The sabot separates from the projectile after launching.
See constellation.
See constellation.
Samples may be taken at random or systematically. The sample is taken in an attempt to estimate the population.
At the end of each saros the sun, moon, and line of nodes return to approximately the same relative positions and another series of eclipses begins, closely resembling the series just completed.
2. A manmade object that revolves about a spatial body, such as Explorer I orbiting about the earth. See spacecraft, table XIV [not reproduced].
3. Such a body intended and designed for orbiting, as distinguished from a companion body that may incidentally also orbit, as in the observer actually saw the orbiting rocket rather than the satellite.
4. An object not yet placed in orbit, but designed or expected to be launched into an orbit.
The saturation vapor pressure of any pure substance, with respect to a specified parent phase, is an intrinsic property of that substance and is a function of temperature alone (see Clapeyron-Clausius equation).
2. = equilibrium vapor pressure.
Owing to the release of latent heat, this lapse rate is less than the dry-adiabatic lapse rate, and the differential equation representing the process must be integrated numerically. Wet-bulb potential temperature is constant with height in an atmosphere with this lapse rate.
A scalar quantity is distinguished from a vector quantity by the fact that a scalar quantity possesses only magnitude, whereas a vector quantity possesses both magnitude and direction.
between their positive directions. Also called dot product, direct product, inner product. See vector product. For two vectors A and B, the scalar product is most commonly written A
B,
read A dot B, and occasionally as (AB). If the vectors A and B have the components
Ax, Bx, and Ay, By, and Az,
Bz along rectangular Cartesian, x, y, and z axes, respectively,
then
If a scalar product is zero, one of the vectors is zero or else the two are perpendicular.
A measure of the relationship between density and temperature of any point in an atmosphere; the thickness of a homogeneous atmosphere which would give the observed temperature:
where k is the Boltzmann constant; T is the absolute temperature; m and M are the mean molecular mass and weight, respectively, of the layer; g is the acceleration of gravity; and R* is the universal gas constant. Compare virtual height.
The number of input pulses per output pulse of a scaler is termed the scaling factor. A binary scaler is a scaler whose scaling factor is 2. A decade scaler is a scaler whose scaling factor is 10.
Scanning usually follows a systematic pattern involving one or more of the following: (1) In horizontal scanning (or searchlighting), the antenna is continuously rotated in azimuth around the horizon or in a sector (sector scanning); used to generate plan-position-indicator-scope displays. (b) Vertical scanning is accomplished by holding the azimuth constant but varying the elevation angle of the antenna; used in height-finding radars to generate the relative-height-indicator-scope display. (c) For conical scanning, a somewhat offcenter radiating element is rotated while its parabolic reflectors fixed in position so that the radiated beam generates a concially shaped volume with the antenna at the apex; used to determine accurate bearing and elevation angle of targets and employed in automatic tracking radars. (d) In helical scanning (or spiral scanning) the azimuth and elevation angle of the antenna are constantly varied so that at a given distance from the radar the radiated beam generates the surface of a hemisphere; used for radio direction finding, in certain types of search radars, and in tracking radars to search areas for targets.
2. The relative dispersion of points on a graph, especially with respect to a mean value, or any curve used to represent the points. See dispersion.
3. To accomplish scattering.
Convention varies as to whether this angle is measured with respect to the direction in which the incident radiation was advancing or with respect to the direction from scatterer to radiation source.
Recognition of this process and the development of specialized equipment (basically, more powerful transmitters and sensitive receivers) has greatly increased the range of VHF and UHF communication. The over-all technique is known as scatter communication.
Along with absorption, scattering is a major cause of the attenuation of radiation by the atmosphere. Scattering varies as a function of the ratio of the particle diameter to the wavelength of the radiation. When this ratio is less than about one-tenth, Rayleigh scattering occurs in which the scattering coefficient varies inversely as the fourth power of the wavelength. At larger values of the ratio of particle diameter to wavelength, the scattering varies in a complex fashion described by the Mie theory; at a ratio of the order of 10, the laws of geometric optics begin to apply.
1. Regions of different density in a fluid, especially as shown by special apparatus.
2. Pertaining to a method or apparatus for visualizing or photographing regions of varying density in a field of flow. See schlieren photography, scintillation.
Used in compounds, such as schlieren lens, schlieren method, schlieren photograph, etc.
A simulated Schuler pendulum carried in a vehicle moving in the earth's gravitational field would always indicate the true vertical.
