C

Source edition 1965. Please read the Introduction to find out about this dictionary and our plans for it. Caution, many entries have not been updated from the 1965 version.
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Cae, Cael

International Astronomical Union abbreviations for Caelum. See constellation.

Caelum (abbr Cae, Cael)

See constellation.

cage

To lock a gyro in a fixed position in its case.

caging

The process of orienting and mechanically locking the spin axis of a gyro to an internal reference position.

caisson disease

Those conditions including collapse, neurological changes, and pain, associated with relatively rapid reduction of ambient pressure from levels appreciably higher than 1 atmosphere to 1 atmosphere; and due to the release of inert gases in the body. Also called compressed air illness, bends.

calculating punch

A punched-card machine in which information is read from cards, and the results of sequential operations are punched on cards as they pass through the machine.

calendar

An orderly arrangement of days, weeks, months, etc. to suit a particular need such as civil life. See Julian Day.

calendar day

The period from midnight to midnight. The calendar day is 24 hours of mean solar time in length and coincides with the civil day unless a time change occurs during the day.

calendar year

The year of the Gregorian calendar, common years having 365 days and leap years 366 days.

Each year exactly divisible by 4 is a leap year, except century years (1800, 1900, etc.), which must be exactly divisible by 400 (2000, 2400, etc.) to be leap years. The calendar year is based on the tropical year. Also called civil year.

calibration marker

In radar, a calibration mark on the display to delineate bearing, distance, height, or time.

Callipic cycle

Four Metonic cycles or 76 years.

Callisto

A satellite of Jupiter orbiting at a mean distance of 1,884,000 kilometers. Also called Jupiter IV.

call number

In computer operations, a set of characters identifying a subroutine and containing (a) information concerning parameters to be inserted in the subroutine, (b) information to be used in generating the subroutine, or (c) information related to the operands.

calorie (abbr cal)

A unit of heat originally defined as the amount of heat required to raise the temperature of 1 gram of water through 1° C (the gram-calorie or small calorie).

Several calories are now in use: International Steam Table calorie = 4.1868 joules, mean calorie = 4.19002 joules, thermochemical calorie = 4.184 joules, 15° C calorie = 4.18580 joules, 20° C = 4.1890 joules. The kilogram calorie or kilocalorie is 1000 times as large as a calorie.

calorimeter

An instrument designed to measure heat evolved or absorbed.

Calorimeters are used in some pyrheliometers.

Cam, Caml

International Astronomical Union abbreviations for Camelopardus. See constellation.

Camelopardus (abbr Cam, Caml)

See constellation.

Caml

International Astronomical Union abbreviation for Camelopardus. See constellation.

canard

Pertaining to an aerodynamic vehicle in which horizontal surfaces used for trim and control are forward of the main lifting surface; the horizontal trim and control surfaces in such an arrangement.

Canc

International Astronomical Union abbreviation for Cancer. See constellation.

Cancer (abbr Cnc, Canc)

See constellation.

candela (symbol cd)

The luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 * 10¹² hertz and that has a radiant intensity in that direction of (1/683) watt per steradian (16th CGPM (1979), Resolution 3).

The previous is an excerpt from WWW version of the National Institute of Standards and Technology: Physics Laboratory's International System of Units (SI)

Also called candle.

candle = candela.

Canes Venatici (abbr Cvn, C Ven)

See constellation.

Canis Major (abbr CMa, C Maj)

See constellation.

Canis Minor (abbr CMi, C Min)

See constellation.

canonical time unit

For geocentric orbits, the time required by a hypothetical satellite to move one radian in a circular orbit of the earth's equatorial radius; 13.447052 minutes.

Cap, Capr

International Astronomical Union abbreviations for Capricornus. See constellation.

capability

A power or capacity to do something. Compare characteristic.

Capabilities belong to people, organized forces, or things.

capacity

In computer operations, (a) the largest quantity which can be stored, processed, or transferred; (b) the largest number of digits or characters which may regularly be processed; (c) the upper and lower limits of the quantities which may be processed.

Capr

International Astronomical Union abbreviation for Capricornus. See constellation.

Capricornus (abbr Cap, Capr)

See constellation.

capsule

1. A boxlike component or unit, often sealed. See aneroid.

2. A small, sealed, pressurized cabin with an internal environment which will support life in a man or animal during extremely high altitude flight, space flight, or emergency escape. See ejection capsule.

The term spacecraft is preferred to capsule for any man-carrying vehicle.

3. A container carried on a rocket or spacecraft, as an instrument capsule holding instruments intended to be recovered after a flight.

captive test

A holddown test of a propulsion subsystem, rocket engine or motor. Distinguished from a flight test.

capture

1. Of a central force filed, as of a planet; to overcome by gravitational force the velocity of a passing body and bring the body under the control of the central force field, in some cases absorbing its mass.

2. Acquisition or absorption of an additional particle by an atomic nucleus.

capture effect

An effect in frequency modulation (FM) reception where the stronger signal of two stations on the same frequency completely suppresses the weaker signal.

capturing

The use of a torquer to restrain the spin axis of a gyro to a specified position relative to the spin reference axis.

Car, Cari

International Astronomical Union abbreviations for Carina. See constellation.

carbide

A compound of carbon with one or more metallic elements.

carbon cycle

A sequence of atomic nuclear reactions and spontaneous radioactive decay which serves to convert matter into energy in the form of radiation and high-speed particles, and which is regarded as one of the principal sources of the energy of the sun and other similar stars.

This cycle, first suggested by Bethe in 1938, gets its name from the fact that carbon plays the role of a kind of catalyst in that it is both used by and produced by the reaction, but is not consumed itself. Four protons are, in net, converted into an alpha particle and two positrons (with accompanying neutrinos); and three gamma-ray emissions are emitted directly in addition to the two gamma emissions that ensue from annihilation of the positrons by ambient electrons. This cycle sets in at stellar interior temperatures of the order of 5 million degrees Kelvin.
An even simpler reaction, the proton-proton reaction, is also believed to occur within the sun and may be of equal or greater importance.

carcinogenesis

The origination or production of cancer.

card

1. A punched card, used in computer operations for the storage of information in the form of holes punched through the card material.

Standard punched cards are 7.375 x 3.250 x 0.007 inches, containing either 80 columns in each of which any of 12 positions may be punched or 90 columns in each of which any combination of 6 places may be punched.

2. Any card adapted for the storage of information.

3. A printed-circuit board, usually before other parts are mounted therein. See module, package.

cardiovascular

Pertaining to the heart and the blood vessels.

card punch

A mechanism which punches holes in cards used in computer operations.

An automatic card punch punches cards according to a stored program.

card reader

A mechanism that reproduces the information on punched cards in another form, usually electrical signals.

Cari

International Astronomical Union abbreviation for Carina. See constellation.

Carnot cycle

An idealized reversible thermodynamic cycle. The Carnot cycle consists of four stages: (a) an isothermal expansion of the gas at temperature T₁; (b) an adiabatic expansion to temperature T₂; (c) an isothermal compression at temperature T₂; (d) an adiabatic compression to the original state of the gas to complete the cycle. See Carnot engine, thermodynamic efficiency.

In a Carnot cycle, the net work done is the difference between the heat inputQ₁at higher temperatureT₁and the heat extractedQ₂at the lower temperatureT₂.

Carnot efficiency = thermodynamic efficiency.

Carnot engine

An idealized reversible heat engine working in a Carnot cycle. It is the most efficient engine that can operate between two specified temperatures; its efficiency is equivalent to the thermodynamic efficiency. The Carnot engine is capable of being run either as a conventional engine or as a refrigerator.

carrier

1. In a semiconductor, a mobile conduction electron or hole.

2. In modulation of a signal, a wave suitable for being modulated as a sine wave, a recurring series of pulses, or a direct current.

carrier frequency

The frequency of a carrier wave.

carrier operated device, anti-noise = codan

carrier rocket

A rocket vehicle used to carry something, as in the carrier rocket of the first artificial earth satellite.

carrier wave (abbr cw)

A wave generated at a point in the transmitting system and modulated by the signal.

carry time

In computer operations, the time required for a binary chain to complete its response to an input pulse.

Cartesian coordinates

A coordinate system in which the locations of points in space are expressed by reference to three planes, called coordinate planes, no two of which are parallel. Compare curvilinear coordinates.

