Aerospace Science and Technonlogy Dictionary K Section

k: Kilo (thousand).
K-band: A frequency band used in radar extending approximately from 10.9 gigacycles per second to 36 gigacycles per second.
K-corona: That portion of the radiation from the solar corona consisting of the continuous spectrum scattered by electrons.
K-display: In radar, a modified A-display in which a target appears as a pair of vertical deflections or blips instead of a single deflection. When the radar antenna is correctly pointed at the target in azimuth, the blips are of equal height. When not correctly pointed, the difference in blip height is an indication of direction and magnitude of azimuth pointing error. Also called K-scan, K-scope, K-indicator.
K-indicator: = K-display.
K-indices: = magnetic K-indices.
K-scan: = K-display.
K-scope: = K-display.
kaolinite: A hydrous silicate of aluminum. It constitutes the principle mineral in kaolin.
Karman street: = Karman vortex street.
Karman vortex street: (After Theodore von Karman, 1881-1963, Hungarian-born American scientist). A double trail of vortices formed alternately on both sides of a cylinder or similar body moving at right angles to its axis through a fluid, the cortices in one row rotating in a direction opposite to that of the other row.
kelvin: A temperature scale often used in sciences such as astronomy. The fundamental SI unit of thermodynamic temperature defined as 1/273.16 of the thermodynamic temperature of the triple point of water. The Kelvin temperature scale is just like the Celsius scale except that the freezing point of water, zero degrees Celsius, is equal to 273 degrees Kelvin. [ K = C + 273o => F = 9/5C + 32o]
Kelvin scale: = Kelvin temperature scale.
Kelvin temperature scale: (abbr K)
An absolute temperature scale independent of the thermometric properties of the working substance. On this scale, the difference between two temperatures T1 and T2 is proportional to the heat converted into mechanical work by a Carnot engine operating between the isotherms and adiabats through T1 and T2. Also called absolute temperature scale, thermodynamic temperature scale.
For convenience the Kelvin is identified with the Celsius degree. The ice point in the Kelvin scale is 273.15 degrees K. The triple point of water, the fundamental reference points, is 273.16 degrees K. See absolute zero, approximate absolute temperature scale, Rankine temperature scale.
Kelvin Units: A Kelvin Unit refers to a thermometric scale in which the degree intervals are equal to those of the Celsius scale and in which zero(0) degrees equals -273.15 degrees Celsius (absolute zero).
Kennelly-Heaviside layer: = E layer.
Kepler equation: In celestial mechanics M = E - e sin E where M is mean anomaly; E is eccentric anomaly; and e is eccentricity of the orbital ellipse. See anomaly, note.
Kepler laws: The three empirical laws governing the motions of planets in their orbits, discovered by Johannes Kepler (1571-1630). These are: (a) the orbits of the planets are ellipses, with the sun at a common focus; (b) as a planet moves in its orbit, the line joining the planet and sun sweeps over equal areas in equal intervals of time (also called law of equal areas ); (c) the squares of the periods of revolution of any two planets are proportional to the cubes of their mean distances from the sun.
Kepler planetary laws: = Kepler laws.
Keplerian: Pertaining to motion in conformance with Kepler laws, as Keplerian trajectory, Keplerian ellipse.
kerogen: Fossilized insoluble organic material found in sedimentary rocks, usually shales, which can be converted to petroleum products by distillation.
ketones: A class of organic compounds possessing a carbonyl group attached to two hydrocarbon groups.
kettles (geology): Steepsided, usually basin or bowlshaped holes or depressions, commonly without surface drainage, in glacial drift deposits (especially outwash and kame fields). Kettles often contain lakes or swamps; formed by the melting of large detached blocks of stagnant ice (left behind by retreating glaciers) that had been wholly or partly buried by glacial drift. Kettles range in depth from about a meter to as much as 13 km. Thoreau's Walden Pond is an example.
Kevlar (trademark): A Dupont synthetic textile material, lightweight and nonflammable, and with high impact resistance.
kg: Kilogram, the metric standard unit of mass, based on the mass of a metal cylinder kept in France. See gram.
kHz: kilohertz.
kilo: (abbr k)
Prefix meaning multiplied by 1000.
kilocalorie: (abbr kcal)
See calorie.
kilocycle: (abbr kc)
One thousand cycles or 1000 cycles per second.
kilogram: One kilogram is equivalent to 1,000 grams or 2.2 pounds; the mass of a liter of water. Abbreviated "kg", it is the fundamental standard international (SI) unit of mass, it is the only SI unit still maintained by a physical artifact: a platinum-iridium bar kept in the International Bureau of Weights and Measures at Sevres, France.
kilogram: (abbr kg)
The unit of mass in the metric system; the mass of the International Prototype Kilogram, a cylinder of platinum-iridium alloy, stored at Seures, France, by the International Bureau of Weights and Measures.
kilogram calorie: (abbr kg-cal, Kcal, Cal)
See calorie.
kilomegacycle: = gigacycle.
kilometer: One kilometer is equivalent to 1,000 meters or 0.62 miles. Abbreviated "km".
kilometer: (abbr km)
A unit of distance in the metric system.
1 kilometer = 3280.8 feet = 1093.6 yards = 1000 meters = 0.62137 statute miles = 0.53996 nautical miles.
kilometric waves: Electromagnetic waves with wavelengths between 1,000 and 10,000 meters.
kilometric waves: See frequency bands.
kiloparsec: A distance equal to 1000 parsecs.
kilowatt-hour: The amount of energy supplied by one kilowatt (1000 watt) for 1 hour (3600 seconds), equal to 3 600 000 joule. The abbreviation is KwH.
kinematic eddy viscosity: See kinematic viscosity.
kinematic viscosity: (symbol )
A coefficient defined as the ratio of the dynamic viscosity of a fluid to its density.