If the object lies outside the earth's atmosphere, as in the case of stars and planets, the phenomenon is termed astronomical scintillation; if the luminous source lies within the atmosphere, the phenomenon is termed terrestrial scintillation. As one of the three principal factors governing astronomical seeing, scintillation is defined as variations in luminance only. It is clearly established that almost all scintillation effects are caused by anomalous refraction occurring in rather small parcels or strata of air, schlieren, whose temperatures and hence densities differ slightly from those of their surroundings. Normal wind motions transporting such schlieren across the observer's line of sight produce the irregular fluctuations characteristic of scintillation. Scintillation effects are always much more pronounced near the horizon than near the zenith. Parcels of the order of only centimeters to decimeters are believed to produce most of the scintillatory irregularities in the atmosphere.
2. A flash of light produced in a phosphor by an ionizing event. See scintillation counter. 3. On a radar display, a rapid apparent displacement of the target from its mean position. Also called target glint or wander.
This includes but is not limited to shift of effective reflection point on the target.
Because of possible ambiguity this term should be avoided in formal reports.
See constellation.
Scotopic vision is associated with rod function.
2. A surface on which images are displayed, as the face of a cathode-ray tube.
See constellation.
See constellation.
See
The unit of time, the second, was defined originally as the fraction 1/86 400 of the mean solar day. The exact definition of the "mean solar day" was left to astronomers, but their measurements have shown that on account of irregularities in the rotation of the Earth, the mean solar day does not guarantee the desired accuracy. In order to define the unit of time more precisely, the 11th CGPM (1960) adopted a definition given by the International Astronomical Union which was based on the tropical year [see ephemeris second]. Experimental work had, however, already shown that an atomic standard of time-interval, based on a transition between two energy levels of an atom or a molecule, could be realized and reproduced much more accurately. Considering that a very precise definition of the unit of time of the International System, the second, is indispensable for the needs of advanced metrology, the 13th CGPM (1967) decided to replaced the defintion of the second by the following:
The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom (13th CGPM (1967), Resolution 1).
The previous is an excerpt (with the exception of the reference to "ephemeris second") from WWW version of the National Institute of Standards and Technology: Physics Laboratory's International System of Units (SI)
It follows from this law that during an adiabatic process, entropy cannot decrease. For reversible adiabatic processes entropy remains constant, and for irreversible adiabatic processes it increases. Another equivalent formulation of the law is that it is impossible to convert the heat of a system into work without the occurrence of other simultaneous changes in the system or its environment. This version, which requires an engine to have a cold source as well as a heat source, is particularly useful in engineering applications. See first law of thermodynamics.
2. A celestial body revolving around another body, its primary.
3. A particle emitted in secondary emission.
The yield or ratio of secondary to primary electrons is a function of the primary electron energy.
2. = cloud seeding.
Recent studies show that seeing is a combination of three principal and distinct effects that the human eye is not capable of distinguishing: (a) scintillation, i.e., fluctuations in brightness; (b) transverse displacements of the image; and (c) variations of the radius of curvature of the wavefront rendering the image in an out of focus.
A substance which absorbs in such fashion is called a selective absorber and is to be contrasted with an ideal blackbody, white body, or gray body. In reality, all substances are selective absorbers when due regard is paid to their interaction with all wavelengths of the complete electromagnetic spectrum.
In general, the largest and most complex degree of selectivity is found for wavelengths nearly equal to the diameter of the scattering particles.
2. Specifically, referring to positions on the moon measured in latitude from the moon's equator and in longitude from a reference meridian.
In active homing guidance the information received is in response to transmissions from the craft. In passive homing guidance natural radiations from the destination are utilized.
2. Half the angle at the observer subtended by the visible disk of a celestial body.
One-half the longest diameter of an ellipse.
One-half the shortest diameter of an ellipse.
For example, a perfect corner reflector is invisible to a circularly polarized radar because it reverses the sense.
Sensible temperature depends on the air temperature; radiation from the sun, sky, and surrounding objects; relative humidity; and air motion. The wet-bulb temperature is often taken as an approximate measure.
2. In measurements, the derivative representing the change in instrument indication produced by a change in the variable being measured.
2. The nerve endings or sense organs which receive information from the environment, from the organism, or from both.
2. The moment of this action.
See constellation.
2 Pertaining to or incorporating a servomechanism.
It should be noted that servomechanism and regulator are not mutually exclusive terms; their application to a particular system will depend on the method of operation of that system.
2. To place a binary cell in the one state.
See constellation.
As originally used, the term applied only to instruments having an arc of 60 degrees, a sixth of a circle, from which the instrument derived its name. Such an instrument had a range of 120 degrees. In modern practice the term applies to a similar instrument, regardless of its range, very few modern instruments being sextants in the original sense.
2. = atmospherics.
Such observations are more commonly obtained from networks of two or three widely spaced stations. Simultaneous observations of the azimuth of the discharge are made at all stations and the location of the storm is determined by triangulation.
