Aerospace Science and Technology Dictionary A Page

Aerospace Science
&
Technology Dictionary

A

A stars

NASA Thesaurus A class of stars in which spectral absorption lines for the Balmer series of hydrogen appear most prominently along with ionized metals. The A class serves as a central point from which other stellar spectra range. They are white stars ranging in temperature from 7000-9500 degrees Kelvin.

A-display

NASA SP-7, 1965 In radar, a display in which targets appear as vertical deflections from a line representing a time base. Also called A-scan or A-scope .
Target distance is indicated by the horizontal position of the deflection from one end of the time base. The amplitude of the vertical deflection is a function of the signal intensity.

A-scan

NASA SP-7, 1965 = A-display.

A-scope

NASA SP-7, 1965 = A-display.

A-station

NASA SP-7, 1965 In loran, the designation applied to the transmitting station of a pair, the signal of which always occurs less than half a repetition period after the next preceding signal and more than half a repetition period before the next succeeding signal of the other station of the pair, designated a B-station.

A-trace

NASA SP-7, 1965 The first trace of an oscilloscope, as the upper trace of a loran indicator.

A/E ratio

NASA SP-7, 1965 = absorptivity-emissivity ratio.

AAAS

Space Flight Glossary - JPL American Association for the Advancement of Science.

AACS

Space Flight Glossary - JPL Attitude and Articulation Control Subsystem onboard a spacecraft.

AAS

Space Flight Glossary - JPL American Astronomical Society.

aberration

NASA Thesaurus / NASA SP-7, 1965 1. In astronomy, the apparent angular displacement of the position of a celestial body in the direction of motion of the observer, caused by the combination of the velocity of the observer and the velocity of light. See constant of aberration, planetary aberration. Compare parallax.
2. In optics, a specific deviation from perfect imagery, as, for example: spherical aberration, coma, astigmatism, curvature of field, and distortion.

aberration constant

NASA SP-7, 1965 = constant of aberration

abiogenesis

NASA Thesaurus The development of living organisms from lifeless matter.

ablate

NASA SP-7, 1965 To carry away; specifically, to carry away heat generated by aerodynamic heating, from a vital part, by arranging for its absorption in a nonvital part, which may melt or vaporize, then fall away taking the heat with it. See heat shield, ablation.

ablating materials

NASA Thesaurus / NASA SP-7, 1965 See ablative materials.

ablation

NASA Thesaurus / NASA SP-7, 1965 The removal of surface material from a body by vaporization, melting, chipping, or other erosive process; specifically, the intentional removal of material from a nose cone or spacecraft during high-speed movement through a planetary atmosphere to provide thermal protection to the underlying structure. See ablative materials.

ablation

Glossary of Hydrologic Terms - NOAA The process by which ice and snow waste away owing to melting and evaporation.

ablative materials

NASA Thesaurus / NASA SP-7, 1965 A material, especially a coating material, designed to provide thermal protection to a body in a fluid stream through loss of mass.
Ablating materials are used on the surfaces of some reentry vehicles to absorb heat by removal of mass, thus blocking the transfer of heat to the rest of the vehicle and maintaining temperatures within design limits. Ablating materials absorb heat by increasing in temperature and changing in chemical or physical state. The heat is carried away from the surface by a loss of mass (liquid or vapor). The departing mass also blocks part of the convective heat transfer to the remaining material in the same manner as transpiration cooling.

ablative nose cones

NASA Thesaurus / NASA SP-7, 1965 Nose cones designed to reduce heat transfer to the internal structure by the use of an ablative material.

ablatively

NASA SP-7, 1965 By a process of ablation, as in ablatively cooled .

ablator

NASA SP-7, 1965 A material designed to provide thermal protection through ablation.

abort

NASA SP-7, 1965 1. To cut short or break off an action, operation, or procedure with an aircraft, space vehicle, or the like, especially because of equipment failure, as to abort a mission, the launching was aborted.
2. An aircraft, space vehicle, or the like that aborts.
3. An act or instance of aborting.

abrasion

NASA Thesaurus The surface loss of a material due to frictional forces.

abrasives

NASA Thesaurus Rocks, minerals, or other substances that, owing to their superior hardness, toughness, consistency, or other properties, are suitable for grinding, cutting, polishing, scouring, or similar use.

Abridged Nautical Almanac

NASA SP-7, 1965 See Nautical Almanac.

absolute

NASA SP-7, 1965 1. Pertaining to a measurement relative to a universal constant or natural datum, as absolute coordinate system, absolute altitude, absolute temperature.
2. Complete, as in absolute vacuum.

absolute altimeter

NASA SP-7, 1965 An instrument intended to give acceptably accurate, direct indications of absolute altitude.

absolute altitude

NASA SP-7, 1965 Altitude above the actual surface, either land or water, of a planet or natural satellite. Compare true altitude.

absolute coordinate system

NASA SP-7, 1965 An inertial coordinate system which is fixed with respect to the stars.
In theory, no absolute coordinate system can be established because the reference stars are themselves in motion. In practice, such a system can be established to meet the demands of the problem concerned by the selection of appropriate reference stars.

absolute delay

NASA SP-7, 1965 1. The time interval between the transmission of sequential signals. Also called delay .
2. Specifically, in loran, the time interval between transmission of a signal from the A-station and transmission of the next signal from the B-station.

absolute humidity

NASA SP-7, 1965 The amount of water vapor actually present in unit quantity of a gas, generally expressed as mass of water vapor per unit volume of gas + water vapor, e.g., as grains per cubic foot.

absolute index of refraction

NASA SP-7, 1965 = index of refraction (sense 1).

absolute instabilities

Plasma Physics and Fusion Energy Glossary A class of plasma instabilities growing exponentially with time at a point in space, in contrast to convective instabilities.

absolute instrument

NASA SP-7, 1965 An instrument whose calibration can be determined by means of physical measurements on the instrument. Compare secondary instrument.

absolute magnitude

NASA SP-7, 1965 (symbol M)
1. A measure of the brightness of a star equal to the magnitude the star would have at a distance of 10 parsecs from the observer.

where m is apparent magnitude, and p is the parallax of the star (in seconds of arc). Absolute magnitudes may be visual, photographic, etc., according to the way in which the apparent magnitude was measured.
2. The stellar magnitude any meteor would have if placed in the observer's zenith at a height of 100 kilometers.

absolute magnitude

IMO Meteor Glossary The stellar magnitude any meteor would have if placed in the observer's zenith at a height of 100 km.

absolute magnitude (Ho)

Comet Glossary - JPL The brightness of a comet when it is at 1 AU from both the Earth and Sun. As this virtually never happens, this quantity is calculated from the comet's light curve. Unfortunately, this quantity is far from absolute. It can be different pre- and post-perihelion. It can also change from apparition to apparition (for periodic comets).

absolute manometer

NASA SP-7, 1965 1. A gas manometer whose calibration, which is the same for all ideal gases, can be calculated from the measurable physical constants of the instrument.
2. A manometer that measures absolute pressure.

absolute motion

NASA SP-7, 1965 Motion relative to a fixed point. See absolute coordinate system, note.

absolute pressure

NASA SP-7, 1965 In engineering literature, a term used to indicate pressure above the absolute zero value of pressure that theoretically obtains in empty space or at the absolute zero of temperature as distinguished from gage pressure.
In high-vacuum technology, pressure is understood to correspond to absolute pressure, not gage pressure, and therefore the term absolute pressure is rarely used.

absolute refractive index

NASA SP-7, 1965 = index of refraction (sense 1)

absolute system of units

NASA SP-7, 1965 1. A system of units in which a small number of units are chosen as fundamental, and all other units are derived from them.
2. Specifically, a system of electrical units put into effect by international agreement on 1 January 1948.
Prior to 1 January 1948 the international system was in effect; the two systems can be converted by the following relationships:
1 mean international ohm = 1.00049 absolute ohm
1 mean international volt = 1.00034 absolute volt.

"Electric units, called "international," for current and resistance had been introduced by the International Electrical Congress held in Chicago in 1893, and the definitions of the international" ampere and the "international" ohm were confirmed by the International Conference of London in 1908.
Although it was already obvious on the occasion of the 8th CGPM (1933) that there was a unanimous desire to replace those "international" units by so-called "absolute" units, the official decision to abolish them was only taken by the 9th GPM (1948), which adopted for the unit of electric current, the ampere," which see.

