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Flight or flying is the process by which an
object Object may refer to: General meanings * Object (philosophy), a thing, being, or concept ** Entity, something that is tangible and within the grasp of the senses ** Object (abstract), an object which does not exist at any particular time or pl ...
moves through a
space Space is the boundless three-dimensional extent in which objects and events have relative position and direction. Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time ...

space
without contacting any
planetary surface OSIRIS-REx collecting a surface sample from asteroid 101955 Bennu in 2020— ''(:File:OSIRIS-REX SamCam TAGSAM Event 2020-10-20.gif, Full-sized image)'' A planetary surface is where the solid (or liquid) material of the outer crust (geology), cru ...
, either within an
atmosphere An atmosphere (from the greek words ἀτμός ''(atmos)'', meaning 'vapour', and σφαῖρα ''(sphaira)'', meaning 'ball' or 'sphere') is a layer or a set of layers of gases surrounding a planet or other material body, that is held in ...
(i.e. air flight or
aviation Aviation is the activities surrounding mechanical flight Flight or flying is the process by which an object (physics), object motion (physics), moves through a space without contacting any planetary surface, either within an atmosphere (i.e. ...
) or through the
vacuum A vacuum is a space devoid of matter. The word is derived from the Latin adjective ''vacuus'' for "vacant" or "Void (astronomy), void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Ph ...

vacuum
of
outer space Outer space is the expanse that exists beyond Earth and between astronomical object, celestial bodies. Outer space is not completely empty—it is a hard vacuum containing a low density of particles, predominantly a plasma (physics), plasma ...
(i.e.
spaceflight Spaceflight (or space flight) is an application of astronautics to fly spacecraft into or through outer space, either human spaceflight, with or uncrewed spaceflight, without humans on board. Most spaceflight is uncrewed and conducted mainly wit ...
). This can be achieved by generating
aerodynamic lift A fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shear stress, or external force. Fluids are a Phase (matter), phase of matter and include liquids, Gas, gases and Plasma (p ...
associated with
gliding Gliding is a recreational activity and competitive air sports, air sport in which pilots fly glider aircraft, unpowered aircraft known as Glider (sailplane), gliders or sailplanes using naturally occurring currents of rising air in the atmosphere ...
or propulsive thrust,
aerostat An aerostat (From greek language, Greek ἀήρ ''aer'' (air) + στατός ''statos'' (standing) through French) is a lighter than air aircraft that gains its lift through the use of a buoyant gas. Aerostats include unpowered balloon (aircraft ...
ically using
buoyancy . Buoyancy (), or upthrust, is an upward force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies mat ...
, or by
ballistic Ballistics may refer to: Science * Ballistics, the science that deals with the motion, behavior, and effects of projectiles. ** Forensic ballistics, the science of analyzing firearm usage in crimes ** Internal ballistics Internal may refer t ...
movement. Many things can fly, from animal aviators such as
bird Birds are a group of warm-blooded vertebrates constituting the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of indiv ...
s,
bat Bats are mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glands which in Female#Mammalian femal ...
s and
insect Insects (from Latin ') are pancrustacean Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, Thorax (inse ...

insect
s, to natural gliders/parachuters such as patagial animals,
anemochorous Seed dispersal is the movement, spread or transport of seed A seed is an embryonic plant enclosed in a protective outer covering. The formation of the seed is part of the process of reproduction Reproduction (or procreation or breeding) ...
seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was released to generally positiv ...

seed
s and
ballistosporeA ballistospore or ballistoconida is a spore )'', growing on a thinned hybrid black poplar ''(Populus x canadensis)''. The last stage of the moss lifecycle is shown, where the sporophytes are visible before dispersion of their spores: the caly ...
s, to human inventions like
aircraft An aircraft is a vehicle or machine that is able to fly Flies are insect Insects or Insecta (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Lat ...
(
airplane An airplane or aeroplane (informally plane) is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, Propeller (aircraft), propeller, or rocket engine. Airplanes come in a variety of sizes, shapes, and wing configurati ...

airplane
s,
helicopter A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally-spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...

helicopter
s,
airship An airship, dirigible balloon or blimp is a type of aerostat or lighter-than-air aircraft that can navigate through the air under its own power. Aerostats gain their lift from a lifting gas that is less dense than the surrounding air. In ea ...
s,
balloon A balloon is a flexible bag that can be inflated with a gas, such as helium Helium (from el, ἥλιος, Helios, lit=Sun) is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table ...
s, etc.) and
rocket A rocket (from it, rocchetto, , bobbin/spool) is a projectile that spacecraft, aircraft 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 ...

rocket
s which may propel
spacecraft File:Space Shuttle Columbia launching.jpg, 275px, The US Space Shuttle flew 135 times from 1981 to 2011, supporting Spacelab, ''Mir'', the Hubble Space Telescope, and the ISS. (''Columbia'' STS-1, maiden launch, which had a white external tank, ...

spacecraft
and
spaceplane A spaceplane is a vehicle that can flight, fly and gliding flight, glide like an aircraft in Earth's atmosphere and maneuver like a spacecraft in outer space. To do so, spaceplanes must incorporate features of both aircraft and spacecraft. Or ...
s. The engineering aspects of flight are the purview of
aerospace engineering Aerospace engineering is the primary field of engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and build ...
which is subdivided into
aeronautics Aeronautics is the science or art involved with the study, design, and manufacturing of air flight Flight or flying is the process by which an object (physics), object motion (physics), moves through a space without contacting any planetary ...
, the study of vehicles that travel through the atmosphere, and
astronautics Astronautics (or cosmonautics) is the theory and practice of travel beyond atmosphere of Earth, Earth's atmosphere into outer space. Spaceflight is one of its main applications and space science its overarching field. The term ''astronautics'' (or ...
, the study of vehicles that travel through space, and
ballistics Ballistics is the field of mechanics concerned with the launching, flight behavior and impact effects of projectiles, especially ranged weapon munitions such as bullets, unguided bombs, rockets or the like; the science or art of designing and ac ...
, the study of the flight of projectiles.