By extension, the term is applied to a similar condition when any form of radiant energy is cut off by an obstruction, as a radar shadow. The darkest part of a shadow in which light is completely cut off is called the umbra; a lighter part surrounding the umbra, in which the light is only partly cut off, is called the penumbra.
Useful in space, a shadow shield is less effective in the earth's atmosphere because air scattering deflects radiation around it.
2. The optical method or technique by which this is done. A shadowgraph differs from a schlieren photograph in that the schlieren method depends on the first derivative of the refractive index while the shadow method depends on the second derivative. Interference measurements give the refractive index directly.
A shear plane wave in an isotropic medium is called a transverse wave.
A shield may be designated according to what it is intended to absorb, as a gamma-ray shield or neutron shield, or according to the kind of protection it is intended to give, as a background, biological, or thermal shield. The shield of a nuclear reactor is a body of material designed to prevent the escape of neutrons and radiation into a protected area, which frequently is the entire space external to the reactor. It may be required for the safety of personnel or to reduce radiation sufficiently to allow use of counting instruments.
2. A blow, impact, collision, or violent jar.
3. A sudden agitation of the mental or emotional state or an event causing it.
4. The sudden stimulation caused by an electrical discharge on the animal or human organism (e.g., electric shock).
2. The front side of a shock wave.
A short range trajectory measuring system using the intersections of the ellipsoids of Dovap and the hyperboloids of Dovap elsse or telemetry elsse during a rocket launch.
2. The flight of a rocket, as, the rocket made a 200-mile shot.
2. The wave components lying within such a band.
Although sidereal generally refers to the stars and tropical to the vernal equinox, sidereal time and the sidereal day are based upon the position of the vernal equinox relative to the meridian. The sidereal year is based upon the stars.
Because of the precession of the equinoxes, the sidereal day thus defined is slightly less than the period of rotation with respect to the stars, but the difference is less than 0.01 second. The length of the mean sidereal day is 24 hours of sidereal time or 23 hours 56 minutes 4.09054 seconds of mean solar time.
2. Specifically, the interval between two successive returns of an earth satellite in orbit to the same geocentric right ascension.
Sidereal time may be designated as local or Greenwich as the local or Greenwich meridian is used as the reference. When adjusted for nutation, to eliminate slight irregularities in the rate, it is called mean sidereal time.
Because of the precession of the equinoxes this is about 20 minutes longer than a tropical year.
2. The information to be conveyed over a communication system.
3. Any carrier of information; opposed to noise.
The signal level at some specified position near the source may be taken as the zero reference level. In an acoustic system the signal level is often in the form of a sound pressure level; either the reference sound pressure or the reference sound pressure level must be specified.
The higher the S/N ratio, the less the interference with reception.
It is constructed in the following manner. A silver disk located at the lower end of a diaphragmed tube serves as the radiation receiver for a calorimeter. Radiation falling on the silver disk is periodically intercepted by means of a shutter located in the tube, causing temperature fluctuations of the calorimeter which are proportional to the intensity of the radiation. The instrument is normally used as a secondary instrument and is calibrated against the water-flow pyrheliometer. It is used by the U.S. Weather Bureau as a standard instrument.
x + 
)
where y is the simple harmonic quantity; A is the amplitude;
is the angular frequency; x is the
independent variable; and
is the phase of the oscillation. The maximum value of the simple harmonic quantity is the amplitude A; it is sometimes called, for emphasis, the single amplitude to distinguish it from double amplitude which for a simple harmonic quantity is the same as the total excursion or peak-to-peak value. When a simple harmonic quantity is expressed as a complex quantity, the term amplitude must be used with caution in view of possible confusion with the alternate meaning of amplitude as the angle or argument of a complex quantity.
2. A heat sink. See source.
Sinking occurs whenever the rate of density decreases with height through the atmosphere is of smaller magnitude than normal or, in extreme cases, where the density actually increases with height.
2. A display employing an optical system with a dark trace tube.
For long radio waves, the ionosphere acts as the reflecting layer. For shorter wavelengths, the effect may be produced by strong superstandard propagation in elevated layers of the troposphere. Skip effects make it possible on occasion to detect targets at distances far greater than the normal radio horizon, while closer targets remain undetected.
2. Device that follows an order given by a master station through remote control.
2. In radar, changing the scale on the display.
See calorie.
Small ions may disappear either by direct recombination with oppositely charged small ions or by combination with neutral Aitken nuclei to form new large ions, or by combination with large ions of opposite sign. The small ion, collectively, is the principal agent of atmospheric conduction.