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

absolute temperature

NASA SP-7, 1965 Temperature value relative to absolute zero.

absolute temperature

From Stargazers to Starships Glossary - GSFC Temperature in degrees centigrade (also known in this case as "degrees Kelvin" K°) measured from the absolute zero of -273.1° C, the temperature at which all atomic and molecular motions are expected to cease.

absolute temperature scale

NASA SP-7, 1965 A temperature scale based upon the value zero as the lowest possible value. Thus, all obtainable temperatures are positive. The Kelvin and Rankine scales are absolute scales.

absolute vacuum

NASA SP-7, 1965 A void completely empty of matter. Also called perfect vacuum.
An absolute vacuum is not obtainable.

absolute vorticity

NASA SP-7, 1965 1. The vorticity of a fluid particle expressed with respect to an absolute coordinate system. 2. The vertical component of the absolute vorticity (as defined above).

absolute zero

NASA Thesaurus / NASA SP-7, 1965 The theoretical temperature at which molecular motion vanishes and a body would have no heat energy; the zero point of the Kelvin and Rankine temperature scales.
Absolute zero may be interpreted as the temperature at which the volume of a perfect gas vanishes or, more generally, as the temperature of the cold source which would render a Carnot cycle 100 percent efficient. The value of absolute zero is now estimated to be - 273.15° Celsius, -459.67° Fahrenheit, 0° Kelvin, and 0° Rankine.

absorptance

NASA Thesaurus / NASA SP-7, 1965 (absorbtance) (symbol A, a, or

) The ratio of the radiant flux absorbed by a body to that incident upon it. Also called absorption factor. Compare absorptivity. Total absorptance refers to absorptance measured over all wavelengths. Spectral absorptance refers to absorptance measured at a specified wavelength.

absorption

Plasma Physics and Fusion Energy Glossary In plasma physics, the loss of (electromagnetic) energy to a medium. For instance, an electromagnetic wave which propagates through a plasma will set the electrons into motion. If the electrons make collisions with other particles, they will absorb net energy from the wave.

absorption

NASA Thesaurus / NASA SP-7, 1965 1. The process by which radiant energy is absorbed and converted into other forms of energy. See attenuation.
Absorption takes place only after the radiant flux enters a medium and thus acts only on the entering flux not on the incident flux, some of which may be reflected at the surface of the medium. A substance which absorbs energy may also be a medium of refraction, diffraction, or scattering; these processes, however, involve no energy retention or transformation and are to be clearly differentiated from absorption.
2. In general, the taking up or assimilation of one substance by another. See sorption, adsorption.
3. In vacuum technology, gas entering into the interior of a solid.

absorption band

NASA SP-7, 1965 A range of wavelengths (or frequencies) in the electromagnetic spectrum within which radiant energy is absorbed by a substance. See absorption spectrum.
When the absorbing substance is a polyatomic gas, an absorption band actually is composed of a group of discrete absorption lines which appear to overlap. Each line is associated with a particular mode of vibration or rotation induced in a gas molecule by the incident radiation.
The absorption bands of oxygen and ozone are often referred to in the literature of atmospheric physics.
The important bands for oxygen are: (a) the Hopfield bands, very strong, between about 670 and 1000 angstroms in the ultraviolet; (b) a diffuse system between 1019 and 1300 angstroms; (c) the Schumann-Runge continuum, very strong, between 1350 and 1760 angstroms; (d) the Schumann-Runge bands between 1760 and 1926 angstroms; (e) the Herzberg bands between 2400 and 2600 angstroms; (f) the atmospheric bands between 5380 and 7710 angstroms in the visible spectrum; and (g) a system in the infrared at about 1 micron.
The important bands for ozone are: (a) the Hartley bands between 2000 and 3000 angstroms in the ultraviolet, with a very intense maximum absorption at 2550 angstroms; (b) the Huggins bands, weak absorption between 3200 and 3600 angstroms; (c) the Chappius bands, a weak diffuse system between 4500 and 6500 angstroms in the visible spectrum; and (d) the infrared bands centered at 4.7, 9.6 and 14.1 microns, the latter being the most intense.

absorption coefficient

NASA SP-7, 1965

(symbol

)
1. A measure of the amount of normally incident radiant energy absorbed through a unit distance or by a unit mass of absorbing medium. Compare transmission coefficient.
The absorption coefficient is frequently identified as follows:

where I_Lx is the flux density of radiation of wavelength L, initially of flux density I_L0, after traversing a distance x in some absorbing medium. (Substitute L for lambda.)
2. In acoustics, the ratio of the sound energy absorbed by a surface of a medium (or material) exposed to a sound field or sound radiation to the sound energy incident on the surface. The stated values of this ratio are to hold for an infinite area of the surface. The conditions under which measurements of absorption coefficients are made are to be stated explicitly.
Three types of absorption coefficients associated with three methods of measurement are: chamber absorption coefficient, obtained in a certain reverberation chamber; free-wave absorption coefficient, obtained when a plane, progressive, sound wave is incident on the surface of the medium; sabine absorption coefficient, obtained when the sound is incident from all directions on the sample.

absorption coefficient:

Plasma Physics and Fusion Energy Glossary Measures the degree of wave absorption (see Absorption above); defined as the fraction of wave energy lost as the wave travels a unit distance.

absorption cooling

NASA Thesaurus Refrigeration in which cooling is effected by the expansion of liquid ammonia into gas and the absorption of the gas by water. The ammonia is reused after the water evaporates.

absorption cross sections

NASA Thesaurus / NASA SP-7, 1965 In radar, the ratio of the amount of power removed from a beam by absorption of radio energy by a target to the power in the beam incident upon the target. Compare scattering cross sections. See cross sections. Used for capture cross sections.

absorption factor

NASA SP-7, 1965 = absorptance.

absorption line

NASA SP-7, 1965 A minute range of wavelength (or frequency) in the electromagnetic spectrum within which radiant energy is absorbed by the medium through which it is passing. Each line is associated with a particular mode of electronic excitation induced in the absorbing atoms by the incident radiation. See absorption spectrum, spectral line, telluric lines, Fraunhofer lines, absorption band.

absorption spectra

NASA Thesaurus The arrays of absorption lines and absorption bands which result from the passage of radiant energy from a continuous source through a selectively absorbing medium cooler than the source. Used for absorption bands and spectral absorption.

absorption spectrum

NASA SP-7, 1965 The array of absorption lines and absorption bands which results from the passage of radiant energy from a continuous source through a selectively absorbing medium cooler than the source. See electromagnetic spectrum.
The absorption spectrum is a characteristic of the absorbing medium, just as an emission spectrum is a characteristic of a radiator.
An absorption spectrum formed by a monatomic gas exhibits discrete dark lines, whereas that formed by a polyatomic gas exhibits ordered arrays (bands) of dark lines, which appear to overlap. This type of absorption is ften referred to as line absorption. The spectrum formed by a selectively absorbing liquid or solid is typically continuous in nature (continuous absorption).

absorption-emission pyrometer

NASA SP-7, 1965 A thermometer for determining gas temperature from measurement of the radiation emitted by a calibrated reference source before and after this radiation has passed through and been partially absorbed by the gas. Both measurements are made over the same wavelength interval.

absorptive index

NASA SP-7, 1965 The imaginary part of the complex index of refraction of a medium. It represents the energy loss by absorption and has a nonzero value for all media which are not dielectrics. Also called index of absorption . Compare absorption coefficient.

absorptive power

NASA SP-7, 1965 The total flux of radiant energy absorbed in a unit area of absorbing substance; expressed, for example, in ergs per square centimeter per second or in watts per square centimeter.

absorptivity

NASA Thesaurus / NASA SP-7, 1965 (symbol

)
The capacity of a material to absorb incident radiant energy, measured as the absorptance of a specimen of the material thick enough to be completely opaque, and having an optically smooth surface.

absorptivity-emissivity ratio

NASA SP-7, 1965 In space applications, the ratio of absorptivity for solar radiation of a material to its infrared emissivity. Also called A/E ratio.

abundance

NASA Thesaurus The mean concentration of an element in a geochemical reservoir, e.g., the abundance of Ni in meteorites or the crustal abundance of oxygen. Also used for the for relative average content, e.g., the order of abundance of elements in the Earth's crust is O, Si, AL, Fe, Ca, etc. Used for element abundance.

AC

Space Flight Glossary - JPL alternating current.

