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- Hagen-Poiseuille flow = Poiseuille flow.
- half life
- The average time required for one half the atoms in a sample of radioactive
element to decay.
- The half life t(1/2) is given by
t(1/2) = (ln 2) / λ where λ is the decay constant.
- half-period zone = Fresnel zone.
- half-power points
- The points on the radiation
pattern of an antenna where the transmitted power is one-half that of the
maximum of the same lobe. See half-power
- half-power width
- In a plane containing the direction of the maximum of a lobe of the radiation
pattern of an antenna, the full angle between the two directions in
that plane in which the radiation intensity is one-half the maximum value of
- See line
- Hall constant
- In an electrical conductor, the constant of proportionality R in the
Eh = RJ X H
where Eh is transverse electric field (Hall field); J is
current density; and H is magnetic field.
- The sign of the majority carrier can be inferred from the sign of the
- Hall effect
- The electrical polarization
of a horizontal conducting sheet of limited extent, when that sheet moves
laterally through a magnetic
field having a component vertical to the sheet.
- The Hall effect is important in determining the behavior of the
electrical currents generated by winds in the lower ionosphere.
- Hall mobility
- A measure of the flow of charged particles
perpendicular to both a magnetic
and an electric
- A faulty condition in the ignition system of a rocket
- hard landing
- An impact landing of a spacecraft on the surface of a planet or
destroying all equipment except possibly a very rugged package.
- Resistance of metal to plastic deformation usually by indentation.
However, the term may also refer to stiffness or temper, or to resistance to
scratching, abrasion, or cutting.
- Indentation hardness may be measured by various hardness tests, such as
Brinnell, Rockwell, and Vickers.
- hard radiation
- Radiation of high penetrating power; that is, radiation of
high frequency and
- A 10-centimeter thickness of lead is usually used as the criterion upon
which the relative penetrating power of various types of radiation is based.
Hard radiation will penetrate such a shield; soft radiation will not.
- hard vacuum
- A very high
vacuum, usually considered to be a pressure less than about 10E7 torr.
- Physical equipment as contrasted to ideas or design that may exist only on
- hard wire telemetry = wire link telemetry.
- 1. An integral multiple or submultiple of a given frequency; a
component of a periodic wave.
- 2. A signal having a
frequency which is a harmonic (sense 1) of the fundamental frequency.
- harmonic analysis
- A statistical method for determining the amplitude and
certain harmonic or
wave components in a set of data with the aid of Fourier
- harmonic analyzer
- A machine which resolves a periodic curve
into its harmonic
- A machine performing the opposite function is called a harmonic
- harmonic distortion
- Nonlinear distortion
characterized by the appearance in the output of multiples of the fundamental
when the input wave is sinusoidal.
- harmonic function
- Any solution of the Laplace
- harmonic motion
- The projection of circular motion on a diameter of the circle of such
- Simple harmonic motion is produced if the circular motion is of
constant speed. The combination of two or more simple harmonic motions results
in compound harmonic motion.
- harmonics of the earth's gravitational fields
- A series representing the gravitational
potentials of the earth in which the terms form a harmonic
- harmonic synthesizer
- A machine which combines elementary harmonic constituents into a single
- A machine performing the opposite function is called a harmonic
- A unit of information
content equal to one of ten possible and equally likely values or states
of anything used to store or convey information. One hartley equals log
(log 2 (10) = 3.323), or
- Hartley bands
- See absorption
- hazemeter = transmissometer.
- In radar, a B-display
modified to include indication of angle of
elevation. The target appears
as two closely spaced blips which
approximate a short bright line, the slope of which is in proportion to the
sine of the angle of elevation. Also called H-scan, H-scope, H-indicator.
- The horizontal direction in which a craft is pointed, expressed as angular
distance from a reference direction, usually from 0 degrees at the reference
direction clockwise through 360 degrees.
- Heading is often designated as true, magnetic, compass, or grid as the
reference direction is true, magnetic, compass, or grid north, respectively.
- heading-upward plan position indicator
- See plan
- head pressure = inlet pressure.
- head-to-foot acceleration
- See physiological
transferred by a thermal
- Heat can be measured in terms of the dynamical units of energy, as the
erg, joule, etc., or in terms of the amount of energy required to produce a
definite thermal change in some substance, as, for example, the energy
required per degree to raise the temperature of a unit mass of water at some
temperature ( calorie, Btu).
