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drag equation | Space and Astronomy | 1 | In fluid dynamics , the drag equation is a formula used to calculate the force of drag experienced by an object due to movement through a fully enclosing fluid . The equation is |
drop test | Space and Astronomy | 1 | is a method of testing the in-flight characteristics of prototype or experimental aircraft and spacecraft by raising the test vehicle to a specific altitude and then releasing it. Test flights involving powered aircraft, particularly rocket-powered aircraft , may be referred to as drop launches due to the launch of the aircraft's rockets after release from its carrier aircraft. |
dual mode propulsion rocket | Space and Astronomy | 1 | Dual mode propulsion systems combine the high efficiency of bipropellant rockets with the reliability and simplicity of monopropellant rockets . It is based upon the use of two rocket fuels , liquid hydrogen and more dense hydrocarbon fuels, like RP, which are all burned with liquid oxygen . |
ductility | Space and Astronomy | 1 | is a measure of a material's ability to undergo significant plastic deformation before rupture, which may be expressed as percent elongation or percent area reduction from a tensile test. |
earth's atmosphere | Space and Astronomy | 1 | The atmosphere of Earth is the layer of gases , commonly known as air , that surrounds the planet Earth and is retained by Earth's gravity . The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface , absorbing ultraviolet solar radiation , warming the surface through heat retention ( greenhouse effect ), and reducing temperature extremes between day and night (the diurnal temperature variation ). |
eccentric anomaly | Space and Astronomy | 1 | In orbital mechanics , the eccentric anomaly is an angular parameter that defines the position of a body that is moving along an elliptic Kepler orbit . The eccentric anomaly is one of three angular parameters ("anomalies") that define a position along an orbit, the other two being the true anomaly and the mean anomaly . |
eccentricity vector | Space and Astronomy | 1 | In celestial mechanics , the eccentricity vector of a Kepler orbit is the dimensionless vector with direction pointing from apoapsis to periapsis and with magnitude equal to the orbit's scalar eccentricity . For Kepler orbits the eccentricity vector is a constant of motion. Its main use is in the analysis of almost circular orbits, as perturbing (non-Keplerian) forces on an actual orbit will cause the osculating eccentricity vector to change continuously. For the eccentricity and argument of periapsis parameters, eccentricity zero (circular orbit) corresponds to a singularity. The magnitude of the eccentricity vector represents the eccentricity of the orbit. Note that the velocity and position vectors need to be relative to the inertial frame of the central body. |
eigenvector slew | Space and Astronomy | 1 | In aerospace engineering, especially those areas dealing with spacecraft , the eigenvector slew is a method to calculate a steering correction (called a slew ) by rotating the spacecraft around one fixed axis, or a gimbal . This corresponds in general to the fastest and most efficient way to reach the desired target orientation as there is only one acceleration phase and one braking phase for the angular rate. If this fixed axis is not a principal axis a time varying torque must be applied to force the spacecraft to rotate as desired, though. Also the gyroscopic effect of momentum wheels must be compensated for. |
electrostatic ion thruster | Space and Astronomy | 1 | is a form of electric propulsion used for spacecraft propulsion . It creates thrust by accelerating ions using electricity . |
elevator | Space and Astronomy | 1 | is a flight control surface , usually at the rear of an aircraft , which control the aircraft's pitch , and therefore the angle of attack and the lift of the wing. The elevators are usually hinged to the tailplane or horizontal stabilizer . |
empennage | Space and Astronomy | 1 | The empennage ( / ˌ ɑː m p ɪ ˈ n ɑː ʒ / or / ˈ ɛ m p ɪ n ɪ dʒ / ), also known as the tail or tail assembly , is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an arrow . The term derives from the French language verb empenner which means " to feather an arrow". Most aircraft feature an empennage incorporating vertical and horizontal stabilising surfaces which stabilise the flight dynamics of yaw and pitch , as well as housing control surfaces . |
enstrophy | Space and Astronomy | 1 | In fluid dynamics , the enstrophy E can be interpreted as another type of potential density ; or, more concretely, the quantity directly related to the kinetic energy in the flow model that corresponds to dissipation effects in the fluid. It is particularly useful in the study of turbulent flows , and is often identified in the study of thrusters as well as the field of combustion theory. |
equations of motion | Space and Astronomy | 1 | In physics , equations of motion are equations that describe the behavior of a physical system in terms of its motion as a function of time. More specifically, the equations of motion describe the behavior of a physical system as a set of mathematical functions in terms of dynamic variables. These variables are usually spatial coordinates and time, but may include momentum components. The most general choice are generalized coordinates which can be any convenient variables characteristic of the physical system. The functions are defined in a Euclidean space in classical mechanics , but are replaced by curved spaces in relativity . If the dynamics of a system is known, the equations are the solutions for the differential equations describing the motion of the dynamics. |
esa | Space and Astronomy | 1 | European Space Agency |
