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- 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
- 3. A coating of one material over another to prevent oxidation,
micrometeoroid penetration, etc.
- 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
- Intentional transmission
or reradiation of radio signals in such
a way as to interfere with reception of desired signals by the intended
- A half-wave antenna, end
fed by a parallel-wire quarter-wave section having the configuration of a J.
- JATO, Jato, or jato
- (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
- 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.
- A vector
that specifies the time rate of change of the acceleration;
the third derivative of displacement with respect to time.
- An instrument for measuring the magnitude of the time rate of change of acceleration.
- 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
- 3. A jet engine, as, an airplane with jets slung in pods.
- 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.
- jet engine
- 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 nozzle
- A nozzle,
usually specially shaped, for producing a jet, such as the
exhaust nozzle on a jet or rocket engine. See rocket
- jet propulsion
- 1. The propulsion of a rocket or other
craft by means of a reaction
- 2. = duct
- Duct propulsion and rocket propulsion are the two forms of jet
- A jet issuing from an orifice into a medium with much lower velocity, such
as the stream of combustion products ejected from a reaction
- In the meteorological sense jet stream is two words, see following
definition, but in the sense defined above, one word.
- jet stream
- 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,
- jet thrust
- 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
- jet vane
- 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.
- J-indicator = J-display.
- 1. Instability of the signal or trace of a cathode-ray
- 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.
- Jodrell Bank
- The site of a large radio
telescope, located near Manchester, England; by extension, the radio
- The radio telescope has a paraboloidal receiver 250 feet in diameter,
60 feet deep.
- Johnson noise
- See thermal
- Joint Long Range Proving Ground
- 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
- This facility became the sole responsibility of the Air Force on 16 May
1950, and became known as the Florida Missile Test Range.
- joule (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
- 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
- (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.
- Joule-Kelvin effect = Joule-Thomson effect.
- Joule-Thomson coefficient (symbol μ)
- See Joule-Thomson
- Joule-Thomson effect
- The decrease in temperature which takes place when a gas expands through a
throttling device 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 -183 degrees C.
- (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
- Any one on the giant planets: Jupiter, Saturn, Uranus, or Neptune. Usually
in plural Jovian planets.
- JP (abbr) = jet propulsion
- Compare RP.
- A liquid fuel for jet and rocket engines, the chief ingredient of which is
- J-scan = J-display.
- J-scope = J-display.
- Julian day
- 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.
- Julian period
- See Julian day.
- In computer programming, to cause the next instruction
to be selected conditionally or unconditionally from a specified storage
- A short length of conductor used to complete an electrical circuit,
usually temporary, between terminals, or to bypass an existing circuit.
- In a semiconductor
device, a region of transition between semiconducting regions of different
- junction point = node.
- June solstice = summer solstice.
- See planet, table.
- Jupiter I = Io.
- Jupiter II = Europa.
- Jupiter III = Ganymede.
- Jupiter IV = Callisto.