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Big Sky Theory
In aviation, the Big Sky Theory is that two randomly flying bodies are very unlikely to collide, as the three-dimensional space is so large relative to the bodies. Some aviation safety rules involving altimetry and navigation standards are based on this concept. It does not apply when aircraft are flying along specific narrow routes, such as an airport traffic pattern or jet airway. The Big Sky Theory has been mathematically modeled, using a gas law approach.Knecht, W.R. (2001)Modeling the Big Sky Theory Proceedings of the Human Factors and Ergonomics Society 45th annual meeting, 87-91, Santa Monica, CA: Human Factors and Ergonomics Society. This implies that collisions of aircraft in free flight should be extremely rare in en-route airspace, whereas operational errors such as violations of formal separation standards should be relatively common. Three critical parameters are the number of flying objects per unit volume, their speed, and their size. Larger, faster objects, flying ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aviation
Aviation includes the activities surrounding mechanical flight and the aircraft industry. ''Aircraft'' includes fixed-wing and rotary-wing types, morphable wings, wing-less lifting bodies, as well as lighter-than-air craft such as hot air balloons and airships. Aviation began in the 18th century with the development of the hot air balloon, an apparatus capable of atmospheric displacement through buoyancy. Some of the most significant advancements in aviation technology came with the controlled gliding flying of Otto Lilienthal in 1896; then a large step in significance came with the construction of the first powered airplane by the Wright brothers in the early 1900s. Since that time, aviation has been technologically revolutionized by the introduction of the jet which permitted a major form of transport throughout the world. Etymology The word ''aviation'' was coined by the French writer and former naval officer Gabriel La Landelle in 1863. He derived the term from the v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fuselage
The fuselage (; from the French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds crew, passengers, or cargo. In single-engine aircraft, it will usually contain an engine as well, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage, which in turn is used as a floating hull. The fuselage also serves to position the control and stabilization surfaces in specific relationships to lifting surfaces, which is required for aircraft stability and maneuverability. Types of structures Truss structure This type of structure is still in use in many lightweight aircraft using welded steel tube trusses. A box truss fuselage structure can also be built out of wood—often covered with plywood. Simple box structures may be rounded by the addition of supported lightweight stringers, allowing the fabric covering to form a more aerodynamic shape, or one more pleasing to the eye. Geodesic construction Geo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kessler Syndrome
The Kessler syndrome (also called the Kessler effect, collisional cascading, or ablation cascade), proposed by NASA scientist Donald J. Kessler in 1978, is a scenario in which the density of objects in low Earth orbit (LEO) due to space pollution is high enough that collisions between objects could cause a cascade in which each collision generates space debris that increases the likelihood of further collisions. In 2009 Kessler wrote that modeling results had concluded that the debris environment was already unstable, "such that any attempt to achieve a growth-free small debris environment by eliminating sources of past debris will likely fail because fragments from future collisions will be generated faster than atmospheric drag will remove them". One implication is that the distribution of debris in orbit could render space activities and the use of satellites in specific orbital ranges difficult for many generations. History NORAD, Gabbard and Kessler Willy Ley predict ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Almaz
The Almaz (russian: Алмаз, lit=Diamond) program was a highly secret Soviet military space station program, begun in the early 1960s. Three crewed military reconnaissance stations were launched between 1973 and 1976: Salyut 2, Salyut 3 and Salyut 5. To cover the military nature of the program the three launched Almaz stations were designated as civilian Salyut space stations. Salyut 2 failed shortly after achieving orbit, but Salyut 3 and Salyut 5 both conducted successful crewed testing. Following Salyut 5, the Soviet Ministry of Defense judged in 1978 that the time and resources consumed by station maintenance outweighed the benefits relative to automatic reconnaissance satellites. The space stations' cores were known internally as OPS (russian: ОПС, GRAU index 11F71 and 11F71B), from "Orbital Piloted Station" (russian: Орбитальная Пилотируемая Станция). As part of the Almaz program, the Soviets developed several spacecraft for support ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Projectiles
A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance. Although any objects in motion through space are projectiles, they are commonly found in warfare and sports (for example, a thrown baseball, kicked football, fired bullet, shot arrow, stone released from catapult). In ballistics mathematical equations of motion are used to analyze projectile trajectories through launch, flight, and impact. Motive force Blowguns and pneumatic rifles use compressed gases, while most other guns and cannons utilize expanding gases liberated by sudden chemical reactions by propellants like smokeless powder. Light-gas guns use a combination of these mechanisms. Railguns utilize electromagnetic fields to provide a constant acceleration along the entire length of the device, greatly increasing the muzzle velocity. Some projectiles provide propulsion during flight by means of a rocket engine or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kinetic Energy