Types of flight


Buoyant flight

Humans have managed to construct lighter-than-air vehicles that raise off the ground and fly, due to their
buoyancy . Buoyancy (), or upthrust, is an upward force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies mat ...
in air. An aerostat is a system that remains aloft primarily through the use of
buoyancy . Buoyancy (), or upthrust, is an upward force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies mat ...
to give an aircraft the same overall density as air. Aerostats include free balloons,
airship An airship, dirigible balloon or blimp is a type of aerostat or lighter-than-air aircraft that can navigate through the air under its own power. Aerostats gain their lift from a lifting gas that is less dense than the surrounding air. In ea ...
s, and
moored balloon A tethered, moored or captive balloon is a Balloon (aircraft), balloon that is restrained by one or more tethers attached to the ground and so it cannot float freely. The base of the tether is wound around the drum of a winch, which may be fixed or ...
s. An aerostat's main structural component is its
envelope An envelope is a common packaging Packaging is the art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of designing, evaluating, and producing packages. Packa ...
, a lightweight
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have differe ...

skin
that encloses a volume of
lifting gas A lifting gas or lighter than air gas is a gas that has a lower density than normal atmospheric gases and rises above them as a result. It is required for aerostats An aerostat (From Greek Greek may refer to: Greece Anything of, from, or rel ...
to provide
buoyancy . Buoyancy (), or upthrust, is an upward force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies mat ...
, to which other components are attached. Aerostats are so named because they use "aerostatic" lift, a
buoyant . Buoyancy (), or upthrust, is an upward force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies mat ...
force that does not require lateral movement through the surrounding air mass to effect a lifting force. By contrast, aerodynes primarily use
aerodynamic study at Wallops Flight Facility, Wallops Island in 1990. A vortex is created by passage of an aircraft wing, revealed by smoke. Vortices are one of the many phenomena associated with the study of aerodynamics. Aerodynamics, from Greek language, ...
lift Lift or LIFT may refer to: Physical devices * Elevator, or lift, a device used for raising and lowering people or goods ** Rack lift, a type of elevator ** Ski lift, an aerial or surface lift for uphill transport ** Space elevator, a hypothetical ...
, which requires the lateral movement of at least some part of the
aircraft An aircraft is a vehicle or machine that is able to fly Flies are insect Insects or Insecta (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Lat ...
through the surrounding air mass.


Aerodynamic flight


Unpowered flight versus powered flight

Some things that fly do not generate propulsive thrust through the air, for example, the
flying squirrel Flying squirrels (scientifically known as Pteromyini or Petauristini) are a tribe of 50 species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of ...

flying squirrel
. This is termed
gliding Gliding is a recreational activity and competitive air sports, air sport in which pilots fly glider aircraft, unpowered aircraft known as Glider (sailplane), gliders or sailplanes using naturally occurring currents of rising air in the atmosphere ...
. Some other things can exploit rising air to climb such as raptors (when gliding) and
man-made sailplane gliders
man-made sailplane gliders
. This is termed soaring. However most other birds and all
powered aircraft A powered aircraft is an aircraft An aircraft is a vehicle or machine that is able to fly Flies are insect Insects or Insecta (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic bran ...
need a source of
propulsion Propulsion is the action or process of pushing or pulling to drive an object forward. The term is derived from two Latin words: '' pro'', meaning'' before'' or ''forward''; and '' pellere'', meaning ''to drive''. A propulsion system consists of ...

propulsion
to climb. This is termed powered flight.


Animal flight

The only groups of living things that use powered flight are
bird Birds are a group of warm-blooded vertebrates constituting the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of indiv ...
s,
insect Insects (from Latin ') are pancrustacean Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, Thorax (inse ...

insect
s, and
bat Bats are mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glands which in Female#Mammalian femal ...
s, while many groups have evolved gliding. The extinct
pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") were flying reptiles of the extinct clade or Order (biology), order Pterosauria. They existed during most of the Mesozoic: from the late Triassic to the end of the Cretace ...
s, an
order Order or ORDER or Orders may refer to: * Orderliness Orderliness is associated with other qualities such as cleanliness Cleanliness is both the abstract state of being clean and free from germs, dirt, trash, or waste, and the habit of achieving a ...
of reptiles contemporaneous with the
dinosaur Dinosaurs are a diverse group of reptiles of the clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic—that is, composed of a ...
s, were also very successful flying animals. Each of these groups'
wing A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined Cross section (geometry), cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's Aerody ...

wing
s evolved independently, with insects the first animal group to evolve flight. The wings of the flying vertebrate groups are all based on the forelimbs, but differ significantly in structure; those of insects are hypothesized to be highly modified versions of structures that form gills in most other groups of
arthropod An arthropod (, (gen. ποδός)) is an invertebrate animal having an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Euarthropoda,Reference showing that Euarthropoda is a phylum: ...
s.Averof, Michalis
"Evolutionary origin of insect wings from ancestral gills."
''Nature'', Volume 385, Issue 385, February 1997, pp. 627–630.
Bat Bats are mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glands which in Female#Mammalian femal ...
s are the only
mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), class Mammalia (), and characterized by the presence of mammary glands which in Female#Mammalian female, females produce milk ...
s capable of sustaining level flight (see ''
bat flight Bats are the only mammal capable of Active flight in animals, true flight. Bats use flight for capturing prey, breeding, avoiding predators, and long-distance migration. Bat wing morphology is often highly specialized to the needs of the species. E ...

bat flight
''). However, there are several which are able to glide from tree to tree using fleshy membranes between their limbs; some can travel hundreds of meters in this way with very little loss in height.
Flying frog A flying frog (also called a gliding frog) is a frog that has the ability to achieve gliding flight. That is, it can descend at an angle less than 45° relative to the horizontal. Other (nonflying) arboreal frogs can also descend, but only at ang ...
s use greatly enlarged webbed feet for a similar purpose, and there are
flying lizards The Flying Lizards were an experimental English New wave music, new wave band, formed in 1976. They are best known for their eccentric cover version of Barrett Strong's "Money (That's What I Want), Money" featuring Deborah Evans-Stickland on lea ...
which fold out their mobile ribs into a pair of flat gliding surfaces. "Flying" snakes also use mobile ribs to flatten their body into an aerodynamic shape, with a back and forth motion much the same as they use on the ground.
Flying fish The Exocoetidae are a family (biology), family of marine fish in the order (biology), order Beloniformes class (biology), class Actinopterygii, known colloquially as flying fish or flying cod. About 64 species are grouped in seven to nine genus ...