This system is used in Project Mercury for locating spacecraft down at sea.
Radiation which can penetrate more than 10 centimeters of lead is termed hard radiation.
2. Relative to the sun as a datum or reference , as solar time.
The solar apex is at approximately right ascension 270 degrees declination 34 degrees N. The point diametrically opposite the solar apex on the celestial sphere is the solar antapex, right ascension 90 degrees declination 34 degrees S.
Six and eight hour components of small amplitude have been observed. They are primarily thermal in origin. The 12-hour component has by many times the greatest amplitude of any atmospheric tidal component, about 1.5 millibars at the equator and 0.5 millibar in middle latitudes. This relatively large amplitude is often explained as a resonance effect. The 24-component is a thermal tide with great local variability.
Measurements of solar radiation at the earth's surface by the Smithsonian Institution for several decades give a best value for the solar constant of 1.934 calories per square centimeter per minute. Measurements from rockets of the intensity of the ultraviolet end of the spectrum have corrected this value to 2.00 calories per square centimeter per minute with a probable error of +/- 2 percent.
This may be either a mean solar day, or an apparent solar day, as the reference is the mean or apparent sun, respectively.
2. The duration of one rotation of the sun on its axis.
A solar eclipse is partial if the sun is partly obscured, total if the entire surface is obscured, or annular if a thin ring of the sun's surface appears around the obscuring body.
The adopted value of the solar parallax in the system of astronomical constants is 8.80 seconds of arc.
To a first approximation, the sun radiates as a blackbody at a temperature of about 5700 degrees K; hence about 99.9 percent of its energy output falls within the wavelength interval from 0.15 micron to 4.0 microns, with peak intensity near 0.47 micron. About one-half of the total energy in the solar beam is contained within the visible spectrum from 0.4 to 0.7 micron, and most of the other half lies in the near infrared, a small additional portion lying in the ultraviolet.
Solar time may be designated as mean or astronomical if the mean sun is the reference, or apparent if the apparent sun is the reference. The difference between mean and apparent time is called equation of time. Solar time may be further designated according to the reference meridian, either the local or Greenwich meridian or additionally in the case of mean time, a designated zone meridian. Standard or daylight-saving are variations of zone time. Time may also be designated according to the timepiece, as chronometer time or watch time, the time indicated by these instruments.
Two types of such observation are taken. The more common consists of measurements of the radiation reaching a horizontal surface, consisting of both radiation from the sun (direct solar radiation) and that reaching the instrument indirectly by scattering in the atmosphere (diffuse sky radiation). The other type of observation involves the use of an equatorial mount that keeps the instrument pointed directly at the sun at all times. The sensitive surface of the instrument is normal to the path of the radiation and is shielded from indirect radiation from the sky.
2. Specifically, a pyranometer consisting of a Moll thermopile covered by a bell glass.
Solenoids formed by the intersection of surfaces of equal pressure and density are frequently referred to in meteorology. A barotropic atmosphere implies the absence of solenoids of this type, since surfaces of equal pressure and density coincide.
)A portion of the whole of space about a given point, bounded by a conical surface with its vertex at that point and measured by the area cut by the bounding surface from the surface of a sphere of unit radius centered at that point. See steradian.
That in the northern hemisphere is called the summer solstice and that in the southern hemisphere the winter solstice. Also called solstitial point.
2. That instant at which the sun reaches one of the solstices, about June 21 (summer solstice) or December 22 (winter solstice).
The sonar capsule, if attached to a reentry body, may be used to locate the reentry body in case of a water landing.
The loudness of any sound that is judged by the listener to be n times that of the 1-sone tone is n sones. A millisone is equal to 0.001 sone. The loudness scale is a relation between loudness and level above threshold for a particular listener. In presenting data relating loudness in sones to sound pressure level, or in averaging the loudness scales of several listeners, the thresholds (measured or assumed) should be specified.
2. Of or pertaining to sound, as in sonic amplifier.
In sense 2, acoustic is preferred to sonic.
A shock wave is a pressure disturbance and is received by the ear as a noise or clap.
2. A sensation evoked by the oscillation described above in the human ear.
In case of possible confusion, the term sound wave or elastic wave may be used for concept 1 and the term sound sensation for concept 2. Not all sound wave can evoke an auditory sensation, e.g., ultrasound. The medium in which the sound exists is often indicated by an appropriate adjective, e.g., airborne, water borne, structure borne.
The terms instantaneous energy density, maximum energy density, and peak energy density have meanings analogous to the related terms used for sound pressure. In speaking of average energy density in general, it is necessary to distinguish between the space average (at a given instant) and the time average (at a given point).