The three planes intersect in three straight lines, called coordinate axes. The coordinate planes and coordinate axes intersect in a common point, called the origin. From any point P in space three straight lines may be drawn, each of which is parallel to one of the three coordinate planes. If A, B, C denote these points of intersection, the Cartesian coordinates of P are the distances PA, PB, and PC. If the coordinate axes are mutually perpendicular, the coordinate system is rectangular; otherwise, oblique.

Cas, Cass

International Astronomical Union abbreviations for Cassiopeia. See constellation.

cascaded

Of a series of elements or devices, arranged so that the output of one feeds directly into the input of another, as a series of dynodes or a series of airfoils.

The cascaded series usually serves to amplify the effect.

cascade shower

A group occurrence of cosmic rays. Also called air shower.

Cass

International Astronomical Union abbreviation for Cassiopeia. See constellation.

Cassegrain = Cassegrain telescope.

Cassegrainian telescope = Cassegrain telescope.

Cassegrain telescope

A reflecting telescope in which a small hyperboloidal mirror reflects the convergent beam from the paraboloidal primary mirror through a hole in the primary mirror to an eyepiece in back of the primary mirror. Also called Cassegrainian telescope, Cassegrain. See Newtonian telescope.

Cassiopeia (abbr Cas, Cass)

See constellation.

catalogue = star catalogue.

catalogue number

The designation of a star by the name of a particular star catalogue and the number of the star in that catalogue.

catapult

A power-actuated machine or device for hurling forth something, an airplane or missile, at a high initial speed; also, a device, usually explosive, for ejecting a person from an aircraft. Compare launcher, senses 1 and 2.

catheter

A hollow tube of metal, glass, hard or soft rubber, rubberized silk, etc., for introduction into a body cavity through a narrow canal, for the purpose of discharging the fluid contents of a cavity or for establishing that the canal is unobstructed.

cathode

In an electron tube, an electrode through which a primary stream of electrons enters the interelectrode space. See cold cathode, hot cathode (thermionic cathode), photocathode.

cathode-ray indicator = cathode-ray oscilloscope.

cathode-ray oscillograph = cathode-ray oscilloscope.

cathode-ray oscilloscope

An instrument which displays visually on the face of a cathode-ray tube instantaneous voltages of electrical signals. Either the intensity or the displacement of the trace may be controlled by the signal voltage. More commonly called oscilloscope. Also called cathode-ray oscillograph. See radarscope.

cathode-ray tube (abbr CRT)

A vacuum tube consisting essentially of an electron gun producing a concentrated electron beam (or cathode ray) which impinges on a phosphorescent coating on the back of a viewing face (or screen). The excitation of the phosphor produces light, the intensity of which is controlled by regulating the flow of electrons. Deflection of the beam is achieved either electromagnetically by currents in coils around the tube, or electrostatically by voltages on internal deflection plates.

cathode rays

Electrons that are driven from the negative electrode (the cathode) of a discharge tube.

cathode-ray screen

See cathode-ray tube.

catoptric light

A light concentrated into a parallel beam by means of a reflector.

A light so concentrated by means of refracting lenses or prisms is a dioptric light.

cat whisker

A fine wire pickoff, specifically a gyro pickoff.

Cauchy number

A nondimensional number arising in the study of the elastic properties of a fluid. It may be written U²p/E, where U is a characteristic velocity; p (lower case Rho) is the density; and E the modulus of elasticity of the fluid. It is the square of the Mach number.

cavitation

The formation of bubbles in a liquid, occurring whenever the static pressure at any point in the fluid flow becomes less than the fluid vapor pressure.

cavity heat receiver = hohlraum.

cavity resonator

See resonator.

C-band

See frequency band.

C-display

In radar, a rectangular display in which targets appear as blips with bearing indicated by the horizontal coordinate and angles of elevation by the vertical coordinate. Also called C-scan and C-scope.

celestial

1. Of or pertaining to the heavens.

2. Short for celestial navigation.

celestial body

Any aggregation of matter in space constituting a unit for astronomical study, as the sun, moon, a planet, comet, star, nebula, etc. Also called heavenly body.

celestial coordinates

Any set of coordinates used to define a point on the celestial sphere.

The horizon, celestial equator, ecliptic, and galactic systems of celestial coordinates are based on the celestial horizon, celestial equator, ecliptic, and galactic equator, respectively, as the primary great circle. See coordinate, Table VI, for a comparison of the systems.

celestial equator

The primary great circle of the celestial sphere in the equatorial system, everywhere 90° from the celestial poles; the intersection of the extended plane of the equator and the celestial sphere. Also called equinoctial.

celestial equator system of coordinates = equatorial system.

celestial guidance

The process of directing movements of an aircraft or spacecraft, especially in the selection of a flight path, by reference to celestial bodies. Also called automatic celestial navigation. See guidance, celestial navigation.

celestial horizon

That great circle of the celestial sphere formed by the intersection of the celestial sphere and a plane through the center of the earth and perpendicular to the zenith-nadir line. Also called rational horizon. See horizon, horizon system.

celestial-inertial guidance

The process of directing the movements of an aircraft or spacecraft, especially in the selection of a flight path, by an inertial guidance system which also receives inputs from observations of celestial bodies.

celestial latitude

Angular distance north or south of the ecliptic; the arc of a circle of latitude between the ecliptic and a point on the celestial sphere, measured northward or southward from the ecliptic through 90°, and labeled N or S to indicate the direction of measurement. See ecliptic system of coordinates.

celestial line of position

A line of position determined by observation of one (or more) celestial bodies.

celestial longitude

Angular distance east of the vernal equinox, along the ecliptic; the arc of the ecliptic or the angle at the ecliptic pole between the circle of latitude of the vernal equinox and the circle of latitude of a point on the celestial sphere, measured eastward from the circle of latitude of the vernal equinox, through 360°. See ecliptic system of coordinates.

celestial mechanics

The study of the theory of the motions of celestial bodies under the influence of gravitational fields. See gravitation.

celestial meridian

A great circle of the celestial sphere, through the celestial poles and the zenith.

The expression usually refers to the upper branch, that half of the great circle from pole to pole which passes through the zenith; the other half being the lower branch. The celestial meridian coincides with the hour circle through the zenith and the vertical circle through the elevated pole.

celestial navigation

The process of directing a craft from one point to another by reference to celestial bodies of known coordinates.

Celestial navigation usually refers to the process as accomplished by a human operator. The same process accomplished automatically by a machine is usually termed celestial guidance or sometimes automatic celestial navigation.

celestial observation

In navigation, the measurement of the altitude of a celestial body, or the measurement of azimuth, or measurement of both altitude and azimuth. Also called sight.

The expression may also be applied to the data obtained by such measurement.

celestial pole

Either of the two points of intersection of the celestial sphere and the extended axis of the earth, labeled N or S to indicate whether the north celestial pole or the south celestial pole.

celestial sphere

An imaginary sphere of infinite radius concentric with the earth, on which all celestial bodies except the earth are assumed to be projected.

celestial triangle

A spherical triangle on the celestial sphere, especially the navigational triangle.

cell

In computers, an elementary unit of storage, as binary cell, decimal cell.

Celsius temperature scale (abbr C)

Same as centigrade temperature scale.

The Ninth General Conference on Weights and Measures (1948) replaced the designation degree centigrade by degree Celsius.

Cen, Cent

International Astronomical Union abbreviation for Centaurus. See constellation.

cent

In acoustics, the interval between two sounds whose basic frequency ratio is the twelve-hundredth root of 2.

Centaurus (abbr Cen, Cent)

See constellation.

center frequency

The assigned carrier frequency of a frequency modulation (FM) station; the unmodulated frequency of an FM system.

center of mass

That point in a given body, or in a system of two or more bodies that act together in respect to another body, which represents the mean position of the matter in the body of bodies. See barycenter.

center of thrust = thrust axis.

centi (abbr C)

A prefix meaning one-hundredth.

centigrade temperature scale (abbr C)

A temperature scale with the ice point at 0° and the boiling point of water at 100°. Now called Celsius temperature scale.

Conversion to the Fahrenheit temperature scale is according to the formula ° C = 5/9 (°F - 32)

centimeter (abbr cm)

One-hundredth of a meter; approximately 0.3937 U.S. inch, exactly 1/2.54 inch.

centimeter-gram-second system (abbr cgs)

A system of units based on the centimeter as the unit of length, the gram as the unit of mass, and the second as the unit of time.

centimetric waves.

