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Variable-buoyancy Propulsion
In engineering, variable-buoyancy propulsion is the use of a buoyancy engine to provide propulsion for a vehicle. The concept was first explored in the 1960s for use with underwater gliders, but has since been applied to autonomous aircraft as well. Principle Variable-buoyancy propulsion is based on the ability of a vehicle to change its buoyancy from negative to positive and vice versa (for aircraft, this means alternating between being heavier and lighter than air). While positively buoyant, the vehicle trims bow up and uses its hydrofoils or wings to glide forward while rising, using buoyancy as the driving force. At the top of the climb, buoyancy is made negative and the vehicle trims bow down and glides forward while descending, using gravity as the driving force. The process can be repeated for as long as the buoyancy engine A buoyancy engine is a device that alters the buoyancy of a vehicle or object in order to either move it vertically, as in the case of underwater pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Buoyancy Engine
A buoyancy engine is a device that alters the buoyancy of a vehicle or object in order to either move it vertically, as in the case of underwater profiling floats and stealth buoys, or provide forward motion (therefore providing variable-buoyancy propulsion) such as with underwater gliders and some autonomous aircraft. For underwater applications, buoyancy engines typically involve a hydraulic pump that either inflates and deflates an external bladder filled with hydraulic fluid, or extends and retracts a rigid plunger. The change in the vehicle's total volume alters its buoyancy, making it float upwards or sink as required. Alternative systems employing gas obtained from water electrolysis, rather than hydraulic fluid, have also been proposed. as have systems which pump ambient water into and out of a pressure vessel Operation The buoyancy engine is a fairly new piece of technology currently in research by many institutions and organizations that utilize underwater surveil ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Propulsion
Propulsion is the generation of force by any combination of pushing or pulling to modify the translational motion of an object, which is typically a rigid body (or an articulated rigid body) but may also concern a fluid. The term is derived from two Latin words: ''wikt:pro, pro'', meaning'' before'' or ''forward''; and ''wikt:pellere, pellere'', meaning ''to drive''. A propulsion system consists of a source of mechanical power, and a ''propulsor'' (means of converting this power into propulsive force). Plucking a guitar string to induce a vibration, vibratory translation is technically a form of propulsion of the guitar string; this is not commonly depicted in this vocabulary, even though human muscles are considered to propel the fingertips. The motion of an object moving through a gravitational field is affected by the field, and within some frames of reference physicists speak of the gravitational field generating a force upon the object, but for general relativity, deep the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of The Highlands And Islands
, type = federal, public , image_name = UHI Coat of Arms.jpg , image_size = 150px , established = 2011 – University status 1992 – UHI Millennium Institute , chancellor = The Princess Royal , vice_chancellor = , budget = £139m (2022) , rector = Fiona McLean , principal = Vicki Nairn (Interim) , city = Highlands and Islands, Moray and Perthshire , country = Scotland, UK , colours = Black & White , total_staff = 3100 (2019) , students = 31,000 (11,201 higher education, 19,779 further education) , website uhi.ac.uk, logo = The University of the Highlands and Islands (UHI) is an integrated, tertiary institution encompassing both further and higher education. It is composed of 12 colleges and research institutions spread around the Highlands and Islands, Moray and Perthshire regions of Scotland. UHI offers further education, undergraduate, postgraduate and research programmes which can be studied at a range of locations across the area and online. It has 3 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Underwater Glider
An underwater glider is a type of autonomous underwater vehicle (AUV) that employs variable-buoyancy propulsion instead of traditional propellers or thrusters. It employs variable buoyancy in a similar way to a profiling float, but unlike a float, which can move only up and down, an underwater glider is fitted with hydrofoils (underwater wings) that allow it to glide forward while descending through the water. At a certain depth, the glider switches to positive buoyancy to climb back up and forward, and the cycle is then repeated. While not as fast as conventional AUVs, gliders offer significantly greater range and endurance compared to traditional AUVs, extending ocean sampling missions from hours to weeks or months, and to thousands of kilometers of range. The typical up-and-down, sawtooth-like profile followed by a glider can provide data on temporal and spatial scales unattainable by powered AUVs and much more costly to sample using traditional shipboard techniques. A wide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Autonomous Aircraft
An autonomous aircraft is an aircraft which flies under the control of automatic systems and needs no intervention from a human pilot. Most autonomous aircraft are unmanned aerial vehicle or drones. However, autonomous control systems are reaching a point where several air taxis and associated regulatory regimes are being developed. History Unmanned aerial vehicles The earliest recorded use of an unmanned aerial vehicle for warfighting occurred in July 1849, serving as a balloon carrier (the precursor to the aircraft carrier) Significant development of radio-controlled drones started in the early 1900s, and originally focused on providing practice targets for training military personnel. The earliest attempt at a powered UAV was A. M. Low's "Aerial Target" in 1916.Taylor, John W. R.. ''Jane's Pocket Book of Remotely Piloted Vehicles''. Autonomous features such as the autopilot and automated navigation were developed progressively through the twentieth century, although techni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BBC News
