produced many balloons with special shapes, as well as cold-air inflatables.

In the USA Aerostar International, Inc. of Sioux Falls, South Dakota was North America’s largest balloon manufacturer and a close second in world manufacturing before ceasing to build balloons in January 2007. The oldest U.S. certified manufacture is now Adams Balloons out of Albuquerque, New Mexico. Firefly Balloons, formerly The Balloon Works, is a manufacturer of hot-air balloons in Statesville, North Carolina. Another manufacturer is Head Balloons, Inc. of Helen, Georgia.

The major manufacturers in Canada are Sundance Balloons and Fantasy Sky Promotions. Other manufacturers include Kavanagh Balloons of Australia, Schroeder Fire Balloons of Germany, and Kubicek Balloons of the Czech Republic.

Hot air ballooning

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 direction of the winds, 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.

Flight techniques

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

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

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. Some balloons, AX7 and larger, may have two (or more) crown lines.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 winds 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 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. Unless the pilot intervenes, 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 equilibrium only momentarily. The rest of the time it is either too warm or too cool and so either climbing or descending.

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

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.

Sometimes, a chase vehicle may be equipped with a trailer, which can provide a lot more room at the cost of being more difficult to maneuver. 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 lift-gate to aid in loading heavy equipment into the cargo space (the envelope itself can weigh 250lbs or more).

Communication between the balloon and chase vehicle can be accomplished by two-way radio, or even shouting, when they are close enough together. The use of cell phones for this purpose, while the balloon is flying, may violate local telecommunication laws and should therefore be avoided except in an emergency situation.

Landing

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 (2.2 m/s) 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 competitionsare 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 point 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 the 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, when winds at altitude flow in the opposite direction of surface 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.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).

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 or 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 or by warming them, with electric heat tapes for example, and insulating them against the cold.

Tethering

Sometimes, especially at balloon festivals or other special events, balloons are flown while tied to the ground with ropes (tethers). This enables quick rides to many passengers, instead of long rides drifting with the wind away from the event with one load of passengers. Tethering techniques depend on the balloon manufacturer’s instructions and wind conditions. Tethers can be attached to the basket, burner support, or the top of the envelope. A “night glow” is a tethered flight in darkness to enhance visual effects. While typical day flights use the main valve, using an efficient blue flame, at night, tethered pilots use the liquid valve “whisper burner” (“cow burner”, as it does not startle livestock), creating a spectacular bright orange flame.

Though tethered, a balloon is considered a registered flying aircraft when it leaves the ground.

Events

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. Two such events are the Albuquerque International Balloon Fiesta and the Bristol Balloon Fiesta.

Toast

Along with the champagne, a popular toast among balloonists is:

“soft winds and gentle landings.”

Many balloonists recite the Balloonist’s Blessing (Anon, known as ‘The Balloonists Prayer’) with the champagne toast:

The winds have welcomed you with softness

The sun has blessed you with its warm hands

You have flown so high and so well

That God has joined you in your laughter

and set you gently back into the loving arms of mother earth.

 

Thank you

Collected and edited by-Kazi Md. Abdullah

References:

1. Apex Balloons : https://www.apexballoons.com/balloons/
2. বাংলাদেশে প্রথম হট এয়ার বেলুন উড্ডয়ন প্রদর্শনী : http://www.somewhereinblog.net/blog/Bigganbarta007/29511926
3. বিজ্ঞানব্লগ : http://bigganblog.org
4. Virgin Balloon Flight : https://www.virginballoonflights.co.uk/
5. Hot Air Balloon, Wikipedia : https://en.wikipedia.org/wiki/Hot_air_balloon
6. Hot Air Ballooning, Wikipedia : https://en.wikipedia.org/wiki/Hot_air_ballooning
7. Get Involved in Ballooning : http://www.hotairballooning.com/
8. 2017 Balloon Festivals in the USA : townandtourist.com/festivals-events/hot-air-balloon-festivals/
9. NASA’s Super Pressure Balloon Takes Flight From New Zealand : https://www.nasa.gov/feature/wallops/2017/nasas-super-pressure-balloon-takes-flight-from-new-zealand
10. Balloon Fiesta Exhibit Highlights NASA Aeronautics : https://www.nasa.gov/topics/aeronautics/features/balloon_fiesta.html