DSA Volume 1 Issue 4 December 2010 - Defence Science and ...

VOLUME 1 ISSUE 4 DECEMBER 2010 | ISSN 1837-8404 and ISSN 1838-0093 (Online)
A U S T R A L I A
Better understanding of
crowd behaviour
Using sound to test
soundness of aircraft parts
Detecting substances
with laser light
1

The Defence Science and Technology
Organisation (DSTO) is part of the
Department of Defence and provides
scientific advice and support to the
Australian Defence Organisation. DSTO
is headed by the Chief Defence Scientist,
Professor Robert Clark, and employs
about 2300 staff, including some 1300
researchers and engineers. It is one of
the two largest research and development
organisations in Australia.
Defence Science Australia is published
quarterly by DSTO’s Defence Science
Communications. Unless labelled copyright,
material may be reproduced freely with
acknowledgement.
Managing Editor: Jimmy Hafesjee
e-mail: jimmy.hafesjee@dsto.defence.gov.au
Editor: Tony Cox
e-mail: dsaeditor@dsto.defence.gov.au
Design and illustration: Anna Antonopoulos
Media enquiries: Karen Polglaze
Phone: 61 2 6128 6384
e-mail: media3@dsto.defence.gov.au
Mailing list enquiries:
e-mail: dsaeditor@dsto.defence.gov.au
More information is available about
DSTO on its web site at:
www.dsto.defence.gov.au
ISSN 1837-8404
ISSN 1838-0093 (Online)
Contents
1 Radar study tool innovation goes directly to work
2 Tiny light-based glass fibre sensors with a big future
4 Crowd behaviour analysis to understand the milling monster
6 A better analytical tool for ‘hit or miss’ situations
8 Sound way of detecting hidden aircraft flaws
10 Improved sonar pictures of a noisy changeable ocean
12 Robust and reliable radio performance in any environment
13 Briefs
Getting the sulphur chemistry right for Defence aviation fuels
Thermal boost for unmanned aircraft performance
New weapons fragmentation recovery facility
14 Calendar of events
Cover image: Researcher at the Institute for Photonics and Advanced Sensing with
optical fibre sensor.
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Radar study tool innovation
goes directly to work
A device developed by
DSTO for use in radar
research has gone
virtually straight from
the laboratory bench
into real-world service,
earning accolades from
users around the world.
The apparatus, named the ‘G-Box’ after
its principal developer, Gavin Scarman,
provides an innovative way of gathering
remote phenomenological information
associated with wide bands of highfrequency
(HF) radar transmissions.
“G-Box consists of a digital HF receiver and
timing signal electronics, packaged together
in a small ‘ruggedised’ container, making
it ideally suited to field use under a wide
range of conditions,” explains Scarman.
“Taking an earlier radar receiver system
developed for the Jindalee Over The
Horizon Radar as our starting point, a team
of DSTO’s researchers came together to
develop powerful and versatile firmware
and software for a new kind of apparatus
that would deliver significant advances.”
Flexible, adaptable research tool
The result is a system that provides a cheaper
and more versatile means of undertaking a
number of radar-related research activities,
seen to be far better than those of any other
commercially available product at present.
One of the principal uses it can be applied
to is that of obtaining readings of the state
of the ionosphere, a critical requirement
when evaluations of over-the-horizon radar
system performance are to be carried out.
The G-Box can also serve as a radar receiver,
and if several units are combined, it is capable
of emulating a sophisticated kind of radar
system known as a large aperture array.
From DSTO’s benches to the world
Some twenty G-Box units have now been
produced by DSTO, and a number of these
have gone on loan to organisations both
inside and outside of military circles.
One is in use by the Australian Bureau of
Meteorology to facilitate studies of the
ionosphere above Antarctica. Other places
where G-Box has been put to work include
North Western Australia and the US.
Most notably, the G-Box played a pivotal
role in the joint Australian-US Spatial
Ionospheric Correlation Experiment
campaign, undertaken recently in
the Caribbean to facilitate improved
performance for over-the-horizon radar
systems. The success of this work was
acclaimed by the US Navy Research
Labs in its 2010 Annual Research Awards.