See frequency band.

centipoise (abbr cp)

A unit of viscosity. See poise.

central control

1. Control exercised over an extensive and complicated system from a single center.

2. Usually capitalized. The place, facility, or activity from which this control is exercised; specifically, at Cape Canaveral or at Vandenberg AFB, the place, facility, or activity at which the whole action incident to a test launch and flight is coordinated and controlled, from the make-ready at the launch site and on the range, to the end of the rocket flight downrange.

For a few seconds during the actual launch, control of a missile is exercised from the blockhouse, but it almost immediately reverts to Central Control for guidance and tracking, with two men in essential control. One of these is the supervisor of range operations, the other is the range safety officer.

central force

A force which for purposes of computation can be considered to be concentrated at one central point with its intensity at any other point being a function of the distance from the central point.

Gravitation is considered as a central force in celestial mechanics.

central force field

The spatial distribution of the influence of a central force.

centrifugal acceleration = centrifugal force.

centrifugal compressor

A compressor having one or more vaned rotary impellers which accelerate the incoming fluid radially outward into a diffuser, compressing by centrifugal force. Sometimes called a centrifugal-flow compressor . Compare axial-flow compressor.

centrifugal-flow compressor = centrifugal compressor.

centrifugal force

The apparent force in a rotating system, deflecting masses radially outward from the axis of rotation, with magnitude per unit mass ²R, where is the angular speed of rotation; and R is the radius of curvature of the path. This magnitude may also be written as V²/R, in terms of the linear speed V. This force (per unit mass) is equal and opposite to the centripetal acceleration. Also called centrifugal acceleration.

The centrifugal force on the earth and atmosphere due to rotation about the earth's axis is incorporated with the field of gravitation to form the field of gravity.

centrifuge

Specifically, a large motor-driven apparatus with a long arm at the end of which human and animal subjects or equipment can be revolved and rotated at various speeds to simulate (very closely) the (prolonged) accelerations encountered in high-performance aircraft, rockets, and spacecraft. Sometimes called astronautic centrifuge.

centripetal acceleration

The acceleration on a particle moving in a curved path, directed toward the instantaneous center of curvature of the path, with magnitude v²/R, where v is the speed of the particle and R the radius of curvature of the path. This acceleration is equal and opposite to the centrifugal force per unit mass.

CEP (abbr) = circle of equal probability.

Cep, Ceph

International Astronomical Union abbreviations for Cepheus. See constellation.

Cepheus (abbr, Cep, Ceph)

See constellation.

caramel = cermet.

ceramic

An inorganic compound or mixture requiring heat treatment to fuse it into a homogeneous mass usually possessing high temperature strength but low ductility. Types and uses range from china for dishes to refractory liner for nozzles.

Cerenkov radiation

The radiation from a charged particle whose velocity is greater than the phase velocity that an electromagnetic wave would have if it were propagating in the medium. The particle will continue to lose energy by radiation until its velocity is less than this phase velocity.

This phenomenon is analogous to the generation of a shock wave when an object is traveling faster than the sound velocity of the medium. A bow wave is set up which radiates energy into the medium and slows down the object.
The angle that the cone of luminescence makes with the direction of motion of the particle can be used to measure the velocity of the particle.

cermet [ceramic + metal]

A body consisting of ceramic particles bonded with a metal; used in aircraft, rockets, and spacecraft for high strength, high temperature applications. Also called ceramal [ceramic + alloy].

Cet, Ceti

International Astronomical Union abbreviations for Cetus . See constellation.

cetane number

A number indicating the relative ignitability of a fuel oil for compression-ignition engines.

Ceti

International Astronomical Union abbreviations for Cetus . See constellation.

Cetus (abbr Cet, Ceti)

See constellation.

C-figure = C-index

CGS system

A system of units based on the centimeter, the gram, and the second.

Cha, Cham

International Astronomical Union abbreviations for Chamaeleon. See constellation.

chad

The piece removed when punching a hole, as in a card. See chadless.

chadless

A type of punching in which the chad is left attached by about 25 percent of the circumference of the hole, at the leading edge.

Chadless punching is used where it is undesirable to mutilate information written or printed on the punched medium.

chaff = window.

chain radar beacon

A radar beacon with a very fast recovery time.

This recovery time provides the possibility of simultaneously interrogating and tracking the beacon by as many radars as required so long as they are phased, synchronized, or the sum total pulse recurrence frequency does not exceed the maximum pulse recurrence frequency characteristics of the beacon.

chain reaction

A reaction in which one of the agents necessary to the reaction is itself produced by the reaction, thus causing like reactions.

In the neutron-fission chain reaction, a neutron striking a fissionable atom causes a fission releasing neutrons which cause other fissions.

challenger = interrogator-responsor.

Cham

International Astronomical Union abbreviation for Chamaeleon. See constellation.

Chamaeleon (abbr Cha, Cham)

See constellation.

chamber = combustion chamber.

chamber pressure (symbol P_c)

The pressure of gases within the combustion chamber of a rocket engine.

chamber volume (symbol V_c)

The volume of the rocket combustion chamber including the convergent portion of the nozzle up to the throat.

change of the moon = new moon.

channel

1. Short for frequency channel.

2. In computer operations: (a) That portion of a storage medium which is accessible to a given reading station. See track. (b) A path of flow, usually including one or more operations.

Chapman region

A hypothetical region in the upper atmosphere in which the distribution of electron density with height can be described by a theoretical equation derived by Sydney Chapman.

Some of the basic assumptions used to develop the equation were that the ionizing radiation from the sun is essentially monochromatic, that the ionized constituent is distributed exponentially (with a constant scale height), and that there is an equilibrium condition between the creation of free electrons and their loss by recombination.

Chappius bands

See absorption band.

character

One of a set of elementary marks or events which may be combined to express information.

For example, a decimal digit (0 to 9), a letter (A to Z), or a symbol (comma, plus, minus, etc.).

characteristic

Specifically, a distinguishing quality, property, feature, or capability of a machine or piece of equipment, or of a component part.

The characteristics of an aircraft are (1) qualities such as stability, maneuverability, and strength; (2) features such as number, kind, or power of engines, and size, shape, or number of wings; and (3) capabilities such as range, speed, and payload.

characteristic chamber length (symbol L*)

The length of a straight cylindrical tube having the same volume as the chamber of a rocket engine would have if it had no converging section.

characteristic equation

1. An equation defining the characteristics of a set of partial differential equations.

2. A linear algebraic equation determining the eigenvalues or free waves of a boundary-value problem. See characteristic value problem.

characteristic exhaust velocity (symbol c*)

Of a rocket engine, a descriptive parameter, c* = V_e/C_F where V_e is effective exhaust velocity and C_F is thrust coefficient. Also called characteristic velocity.

characteristic Larmor radius

The size of the Larmor orbit of a charged particle whose rotational velocity is equal to the Alfvén speed.

characteristic length (symbol l, )

A convenient reference length (usually constant) of a given configuration, such as overall length of an aircraft, the maximum diameter or radius of a body of revolution, a chord or span of a lifting surface, etc.

characteristic mode = normal mode of vibration.

characteristics

Lines or surfaces associated with a partial differential equation, or with a set of such equations, which are at all points tangent to characteristics directions, determined by certain specified linear combinations of the equations.

The use of these lines or surfaces may facilitate the solution of the equations and is known as the method of characteristics. The method has been particularly successful, for example, in the problem of finite-amplitude expansion and shock waves.

characteristic value

See characteristic value problem.

characteristic-value problem

A problem in which an undetermined parameter is involved in the coefficients of a differential equation, and in which the solution of the differential equation, with associated boundary conditions, exists only for certain discrete values of the parameter, called eigenvalues, or characteristic values, sometimes principal values.

An important example of a physical problem which leads to a characteristic-value problem is the determination of the modes and frequencies of a vibrating system. In this case the dependent variable of the differential equation represents the displacements of the system and the parameter represents the frequencies of vibration.

characteristic velocity (symbol c*) = characteristic exhaust velocity.

charge neutrality

The approximate equality of positive and negative particles in high-density plasmas.

This phenomenon, which is sometimes called electrical neutrality, is a result of the extremely large electric space charge fields that would arise if the densities were not equal. Although the positive and negative charge densities are seldom exactly equal, their percentage difference is so small as to be negligible. It is not difficult to maintain this condition in an active plasma since ionization or recombination always produces or destroys an ion pair together.

charge spectrum

The range and magnitude of electric charges with reference to cosmic rays at a specific altitude.