AC generators

NASA Thesaurus Generators for the production of alternating-current power. Used for alternating current generators and alternators (generators).

accelerated life tests

NASA Thesaurus Methods designed to approximate, in a short time, the deteriorating effects under normal long-term service conditions.

acceleration (physics)

NASA Thesaurus / NASA SP-7, 1965 1. The rate of change of velocity.
2. The act or process of accelerating, or the state of being accelerated. Negative acceleration is called deceleration . Used for boost and G force.

acceleration of gravity

NASA SP-7, 1965 (symbol g)
By the International Gravity Formula,

g = 978.0495 [1 + 0.0052892 sin

²(p) - 0.0000073 sin² (2p)] centimeters per second squared at sea level at latitude p. See gravity.
The standard value of gravity, or normal gravity, g, is defined as g_o=980.665 centimeters per second squared, or 32.1741 feet per second squared. This value corresponds closely to the International Gravity Formula value of g at 45° latitude at sea level.

accelerator

NASA SP-7, 1965 Short for particle accelerator .

accelerators

NASA Thesaurus Machines that ionize gases and electrically accelerate the ions onto targets.

accelerometers

NASA Thesaurus / NASA SP-7, 1965 Transducers that measure acceleration or gravitational forces capable of imparting acceleration.
An accelerometer usually uses a concentrated mass (seismic mass) which resists movement because of its inertia. The displacement of the seismic mass relative to its supporting frame or container is used as a measure of acceleration.

acceptor

NASA SP-7, 1965 In transistors, the P-type semiconductor, the electrode containing trivalent impurities (boron, gallium, or indium) to increase the number of holes which can accept electrons. Contrast with donor.

access control

NASA Thesaurus Hardware or software features, operating procedures, or management procedures designed to permit authorized access to a computer system.

accidental error

NASA SP-7, 1965 In experimental observations, an error which does not always recur when an observation is repeated under the same conditions. Contrast systematic errors.

acclimatization

NASA Thesaurus / NASA SP-7, 1965 The adjustments of a human body or other organism to a new environment; the bodily changes which tend to increase efficiency and reduce energy loss. Compare adaptation, accustomization.

accommodation coefficient

NASA Thesaurus / NASA SP-7, 1965 (symbol

)
The ratio of the average energy actually transferred between a surface and impinging gas molecules which are scattered by the surface to the average energy which would theoretically by transferred if the impinging molecules reached complete thermal equilibrium with the surface before leaving the surface or

a = (E

_r-E _i)/E_s-E_i) where a is the accommodation coefficient, Er is the energy carried away from unit surface area per second by the scattered or re-evaporated molecules, Ei is the energy per unit surface area per second carried toward the surface by the impinging molecules, and Es is the energy per unit surface area per second which would be carried away by the molecules if the molecules reached complete thermal equilibrium with the surface before leaving.

accounting

NASA Thesaurus The practice and system of recording and summarizing business and financial transactions, and reporting as well as verifying and analyzing their results.

accretion

High Energy Astrophysics Dictionary- GSFC Accumulation of dust and gas into larger bodies such as stars, planets and moons.

accretion disks

NASA Thesaurus Rotating disks of matter surrounding an astronomical object, such as a star, galactic nucleus, black hole, etc., which is accumulated gravitationally by the object.

accretion disks

Spacetime Wrinkles Glossary In a binary system containing a star and a compact object (white dwarf, neutron star, or black hole) gas may flow from the star to the compact object. According to the theoretical model, the gas will spiral in and fall to the surface of the compact object creating a flow of matter in the shape of a disk. It is generally believed that this model explains many features of X-ray pulsars

accumulator

NASA Thesaurus / NASA SP-7, 1965 1. A device or apparatus that accumulates or stores up, as: (a) a contrivance in a hydraulic system that stores fluid under pressure; (b) a device sometimes incorporated in the fuel system of a gas-turbine engine to store up and release fuel under pressure as an aid in starting; (c) an electrical storage battery (British usage).
2. In computer technology, a device which stores a number and upon receipt of another number adds it to the number already stored and stores the sum. See counter.

accuracy

NASA Thesaurus The degree of agreement of the measurements with the true value of the magnitude of the quantity measured. Used for error band and fidelity.

accustomization

NASA SP-7, 1965 The process of learning the techniques of living with a minimum of discomfort in an extreme or new environment. Compare acclimatization, adaptation.

ACE

SOHO Glossary - GSFC Advanced Composition Explorer. A spacecraft studying the heliosphere and cosmic rays.

ACEE program

NASA Thesaurus A NASA program started in 1975 to reduce fuel consumption for transport aircraft through the study of structural and aerodynamic energy efficiency as well as engine energy efficiency consisting of engine component improvement, new energy efficient engines, and advanced turbopropellers. The acronym stands for aircraft energy efficiency. Used for Aircraft Energy Efficiency program and energy efficiency transport program.

acetylation

NASA Thesaurus Substitution of an acetyl radical for an active hydrogen. Specifically, formation of cellulose acetate from cellulose. Used for acetation.

acid rain

NASA Thesaurus Low pH rainfall resulting from atmospheric reactions of aerosols containing chlorides and sulfates (or other negative ions).

acidosis

NASA Thesaurus Reduction of alkali reserves due to an excess of acid metabolites.

aclinic line

NASA SP-7, 1965 The line through those points on the earth's surface at which magnetic dip is zero. The aclinic line is a particular case of an isoclinic line. Also call dip equator, magnetic equator. Compare agonic line, geomagnetic equator.

acoustic delay lines

NASA Thesaurus / NASA SP-7, 1965 Devices used in a communications link or a computer memory in which the signal is delayed by the propagation of a sound wave. Also called sonic delay lines .

acoustic description

NASA SP-7, 1965 The change of speed of sound with frequency.

acoustic emission

NASA Thesaurus The stress and pressure waves generated during dynamic processes in materials and used in assessing structural integrity in machined parts.

acoustic excitation

NASA Thesaurus / NASA SP-7, 1965 The process of inducing vibration in a structure by exposure to sound waves.

acoustic generator

NASA SP-7, 1965 A transducer which converts electric, mechanical, or other forms of energy into sound.

acoustic levitation

NASA Thesaurus Method by which molten materials in space are suspended during processing experiments in the low gravity environment. Also, the use of very intense sound waves to keep a body suspended, thereby eliminating any container contact.

acoustic Mach meter

NASA SP-7, 1965 A device which obtains data on sound propagation for the calculation of Mach number.
Some acoustics Mach meters measure transit time or velocity of a sound pulse; others measure an angle, as the angle of the Mach cone.

acoustic measurement

NASA Thesaurus Measurement of properties, quantities, or conditions of acoustical, i.e., mechanical waves. Used for sound measurement.

acoustic microscopes

NASA Thesaurus Instruments which use acoustic radiation at microwave frequencies to allow visualization of microscopic detail exhibited in elastic properties of objects. Used for scanning laser acoustic microscope (SLAM).

acoustic radiation pressure

NASA SP-7, 1965 A unidirectional, steady-state pressure exerted upon a surface exposed to a sound wave.

acoustic refraction

NASA SP-7, 1965 The process by which the direction of sound propagation is changed due to spatial variation in the speed of sound in the medium.

acoustic retrofitting

NASA Thesaurus Modification, especially of aircraft, to effect noise reduction; specifically, the introduction of absorber materials and jet noise silencers.

acoustic streaming

NASA Thesaurus / NASA SP-7, 1965 Unidirectional flow currents in a fluid that are due to the presence of sound waves.

acoustic velocity

NASA Thesaurus / NASA SP-7, 1965 (symbol

)
=speed of sound

acoustic vibration

NASA SP-7, 1965 With respect to operational environments, vibrations transmitted through a gas. These vibrations may be subsonic, sonic, and ultrasonic.

acoustic wave

NASA SP-7, 1965 = sound wave.

acoustic, acoustical

NASA SP-7, 1965 Containing, producing, arising from, actuated by, related to, or associated with sound.
Acoustic is used to modify terms that designate an object, or physical characteristics, associated with sound waves; acoustical is used when the term being qualified does not designate explicitly something that has such properties, dimensions, or physical characteristics.
The following terms are examples of those modified by acoustic; impedance, intertance, load (radiation field), output (sound power), energy, wave, medium, signal, conduit, absorptivity, transducer.
The following examples do not have the requisite physical characteristics and therefore take acoustical; society, method, engineer, school, glossary, symbol, problem, measurement, point of view, device.
As illustrated, the generic term is usually modified by acoustical, whereas the specific technical term calls for acoustic.

acoustics

NASA Thesaurus / NASA SP-7, 1965 1. The study of sound, including its production, transmission, and effects.
2. Those qualities of an enclosure that together determine its character with respect to distinct hearing.