- heat balance
- 1. The equilibrium which exists on the average between the radiation
received by a planet and its
atmosphere from the sun and that emitted by the planet and atmosphere.
- That the equilibrium does exist in the mean is demonstrated by the
observed long-term constancy of the earth's surface temperature. On the
average, regions of the earth nearer the equator than about 35 degrees
latitude receive more energy from the sun than they are able to radiate,
whereas latitudes higher than 35 degrees received less. The excess of heat is
carried from low latitudes to higher latitudes by atmospheric and oceanic
circulations and is reradiated there.
- 2. The equilibrium which is known to exist when all sources of heat gain
and loss for a given region or body are accounted for. In general this balance
includes advective, evaporative (etc.) terms as well as a radiation term.
- heat barrier = thermal barrier.
- heat conductivity = thermal conductivity.
- heat dump = heat sink.
- heat engine
- A system which receives energy in the
form of heat and which, in the performance of an energy transformation, does
work. See thermodynamic
- The atmosphere itself is a heat engine.
- heat exchanger
- A device for transferring heat from one fluid to another without
intermixing the fluids, as (a) a regenerator
and (b) an apparatus for cooling or heating the air in a wind tunnel. See radiator,
- heat function = enthalpy.
- heat index
- The difference between the absolute visual magnitude of a star and the
absolute radiometric magnitude (Mv - Mr).
- heat of ablation
- A measure of the effective heat capacity of an ablating
material, numerically the heating rate input divided by the mass loss rate
which results from ablation.
- In the most general case, heat of ablation is given by
(qc + qr - σεTw4)/m where
qc is convective heat transfer in the absence of
ablation; qr is radiative heat transfer from hot gases to
ablation material; σεTw4 is rate of heat rejection by radiation from
external surface of ablation material; and m is rate at which gaseous ablation
products are injected into the boundary layer.
Heat of ablation is sometimes
evaluated neglecting the heat rejected by radiation and as a result
unrealistically high heats of ablation are obtained.
If qr &<; σεTw4,
for moderate values of stream enthalpy hs, heat of ablation is given by
Hv + μ (hs - hw) where Hs is heat required to cause a unit weight of mass
to be injected into boundary layer; μ is blocking factor with numerical value from
about 0.2 to 0.6 depending on material and type of flow; and hw is enthalpy at wall temperature.
- heat of fusion
- See latent
- heat of sublimation
- See latent
- heat of vaporization
- See latent
- heat pulse
- Specifically, the sudden rise and subsequent fall in the temperature of a
vehicle on reentry.
- heat shield
- 1. Any device that protects something from heat.
- 2. Specifically, the protective structure necessary to protect a reentry body
heating. See heat sink.
- heat sink
- 1. In thermodynamic theory, a means by which heat is stored, or
is dissipated or transferred from the system under
- 2. A place toward which the heat moves in a system.
- 3. A material capable of absorbing heat; a device utilizing such a
material and used as a thermal protection device on a spacecraft
- 4. In nuclear propulsion, any thermodynamic device, such as a radiator or condenser,
that is designed to absorb the excess heat energy of the working
fluid. Also called heat dump.
- heat transfer
- The transfer or exchange of heat by radiation,
conduction, or convection within a substance and between the substance and its
- Radiation represents the transfer of radiant energy from one region to
another by electromagnetic waves, with or without an intervening medium.
Conduction, or diffusion of heat, implies the elastic impact of fluid
molecules, without any net transfer of matter. Convection arises from the
mixing of relatively large volumes of fluid because of the fluid motion and
may be due either to local temperature inequalities (free convection) or to an
applied pressure gradient (forced convection).
- heat-transfer coefficient
- 1. The rate of heat
transfer per unit area per unit temperature difference, a quantity having
the dimensions of reciprocal length.
- 2. A misnomer for Nusselt
- heat treatment
- Heating and cooling a solid metal or alloy in such a way as to obtain
desired conditions or properties.
- Heating for the sole purpose of hot-working is excluded from the
meaning of this definition.
- heavenly body = celestial body.
- Heaviside layer = E-layer.