Charles-Gay-Lussac law

An empirical generalization that in a gaseous system at constant pressure, the temperature increase and the relative volume increase stand in approximately the same proportion for so-called perfect gases. Mathematically, t - t₀ + (1 / c [ ( v - v₀ ) / v₀] where t is temperature; v is volume; and c is a coefficient of thermal expansion independent of the particular gas. If the centrigrade temperature scale is used and v₀ is the volume at 0° C, then the value of the constant c is approximately 1/273. Also called Charles law, Gay-Lussac law.

Charles law = Charles-Gay-Lussac law.

charring ablator

An ablation material characterized by the formation of a carbonaceous layer at the heated surface which impedes heat flow into the material by it insulating and reradiating characteristics.

chase pilot

A pilot who flies an escort airplane advising a pilot who is making a check, training, or research flight in another craft.

chaser

The vehicle that maneuvers in order to effect a rendezvous with an orbiting object.

check flight

1. A flight made to check or test the performance of an aircraft, rocket, or spacecraft, or a piece of equipment or component, or to obtain measurements or other data on performance; a test flight.

2. A familiarization flight in an aircraft, or a flight in which a pilot or other aircrew member or members are tested or examined for proficiency.

checking

Presence of a network of fine hairline cracks on the surface of a structure usually induced by poor machining technique.

checkout

1. A sequence of actions taken to test or examine a thing as to its readiness for incorporation into a new phase of use, or for the performance of its intended function.

2. The sequence of steps taken to familiarize a person with the operation of an airplane or other piece of equipment.

In sense 1, a checkout is usually taken at a transition point between one phase of action and another. To shorten the time of checkout, automation is frequently employed.

checkout GSE

Ground support equipment used to make a checkout, which see, sense 1.

cheese antenna

A cylindrical parabolic reflector enclosed by two plates perpendicular to the cylinder, so spaced as to permit the propagation of more than one mode in the desired direction of polarization.

chemical energy

Energy produced or absorbed in the process of a chemical reaction. In such a reaction, energy losses or gains usually involve only the outermost electrons of the atoms or ions of the system undergoing change; here a chemical bond of some type is established or broken without disrupting the original atomic or ionic identities of the constituents.

Chemical changes, according to the nature of the materials entering into the change, may be induced by heat (thermochemical), light (photochemical), and electric (electrochemical) energies.

chemical fuel

1. A fuel that depends upon an oxidizer for combustion or for development of thrust, such as liquid or solid rocket fuel or internal-combustion-engine fuel; distinguished from nuclear fuel.

2. A fuel that uses special chemicals, such as the fuel once projected for the afterburner of the B-70.

chemical pressurization

The pressurization of propellants tanks in a rocket by means of high-pressure gases developed by the combustion of a fuel and oxidizer or by the decomposition of a substance.

chemiluminescence

Any luminescence produced by chemical action. See airglow.

chemisorption

The binding of a liquid or gas on the surface or in the interior of a solid by chemical bonds or forces.

chemosphere

The vaguely defined region of the upper atmosphere in which photochemical reactions take place. It is generally considered to include the stratosphere (or the top thereof) and the mesosphere, and sometimes the lower part of the thermosphere. See atmospheric shell.

This entire region is the seat of a number of important photochemical reactions involving atomic oxygen O, molecular oxygen O₂, ozone O₃, hydroxyl OH, nitrogen N₂, sodium Na, and other constituents to a lesser degree.

chest-to-back acceleration

See physiological acceleration.

chirp

An all-encompassing term for the various techniques of pulse expansion-pulse compression applied to pulse radar; a technique to expand narrow pulses to wide pulses for transmission, and compress wide received pulses to the original narrow pulse width and wave shape, to gain improvement in signal-to-noise ratio without degradation to range resolution and range discrimination.

chi-square test

A statistical significance test based on frequency of occurrence; it is applicable both to qualitative attributes and quantitative variables. Among its many uses, the most common are test of hypothesized probabilities or probability distributions (goodness of fit), statistical dependence or independence (association), and common population (homogeneity).

The formula for chi square (x²) depends upon intended use, but is often expressible as a sum of terms of the type (f - h)² / h where f is an observed frequency and h is its hypothetical value.

chlorate candle

A mixture of solid chemical compounds which, when ignited, liberates free oxygen.

Chlorella

A genus of unicellular green algae, considered to be adapted to converting carbon dioxide into oxygen in a closed ecological system See closed ecological system.

choked flow

Flow in a duct or passage such that the flow upstream of a certain critical section cannot be increased by a reduction of downstream pressure.

chokes

Pain and irritation in the chest and throat as a result of reduced ambient pressure.

choking Mach number

The Mach number at some reference point in a duct or passage (e.g., at the inlet) at which the flow in the passage becomes choked. See choked flow.

chondrite

A meteoritic stone characterized by small rounded grains or spherules.

chopper

A device used to interrupt the path of radiation, as a beam of light, from a single source or to alternate it between two sources.

chord

1. A straight line intersecting a circle or other curve, or a straight line connecting the ends of an arc.

2. (symbol c). In aeronautics, a straight line intersecting or touching an airfoil profile at two points; specifically, that part of such a line between two points of intersection.

This line is usually a datum line joining the leading and trailing edges of an airfoil, joining the ends of the mean line of an airfoil profile, from which the ordinates and angles of the airfoil are measured. As such a datum line, it is sometimes called the geometric chord, to distinguish it from a chord established on the basis of any other considerations.

3. = chord length.

In sense 3, points or stations along a chord are designated in percentages or fractions of the chord or chord length from the leading edge, as, a point at 25 percent, or one-quarter, chord.

chord length

The length of the chord of an airfoil section between the extremities of the section.

For many airfoils, the chord is established intersecting the airfoil profile at its extremities, and the chord length is equal to the length of the chord between the points of intersection; for airfoils where the chord is established by a point or points of tangency or intersection not at the extremities, however, the chord length is considered to extend beyond either or both points, as necessary, to equal the maximum length of the profile. See chord, senses 2 and 3.

choroisotherm

See isotherm, note.

chromatography

The separation of chemical substances by making use of differences in the rates at which the substances travel through or along a stationary medium.

chromosphere

A thin layer or relatively transparent gases above the photosphere of the sun.

chronoisotherm

See isotherm, note.

chronometer noon

See solar noon.

chronometer time

See time.

chronometric data

Data in which the desired quantity is the time of occurrence of an event or the time interval between two events.

chronotron

A device which utilizes a measurement of the position of the superposed loci of a pair of pulses on a transmission line to determine the time between the events which initiate the pulses.

chuffing = chugging.

chugging

A form of combustion instability in a rocket engine, characterized by a pulsing operation at a fairly low frequency, sometimes defined as occurring between particular frequency limits; the noise made in this kind of combustion. Also called chuffing, bumping.

C-index

A subjectively obtained daily index of geomagnetic activity. Each day's record is evaluated on the basis of 0 for quiet, 1 for moderately disturbed, and 2 for very disturbed. Also called C-figure, magnetic character figure. See geomagnetism.

cine-theodolite

A photographic tracking instrument which records on each film frame the target and the azimuth and elevation angles of the optical axis of the instrument. Also called Askania.

Cir, Circ

International Astronomical Union abbreviations for Circinus. See constellation.

circadian rhythm

A regular change in physiological function occurring in approximately 24-hour cycles.

Circinus (abbr Cir, Circ)

See constellation.

circle of declination = hour circle.

circle of equal altitude = parallel of altitude

circle of equal declination = parallel of declination.

circle of equal probability (abbr CEP)

A measure of the accuracy with which a rocket or missile can be guided; the radius of the circle at a specific distance in which 50 percent of the reliable shots land. Also called circular error probable, circle of probable error.

circle of latitude

A great circle of the celestial sphere through the ecliptic poles, and hence perpendicular to the plane of the ecliptic.

circle of longitude

A circle of the celestial sphere, parallel to the ecliptic. Also called parallel of latitude.

circle of probable error = circle of equal probability.

circle of right ascension = hour circle.

circuit

A network providing one or more closed paths.

circuit element

See element, sense 2.

circular area

Of a circle, the square of the diameter.

Circular area = 1.2733 * true area.
True area = 0.785398 * circular area.

circular cylindrical coordinates = cylindrical coordinates.

circular dispersion (abbr CD)

In rocketry, the diameter of a circle within which 75 percent of the events under study occur. CD = 3.330 where = standard deviation.