acquired immunodeficiency syndrome

NASA Thesaurus A condition caused by the human immunodeficiency virus (HIV) attacking the human body's T-cells, thereby rendering an infected individual defenseless against diseases.

acquisition

NASA SP-7, 1965 1. The process of locating the orbit of a satellite or trajectory of a space probe so that tracking or telemetry data can be gathered.
2. The process of pointing an antenna or telescope so that it is properly oriented to allow gathering of tracking or telemetry data from a satellite or space probe.

acquisition and tracking radar

NASA SP-7, 1965 A radar set that locks onto a strong signal and track the object reflecting the signal.

actinic

NASA SP-7, 1965 Pertaining to electromagnetic radiation capable of initiating photochemical reactions, as in photography or the fading of pigments.
Because of the particularly strong action of ultra violet radiation on photochemical processes, the term has come to be almost synonymous with ultraviolet, as in actinic rays.

actinic balance

NASA SP-7, 1965 =bolometer.

actinide series

NASA Thesaurus The series of elements beginning with actium, element No. 89, and continuing through lawrencium, element No. 103.

actinogram

NASA SP-7, 1965 The record of a recording actinometer.

actinograph

NASA SP-7, 1965 A recording actinometer.

actinometer

NASA Thesaurus / NASA SP-7, 1965 The general name for any instrument used to measure the intensity of radiant energy, particularly that of the sun. See actinometry. See also bolometer, dosimeter, photometer, radiometer.
Actinometers may be classified, according to the quantities which they measure, in the following manner: (a) pyrheliometer, which measures the intensity of direct solar radiation; (b) pyranometer, which measure global radiation (the combined intensity of direct solar radiation and diffuse sky radiation); and (c) pyrgeometer, which measures the effective terrestrial radiation.

actinometry

NASA SP-7, 1965 The science of measurement of radiant energy, particularly that of the sun, in its thermal, chemical, and luminous aspects. Compare photometry. See actinometer.

activated sludge

NASA Thesaurus A semiliquid mass removed from the liquid flow of sewage and subjected to aeration and aerobic microbial action. The end product is dark to golden brown, partially decomposed, granular and flocculent, and has an earthy odor when fresh.

activation

Plasma Physics and Fusion Energy Glossary Activation occurs when a particle interacts with an atomic nucleus, shifting the nucleus into an unstable state, and causing it to become radioactive. In fusion research, where deuterium-tritium is a common fuel mixture, the neutron released when (D + T) combine to form (4He + n) can activate the reactor structure. In this case the 4He is inert, the neutron sticks to another nucleus, and the neutron + nucleus reaction creates an actvation product. Sometimes called "radioactivation."

activation analysis

NASA Thesaurus A method of chemical analysis, especially for small traces of materials, based on the detection of characteristic radiations following a nuclear bombardment.

activation analysis

Plasma Physics and Fusion Energy Glossary Method for identifying and measuring chemical elements in a sample of material. Sample is first made radioactive by bombardment with neutrons, charged particles, or gamma rays. Newly formed radioactive atoms in the sample then give off characteristic radiations (such as gamma rays) that tell what kinds of atoms are present, and how many.

activation product

Plasma Physics and Fusion Energy Glossary The unstable nucleus formed when activation occurs

active

NASA SP-7, 1965 1. Transmitting a signal, as active satellite . Antonym of passive.
2. = radioactive, as active sample .
3. = fissionable, as active material .
4. Receiving energy from some source other than a signal, as active element .

active control

NASA Thesaurus The automatic activation of various control surface functions in aircraft.

active element

NASA SP-7, 1965 In a computer, a circuit or device which receives energy from some source other than the signal input.

active galactic nuclei

High Energy Astrophysics Dictionary- GSFC Normal galaxies with a massive black hole accreting gas at its center, thus producing enormous amounts of energy at all wavelengths of the electromagnetic spectrum.

active homing

NASA SP-7, 1965 The homing of an aerodynamic or space vehicle in which energy waves (as radar) are transmitted from the vehicle to the target and reflected back to the vehicle to direct the vehicle toward the target. Compare passive homing.

active homing guidance

NASA SP-7, 1965 See homing guidance.

active leg

NASA SP-7, 1965 An electrical element within a transducer which changes its electrical characteristics as a function of the application of a stimulus.

active region

SOHO Glossary - GSFC An area of the Sun where the magnetic fields are very strong. At ultraviolet and X-ray wavelengths they appear bright. In visible light they exhibit sunspots.

active satellite

NASA Thesaurus / NASA SP-7, 1965 A satellite which transmits a signal, in contrast to passive satellite .

active tracking system

NASA SP-7, 1965 A system which requires addition of a transponder, or transmitter on board the vehicle to repeat, transmit, or retransmit information to the tracking equipment, e.g. Dovap, Secor, Azusa, Miran, Minitrack.

active transducer

NASA SP-7, 1965 A transducer whose output is dependent upon sources of power, apart from that supplied by any of the actuating signals, which power is controlled by one or more of these signals.

actuating system

NASA SP-7, 1965 A mechanical system that supplies and transmits energy for the operation of other mechanisms or systems.

actuators

NASA Thesaurus Mechanisms to activate process control equipment, e.g., valves. Used for cartridge actuated devices, hydraulic actuators, and triggers.

acuity

NASA Thesaurus The keeness of ability to detect and discriminate.

Ada (programming language)

NASA Thesaurus A programming language based on PASCAL, originally developed on behalf of the US Department of Defense for use in embedded computer systems. It is named Ada in honor of Augusta Ada Byron, countess of Lovelace, primarily due to the fact that she was the assistant and patron of Charles Babbage and is considered the world's first programmer.

adaptation

NASA Thesaurus / NASA SP-7, 1965 The adjustment, alteration, or modification of an organism to fit it more perfectly for existence in its environment. Compare acclimatization, accustomization.
Adaptation is applied particularly to evolutionary change.

adaptation brightness

NASA SP-7, 1965 = adaptation luminance.

adaptation illuminance

NASA SP-7, 1965 = adaptation luminance.

adaptation level

NASA SP-7, 1965 = adaptation luminance.

adaptation luminance

NASA SP-7, 1965 The average luminance (or brightness) of those objects and surfaces in the immediate vicinity of an observer. Also called adaptation brightness, adaptation level, adaptation illuminance.
The adaptation luminance has a marked influence on an observer's estimate of the visual range because, along with the visual angle of the object under observation, it determines the observer's threshold contrast. High adaptation luminance tends to produce a high threshold contrast, thus reducing the estimated visual range. This effect of the adaptation luminance is to be distinguished from the influence of background luminance.

adapter

NASA Thesaurus / NASA SP-7, 1965 1. Any device or contrivance used or designed primarily to fit or adjust one thing to another, as: (a) a buckle or clip on a parachute harness, used in adjusting the harness to the wearer; (b) a joint attaching an afterburner to a turbine casing on a jet engine; (c) a fitting for connecting pipes, valves, etc., that have different types of threads.
2. Any device, appliance or the like used to alter something so as to make it suitable for a use for which it was not originally designed.

adapter skirt

NASA SP-7, 1965 A flange or extension of a space vehicle stage or section that provides a ready means for fitting some object to the stage or section.

adaptive control system

NASA SP-7, 1965 A control system which continuously monitors the dynamic response of the controlled system and automatically adjusts critical system parameters to satisfy preassigned response criteria, thus producing the same response over a wide range of environmental conditions.

adaptive optics

NASA Thesaurus Real-time optical correction for atmospheric perturbations and other system error sources.

ADC (abbr)

NASA SP-7, 1965 = analog to digital converter.

Adcock antenna

NASA SP-7, 1965 A pair of vertical antennas separated by a distance of one-half wavelength or less, and connected in phase opposition to produce a radiation pattern having the shape of a figure eight.

adder

NASA SP-7, 1965 In a computer, a device which can form the sum of two or more numbers or quantities.

additional apparent mass

NASA SP-7, 1965 = apparent additional mass.

additive

NASA Thesaurus / NASA SP-7, 1965 Any material or substance added to something else. Specifically, a substance added to a propellant to achieve some purpose, such as a more even rate of combustion, or a substance added to fuels or lubricants to improve them or give them some desired quality, such as tetraethyl lead added to a fuel as an antidetonation agent, or graphite, talc, or other substances added to certain oils and greases to improve lubrication qualities.

address

NASA SP-7, 1965 1. Of a computer, a location where information is stored.
2. An expression, usually numerical, identifying an address (sense 1).

adducts

NASA Thesaurus Chemical compounds with weak bonds, e.g., occlusive or Van der Waal bonds.