Flying fish
can glide using enlarged wing-like fins, and have been observed soaring for hundreds of meters. It is thought that this ability was chosen by
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the Heredity, heritable Phenotypic trait, traits characteristic of a populatio ...
because it was an effective means of escape from underwater predators. The longest recorded flight of a flying fish was 45 seconds."BBC article and video of flying fish."
''BBC'', May 20, 2008. Retrieved: May 20, 2008.
Most
bird Birds are a group of warm-blooded vertebrates constituting the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of indiv ...
s fly (''see
bird flight Bird flight is the primary mode of locomotion used by most bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves , characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggsh ...
''), with some exceptions. The largest birds, the
ostrich ''Struthio'' is a genus of birds in the order (biology), order Struthioniformes, whose members are the ostriches. It is part of the infra-class Palaeognathae, a diverse group of flightless birds also known as ratites that includes the emus, Rhea ( ...

ostrich
and the
emu The emu (''Dromaius novaehollandiae'') is the second-largest living bird by height, after its ratite relative, the ostrich. It is endemic Endemism is the state of a species In biology, a species is the basic unit of biological c ...

emu
, are earthbound
flightless bird s are a well-known example of flightless birds. Flightless birds are birds that through evolution lost the ability to flight, fly. There are over 60 extant species, including the well known ratites (ostriches, emu, cassowary, cassowaries, Rhea ...
s, as were the now-extinct
dodo The dodo (''Raphus cucullatus'') is an extinct Extinction is the termination of a kind of organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that ...

dodo
s and the Phorusrhacids, which were the dominant predators of
South America South America is a continent A continent is one of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven regions are commonly regarded as continents. Ordered fr ...

South America
in the
Cenozoic The Cenozoic ( ; ) is Earth's current geological era An era is a span of time defined for the purposes of chronology or historiography, as in the regnal eras in the history of a given monarchy, a calendar era used for a given calendar, or the ge ...

Cenozoic
era. The non-flying
penguin Penguins (order (biology), order Sphenisciformes , family (biology), family Spheniscidae ) are a group of Water bird, aquatic flightless bird, flightless birds. They live almost exclusively in the southern hemisphere: only one species, the Gal ...

penguin
s have wings adapted for use under water and use the same wing movements for swimming that most other birds use for flight. Most small flightless birds are native to small islands, and lead a lifestyle where flight would offer little advantage. Among living animals that fly, the
wandering albatross The wandering albatross, snowy albatross, white-winged albatross or goonie (''Diomedea exulans'') is a large seabird Seabirds (also known as marine birds) are bird Birds are a group of warm-blooded vertebrates constituting the class ( ...
has the greatest wingspan, up to ; the
great bustard The great bustard (''Otis tarda'') is a bird in the bustard family, the only member of the genus Genus (plural genera) is a taxonomic rank Taxonomy (general) is the practice and science of classification of things or concepts, including the ...
has the greatest weight, topping at . Most species of
insect Insects (from Latin ') are pancrustacean Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, Thorax (inse ...

insect
s can fly as adults.
Insect flight Insect Insects or Insecta (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through th ...
makes use of either of two basic aerodynamic models: creating a leading edge vortex, found in most insects, and using
clap and fling Insects are the only group of invertebrates that have evolved insect wing, wings and flight. Insects first flew in the Carboniferous, some 350 to 400 million years ago. Wings may have evolved from appendages on the sides of existing limbs, which al ...
, found in very small insects such as
thrips Thrips ( order Thysanoptera) are minute (mostly 1 mm long or less), slender insect Insects or Insecta (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European langua ...

thrips
.


Mechanical

Mechanical flight is the use of a
machine A machine is any physical system with ordered structural and functional properties. It may represent human-made or naturally occurring device molecular machine that uses Power (physics), power to apply Force, forces and control Motion, movement ...

machine
to fly. These machines include
aircraft An aircraft is a vehicle or machine that is able to fly Flies are insect Insects or Insecta (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Lat ...
such as
airplane An airplane or aeroplane (informally plane) is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, Propeller (aircraft), propeller, or rocket engine. Airplanes come in a variety of sizes, shapes, and wing configurati ...

airplane
s,
gliders Glider may refer to: Aircraft and transport Aircraft * Glider (aircraft), heavier-than-air aircraft primarily intended for unpowered flight ** Glider (sailplane), a rigid-winged glider aircraft with an undercarriage, used in the sport of gliding * ...
,
helicopter A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally-spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...

helicopter
s,
autogyro An autogyro (from Greek and , "self-turning"), also known as a gyroplane or gyrocopter, is a type of rotorcraft that uses an unpowered rotor in free autorotation to develop lift. Forward thrust is provided independently, by an engine-driven ...
s,
airship An airship, dirigible balloon or blimp is a type of aerostat or lighter-than-air aircraft that can navigate through the air under its own power. Aerostats gain their lift from a lifting gas that is less dense than the surrounding air. In ea ...
s,
balloons A balloon is a flexible bag that can be inflated with a gas, such as helium, hydrogen, nitrous oxide, oxygen, and Atmosphere of Earth, air. For special tasks, balloons can be filled with smoke, liquid water, granular media (e.g. sand, flour ...
,
ornithopter An ornithopter (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 ...
s as well as
spacecraft File:Space Shuttle Columbia launching.jpg, 275px, The US Space Shuttle flew 135 times from 1981 to 2011, supporting Spacelab, ''Mir'', the Hubble Space Telescope, and the ISS. (''Columbia'' STS-1, maiden launch, which had a white external tank, ...

