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Atmospheric Satellite
Atmospheric satellite (United States usage, abbreviated atmosat) or pseudo-satellite (British usage) is a marketing term for an aircraft that operates in the atmosphere at high altitudes for extended periods of time, in order to provide services conventionally provided by an artificial satellite orbiting in space. Atmospheric satellites remain aloft through atmospheric lift, either aerostatic/buoyancy (e.g., balloons) or aerodynamic (e.g., airplanes). By contrast, conventional satellites in Earth orbit operate in the vacuum of space and remain in flight through centrifugal force derived from their orbital speed. To date, all atmosats have been unmanned aerial vehicles (UAVs). Design principles An atmosat remains aloft through atmospheric lift, in contrast to a satellite in Earth orbit which moves freely at high speed in the vacuum of space, and orbits due to its centrifugal force matching the force of gravity. Satellites are expensive to build and launch, and any changes t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Stations And Systems ITU
Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves, and received by another antenna connected to a radio receiver. Radio is very widely used in modern technology, in radio communication, radar, radio navigation, remote control, remote sensing, and other applications. In radio communication, used in radio and television broadcasting, cell phones, two-way radios, wireless networking, and satellite communication, among numerous other uses, radio waves are used to carry information across space from a transmitter to a receiver, by modulating the radio signal (impressing an information signal on the radio wave by varying some aspect of the wave) in the transmitter. In radar, used to locate and track objects like aircraft, ships, spacecraft and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Airships
An airship or dirigible balloon is a type of aerostat or lighter-than-air aircraft that can navigate through the air Powered aircraft, under its own power. Aerostats gain their lift from a lifting gas that is less dense than the surrounding air. In early dirigibles, the lifting gas used was hydrogen gas, hydrogen, due to its high lifting capacity and ready availability. Helium gas has almost the same lifting capacity and is not flammable, unlike hydrogen, but is rare and relatively expensive. Significant amounts were first discovered in the United States and for a while helium was only available for airships in that country. Most airships built since the 1960s have used helium, though some have used hot air.A few airships after World War II used hydrogen. The first British airship to use helium was the Chitty Bang Bang (airship), ''Chitty Bang Bang'' of 1967. The envelope of an airship may form the gasbag, or it may contain a number of gas-filled cells. An airship also has ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
