Aerospace Science and Technonlogy Dictionary Z Section

Z: Zulu in phonetic alphabet, stands for GMT.
z-time: = Greenwich mean time.
Zarya control module: Component of the International Space Station providing propulsion, steering, and communications during the early assembly stages of the station; later serving as a docking port and fuel tank. Zarya was built by Russia under contract to the U.S. and is owned by the U.S.
Zeeman effect: The splitting of the lines in a spectrum when the source is exposed to a magnetic field. It is used to measure magnetic field strengths on the Sun and on other astronomical objects.
zenith: That point of the celestial sphere vertically overhead.
The point 180 degrees from the zenith is called the nadir.
zenith attraction: The effect of the earth's gravity on a meteoric body, which increases the velocity and moves the radiant toward the zenith.
zenith distance: Angular distance from the zenith; the arc of a vertical circle between the zenith and a point on the celestial sphere, measured from the zenith through 90 degrees, for bodies above the horizon.
This is the same as colatitude with reference to the celestial horizon.
zenithal: Of or pertaining to the zenith.
zenographic: Referring to positions on Jupiter measured in latitude from Jupiter's equator and in longitude from a reference meridian.
zero gravity: = weightlessness.
zero launch: The launch of a rocket or aircraft by a zero-length launcher.
zero point energy: Kinetic energy retained by molecules of a substance at a temperature of absolute zero.
zero-g: = weightlessness.
zero-length launcher: A launcher that holds a vehicle in position and releases the rocket simultaneously at two points so that the buildup of thrust, normally rocket thrust, is sufficient to take the missile or vehicle directly into the air without need of a take-off run and without imposing a pitch rate release.
The term is not normally applied to a pad used for a vertical launch.
zero-length rocket: A rocket with sufficient thrust to launch a vehicle directly into the air.
Said especially of a rocket used to launch an aerodynamic vehicle.
zero-lift chord: A chord taken through the trailing edge of an airfoil in the direction of the relative wind when the airfoil is at a zero-lift angle of attack.
zeta machine: An experimental thermonuclear device which generates a plasma inside a torus and employs the pinch effect for heating and compression.
zeta pinch: Type of plasma pinch produced by an electric current applied axially to a plasma cylinder in a controlled fusion reactor.
zinc chlorides: Reaction products of hydrochloric acid and zinc; white crystals soluble in water and alcohol and with a melting point of 290 degrees C.
zinc-bromide batteries: Electric cells in which during charge, zinc is plated on the anode and bromine is evolved at the cathode. The bromine is transferred to an external chamber for mixing and storing with an organic liquid complexing oil. During discharge, the zinc is oxidized at the anode and the complexed bromine is reduced at the cathode.
zinc-chlorine batteries: Candidate electric cells under development for electric vehicles.
zincblende: Zinc sulfide, ZnS; a cubic crystal. Used for sphalerite.
zip fuel: A boron-base high-energy liquid propellant.
zippers: Slide fasteners consisting of interlockable elements each attached to one of the opposing edges of two tapes and a movable part called a 'slider' that spans the interlockable elemets, which when moved in one direction causes the elements of one tape to interlock with the elements on the other tape, and when moved in the opposite direction causes the elements to disengage.
zodiac: Twelve constellations dividing the ecliptic into approximately equal parts. Each month the Sun is in a different constellation of the zodiac.
zodiac: The band of the sky extending 8 degrees either side of the ecliptic.
The Sun, Moon, and navigational planets are always within this band, with the occasional exception of Venus. The zodiac is divided into 12 equal parts, called signs, each part being named for the principal constellation originally within it.
zodiacal counterglow: = gegenschein.
zodiacal light: A pale glow sometimes visible in the night sky in the path of the Earth's orbit around the Sun. (The constellations in this path make up the zodiac). It is caused by the scattering of sunlight off of dust in the plane of Earth's orbit.
zodiacal light: A faint cone of light extending upward from the horizon in the direction of the ecliptic (zodiac). It is seen from tropical latitudes for a few hours after sunset or before sunrise.
The spectrum of the zodiacal light is similar to that of sunlight, so it has been suggested that it is due to the scattering of sunlight by extraterrestrial dust particles. Some scattering is also due to electrons.
zonal flow: Large-scale atmospheric flow in which the east-west component (i.e., latitudinal) is dominant. The accompanying meridional (north-south) component often is weaker than normal. Compare with meridional flow.
zone time: See time.
zooplankton: The aggregate of passively floating or drifting animal organisms in aquatic ecosystems.
Zurich number: = relative sunspot number