spacecraft
.
Gliders Glider may refer to: Aircraft and transport Aircraft * Glider (aircraft), heavier-than-air aircraft primarily intended for unpowered flight ** Glider (sailplane), a rigid-winged glider aircraft with an undercarriage, used in the sport of gliding * ...
are capable of unpowered flight. Another form of mechanical flight is para-sailing, where a parachute-like object is pulled by a boat. In an airplane, lift is created by the wings; the shape of the wings of the airplane are designed specially for the type of flight desired. There are different types of wings: tempered, semi-tempered, sweptback, rectangular and elliptical. An aircraft wing is sometimes called an
airfoil An airfoil (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American English ...

airfoil
, which is a device that creates lift when air flows across it.


=Supersonic

= Supersonic flight is flight faster than the
speed of sound The speed of sound is the distance travelled per unit of time by a sound wave as it propagates through an elasticity (solid mechanics), elastic medium. At , the speed of sound in air is about , or one kilometre in or one mile in . It depends s ...
. Supersonic flight is associated with the formation of
shock wave of an attached shock on a sharp-nosed supersonic body firing a broadside during training exercises in Puerto Rico, 1984. Circular marks are visible where the expanding spherical atmospheric shockwaves from the gun firing meet the water surfac ...
s that form a
sonic boom NASA data showing N-wave signature. A sonic boom is a sound associated with shock waves created when an object travels through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding similar to ...

sonic boom
that can be heard from the ground, and is frequently startling. This shockwave takes quite a lot of energy to create and this makes supersonic flight generally less efficient than subsonic flight at about 85% of the speed of sound.


=Hypersonic

= Hypersonic flight is very high speed flight where the heat generated by the compression of the air due to the motion through the air causes chemical changes to the air. Hypersonic flight is achieved primarily by reentering spacecraft such as the
Space Shuttle The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. NASA, National Aeronautics and Space Administration (NASA) as part of the Space Shuttle progra ...

Space Shuttle
and
Soyuz "Soyuz" is a transliteration of the Cyrillic text "Союз", and is the Russian word for "Union". It was often used as an internal abbreviation for the Union of Soviet Socialist Republics ("''Сою́з Сове́тских Социалисти́ ...

Soyuz
.


Ballistic


Atmospheric

Some things generate little or no lift and move only or mostly under the action of momentum, gravity, air drag and in some cases thrust. This is termed ''ballistic flight''. Examples include
ball A ball is a round object (usually spherical, but can sometimes be ovoid An oval (from Latin ''ovum'', "egg") is a closed curve in a plane which resembles the outline of an egg. The term is not very specific, but in some areas ( projective ...

ball
s,
arrowsArrows may refer to: * more than one arrow * Arrows (Australian band), indie rock band established 2006 * Arrows (British band), 1970s Anglo-American glam rock-pop band * Arrows (Unicode block), a Unicode block containing line, curve, and semicircle ...

arrows
,
bullet A bullet is a kinetic projectile, a component of firearm ammunition that is Shooting, shot from a gun barrel. The term is from Middle French, originating as the diminutive of the word ''boulle'' (''boullet''), which means "small ball". Bullets ar ...

bullet
s,
firework Fireworks are a class of low explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion An explosion is a rapid expansion in volume associat ...

firework
s etc.


Spaceflight

Essentially an extreme form of ballistic flight, spaceflight is the use of
space technology Space technology is technology Technology ("science of craft", from Ancient Greek, Greek , ''techne'', "art, skill, cunning of hand"; and , ''wikt:-logia, -logia'') is the sum of Art techniques and materials, techniques, skills, Scientific me ...
to achieve the flight of
spacecraft File:Space Shuttle Columbia launching.jpg, 275px, The US Space Shuttle flew 135 times from 1981 to 2011, supporting Spacelab, ''Mir'', the Hubble Space Telescope, and the ISS. (''Columbia'' STS-1, maiden launch, which had a white external tank, ...

spacecraft
into and through
outer space Outer space is the expanse that exists beyond Earth and between astronomical object, celestial bodies. Outer space is not completely empty—it is a hard vacuum containing a low density of particles, predominantly a plasma (physics), plasma ...
. Examples include
ballistic missile A ballistic missile follows a ballistic trajectory to deliver one or more warheads on a predetermined target. These weapons are guided only during relatively brief periods—most of the flight is unpowered. Short-range ballistic missiles stay ...
s,
orbital spaceflight An orbital spaceflight (or orbital flight) is a spaceflight in which a spacecraft is placed on a trajectory where it could remain in space for at least one orbit In physics, an orbit is the gravitationally curved trajectory of an phys ...
, etc. Spaceflight is used in
space exploration Space exploration is the use of astronomy and space technology to explore outer space. While the exploration of space is carried out mainly by astronomers with telescopes, its physical exploration though is conducted both by robotic spacecra ...
, and also in commercial activities like
space tourism Space tourism is Human spaceflight, human space travel for recreational purposes. There are several different types of space tourism, including orbital, suborbital and lunar space tourism. During the period from 2001 to 2009, seven space tour ...
and satellite telecommunications. Additional non-commercial uses of spaceflight include
space observatories A space telescope or space observatory is a telescope located in outer space to observe distant planets, galaxy, galaxies and other astronomical objects. Space telescopes avoid the filtering of ultraviolet frequencies, X-rays and gamma rays; the ...
,
reconnaissance satellite A reconnaissance satellite or intelligence satellite (commonly, although unofficially, referred to as a spy satellite) is an Earth observation satellite An Earth observation satellite or Earth remote sensing satellite is a satellite us ...
s and other
earth observation satellite An Earth observation satellite or Earth remote sensing satellite is a satellite used or designed for Earth observation (EO) from orbit, including spy satellites and similar ones intended for non-military uses such as natural environment, environm ...
s. A spaceflight typically begins with a
rocket launch A rocket (from it, rocchetto, , bobbin/spool) is a spacecraft File:Space Shuttle Columbia launching.jpg, 275px, The US Space Shuttle flew 135 times from 1981 to 2011, supporting Spacelab, ''Mir'', the Hubble Space Telescope, and the ISS. (' ...
, which provides the initial thrust to overcome the force of
gravity Gravity (), or gravitation, is a list of natural phenomena, natural phenomenon by which all things with mass or energy—including planets, stars, galaxy, galaxies, and even light—are brought toward (or ''gravitate'' toward) one another. ...