et | Space and Astronomy | 1 | (Space Shuttle) external tank |
euler angles | Space and Astronomy | 1 | are three angles introduced by Leonhard Euler to describe the orientation of a rigid body with respect to a fixed coordinate system . They can also represent the orientation of a mobile frame of reference in physics or the orientation of a general basis in 3-dimensional linear algebra. Alternative forms were later introduced by Peter Guthrie Tait and George H. Bryan intended for use in aeronautics and engineering. |
expander cycle | Space and Astronomy | 1 | is a power cycle of a bipropellant rocket engine . In this cycle, the fuel is used to cool the engine's combustion chamber, picking up heat and changing phase. The now heated and gaseous fuel then powers the turbine that drives the engine's fuel and oxidizer pumps before being injected into the combustion chamber and burned for thrust. |
rocket | Space and Astronomy | 1 | is a power cycle of a pumped liquid bipropellant rocket engine . Part of the unburned propellant is burned in a gas generator (or preburner) and the resulting hot gas is used to power the propellant pumps before being exhausted overboard, and lost. Because of this loss, this type of engine is termed open cycle . |
fatigue | Space and Astronomy | 1 | In materials science , fatigue is the weakening of a material caused by repeatedly applied loads. It is the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The nominal maximum stress values that cause such damage may be much less than the strength of the material typically quoted as the ultimate tensile stress limit , or the yield stress limit . |
field-emission electric propulsion | Space and Astronomy | 1 | (FEEP), is an advanced electrostatic space propulsion concept, a form of ion thruster , that uses a liquid metal as a propellant – usually either caesium , indium , or mercury . |
fixed-wing aircraft | Space and Astronomy | 1 | is a heavier-than-air flying machine , such as an airplane , which is capable of flight using wings that generate lift caused by the aircraft's forward airspeed and the shape of the wings . are distinct from rotary-wing aircraft (in which the wings form a rotor mounted on a spinning shaft or "mast"), and ornithopters (in which the wings flap in a manner similar to that of a bird ). The wings of a fixed-wing aircraft are not necessarily rigid; kites, hang gliders , variable-sweep wing aircraft and airplanes that use wing morphing are all examples of fixed-wing aircraft. |
flap | Space and Astronomy | 1 | is a high-lift device used to reduce the stalling speed of an aircraft wing at a given weight. s are usually mounted on the wing trailing edges of a fixed-wing aircraft . s are used to reduce the take-off distance and the landing distance. s also cause an increase in drag so they are retracted when not needed. |
flight control surfaces | Space and Astronomy | 1 | are aerodynamic devices allowing a pilot to adjust and control the aircraft's flight attitude . |
flight control system | Space and Astronomy | 1 | A helicopter pilot manipulates the helicopter flight controls to achieve and maintain controlled aerodynamic flight . Changes to the aircraft flight control system transmit mechanically to the rotor, producing aerodynamic effects on the rotor blades that make the helicopter move in a deliberate way. To tilt forward and back (pitch) or sideways (roll) requires that the controls alter the angle of attack of the main rotor blades cyclically during rotation, creating differing amounts of lift (force) at different points in the cycle. To increase or decrease overall lift requires that the controls alter the angle of attack for all blades collectively by equal amounts at the same time, resulting in ascent, descent, acceleration and deceleration. |
aircraft | Space and Astronomy | 1 | 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. |
helicopter | Space and Astronomy | 1 | A helicopter pilot manipulates the helicopter flight controls to achieve and maintain controlled aerodynamic flight . Changes to the aircraft flight control system transmit mechanically to the rotor, producing aerodynamic effects on the rotor blades that make the helicopter move in a deliberate way. To tilt forward and back (pitch) or sideways (roll) requires that the controls alter the angle of attack of the main rotor blades cyclically during rotation, creating differing amounts of lift (force) at different points in the cycle. To increase or decrease overall lift requires that the controls alter the angle of attack for all blades collectively by equal amounts at the same time, resulting in ascent, descent, acceleration and deceleration. |
flight dynamics | Space and Astronomy | 1 | is the study of the performance, stability, and control of vehicles flying through the air or in outer space . It is concerned with how forces acting on the vehicle determine its velocity and attitude with respect to time. For a fixed-wing aircraft , its changing orientation with respect to the local air flow is represented by two critical angles, the angle of attack of the wing ("alpha") and the angle of attack of the vertical tail, known as the sideslip angle ("beta"). A sideslip angle will arise if an aircraft yaws about its centre of gravity and if the aircraft sideslips bodily, i.e. the centre of gravity moves sideways. These angles are important because they are the principal source of changes in the aerodynamic forces and moments applied to the aircraft. Spacecraft flight dynamics involve three main forces: propulsive (rocket engine), gravitational, and atmospheric resistance. Propulsive force and atmospheric resistance have significantly less influence over a given spacecraft compared to gravitational forces. |