Circular dispersion is most often used as a measure of error of the accuracy with which rockets reach their intended target.

circular error probable = circle of equal probability.

circular frequency = angular frequency (symbol ).

circular inch

The area of a circle 1 inch in diameter.

circularly polarized sound wave

A transverse wave in an elastic medium in which the displacement vector at any point rotates about the point with constant angular velocity and has a constant magnitude.

A circularly polarized wave is equivalent to two super-posed plane polarized waves of sinusoidal form in which the displacements have the same amplitude, lie in perpendicular planes, and are in quadrature.

circularly polarized wave

An electromagnetic wave for which the electric or the magnetic field vector, or both, at a point describe a circle.

This term is usually applied to transverse waves.

circular mil

The area of a circle with a diameter of 0.001 inch; a unit used for the measurement of small circular areas, such as the cross section of a wire.

One circular mil = 7.85 x 10^-7 square inch.

circular polarization

The polarization of a wave radiated by a constant electric vector rotating in a plane so as to describe a circle. See elliptical polarization.

circular scanning

Scanning in which the direction of maximum radiation generates a plane or a right circular cone whose vertex angle is close to 180°.

circular velocity

At any specific distance from the primary, the orbital velocity required to maintain a constant-radius orbit.

circulating memory =delay-line storage.

circulating register = delay-line storage.

circulation

1. The flow or motion of a fluid in or through a given area or volume.

2. A precise measure of the average flow of fluid along a given closed curve. Mathematically, circulation is the line integral. about the closed curve, where v is the fluid velocity, and dr is a vector element of the curve.

By Stokes theorem, the circulation about a plane curve is equal to the total vorticity of the fluid enclosed by the curve.
The given curve may be fixed in space or may be defined by moving fluid parcels.

circulation integral

The line integral of an arbitrary vector taken around a closed curve. Thus, is the circulation integral of the vector a around the closed curve; dr is an infinitesimal vector element of the curve. If the vector is the velocity, this integral is called the circulation.

circumlunar

Around the moon, generally applied to trajectories.

cislunar

[Latin cis, on this side]. Of or pertaining to phenomena, projects, or activity in the space between the earth and moon, or between the earth and the moon's orbit. Compare translunar, circumlunar.

civil day

See mean solar day.

civil time

See mean time, note.

civil twilight

See twilight, note.

civil year = calendar year.

clad = cladding.

cladding

A coating placed on the surface of a material and usually bonded to the material. Also called clad.

Cladding is used extensively in nuclear reactor cores to prevent corrosion of the fissionable material by the coolant.

clamping circuit

1. A circuit which maintains either extremity of a waveform at a prescribed potential.

2. A network for adjusting the absolute voltage level of a waveform.

Clapeyron-Clausius equation

The differential equation relating pressure to temperature in a system in which two phases of a substance are in equilibrium. dp/dT = L/(T V) where p is pressure; T is temperature; L is the latent heat of the phase change; and V is the difference in volume of the phases. Also called Clapeyron equation, Clausius-Clapeyron equation.

Clapeyron equation = Clapeyron-Clausius equation.

Clausius-Clapeyron equation = Clapeyron-Clausius equation.

cleanup

1. The process of removing gas from a vacuum system or device by sorption or ion pumping.

2. In aeronautics, the process of improving external shape and smoothness of an aircraft to reduce its drag.

clear

To restore a storage or memory device to a prescribed state, usually that denoting zero. See reset.

climatology

See meteorology, note.

clipper = clipping circuit.

clipping circuit

A pulse-shaping network which removes that part of a waveform which tends to extend above, or below, a chosen voltage level. Also called clipper.

clo

The amount of insulation which will maintain normal skin temperature of the human body when heat production is 50 kilogram-calorie per meter squared per hour, air temperature is 70° F, and the air is still.

One clo is roughly equivalent to the amount of insulation provided by the average businessman's suit in a temperature climate.

clock frequency

The master frequency of periodic pulses which schedule the operation of a machine, as a computer.

clock pulse

A pulse used for timing purposes. In pulse-code-modulation systems, a timing pulse which occurs at the bit rate.

closed ecological system

A system that provides for the maintenance of life in an isolated living chamber through complete reutilization of the material available, in particular, by means of a cycle wherein exhaled carbon dioxide, urine, and other waste matter are converted chemically or by photosynthesis into oxygen, water, and food. Compare controlled-leakage system, open system.

closed-loop system

A system in which the output is used to control the input. See feedback control loop.

closed-loop telemetry

1. A telemetry system which is used as the indicating portion of a remote-control system.

2. A system used to check out test vehicle or telemetry performance without radiation of radio-frequency energy.

closed respiratory gas system

A completely self-contained system within a sealed cabin, capsule, or spacecraft that will provide adequate oxygen for breathing, maintain adequate cabin pressure, and absorb the exhaled carbon dioxide and water vapor.

closed system

1. In thermodynamics, a system so chosen that no transfer of mass takes place across its boundaries; for example, a fluid parcel undergoing a saturation-adiabatic process, as opposed to a pseudoadiabatic expansion. See open system.

2. In mathematics, a system of differential equations and supplementary conditions such that the values of all the unknowns (dependent variables) of the system are mathematically determined for all values of the independent variables (usually space and time) to which the system applies.

3. = closed ecological system.

4. A system which constitutes a feedback loop so that the inputs and controls depend on the resulting output. For example, an automatic radar-controlled tracking system.

closet approach

1. The event that occurs when two planets or other celestial bodies are nearest to each other as they orbit about the sun or other primary.

2. The place or time of such an event.

cloud rate

The speed at which two bodies approach each other.

cloud absorption

The absorption of electromagnetic radiation by the water drops and water vapor within a cloud. Compare cloud attenuation.

For insolation (incoming solar radiation), clouds absorb rather small fractions, particularly of the shorter wavelengths. Even for depths of clouds of the order of 20,000 feet, measurements suggest absorptions of less than 30 percent, while layers only 1000 to 2000 feet thick may absorb only about 5 percent. However, for long wave terrestrial radiation, even very thin layers of cloud act as almost complete black-body absorbers.

cloud attenuation

Usually, the reduction in intensity of microwave radiation by clouds in the earth's atmosphere. For the centimeter wavelength band, clouds produce Rayleigh scattering. The attenuation is due largely to scattering, rather than to absorption, for both ice and water clouds. See precipitation attenuation. Compare cloud absorption.

cloud band

A broad band of clouds, from about 10 to 100 or more miles wide, and varying in length from a few tens of miles to hundreds of miles. See cloud streets.

cloud chamber

A device for observing the paths of ionizing particles, based on the principle that supersaturated vapor condenses more readily on ions than on neutral molecules.

cloud physics

A subdivision of physical meteorology concerned with physical properties of clouds in the atmosphere and the processes occurring therein.

Cloud physics, broadly considered, embraces not only the study of condensation and precipitation processes in clouds, but also radiative transfer, optical phenomena, electrical phenomena, and a wide variety of hydrodynamic and thermodynamic processes peculiar to natural clouds.

cloud seeding

Any technique carried out with the intent of adding to a natural cloud in a planetary atmosphere certain substances that will altar the natural development of that cloud.

cloud street

A line of cumuliform clouds frequently one cumulus element wide, but ranging upward in width so that it is sometimes difficult to differentiate between streets and bands. Typical dimensions are: axis spacing, 1 to 30 miles; length of cloud streets, 10 to 200 miles; cell spacing along axis, 1/2 to 2 miles. See cloud band.

clusec

A flow rate equal to 0.01 lusec.

cluster

Two or more rocket motors bound together so as to function as one propulsion unit.

clutter

1. Atmospheric noise, extraneous signals, etc., which tend to obscure the reception of a desired signal in a radio receiver, radarscope, etc.

As compared with interference, clutter refers more particularly to unwanted reflections on a radar plan position indicator, such as ground return, but the terms are often used interchangeably.

2. = window.

CMa, C Maj

International Astronomical Union abbreviations for Canis Major. See constellation.

CMi, C Min

International Astronomical Union abbreviations for Canis Minor. See constellation

Cnc, Canc

International Astronomical Union abbreviations for Cancer. See constellation.

co

1. A prefix meaning 90° minus the value with which it is used. Thus, if the latitude is 30°, the colatitude is 90° - 30° = 60°.

