A tethered, moored or captive balloon is a

balloon A balloon is a flexible bag that can be inflated with a gas, such as helium, hydrogen, nitrous oxide, oxygen, and air. For special tasks, balloons can be filled with smoke, liquid water, granular media (e.g. sand, flour or rice), or light so ...

that is restrained by one or more tethers attached to the ground and so it cannot float freely. The base of the tether is wound around the drum of a

winch A winch is a mechanical device that is used to pull in (wind up) or let out (wind out) or otherwise adjust the tension of a rope or wire rope (also called "cable" or "wire cable"). In its simplest form, it consists of a spool (or drum) attache ...

, which may be fixed or mounted on a vehicle, and is used to raise and lower the balloon. A balloon is a form of

aerostat An aerostat (, via French) is a lighter-than-air aircraft that gains its lift through the use of a buoyant gas. Aerostats include unpowered balloons and powered airships. A balloon may be free-flying or tethered. The average density of the cra ...

, along with the powered free-flying

airship An airship or dirigible balloon is a type of aerostat or lighter-than-air aircraft that can navigate through the air under its own power. Aerostats gain their lift from a lifting gas that is less dense than the surrounding air. In early ...

, although the American GAO has used the term "aerostat" to describe a tethered balloon in contrast to the powered airship. Tethered balloons have been used for advertising, recreation,

observation Observation is the active acquisition of information from a primary source. In living beings, observation employs the senses. In science, observation can also involve the perception and recording of data via the use of scientific instruments. The ...

, and civil or military uses.

Design principles

Early balloons were simple round

sphere A sphere () is a Geometry, geometrical object that is a solid geometry, three-dimensional analogue to a two-dimensional circle. A sphere is the Locus (mathematics), set of points that are all at the same distance from a given point in three ...

s, with a payload hung beneath. The round shape uses the minimum material to accommodate a given volume of lifting gas, making it the lightest construction. However, in any significant wind the round shape is aerodynamically unstable and will bob about, risking damage or the balloon breaking free. To avoid this problem, the

kite balloon A kite balloon is a tethered balloon which is shaped to help make it stable in low and moderate winds and to increase its lift. It typically comprises a streamlined envelope with stabilising features and a harness or yoke connecting it to the mai ...

was developed. This form has an elongated shape to reduce wind resistance and some form of tail surface to stabilize it so that it always points into the wind. Like the powered airship, such balloons are often called blimps. A hybrid tethered balloon or

kytoon A kytoon or kite balloon is a tethered aircraft which obtains some of its lift dynamically as a heavier-than-air kite and the rest aerostatically as a lighter-than-air balloon. The word is a portmanteau of kite and balloon. The primary advantage ...

is shaped to provide aerodynamic lift similar to a

kite A kite is a tethered heavier than air flight, heavier-than-air or lighter-than-air craft with wing surfaces that react against the air to create Lift (force), lift and Drag (physics), drag forces. A kite consists of wings, tethers and anchors. ...

, as well as to reduce drag.

History

The Royal Flying Corps on the Western Front, 1914-1918 Q12029

barrage balloon A barrage balloon is a large uncrewed tethered balloon used to defend ground targets against aircraft attack, by raising aloft steel cables which pose a severe collision risk to aircraft, making the attacker's approach more difficult. Early barra ...

s of

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

and

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

were early examples of tethered balloons. Military

observation balloon An observation balloon is a type of balloon that is employed as an aerial platform for intelligence gathering and artillery spotting. Use of observation balloons began during the French Revolutionary Wars, reaching their zenith during World War ...

s were also used extensively in World War I. These early types used

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

as their lifting gas. Tethered balloons are used for lifting

camera A camera is an Optics, optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), ...

s, 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. Typically, they use non-flammable

helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...

gas to provide lift.

Modern use

Advertising

Tethered balloons are often used for

advertising Advertising is the practice and techniques employed to bring attention to a product or service. Advertising aims to put a product or service in the spotlight in hopes of drawing it attention from consumers. It is typically used to promote a ...

, either by lifting advertisement signs, or by using a balloon with advertisements written on, or attached to it. Often both methods are combined. It is not uncommon to use specially designed balloons.

Blimp A blimp, or non-rigid airship, is an airship (dirigible) without an internal structural framework or a keel. Unlike semi-rigid and rigid airships (e.g. Zeppelins), blimps rely on the pressure of the lifting gas (usually helium, rather than hydr ...