flight management system | Space and Astronomy | 1 | A flight management system (FMS) is a fundamental component of a modern airliner's avionics . An FMS is a specialized computer system that automates a wide variety of in-flight tasks, reducing the workload on the flight crew to the point that modern civilian aircraft no longer carry flight engineers or navigators . A primary function is in-flight management of the flight plan. Using various sensors (such as GPS and INS often backed up by radio navigation ) to determine the aircraft's position, the FMS can guide the aircraft along the flight plan. From the cockpit, the FMS is normally controlled through a Control Display Unit (CDU) which incorporates a small screen and keyboard or touchscreen. The FMS sends the flight plan for display to the Electronic Flight Instrument System (EFIS), Navigation Display (ND), or Multifunction Display (MFD). The FMS can be summarised as being a dual system consisting of the Flight Management Computer (FMC) , CDU and a cross talk bus. |
floatstick | Space and Astronomy | 1 | is a device to measure fuel levels in modern large aircraft . It consists of a closed tube rising from the bottom of the fuel tank. Surrounding the tube is a ring-shaped float, and inside it is a graduated rod indicating fuel capacity. The float and the top of the rod contain magnets . The rod is withdrawn from the bottom of the wing until the magnets stick, the distance it is withdrawn indicating the level of the fuel. When not in use, the stick is secured within the tube. |
fluid | Space and Astronomy | 1 | In physics , a fluid is a liquid , gas , or other material that continuously deforms (flows) under an applied shear stress , or external force. They have zero shear modulus , or, in simpler terms, are substances which cannot resist any shear force applied to them. |
fluid dynamics | Space and Astronomy | 1 | In physics and engineering , fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids — liquids and gases . It has several subdisciplines, including aerodynamics (the study of air and other gases in motion) and hydrodynamics (the study of liquids in motion). has a wide range of applications, including calculating forces and moments on aircraft , determining the mass flow rate of petroleum through pipelines , predicting weather patterns , and understanding nebulae in interstellar space . |
fluid mechanics | Space and Astronomy | 1 | is the branch of physics concerned with the mechanics of fluids ( liquids , gases , and plasmas ) and the forces on them. It has applications in a wide range of disciplines, including mechanical , civil , chemical and biomedical engineering , geophysics , oceanography , meteorology , astrophysics , and biology . It can be divided into fluid statics , the study of fluids at rest; and fluid dynamics , the study of the effect of forces on fluid motion. |
fluid statics | Space and Astronomy | 1 | or hydrostatics , is the branch of fluid mechanics that studies the condition of the equilibrium of a floating body and submerged body " fluids at hydrostatic equilibrium and the pressure in a fluid, or exerted by a fluid, on an immersed body". |
fms | Space and Astronomy | 1 | Flight management system. |
force | Space and Astronomy | 1 | In physics , a force is any influence that, when unopposed, will change the motion of an object . A force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest ), i.e., to accelerate . can also be described intuitively as a push or a pull. A force has both magnitude and direction , making it a vector quantity. It is measured in the SI unit of newton (N) . is represented by the symbol F (formerly P ). |
freefall | Space and Astronomy | 1 | In Newtonian physics , free fall is any motion of a body where gravity is the only force acting upon it. In the context of general relativity , where gravitation is reduced to a space-time curvature , a body in free fall has no force acting on it. An object in the technical sense of the term "free fall" may not necessarily be falling down in the usual sense of the term. An object moving upwards might not normally be considered to be falling, but if it is subject to only the force of gravity, it is said to be in free fall. The Moon is thus in free fall around the Earth , though its orbital speed keeps it in very far orbit from the Earth's surface . In a roughly uniform gravitational field , in the absence of any other forces, gravitation acts on each part of the body roughly equally. When there is no normal force exerted between a body (e.g. an astronaut in orbit) and its surrounding objects, it will result in the sensation of weightlessness , a condition that also occurs when the gravitational field is weak (such as when far away from any source of gravity). |
fuselage | Space and Astronomy | 1 | In aeronautics , the fuselage ( / ˈ f juː z əl ɑː ʒ / ; 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. |
future air navigation system | Space and Astronomy | 1 | (FANS), is an avionics system which provides direct data link communication between the pilot and the air traffic controller . The communications include air traffic control clearances, pilot requests and position reporting. |
flying wing | Space and Astronomy | 1 | is a tailless fixed-wing aircraft that has no definite fuselage , with its crew, payload, fuel, and equipment housed inside the main wing structure. A flying wing may have various small protuberances such as pods, nacelles , blisters, booms, or vertical stabilizers . |
galaxy | Space and Astronomy | 1 | One of the very large groups of stars and other matter that are foundthroughout the universe. |
gas-generator cycle | Space and Astronomy | 1 | is a power cycle of a pumped liquid bipropellant rocket engine . Part of the unburned propellant is burned in a gas generator (or preburner) and the resulting hot gas is used to power the propellant pumps before being exhausted overboard, and lost. Because of this loss, this type of engine is termed open cycle . |