In a medium of density
for a plane or spherical free wave having a velocity of propagation c, the sound energy flux through the area S corresponding to an effective sound pressure p is 
where
= the angle between the direction of propagation of the sound and the normal to the area S.
A suitable method of stating the weighting is, for example, The A-sound level was 43 decibels.
The following reference pressures are in common use: (a) 2 X 10E-4 microbar, (b) 1 microbar. Reference pressure (a) is in general use for measurements concerned with hearing and with sound in air and liquids, whereas (b) has gained widespread acceptance for calibration of transducers and various kinds of sound measurements in liquids. Unless otherwise explicitly stated, it is to be understood that the sound pressure is the effective (root-mean-square) sound pressure. It is to be noted that in many sound fields the sound pressure ratios are not the square roots of the corresponding power ratios.
where
2 is the Laplace operator,
is the velocity potential, c is the speed of sound, and t
is the time; the density variations and velocities are small. As so defined,
this includes waves outside the frequency limits of human hearing, which limits
customarily define sound. Also called acoustic wave, sonic wave.
See ultrasonic, infrasonic,
pressure wave. Gases, liquids, and solids transmit sound waves, and the propagation velocity is characteristic of the nature and physical state of each of these media. In those cases where a steadily vibrating sound generator acts as a source of waves, one may speak of a uniform wave train; but in other cases (explosions, lightning discharges) a violent initial disturbance sends out a principal wave, followed by waves of more or less rapidly diminishing amplitude.
2. In meteorology, same as upper air observation. However, a common connotation is that of a single complete radiosonde observation.
3. = air sounding.
Usually a sounding rocket has a near vertical trajectory.
2. Specifically, in the mathematical representation of fluid flow, a hypothetical point or place from which fluid emanates.
The strength of a source; the rate of mass flow of unit density across a curve enclosing the source is given by
where r is the distance from the source and is the radial speed.
3. Specifically, the device which supplies signal power to a transducer.
2. More generally, the volume in which all celestial bodies, including the earth, move.
A capsule is usually assumed to carry an organism or equipment.
2. The net electric charge within a given volume.
For example, at 50,000 feet, the drop in air pressure and the scarcity of oxygen creates a condition, so far as respiration is concerned, that is equivalent to a condition in outer space where no appreciable oxygen is present; thus, a physiological space equivalent is present in the atmosphere.
That component perpendicular to the line of sight is termed proper motion and that component in the direction of the line of sight, radial motion.
2. Specifically, a closed chamber capable of approximately the vacuum and normal environments of space.
From 1957 through 1962 spacecraft were designated by the year and a Greek letter assigned in the order of launching, as 1958
for the first satellite of 1958. When more than one object was put in orbit by a single launch vehicle, each object was numbered, as 1961o2. (Space probes were not included in this system until 1960). Beginning January 1, 1963, arabic numerals supplanted Greek letters in the scientific designations of all spacecraft with a lifetime of more than 90 minutes. Thus, the first satellite launched in 1963 was 1963-1, the last was 1963-55. When more than one component is put in orbit, alphabetical suffixes are added to the designations, as 1963-4A. The letter A usually designates the component carrying the principle scientific payload; B, C, etc., are used as needed for any subsidiary payloads and then for inert components in order of maximum brightness. The designation system was promulgated formally in the COSPAR Guide to Rocket and Satellite Information and Data Exchange. The Guide has been published in full in COSPAR Information Bulletin No. 9, July 1962, and in IGY Bulletin No. 61, July 1962. Table XIV [not reproduced] is a listing of scientific satellites and space probes launched through 1964 and is reprinted from the IG Bulletin (International Geophysics Bulletin) published by the National Academy of Sciences.
2. Specifically, the dimension of an airfoil from tip to tip measured in a straight line.
Span is not usually applied to vertical airfoils.
The exact meaning to be attached to the term spark discharge varies somewhat in the literature. It is frequently applied to just the transient phase of the establishment of any arc discharge. A lightning discharge is a large-scale spark discharge, though its very length introduces certain details not found in laboratory short-spark processes.
For gases the thermodynamic process must be specified; two specific heats are defined, one being the specific heat in a constant-pressure process
and the other, the specific heat in a constant-volume process
In a perfect gas these are, by definition, constants with respect to temperature, and the difference of the specific heat at constant pressure and the specific heat at constant volume is equal to the gas constant:
R = cp - cv
A performance parameter of a rocket propellant, expressed in seconds, equal to the thrust F in pounds divided by the weight flow rate
in pounds per second:
Specific impulse is also equivalent to the effective exhaust velocity divided by the gravitational acceleration.
Volume per unit mass of a substance. The reciprocal of density.