gravity
and propels the spacecraft from the surface of the Earth. Once in space, the motion of a spacecraft—both when unpropelled and when under propulsion—is covered by the area of study called
astrodynamics Orbital mechanics or astrodynamics is the application of ballistics Ballistics is the field of mechanics concerned with the launching, flight behavior and impact effects of projectiles, especially ranged weapon munitions such as bullets, ung ...
. Some spacecraft remain in space indefinitely, some disintegrate during
atmospheric reentry An atmosphere (from the greek words ἀτμός ''(atmos)'', meaning 'vapour', and σφαῖρα ''(sphaira)'', meaning 'ball' or 'sphere') is a layer or a set of layers of gases surrounding a planet or other solid, material body, that is held ...
, and others reach a planetary or lunar surface for landing or impact.


Solid-state propulsion

In 2018, researchers at
Massachusetts Institute of Technology Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts Cambridge ( ) is a city in Middlesex County, Massachusetts, Middlesex County, Massachusetts, and part of the Greater Bos ...
(MIT) managed to fly an aeroplane with no moving parts, powered by an "
ion An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ...
ic wind" also known as electroaerodynamic thrust.


History

Many human cultures have built devices that fly, from the earliest projectiles such as stones and spears, the
boomerang A boomerang is a thrown tool, typically constructed as a flat airfoil An airfoil (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of t ...

boomerang
in
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, smal ...

Australia
, the hot air
Kongming lantern A sky lantern (), also known as Kǒngmíng lantern (simplified Chinese: 孔明灯; traditional Chinese: 孔明燈), or Chinese lantern, is a small hot air balloon A hot-air balloon is a lighter-than-air aircraft consisting of a bag, calle ...
, and
kite . This sparless, ram-air inflated kite, has a complex bridle formed of many strings attached to the face of the wing. A kite is a tether A tether is a cord, fixture, or flexible attachment that characteristically anchors something movable to s ...

kite
s.


Aviation

George Cayley Sir George Cayley, 6th Baronet (27 December 1773 – 15 December 1857) was an English engineer Engineers, as practitioners of engineering, are Professional, professionals who Invention, invent, design, analyze, build and test Machine, machi ...

George Cayley
studied flight scientifically in the first half of the 19th century, and in the second half of the 19th century
Otto Lilienthal Karl Wilhelm Otto Lilienthal (23 May 1848 – 10 August 1896) was a Germany, German pioneer of aviation who became known as the "flying man". He was the first person to make well-documented, repeated, successful flights with Glider (aircraft), ...

Otto Lilienthal
made over 200 gliding flights and was also one of the first to understand flight scientifically. His work was replicated and extended by the who made gliding flights and finally the first controlled and extended, manned powered flights.


Spaceflight

Spaceflight, particularly
human spaceflight Human spaceflight (also referred to as manned spaceflight or crewed spaceflight) is spaceflight with a crew or passengers aboard a spacecraft, the spacecraft being operated directly by the onboard human crew. Spacecraft can also be telerobotic ...

human spaceflight
became a reality in the 20th century following theoretical and practical breakthroughs by
Konstantin Tsiolkovsky Konstantin Eduardovich Tsiolkovsky (russian: Константи́н Эдуа́рдович Циолко́вский , , p=kənstɐnʲˈtʲin ɪdʊˈardəvʲɪtɕ tsɨɐlˈkofskʲɪj , a=Ru-Konstantin Tsiolkovsky.oga; – 19 September 1935) wa ...
and
Robert H. Goddard Robert Hutchings Goddard (October 5, 1882 – August 10, 1945) was an American engineer Engineers, as practitioners of engineering, are Professional, professionals who Invention, invent, design, analyze, build and test Machine, mac ...
. The was in 1957, and
Yuri Gagarin#REDIRECT Yuri Gagarin {{Redirect category shell, {{R from miscapitalisation {{R unprintworthy ...
was carried aboard the first manned orbital spaceflight in 1961.


Physics

There are different approaches to flight. If an object has a lower
density The density (more precisely, the volumetric mass density; also known as specific mass), of a substance is its mass per unit volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter Rho (letter), rho), although the L ...

density
than air, then it is
buoyant . Buoyancy (), or upthrust, is an upward force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies mat ...

buoyant
and is able to float in the air without expending energy. A heavier than air craft, known as an aerodyne, includes flighted animals and insects,
fixed-wing aircraft A fixed-wing aircraft is a heavier-than-air Aircraft, flying machine, such as an airplane, which is capable of flight using wings that generate Lift (force), lift caused by the aircraft's forward airspeed and the wing configuration, shape of t ...
and
rotorcraft A rotorcraft or rotary-wing aircraft is a heavier-than-air aircraft 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 ...
. Because the craft is heavier than air, it must generate
lift Lift or LIFT may refer to: Physical devices * Elevator, or lift, a device used for raising and lowering people or goods ** Rack lift, a type of elevator ** Ski lift, an aerial or surface lift for uphill transport ** Space elevator, a hypothetical ...
to overcome its
weight In science and engineering, the weight of an object is the force acting on the object due to gravity. Some standard textbooks define weight as a Euclidean vector, vector quantity, the gravitational force acting on the object. Others define weight ...