geostationary orbit | Space and Astronomy | 1 | also referred to as a geosynchronous equatorial orbit ( GEO ), is a circular geosynchronous orbit 35,786 kilometres (22,236 miles) in altitude above Earth's equator (42,164 kilometers in radius from Earth's center) and following the direction of Earth's rotation . An object in such an orbit has an orbital period equal to the Earth's rotational period, one sidereal day , and so to ground observers it appears motionless, in a fixed position in the sky. |
geosynchronous orbit | Space and Astronomy | 1 | (sometimes abbreviated GSO) is an Earth-centered orbit with an orbital period that matches Earth's rotation on its axis, 23 hours, 56 minutes, and 4 seconds (one sidereal day ). The synchronization of rotation and orbital period means that, for an observer on Earth's surface, an object in geosynchronous orbit returns to exactly the same position in the sky after a period of one sidereal day. Over the course of a day, the object's position in the sky may remain still or trace out a path, typically in a figure-8 form , whose precise characteristics depend on the orbit's inclination and eccentricity . A circular geosynchronous orbit has a constant altitude of 35,786 km (22,236 mi), and all geosynchronous orbits share that semi-major axis. A special case of geosynchronous orbit is the geostationary orbit , which is a circular geosynchronous orbit in Earth's equatorial plane . A satellite in a geostationary orbit remains in the same position in the sky to observers on the surface. |
glide ratio | Space and Astronomy | 1 | As the aircraft fuselage and control surfaces will also add drag and possibly some lift, it is fair to consider the lift-to-drag ratio (or L/D ratio) of the aircraft as a whole. As it turns out, the glide ratio , which is the ratio of an (unpowered) aircraft's forward motion to its descent, is (when flown at constant speed) numerically equal to the aircraft's L/D. This is especially of interest in the design and operation of high performance sailplanes , which can have glide ratios almost 60 to 1 (60 units of distance forward for each unit of descent) in the best cases, but with 30:1 being considered good performance for general recreational use. Achieving a glider's best L/D in practice requires precise control of airspeed and smooth and restrained operation of the controls to reduce drag from deflected control surfaces. In zero wind conditions, L/D will equal distance traveled divided by altitude lost. Achieving the maximum distance for altitude lost in wind conditions requires further modification of the best airspeed, as does alternating cruising and thermaling. To achieve high speed across country, glider pilots anticipating strong thermals often load their gliders (sailplanes) with water ballast : the increased wing loading means optimum glide ratio at greater airspeed, but at the cost of climbing more slowly in thermals. The maximum L/D is not dependent on weight or wing loading, but with greater wing loading the maximum L/D occurs at a faster airspeed. Also, the faster airspeed means the aircraft will fly at greater Reynolds number and this will usually bring about a lower zero-lift drag coefficient . |
glider | Space and Astronomy | 1 | is a fixed-wing aircraft that is supported in flight by the dynamic reaction of the air against its lifting surfaces, and whose free flight does not depend on an engine. Most gliders do not have an engine, although motor-gliders have small engines for extending their flight when necessary by sustaining the altitude (normally a sailplane relies on rising air to maintain altitude) with some being powerful enough to take off self-launch . |
global positioning system | Space and Astronomy | 1 | (GPS), originally Navstar GPS , is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force . It is one of the global navigation satellite systems (GNSS) that provides geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. Obstacles such as mountains and buildings can block the relatively weak GPS signals . |
goddard problem | Space and Astronomy | 1 | In rocketry , the is to optimize the peak altitude of a rocket, ascending vertically, and taking into account atmospheric drag and the gravitational field . This was first posed by Robert H. Goddard in his 1919 publication, "A Method of Reaching Extreme Altitudes". |
gps | Space and Astronomy | 1 | Global Positioning System |
gravitational constant | Space and Astronomy | 1 | The gravitational constant (also known as the universal gravitational constant , the Newtonian constant of gravitation , or the Cavendish gravitational constant ), denoted by the letter G , is an empirical physical constant involved in the calculation of gravitational effects in Sir Isaac Newton 's law of universal gravitation and in Albert Einstein 's general theory of relativity . In Newton's law, it is the proportionality constant connecting the gravitational force between two bodies with the product of their masses and the inverse square of their distance . In the Einstein field equations , it quantifies the relation between the geometry of spacetime and the energy–momentum tensor (also referred to as the stress–energy tensor ). The measured value of the constant is known with some certainty to four significant digits. In SI units , its value is approximately 6.674 × 10 −11 m 3 ⋅kg −1 ⋅s −2 . The modern notation of Newton's law involving G was introduced in the 1890s by C. V. Boys . The first implicit measurement with an accuracy within about 1% is attributed to Henry Cavendish in a 1798 experiment . |