-shaped balloons are especially popular for advertising use. By suspending a light source within the envelope, the balloon can be illuminated at night, drawing attention to its message.

Earth sciences

The

United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...

uses tethered balloons to carry equipment to places where conventional aircraft cannot go, such as above an erupting

volcano A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are ...

. 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 A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...

Leisure

Tethered balloons are frequently used as a recreational attraction.

Telecommunications

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 attainable and they are significantly cheaper than erecting a temporary mast. This allows for more localized coverage with a high capacity within a radius of the balloon at an altitude between above ground level. Tethered balloons or blimps have been studied to overcome the limitations of terrestrial

cell towers A cell site, cell tower, or cellular base station is a cellular-enabled mobile device site where antennas and electronic communications equipment are placed (typically on a radio mast, tower, or other raised structure) to create a cell, or adjac ...

for telecommunications. Because of their higher elevation they can provide a larger coverage area and better line of sight, would be more economical and would have better latency than satellite systems.

Security and defense

During the 1990

Invasion of Kuwait The Iraqi invasion of Kuwait was an operation conducted by Iraq on 2 August 1990, whereby it invaded the neighboring State of Kuwait, consequently resulting in a seven-month-long Iraqi military occupation of the country. The invasion and Ira ...

, the first indication of the Iraqi ground advance was from a

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, w ...

-equipped tethered balloon that detected Iraqi armor and air assets moving south. Tethered surveillance balloons were used in the 2004 American occupation of Iraq. They utilized a high-tech

optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviole ...

system to detect and observe enemies from miles away. They have been used to over watch foot patrols and convoys in

Baghdad Baghdad (; ar, بَغْدَاد , ) is the capital of Iraq and the second-largest city in the Arab world after Cairo. It is located on the Tigris near the ruins of the ancient city of Babylon and the Sassanid Persian capital of Ctesiphon ...

Afghanistan Afghanistan, officially the Islamic Emirate of Afghanistan,; prs, امارت اسلامی افغانستان is a landlocked country located at the crossroads of Central Asia and South Asia. Referred to as the Heart of Asia, it is bordere ...

, and are permanently installed above US military bases in

Kabul Kabul (; ps, , ; , ) is the capital and largest city of Afghanistan. Located in the eastern half of the country, it is also a municipality, forming part of the Kabul Province; it is administratively divided into 22 municipal districts. Acco ...

and

Bagram Bagram (; Pashto/ fa, بگرام) is a town and seat in Bagram District in Parwan Province of Afghanistan, about 60 kilometers north of the capital Kabul. It is the site of an ancient city located at the junction of the Ghorband and Panjshir Va ...

. The US

Drug Enforcement Administration The Drug Enforcement Administration (DEA; ) is a Federal law enforcement in the United States, United States federal law enforcement agency under the U.S. Department of Justice tasked with combating drug trafficking and distribution within th ...

has contracted with

Lockheed Martin The Lockheed Martin Corporation is an American aerospace, arms, defense, information security, and technology corporation with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It ...

to operate a series of

-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 The Tethered Aerostat Radar System (TARS) is an American low-level airborne ground surveillance system that uses aerostats (moored balloons) as radar platforms. Similar systems include the EL/M-2083 and JLENS. System The aerostats are large fa ...

, are positioned approximately apart, from

California California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...

Puerto Rico Puerto Rico (; abbreviated PR; tnq, Boriken, ''Borinquen''), officially the Commonwealth of Puerto Rico ( es, link=yes, Estado Libre Asociado de Puerto Rico, lit=Free Associated State of Puerto Rico), is a Caribbean island and Unincorporated ...

, providing unbroken radar coverage along the entire southern border of the US. The U.S. Army has developed a tethered

to perform operational testing at

Aberdeen Proving Ground Aberdeen Proving Ground (APG) (sometimes erroneously called Aberdeen Proving ''Grounds'') is a U.S. Army facility located adjacent to Aberdeen, Harford County, Maryland, United States. More than 7,500 civilians and 5,000 military personnel work at ...

beginning in 2015. The system, called

JLENS The Joint Land Attack Cruise Missile Defense Elevated Netted Sensor System, or JLENS (colloquially, Spy Balloon), was a tethered aerial detection system designed to track boats, ground vehicles, cruise missiles, manned and unmanned aircraft (air ...

, uses two moored balloons designed to provide over-the-horizon missile defense capability.

References

{{Authority control Aircraft configurations Balloons (aeronautics)