- heavy cosmic-ray primaries
- The positively charge nuclei of elements heavier than hydrogen and helium
up to atomic nuclei of iron. See cosmic
- These heavy atomic nuclei comprise about 1 percent of the total
cosmic-ray particles and less than 4 percent of the total positive charges.
- heavy hydrogen = deuterium.
- heavy ion = large ion.
- heavy water
- Water in
which the hydrogen of the water molecule consists entirely of the heavy
hydrogen isotope of mass 2 ( deuterium).
- Written D2O. Density, 1.1076 at 20 degrees C. It is used as
a moderator in certain types of nuclear reactors. The term is sometimes
applied to water whose deuterium content is greater than natural water.
- hecto (abbr h)
- A prefix meaning multiplied by 100.
- hectometric wave
- See frequency
- height (symbol h )
- 1. Vertical distance; the distance above some reference point or plane,
as, height above sea level. See altitude.
- 2. The vertical dimension of anything; the distance which something
extends above its foot or root, as blade height.
- height effect = antenna effect.
- height gain
- A radio-wave interference
phenomenon which results in a more or less periodic signal
strength variation with height. This specifically refers to interference
between direct and surface-reflected waves. See radiation
- helical antenna
- An antenna used
polarization is required. The driven element consists of a helix supported
above a ground plane.
- helical scanning
- In radar
scanning, varying the azimuth and
elevation of the antenna continuously to generate a spiral pattern of the
beam. Also called spiral
- Relative to the sun as a center, as a heliocentric orbit.
- heliocentric parallax
- The difference in the apparent
positions of a celestial
body outside the solar system, as observed from the earth and sun. Also
called stellar parallax. See parallax.
- Referring to positions on the sun measured in latitude from
the sun's equator and in longitude
from a reference meridian.
- Helmholtz free energy = Helmholtz function.
- Helmholtz function (symbol a )
- A mathematically defined thermodynamic
function of state, the decrease in which during a reversible isothermal
process is equal to the work done by the system. the Helmholtz function is
a = u - Ts
where u is specific internal energy; T is Kelvin temperature;
and s is specific entropy. By use of the first law of thermodynamics
for reversible processes,
da = -s dT - dw
where dw is the work done per unit mass by the system. Also called
Helmhotlz free energy, work function. Compare Gibbs
- Helmholtz theorem
- The statement that if F is a vector field satisfying certain quite general
mathematical conditions, then F is the sum of two vectors, one of which is
irrotational (has no vorticity),
the other solenoidal (has no divergence).
- Referring to thermal radiation properties, in all possible directions from
a flat surface.
- hemispherical emittance (symbol εh, Eh)
- The ratio of the emissive power of a specimen to that of a black body at
the same temperature, considering radiation emitted in all possible
- hemmungspunkt = stopping point.
- henry (abbr h)
- The unit of electrical inductance; the inductance of a closed circuit in
which an electromotive force of 1 volt is produced
when the electric current in the circuit varies uniformly at the rate of 1 ampere per
- Her, Herc
- International Astronomical Union abbreviations for Hercules. See constellation.
- Hercules (abbr Her, Herc)
- See constellation.
- hertz (abbr Hz)
- The unit of frequency,
cycles per second.
- Hertzian waves
waves of any frequency between 10 kilocycles per second and 300,000
megacycles per second. Now generally called radio waves. See frequency
- Herzberg bands
- See absorption
- To mix two radio signals of
to produce a third signal which is of lower frequency, i.e., to produce beating.
- Radar receivers are of the heterodyne type (as contrasted to the
superregenerative type) because the very high radio frequencies used in radar
are difficult to amplify. A target signal is heterodyned with a current of
lower frequency produced by a klystron oscillator and the resulting
intermediate-frequency signal can then be highly amplified for subsequent
presentation or analysis.
- The upper portion of a two-part division of the atmosphere
according to the general homogeneity of atmospheric composition; the layer
above the homosphere.
The heterosphere is characterized by variation in composition and mean
molecular weight of constituent gases. See atmospheric
- This region starts at 80 and 100 kilometers above the earth, and
therefore closely coincides with the ionosphere and the thermosphere.
- hexidecimal notation = sexidecimal notation.