With much having been learnt about
G-Box’s performance through these realworld
uses, the development team is
drawing on this experience to produce
an improved version, to be known as
the Next Generation Radar Receiver.
Background photo: Antenna (centre of image) used during the recent Spatial Ionospheric Correlation Experiment campaign in Caribbean.
Overlay image above: The G-Box system (second from bottom in equipment rack) in use during the Caribbean trials.
Above: The G-Box system with laptop screen featuring HF data obtained.
1

Tiny light-based glass fibre
sensors with a big future
DSTO is collaborating with the Institute of Photonics & Advanced Sensing (IPAS) to
develop new ways of sensing the composition and condition of materials with laser
light guided in ‘microstructured’ optical fibres.
IPAS is a recently established research
institute that builds on the Centre of
Expertise in Photonics (CoEP) established
at the University of Adelaide in 2005. The
institute was set up with support from DSTO
along with several other organisations.
CoEP researchers have for a number of years
been developing techniques to make optical
fibres using non-silica ‘soft glasses’. These
glasses, unlike the hard kind, have the ability
to transmit light in the mid-infrared frequency
range, making it possible to develop several
important applications of interest to Defence.
Additionally, because soft glasses melt at
lower temperatures, they are amenable to
production methods that enable the creation
of fibres with arrays of air holes running the
length of the fibre, known as microstructures.
Microstructure features provide a new
way of containing light inside a fibre, without
which, it would quickly dissipate through the
sides. The previous method of containment
required using two kinds of compatible
glasses with different refractive indices for
core and cladding.
The advent of microstructure designs thus
enables optical fibres to be made with just
one kind of glass, greatly increasing the range
of materials that can be transformed into
optical fibres.
Moreover, microstructure fabrication
techniques have advanced to the point where
structures can be produced with features
as small as 20 nanometers – significantly
smaller than the wavelength of light. This
opens up extraordinary new possibilities for
optical fibre use.
Biological and chemical signal sensors
One such use is for sensors that can
analyse liquids or gasses. IPAS is
investigating the possibility of developing
various real-world applications.
“The new optical fibres we’ve developed
use a suspended glass nanorail to guide
light. This nanorail serves as the sensing
platform, allowing light to interact with the
environment in which it is embedded, or into
which it is dipped,” explains IPAS Director
Professor Tanya Monro.
“Because a significant proportion of the
light guided by the fibre falls outside of
the glass, this can be used as a means for
sensing conditions in the immediate locality
by observing how it interacts with particular
kinds of matter present.”
The sensing apparatus consists of a laser
light source, a length of fibre optic cable
with one or more small sensing regions, and
a detector. A sensing region can be exposed
to the external environment, or alternatively,
the material to be sensed can be loaded into
holes within the fibre.
The IPAS work on sensing for defence
applications currently involves the use
of sensors with surfaces prepared in ways
that react only to molecules associated
with a certain type of material – such as an
explosive, biological agent or contaminant –
to determine whether that material is
present or not.
“When particular molecules of interest are
present, they bind to the specially prepared
surfaces, and under stimulation by laser light,
fluorescence occurs, which the system then
detects,” says Professor Monro.
The fluorescent light further provides a
measure of the relative quantity of such
molecules present, as revealed by the light
intensity levels detected.
High-tech dipstick
Liquid samples can be assayed in such a
way using an optical fibre with a central core
surrounded by air holes. The liquid is drawn
into the fibre by capillary action or forced up
into the holes by pressure.
The volume needed for accurate
sampling is extremely small, just nanolitres
(10 -9 litres). Concentrations of chemicals and
biomolecules as low as 0.2 nanomoles can be
detected even when assaying sample volumes
this small, and further improvement in the
detection limit is expected in the future.
The fact that the fluorescing light travels
in both directions means it can be observed
at either end of the fibre. This makes possible
the development of a continual automated
monitoring application in the form of a
‘dip-sensor’.
The system involves a length of optical fibre,
with laser light being sent at one end, a liquid
sample entered into it at the other end, and
a detector for fluorescence mounted at the
same end as the laser light source.