ADF

NASA SP-7, 1965 = automatic direction finder.

adiabat

NASA SP-7, 1965 A line on a thermodynamic diagram representing a constant potential temperature. See adiabatic process.

adiabatic

NASA SP-7, 1965 Without gain or loss of heat.

adiabatic

Plasma Physics and Fusion Energy Glossary Not involving an exchange of heat between the system said to be adiabatic and the rest of the universe.

adiabatic atmosphere

NASA SP-7, 1965 A model atmosphere in which the pressure decreases with height according to:

p = p

₀[1 - (-gz/c_p,dT₀)] C_p,dR_d where

p

₀ and

T

₀ are the pressure and temperature (° K) at sea level or other datum; z is the geometric height;

R

_d is the gas constant for dry gas;

c

_p,d is the specific heat for dry gas at constant pressure; and g is the acceleration of gravity. Also called dry-adiabatic atmosphere, convective atmosphere, homogeneous atmosphere . See homogeneous atmosphere, barotropy.

adiabatic compression

NASA SP-7, 1965 See adiabatic process.

adiabatic compression

Plasma Physics and Fusion Energy Glossary Compression (of a gas, plasma, etc.) not accompanied by gain or loss of heat from outside the system. For a plasma in a magnetic field, a compression slow enough that the magnetic moment (and other adiabatic invariants - see entry) of the plasma particles may be taken as constant.

adiabatic demagnetization cooling

NASA Thesaurus Use of paramagnetic salts cooled to the boiling point of helium in a strong magnetic field, then thermally isolated and removed from the field to demagnetize the salts and attain temperatures of 10(-3) K.

adiabatic efficiency

NASA SP-7, 1965 The efficiency with which work is done with respect to heat gains or losses. See adiabatic process.

adiabatic equivalent temperature

NASA SP-7, 1965 See equivalent temperature, sense 2.

adiabatic invariant

Plasma Physics and Fusion Energy Glossary Characteristic parameters which do not change as a physical system slowly evolves; the most commonly used one in plasma physics is the magnetic moment of a charged particle spiraling around a magnetic field line

adiabatic invariant

Earth's Magnetosphere Glossary - GSFC Adiabatic invariants are quantities associated with approximately periodic motions. They almost do not change, and thus also help in calculating the motion, to a very good degree of accuracy. They are often important in calculating the way ions and electrons move in a magnetic field. (Plasma Physics and Fusion Energy Glossary) Characteristic parameters which do not change as a physical system slowly evolves; the most commonly used one in plasma physics is the magnetic moment of a charged particle spiraling around a magnetic field line.

adiabatic process

NASA SP-7, 1965 A thermodynamic change of state of a system in which there is no transfer of heat or mass across the boundaries of the system. In an adiabatic process, compression always results in warming, expansion in cooling. See diabatic process.

adiabatic recovery temperature

NASA SP-7, 1965 1. The temperature reached by a moving fluid when brought to rest through an adiabatic process. Also called recovery temperature, stagnation temperature .
2. = adiabatic wall temperature.
3. The final and initial temperature in an adiabatic, Carnot cycle.

adiabatic wall temperature

NASA SP-7, 1965 The temperature assumed by a wall in a moving fluid stream when there is no heat transfer between the wall and the stream.

ADP (abbr)

NASA SP-7, 1965 = automatic data processing.

Adrastea

NASA Thesaurus A natural satellite of Jupiter orbiting at a mean distance of 129,980 kilometers.

adsorbate

NASA SP-7, 1965 In the process of adsorption, the adsorbed substance.

adsorbent

NASA Thesaurus / NASA SP-7, 1965 A material which takes up gas by adsorption.

adsorption

NASA Thesaurus / NASA SP-7, 1965 The adhesion of a thin film of liquid or gas to the surface of a solid substance. The solid does not combine chemically with the adsorbed substance. See sorption, absorption, chemisorption.

Advanced Composition Explorer

NASA Thesaurus Explorer spacecraft (launched August 25, 1997) carrying six high-resolution sensors and three monitoring instruments for sampling low-energy particles of solar origin and high-energy galactic particles. From a vantage point approximately 1/100 of the distance from the Earth to the Sun, the Advanced Composition Explorer (ACE) can perform measurements over a wide range of energy and nuclear mass, under all solar wind flow conditions and during both large and small particle events including solar flares. When reporting space weather ACE can provide an advance warning of geomagnetic storms.

Advanced Concepts Torus I

Plasma Physics and Fusion Energy Glossary (ACT-I) A steady-state toroidal device built primarily for studies of RF heating and RF current drive. Operated at PPPL but shut down several years ago.

Advanced Microwave Sounding Unit

NASA Thesaurus A line-scan instrument on the Advanced TIROS-N (ATN) NOAA K-N series of operational meteorological satellites. The AMSU consists of two functionally independent units, AMSU-A and AMSU-B. The AMSU-A is designed to measure scene radiance in 15 channels, ranging from 23.8 to 89 GHz, to derive atmospheric temperature profiles from the Earth surface to about 3 millibar pressure height. The AMSU-B is designed to measure scene radiance in five channels, ranging from 89 GHz to 183 GHz for the computation of atmospheric water vapor profiles.

Advanced Range Instrumentation Aircraft

NASA Thesaurus An EC-135 aircraft configured for reception recording and real-time relay of telemetry data.

Advanced Technology Laboratory

NASA Thesaurus An all-pallet payload utilizing the Space Shuttle and the European Spacelab and designed to accommodate 8 to 15 experiments per mission.

Advanced Toroidal Facility: (ATF)

Plasma Physics and Fusion Energy Glossary (ATF) A large stellarator device developed at Oak Ridge National Lab (ORNL),

Advanced Very High Resolution Radiometer

Global Land Information System Glossary - USGS The AVHRR is a broad-band, 4 or 5 channel scanner (depending on the model), sensing in the visible, near-infrared, and thermal infrared portions of the electromagnetic spectrum. This sensor is carried on NOAA's Polar Orbiting Environmental Satellites (POES), beginning with TIROS-N in 1978.

Advanced Very High Resolution Radiometer

NASA Thesaurus A five channel scanning instrument that quantitatively measures electromagnetic radiation.

advection

NASA Thesaurus / NASA SP-7, 1965 The process of transport of an atmospheric property solely by the mass motion of the atmosphere; also, the rate of change of the value of the advected property at a given point.
Regarding the general distinction (in meteorology) between advection and convection, the former describes the predominantly horizontal, large-scale motions of the atmosphere whereas convection describes the predominantly vertical, locally induced motions.

advective

NASA SP-7, 1965 Pertaining to advection .

aeon

NASA SP-7, 1965

10

⁹ years. This term was suggested by Harold Urey in 1957.

aeration zone

Glossary of Hydrologic Terms - NOAA A portion of the lithosphere in which the functional interstices of permeable rock or earth are not filled with water under hydrostatic pressure. The interstices either are not filled with water or are filled with water that is no held by capillarity.

aerial

NASA SP-7, 1965 1. = antenna.
2. Of or pertaining to the air, atmosphere, or aviation.

aerial archeology

AS&T Dictionary The location and study of archeological sites through observation or remote sensing from aircraft or airborne platforms.

aero-otitis media

NASA SP-7, 1965 An inflammatory reaction of the middle ear resulting from a difference in pressure between the gas in the middle ear and the surrounding atmosphere. Also called otitic barotrauma . c

aeroassist

NASA Thesaurus Changing orbit size by utilizing aerobraking, aerocapture, or aeromaneuvering.

aeroastromedicine

NASA SP-7, 1965 = aerospace medicine.

aeroballistics

NASA SP-7, 1965 The study of the interaction of projectiles or high speed vehicles with the atmosphere. See ballistics.
The problem of the effect of reentry on the trajectory of a vehicle is a problem in aeroballistics.

aerobiology

NASA Thesaurus / NASA SP-7, 1965 The study of the distribution of living organisms freely suspended in the atmosphere.

aerobraking

NASA Thesaurus Changing orbit size by using the upper atmosphere to create drag.

aerocapture

NASA Thesaurus Making use of the atmosphere of a planet or planetary satellite by capturing the object and reducing the orbit size so that it remains in orbit or lands on the body.

aerodontalgia

NASA SP-7, 1965 A toothache brought on by a change in ambient pressure.

aeroduct

NASA SP-7, 1965 A ramjet type of engine designed to scoop up ions and electrons freely available in the outer reaches of the atmosphere or in the atmospheres of other spatial bodies, and by a metachemical process within the duct of this engine, expel particles derived from the ions and electrons as a propulsive jetstream.