gravitational slingshot | Space and Astronomy | 1 | In orbital mechanics and aerospace engineering , a gravitational slingshot , gravity assist maneuver , or swing-by is the use of the relative movement (e.g. orbit around the Sun ) and gravity of a planet or other astronomical object to alter the path and speed of a spacecraft , typically to save propellant and reduce expense. Gravity assistance can be used to accelerate a spacecraft, that is, to increase or decrease its speed or redirect its path. The "assist" is provided by the motion of the gravitating body as it pulls on the spacecraft. |
gravity | Space and Astronomy | 1 | (from Latin gravitas ' weight ' ), or gravitation , is a natural phenomenon by which all things with mass or energy —including planets , stars , galaxies , and even light —are attracted to (or gravitate toward) one another. On Earth , gravity gives weight to physical objects , and the Moon's gravity causes the tides of the oceans. The gravitational attraction of the original gaseous matter present in the Universe caused it to begin coalescing and forming stars and caused the stars to group together into galaxies, so gravity is responsible for many of the large-scale structures in the Universe. has an infinite range, although its effects become weaker as objects get further away. |
hall effect thruster | Space and Astronomy | 1 | In spacecraft propulsion , a Hall-effect thruster (HET) is a type of ion thruster in which the propellant is accelerated by an electric field . Hall-effect thrusters (based on the discovery by Edwin Hall ) are sometimes referred to as Hall thrusters or Hall-current thrusters . Hall-effect thrusters use a magnetic field to limit the electrons' axial motion and then use them to ionize propellant, efficiently accelerate the ions to produce thrust , and neutralize the ions in the plume. The Hall-effect thruster is classed as a moderate specific impulse (1,600 s) space propulsion technology and has benefited from considerable theoretical and experimental research since the 1960s. |
heat shield | Space and Astronomy | 1 | A heat shield is designed to protect an object from overheating by dissipating, reflecting, absorbing heat, or simply gradually burn and fall away from the aircraft, pulling the excess heat with it. The term is most often used in reference to exhaust heat management and to systems for dissipation of heat due to friction. |
helicopter | Space and Astronomy | 1 | 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 allow helicopters to be used in congested or isolated areas where fixed-wing aircraft and many forms of VTOL (Vertical TakeOff and Landing) aircraft cannot perform. |
hohmann transfer orbit | Space and Astronomy | 1 | In orbital mechanics , the ( / ˈ h oʊ m ə n / ) is an elliptical orbit used to transfer between two circular orbits of different radii around a central body in the same plane . The Hohmann transfer often uses the lowest possible amount of propellant in traveling between these orbits, but bi-elliptic transfers can use less in some cases. |
hybrid rocket | Space and Astronomy | 1 | A hybrid-propellant rocket is a rocket with a rocket motor that uses rocket propellants in two different phases: one solid and the other either gas or liquid . The hybrid rocket concept can be traced back to at least the 1930s. |
hydrodynamics | Space and Astronomy | 1 | In physics and engineering , fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids — liquids and gases . It has several subdisciplines, including aerodynamics (the study of air and other gases in motion) and hydrodynamics (the study of liquids in motion). Fluid dynamics has a wide range of applications, including calculating forces and moments on aircraft , determining the mass flow rate of petroleum through pipelines , predicting weather patterns , understanding nebulae in interstellar space and modelling fission weapon detonation . |
hydrostatics | Space and Astronomy | 1 | Fluid statics or hydrostatics is the branch of fluid mechanics that studies the condition of the equilibrium of a floating body and submerged body " fluids at hydrostatic equilibrium and the pressure in a fluid, or exerted by a fluid, on an immersed body". It encompasses the study of the conditions under which fluids are at rest in stable equilibrium as opposed to fluid dynamics , the study of fluids in motion. is a subcategory of fluid statics, which is the study of all fluids, both compressible or incompressible, at rest. |
hyperbolic partial differential equation | Space and Astronomy | 1 | In mathematics , a hyperbolic partial differential equation of order n n} is a partial differential equation (PDE) that, roughly speaking, has a well-posed initial value problem for the first n − 1 n-1} derivatives. More precisely, the Cauchy problem can be locally solved for arbitrary initial data along any non-characteristic hypersurface . Many of the equations of mechanics are hyperbolic, and so the study of hyperbolic equations is of substantial contemporary interest. The model hyperbolic equation is the wave equation . In one spatial dimension, this is |
hypersonic speed | Space and Astronomy | 1 | In aerodynamics , a hypersonic speed is one that greatly exceeds the speed of sound , often stated as starting at speeds of Mach 5 and above. The precise Mach number at which a craft can be said to be flying at hypersonic speed varies, since individual physical changes in the airflow (like molecular dissociation and ionization ) occur at different speeds; these effects collectively become important around Mach 5–10. The hypersonic regime can also be alternatively defined as speeds where specific heat capacity changes with the temperature of the flow as kinetic energy of the moving object is converted into heat. |