2. Referring to thermal radiation properties, for ratios such as emittance, reflectance, and transmittance, at a specified wavelength; for powers, such as emissive power, within a narrow wavelength band centered on a specified wavelength.
Bright lines indicate emission, dark lines indicate absorption.
In one design, radiation enters the spectrophotometer through a slit and is dispersed by means of a prism. A bolometer having a fixed aperture scans the dispersed radiation so that the intensity over a narrow wave band is obtained as a function of frequency.
A spectroscope with a photographic recording device is called a spectrograph.
2. The series of images produced when a beam of radiant energy is subject to dispersion.
3. Short for electromagnetic spectrum or for any part of it used for a specific purpose as the radio spectrum (10 kilocycles to 300,000 megacycles).
4. In mathematics, = function.
5. In acoustics, the distribution of effective sound pressures or intensities measured as a function of frequency in specified frequency bands.
The angle between the normal to the surface and the incident beam is equal to the angle between the normal to the surface and the reflected beam. Any surface irregularities on a specular reflector must be small compared to the wavelength of the incident radiation.
Rate of motion in a straight line is called linear speed, whereas change of direction per unit time is called angular speed. Speed and velocity are often used interchangeably although some authorities maintain that velocity should be used only for the vector quantity.
The speed of propagation of electromagnetic radiation through a perfect vacuum; a universal dimensional constant equal to 299,792.5 +/- 0.4 kilometers per second. Also called velocity of light.
The speed of propagation of sound waves. In the atmosphere
where
is the ratio of
specific heat of air at constant pressure to that a constant volume, R
* is the universal gas constant, M0 is the
mean molecular weight of air at sea level, and TM
is the molecular scale temperature. At sea level in the standard atmosphere, the speed of sound is 340.294 meters per second (1116.45 feet per second). The concept of the speed of sound in the atmosphere loses its applicability at about 90 kilometers where the mean of free path of air molecules approaches the wavelengths of sound waves.
The volume inside this surface defines the region where the attracting body exerts the primary influence on a particle.
2. = space polar coordinates.
A unique point in space is determined by the intersection of three or more spheres. The term spherical system has been applied to systems using three or more slant ranges to determine space position.
They are several hundred miles in diameter and extend outward 5000 to 10,000 miles. Spicules have a lifetime of several minutes and may be related to granules.
Complex types of tumbling can be simulated by mounting the spin table on the arm of a centrifuge.
Spoilers are normally movable and consist of two basic types: the flap spoiler, which is hinged along one edge and lies flush with the airfoil or body when not in use, and the retractable spoiler, which retracts edgewise into the body.
where h is the Planck constant and v is the frequency.
2. Any electromagnetic radiation from a radio receiver. Also called spurious emission.
Spurious counts are caused by failure of the quenching process, electrical leakage, and the like. Spurious counts may seriously affect measurement of background counts.
2. Specifically, in radar a pulse initiated by a rapid rise to peak power, maintained at a constant peak power over the finite pulse length, and terminated by rapid decrease from peak power.
2. An explosive device used in the ignition of a rocket. Usually called an igniter. Used for XM-6 squib and XM-8 squib.
2. Of a fuel, the capability of a fuel to retain its characteristics in an adverse environment, e.g. extreme temperature.
2. A step or process through which a fluid passes, especially in compression or expansion.
3. A set of stator blades and a set of rotor blades in an axial-flow compressor or in a turbine; an impeller wheel in a radial-flow compressor. See multistage compressor, single-stage compressor, single-stage turbine.
2. In compressible flow, the pressure exhibited by a moving gas or liquid brought to zero velocity by an isentropic process.
3. = total pressure.
4. = impact pressure.
Because of the lack of a standard meaning, stagnation pressure should be defined when it is used.
2. A document that establishes engineering and technical limitations and applications for items, materials, processes, methods, design, or engineering practices.
Standard atmospheres, sense 1, which have been used are: (a) The NACA standard atmosphere, also called U.S. standard atmosphere, prepared in 1925, which was supplanted by (b) The ICAO standard atmosphere, adopted in 1952, which was extended to greater altitudes by (c) The ARDC model atmosphere, 1956, and (d) The U.S. extension to the ICAO standard atmosphere, adopted in 1956, which has been revised by (e) The ARDC model atmosphere, 1959, which incorporated some satellite data which has been supplanted by (f) The U.S. Standard Atmosphere-1962. (See Table XV [not reproduced]).
2. (abbr atm). A standard unit of atmospheric pressure. Defined as that pressure exerted by a 760-milimeter column of mercury at standard gravity (980.665 centimeters per second) at temperature 0o C.
