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burn in 1 To enter data in EDP core store so that it will
subsequently resist nuclear explosion effects and other
hostile action.
2 To operate avionic and other electronic equipment
under severe overload conditions to stabilize it before
operational service and reduce incidence of faults.
burnish To smooth and polish metal surface by rubbing
(usually with lubricant) with convex surface of harder
metal.
burn-off In aeroplane (esp. commercial transport) operation,
fuel burned between takeoff and critical position
for establishing terrain clearance.
burnout 1 Termination of rocket operation as result of
exhaustion of propellants. Also called all-burnt.
2 Mechanical failure of part subject to high temperature
as result of gross overheating, esp. rocket case or
chamber.
burnout plug In certain rocket motors, esp. storable
liquid and hybrid types, combustible plug which, when
ignited, releases and fires liquid propellant.
burnout velocity Vehicle speed at burnout (theoretically,
highest attainable for given trajectory).
burnout weight Mass of vehicle at burnout, including
unusable fuel.
burn rate In solid rocket, linear velocity of combustion
measured (usually in millimetres per second) normal to
burning surface. Symbol r.
burn-rate constant Factor applied to ** calculations
dependent upon initial grain temperature.
burn-rate exponent Pressure exponent n in burn rate law
r = aP n c.
burn table Refractory surface in tail of plume target on
which jet fuel is burnt.
burn-through Operation of radar in face of jamming and
similar ECM, esp. by virtue of high transmission power to
overcome interference.
burn-through range Limit of range at which *-* operation
can yield useful information, if necessary in
emergency short-life operation at abnormally high power.
burn time Duration in seconds of rocket motor burn.
Burn time starts when chamber pressure has risen to 10%
of maximum (or averaged maximum during level portion
of thrust curve) and ends when pressure drops to 75%.
Alternative criterion is to draw tangents to level portion
and descending portion of thrust curve and measure time
to point at which curve is cut by bisector of angle between
tangents. Symbol tb .
burn-time average chamber pressure Integral of chamber
pressure versus time taken over burn time interval divided
by burn time. Symbol P – c.
burn-time average thrust Integral of thrust versus time
taken over burn time interval divided by burn time.
Symbol F – b.
burnup 1 On entry to atmosphere from space, partial or
complete destruction due to kinetic heating.
2 In nuclear reactor, esp. thermal fission reactor,
percentage of available fissile atoms that have undergone
fission.
BURR Basic unscheduled removals rate.
Burro Broad-area unmanned responsive resupply
operations.
burst In colour TV, transmission of small number of
cycles of chroma sub-carrier in back-porch period (in military
systems this signal not always used).
buster
2 One round (payload) of ECM dispensed from
attacking vehicle; can be active jammer or flare.
3 Period of fire by automatic gun[s].
4 See turbulent *.
5 Catastrophic failure of a rotating part, especially
turbofan fan hub.
burst controller Burst limiter.
burst criteria Design of fan disc to ensure that it will
survive any overspeed condition.
burst diaphragm Diaphragm sealing fluid system and
designed to rupture either upon command or at predetermined
dP.
burst height Height at which nuclear weapon is
programmed to detonate.
burst limiter Preset control of number of rounds to be
fired in burst (3).
burst order Detonation of missile warhead by
command.
BUS 1 Break-up system (of unmanned vehicle upon
command).
2 Backscatter ultraviolet spectrometer.
bus 1 Spacecraft carrier vehicle for various payloads.
2 In EDP, main route for power or data. Alternatively,
trunk.
3 Busbar.
4 In ICBM, carrier vehicle for MIRV payloads.
5 In any delivery system, carrier vehicle for multiple
warheads or submunitions
6 A particular aeroplane (affectionate usage, UK
c 1910–30).
busbar In elecrical system, main conductor linking all
generators and/or batteries and distributing power to
operative branches.
Busemann biplane Aeroplane, so far not built, in which
at supersonic speed shockwaves and flows around upper
and lower wings would react favourably.
Busemann theory First theory for two-dimensional
supersonic wing to take into account second-order terms
(1935).
bush Open-ended drum tailored to fit inside hole, eg to
reduce its diameter, act as shaft bearing or serve as
electrical insulation (see grommet).
bush aircraft Aerodyne tailored to utility service in
remote (eg Canadian Arctic) regions.
bushie Bush pilot (Australia).
bush pilot Operator (often also owner) of bush aircraft,
usually freelance jobbing professional.
business aircraft Aerodyne tailored to needs of business
management and executives of government and other
organisations.
Business Class Airline passenger category between
Tourist and First; no universal definition of seat pitch or
services provided.
business engineering BE, a business integration strategy
based on net value to the business, not functional
optimisation.
business jet Rapidly growing class of business aircraft,
abb. bizjet, subdivided by passenger seating into: micro