The kinematic viscosity of most gases increases with increasing temperature and decreasing pressure. For dry air at 0º C, the kinematic viscosity is about 0.13 square centimeter per second. In the theory of atmospheric turbulence the kinematic viscosity is usually replaced by the kinematic eddy viscosity to account for the increased internal friction due to turbulence.
kinematics: The branch of mechanics dealing with the description of the motion of bodies or fluids without reference to the forces producing the motion.
kinetic energy: (symbol E_k)
The energy which a body possesses as a consequence of its motion, defined as one-half the product of its mass m and the square of its speed v, . The kinetic energy per unit volume of a fluid parcel is the , where is the density and v the speed of the parcel. See potential energy.
For relativistic speeds the kinetic energy is given by

where c is the velocity of light in a vacuum, m₀ is the rest mass, and m is the moving mass.
kinetic pressure: Density of kinetic energy (energy in the thermal motions of the plasma particles). For an ideal plasma, pressure is given by p = nkT, that is: pressure = (density) * (Boltzmann's constant)* (temperature)
kinetic pressure: = dynamic pressure.
kinetic theory: The derivation of the bulk properties of fluids from the properties of their constituent molecules, their motions, and interactions.
kinetic-energy equation: = mechanical-energy equation.
kink instability: In plasma physics, a kinking or bending of a current-carrying filament in the pinch effect geometry.
If a slight bend forms in the plasma column of a pinch, the magnetic forces are such as to increase the bend and the column is unstable.
kink mode: Class of MHD instabilities which sometimes develop in a thin plasma column carrying a strong axial current. If a kink begins to develop in such a column the magnetic forces on the inside of the kink become larger than those on the outside, so that in general it tends to grow in magnitude. The column then becomes unstable and can be displaced into the walls of the discharge chamber, causing a disruption.
kipuka: A Hawaiian term for an "island" of land completely surrounded by one or more younger lava flows. A kipuka forms when lava encircles a hill or a slight rise in the ground as it moves downslope or across relatively flat ground. Because they are surrounded by more recent flows, kipukas are often covered with mature vegetation.
Kirchhoff law: The radiation law which states that at a given temperature the ratio of the emissivity to the absorptivity for a given wavelength is the same for all bodies and is equal to the emissivity of an ideal blackbody at that temperature and wavelength.
Loosely put, this important law asserts that good absorbers of a given wavelength are also good emitters of that wavelength. It is essential to note that the Kirchhoff law relates absorption and emission at the same wavelength and at the same temperature. Also called Kirchhoff radiation law.
Kirchhoff law of radiation: The radiation law which states that at a given temperature the ratio of the emissivity to the absorptivity for a given wavelength is the same for all bodies and is equal to the emissivity of an ideal blackbody at that temperature and wavelength.
Kirchhoff's law of radiation: The emissivity of a body is equal to its absorbance at the same temperature.
klystron: An electron tube for converting direct-current energy into radio frequency energy by alternately speeding up and slowing down the electrons. See magnetron.
knot: A nautical mile per hour, 1.1508 statute miles per hour.
knowledge bases (artificial intelligence): Facts, assumptions, beliefs, and heuristics, used in dealing with a database to achieve desired results such as a diagnosis, an interpretation, or a solution to a problem.
knowledge representation: The use of symbolic data structures to represent knowledge so that a computer can manipulate them.
Knudsen flow: The flow of gases through ducts and tubes under conditions intermediate between laminar viscous flow and molecular flow. Also called transition flow.
Knudsen gage: A gage which measures pressure in terms of the net rate of transfer of momentum by molecules between two surface maintained at different temperatures and separated by a distance smaller than the mean free path of the gas molecules. Also called radiometer vacuum gage.
Various types of Knudsen gage are distinguished by the names of the inventors and differ mainly in the shape and method of suspension of the movable element.
Knudsen number: A number used to describe the flow of a low density gas, equal to the ratio where is the mean free path of the gas molecule and is a characteristic length, such as boundary layer thickness, or apparatus dimension.
The Knudsen number is used most commonly to define the extend to which the gas behaves like a collection of independent particles (free-molecule regime, Knudsen number much larger than unity), or like a viscous fluid (continuous regime, Knudsen number much smaller than unity). Intermediate regimes are termed transition region, and slip flow region. See rarefied gas dynamics, note.
Knudsen rate of evaporation: = maximum evaporation rate.
Kondo effect: Change in superconductivity characteristics resulting from magnetic impurities in the compounds involved.
Korteweg-Devries equation: The mathematical representation describing the propagation of long waves of small but finite amplitude.
Kraft process (woodpulp): Woodpulping process in which sodium sulfate is used in the caustic soda pulp-digestion liquor. Also known as sulfate pulping or Kraft pulping.
Kramers-Kronig formula: The relationship between the attenuation coefficient and the dispersion (frequency dependent phase velocity) for viscoelastic waves.
kreep: A yellow-brown glassy lunar mineral enriched in potassium, rare earth elements, and phosphate.
kriging: A method of providing unbiased estimates of variables in regions where the available data exhibit spatial autocorrelation, and these estimates are obtained in such a way that they have minimum variance.
krypton fluoride lasers: Rare gas halide ultraviolet stimulated emission devices in which krypton fluoride is the active lasing medium.
KSC: Kennedy Space Center, Cape Canaveral, Florida.
kurtosis: In statistics, the extent to which a frequency distribution is peaked or concentrated about the mean; it is sometimes defined as the ratio of the fourth moment of the distribution to the square of the second moment.
KWF: Keyword file of events listing DSN station activity.