weight
. The wind resistance caused by the craft moving through the air is called
drag Drag or The Drag may refer to: Places * Drag, Norway, a village in Tysfjord municipality, Nordland, Norway * ''Drág'', the Hungarian name for Dragu Commune in Sălaj County, Romania * Drag (Austin, Texas), the portion of Guadalupe Street adja ...
and is overcome by propulsive thrust except in the case of
gliding Gliding is a recreational activity and competitive air sports, air sport in which pilots fly glider aircraft, unpowered aircraft known as Glider (sailplane), gliders or sailplanes using naturally occurring currents of rising air in the atmosphere ...
. Some vehicles also use thrust for flight, for example
rocket A rocket (from it, rocchetto, , bobbin/spool) is a projectile that spacecraft, aircraft 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 ...

rocket
s and
Harrier Jump Jet The Harrier, informally referred to as the Harrier Jump Jet, is a family of jet-powered attack aircraft An attack aircraft, strike aircraft, or attack bomber is a tactical military aircraft that has a primary role of carrying out airstrikes ...
s. Finally,
momentum In Newtonian mechanics, linear momentum, translational momentum, or simply momentum is the product of the mass Mass is both a property Property (''latin: Res Privata'') in the Abstract and concrete, abstract is what belongs to or w ...

momentum
dominates the flight of ballistic flying objects.


Forces

Forces relevant to flight are * Propulsive thrust (except in gliders) *
Lift Lift or LIFT may refer to: Physical devices * Elevator, or lift, a device used for raising and lowering people or goods ** Rack lift, a type of elevator ** Ski lift, an aerial or surface lift for uphill transport ** Space elevator, a hypothetical ...
, created by the reaction to an airflow *
Drag Drag or The Drag may refer to: Places * Drag, Norway, a village in Tysfjord municipality, Nordland, Norway * ''Drág'', the Hungarian name for Dragu Commune in Sălaj County, Romania * Drag (Austin, Texas), the portion of Guadalupe Street adja ...
, created by aerodynamic
friction Friction is the force In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related en ...

friction
*
Weight In science and engineering, the weight of an object is the force acting on the object due to gravity. Some standard textbooks define weight as a Euclidean vector, vector quantity, the gravitational force acting on the object. Others define weight ...

Weight
, created by gravity *
Buoyancy . Buoyancy (), or upthrust, is an upward force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies mat ...

Buoyancy
, for lighter than air flight These forces must be balanced for stable flight to occur.


Thrust

A
fixed-wing aircraft A fixed-wing aircraft is a heavier-than-air Aircraft, flying machine, such as an airplane, which is capable of flight using wings that generate Lift (force), lift caused by the aircraft's forward airspeed and the wing configuration, shape of t ...
generates forward thrust when air is pushed in the direction opposite to flight. This can be done in several ways including by the spinning blades of a
propeller . A propeller is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral, that, when rotated, exerts linear thrust upon a working fluid, such as water or air. Propellers are used to pump fluid through a ...
, or a rotating
fan Fan commonly refers to: * Fan (machine), a machine for producing airflow, often for cooling ** Hand fan, an implement held and waved by hand to move air * Fan (person), short for fanatic; an enthusiast or supporter, especially with regard to enterta ...

fan
pushing air out from the back of a
jet engine A jet engine is a type of reaction engine A reaction engine is an engine or motor that produces thrust by expelling reaction mass, in accordance with Newton's third law of motion. This law of motion is most commonly paraphrased as: "For ...

jet engine
, or by ejecting hot gases from a
rocket engine A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive Jet (fluid), jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, i ...

rocket engine
. The forward thrust is proportional to the
mass Mass is the physical quantity, quantity of ''matter'' in a physical body. It is also a measure (mathematics), measure of the body's ''inertia'', the resistance to acceleration (change of velocity) when a net force is applied. An object's mass ...
of the airstream multiplied by the difference in
velocity The velocity of an object is the rate of change of its position with respect to a frame of reference In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (ph ...

velocity
of the airstream. Reverse thrust can be generated to aid braking after landing by reversing the pitch of variable-pitch propeller blades, or using a
thrust reverser Thrust reversal, also called reverse thrust, is the temporary diversion of an aircraft engine's thrust for it to act against the forward travel of the aircraft, providing deceleration. Thrust reverser systems are featured on many jet aircraft to ...
on a jet engine.
Rotary wing aircraft A rotorcraft or rotary-wing aircraft is a heavier-than-air aircraft 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 ...
and
thrust vectoring Thrust vectoring, also known as thrust vector control (TVC), is the ability of an aircraft, rocket, or other vehicle to manipulate the direction of the thrust from its engine(s) or motor(s) to flight control, control the Attitude control, attitude ...
V/STOL A vertical and/or short take-off and landing (V/STOL) aircraft is an airplane able to takeoff and landing, take-off or land vertically or on short runways. VTOL, Vertical takeoff and landing (VTOL) aircraft are a subset of V/STOL craft that do ...
aircraft use engine thrust to support the weight of the aircraft, and vector sum of this thrust fore and aft to control forward speed.


Lift

In the context of an
air flow Airflow, or air flow, is the movement of air. The primary cause of airflow is the existence of air. Air behaves in a fluid manner, meaning particles naturally flow from areas of higher pressure to those where the pressure is lower. Atmospheric pres ...
relative to a flying body, the lift force is the
component Component may refer to: In engineering, science, and technology Generic systems *System components, an entity with discrete structure, such as an assembly or software module, within a system considered at a particular level of analysis *Lumped ele ...

component
of the
aerodynamic force Forces on an aerofoil. An aerodynamic force is a force exerted on a body by the air (or other gas) in which the body is immersed, and is due to the relative motion between the body and the gas. There are two causes of Aerodynamics, aerodynamic forc ...
that is
perpendicular In elementary geometry Geometry (from the grc, γεωμετρία; ''wikt:γῆ, geo-'' "earth", ''wikt:μέτρον, -metron'' "measurement") is, with arithmetic, one of the oldest branches of mathematics. It is concerned with propertie ...