hypoxia | Space and Astronomy | 1 | is a condition in which the body or a region of the body is deprived of adequate oxygen supply at the tissue level. may be classified as either generalized , affecting the whole body, or local , affecting a region of the body. Although hypoxia is often a pathological condition, variations in arterial oxygen concentrations can be part of the normal physiology, for example, during hypoventilation training or strenuous physical exercise. |
impulse | Space and Astronomy | 1 | Specific impulse (usually abbreviated I sp ) is a measure of how efficiently a rocket uses propellant or a jet engine uses fuel. For engines whose reaction mass is only the fuel they carry, specific impulse is exactly proportional to exhaust gas velocity. |
indicated airspeed | Space and Astronomy | 1 | (IAS), is the airspeed read directly from the airspeed indicator (ASI) on an aircraft, driven by the pitot-static system . It uses the difference between total pressure and static pressure, provided by the system, to either mechanically or electronically measure dynamic pressure . The dynamic pressure includes terms for both density and airspeed. Since the airspeed indicator cannot know the density, it is by design calibrated to assume the sea level standard atmospheric density when calculating airspeed. Since the actual density will vary considerably from this assumed value as the aircraft changes altitude, IAS varies considerably from true airspeed (TAS), the relative velocity between the aircraft and the surrounding air mass. Calibrated airspeed (CAS) is the IAS corrected for instrument and position error . An aircraft's indicated airspeed in knots is typically abbreviated KIAS for " Knots -Indicated Air Speed" (vs. KCAS for calibrated airspeed and KTAS for true airspeed ). |
instrument landing system | Space and Astronomy | 1 | In aviation , the instrument landing system (ILS) is a radio navigation system that provides short-range guidance to aircraft to allow them to approach a runway at night or in bad weather. In its original form, it allows an aircraft to approach until it is 200 feet (61 m) over the ground, within a 1 ⁄ 2 mile (800 m) of the runway. At that point the runway should be visible to the pilot; if it is not, they perform a missed approach . Bringing the aircraft this close to the runway dramatically improves the weather conditions in which a safe landing can be made. Later versions of the system, or "categories", have further reduced the minimum altitudes. |
interplanetary transport network | Space and Astronomy | 1 | (ITN) is a collection of gravitationally determined pathways through the Solar System that require very little energy for an object to follow. The ITN makes particular use of Lagrange points as locations where trajectories through space can be redirected using little or no energy. These points have the peculiar property of allowing objects to orbit around them, despite lacking an object to orbit. While it would use little energy, transport along the network would take a long time. |
interplanetary travel | Space and Astronomy | 1 | Interplanetary spaceflight or interplanetary travel is the crewed or uncrewed travel between stars and planets , usually within a single planetary system . |
interstellar travel | Space and Astronomy | 1 | refers to the currently theoretical idea of interstellar probes or crewed spacecraft moving between stars or planetary systems in a galaxy. would be much more difficult than interplanetary spaceflight . Whereas the distances between the planets in the Solar System are less than 30 astronomical units (AU), the distances between stars are typically hundreds of thousands of AU, and usually expressed in light-years . Because of the vastness of those distances, practical interstellar travel based on known physics would need to occur at a high percentage of the speed of light ; even so, travel times would be long, at least decades and perhaps millennia or longer. |
ion thruster | Space and Astronomy | 1 | An ion thruster, ion drive , or ion engine is a form of electric propulsion used for spacecraft propulsion . It creates thrust by accelerating ions using electricity . |
isro | Space and Astronomy | 1 | The Indian Space Research Organisation ( / ˈ ɪ s r oʊ / ) or ( IAST : Bhāratīya Antrikṣ Anusandhān Saṅgaṭhan ) is the national space agency of India , headquartered in Bengaluru . It operates under the Department of Space (DOS) which is directly overseen by the Prime Minister of India , while Chairman of acts as executive of DOS as well. is the primary agency in India to perform tasks related to space based applications, space exploration and development of related technologies. It is one of six government space agencies in the world which possess full launch capabilities, deploy cryogenic engines , launch extraterrestrial missions and operate large fleets of artificial satellites. |
jet engine | Space and Astronomy | 1 | is a type of reaction engine discharging a fast-moving jet that generates thrust by jet propulsion . |
keel effect | Space and Astronomy | 1 | In aeronautics , the keel effect (also known as the pendulum effect or pendulum stability ) is the result of the sideforce-generating surfaces being above (or below) the center of mass (which coincides with the center of gravity ) in an aircraft. Along with dihedral , sweepback , and weight distribution , keel effect is one of the four main design considerations in aircraft lateral stability . |
kepler's laws of planetary motion | Space and Astronomy | 1 | In astronomy , , published by Johannes Kepler between 1609 and 1619, describe the orbits of planets around the Sun . The laws modified the heliocentric theory of Nicolaus Copernicus , replacing its circular orbits and epicycles with elliptical trajectories, and explaining how planetary velocities vary. The three laws state that |