)A measure of the dispersion of data points around their mean value. It is the positive square root of the arithmetic mean of the squares of the deviation from the arithmetic mean of the population:
where m is arithmetic mean; d is deviation from the arithmetic mean; and n is number of points.
where d is deviation from R ; R is curve of regression; and n is number of points.
S is a measure of the variation to be expected in making predictions from the regression equation.
2. In physics, a pressure of 1 standard atmosphere.
Standard propagation results in a ray curvature due to refection which has a value approximately one-fourth that of the earth's curvature, giving a radio horizon which is about 15 percent greater than the distance to the geometrical horizon. This is equivalent to straight-line propagation over a fictitious earth whose radius is four-thirds the radius of the actual earth.
Standard refraction may be included in ground-wave calculations by use of an effective earth radius of 8.5 X 10E6 meters, or four-thirds the geometrical radius of the earth.
2. In physics, usually the ice point (0 degrees C); less frequently, the temperature of maximum water density (4 degrees C).
3. In meteorology, this has no generally accepted meaning, except that it may refer to the temperature at zero altitude in the standard atmosphere (15 degrees C).
2. A measure of uniformity.
3. A special case of calibration whereby a known input is applied to a device or system for the purpose of verifying the output or adjusting the output to a desired level or scale factor.
Applied to transducers, standardization indicates adjustments of the output to a standard value within specified limits of error.
v where h is the heat transfer coefficient, cp is the specific heat, is the density, and v is the flow velocity.
2. Any luminous body seen in the heavens.
The star (sense 1) of our solar system is the sun. In sense 2, star sometimes excludes the sun, the moon, and manmade satellites from the category.
O - He II absorption;
B - He I absorption;
A - H absorption;
F - Ca II absorption;
G - strong metallic lines;
K -bands developing;
M - very red.
Also, the letters, P, W, Q, R, N, and S are used to designate comparatively rare types of stars which do not fall into the main series.
2. Involving no movement, as in static test.
3. Any radio interference detectable as noise in the audio stage of a receiver.
1. The pressure with respect to a stationary surface tangent to the mass-flow velocity vector.
2. The pressure with respect to a surface at rest in relation to the surrounding fluid.
This may or may not be the same as either the climatological station pressure or the actual pressure, the difference being attributable to the difference in reference elevations. Station pressure usually is the base value from which sea-level pressure and altimeter setting are determined.
A stationary orbit with respect to the earth is commonly called a 24-hour orbit.
Stationary waves can only be approximated in practice.
2. Specifically, the stable operating condition of a reactor in which the neutron inventory remains constant; that is, the effective multiplication factor ke is equal to 1.
). A universal constant of proportionality between the radiant emittance of a blackbody and the fourth power of the body's absolute temperature; 5.6697 X 10E-5 erg centimeter squared second degrees KE4.
T4 is the Stefan-Boltzmann constant; and T is the absolute temperature of the blackbody. Also called Stefan law. This law was established experimentally by Stefan and was given theoretical support by thermodynamic reasoning due to Boltzmann. This law may be deduced by integrating Planck law over the entire frequency spectrum.
steradians in a sphere.
2. = measurand.
If a regenerator is used so that heat rejected during the constant-volume process is recovered during heat addition at constant volume, the thermal efficiency of the Stirling cycle is the same as for the Carnot cycle, with less compressive work needed.
The opposite of stooping is towering.
2. Any device in which information can be stored. Also called a memory device.
3. In a computer, a section used primarily for storing information. Such a section is sometimes called a memory or a store.
The physical means of storing information may be electrostatic, ferroelectric, magnetic, acoustic, optical, chemical, electronic, electrical, mechanical, etc., in nature.
2. To introduce information into such a device.
3. A container, rocket, bomb, or vehicle carried externally in a craft.
In steady-state flow the streamlines coincide with the trajectories of the fluid particles; otherwise, the streamline pattern changes with time. See free streamline. Compare trajectory.
2. The effect of a physiological, psychological, or mental load on a biological organism which causes fatigue and tends to degrade proficiency.
ij. It has nine components, one for each of the coordinate faces of an imaginary element upon which the stress acts ( j = x, y, z ) and for each direction in which the stress is directed ( i = x, y, z ). By definition, an inviscid fluid is one in which the six tangential stresses (i +/- j) are zero, and the three normal stresses (i = j) are equal to the negative of the pressure.
where n is a frequency; l is a representative length, and u is a representative velocity of the stream.
Subatomic particles are classified by relative mass into four groups: leptons, mesons, nucleons, and hyperons, from lowest to highest masses, respectively.
Subcommutation is called synchronous if its rate is a submultiple of that of the primary commutator. Unique identification must be provided for the subcommutation frame pulse.