perpendicular
to the flow direction. Aerodynamic lift results when the wing causes the surrounding air to be deflected - the air then causes a force on the wing in the opposite direction, in accordance with Newton's third law of motion. Lift is commonly associated with the
wing A wing is a type of fin that produces lift while moving through air or some other fluid. Accordingly, wings have streamlined Cross section (geometry), cross-sections that are subject to aerodynamic forces and act as airfoils. A wing's Aerody ...

wing
of an
aircraft An aircraft is a vehicle or machine that is able to fly Flies are insect Insects or Insecta (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Lat ...
, although lift is also generated by rotors on
rotorcraft A rotorcraft or rotary-wing aircraft is a heavier-than-air aircraft 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 ...
(which are effectively rotating wings, performing the same function without requiring that the aircraft move forward through the air). While common meanings of the word "
lift Lift or LIFT may refer to: Physical devices * Elevator, or lift, a device used for raising and lowering people or goods ** Rack lift, a type of elevator ** Ski lift, an aerial or surface lift for uphill transport ** Space elevator, a hypothetical ...

lift
" suggest that lift opposes gravity, aerodynamic lift can be in any direction. When an aircraft is
cruising Cruising may refer to: * Cruising, on a cruise ship *Cruising (driving), driving around for social purposes, especially by teenagers *Cruising (maritime), leisurely travel by boat, yacht, or cruise ship *Cruising for sex, the process of searching i ...
for example, lift does oppose gravity, but lift occurs at an angle when climbing, descending or banking. On high-speed cars, the lift force is directed downwards (called "down-force") to keep the car stable on the road.


Drag

For a solid object moving through a fluid, the drag is the component of the
net Net or net may refer to: Mathematics and physics * Net (mathematics), a filter-like topological generalization of a sequence * Net, a linear system of divisors of dimension 2 * Net (polyhedron) In geometry, a net of a polyhedron is an arran ...

net
aerodynamic study at Wallops Flight Facility, Wallops Island in 1990. A vortex is created by passage of an aircraft wing, revealed by smoke. Vortices are one of the many phenomena associated with the study of aerodynamics. Aerodynamics, from Greek language, ...
or
hydrodynamic In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through ...
force In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space and time, and the related entities of energy and force ...

force
acting opposite to the direction of the movement."What is Drag?"
''NASA.'' Retrieved: May 6, 2012.
Therefore, drag opposes the motion of the object, and in a powered vehicle it must be overcome by
thrust Thrust is a reaction (physics), reaction force (physics), force described quantitatively by Newton's third law. When a system expels or acceleration, accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude ...

thrust
. The process which creates lift also causes some drag.


Lift-to-drag ratio

Aerodynamic lift is created by the motion of an aerodynamic object (wing) through the air, which due to its shape and angle deflects the air. For sustained straight and level flight, lift must be equal and opposite to weight. In general, long narrow wings are able deflect a large amount of air at a slow speed, whereas smaller wings need a higher forward speed to deflect an equivalent amount of air and thus generate an equivalent amount of lift. Large cargo aircraft tend to use longer wings with higher angles of attack, whereas supersonic aircraft tend to have short wings and rely heavily on high forward speed to generate lift. However, this lift (deflection) process inevitably causes a retarding force called drag. Because lift and drag are both aerodynamic forces, the ratio of lift to drag is an indication of the aerodynamic efficiency of the airplane. The lift to drag ratio is the L/D ratio, pronounced "L over D ratio." An airplane has a high L/D ratio if it produces a large amount of lift or a small amount of drag. The lift/drag ratio is determined by dividing the lift coefficient by the drag coefficient, CL/CD. The lift coefficient Cl is equal to the lift L divided by the (density r times half the velocity V squared times the wing area A). l = L / (A * .5 * r * V^2)The lift coefficient is also affected by the compressibility of the air, which is much greater at higher speeds, so velocity V is not a linear function. Compressibility is also affected by the shape of the aircraft surfaces. The drag coefficient Cd is equal to the drag D divided by the (density r times half the velocity V squared times the reference area A). [Cd = D / (A * .5 * r * V^2)] Lift-to-drag ratios for practical aircraft vary from about 4:1 for vehicles and birds with relatively short wings, up to 60:1 or more for vehicles with very long wings, such as gliders. A greater angle of attack relative to the forward movement also increases the extent of deflection, and thus generates extra lift. However a greater angle of attack also generates extra drag. Lift/drag ratio also determines the glide ratio and gliding range. Since the glide ratio is based only on the relationship of the aerodynamics forces acting on the aircraft, aircraft weight will not affect it. The only effect weight has is to vary the time that the aircraft will glide for – a heavier aircraft gliding at a higher airspeed will arrive at the same touchdown point in a shorter time.


Buoyancy

Air pressure acting up against an object in air is greater than the pressure above pushing down. The buoyancy, in both cases, is equal to the weight of fluid displaced - Archimedes' principle holds for air just as it does for water. A cubic meter of air at ordinary atmospheric pressure and room temperature has a mass of about 1.2 kilograms, so its weight is about 12 Newton (unit), newtons. Therefore, any 1-cubic-meter object in air is buoyed up with a force of 12 newtons. If the mass of the 1-cubic-meter object is greater than 1.2 kilograms (so that its weight is greater than 12 newtons), it falls to the ground when released. If an object of this size has a mass less than 1.2 kilograms, it rises in the air. Any object that has a mass that is less than the mass of an equal volume of air will rise in air - in other words, any object less dense than air will rise.


