A contour energy integral formulated by Rice and used for evaluating fracture
toughness of elastoplastic materials.
J-antenna
(NASA SP-7, 1965)
A half-wave antenna, end fed by a parallel-wire
quarter-wave section having the configuration of a J.
J-display
(NASA SP-7, 1965)
In radar, a modified A-display in which
the time base is a circle. The target signal appears as a radial deflection
from the time base. Also called J-scan, J-scope, J-indicator.
1. A covering or casing of some kind.
2. Specifically, a shell around the combustion
chamber of a liquid-fuel rocket,
through which the propellant is circulated in regenerative
cooling.
3. A coating of one material over another to prevent oxidation, micrometeoroid
penetration, etc.
Jacobian
(NASA SP-7, 1965)
The determinant formed by the n partial
derivatives of n functions of n variables, when the derivatives
of each function occupy one row of the determinant. For the case of two functions
f(x,y) and g(x,y) , the Jacobian J(f,g) is
Sometimes written
.
Jahn-Teller effect
(NASA Thesaurus)
The effect whereby, except for linear molecules, degenerate orbital states
in molecules are unstable.
jamming
(NASA Thesaurus / NASA SP-7, 1965)
Intentional transmission or reradiation
of radio signals in such a way as to interfere
with reception of desired signals by the intended receiver.
Janus
(NASA Thesaurus)
One of the natural satellites of Saturn.
Japanese spacecraft
(NASA Thesaurus)
Spacecraft operated by the Japanese government. Used for MOS (Japanese
spacecraft).
JATO, Jato, or jato
(NASA SP-7, 1965)
(From jet-assisted take-off ).
1. A take-off utilizing an auxiliary jet-producing unit or units, usually
rockets, for additional thrust. Hence JATO bottle, Jato unit , etc.;
a rocket or unit so used. Where rockets are the auxiliary units, RATO
(which see) is the more specific term.
2. A JATO bottle or unit; the complete auxiliary power system used for assisted
take-off.
jerk
(NASA SP-7, 1965)
A vector that specifies the time rate of change
of the acceleration; the third
derivative of displacement with respect to time.
jerkmeter
(NASA SP-7, 1965)
An instrument for measuring the magnitude of the time rate of change of
acceleration.
jet
(NASA SP-7, 1965)
1. A strong well-defined stream of fluid either
issuing from an orifice or moving in a contracted duct, such as the jet of
combustion gases issuing from a reaction
engine, or the jet in the test section of a wind
tunnel. See free jet.
2. A tube, nozzle, or the like through which fluid passes, or from which it
issues, in a jet, such as a jet in a carburetor. See metering
jet.
3. A jet engine, as, an airplane with jets slung in pods.
jet engine
(NASA Thesaurus / NASA SP-7, 1965)
1. Broadly, and engine that ejects a jet
or stream of gas or fluid, obtaining all or most of its thrust by reaction
to the ejection. See reaction engine.
2. Specifically, an aircraft engine that derives all or most of its thrust
by reaction to its ejection of combustion products (or heated air) in a jet
and that obtains oxygen from the atmosphere for the combustion of its fuel
(or outside air for heating, as in the case of the nuclear jet engine), distinguished
in this sense from a rocket engine. A jet
engine of this kind may have a compressor,
commonly turbine-driven, to take in and compress air (turbojet), or it may
be compressorless, taking in and compressing air by other means ( pulsejet,
ramjet).
jet lag
(NASA Thesaurus)
Desynchronization of biological rhythms because of transmeridian flight.
jet membrane process
(NASA Thesaurus)
Method for separating or enriching isotopes of the same element by using
a condensable vapor as the carrier fluid. A process gas containing the isotopes
enters a chamber into which a heavy condensable gas (the jet) flows. The lighter
of the two isotopes is enriched, relative to the heavier species, and is collected
by a probe downstream for further enrichment or analysis.
jet nozzle
(NASA SP-7, 1965)
A nozzle, usually specially shaped, for producing
a jet, such as the exhaust nozzle on a jet or rocket engine.
See rocket nozzle.
jet propulsion
(NASA SP-7, 1965)
1. The propulsion of a rocket or other craft
by means of a reaction engine.
2. = duct propulsion. Duct propulsion and rocket propulsion are the two forms of jet propulsion.
jet stream
(NASA Thesaurus / NASA SP-7, 1965)
A strong band of wind or winds in the upper troposphere
or in the stratosphere, moving in a general
direction from west to east and often reaching velocities of hundreds of miles
an hour. See jetstream, note.
jet thrust
(NASA Thesaurus / NASA SP-7, 1965)
The thrust of a fluid,
especially as distinguished from the thrust of a propeller. The thrust of
a rocket engine is calculated in the same manner as gross thrust of a jet
engine. See gross thrust.
jet vane
(NASA Thesaurus / NASA SP-7, 1965)
A vane, either fixed or movable, used in a jetstream,
especially in the jetstream of a rocket, for purposes
of stability or control under conditions where external aerodynamic
controls are ineffective. Also called blast vane. Compare air
vane.
jetavator
(NASA SP-7, 1965)
A control surface that may be moved into or against a rocket's jetstream,
used to change the direction of the jet flow for thrust vector control. Compare
jet vane.
jets
(Imagine the Universe Dictionary - NASA GSFC)
Beams of particles, usually coming from an active galactic nucleus or a
pulsar. Unlike a jet airplane, when the stream of gas is in one direction,
astrophysical jets come in pairs with each jet aiming in opposite directions.
jetstream
(NASA SP-7, 1965)
A jet issuing from an orifice into a medium with much lower velocity, such
as the stream of combustion products ejected from a reaction
engine. In the meteorological sense jet stream is two words, see following definition,
but in the sense defined above, one word.