The expression subpermanent magnetism is sometimes used because of the slow dissipation of such magnetism, but the expression permanent magnetism is considered preferable.
Greater-than-normal refraction is called super refraction.
Aerodynamic problems of subsonic flow are treated with the assumption that air acts as an incompressible fluid.
Substandard propagation produces a less-than-normal downward bending or even an upward bending of radio waves as they travel through the atmosphere, giving closer radio horizons and decreased radar and radio coverage. It results primarily when propagation takes place through a layer in which moisture remains constant or increases with height.
2. That instant at which the sun reaches the point of maximum northerly declination, about June 21.
The sun visible in the sky is called apparent or true sun. A fictitious sun conceived to move eastward along the celestial equator at a rate that provides a uniform measure of time equal to the average apparent time is called mean sun; a fictitious sun conceived to move eastward along the ecliptic at the average rate of the apparent sun is called dynamical mean sun.
Sunspots usually occur in pairs with opposite magnetic polarities. They have a lifetime ranging from a few days to several months. Their occurrence exhibits approximately an 11-year period (the sunspot cycle).
An approximate 11-year cycle has been found or suggested in geomagnetism, frequency of aurora, and other ionospheric characteristics. The u-index of geomagnetic intensity variation shows one of the strongest known correlations to solar activity. Eleven-year cycles have been suggested for various tropospheric phenomena, but none of these has been substantiated.
See frequency band.
Corresponding crosspatching is required at the decommutator.
Superior mirages occur when the temperature lapse rate near the earth's surface is less than its normal value or, especially, when the temperature actually increases with height. Under these conditions the velocity of light increases upward in such a way that light rays are bent downward as they propagate through the layer in quasi-horizontal directions. The downward curvature gives the impression that the position of the object viewed is well above its true position in space. The object also appears inverted. Complex combination of superior and inferior mirages may occur with unusual density stratifications.
Superstandard propagation produces a greater-than-normal downward bending of radio waves as they travel through the atmosphere, giving extended radio horizons and increased radar coverage. It results primarily from propagation through layers near the earth's surface in which the moisture lapse rate is greater than normal, or the temperature lapse rate less than normal, or both. A condition in which warn dry air moves out over a cool water surface is an example of superrefraction. A layer in which the downward bending is greater than the curvature of the earth is called a radio duct. Frequently, the general term, anomalous propagation, is used for superstandard propagation.
2. A wing, rudder, propeller blade, vane, hydrofoil, or the like - applied in this sense to the entire structure or body.
Given sufficient time, a suspension will, be definition, separate itself by gravitational action into two visibly distinct portions, whereas a colloidal system, by definition, is stable. Dust in the atmosphere is an example of a suspension of a solid in a gas.
This term is applied, for example, to the remaining engine of the Atlas after the two booster engines have been jettisoned. The term is also applied to a rocket engine used on an orbital flider to provide the small amount of thrust now and then required to compensate for the drag imparted by air particles in the upper atmosphere.
A linear time-base sweep has a constant sweep speed before retrace. An expanded time-base sweep is produced if the sweep speeds is increased during a selected part of the cycle; a delayed time-base sweep if the start of the sweep is delayed, usually to provide an expanded scale for a particular part. A sweep intended primarily for measurement of range may be called a range sweep. See trace.
This curve, plotted to minimize air resistance, starts off vertically, but bends towards the horizontal between 20 and 60 miles altitude to minimize the thrust required for vertical ascent.
This is sometimes called the month of the phases, since it extends from new moon to the next new moon. Also called lunation.
In meteorology, this term refers to meteorological data obtained simultaneously over a wide area for the purpose of presenting a comprehensive and nearly instantaneous picture of the state of the atmosphere. Thus, to a meteorologist, synoptic takes on the additional connotation of simultaneity.
2. Specifically, a major component of a given vehicle such as a propulsion system or a guidance system. Usually called a major system to distinguish it from the systems subordinate or auxiliary to it.
The system of sense 1 may become organized by a process of evolution, as in the solar system, or by deliberate action imposed by the designer, as in a missile system or an electrical system. In sense 2, the system embraces all its own subsystems including checkout equipment, servicing equipment, and associated technicians and attendants. When the term is preceded by such designating nouns as propulsion or guidance, it clearly refers to a major component of the missile. Without the designating noun, the term may become ambiguous. When modified by the word major, however, it loses its ambiguity and refers to a major component of the missile.
When the error is constant it is called a bias error. Systematic errors are often caused by false elements in an instrument. An example is an eccentrically mounted azimuth circle or an azimuth circle with graduation errors.
The term is used chiefly in connection with the moon, when it refers to the points occupied by the moon at new and full phase.