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Scimitar Antenna
A scimitar antenna is a radio antenna so named because its shape resembles a talon-shaped curved sword of the same name. It was invented in 1958 by Edwin M. and William P. Turner. It is essentially a flat metal plate in a semi-circular or semi-elliptical shape with a wide end at one side and a narrow point at the other. Its shape makes it suited for use on aircraft or space vehicles. It was used for VHF communication on the Apollo command and service module. A U.S. patent was applied for on October 31, 1958, and granted on December 26, 1961. The inventors assigned the patent to the U.S. government, as represented by the Secretary of the Air Force. Use in Apollo Program The Block II Apollo command and service module carried a pair of elliptical VHF scimitar antennas on the Service Module walls. The antenna's scimitar shape wasn't externally visible, since it had to be covered by a shroud for aerodynamic purposes. The antenna radiated and received signals in an approxima ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Antenna
In radio engineering, an antenna or aerial is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. In transmission, a radio transmitter supplies an electric current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). In reception, an antenna intercepts some of the power of a radio wave in order to produce an electric current at its terminals, that is applied to a receiver to be amplified. Antennas are essential components of all radio equipment. An antenna is an array of conductors ( elements), electrically connected to the receiver or transmitter. Antennas can be designed to transmit and receive radio waves in all horizontal directions equally (omnidirectional antennas), or preferentially in a particular direction ( directional, or high-gain, or “beam” antennas). An antenna may include components not connec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apollo 5
Apollo 5 (launched January 22, 1968), also known as AS-204, was the uncrewed first flight of the Apollo Lunar Module (LM) that would later carry astronauts to the surface of the Moon. The Saturn IB rocket bearing the LM lifted off from Cape Kennedy on January 22, 1968. The mission was successful, though due to programming problems an alternate mission to that originally planned was executed. Like Apollo 4, this flight was long delayed, due in part to setbacks in development of the LM, manufactured by Grumman Aircraft. The original Saturn IB rocket that was to take the first LM (LM-1) to space was taken down during the delays and replaced with the one that would have launched Apollo 1 if the spacecraft fire that killed three astronauts had not taken place. LM-1 arrived at the Kennedy Space Center in June 1967; the following months were occupied in testing and placing the LM atop the Saturn IB. After final delays due to equipment trouble, the countdown began on Jan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antennas (radio)
In radio engineering, an antenna or aerial is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. In transmission, a radio transmitter supplies an electric current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). In reception, an antenna intercepts some of the power of a radio wave in order to produce an electric current at its terminals, that is applied to a receiver to be amplified. Antennas are essential components of all radio equipment. An antenna is an array of conductors ( elements), electrically connected to the receiver or transmitter. Antennas can be designed to transmit and receive radio waves in all horizontal directions equally (omnidirectional antennas), or preferentially in a particular direction ( directional, or high-gain, or “beam” antennas). An antenna may include components not connect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PTFE
Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. It is one of the best-known and widely applied PFAS. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a spin-off from DuPont, which originally discovered the compound in 1938. Polytetrafluoroethylene is a fluorocarbon solid, as it is a high- molecular-weight polymer consisting wholly of carbon and fluorine. PTFE is hydrophobic: neither water nor water-containing substances wet PTFE, as fluorocarbons exhibit only small London dispersion forces due to the low electric polarizability of fluorine. PTFE has one of the lowest coefficients of friction of any solid. Polytetrafluoroethylene is used as a non-stick coating for pans and other cookware. It is non-reactive, partly because of the strength of carbon–fluorine bonds, so it is often used in containers and pipework for reactive and corrosive chemicals. Where used as a lubric ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DynCorp
DynCorp (), formally DynCorp International, was an American private military contractor. Started as an aviation company, the company also provided flight operations support, training and mentoring, international development, intelligence training and support, contingency operations, security, and operations and maintenance of land vehicles. DynCorp received more than 96% of its more than $3 billion in annual revenue from the U.S. federal government. The corporate headquarters were in an unincorporated part of Fairfax County near Falls Church, Virginia, while the company's contracts were managed from its office at Alliance Airport in Fort Worth, Texas. DynCorp provided services for the U.S. military in several theaters, including Bolivia, Bosnia, Somalia, Angola, Haiti, Colombia, Kosovo and Kuwait. It also provided much of the security for Afghan president Hamid Karzai's presidential guard and trained much of the police forces of Iraq and Afghanistan. DynCorp was also hired to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interceptor Aircraft