2. A prefix meaning in common, as in coaxial, having a common axis.

coaltitude = zenith distance.

coast

A memory feature on a radar which, when activated, causes the range and angle systems to continue to move in the same direction and at the same speed as that required to track an original target.

Coast is used to prevent lock-on to a stronger target if approached by the target being tracked.

coasting flight

The flight of a rocket between burnout or thrust cutoff of one stage and ignition of another, or between burnout and summit altitude or maximum horizontal range.

coated optics

Optical elements (lenses, prisms, etc.) which have their surfaces covered with a thin transparent film to minimize reflection and loss of light in the system.

coaxial cable

A form of waveguide consisting of two concentric conductors insulated from each other.

codan (abbr) = carrier operated device, anti-noise

A device which silences a receiver except when a carrier signal is being received.

code

1. A system of symbols or signals for representing information, and the rules for associating them.

2. The set of characters resulting from the use of a code as defined in sense 1.

3. Specifically, to translate a problem to a routine expressed in machine language for a specific computer.

4. To express given information by means of a code, to encode.

codeclination

Ninety degrees minus the declination. When the declination and latitude are of the same name, codeclination is polar distance measured from the elevated pole.

coded decimal digit

In computer operation, a decimal digit expressed in a code, usually a four-digit binary code.

coding

The arrangement in a coded form, usually acceptable to a specific computer, of the instructions for the operations necessary to solve a problem.

coefficient (abbr coeff)

1. A number indicating the amount of some change under certain specified conditions, often expressed as a ratio.

For example, the coefficient of linear expansion of a substance is the ratio of its change in length to the original length for a unit change of temperature from a standard.

2. A constant in an algebraic equation.

3. One of several parts which combine to make a whole, as the maximum deviation produced by each of several causes.

coefficient of barotropy.

See barotropy.

coefficient of compressibility

The relative decrease of the volume of a gaseous system with increasing pressure in an isothermal process. This coefficient is -(1/V)(V/ p)_Twhere V is the volume; p is the pressure; and T is the temperature. The reciprocal of this quantity is the bulk modulus. Also called compressibility. Compare coefficient of thermal expansion, coefficient of tension.

coefficient of diffusion = diffusivity.

coefficient of heat conduction = thermal conductivity.

coefficient of molecular viscosity = dynamic viscosity.

coefficient of mutual diffusion

A quantity in the kinetic theory of gases which measures the tendency of gases to diffuse into one another in nonturbulent flow.

This diffusion coefficient is a property of the gases in question and of the assumed nature of the molecular impacts in the diffusion process. For rigid, perfectly elastic, spherical molecules the coefficient of mutual diffusion d_1,2 is, in square centimeters per second, where n is Loschmidt number (the number of molecules per cubic centimeter); ₁, ₂ and m₁, m₂ are the effective molecular diameters and masses of the two gases, respectively; T is the temperature,°K; and k is Boltzmann constant.

coefficient of tension

The relative increase of pressure of a system with increasing temperature in an isochoric process. In symbols this quantity is (1/p)(p/ T)_Vwhere p is pressure; T is temperature; and V is volume. Compare coefficient of compressibility, coefficient of thermal expansion.

coefficient of thermal conduction = thermal conductivity.

coefficient of thermal conductivity =thermal conductivity.

coefficient of thermal expansion

The ratio of the change of length per unit length (linear), or change of volume per unit volume (voluminal), to the change of temperature.

coefficient of viscosity= dynamic viscosity.

coherence

In radar, a relation between two wave trains such that, when they are brought into coincidence, they are capable of producing interpretable interference phenomena.

This is limited to those wave trains which have fixed or slowly varying phase relationships with each other.

In contract are the rapid interference phenomena produced by the superposition of the more or less randomly scattered waves from hydrometeors.

coherent

1. Of electromagnetic radiation, being in phase, so that waves at various points in space act in unison, as in a laser producing coherent light.

2. Having a fixed relation between frequency and phase of input and output signal.

coherent carrier

A carrier wave derived from a continuous-wave signal in such a way that its frequency and phase have a fixed relationship to the frequency and phase of the reference signal.

coherent echo

A radar echo whose phase and amplitude at a given range remain relatively constant.

Hills, buildings, and slowly moving point targets such as ships are examples of objects which produce coherent radar echoes. Volume targets (such as clouds and precipitation) give noncoherent echoes. The classification of an echo as coherent or noncoherent is closely related to the spatial resolution (beam width) of the radar or the volume occupied by the radar pulse. Thus, small atmospheric inhomogeneities which give rise to noncoherent echoes, would give coherent echoes if the radar volume were reduced in size to the order of magnitude of the inhomogeneities themselves.

coherent oscillator (abbr Coho)

An oscillator which provides a reference by which the radio frequency phase difference of successive received pulses may be recognized. See coherent reference.

coherent radar

A type of radar that employs circuitry which permits comparison of the phase of successive received target signals.

coherent reference

The reference signal, usually of stable frequency, to which other signals are phase-locked to establish coherence throughout a system.

coherent transponder

A transponder, the output signal of which is coherent with the input signal.

Coho (abbr) = coherent oscillator.

coincidence circuit

An electronic circuit that produces a usable output pulse only when each of two or more input circuits receive pulses simultaneously or within an assignable time interval.

coincidence counter

A device using ionization counters and coincidence circuits to count and determine the direction of travel of ionized particles, particularly cosmic rays.

coincident-current magnetic core

A binary magnetic core in which information is stored as the result of current flowing simultaneously in two or more independent windings.

Usually a number of cores are arranged in the form of a matrix.

Col, Colm

International Astronomical Union abbreviations for Columba. See constellation.

colatitude

Ninety degrees minus the latitude.

cold cathode

A cathode whose operation does not depend on its temperature being above the ambient temperature.

cold-cathode gage = cold-cathode ionization gage.

cold-cathode ionization gage

A ionization gage (vacuum gage) in which the ions are produced by a discharge between two electrodes, both near room temperature. The discharge usually takes place in the presence of a magnetic field which lengthens the path of the electrons between cathode and anode.

One form of gage is a transparent tube in which the color and form of a cold-cathode discharge, without the presence of a magnetic field, give an indication of the pressure and the nature of the gas. The Philips ionization gage, or Penning gage, is a cold-cathode ionization gage in which a magnetic field is used. Various modifications of the Penning gage are named after the inventors, and certain types are referred to as magnetron vacuum gages.

cold-flow test

A test of a liquid rocket without firing it to check or verify the efficiency of a propulsion subsystem, providing for the conditioning and flow of propellants (including tank pressurization, propellant loading, and propellant feeding).

cold-pressor test

A test for measuring the response of heart and blood pressure to the stress of plunging an extremity (foot or hand) into ice water.

The normal response is an increase in both heart rate and blood pressure.

cold working

Deforming metal plastically at a temperature lower than the recrystallization temperature.

coleopter

An aircraft having an annular (barrel-shaped) wing, the engine and body being mounted within the circle of the wing.

collimate

1. To render parallel, as rays of light.

2. To adjust the line of sight of an optical instrument, such as a theodolite, in proper relation to other parts of the instrument.

collimation error

The angular error in magnitude and direction between two nominally parallel lines of sight; specifically, the angle by which the line of sight of an optical instrument or radar differs from what it should be.

collimation tower

A tower on which are mounted a visual and a radio target for use in checking the electrical axis of an antenna.

collimator

An optical device which renders rays of light parallel.

collision

An encounter between two particles that changes their existing momentum and energy conditions. See elastic collision.

The products of the collision may or may not be the same as the precollision particles. The collision may be actual contact or the close approach and deflection of the particles.

collision broadening

In spectroscopy, the broadening or spreading of an emission line, due to the interruption of the radiating process by a collision of the radiator with another particle.

In the case of cyclotron radiation, the collision will actually change the phase of the radiation. For many collisions, this has the effect of broadening the observed frequencies by an amount equal to the collision rate.

collision cross section

See cross section. See also elastic collision, coulomb collision.

collision frequency = collision rate.

collistion frequency per molecule = collision rate.

collision frequency per unit volume

The number of collisions between molecules in a gas per unit volume per unit time.

collision parameter

1. In orbit computation, the distance between a center of attraction of a central force field and the extension of the velocity vector of a moving object at a great distance from the center.