aerodynamic

NASA SP-7, 1965 Of or pertaining to aerodynamics.

aerodynamic coefficient

NASA Thesaurus / NASA SP-7, 1965 Any nondimensional coefficient relating to aerodynamic forces or moments, such as a coefficient of drag, a coefficient of lift, etc.

aerodynamic force

NASA Thesaurus / NASA SP-7, 1965 The force exerted by a moving gaseous fluid upon a body completely immersed in it.
The aerodynamic force is proportional to the expression
p u²L ² Rⁿ
where p is the fluid density; u is the velocity of the undisturbed stream relative to the body; L is a characteristic linear dimension of the body; and Rⁿ is the Reynolds number raised to the power of n, a constant usually determined experimentally. This form for the aerodynamic force is sometimes called Rayleigh formula. The component of the aerodynamic force parallel to the direction of flow is called the drag.

aerodynamic heating

NASA Thesaurus / NASA SP-7, 1965 The heating of a body produced by passage of air or other gases over the body; caused by friction and by compression processes and significant chiefly at high speeds. See radiative heating.

aerodynamic trail

NASA SP-7, 1965 A condensation trail formed by adiabatic cooling to saturation (or slightly supersaturation) of air passing over the surfaces of high-speed aircraft.
Aerodynamic trails form off the tips of wings and propellers and other points of maximum pressure decrease. They are relatively rare and of short duration compared to exhaust trails.

aerodynamic vehicle

NASA SP-7, 1965 A device, such as an airplane, glider, etc., capable of flight only within a sensible atmosphere and relying on aerodynamic forces to maintain flight.
The term is used when the context calls for discrimination from space vehicle.

aerodynamics

NASA Thesaurus / NASA SP-7, 1965 1. The science that deals with the motion of air and other gaseous fluids, and of the forces acting on bodies when the bodies move through such fluids, or when such fluids move against or around the bodies, as, his research in aerodynamics .
2. (a) The actions and forces resulting from the movement or flow of gaseous fluids against or around bodies, as, the aerodynamics of a wing in supersonic flight . (b) The properties of a body or bodies with respect to these actions or forces, as, the aerodynamics of a turret or of a configuration .
3. The application of the principles of gaseous fluid flows and of their actions against and around bodies to the design and construction of bodies intended to move through such fluids, as a design used in aerodynamics.

aeroelastic research wings

NASA Thesaurus Wings that are designed with less than normal stiffness to test devices that suppress flutter.

aeroelasticity

NASA Thesaurus / NASA SP-7, 1965 The study of the response of structurally elastic bodies to aerodynamic loads.

aeroembolism

NASA Thesaurus / NASA SP-7, 1965 1. The formation or liberation of gases in the blood vessels of the body, as brought on by a too-rapid change from a high, or relatively high, atmospheric pressure to a lower one.
2. The disease or condition caused by the formation of gas bubbles (mostly nitrogen) in the body fluids. The disease is characterized principally by neuralgic pains, cramps, and swelling, and sometimes results in death. Also call decompression sickness .

aeroemphysema

NASA SP-7, 1965 A swelling condition caused by the formation of gas in the tissues of the body.

aerolite

NASA SP-7, 1965 A meteorite composed principally of stony material.

aerology

NASA Thesaurus / NASA SP-7, 1965 1. As officially used in the U.S. Navy until early 1957, same as meteorology; this usage was more administrative than scientific.
2. As a subdivision of meteorology, the study of the free atmosphere through its vertical extend, as distinguished from studies confined to the layer of the atmosphere adjacent to the earth's surface.

aeromagnetic

Global Land Information System Glossary - USGS Aeromagnetic is descriptive of data pertaining to the Earth's magnetic field which has been collected from an airborne sensor.

aeromaneuvering

NASA Thesaurus Changing orbit size or plane or both by entering the upper atmosphere to create drag or lift or both.

Aeromaneuvering Orbit to Orbit Shuttle

NASA Thesaurus Proposed reusable upper stage for the Space Shuttle superseded by the orbit transfer vehicle. Used for AMOOS.

aeronomy

NASA Thesaurus / NASA SP-7, 1965 The study of the upper regions of the atmosphere where ionization, dissociation, and chemical reactions take place.

aeropause

NASA SP-7, 1965 A region of indeterminate limits in the upper atmosphere, considered as a boundary or transition region between the denser portion of the atmosphere and space.
From a functional point of view, it is considered to be that region in which the atmosphere is so tenuous as to have a negligible, or almost negligible, effect on men and aircraft, and in which the physiological requirements of man become increasingly important in the design of aircraft and auxiliary equipment.

aerophare

NASA SP-7, 1965 =radio beacon .

aeropulse engine

NASA SP-7, 1965 = pulsejet engine.

Aerosat satellites

AS&T Dictionary Satellites developed for aeronautical applications as part of a joint U.S., European Space Agency and Canadian program during the late-1960s and early-1970s. The Aerosat system uses two geostationary satellites over the Atlantic to provide voice and data links to transatlantic aircraft and to determine and monitor aircraft positions.

aeroshells

NASA Thesaurus Aerodynamic structural shells that attach to, or comprise a portion of, the exterior of an aerospace vehicle or space probe; especially such structures that support atmospheric entry, aerobraking, aeroassist, or hypersonic flight.

aerosinusitis

NASA SP-7, 1965 An inflammatory reaction of one or more of the accessory nasal sinuses resulting from a difference in pressure between the gas in the sinus and the surrounding atmosphere. Also called sinus barotrauma .

aerosols

NASA Thesaurus Dispersions of solid or liquid particles in gaseous media.

aerosonator

NASA SP-7, 1965 = resojet engine.

aerospace

NASA SP-7, 1965 (From aeronautics and space).
1. Of or pertaining to both the earth's atmosphere and space, as in aerospace industries.
2. Earth's envelope of air and space above it; the two considered as a single realm for activity in the flight of air vehicles and in the launching, guidance, and control of ballistic missiles, earth satellites, dirigible space vehicles, and the like.
Aerospace in sense 2 is used primarily by the U.S. Air Force. The term aerospace first appeared in print in the Interim Glossary; Aero-Space Terms (edited by Woodford Agee Heflin) published in February 1958 at the Air University, Maxwell Air Force Base, Alabama.

aerospace medicine

NASA Thesaurus / NASA SP-7, 1965 That branch of medicine dealing with the effects of flight through the atmosphere or in space upon the human body and with the prevention or cure of physiological or psychological malfunctions arising from these effects.

aerospace safety

NASA Thesaurus The engineering assessment and analysis of systems, subsystems, and functions of spacecraft, missiles, advanced aircraft and ground support in order to identify hazards associated with such systems and to design procedures that eliminate those hazards or determine tolerable safety levels.

aerospace technology transfer

NASA Thesaurus Technology transfer germane to aircraft and space vehicles, their propulsion, guidance, etc.

aerospace vehicle

NASA Thesaurus / NASA SP-7, 1965 A vehicle capable of flight within and outside the sensible atmosphere.

aerospike engines

NASA Thesaurus Rocket engines incorporating a radial in-flow (aerospike) nozzle for altitude compensation. Since the nozzle is open to the ambient atmosphere, the plume compensates for decreasing atmospheric pressure as the vehicle ascends.

aerothermodynamic border

NASA SP-7, 1965 An altitude at about 100 miles, above which the atmosphere is so rarefied that the skin of an object moving through it at high speeds generates no significant heat.

aerothermodynamic duct

NASA SP-7, 1965 The full term for athodyd .

aerothermodynamics

NASA Thesaurus / NASA SP-7, 1965 The study of aerodynamic phenomena at sufficiently high gas velocities that thermodynamic properties of the gas are important.

aerothermoelasticity

NASA Thesaurus / NASA SP-7, 1965 The study of the response of elastic structures to the combined effect of aerodynamic heating and loading.

aerozine

NASA Thesaurus A rocket fuel consisting of a mixture of hydrazine and unsymmetrical dimethylhydrazine (UDMH).

