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Identification Studies Of UFOs
Identifying unidentified flying objects (UFOs) is a difficult task due to the normally poor quality of the evidence provided by those who report sighting the unknown object. Observations and subsequent reporting are often made by those untrained in astronomy, atmospheric phenomena, aeronautics, physics, and perception. Nevertheless, most officially investigated UFO sightings, such as from the U.S. Air Force's Project Blue Book, have been identified as being due to honest misidentifications of natural phenomena, aircraft, or other prosaic explanations. In early U.S. Air Force attempts to explain UFO sightings, unexplained sightings routinely numbered over one in five reports. However, in early 1953, right after the CIA's Robertson Panel, percentages of unexplained sightings dropped precipitously, usually being only a few percent in any given year. When Project Blue Book closed down in 1970, only 6% of all cases were classified as being truly unidentified. UFOs that can be explaine ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unidentified Flying Object
An unidentified flying object (UFO) is an object or phenomenon seen in the sky but not yet identified or explained. The term was coined when United States Air Force (USAF) investigations into flying saucers found too broad a range of shapes reported to consider them all saucers or discs. UFOs are also known as unidentified aerial phenomena or unidentified anomalous phenomena (UAP). Upon investigation, most UFOs are Identification studies of UFOs, identified as known objects or atmospheric phenomena, while a small number remain unexplained. While unusual sightings in the sky have been reported since at least the 3rd century BC, UFOs became culturally prominent after World War II, escalating during the Space Age. Studies and investigations into UFO reports conducted by governments (such as Project Blue Book in the United States and Project Condign in the United Kingdom of Great Britain and Ireland, United Kingdom), as well as by organisations and individuals have occurred over ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CUFOS
The Center for UFO Studies (CUFOS) is a privately funded UFO research group. The group was founded in 1973 by J. Allen Hynek, who at the time was chair of the Department of Astronomy at Northwestern University in Illinois.Franch John, The Secret Life of J. Allen Hynek'. Skeptical Inquirer Volume 37.1, January/February 2013Archivedfrom the original on November 22, 2020. History Hynek was a scientific consultant for Project Blue Book, the United States Air Force official study of the UFO phenomenon from 1948 to 1969. Although Hynek started out as a skeptic and helped the Air Force to debunk most UFO reports, he gradually became convinced that a small number of UFO cases were not hoaxes or explainable as misidentifications of natural phenomena, and that these cases might represent something extraordinary—even alien visitation from other planets. When the Air Force shut down Project Blue Book in 1969, Hynek, in 1973, founded the Center for UFO Studies (CUFOS) to continue to collec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerodynamic
Aerodynamics () is the study of the motion of atmosphere of Earth, air, particularly when affected by a solid object, such as an airplane wing. It involves topics covered in the field of fluid dynamics and its subfield of gas dynamics, and is an important domain of study in aeronautics. The term ''aerodynamics'' is often used synonymously with gas dynamics, the difference being that "gas dynamics" applies to the study of the motion of all gases, and is not limited to air. The formal study of aerodynamics began in the modern sense in the eighteenth century, although observations of fundamental concepts such as aerodynamic drag were recorded much earlier. Most of the early efforts in aerodynamics were directed toward achieving Aircraft#Heavier-than-air – aerodynes, heavier-than-air flight, which was first demonstrated by Otto Lilienthal in 1891. Since then, the use of aerodynamics through mathematical analysis, empirical approximations, wind tunnel experimentation, and computer si ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ramjet
A ramjet is a form of airbreathing jet engine that requires forward motion of the engine to provide air for combustion. Ramjets work most efficiently at supersonic speeds around and can operate up to . Ramjets can be particularly appropriate in uses requiring a compact mechanism for high-speed, such as missiles. Weapons designers are investigating ramjet technology for use in artillery shells to increase range; a 120 mm ramjet-assisted mortar shell is thought to be able to travel . They have been used, though not efficiently, as tip jets on the ends of helicopter rotors. History France Cyrano de Bergerac ''L'Autre Monde: ou les États et Empires de la Lune ( Comical History of the States and Empires of the Moon)'' (1657) was the first of three satirical novels written by Cyrano de Bergerac that are considered among the first science fiction stories. Arthur C Clarke credited this book with conceiving the ramjet, and as the first fictional example of rocket-powered ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rocket
A rocket (from , and so named for its shape) is a vehicle that uses jet propulsion to accelerate without using any surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely from propellant carried within the vehicle; therefore a rocket can fly in the vacuum of space. Rockets work more efficiently in a vacuum and incur a loss of thrust due to the opposing pressure of the atmosphere. Multistage rockets are capable of attaining escape velocity from Earth and therefore can achieve unlimited maximum altitude. Compared with airbreathing engines, rockets are lightweight and powerful and capable of generating large accelerations. To control their flight, rockets rely on momentum, airfoils, auxiliary reaction engines, gimballed thrust, momentum wheels, deflection of the exhaust stream, propellant flow, spin, or gravity. Rockets for military and recreational uses date back to at least 13th-century China. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Propfan