BBC News is an operational business division of the British Broadcasting Corporation (BBC) responsible for the gathering and broadcasting of news and current affairs in the UK and around the world. The department is the world's largest broadcast news organisation and generates about 120 hours of radio and television output each day, as well as online news coverage. The service maintains 50 foreign news bureaus with more than 250 correspondents around the world. Deborah Turness has been the CEO of news and current affairs since September 2022. In 2019, it was reported in an Ofcom report that the BBC spent £136m on news during the period April 2018 to March 2019. BBC News' domestic, global and online news divisions are housed within the largest live newsroom in Europe, in Broadcasting House in central London. Parliamentary coverage is produced and broadcast from studios in London. Through BBC English Regions, the BBC also has regional centres across England and national news c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Buoyancy
Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the pressure at the bottom of a column of fluid is greater than at the top of the column. Similarly, the pressure at the bottom of an object submerged in a fluid is greater than at the top of the object. The pressure difference results in a net upward force on the object. The magnitude of the force is proportional to the pressure difference, and (as explained by Archimedes' principle) is equivalent to the weight of the fluid that would otherwise occupy the submerged volume of the object, i.e. the displaced fluid. For this reason, an object whose average density is greater than that of the fluid in which it is submerged tends to sink. If the object is less dense than the liquid, the force can keep the object afloat. This can occur only in a no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heavier Than Air
An aircraft is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or by using the Lift (force), dynamic lift of an airfoil, or in a few cases the Powered lift, downward thrust from jet engines. Common examples of aircraft include airplanes, helicopters, airships (including blimps), Glider (aircraft), gliders, Powered paragliding, paramotors, and hot air balloons. The human activity that surrounds aircraft is called ''aviation''. The science of aviation, including designing and building aircraft, is called ''aeronautics.'' Aircrew, Crewed aircraft are flown by an onboard Aircraft pilot, pilot, but unmanned aerial vehicles may be remotely controlled or self-controlled by onboard computers. Aircraft may be classified by different criteria, such as lift type, Powered aircraft#Methods of propulsion, aircraft propulsion, usage and others. History Flying model craft an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aerostat
An aerostat (, via French) is a lighter-than-air aircraft that gains its lift through the use of a buoyant gas. Aerostats include unpowered balloons and powered airships. A balloon may be free-flying or tethered. The average density of the craft is lower than the density of atmospheric air, because its main component is one or more gasbags, a lightweight skin containing a lifting gas (which could be heated air or any gas of lower density than air) to provide buoyancy, to which other components such as a gondola containing equipment or people are attached. Especially with airships, the gasbags are often protected by an outer envelope. Aerostats are so named because they use aerostatic lift which is a buoyant force that does not require movement through the surrounding air mass, resulting in VTOL ability. This contrasts with the heavy aerodynes that primarily use aerodynamic lift which requires the movement of a wing surface through the surrounding air mass. The term has also be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrofoil
A hydrofoil is a lifting surface, or foil, that operates in water. They are similar in appearance and purpose to aerofoils used by aeroplanes. Boats that use hydrofoil technology are also simply termed hydrofoils. As a hydrofoil craft gains speed, the hydrofoils lift the boat's hull out of the water, decreasing drag and allowing greater speeds. Description The hydrofoil usually consists of a winglike structure mounted on struts below the hull, or across the keels of a catamaran in a variety of boats (see illustration). As a hydrofoil-equipped watercraft increases in speed, the hydrofoil elements below the hull(s) develop enough lift to raise the hull out of the water, which greatly reduces hull drag. This provides a corresponding increase in speed and fuel efficiency. Wider adoption of hydrofoils is prevented by the increased complexity of building and maintaining them. Hydrofoils are generally prohibitively more expensive than conventional watercraft above a certain disp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wing
A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's aerodynamic efficiency is expressed as its lift-to-drag ratio. The lift a wing generates at a given speed and angle of attack can be one to two orders of magnitude greater than the total drag on the wing. A high lift-to-drag ratio requires a significantly smaller thrust to propel the wings through the air at sufficient lift. Lifting structures used in water include various foils, such as hydrofoils. Hydrodynamics is the governing science, rather than aerodynamics. Applications of underwater foils occur in hydroplanes, sailboats and submarines. Etymology and usage For many centuries, the word "wing", from the Old Norse ''vængr'', referred mainly to the foremost limbs of birds (in addition to the architectural aisle). But in recent centuries the word's meaning has ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gliding Flight
Gliding flight is heavier-than-air flight without the use of thrust; the term volplaning also refers to this mode of flight in animals. It is employed by gliding animals and by aircraft such as gliders. This mode of flight involves flying a significant distance horizontally compared to its descent and therefore can be distinguished from a mostly straight downward descent like with a round parachute. Although the human application of gliding flight usually refers to aircraft designed for this purpose, most powered aircraft are capable of gliding without engine power. As with sustained flight, gliding generally requires the application of an airfoil, such as the wings on aircraft or birds, or the gliding membrane of a gliding possum. However, gliding can be achieved with a flat ( uncambered) wing, as with a simple paper plane, or even with card-throwing. However, some aircraft with lifting bodies and animals such as the flying snake can achieve gliding flight without any wings b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