An interceptor aircraft, or simply interceptor, is a type of fighter aircraft designed specifically for the defensive interception role against an attacking enemy aircraft, particularly bombers and reconnaissance aircraft. Aircraft that are capable of being or are employed as both ‘standard’ air superiority fighters and as interceptors are sometimes known as fighter-interceptors. There are two general classes of interceptor: light fighters, designed for high performance over short range; and heavy fighters, which are intended to operate over longer ranges, in contested airspace and adverse meteorological conditions. While the second type was exemplified historically by specialized night fighter and all-weather interceptor designs, the integration of mid-air refueling, satellite navigation, on-board radar and beyond visual range (BVR) missile systems since the 1960s has allowed most frontline fighter designs to fill the roles once reserved for specialised night/all-we ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Jamming
Radio jamming is the deliberate jamming, blocking or interference with wireless communications.https://apps.fcc.gov/edocs_public/attachmatch/DA-12-347A1.pdf Enforcement Advisory No. 2012-02 FCC Enforcement Advisory Cell Jammers, GPS Jammers, and Other Jamming Devices Consumer Alert: Using or Importing Jammers is Illegal In some cases, jammers work by the transmission of radio signals that disrupt communications by decreasing the signal-to-noise ratio. The concept can be used in wireless data networks to disrupt information flow. It is a common form of censorship in totalitarian countries, in order to prevent foreign radio stations in border areas from reaching the country. Jamming is usually distinguished from interference that can occur due to device malfunctions or other accidental circumstances. Devices that simply cause interference are regulated differently. Unintentional "jamming" occurs when an operator transmits on a busy frequency without first checking whether it is i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apollo 9
Apollo 9 (March 313, 1969) was the third human spaceflight in NASA's Apollo program. Flown in low Earth orbit, it was the second crewed Apollo mission that the United States launched via a Saturn V rocket, and was the first flight of the full Apollo spacecraft: the command and service module (CSM) with the Lunar Module (LM). The mission was flown to qualify the LM for lunar orbit operations in preparation for the first Moon landing by demonstrating its descent and ascent propulsion systems, showing that its crew could fly it independently, then rendezvous and dock with the CSM again, as would be required for the first crewed lunar landing. Other objectives of the flight included firing the LM descent engine to propel the spacecraft stack as a backup mode (as would be required on the Apollo 13 mission), and use of the portable life support system backpack outside the LM cabin. The three-man crew consisted of Commander James McDivitt, Command Module Pilot David Scott, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gumdrop Meets Spider - GPN-2000-001100
Gumdrops are a type of gummy candy. They are brightly colored pectin-based pieces, shaped like a narrow dome (sometimes with a flattened top), often coated in granulated sugar and having fruit and spice flavors; the latter are also known as spice drops. History Gumdrops first appeared in the 19th century United States, purportedly as early as 1801, although at that time they likely referred to small, hard sweets also derived from fruit gelatin. The name "gumdrop" is not found in print until 1859, appearing in an advertisement published by the Decatur, IL ''Illinois State Chronicle'' for a candy shop owned by a George Julier. By that time, a gelatin-based, rubbery candy akin to modern gummies went by the ''gumdrop'' name, but also a pastier candy with a potato starch base. One of the oldest types of gumdrops still produced are "spice" gumdrops, using traditional spices including clove, anise, allspice, spearmint, cinnamon, and wintergreen for flavoring. Usage Gumdrops, spi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Claw
A claw is a curved, pointed appendage found at the end of a toe or finger in most amniotes (mammals, reptiles, birds). Some invertebrates such as beetles and spiders have somewhat similar fine, hooked structures at the end of the leg or tarsus for gripping a surface as they walk. The pincers of crabs, lobsters and scorpions, more formally known as their chelae, are sometimes called claws. A true claw is made of a hard protein called keratin. Claws are used to catch and hold prey in carnivorous mammals such as cats and dogs, but may also be used for such purposes as digging, climbing trees, self-defense and grooming, in those and other species. Similar appendages that are flat and do not come to a sharp point are called nails instead. Claw-like projections that do not form at the end of digits but spring from other parts of the foot are properly named spurs. Tetrapods In tetrapods, claws are made of keratin and consist of two layers. The unguis is the harder external lay ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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