Thrust to weight ratio

Thrust-to-weight ratio is, as its name suggests, the ratio of instantaneous
thrust Thrust is a reaction (physics), reaction force (physics), force described quantitatively by Newton's third law. When a system expels or acceleration, accelerates mass in one direction, the accelerated mass will cause a force of equal magnitude ...

thrust
to
weight In science and engineering, the weight of an object is the force acting on the object due to gravity. Some standard textbooks define weight as a Euclidean vector, vector quantity, the gravitational force acting on the object. Others define weight ...

weight
(where weight means weight at the Earth's standard acceleration g_0).Sutton and Biblarz 2000, p. 442. Quote: "thrust-to-weight ratio F/W0 is a dimensionless parameter that is identical to the acceleration of the rocket propulsion system (expressed in multiples of g0) if it could fly by itself in a gravity free vacuum." It is a dimensionless parameter characteristic of
rocket A rocket (from it, rocchetto, , bobbin/spool) is a projectile that spacecraft, aircraft 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 ...

rocket
s and other jet engines and of vehicles propelled by such engines (typically space launch vehicles and jet
aircraft An aircraft is a vehicle or machine that is able to fly Flies are insect Insects or Insecta (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Lat ...
). If the thrust-to-weight ratio is greater than the local gravity strength (expressed in ''g''s), then flight can occur without any forward motion or any aerodynamic lift being required. If the thrust-to-weight ratio times the lift-to-drag ratio is greater than local gravity then takeoff using aerodynamic lift is possible.


Flight dynamics

Flight dynamics is the science of aircraft, air and spacecraft, space vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are the angles of rotation in three dimensions about the vehicle's center of mass, known as ''pitch'', ''roll'' and ''yaw'' (See Tait-Bryan rotations for an explanation). The control of these dimensions can involve a horizontal stabilizer (i.e. "a tail"), ailerons and other movable aerodynamic devices which control angular stability i.e. flight attitude (which in turn affects altitude, Aircraft heading, heading). Wings are often angled slightly upwards- they have "positive Dihedral (aircraft), dihedral angle" which gives inherent roll stabilization.


Energy efficiency

To create thrust so as to be able to gain height, and to push through the air to overcome the drag associated with lift all takes energy. Different objects and creatures capable of flight vary in the efficiency of their muscles, motors and how well this translates into forward thrust. Propulsive efficiency determines how much energy vehicles generate from a unit of fuel.


Range

The range that powered flight articles can achieve is ultimately limited by their drag, as well as how much energy they can store on board and how efficiently they can turn that energy into propulsion. For powered aircraft the useful energy is determined by their fuel fraction- what percentage of the takeoff weight is fuel, as well as the specific energy of the fuel used.


Power-to-weight ratio

All animals and devices capable of sustained flight need relatively high power-to-weight ratios to be able to generate enough lift and/or thrust to achieve take off.


Takeoff and landing

Vehicles that can fly can have different ways to takeoff and land. Conventional aircraft accelerate along the ground until sufficient lift is generated for takeoff, and reverse the process for landing. Some aircraft can take off at low speed; this is called a short takeoff. Some aircraft such as helicopters and Harrier jump jets can take off and land vertically. Rockets also usually take off and land vertically, but some designs can land horizontally.


Guidance, navigation and control


Navigation

Navigation is the systems necessary to calculate current position (e.g. compass, GPS, LORAN, star tracker, inertial measurement unit, and altimeter). In aircraft, successful air navigation involves piloting an aircraft from place to place without getting lost, breaking the laws applying to aircraft, or endangering the safety of those on board or on the Earth, ground. The techniques used for navigation in the air will depend on whether the aircraft is flying under the visual flight rules (VFR) or the instrument flight rules (IFR). In the latter case, the aviator, pilot will navigate exclusively using flight instruments, instruments and radio navigation aids such as beacons, or as directed under radar control by air traffic control. In the VFR case, a pilot will largely navigate using dead reckoning combined with visual observations (known as pilotage), with reference to appropriate maps. This may be supplemented using radio navigation aids.


Guidance

A guidance system is a device or group of devices used in the navigation of a ship,
aircraft An aircraft is a vehicle or machine that is able to fly Flies are insect Insects or Insecta (from Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Lat ...
, missile,
rocket A rocket (from it, rocchetto, , bobbin/spool) is a projectile that spacecraft, aircraft 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 ...

rocket
, satellite, or other moving object. Typically, guidance is responsible for the calculation of the vector (i.e., direction, velocity) toward an objective.


Control

A conventional fixed-wing aircraft flight control system consists of flight control surfaces, the respective cockpit controls, connecting linkages, and the necessary operating mechanisms to control an aircraft's direction in flight. Aircraft engine controls are also considered as flight controls as they change speed.


Traffic

In the case of aircraft, air traffic is controlled by air traffic control systems. Collision avoidance (spacecraft), Collision avoidance is the process of controlling spacecraft to try to prevent collisions.


Flight safety

Air safety is a term encompassing the theory, investigation and categorization of Aviation accidents and incidents, flight failures, and the prevention of such failures through regulation, education and training. It can also be applied in the context of campaigns that inform the public as to the safety of air travel.


See also

* Aerodynamics * Levitation * Transvection (flying)


References

;Notes ;Bibliography * Coulson-Thomas, Colin. ''The Oxford Illustrated Dictionary.'' Oxford, UK: Oxford University Press, 1976, First edition 1975, . * French, A. P. ''Newtonian Mechanics'' (The M.I.T. Introductory Physics Series) (1st ed.). New York: W. W. Norton & Company Inc., 1970. * Honicke, K., R. Lindner, P. Anders, M. Krahl, H. Hadrich and K. Rohricht. ''Beschreibung der Konstruktion der Triebwerksanlagen.'' Berlin: Interflug, 1968. * Sutton, George P. Oscar Biblarz. ''Rocket Propulsion Elements.'' New York: Wiley-Interscience, 2000 (7th edition). . * Walker, Peter. ''Chambers Dictionary, Chambers Dictionary of Science and Technology.'' Edinburgh: Chambers Harrap Publishers Ltd., 2000, First edition 1998. .


External links

* History and photographs of early aeroplanes etc.
'Birds in Flight and Aeroplanes' by Evolutionary Biologist and trained Engineer John Maynard-Smith
Freeview video provided by the Vega Science Trust. {{Authority control Flight, Aerodynamics Sky