Aerostat
From Free net encyclopedia
The term "aerostat" has two meanings. In the first, broader sense, it includes all lighter than air aircraft.
The term "aerostat" comes from the fact that buoyancy is technically said to provide aerostatic lift in that the force upwards arises without movement through the surrounding air mass. This contrasts with aerodynamic lift which requires the movement of at least some part of the aircraft through the surrounding air mass.
The second, narrower and more techical usage refers only to moored balloons. This article focuses on the narrower use of the term. For a discussion of the other types of buoyant aircraft, see balloon (aircraft), airship, and lighter than air.
Thus, in the narrower sense, an aerostat is a tethered or moored balloon often shaped like an airship and usually filled with helium. Aerostats differ from airships and balloons in that airships and balloons are both free flying whereas aerostats are tied to the ground.
The barrage balloons of World War I and World War II were examples of aerostats. Today, Aerostats are used primarily as long duration sensor platforms.
Surveillance aerostats have also been used in the 2004 American occupation of Iraq. Utilizing a high-tech optics system to detect and observe enemies from miles away and have been used accompanying foot patrols in Baghdad.
The USGS uses aerostats to carry equipment to places where conventional aircraft cannot go, such as above an erupting volcano. Aerostats 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.
Aerostats in science fiction
Aerostats are commonly used in science fiction, though they are often envisioned as having a vacuum based displacement rather than helium; doing such appears to require the construction of a very large craft or the use of super-strong rigid materials. Aerostats of fiction are typically not tied to the ground, but rather remain stationary through the use of propulsion systems and internal sensors and controls.
es:Aerostato fr:Aérostat it:Aerostato pt:aeróstato ru:Аэростат