- hibernating spacecraft
- A spacecraft
maintaining an orbit without
power and without maintaining orientation within the orbit, but with inherent
- A hibernating spacecraft could be in an orbit around the sun for months
or years before power is triggered from a station on earth at an opportune
- Variant of hydyne.
- high frequency (abbr HF)
- See frequency
- high-intensity gamma
- A level a gamma
radiation flux on the order of 10E4 roentgens or
- high-pass filter
- A wave
filter having a single transmission band extending
from some critical or cutoff frequency, not zero, up to infinite frequency.
- high-precision shoran (abbr hiran)
- See shoran.
- high-speed motion-picture photography
- The picture-taking frequency range from 32 to 500 pictures per second.
- high vacuum
- The condition in a gas-filled space at pressure less than 10-3 torr.
- The term high vacuum has frequently been defined as a pressure less
than some upper limit. High vacuum (and similar vacuum terms) should not be
defined as a pressure but rather as the condition or state in a gas-filled
space at pressures less than some upper limit or within specified limits. The
following classification of degrees of high vacuum has been proposed:
|high vacuum||10-3 to 10-6 torr|
|very high vacuum||10-6 to 10-9 torr|
|ultrahigh vacuum||10-9 torr and below|
- H-indicator = H-display.
- hiran (abbr) = high precision shoran
- See shoran.
- Random noise in the audio
frequency range, having subjective characteristics analogous to prolonged
- In radiation thermodynamics, a cavity whose walls are in radiative
equilibrium with the radiant
energy within the cavity.
- This idealized cavity can be approximated in practice by making a small
perforation in the walls of a hollow container of any opaque material. The
radiation escaping through such a perforation will be a good approximation to
radiation at the temperature of the interior of the container.
- Hohmann orbit
- A minimum energy transfer
- 1. During a countdown to
stop counting and to wait until an impediment has been removed so that the
countdown can be resumed, as in T minus 40 and holding. Compare count, recycle.
- 2. In computer terminology, to retain information in one storage device
after copying it into another storage device.
- holddown = holddown test.
- holddown test
- The testing of some system or subsystem in a rocket while the
rocket is firing but restrained in a test stand.
- holding beam
- An electron
beam which regenerates the electrostatic charges stored in an electrostatic-storage
- A mobile vacancy in the electronic valence structure of a semiconductor
which acts like an electron with
a positive charge.
- To follow a path of energy waves, especially
radio or radar waves, by
means of a directional
antenna, radar equipment, or other sensing devices, to or toward the point
of transmission or reflection of the waves.
- homer = homing beacon.
- The following of a path of energy waves to or
toward their source or point of reflection. See home, active
- homing beacon
- A beacon providing homing
guidance. Also called homer.
- homing guidance
- Guidance in
which a craft or missile is directed toward a destination by means of
information received from the destination.
- It is active homing guidance if the information received is in response
to transmissions from the craft, semiactive homing guidance if in response to
transmissions from a source other than the craft, and passive homing guidance
if natural radiations from the destination are utilized.
- homogeneous atmosphere
- 1. A hypothetical atmosphere
in which the density is constant with height.
- The lapse rate of temperature in such an atmosphere is known as the
autoconvective lapse rate and is equal to g/R (or approximately 3.4 degrees C
per 100 meters) where g is the acceleration of gravity and R is the gas
constant for air. A homogeneous atmosphere has a finite total thickness which
is given by RdTv/g, where Rd is the gas constant for dry air and Tv is the
virtual temperature (degrees K) at the surface. For a surface temperature of
273 degrees K, the vertical extent of the homogeneous atmosphere on the earth
is approximately 8000 meters. At the top of such an atmosphere both the
pressure and absolute temperature vanish.
- 2. With respect to radio propagation, an atmosphere which has a constant
of refraction, or one in which radio waves travel in straight lines at
constant speed. Free space is the ideal homogeneous atmosphere in this
- 3. Same as adiabatic atmosphere. See barotrophy.
- homologous turbulence
in which the mean value of the squares and products of the velocity components
and their derivatives differ only in scale from point to point. See isotropic
- The top of the homosphere,
or the level of transition between it and the heterosphere.
- The homopause probably lies between 80 and 90 kilometers, where
molecular oxygen begins to dissociate into atomic oxygen. The homopause is
somewhat lower in the daytime than at night.