kessler syndrome | Space and Astronomy | 1 | (also called the Kessler effect , collisional cascading , or ablation cascade ), proposed by NASA scientist Donald J. Kessler in 1978, is a theoretical 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. 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. |
kinetic energy | Space and Astronomy | 1 | 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. In classical mechanics , the kinetic energy of a non-rotating object of mass m traveling at a speed v is 1 2 m v 2 {\textstyle {\frac {1}{2}}mv^{2}} . In relativistic mechanics , this is a good approximation only when v is much less than the speed of light . |
kite | Space and Astronomy | 1 | is a tethered heavier-than-air or lighter-than-air craft with wing surfaces that react against the air to create lift and drag forces. A kite consists of wings, tethers and anchors. s often have a bridle and tail to guide the face of the kite so the wind can lift it. Some kite designs don't need a bridle; box kites can have a single attachment point. A kite may have fixed or moving anchors that can balance the kite. One technical definition is that a kite is “a collection of tether-coupled wing sets“. The name derives from its resemblance to a hovering bird . |
kutta condition | Space and Astronomy | 1 | is a principle in steady-flow fluid dynamics , especially aerodynamics , that is applicable to solid bodies with sharp corners, such as the trailing edges of airfoils . It is named for German mathematician and aerodynamicist Martin Kutta . |
kutta–joukowski theorem | Space and Astronomy | 1 | is a fundamental theorem in aerodynamics used for the calculation of lift of an airfoil and any two-dimensional bodies including circular cylinders translating into a uniform fluid at a constant speed large enough so that the flow seen in the body-fixed frame is steady and unseparated. The theorem relates the lift generated by an airfoil to the speed of the airfoil through the fluid, the density of the fluid and the circulation around the airfoil. The circulation is defined as the line integral around a closed-loop enclosing the airfoil of the component of the velocity of the fluid tangent to the loop. It is named after Martin Kutta and Nikolai Zhukovsky (or Joukowski) who first developed its key ideas in the early 20th century. is an inviscid theory , but it is a good approximation for real viscous flow in typical aerodynamic applications. |
lander | Space and Astronomy | 1 | spacecraft designed to soft-land intact or almost undamaged on the surface of a celestial body and eventually take-off from it |
landing | Space and Astronomy | 1 | is the last part of a flight , where an aircraft , or spacecraft returns to the ground. When the flying object returns to water, the process is called alighting , although it is commonly called "landing", "touchdown" a or " splashdown " as well. A normal aircraft flight would include several parts of flight including taxi , takeoff , climb , cruise , descent and landing. |
landing gear | Space and Astronomy | 1 | is the undercarriage of an aircraft or spacecraft and may be used for either takeoff or landing . For aircraft it is generally needed for both. Also, for aircraft, the landing gear supports the craft when it is not flying, allowing it to take off, land, and taxi without damage. Wheeled landing gear is the most common, with skis or floats needed to operate from snow/ice/water and skids for vertical operation on land. Faster aircraft have retractable undercarriages, which fold away during flight to reduce drag . |
lagrangian mechanics | Space and Astronomy | 1 | Introduced by the Italian-French mathematician and astronomer Joseph-Louis Lagrange in 1788, is a formulation of classical mechanics and is founded on the stationary action principle . |
lagrangian point | Space and Astronomy | 1 | Any of a set of points near two large bodies in orbit at which a smaller object will maintain a constant position relative to the larger bodies. At other locations, a small object would eventually be pulled into its own orbit around one of the large bodies, but at the Lagrangian points the gravitational forces of the large bodies, the centripetal force of orbital motion, and (in certain scenarios) the Coriolis acceleration all align in a way that causes the small object to become "locked" in a stable or nearly stable relative position. For each combination of two orbital bodies, there are five such Lagrangian points, typically identified with the labels L1 to L5. The phenomenon is the basis for the stable orbits of trojan satellites and is commonly exploited by man-made satellites. |
laser broom | Space and Astronomy | 1 | is a proposed ground-based laser beam-powered propulsion system whose purpose is to sweep space debris out of the path of other artificial satellites such as the International Space Station . It would heat one side of an object enough to change its orbit and make it hit the atmosphere sooner. Space researchers have proposed that a laser broom may help mitigate Kessler syndrome , a theoretical runaway cascade of collision events between orbiting objects. Space-based laser broom systems using a laser mounted on a satellite or space station have also been proposed. |
laser camera system | Space and Astronomy | 1 | (LCS), is short-range, high precision autosynchronous triangulation scanner. The camera uses a laser to measure the distance between itself and points on a target and is able to create a three-dimensional representation of the area it has scanned. |
latus rectum | Space and Astronomy | 1 | is the chord parallel to the directrix and passing through a focus; its half-length is the semi-latus rectum ( ℓ ). |