2. In gas dynamics and atomic physics, any of several parameters, such as cross section, collision rate, mean free path, etc., which provide a measure of the probability of collision.

collision rate

The average number of collisions per second suffered by a molecule or other particle moving through a gas. Also called collision frequency.

colloid

See colloidal system.

colloidal dispersion = colloidal system.

colloidal suspension = colloidal system.

colloidal system

An intimate mixture of two substances one of which, called the dispersed phase (or colloid ) is uniformly distributed in a finely divided state through the second substance, called the dispersion medium (or dispersing medium ). The dispersion medium may be a gas, a liquid, or a solid, and the dispersed phase may also be any of these, with the exception that one does not speak of a colloidal system of one gas in another. Also called colloidal dispersion, colloidal suspension.

A system of liquid or solid particles colloidally dispersed in a gas is called an aerosol. A system of solid substance or water-insoluble liquid colloidally dispersed in liquid water is called a hydrosol. There is no sharp line of demarcation between true solutions and colloidal system on the one hand, or between mere suspensions and colloidal systems on the other. When the particles of the dispersed phase are smaller than about 1 millimicron in diameter, the system begins to assume the properties of a true solution; when the particles dispersed are much greater than 1 micron, separation of the dispersed phase from the dispersing medium becomes so rapid that the system is best regarded as a suspension.

Colm

International Astronomical Union abbreviation for Columba. See constellation.

colorblind

Applied to a photographic emulsion sensitive only to blue, violet, and ultraviolet light.

color equation

In astronomy, a measure of the color sensitivity of a method of observation, equal to the color index of a class K0 star.

color excess (symbol E)

The difference between the apparent color index of a star and its true color index as computed for its stellar type.

Color excess is a measure of space reddening.

color index (symbol C)

Of a star, the numerical difference between the apparent photographic magnitude $m$_pg and the apparent photovisual magnitude m_pv or C = m_pg - m_pv

The color index is zero for class A0 stars of magnitudes between 5.5 and 6.5; it is positive for red stars and negative for bluish stars. Various other color indices can be formed by using apparent magnitudes measured in other systems. Thus, the intrinsic color index is apparent photographic magnitude minus apparent ultraviolet magnitude.

color sensitive

Referring to a photographic emulsion which is not colorblind.

An emulsion sensitive not only to blue, violet, and ultraviolet, but also to yellow and green, is called orthochromatic; if sensitive to red as well, it is called panchromatic.

color temperature

1. An estimate of the temperature of an incandescent body, determined by observing the wavelength at which it is emitting with peak intensity (its color) and using that wavelength in Wien law.

If such a body were an ideal black body, the temperature so estimated would be its true temperature and would also agree with its effective temperature; but for actual bodies, the color temperature is generally only an approximate value. Thus, the sun's color temperature is about 6100° K, a few hundred degrees hotter than most approximations of its effective temperature.

2. The temperature to which a black body radiator must be raised in order that the light it emits may match a given light source in color. [Usually expressed in Kelvin (°K).]

Columba (abbr Col, Colm)

See constellation.

column

In a structure, a body whose function is to carry compression loads to its longest dimension.

Com, Coma

International Astronomical Union abbreviations for Coma Berenices. See constellation.

Coma

International Astronomical Union abbreviations for Coma Berenices. See constellation

coma

1. The gaseous envelope that surrounds the nucleus of a comet.

2. In an optical system, a result of spherical aberration in which a point source of light, not on the axis, has a blurred, comet-shaped image.

Coma Berenices (abbr Com, Coma)

See constellation.

combination coefficient

A measure of the specific rate of disappearance of small ions due to either (a) union with neutral Aitken nuclei to form new large ions, or (b) union with large ions of opposite sign to form neutral Aitken nuclei.

combined error

A term used to specify the largest possible error of an instrument in the presence of adding or interacting effects.

Generally applied to the largest error due to the combined effect of nonlinearity and hysteresis.

combustion chamber (symbol c used as a subscript)

Any chamber for the combustion of fuel, specifically that part of the rocket engine in which the combustion of propellants takes place at high pressure. Also called chamber, firing chamber.

The combustion chamber plus the diverging section of the nozzle comprise the rocket thrust chamber.

combustion-chamber liner = inner liner.

combustion efficiency

The efficiency with which fuel is burned, expressed as the ratio of the actual energy released by the combustion to the potential chemical energy of the fuel.

combustion instability

Unsteadiness or abnormality in the combustion of fuel, as may occur, e.g., in a rocket engine.

combustion wave

A zone of burning propagated through a combustible medium.

combustor = combustion chamber.

comes (plural, comites)

The smaller star in a binary system. Also called companion.

comet

A luminous member of the solar system composed of a head, or coma, and often with a spectacular gaseous trail extending a great distance from the head.

The orbits of comets are highly elliptical.

command

A signal which initiates or triggers an action in the device which receives the signal. In computer operations also called instruction.

command control

A system whereby functions are performed as the result of a transmitted signal.

command destruct

A command control system that destroys a flightborne test rocket, actuated on command of the range safety officer whenever the rocket performance indicates a safety hazard.

command guidance

The guidance of a spacecraft or rocket by means of electronic signals sent to receiving devices in the vehicle.

common item

An item of supply used in two or more systems, subsystems, or pieces of support equipment, including related components and spares.

communications satellite

A satellite designed to reflect or relay electromagnetic signals used for communication.

commutation

Sequential sampling, on a repetitive timesharing basis, of multiple data sources for transmitting or recording, or both, on a single channel.

commutation rate

Number of commutator inputs sampled per second.

commutator

A device used to accomplish time division multiplexing by repetitive sequential switching.

companion

The smaller body in a physical double-star system. See binary star. Also called comes.

companion body

A nose cone, last-stage rocket, or other body that orbits along with an earth satellite. Compare afterbody.

comparator

In computer operations, a device or circuit for comparing information from two sources.

compass

1. An instrument for indicating a horizontal reference direction, specifically a magnetic compass.

2. Referring to or measured from compass north.

compass meridian

See meridian.

compass north

The direction north as indicated by a magnetic compass; the reference direction for measurement of compass directions.

compatibility

1. A characteristic ascribed to a major subsystem that indicates it functions well in the overall system.

2. Also applied to the overall system with reference to how well its various subsystems work together, as in the vehicle has good compatibility.

3. Also applied to materials which can be used in conjunction with other materials which can be used in conjunction with other materials and not react with each other under normal operating conditions.

compensation signals

In telemetry, a signal recorded on a tape, along with the data and in the same track as the data, used during the playback of data to correct electrically the effects of tape-speed errors.

compile

In computer terminology, to assemble the necessary subroutines into a main routine for a specific problem.

complement

1. An angle equal to 90° minus a given angle.

Thus, 50° is the complement of 40°, and the two are said to be complementary. See explement.

2. The true complement of any quantity in positional notation, i.e., the quantity which, when added to the first quantity, gives the least quantity containing one more place.

3. The base-minus-one complement of any quantity in positional notation; i.e., the quantity which, when added to the first quantity, gives the largest quantity containing the same number of places.

In many computing machines a negative quantity is represented as a complement of the corresponding positive quantity.

complementary angle = complement.

complementation

In Boolean algebra, an operation in which items are described by stating that they do not belong to a particular class or classes. See NOT circuit.

complementor

In computers, a device which performs a function corresponding to the operation of complementation.

complex

1. Short for launch complex, as in Complex 25B at Cape Kennedy.

2. Pertaining to a magnitude composed of a real number and an imaginary number.

complexity units

In reliability studies of electronic devices, an approximate figure of merit for complexity based on the sum of the number of tubes plus the number of relays in a unit or system. The total number of parts is roughly 10 times the number of complexity units.

component

An article which is a self-contained element of a complete operating unit and performs a function necessary to the operation of that unit.

composite materials

Structural materials of metals, ceramics, or plastics with built-in strengthening agents which may be in the form of filaments, foils, powders, or flakes of a different compatible material.

composite propellant

A solid rocket propellant consisting of a fuel and an oxidizer neither of which would burn without the presence of the other.

compound centripetal acceleration = coriolis acceleration.

compressed air illness = caisson disease.

compressibility

1. The property of a substance, as air, by virtue of which its density increases with increase in pressure.

2. = coefficient of compressibility.

In aerodynamics, this property of the air is manifested especially at high speeds (speeds approaching that of sound and higher speeds). Compressibility of the air about an aircraft may give rise to buffeting, aileron buzz, shifts in trim, and other phenomena not ordinarily encountered at low speeds, known generally as compressibility effects.

compressibility burble

A region of disturbed flow, produced by, and rearward of, a shock wave. See burble.

compressible flow

In aerodynamics, flow at speeds sufficiently high that density changes in the fluid cannot be neglected.

compression

1. = ellipticity. See flattening.