AFC (abbr)

NASA SP-7, 1965 = automatic frequency control.

afterbody

NASA Thesaurus / NASA SP-7, 1965 1. A companion body that trails a satellite.
2. A section or piece of a rocket or spacecraft that enters the atmosphere unprotected behind the nose cone or other body that is protected for entry.
3. The afterpart of a vehicle.

afterburner

NASA SP-7, 1965 A device for augmenting the thrust of a jet engine by burning additional fuel in the uncombined oxygen in the gases from the turbine.

afterburning

NASA Thesaurus / NASA SP-7, 1965 1. Irregular burning of fuel left in the firing chamber or a rocket after fuel cutoff.
2. The function of an afterburner, a device for augmenting the thrust of a jet engine by burning additional fuel in the uncombined oxygen in the gases from the turbine.

aftercooling

NASA SP-7, 1965 1. The cooling of a gas after compression.
2. The necessary cooling of a reactor core after its shutdown by pumping a liquid or gas through it to carry off the excess heat generated by continuing radioactive decay of fission products within the core.

aftercooling:

Plasma Physics and Fusion Energy Glossary Cooling of a reactor after it has been shut down.

afterglow

NASA Thesaurus / NASA SP-7, 1965 1. A broad, high arch of radiance or glow seen occasionally in the western sky above the highest clouds in deepening twilight, caused by the scattering effect of very fine particles of dust suspended in the upper atmosphere.
2. The transient decay of a plasma after the power has been turned off.
The decay time involved is a direct consequence of the charged particle loss mechanisms, such as diffusion and recombination. The magnitude of these quantities is determined by measuring the decay time under controlled conditions.

afterglow

Plasma Physics and Fusion Energy Glossary Recombination radiation emitted from a cooling plasma when the source of ionization (heating, etc) is removed.

afterheat

NASA SP-7, 1965 The heat generated in a reactor core after shutdown by continuing radioactive decay of fission products.

AGE (abbr)

NASA SP-7, 1965 = aerospace ground equipment. See GSE.

age of the moon

NASA SP-7, 1965 The elapsed time, usually expressed in days, since the last new moon. See phases of the moon.

agents of change

Galileo Project Glossary - JPL The constructive and destructive processes that reshape a planetary surface.

agglomerate

Glossary of Hydrologic Terms - NOAA An ice cover of floe formed by the freezing together of various forms of ice.

aging

NASA SP-7, 1965 In a metal or alloy, a change in properties that generally occurs slowly at room temperature and more rapidly at higher temperatures.

Agiwarn

NASA SP-7, 1965 Code name for the Western Hemisphere Regional Center for the IGY World Warning Agency.

agonic line

NASA SP-7, 1965 A line joining points at which the magnetic variation is zero. The agonic line is a particular case of an isogonic line.

agravic

NASA SP-7, 1965 Or pertaining to a condition of no gravitation. See weightlessness.

agravic illusion

NASA SP-7, 1965 An apparent movement of a target in the visual field due to otolith response in zerogravity. Also called oculoagravic illusion .

agricultural aircraft

NASA Thesaurus Light aircraft specially equipped for agricultural applications such as crop dusting.

AgRISTARS project

NASA Thesaurus A multiagency program utilizing Landsat remote sensing data to predict crop yields, land use, and detect pollution. Used for Crop Inventories by Remote Sensing.

agrophysical units

NASA Thesaurus Geographic areas defined for statistical purposes by AgRISTARS personnel whose boundaries are based on natural rather than political lines for the purpose of comparing similar agricultural regions.

AH-1G helicopter

NASA Thesaurus US Army designation for the Bell Model 209 Hueycobra attack helicopter powered by a single Avco Lycoming T53-L-13 turboshaft engine.

air

NASA Thesaurus / NASA SP-7, 1965 1. The mixture of gases comprising the earth's atmosphere.
The percent by volume of those gases found in relatively constant amount in dry air near sea level in very nearly as follows:

.

ELEMENT

%

nitrogen (N₂) 78.084

oxygen (O₂) 20.9476

argon (A) 0.934

carbon dioxide (CO₂) 0.0314 (variable)

neon (Ne) 0.001818

helium (He) 0.000524

methane (CH₄) 0.0002 (variable)

krypton (Kr) 0.000114

hydrogen (H₂) 0.00005

nitruous oxide (N₂O) 0.00005

xenon (Xe) 0.0000087

air breakup

NASA SP-7, 1965 The breakup of a test reentry body after reentry into the atmosphere.
Air breakup is sometimes provided for, as by the firing of a cartridge inside the reentry body, so as to retard the fall of certain pieces and increase the chances of their recovery. See blowoff.

air breathing boosters

NASA Thesaurus Boosters which are possible substitutes for rocket engines and which have inlets for oxygen sources for their engines rather than carrying their own oxygen as in a conventional rocket.

air breathing engines

AS&T Dictionary An aircraft or spacecraft propulsion system which sustains combustion of fuel with the intake of atmospheric oxygen and therefore cannot operate beyond the atmosphere.

air conditioning

NASA Thesaurus The simultaneous control of all, or at least three, of those factors affecting both the physical and chemical conditions of the atmosphere within any structure. These factors include temperature, humidity, motion, distribution, dust, bacteria, odor, and toxic gases.

air cushion landing systems

NASA Thesaurus Landing systems based on the ground effect principle whereby a stratum of air is utilized as the aircraft ground contacting medium (in place of landing gear).

air data systems

NASA Thesaurus Sets of aerodynamic and thermodynamic sensors, and a computer which provide flight characteristics such as airspeed, static pressure, air temperature and Mach number.

air launch

NASA SP-7, 1965 To launch from an aircraft in the air, as to air launch a guided missile .

air law

NASA Thesaurus The body of domestic and/or international laws dealing with regulations and liabilities in civil or military aviation.

air light

NASA SP-7, 1965 Light from sun and sky which is scattered into the eyes of an observer by atmospheric suspensoids (and, to slight extent, by air molecules) lying in the observer's cone of vision. That is, air light reaches the eye in the same manner that diffuse sky radiation reaches the earth's surface.
Air light is not be confused with airglow .

air lock

NASA SP-7, 1965 1. A stoppage or diminution of flow in a fuel system, hydraulic system, or the like, caused by a pocket of air or vapor. 2. A chamber capable of being hermetically sealed that provides for passage between two places of different pressure, as between an altitude chamber and the outside atmosphere.

air locks

NASA Thesaurus A stoppage or diminution of flow in a fuel system, hydraulic system, or the like, caused by pockets of air or vapor. Also chambers capable of being hermetically sealed that provide for passage between two places of different pressure as between an altitude chamber and the outside atmosphere.

air masses

NASA Thesaurus Large widespread volumes of air having particular characteristics of temperature and moisture content that were acquired at its source region and are modified as they move away from their source.

air navigation

NASA Thesaurus The art, science, or action of plotting and directing the course of an aircraft through the air from one place to another.

air pollution

NASA Thesaurus The presence of unwanted material in the air. The term "unwanted material" here refers to material in sufficient concentrations, present for a sufficient time, and under circumstances to interfere significantly with comfort, health, or welfare of persons, or with the full use and enjoyment of property. Used for atmospheric impurities.

air position indicator

NASA SP-7, 1965 (abbr API)
An airborne computing system which presents a continuous indication of the aircraft position on the basis of aircraft heading, airspeed, and elapsed time.

air shower

NASA SP-7, 1965 A grouping of cosmic-ray particles observed in the atmosphere; a cascade shower in the atmosphere. Also called shower .
Primary cosmic rays slowed down in the atmosphere emit bremsstrahlung photons of high energy. Each of these photons produces secondary electrons which generate more photons and the process continues until the available energy is absorbed.

air slew missiles

NASA Thesaurus Solid propellant rockets utilizing thrust vector control.

air sounding

NASA SP-7, 1965 The act of measuring atmospheric phenomena or determining atmospheric conditions at altitude, especially by means of apparatus carried by balloons or rockets. See sounding.

air start

NASA SP-7, 1965 An act or instance of starting an aircraft's engine while in flight, especially a jet engine after flameout. Compare in-flight start, ground start.

air traffic control

NASA Thesaurus A service operated by approriate authority to promote the safe, orderly and expedious flow of air traffic.

air transportation

NASA Thesaurus The conveyance of cargo and passengers by means of airplanes, helicopters, and other airborne vehicles.

air vane

NASA SP-7, 1965 A vane that acts in the air, as contrasted to a jet vane which acts within a jetstream. See control vane.

air vehicle

NASA SP-7, 1965 = aircraft

air-space

NASA SP-7, 1965 Of or pertaining to both the atmosphere and space.
Because this adjective is pronounced as the noun airspace is, it is subject to misunderstanding. Aerospace is commonly used instead.