- The lower portion of a two-part division of the atmosphere
according to the general homogeneity of atmospheric composition; opposed to
The region in which there is no gross change in atmospheric composition, that
is, all the atmosphere from the earth's surface to about 90 kilometers. See atmospheric
- The homosphere is about equivalent to the neutrosphere,
and includes the troposphere, stratosphere, and mesosphere; it also includes
the ozonosphere and at least part of the chemosphere.
- honeycomb core
- A lightweight strengthening material of a structure resembling a honeycomb
mesh. See sandwich
- Travel of a radio wave
to the ionosphere
and back to earth.
- The number of hops a radio signal has experienced is usually designated
by the expression one hop, two hop, multihop, etc. The number of hops is
called the order of reflection.
- Hopfield bands
- See absorption
- Hor, Horo
- International Astronomical Union abbreviations for Horologium. See
- That great
circle of the celestial
sphere midway the zenith and nadir, or a line
resembling or approximating such a circle.
- That line where earth and sky appear to meet, and the projection of
this line upon the celestial sphere, is called visible or apparent horizon. A
line resembling the visible horizon but above or below it is called a false
horizon. That circle of the celestial sphere formed by the intersection of the
celestial sphere and a plane perpendicular to the zenith-nadir line is called
sensible horizon if the plane is through any point, such as the eye of an
observer, geoidal horizon if through any sea-level point, and celestial or
rational horizon if through the center of the earth. The geometrical horizon
was originally considered identical with the celestial sphere and an infinite
number of straight lines tangent to the earth's surface, and radiating from
the eye of the observer. If there were no terrestrial refraction, geometrical
and visible horizons would coincide. An artificial horizon is a gyroscopic
instrument for indicating the attitude of an aircraft with respect to the
horizontal. A radio horizon is the line at which direct rays from a
transmitting antenna become tangent to the earth's surface. A radar horizon is
the radio horizon of a radar antenna.
- horizon system of coordinates
- A set of celestial
coordinates, usually altitude and
based on the celestial
horizon as the primary
great circle. See coordinate,
- horizontal parallax
- The geocentric
parallax of a body on the observer's horizon. This is equal to the angular
of the earth as seen from the body.
- horizontal scanning
- In radar
scanning, rotating the antenna in azimuth around
the horizon or in a sector. Also called searchlighting.
- horizontal stratification
- Uniform meteorological conditions at a given altitude, over the area under
- The term horizontally stratified atmosphere is generally assumed to
mean complete stratification at each altitude. It follows that the vertical
profile, which need not be a standard profile, is consistent over the area
under consideration. When the condition extends over a large area, the term
spherical stratification is used.
- An antenna shaped
like a horn. Also called horn radiator.
- A horn is usually designed as an extension of a waveguide
whose sides flare from the original waveguide size to a larger aperture size.
- horn antenna = horn.
- horn radiator = horn.
- International Astronomical Union abbreviation for Horologium. See
- Horologium (abbr Hor, Horo)
- See constellation.
- hot cathode
- A cathode that
functions primarily by the process of thermionic
emission. Also called thermionic cathode.
- hot-cathode ionization gage
- An ionization
gage in which the ions are produced by collisions with electrons emitted
from a hot filament (or cathode) and accelerated by an electric field. Also
called hot-filament ionization gage, ionization gage , or simply ion
- The Bayard-Alpert ionization gage employs a tube with an electrode
structure designed to minimize X-ray induced electron emission from the ion
- hot-filament ionization gage = hot-cathode ionization gage.
- hot test
- A propulsion system test conducted by actually firing the propellants.
- hot-wire transducer
- A unilateral
transducer that depends for its operation on the change in resistance of a
hot wire produced by the cooling or heating effects of a sound wave.
- hour angle
- Angular distance west of a celestial
meridian or hour
circle; the arc of the celestial equator, or the angle at the celestial
pole, between the upper branch of a celestial meridian or hour circle and the
hour circle of a celestial
body or the vernal
equinox, measured westward through 360 degrees.
- Hour angle is usually further designated as local, Greenwich, or
sidereal as the origin of measurement is the local or Greenwich celestial
meridian or the hour circle of the vernal equinox. See meridian
- hour circle
- On the celestial
sphere, a great
circle through the celestial poles. An hour circle through the zenith is called
a celestial meridian. Also called circle of declination, circle of
- H-scan = H-display.