launch window | Space and Astronomy | 1 | In the context of spaceflight , launch period is the collection of days and launch window is the time period on a given day during which a particular rocket must be launched in order to reach its intended target. If the rocket is not launched within a given window, it has to wait for the window on the next day of the period. Launch periods and launch windows are very dependent on both the rocket's capability and the orbit to which it is going. |
leading edge | Space and Astronomy | 1 | The leading edge of an airfoil surface such as a wing is its foremost edge and is therefore the part which first meets the oncoming air. |
lift coefficient | Space and Astronomy | 1 | is a dimensionless coefficient that relates the lift generated by a lifting body to the fluid density around the body, the fluid velocity and an associated reference area. A lifting body is a foil or a complete foil-bearing body such as a fixed-wing aircraft . C L is a function of the angle of the body to the flow, its Reynolds number and its Mach number . The lift coefficient c l refers to the dynamic lift characteristics of a two-dimensional foil section, with the reference area replaced by the foil chord . |
lightcraft | Space and Astronomy | 1 | The is a space- or air- vehicle driven by beam-powered propulsion , the energy source powering the craft being external. It was conceptualized by aerospace engineering professor Leik Myrabo at Rensselaer Polytechnic Institute in 1976, who developed the concept further with working prototypes, funded in the 1980s by the Strategic Defense Initiative organization, and the decade after by the Advanced Concept Division of the US Air Force AFRL , NASA 's MFSC and the Lawrence Livermore National Laboratory . |
lighter than air | Space and Astronomy | 1 | 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 to create buoyancy , particularly in lighter-than-air aircraft , which include free balloons , moored balloons , and airships . Only certain lighter than air gases are suitable as lifting gases. Dry air has a density of about 1.29 g/L (gram per liter) at standard conditions for temperature and pressure (STP) and an average molecular mass of 28.97 g/mol , and so lighter than air gases have a density lower than this. |
liquid air cycle engine | Space and Astronomy | 1 | (LACE), is a type of spacecraft propulsion engine that attempts to increase its efficiency by gathering part of its oxidizer from the atmosphere . A liquid air cycle engine uses liquid hydrogen (LH2) fuel to liquefy the air. |
liquid fuel | Space and Astronomy | 1 | s are combustible or energy-generating molecules that can be harnessed to create mechanical energy , usually producing kinetic energy ; they also must take the shape of their container. It is the fumes of liquid fuels that are flammable instead of the fluid. Most liquid fuels in widespread use are derived from fossil fuels ; however, there are several types, such as hydrogen fuel (for automotive uses), ethanol, and biodiesel , which are also categorized as a liquid fuel. Many liquid fuels play a primary role in transportation and the economy. s are contrasted with solid fuels and gaseous fuels . |
liquid-propellant rocket | Space and Astronomy | 1 | or liquid rocket , utilizes a rocket engine that uses liquid propellants . Liquids are desirable because they have a reasonably high density and high specific impulse ( I sp ) . This allows the volume of the propellant tanks to be relatively low. It is also possible to use lightweight centrifugal turbopumps to pump the rocket propellant from the tanks into the combustion chamber, which means that the propellants can be kept under low pressure. This permits the use of low-mass propellant tanks that do not need to resist the high pressures needed to store significant amounts of gases, resulting in a low mass ratio for the rocket. |
liquid rocket propellant | Space and Astronomy | 1 | The highest specific impulse chemical rockets use liquid propellants ( liquid-propellant rockets ). They can consist of a single chemical (a monopropellant ) or a mix of two chemicals, called bipropellants . Bipropellants can further be divided into two categories; hypergolic propellants , which ignite when the fuel and oxidizer make contact, and non-hypergolic propellants which require an ignition source. |
lithobraking | Space and Astronomy | 1 | is a landing technique used by uncrewed space vehicles to safely reach the surface of a celestial body while reducing landing speed by impact with the body's surface. |
loiter | Space and Astronomy | 1 | In aeronautics and aviation , loiter is the phase of flight consisting of flying over some small region. |
low earth orbit | Space and Astronomy | 1 | (LEO), is an Earth-centered orbit close to the planet, often specified as an orbital period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never more than about one-third of the radius of the Earth . |
lunar module | Space and Astronomy | 1 | The Apollo , or simply ( LM / ˈ l ɛ m / ), originally designated the Lunar Excursion Module ( LEM ), was the Lunar lander spacecraft that was flown between lunar orbit and the Moon's surface during the United States' Apollo program . It was the first crewed spacecraft to operate exclusively in the airless vacuum of space, and remains the only crewed vehicle to land anywhere beyond Earth. |
lunar space elevator | Space and Astronomy | 1 | or lunar spacelift , is a proposed transportation system for moving a mechanical climbing vehicle up and down a ribbon-shaped tethered cable that is set between the surface of the Moon "at the bottom" and a docking port suspended tens of thousands of kilometers above in space at the top. |
mach number | Space and Astronomy | 1 | In fluid dynamics , the is a dimensionless quantity representing the ratio of flow velocity past a boundary to the local speed of sound . |
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