In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body when decelerating from its current speed to a state of rest. Formally, a kinetic energy is any term in a system's Lagrangian which includes a derivative with respect to time. In classical mechanics, the kinetic energy of a non-rotating object of mass ''m'' traveling at a speed ''v'' is \fracmv^2. In relativistic mechanics, this is a good approximation only when ''v'' is much less than the speed of light. The standard unit of kinetic energy is the joule, while the English unit of kinetic energy is the foot-pound. History and etymology The adjective ''kinetic'' has its roots in the Greek word κίνησις ''kinesis'', m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Subtended Angle
In geometry, an angle is subtended by an arc, line segment or any other section of a curve when its two rays pass through the endpoints of that arc, line segment or curve section. Conversely, the arc, line segment or curve section confined within the rays of an angle is regarded as the corresponding subtension of that angle. We also sometimes say that an arc is intercepted or enclosed by that angle. The precise meaning varies with context. For example, one may speak of the angle subtended by an arc of a circle when the angle's vertex is the centre of the circle. See also * Central angle * Inscribed angle External links Definition of subtended angle mathisfun.com, with interactive applet In computing, an applet is any small application that performs one specific task that runs within the scope of a dedicated widget engine or a larger program, often as a plug-in. The term is frequently used to refer to a Java applet, a program w ... How an object subtends an angle '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Space Warfare
Space warfare is hypothetical combat in which one or more belligerents are situated in outer space. The scope of space warfare therefore includes ''ground-to-space warfare'', such as attacking satellites from the Earth; ''space-to-space warfare'', such as satellites attacking satellites; and ''space-to-ground warfare'', such as satellites attacking Earth-based targets. Space warfare in fiction is thus sub-genre and theme of science fiction, where it is portrayed with a range of realism and plausibility. , no actual warfare is known to have taken place in space, though a number of tests and demonstrations have been performed. International treaties are in place that attempt to regulate conflicts in space and limit the installation of space weapon systems, especially nuclear weapons. From 1985 to 2002 there was a United States Space Command, which in 2002 merged with the United States Strategic Command, leaving the United States Space Force (formerly Air Force Space Comma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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-dimensional space.. That given point is the centre (geometry), centre of the sphere, and is the sphere's radius. The earliest known mentions of spheres appear in the work of the Greek mathematics, ancient Greek mathematicians. The sphere is a fundamental object in many fields of mathematics. Spheres and nearly-spherical shapes also appear in nature and industry. Bubble (physics), Bubbles such as soap bubbles take a spherical shape in equilibrium. spherical Earth, The Earth is often approximated as a sphere in geography, and the celestial sphere is an important concept in astronomy. Manufactured items including pressure vessels and most curved mirrors and lenses are based on spheres. Spheres rolling, roll smoothly in any direction, so mos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Degree (angle)
A degree (in full, a degree of arc, arc degree, or arcdegree), usually denoted by ° (the degree symbol), is a measurement of a plane (mathematics), plane angle in which one Turn (geometry), full rotation is 360 degrees. It is not an SI unit—the SI unit of angular measure is the radian—but it is mentioned in the SI Brochure, SI brochure as an Non-SI units mentioned in the SI, accepted unit. Because a full rotation equals 2 radians, one degree is equivalent to radians. History The original motivation for choosing the degree as a unit of rotations and angles is unknown. One theory states that it is related to the fact that 360 is approximately the number of days in a year. Ancient astronomers noticed that the sun, which follows through the ecliptic path over the course of the year, seems to advance in its path by approximately one degree each day. Some ancient calendars, such as the Iranian calendar, Persian calendar and the Babylonian calendar, used 360 days for a year. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slant Range
In radio electronics, especially radar terminology, slant range or slant distance is the distance along the relative direction between two points. If the two points are at the same level (relative to a specific datum), the slant distance equals the horizontal distance. An example of slant range is the distance to an aircraft flying at high altitude with respect to that of the radar antenna. The slant range (1) is the hypotenuse of the triangle represented by the altitude of the aircraft and the distance between the radar antenna and the aircraft's ground track (point (3) on the earth directly below the aircraft). In the absence of altitude information, for example from a height finder, the aircraft location would be plotted farther (2) from the antenna than its actual ground track. See also *Ranging *Spherical range The great-circle distance, orthodromic distance, or spherical distance is the distance along a great circle. It is the shortest distance between two points o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anti-aircraft Warfare
Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes Surface-to-air missile, surface based, subsurface (Submarine#Armament, submarine launched), and air-based weapon systems, associated sensor systems, command and control arrangements, and passive measures (e.g. barrage balloons). It may be used to protect naval, ground, and air forces in any location. However, for most countries, the main effort has tended to be homeland defence. NATO refers to airborne air defence as counter-air and naval air defence as anti-aircraft warfare. Missile defense, Missile defence is an extension of air defence, as are initiatives to adapt air defence to the task of intercepting any projectile in flight. In some countries, such as Britain and Germany during the World War II, Second World War, the Soviet Union, and modern NATO a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