- H-scope = H-display.
- Huggins bands
- See absorption
- Electrical disturbance at the power-supply frequency or
- human engineering
- The activity or science of designing, building, or equipping mechanical
devices or artificial environments to the anthropometric, physiological, or
psychological requirements of the men who will use them.
- human factors
- The study of psychophysical, psychological, and physiological variables
which affect man's performance in an operational system. See human
- 1. The amount of water vapor
in the air.
- 2. Specifically, relative
humidity. See absolute
humidity, dew point.
- 1. Of an aircraft, rocket, etc.: to weave about its flightpath, as if
seeking a new direction of another angle of attack, specifically, to yaw back
- 2. Of a control surface: to rotate up and down or back and forth without
being deflected by the pilot.
- 3. Of a control system: to oscillate about a selected value.
- 4. Of an indicator on a display: to swing back and forth or to oscillate,
especially rather slowly.
- Fluctuation about a midpoint due to instability,
of the needle of an instrument about the zero point, or alternate lead and lag
of a synchronous motor with respect to the alternating current.
- Huygens principle
- A very general principle applying to all forms of wave motion
which states that every point on the instantaneous position of an advancing phase front
(wave front) may be regarded as a source of secondary spherical wavelets. The
position of the phase front a moment later is then determined as the envelope
of all the secondary wavelets (ad infinitum).
- This principle, stated by Dutch physicist Christian Huygens (1629-95),
is extremely useful in understanding effects due to refraction, reflection,
diffraction, and scattering of all types of radiation, including sonic
radiation as well as electromagnetic radiation and applying even to ocean-wave
- Huygens wavelets
- The assemblage of secondary waves asserted by Huygens to be set up at each
instant at all points on the advancing surface of a wave, or phase
- Many phenomena of wave optics can be neatly explained on this
assumption ( Huygens
principle) of the continual creation of new wavelets and the subsequent
destructive or constructive interference between the wavelets to set up the
next-imagined state of the advancing wave front.
- Hya, Hyda
- International Astronomical Union abbreviations for Hydra. See constellation.
- International Astronomical Union abbreviations for Hydrus. See constellation
- Hydra (abbr Hya, Hyda)
- See constellation.
- The study of fluid motion. See aerodynamics.
- Fluid here refers ambiguously to liquids and gases.
- hydromagnetics = magnetohydrodynamics.
- Any product of condensation
of atmospheric water
vapor, such as rain, snow, fog, or frost. See meteor, sense 2.
- An instrument used for measuring the specific gravity of a liquid.
- A microphone
suitable for use in water or other liquid.
- That part of the earth that consists of the oceans, seas, lakes, and
rivers; a similar part of any other spatial body if such a body exists.
- hydrostatic equation
- In numerical equations, the form assumed by the vertical component of the
of motion when all coriolis, earth- curvature, frictional, and
vertical-acceleration terms are considered negligible compared with those
involving the vertical pressure force and the force of gravity. Thus,
dP = -pgdZ
where P is the atmospheric pressure; p is the density; g
is the acceleration of gravity; and Z is the geometric light.
- For cyclonic-scale motions the error committed in applying the
hydrostatic equation to the earth's atmosphere is less than 0.01 percent.
Strong vertical accelerations in thunderstorms and mountain waves may be 1
percent of gravity or more in extreme situations.
- hydrostatic equilibrium
- 1. The state of a fluid whose surfaces of constant pressure and constant
mass (or density) coincide and are horizontal throughout. Complete balance
exists between the force of gravity and the
pressure force. See hydrostatic
- 2. Of a rotating body, a state in which the body maintains, or returns to,
the figure generated by this rotation in spite of small disturbances.
- Hydrus (abbr Hyi, Hydi)
- See constellation.
- A hydrazine-base liquid
rocket fuel. Also called hidyne.
- Hyi, Hydi
- International Astronomical Union abbreviations for Hydrus. See constellation.
- Pertaining to breathing atmosphere pressure above sea level normal.
- Disturbances in the body resulting from an excess of the ambient
pressure over that within the body fluids, tissues, and cavities.
- An open curve with two branches, all points of which have a constant
difference in distance from two fixed points called focuses.
