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adial struts
radial struts Those connecting inner and outer ridge
main joints of airship transverse frames.
radial temperature distribution factor Circumferentially
measured combustor outlet peak gas temperature minus
outlet mean temperature divided by mean combustor
temperature rise.
radial velocity Velocity of approach or recession
between two bodies, ie component of relative velocity
along line connecting them.
radial wall jet Outward flow along ground beneath jetlift
aircraft or helicopter hovering in ground effect.
radial-wing configuration Use of several, eg four, wings
mounted radially to permit flight manoeuvre instantaneously
along any plane containing longitudinal axis
without prior need for roll.
radial wires Join vertices of airship’s main transverse
frames to central fitting or to those diametrically opposite.
radian SI unit of plane angle; angle subtended at centre
of circle by arc equal in length to diameter, rad = 57.2958°
= 57°17'44.8" = 0.1592 revolution.
radiant energy EM radiation, eg heat (IR), light, radio
and radar. Arguably, also occasionally used for other
energy, esp. acoustic.
radiant-energy density Instantaneous value for amount
of energy in unit volume of propagating medium, symbol
u. With pulse radars depends on pulse length and position.
radiant-energy thermometer Instrument which determines
black-body temperature; emitter need be ‘black’
only over range of wavelengths studied.
radiant flux Time rate of flow of radiant energy, ø.
radiant-flux density Radiant flux per unit area; when
applied to source, called radiant emittance, radiancy,
symbol W; when applied to receiver, called irradiance or
(not recommended) irradiancy, symbol H.
radiant intensity Radiant flux per unit solid angle,
measured in given direction, SI unit W/sr.
Radiant Mercury Software for sharing information,
including classified (DoD).
radiant temperature That recorded by total-radiation
pyrometer; when sighted on non-black body is less than
true temperature.
radiating element Any portion of radar aerial, esp. one
of electronically scanned type, which emits or reflects
transmitted energy.
radiation 1 Process by which EM waves are propagated.
2 Process by which other forms of energy are propagated,
eg heat from solid body, kinetic by ocean waves and
sound waves through atmosphere or other medium.
3 Other forms of energy propagation such as nuclear *,
high-energy ionising *, radioactivity.
radiation area Place where human being could receive
5+ mrem/h or total of 150 mrem in 5 consecutive days.
radiation belts Belts of charged particles trapped within
planetary magnetic field, esp. Van Allen belts.
radiation burn Damage to skin caused by ionising radiation.
radiation constants Two physical constants: First ** =
2πhc 2 = 3.7418 × 10 -16 Wm 2 ; Second ** = hc/k = 1.4388 ×
10 -2 mK.
radiation cooling Cooling by direct radiation from
surface, normally implying high temperature (eg rocket
thrust-chamber skirt).
radiation dose Amount of ionising radiation absorbed
radiator header
by substance, esp. over short period of time (see rad [3],
roentgen, rem).
radiation dose rate Dose per unit time.
radiation efficiency Ratio of power radiated to power
supplied to transmitting aerial at given frequency.
radiation field Volume occupied by radiation (1), esp.
that around conductor carrying AC or RF, comprising
electrical and magnetic (inductive) components.
radiation fog Usually shallow fog caused by radiative
cooling (often at night) of ground to below dewpoint,
combined with gentle mixing, saturation and condensation.
radiation hardening Gradual hardening and embrittlement
of most metals exposed to intense nuclear radiation,
resulting in limited choice of metals for high-integrity
structures in such environments.
radiation illness Disorders, some fatal, caused by
excessive exposure to ionising radiation.
radiation intelligence That derived from collection and
analysis of non-information-bearing radiation unintentionally
emitted by foreign devices, excluding that
generated by detonation of NW.
radiation intensity Radiation dose rate, normally that
measured in air. RI-3, eg, is value 3 h after NW burst.
radiation laws Those describing black-body radiation:
Stefan-Boltzmann, Planck, Kirchoff and Wien.
radiation lobe See lobe.
radiation medicine Branch dealing with radiation and
human beings.
radiation pattern Graphical representation of radiation
(1) of device, esp. radio, radar or similar emitting aerial,
plotted as field strength as function of direction. Normally
plotted as plan-view polar or as vertical cross-section, but
can be in plane of magnetic or electrical polarization of
waves. Free-space ** depends on wavelength, feed system
and reflector. Field** takes account of real situation in
which waves are reflected from ground or other objects so
that direct and reflected waves interfere with each other.
Also called coverage diagram, aerial (antenna) pattern,
lobe pattern.
radiation pressure That exerted on solid body by
incident radiation (1), symbol P r .
radiation pyrometer Pyrometer measuring light wavelengths
and giving readout in terms of temperature.
radiation scattering Diversion of radiation (EM,
thermal or nuclear) caused by collision or interaction with
atoms, molecules or large particles between source (esp.
NW explosion) and remote site; thus radiation is received
from many directions.
radiation sickness See radiation illness.
radiation situation map One showing actual and/or
predicted radiation situation, usually intensity, in particular
ground area.
radiation source Generally a man-made, portable,
sealed source of radioactivity.
radiator 1 Source of radiant energy, esp. EM or RF, eg
hostile operating radar.
2 Heat exchanger, esp. for rejecting unwanted heat to a
sink. Common usage restricts term to devices that dump
heat overboard, eg to atmosphere, and to call those that
use heat sink on board (eg fuel) heat-exchangers.
radiator header Tank in which liquid coolant is received
from heat source, eg engine, and distributed to cooling
elements, ie radiator(s).
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