388:, spend most of their life in a cruise condition. For these airplanes, excess thrust is not as important as high engine efficiency and low fuel usage. Since thrust depends on both the amount of gas moved and the velocity, we can generate high thrust by accelerating a large mass of gas by a small amount, or by accelerating a small mass of gas by a large amount. Because of the aerodynamic efficiency of propellers and fans, it is more fuel efficient to accelerate a large mass by a small amount, which is why high-bypass turbofans and turboprops are commonly used on cargo planes and airliners.
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229:, physicists now consider the curved path of an object moving freely through space-time as shaped by gravity as a natural movement of the object, unaffected by a propulsive force (in this view, the falling apple is considered to be unpropelled, while the observer of the apple standing on the ground is considered to be propelled by the reactive force of the Earth's surface).
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An aircraft propulsion system must achieve two things. First, the thrust from the propulsion system must balance the drag of the airplane when the airplane is cruising. And second, the thrust from the propulsion system must exceed the drag of the airplane for the airplane to accelerate. The greater
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A cable car is any of a variety of transportation systems relying on cables to pull vehicles along or lower them at a steady rate. The terminology also refers to the vehicles on these systems. The cable car vehicles are motor-less and engine-less and they are pulled by a cable that is rotated by a
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systems. It is claimed that non-reliance on friction also means that acceleration and deceleration can far surpass that of existing forms of transport. The power needed for levitation is not a particularly large percentage of the overall energy consumption; most of the power used is needed to
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the wheels (rotational motion), and the wheels propel the car forward (translational motion). In common speech, propulsion is associated with spatial displacement more strongly than locally contained forms of motion, such as rotation or vibration. As another example, internal stresses in a
773:, and to escape predators. For many animals the ability to move is essential to survival and, as a result, selective pressures have shaped the locomotion methods and mechanisms employed by moving organisms. For example, migratory animals that travel vast distances (such as the
640:. There are many different methods. Each method has drawbacks and advantages, and spacecraft propulsion is an active area of research. However, most spacecraft today are propelled by forcing a gas from the back/rear of the vehicle at very high speed through a
852:). The effect of forces during locomotion on the design of the skeletal system is also important, as is the interaction between locomotion and muscle physiology, in determining how the structures and effectors of locomotion enable or limit animal movement.
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environments gravity must be overcome, though the drag of air is much less of an issue. In aqueous environments however, friction (or drag) becomes the major challenge, with gravity being less of a concern. Although animals with natural
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or experimental high speed aircraft, require very high excess thrust to accelerate quickly and to overcome the high drag associated with high speeds. For these airplanes, engine efficiency is not as important as very high thrust. Modern
494:. With maglev a vehicle is levitated a short distance away from a guide way using magnets to create both lift and thrust. Maglev vehicles are claimed to move more smoothly and quietly and to require less maintenance than wheeled
220:
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
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Influencing rotational motion is also technically a form of propulsion, but in speech, an automotive mechanic might prefer to describe the hot gasses in an engine cylinder as propelling the piston (translational motion), which
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for decades, and newer
Western geo-orbiting spacecraft are starting to use them for north–south stationkeeping and orbit raising. Interplanetary vehicles mostly use chemical rockets as well, although a few have used
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is widely used in the study of animal locomotion: if at rest, to move forward an animal must push something backward. Terrestrial animals must push the solid ground; swimming and flying animals must push against a
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cause the surface of the baseball to travel along a sinusoidal or helical trajectory, which would not happen in the absence of these interior forces; these forces meet the technical definition of propulsion from
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and have been proposed for energy-efficient propulsion. Recent development in liquified natural gas (LNG) fueled engines are gaining recognition for their low emissions and cost advantages.
777:) typically have a locomotion mechanism that costs very little energy per unit distance, whereas non-migratory animals that must frequently move quickly to escape predators (such as
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may be needed to connect the motor to axles, wheels, or propellers. A technological/biological system may use human, or trained animal, muscular work to power a mechanical device.
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than air. Limbless organisms moving on land must often contend with surface friction, but do not usually need to expend significant energy to counteract gravity.
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need not expend much energy maintaining vertical position, some will naturally sink and must expend energy to remain afloat. Drag may also present a problem in
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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
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highlight this point. Flight presents a different problem from movement in water however, as there is no way for a living organism to have lower
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are still used on some smaller boats, most modern ships are propelled by mechanical systems consisting of a motor or engine turning a
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the difference between the thrust and the drag, called the excess thrust, the faster the airplane will accelerate.
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Marine propulsion is the mechanism or system used to generate
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the crankshaft (rotational motion), the crankshaft then
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Spacecraft propulsion is any method used to accelerate
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An aircraft propulsion system generally consists of an
177:(or an articulated rigid body) but may also concern a
290:; larger objects propelled at high speed, often into
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503:), as with any other high-speed form of transport.
71:. Unsourced material may be challenged and removed.
408:may use some type of ramjet or rocket propulsion.
486:itation) is a system of transportation that uses
209:consists of a source of mechanical power, and a
158:in the exhaust plume from its propulsion system
611:A remote camera captures a close-up view of a
655:All current spacecraft use chemical rockets (
420:Wheels are commonly used in ground propulsion
365:and some means to generate thrust, such as a
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181:. The term is derived from two Latin words:
27:Means of creating force leading to movement
271:to generate the force. Components such as
131:Learn how and when to remove this message
549:, or less frequently, in jet drives, an
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663:) for launch, though some (such as the
400:usually have an afterburner added to a
286:, propelled at high speed are known as
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933:"Energy Efficient - All Electric Ship"
919:"Beginner's Guide to Propulsion NASA"
571:diesel engines, outboard motors, and
216:Plucking a guitar string to induce a
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69:adding citations to reliable sources
699:. Soviet bloc satellites have used
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957:Biewener, Andrew A. (2003-06-19).
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515:A view of a ship's engine room
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36:Power plant (disambiguation)
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825:efficient body shapes of
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1004:"Propulsion Efficiency"
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282:Small objects, such as
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722:Cable car (railway)
701:electric propulsion
573:gas turbine engines
488:magnetic levitation
406:hypersonic aircraft
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325:Newtonian mechanics
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677:first stage
585:icebreakers
569:four-stroke
288:projectiles
121:August 2017
1033:Propulsion
1027:Categories
994:Propulsion
943:2009-11-25
873:References
821:, and the
661:solid-fuel
638:satellites
634:spacecraft
593:submarines
565:two-stroke
529:to move a
461:09 at the
459:Transrapid
265:propellers
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233:Biological
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175:rigid body
163:Propulsion
91:newspapers
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867:Transport
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675:on their
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404:. Future
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352:turboprop
277:gearboxes
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187:, meaning
856:See also
844:(either
815:buoyancy
794:friction
759:swimming
581:warships
551:impeller
382:aircraft
320:baseball
317:rotating
300:missiles
273:clutches
203:to drive
150:'s quad
862:Jetpack
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806:gravity
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193:forward
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412:Ground
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189:before
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380:Some
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205:. A
179:fluid
167:force
112:JSTOR
98:books
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