2. More generally, the act of compressing, pressing together; as in compression waves, compression ratio.

compressional wave

In acoustics, a wave in an elastic medium which causes an element of the medium to change its volume without undergoing rotation. Mathematically, a compressional wave is one whose velocity field has zero curl. Also called compression wave.

A compressional plane wave is a longitudinal wave.

compressor

A machine for compressing air or other fluid.

Compressors are distinguished (1) by the manner in which fluid is handled or compressed, as the axial flow, centrifugal, double-entry, free-vortex, mixed-flow, single-entry, and supersonic compressor; or (2) by the number of stages, as the multistage or single-stage compressor. See individual entries on the different types.

compressor blade

Either a rotor blade or a stator blade in an axial-flow compressor; sometimes used restricitevly (and ambiguously) for a compressor rotor blade. Compare impeller vane.

Compton effect

The decrease in frequency and increase in wavelength of X-rays or gamma rays when scattered by free electrons. Also called Compton recoil effect.

Compton electron

An orbital electron of an atom which has been ejected from its orbit as a result or an impact by a high-energy quantum of radiation (X-ray or gamma ray). Also called Compton recoil electron.

Compton recoil effect = Compton effect.

Compton recoil electron = Compton electron.

Compton wavelength (symbol _c)

Of a particle, the distance h/mc, where h is the Planck constant, m is the mass of the particle, and c is the velocity of light.

The Compton wavelength of the electron (symbol _c) is 2.4261 x 10^-10 centimeter; of the proton (symbol _cp) is 1.32140 x 10^-13 centimeter.

computer

1. A machine for carrying out calculations and performing specified transformations on information. Also called computing machinery.

2. One who computes, or who operates a computer.

computing efficiency

Of a computer, the percentage of the successful computation time during a defined period to the total time in that period. Also called operating ratio.

computing machinery

Machinery which can take in, give out, and store information, and also perform arithmetic and logical operations with the information. Usually called computer.

condensation

1. The physical process by which a vapor becomes a liquid or solid; the opposite of evaporation.

2. Specifically, in meteorology, the transformation from vapor to liquid. See sublimation.

condensation coefficient

The ratio of condensation rate to impingement rate.

condensation nucleus

1. A particle, either liquid or solid, upon which condensation of vapor begins.

2. Specifically, in meteorology, a particle upon which condensation of water begins in the atmosphere.

condensation rate

The number per square centimeter per second at which molecules condense on a surface.

condensation shock = condensation shock wave.

condensation shock wave

A sheet of discontinuity associated with a sudden condensation and fog formation in a field of flow. It occurs, e.g., on a wing, where a rapid drop in pressure causes the temperature to drop considerably below the dew point. Also called condensation shock.

condensation trail

A visible trail of condensed water vapor or ice particles left behind an aircraft, an airfoil, etc. in motion through the air. Also called a contrail or vapor trail.

There are three kinds of condensation trails: the aerodynamic type, caused by reduced pressure of the air in certain areas as it flows past the aircraft; the convection type, caused by the rising of air warmed by an engine; and the engine-exhaust, or exhaust-moisture, type, formed by the ejection of water vapor from an engine into a cold atmosphere.

conductance

1. In electricity, the ratio of the current flowing through an electric circuit to the difference of potential between the ends of the circuit, the reciprocal of resistance. See conductivity.

2. In vacuum systems, the throughput Q under steady-state conservative conditions divided by the measured difference in pressure p between two specified cross sections inside a pumping system: G = Q/(p₁-p₂).

conduction

The transfer of energy within and through a conductor by means of internal particle or molecular activity and without any net external motion.

Conduction is to be distinguished from convection (of heat) and radiation (of all electromagnetic energy).

conduction band

A range of states in the energy spectrum of a solid in which electrons can move freely.

conductive equilibrium = isothermal equilibrium.

conductivity

1. The ability to transmit, as electricity, heat, sound, etc.

2. A unit measure of electrical conduction; the facility with which a substance conducts electricity, as represented by the current density per unit electrical-potential gradient in the direction of flow.

Electrical conductivity is the reciprocal of electrical resistivity and is expressed in units such as mhos (reciprocal ohms) per centimeter. It is an intrinsic property of a given type of material under given physical conditions (dependent mostly upon temperature). Conductance, on the other hand, varies with the dimensions of the conducting system, and is the reciprocal of the electrical resistance.

conductor

A substance or entity which transmits electricity, heat, sound, etc.

cone

1. A geometric configuration having a circular bottom and sides tapering off to an apex (as in nose cone).

2. A type of light-sensitive cell in the retina. Cones are involved in color vision, high visual acuity, and photopic vision.

cone of escape

A hypothetical cone in the exosphere, directed vertically upward, through which an atom or molecule would theoretically be able to pass to outer space without a collision, that is, in which the mean free path is infinite. See fringe region.

Such a cone would open wider with increasing altitude above the critical level of escape, and would be nonexistent below the critical level of escape.

confidence interval

In statistics, a range of values which is believed to include, with a preassigned degree of confidence (confidence level), the true characteristic of the lot or universe a given percentage of the time.

For example: 95-percent confidence limits for a sample of 10 with a ratio of successes to total number tested of 0.9 (9 successes and 1 failure) would be 0.54 to 1.0. That is, even with an observed success ratio of 0.9 (90 percent) the best that can be said is that the true ratio lies between 0.54 (54 percent) and 1.0 (100 percent) an estimated 95 percent of the time.

confidence level

In statistics, the degree of desired trust or assurance in a given result.

A confidence level is always associated with some assertion and measures the probability that a given assertion is true. For example, it could be the probability that a particular characteristic will fall within specified limits, i.e., the chance that the true value of P lies between P = a and P = b. See confidence interval.

confidence limits

In statistics, the upper and lower extremes of the confidence interval.

configuration

1. Relative position or disposition of various things, or the figure or pattern so formed.

2. A geometric figure, usually consisting principally of points and connecting lines.

3. = planetary configuration.

4. A particular type of a specific aircraft, rocket, etc., which differs from others of the same model by virtue of the arrangement of its components or by the addition or omission of auxiliary equipment as long-range configuration, cargo configuration.

Some writers use constellation as a synonym for configuration in referring to the relative positions of spacecraft to each other, as in a rendezvous maneuver, or to celestial bodies. This usage should be discouraged.

confluence

The rate at which adjacent flow is converging along an axis oriented normal to the flow at the point in question. It is the opposite of difluence. Compare convergence.

conformal

Having correct angular representation.

conic

1. A curve formed by the intersection of a plane and a right circular cone. Originally called conic section.

The conic sections are the ellipse, the parabola, and the hyperbola, curves that are used to describe the path or bodies moving in space. The circle is a special case of the ellipse, an ellipse with an eccentricity of zero.
The conic is the locus of all points the ratio of whose distances from a fixed point, called the focus, and a fixed line, called the directrix, is constant.

2. In reference to satellite orbital parameters, without consideration of the perturbing effects of the actual shape or distribution of mass of the primary.

Thus, conic perigee is the perigee the satellite would have if all the mass of the primary were concentrated at its center.

conical beam

The radar beam produced by conical scanning methods.

This type of beam has an advantage over that produced by a single radiating element placed at the focus of a parabolic reflector in that much greater angular accuracy is possible in locating targets.

conical scanning

Scanning in which the direction of maximum radiation generates a cone whose vertex angle is of the order of the beam width. Such scanning may be either rotating or nutating, according as the direction of polarization rotates or remains unchanged.

conic section

The original name for conic.

conjunction

1. The situation of two celestial bodies having either the same celestial longitude or the same sidereal hour angle. Compare opposition, quadrature.

A planet is at superior conjunction if the sun is between it and the earth; at inferior conjunction if it is between the sun and the earth.

2. The time at which conjunction, as defined in sense 1, takes place.

conservation of angular momentum

The principle that absolute angular momentum is a property which cannot be created or destroyed by can only be transferred from one physical system to another through the agency of a net torque on the system. As a consequence, the absolute angular momentum of an isolated physical system remains constant.

The principle of conservation of angular momentum can be derived from the Newton second law of motion.

conservation of energy

The principle that the total energy of an isolated system remains constant if no interconversion of mass and energy takes place.

This principle takes into account all forms o