A propfan, also called an open rotor engine, open fan engine is an aircraft engine combining features of turbofans and turboprops. It uses advanced, curved propeller blades without a ducted fan, duct. Propfans aim to combine the speed capability of turbofans with the fuel efficiency of turboprops, especially at high subsonic speeds. It is sometimes called a "ultra-high-bypass (UHB) turbofan". Definition In the 1970s, Hamilton Standard described its propfan as "a small diameter, highly loaded multiple bladed variable pitch propulsor having swept blades with thin advanced airfoil sections, integrated with a nacelle contoured to retard the airflow through the blades thereby reducing compressibility losses and designed to operate with a turbine engine and using a single stage reduction gear resulting in high performance". In 1982, the weekly aviation magazine Flight International defined the propfan as a propeller with 8–10 highly swept blades that cruised at a speed of , a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thrust
Thrust is a reaction force described quantitatively by Newton's third law. When a system expels or accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude but opposite direction to be applied to that system. The force applied on a surface in a direction perpendicular or normal to the surface is also called thrust. Force, and thus thrust, is measured using the International System of Units (SI) in newtons (symbol: N), and represents the amount needed to accelerate 1 kilogram of mass at the rate of 1 meter per second per second. In mechanical engineering, force orthogonal to the main load (such as in parallel helical gears) is referred to as static thrust. Examples A fixed-wing aircraft propulsion system generates forward thrust when air is pushed in the direction opposite to flight. This can be done by different means such as the spinning blades of a propeller, the propelling jet of a jet engine, or by ejecting hot gases f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerostatics
A subfield of fluid statics, aerostatics is the study of gases that are not in motion with respect to the coordinate system in which they are considered. The corresponding study of gases in motion is called aerodynamics. Aerostatics studies density allocation, especially in air. One of the applications of this is the barometric formula. An aerostat is a lighter than air craft, such as an airship or balloon, which uses the principles of aerostatics to float. Basic laws Treatment of the equations of gaseous behaviour at rest is generally taken, as in hydrostatics, to begin with a consideration of the general equations of momentum for fluid flow, which can be expressed as: \rho + U_i = - - + \rho g_j , where \rho is the mass density of the fluid, U_j is the instantaneous velocity, P is fluid pressure, g are the external body forces acting on the fluid, and \tau_ is the momentum transport coefficient. As the fluid's static nature mandates that U_j = 0 , and that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnus Effect
The Magnus effect is a phenomenon that occurs when a spin (geometry), spinning Object (physics), object is moving through a fluid. A lift (force), lift force acts on the spinning object and its path may be deflected in a manner not present when it is not spinning. The strength and direction of the Magnus force is dependent on the speed and direction of the rotation of the object. The Magnus effect is named after Heinrich Gustav Magnus, the German physicist who investigated it. The force on a rotating cylinder is an example of Kutta–Joukowski theorem, Kutta–Joukowski lift, named after Martin Kutta and Nikolay Zhukovsky (scientist), Nikolay Zhukovsky (or Joukowski), mathematicians who contributed to the knowledge of how lift is generated in a fluid flow. Description The most readily observable case of the Magnus effect is when a spinning sphere (or cylinder) curves away from the arc it would follow if it were not spinning. It is often used by football (soccer) and volleybal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
VTOL
A vertical take-off and landing (VTOL) aircraft is one that can takeoff and landing, take off and land vertically without relying on a runway. This classification can include a variety of types of aircraft including helicopters as well as thrust-vectoring fixed-wing aircraft and other hybrid aircraft with powered helicopter rotor, rotors such as cyclogyro, cyclogyros/cyclocopters and gyrodynes. Some VTOL aircraft can operate in other modes as well, such as CTOL (conventional take-off & landing), STOL (short take-off & landing), or STOVL (short take-off & vertical landing). Others, such as some helicopters, can only operate as VTOL, due to the aircraft lacking landing gear that can handle taxiing. VTOL is a subset of V/STOL (vertical or short take-off & landing). Some aerostat, lighter-than-air aircraft also qualify as VTOL aircraft, as they can hover, takeoff and land with vertical approach/departure profiles. Electric vertical takeoff and landing aircraft, or eVTOLs, are being ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Propeller
A propeller (often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working fluid such as water or air. Propellers are used to pump fluid through a pipe or duct, or to create thrust to propel a boat through water or an aircraft through air. The blades are shaped so that their rotational motion through the fluid causes a pressure difference between the two surfaces of the blade by Bernoulli's principle which exerts force on the fluid. Most marine propellers are screw propellers with helical blades rotating on a propeller shaft (ship), propeller shaft with an approximately horizontal axis. History Early developments The principle employed in using a screw propeller is derived from stern sculling. In sculling, a single blade is moved through an arc, from side to side taking care to keep presenting the blade to the wat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
