Hot Air Balloons

History

The hot air balloon is the oldest successful human-carrying flight technology and is a subset of balloon aircraft.
On Nov 21, 1783, in Paris, France, the first untethered manned flight was made by Jean-François Pilâtre de Rozier and François Laurent d'Arlandes in a hot air balloon created on Dec 14, 1782 by the Montgolfier brothers. Recently, balloon envelopes have been made in all kinds of shapes, such as hot dogs, rocket ships, and the shapes of commercial products. Hot air balloons that can be propelled through the air rather than just being pushed along by the wind are known as airships or, more specifically, thermal airships.
A hot air balloon consists of a bag called the envelope that is capable of containing heated air. Suspended beneath is a gondola or wicker basket (in some long-distance or high-altitude balloons, a capsule), which carries passengers and (usually) a source of heat, in most cases an open flame. The heated air inside the envelope makes it buoyant since it has a lower density than the relatively cold air outside the envelope. As with all aircraft, hot air balloons cannot fly beyond the atmosphere. Unlike gas balloons, the envelope does not have to be sealed at the bottom since the air near the bottom of the envelope is at the same pressure as the surrounding air. In today's sport balloons the envelope is generally made from nylon fabric and the mouth of the balloon (closest to the burner flame) is made from fire resistant material such as Nomex.

Origins:

Unmanned hot air balloons are popular in Chinese history. Zhuge Liang of the Shu Han kingdom, in the Three Kingdoms era (220–80 AD) used airborne lanterns for military signaling. These lanterns are known as Kongming lanterns. There is also some speculation, from a demonstration led by British modern hot air balloonist Julian Nott in the late 1970s and again in 2003, that hot air balloons could have been used by people of the Nazca culture of Peru some 1500 to 2000 years ago, as a tool for designing the famous Nazca ground figures and lines. The first documented balloon flight in Europe was demonstrated by Bartolomeu de Gusmão. On August 8, 1709, in Lisbon, he managed to lift a balloon full of hot air about 4.5 meters in front of King John V and the Portuguese court.

First Use:

The first clearly recorded instance of a balloon carrying passengers used hot air to generate buoyancy and was built by the brothers Joseph-Michel and Jacques-Etienne Montgolfier in Annonay, France. After experimenting with unmanned balloons and flights with animals, the first tethered balloon flight with humans on board took place on October 15, 1783. It is fitting that Etienne Montgolfier was the first human to lift off the earth, making at least one tethered flight from the yard of the Reveillon workshop in the Faubourg Saint-Antoine. It was most likely on October 15th, 1783. A little while later on that same day, Pilatre de Rozier became the second to ascend into the air, to an altitude of 80 feet, which was the length of the tether. The first free flight with human passengers took place on November 21, 1783. King Louis XVI had originally decreed that condemned criminals would be the first pilots, but de Rozier, along with Marquis François d'Arlandes, successfully petitioned for the honor. The first military use of a hot air balloon happened during the battle of Fleurus where the French used the balloon l'Entreprenant as an observation post.

Modern hot air balloons, with an onboard heat source, were pioneered by Ed Yost, beginning in the 1950s; his work resulted in his first successful flight, on October 22, 1960. The first modern-day hot air balloon to be built in the United Kingdom was the Bristol Belle in 1967. Today, hot air balloons are used primarily for recreation.
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 21,027 meters (68,986 feet). He took off from downtown Bombay, India, and landed 240 kilometers (149 miles) 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. As with all unpressurized aircraft, oxygen is needed for all crew and passengers on any flight that exceeds an altitude of about 15,000 ft (4,572 m).
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 highest 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 (482 kilometers) south of Cairo. The two men broke distance, endurance, and time records, traveling 19 days, 21 hours, and 55 minutes. Steve Fosset broke the record for shortest time around the world on 3 July 2002. The new record is 320 h 33 min.

Construction

A hot air balloon for manned flight uses a single-layered, fabric gas bag (lifting "envelope"), with an opening at the bottom called the mouth or throat. Attached to the envelope is a basket, or gondola, for carrying the passengers. Mounted above the basket and centered in the mouth is the "burner," which injects a flame into the envelope, heating the air within. The heater or burner is fueled by propane, a liquefied gas stored in pressure vessels, similar to high pressure forklift cylinders.


Envelope

Modern hot air balloons are usually made of light-weight and strong synthetic fabrics such as ripstop nylon, or dacron (a polyester).
A hot air balloon is partially inflated with cold air from a gas-powered fan, before the propane burners are used for final inflation.
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 run from the throat to the crown (top) of the envelope, are called 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 (0.3 m) in diameter that vertical load tapes attach to.


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 used as a 'rag bag': cold inflated and opened for children to run through. Products for recoating the fabric are becoming commercially available.