Airborne Integrated Reconnaissance System

NASA Thesaurus Aerial reconnaissance system incorporating various modes of detection. Used for AIRS (reconnaissance sys).

airborne radar approach

NASA Thesaurus The use of airborne radar for helicopter approach control -- the radar cursor technique.

airbreather

NASA SP-7, 1965 An aerodynamic vehicle propelled by fuel oxidized by intake from the atmosphere; an air breathing vehicle.

airbreathing

NASA SP-7, 1965 Of an engine or aerodynamic vehicle, required to take in air for the purpose of combustion.

aircraft

NASA SP-7, 1965 Any structure, machine, or contrivance, especially a vehicle, designed to be supported by the air, being borne up either by the dynamic action of the air upon the surfaces of the structure or object, or by its own buoyancy; such structures, machines, or vehicles collectively, as, fifty aircraft.
Aircraft, in its broadest meaning, includes fixed-wing airplanes, helicopters, gliders, airships, free and captive balloons, ornithopters, flying model aircraft, kites, etc., but since the term carries a strong vehicular suggestion, it is more often applied, or recognized to apply, only to such of these craft as are designed to support or convey a burden in or through the air.

aircraft communication

NASA Thesaurus The conveyance of information to or from aircraft by radio or other signals.

aircraft construction materials

NASA Thesaurus A general term designating the materials used in manufacturing an aircraft.

aircraft control

NASA Thesaurus To direct the movements of an aircraft with particular reference to changes in attitude and speed.

aircraft design

NASA Thesaurus The act of conceiving and planning the structure, systems, and performance characteristics of an aircraft vehicle or any other apparatus, machine or contrivance intended to be borne up either by dynamic action of the air upon the object`s surfaces, or by the object`s own buoyancy.

aircraft icing

NASA Thesaurus Accumulation of ice on aircraft external surfaces, propellers and engine inlets from freezing rain or flight through inclement weather.

aircraft instruments

NASA Thesaurus Any electronic or mechanically-based instrument or instrument system designed for detecting, measuring, displaying, recording, telemetering, processing, or analyzing different values or quantities encountered in the flight of an aircraft; often supporting the general control of the aircraft.

aircraft performance

NASA Thesaurus The manner or effectiveness with which an aircraft vehicle or any airborne structure, machine, or contrivance functions while in operation.

aircraft power supplies

NASA Thesaurus Electric power sources for the normal operation of aircraft.

aircraft rocket

NASA SP-7, 1965 A rocket missile designed to be carried by, and launched from, an aircraft.

aircraft runup

NASA Thesaurus Final engine check prior to takeoff.

aircraft safety

NASA Thesaurus Techniques used to prevent aircraft failures or accidents; the degree to which an aircraft is free of the risk of malfunction or accidents.

aircraft spin

NASA Thesaurus A prolonged stall in fixed-wing aircraft characterized by a sustained spiral descent, usually with the nose down.

aircraft stability

NASA Thesaurus The property of an aircraft to maintain its attitude or to resist displacement, and if displaced, to develop forces and moments tending to restore the original condition.

airflow

NASA SP-7, 1965 A flow or stream of air. An airflow may take place in a wind tunnel, in the induction system of an engine, etc., or a relative airflow can occur, as past the wing or other parts of a moving craft; a rate of flow, measured by mass or volume per unit of time. See flow.

airfoil

NASA Thesaurus / NASA SP-7, 1965 A structure, piece, or body, originally likened to a foil or leaf in being wide and thin, designed to obtain a useful reaction on itself in its motion through the air.

airfoil oscillations

NASA Thesaurus Periodic motions experienced by airfoils in aerodynamic conditions.

airframe

NASA Thesaurus / NASA SP-7, 1965 The assembled structural and aerodynamic components of an aircraft or rocket vehicle that support the different systems and subsystems integral to the video.
The word airframe, a carryover from aviation usage, remains appropriate for rocket vehicles since a major function of the airframe is performed during flight within the atmosphere. There is disagreement as to whether the nose cone and combustion chambers are included in the term airframe while they are attached to the vehicle.

airglow

NASA Thesaurus / NASA SP-7, 1965 The quasi-steady radiant emission from the upper atmosphere as distinguished from the sporadic emission of the auroras.
Airglow is a chemiluminescence due primarily to the emission of the molecules O2 and N2, the radical OH, and the atoms O and Na. Emissions observed in airglow could arise from three-body atom collisions forming molecules, from two-body reactions between atoms and molecules, or from recombination of ions.
Historically, airglow has referred to visual radiation. Some recent studies use airglow to refer to radiation outside the visual range.

airport security

NASA Thesaurus Organization of trained security personnel, surveillance and screening devices, and procedures used for the protection of airport and airline property, aircraft, passengers, employees, and visitors from injury, air piracy, and other unauthorized acts.

airports

NASA Thesaurus An area of land or water that is used, or intended to be used, for the landing and takoff of aircraft, including buildings and facilities, if any.

airscoop

NASA SP-7, 1965 A hood or open end of an air duct or a similar structure, projecting into the airstream about a vehicle in such a way as to utilize the motion of the vehicle in capturing air to be conducted to an engine, a ventilator, etc.

airships

NASA Thesaurus Propelled and steerable dirigibles dependent on gases for flotation. Used for aerostats and dirigibles.

airsickness

NASA SP-7, 1965 Motion sickness occurring in flight.

airspace

NASA Thesaurus / NASA SP-7, 1965 Specifically, the atmosphere above a particular portion of the earth, usually defined by the boundaries of an area on the surface projected upward.
Airspace is sometimes particularized by altitude, as the airspace above 20,000 feet.

airstream

NASA SP-7, 1965 = airflow

Aitken dust counter

NASA SP-7, 1965 An instrument developed by John Aitken for determining the dust content of the atmosphere. In operation, a sample of air is mixed, in an expandable chamber, with a larger volume of dust-free air containing water vapor. Upon a sudden expansion, the chamber cools adiabatically below its dewpoint, and the droplets form with the dust particles as nuclei (Aitken nuclei). A portion of these droplets settle on a ruled plate in the instrument and are counted with the aid of a microscope. Also called Aitken nucleus counter .

Aitken nuclei

NASA Thesaurus / NASA SP-7, 1965 The microscopic particles in the atmosphere which serve as condensation nuclei for droplet growth during the rapid adiabatic expansion produced by an Aitken dust counter. These nuclei are both solid and liquid particles whose diameters are of the order of tenths of microns or even smaller.
The Aitken nuclei play an important role in atmospheric electrical processes, for they are the particles which capture (by adsorption or other surface electrical processes) small ions and thereby form large ions. In air containing large numbers of Aitken nuclei, the small ion population is small, the large ion population is large, and the air conductivity is low.

Aitken nucleus counter

NASA SP-7, 1965 = Aitken dust counter.

akermanite

NASA Thesaurus A mineral of the melilite group. It is isomorphous with gehlenite.

Alais meteorite

AS&T Dictionary A carbonaceous chondrite specimen which fell to earth in France in 1806. It weighed 0.3 grams.

albedo

Solar System Dynamics Glossary - JPL Geometric albedo is the ratio of a body's brightness at zero phase angle to the brightness of a perfectly diffusing disk with the same position and apparent size as the body.

albedo

NASA Thesaurus / NASA SP-7, 1965 The ratio of the amount of electromagnetic radiation reflected by a body to the amount incident upon it, often expressed as a percentage, as, the albedo of the earth is 34% . Compare Bond albedo.

The concept defined above is identical with reflectance. However, albedo is more commonly used in astronomy and meteorology and reflectance in physics.
Albedo is sometimes used to mean the flux of the reflected radiation as, the earth albedo is 0.64 calorie per square centimeter. This usage should be discouraged.
The albedo is to be distinguished from the spectral reflectance which refers to one specific wavelength (monochromatic radiation).
Usage varies somewhat with regard to the exact wavelength interval implied in albedo figures; sometimes just the visible portion of the spectrum is considered, sometimes the totality of wavelengths in the solar spectrum.

albedo neutrons

AS&T Dictionary Secondary neutrons ejected (along with other particles) in the collision of cosmic ray ions with particles of the upper atmosphere. See neutron albedo.

albedometer

NASA SP-7, 1965 An instrument used for the measurement of the reflecting power, the albedo, of a surface

ELEMENT	%
nitrogen (N₂)	78.084
oxygen (O₂)	20.9476
argon (A)	0.934
carbon dioxide (CO₂)	0.0314 (variable)
neon (Ne)	0.001818
helium (He)	0.000524
methane (CH₄)	0.0002 (variable)
krypton (Kr)	0.000114
hydrogen (H₂)	0.00005
nitruous oxide (N₂O)	0.00005
xenon (Xe)	0.0000087

Aerospace Science & Technology Dictionary

Aerospace Science
&
Technology Dictionary