JFET
(NASA Thesaurus)
Junction field effect transistors in which semiconductor channels of low
conductivity join the source and drain and in which these channels are reduced
and cut off by the junction depletion regions, which reduce the conductivity
and cause a voltage to be applied between the gate electrodes. Used for junction
field effect transistors.
jitter
(NASA SP-7, 1965)
1. Instability of the signal or trace of a cathode-ray
tube.
2. Small rapid variations in a waveform due
to deliberate or accidental electrical or mechanical disturbances or to changes
in the supply voltages, in the characteristic of components, etc.
JNC--Jet Navigation Chart
(Global Land Information System Glossary - USGS)
The JNC series provides worldwide coverage at 1:2,000,000 scale. The information
on these charts are suitable for aeronautical long-range, high-altitude, high-speed
travel; map features include cities, roads, railroads, lakes, principal drainage,
and permanent snow/ice areas. The polar regions are in a Transverse Mercator
projection. All other regions are presented in the Lambert Conformal Conic
projection.
Jodrell Bank
(NASA SP-7, 1965)
The site of a large radio telescope,
located near Manchester, England; by extension, the radio telescope itself.
The radio telescope has a paraboloidal receiver 250 feet in diameter,
60 feet deep.
Jodrell Bank Observatory
(NASA Thesaurus)
A large radio telescope, located near Manchester, England.
The earliest predecessor organization and facility of the Atlantic Missile
Range, activated at Cape Canaveral 1 October 1949 as a joint undertaking of
the Air Force, Army, and Navy under the executive control of the Chief of
Staff, USAF. This facility became the sole responsibility of the Air Force on 16 May
1950, and became known as the Florida Missile Test Range.
Joule
(From Stargazers to Starships Glossary - GSFC)
Unit of energy: the ability to overcome one Newton along 1 meter (assuming
g = 10 meter/sec[superscript]2, it is also the energy required to lift 1 kg
by 0.1 meters). Named for James Prescott Joule, one of the first to measure
the "rate of exchange" between mechanical energy and heat.
joule
(NASA SP-7, 1965)
(abbr j)
A unit of energy or work in the MKS system;
the work done when the point of application of 1 newton
is displaced a distance of 1 meter in the direction of the force. 1 joule = 10E7 ergs = 1 watt second.
Joule constant
(NASA SP-7, 1965)
The ratio between heat and work units from experiments based on the first
law of thermodynamics: 4.1858 X 10E7 ergs per 15 degrees calorie. Also
called mechanical equivalent of heat.
Joule cycle
(NASA SP-7, 1965)
(After James Prescott Joule, 1818-89, English physicist). An ideal cycle
for engines consisting of isentropic compression
of the working substance, addition of heat at constant pressure, isentropic
expansion to ambient pressure, and exhaust at constant pressure. Also called
Brayton cycle.
The decrease in temperature which takes place when a gas expands through
a throttling device such as a nozzle. Also called Joule-Kelvin effect.
The rate of change of temperature T with pressure p in the Joule-Thomson
effect is called the Joule-Thomson coefficient (symbol µ):
where h denotes constant enthalpy. For the Joule-Thomson effect to take
place the gas must initially be below its inversion temperature; if above
the inversion temperature, the gas will gain heat on expansion. The inversion
temperature of hydrogen, for example, is approximately -183º C.
journal bearings
(NASA Thesaurus)
Bearings that support the cylindrical journal of a shaft in rotating machinery.
Jovian
(NASA SP-7, 1965)
(Latin Jovis, genitive of Jupiter) Of or pertaining to the planet Jupiter;
associated with Jupiter; or similar to Jupiter, as in Jovian planet.
Jovian planet
(NASA SP-7, 1965)
Any one on the giant planets: Jupiter, Saturn, Uranus, or Neptune. Usually
in plural Jovian planets.
A liquid fuel for jet and rocket engines, the chief ingredient of which
is kerosene.
JPL
(Space Flight Glossary - JPL)
Jet Propulsion Laboratory, operating division of the California Institute
of Technology.
Julian calendar
(From Stargazers to Starships Glossary - GSFC)
Introduced in 46 BC by the Roman ruler Julius Ceasar, this calendar assumes
a year of 365.25 days, and uses a cycle in which 3 "ordinary" years of 365
days are followed by a "leap year" with 366 days. Leap years are the years
whose number is divisible by 4.
Julian day
(NASA SP-7, 1965)
The number of each day, as reckoned consecutively since the beginning of
the present Julian period on January 1, 4713 B.C. The Julian day is used primarily by astronomers to avoid confusion due
to the use of different calendars at different times and places. The Julian
day begins at noon, 12 hours later than the corresponding civil
day. The day beginning at noon January 1, 1965, is Julian day 2,438,395.