Sizes

A range of envelope sizes is available. The smallest, one-person, basket-less balloons (called "Hoppers" or "Cloudhoppers") have as little as 21,000 ft³ (595 m³) of envelope volume[29] (for a perfect sphere this would mean a radius of around 5.22 m (17 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 600,000 ft³ (16,990 m³). However, most balloons are roughly 100,000 ft³ (2,832 m³) and carry 3 to 5 people.


Vents


The parachute vent at the top of an envelope, as seen from below through the mouth
The top of the balloon usually has a vent of some sort. This enables 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.[31] 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 completely open to collapse the balloon after landing.
An older, and today 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.


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

A wicker basket capable of holding 16 passengers
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 attempts,[37] and baskets that consist of little more than a seat for the pilot and perhaps one passenger.


Burner

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. 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, 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.
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 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. 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.


Stainless steel fuel tanks, wrapped in red insulating covers, mounted vertically, and with fuel gauges, during refueling
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.
[edit]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. A GPS receiver can be useful to indicate ground speed (traditional aircraft air speed indicators would be useless) and direction.


Generating lift


Thermal image showing temperature variation in a hot air balloon
Raising the air temperature inside the envelope makes it lighter than the surrounding (ambient) air. The balloon floats because of the buoyant force exerted on it. This force is the same force that acts on objects when they are in water and is described by Archimedes' principle. The amount of lift (or buoyancy) provided by a hot air balloon depends primarily upon the difference between the temperature of the air inside the envelope and the temperature of the air outside the envelope. For most envelopes made of nylon fabric, the maximum internal temperature is limited to approximately 120 °C (250 °F).
It should be noted that the melting point of nylon is significantly higher than this maximum operating temperature — about 230 °C (450 °F). However the lower temperatures are generally used because the higher the temperature, the more quickly the strength of the nylon fabric degrades over time. With a maximum operating temperature of 120 °C (250 °F), balloon envelopes can generally be flown for between 400 and 500 hours before the fabric needs to be replaced. Many balloon pilots operate their envelopes at temperatures significantly below the maximum 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:

air temperature air density air mass lift generated
68 °F, 20 °C 1.2041 kg/m³ 7517 lbs, 3409.7 kg 0 lbs, 0 kg
210 °F, 99 °C 0.9486 kg/m³ 5922 lbs, 2686.2 kg 1595 lbs, 723.5 kg
250 °F, 120 °C 0.8978 kg/m³ 5606 lbs, 2542.4 kg 1912 lbs, 867.3 kg

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 higher 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 surrounding air. 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.

Montgolfiere


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

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

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




Hot Air Balloon Festivals

Hot air balloon festivals are held annually in many places throughout the year, allowing hot air balloons to gather and participate in various activities. They can include races; evening "night glows", in which balloons are fired while remaining tetheted to the ground; and rides.




Facts



- Hot air balloons were discovered in France in 1783.
- It was discovered that a fabric bag filled with hot air would rise.
- Initially Balloons without any Passengers were sent up.
- Then, animals of all sorts were used for experimenting like a sheep, rooster, and duck, to be sent high up.
- Finally, they sent up a balloon with two men in it. It traveled over Paris for 5.5 miles. It stayed up 23 minutes.
- This was the first attempt made by man to fly. Bravo!
- Balloons have been important in science as they have helped us study the weather and the atmosphere.
- Hot Air Balloon has a Special basket for passengers to sit in it.
- It has flying wires to attach the basket to the balloon.
- The skirt helps direct the hot air into the balloon.
- Each long section of the Hot Air Balloon is called the gore.
- Smaller pieces of the gore are called panels.
- A Parachute is placed right at the top of each Hot Air Balloon.

- Balloon pilots need a commercial pilot's license (fixed-wing). They must have at least 35 hours of flight instruction, attend ground school for basic aviation training, pass a written test for hot-air balloons and have a flight check from a Federal Aviation Administration official.
- According to the FAA, balloons must meet air-traffic control requirements if they are in a controlled air-space, and pilots must have radio contact with controllers.
- There are no official safety requirements for passengers, but passengers should know with whom they're flying and their qualifications.
- Accidents are rare, especially in the Northwest. The only serious injuries for the area -- found in a check of National Transportation Safety Board balloon accident reports back to 1984 -- were a broken leg and a broken ankle, both from rough landings.
- Hot air balloons don't fly in the rain because balloon heat can cause water to boil atop the balloon, and boiling water destroys the fabric.
- Area balloon operators can carry from two to 10 passengers at a time, depending on balloon size.
- Children under 5 usually aren't allowed.
- Ballooning is not a silent sport. There are some quiet moments, but those burners are noisy.
- Balloonists dress like hikers: Pants, sturdy flat shoes and layers of shirt, sweater, jacket, for example. Carry cameras and lots of film.