- Of or pertaining to a hyperbola.
- hyperbolic Dovap (abbr Hyperdop)
- A system utilizing four or more Dovap stations
with a common reference signal which is not coherent with the interrogation
- Hyperboloids of position are obtained by differencing phase of one
station against another. Space position is computed by intersection of three
or more hyperboloids of position.
- hyperbolic error
- The error in an interferometer
system arising from the assumption that the directions of the wave fronts
incident at two antennas of a baseline are
parallel, whereby the equiphase path is a cone.
- Mathematically, the equiphase path is a hyperbola.
- hyperbolic fix
- A fix established by means of hyperbolic
lines of position.
- hyperbolic guidance
- The guidance of a
rocket or the like in which radio signals, transmitted simultaneously from two
ground stations, arrive at the guided object with a constant time difference,
thereby establishing a hyperbolic
line of position which the object follows.
- hyperbolic line of position
- A line of position in the shape of a hyperbola,
determined by measuring the difference in distance to two fixed points. Loran lines of
position are an example.
- hyperbolic navigation
- Radio navigation in which a hyperbolic
line of position is established by signals received from two stations at a
constant time difference.
- hyperbolic system
- A system where lines of
position are determined from time or phase differences
relative to two or more fixed stations which are the focuses of hyperbolas.
- In a three-dimensional system, the lines of position become hyperbolic
surfaces of position.
- hyperbolic velocity
- A velocity sufficient to allow escape from the solar system. Comets unless
captured by the sun have hyperbolic velocities and their trajectories are
- Hyperdop (abbr) = hyperbolic Dovap.
- hypergolic propellants
- Rocket propellants
that ignite spontaneously when mixed with each other.
- A satellite of Saturn orbiting at a mean distance of 1,481,000 kilometers.
- In the classification of subatomic
particles according to mass, the heaviest of such particles. Compare lepton, meson, nucleon.
- Some large and highly unstable components of cosmic rays are hyperons.
- A condition in which the total oxygen content of the body is increased
above that normally existing at sea level.
- 1. Pertaining to hypersonic
- 2. Pertaining to speeds of Mach 5 or greater.
- hypersonic flow
- In aerodynamics, flow of a fluid
over a body at speeds much greater than the speed of sound and in which the
shock waves start at a finite distance from the surface of the body. Compare
- hypersonic glider
- An unpowered vehicle, specifically a reentry
vehicle, designed to fly at hypersonic
- That branch of aerodynamics
that deals with hypersonic
- Extremely high velocity.
- Applied by physicists to speeds approaching the speed of light, but
generally implies speeds of the order of satellite
speed and greater.
- Overbreathing. A respiratory-minute volume, or pulmonary ventilation, that
is greater than normal.
- Hyperventilation often results in an abnormal loss of carbon dioxide
from the lungs and blood, which may lead to dizziness, confusion, and muscular
- hyperventilation syndrome
- The syndrome of blurring of vision, (feeling of) tingling of the
extremities, faintness, and dizziness, which may progress to unconsciousness,
and convulsions, caused by reduction of the normal carbon dioxide tension of
the human body, due to increased pulmonary
- Pertaining to low atmospheric pressure, particularly the low atmospheric
pressure of high altitudes.
- Disturbances resulting from a decrease of ambient
pressure to less than that within the body fluids, tissues, and cavities.
- Deficiency of carbon dioxide in the blood and body tissues, which may
result in dizziness, confusion, and muscular cramps.
- hypothetical parallax = dynamic parallax.
- A respiratory-minute volume, or pulmonary
ventilation, that is less than normal. Also called underbreathing.
- The condition of reduction of the normal oxygen tension in the blood. Also
- Oxygen want or deficiency; any state wherein a physiologically inadequate
amount of oxygen is available to, or utilized by, tissue without respect to
cause or degree. Compare anoxia.
- 1. Any of several effects resembling a kind of internal friction,
accompanied by the generation of heat within the substance affected.
- Magnetic hystersis occurs when a ferromagnetic substance is subjected
to a varying magnetic intensity; electric hysteresis occurs when a dielectric
is subjected to a varying electric intensity. Elastic hysteresis is the
internal friction in an elastic solid subjected to varying stress.
- 2. The delay of an indicator in registering a change in a parameter being