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A tethered balloon is a balloon that is restrained by a cable attached to the ground or a vehicle and so cannot float freely. The tether is attached to a winch which is used to raise and lower the balloon. To give it buoyancy and enable it to float, a tethered balloon would once have been filled with hydrogen gas but nowadays helium gas is used because it is not flammable.
Tethered balloons typically take one of three forms:
- An elongated (airship- or blimp-shaped) balloon with fins at one end to stabilise it so that it always points into the wind.
- A simple round balloon, without stabilisation.
- A hybrid tethered balloon uses buoyancy, and also aerodynamic lift similar to a kite.
Tethered hydrogen balloons
Designed by Albert Caquot, French engineer, in 1914, the barrage balloons of World War I and World War II were examples of tethered balloons. Today, tethered balloons are used for lifting cameras, radio antennas, electro-optical sensors, radio-relay equipment and advertising banners - often for long durations. Tethered balloons are also used for position marking and bird control work.
Tethered helium balloons
A tethered balloon was made in France at Chantilly Castle in 1994 by Aerophile SA and following the installation of a balloon in Paris in 1999 the company has installed more than 60 tethered balloons in 25 countries. Aerophile SA is also the largest operator of tethered balloons in the world with six operations, Paris, Disneyland Paris in France and Orange County Great Park (CA), Walt Disney World (FL), Wonderworks Pigeon Forge (TN) and San Diego Zoo Safari Park (CA) in the US.
During the 1990 Invasion of Kuwait, the first indication of the Iraqi ground advance was from a radar-equipped tethered balloon that detected Iraqi armor and air assets moving south. Surveillance tethered balloons were used in the 2004 American occupation of Iraq. They utilized a high-tech optics system to detect and observe enemies from miles away. They have been used to over watch foot patrols and convoys in Baghdad, Afghanistan and several other contingency operations.
The United States Geological Survey uses tethered balloons to carry equipment to places where conventional aircraft cannot go, such as above an erupting volcano. Tethered balloons are ideal as they can easily remain more or less in one place; are less likely to be damaged by volcanic ash and are less expensive to operate than a helicopter.
The Drug Enforcement Administration has contracted with Lockheed Martin to operate a series of radar-equipped tethered balloons to detect low-flying aircraft attempting to enter the United States. A total of twelve tethered balloons, called Tethered Aerostat Radar System, are positioned approximately 350 miles apart, from California to Florida to Puerto Rico, providing unbroken radar coverage along the entire southern border of the US.
Tethered balloons can be used as temporary transmitters, instead of a radio mast, either by using the tether which holds the balloon as the antenna, or by carrying antennas on the balloon fed by a fiber optic or radio frequency cable contained inside the tether. The advantage of tethered balloons is that great antenna heights are easily realizable and they can stay aloft for months.
Tethered balloons are sometimes used for advertisement, either by lifting advertisement signs, or by using a balloon with advertisements on it. Often both methods are combined. It is not uncommon to use specially designed balloons. By suspending a light source within the envelope, the balloon can be made to glow at night, drawing attention to its message.
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List of manufacturers
- Lockheed Martin PTDS Aerostat ISR system
- Vigilance Rapid Deployable Aerostat
- Raven Aerostar
- SkyDoc Aerostat resources
- Worldwide Aeros Corp
- Top I Vision
- Aerophile SA
- Aerostat based communications and surveillance
- SkyDoc Aerostat resources
- Air-Foil Aerostat
- "GAO-13-81, DEFENSE ACQUISITIONS: Future Aerostat and Airship Investment Decisions Drive Oversight and Coordination Needs" (PDF). Retrieved 2013-06-15.
- "Persian Gulf States - Kuwait - Regional and National Security Considerations". Countrystudies.us. Retrieved 2013-06-15.
- "Tethered Aerostat Radar System - United States Nuclear Forces". Fas.org. Retrieved 2013-06-15.