The dip-sensor, involving no moving parts
and no electronics, need only contact the
liquid surface to facilitate a reading. Being
very small and robust, such devices could
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eventually be built into storage tanks,
thereby obviating the need to open the
tank for sampling and eliminating the risk
that the contents may spoil or be exposed
to contamination.
Jet fuel monitoring
One possible application of considerable
interest to the Australian Defence Force
(ADF) is for monitoring aircraft fuel quality.
Fuel has a dual role in modern jet aircraft,
providing not only engine power but also
cooling for the engines, with fuel being
circulated around engine parts to draw
away heat that would otherwise cause
damage over time.
The effect of the heat on fuel, however, is to
cause quality degradation that diminishes
engine performance and the life of certain
parts. Fuel degradation can happen
very quickly, and occurs in somewhat
unpredictable ways, so the ability to
monitor in situ for impending degradation is
seen to offer a valuable management tool.
Optical fibre sensing technology can
do so via use of a sensor chemically
sensitised to detect hydroperoxide, the
presence of which indicates the initial state
of fuel degradation.
This form of monitoring, producing virtually
instantaneous results in support of real-time
decision-making, could also be used for
monitoring the quality of other fluids such
as turbine oils and hydraulic fluids.
Sensing the effects of corrosion
Another application of major interest to
the ADF is that of detecting corrosion on
aircraft structures.
Aircraft maintenance inspections are
currently difficult, costly and timeconsuming,
and in some cases, involve the
dismantling of aircraft structures for manual
inspection of hard-to-access parts.
The development by IPAS of open-core
chemically sensitised sensors that fluoresce
in the presence of aluminium ions, a
corrosion by-product of aluminium
structures, promises to significantly improve
this situation.
To monitor alloy condition at a particular
site, a sensor with fully exposed core is laid
over it. Multiple sensors can be fabricated
into a single optical fibre, with monitoring
undertaken via pulsed laser light emissions
that elicit time-series sets of fluorescence
spectra ‘echoes’.
Any such echoes detected indicate not only
that corrosion is happening, and how much is
happening, but also where it is happening, as
revealed by the time of signal return.
The eventual aim of the work is to allow for
corrosion monitoring through a simple check
of signals from sensors built into aircraft at
each site where corrosion is known to be a
problem, thereby greatly reducing inspection
costs and aircraft downtime.
DSTO support for the research
DSTO’s Corporate Enabling Research Program
(CERP) in Signatures, Materials and Energy
is supporting the IPAS research on corrosion
detection and fuel degradation monitoring
through top-up scholarships awarded to
Stephen Warren-Smith and Erik Schartner for
their doctoral studies in these areas.
“The joint IPAS-DSTO programs in corrosion
detection and fuel degradation monitoring
offer highly innovative approaches and
promising solutions to long-standing
issues affecting the availability and cost-ofownership
of ADF assets,” says CERP Program
Leader, Dr Christine Scala.
The various kinds of microstructured sensors
in development are expected to be available
for field-testing within two to five years.
Opposite page: Design for nanorail optical fibre in the preform stage of production.
Top: IPAS optical fibre sensor apparatus for assaying liquid sample.
Above: Close-up of IPAS optical fibre sensor components.
3

Crowd behaviour analysis to
understand the milling monster
DSTO is developing crowd
behaviour modelling that
improves on the complexity
of situations simulated, and
also provides a capability for
making predictions of crowd
motions, thus allowing for
more effective intervention
measures overall.
The work began as ‘blue sky’ research
initiated in DSTO by Dr Darryn Reid. His
interest in crowd behaviour was inspired
by observations of actual events, such
as pilgrimage processions and football
matches, having noted that crowds
now feature increasingly prominently
in Army operational environments.
“Crowds assembled for some common
purpose or interest may appear to flow in
a stable orderly manner, but after some
seemingly trivial change or interruption, as
happens when a person stumbles or turns in
the opposite direction, chaos of disastrous
proportions can ensue with widespread
injuries and loss of life,” he says.
Concern
The way in which crowds move is thus of
central concern to military commands as
well as civilian authorities and disaster
relief agencies. Some scenarios of interest
include civilians passing through a combat
zone to escape conflict, and persons
fleeing natural disasters such as tsunamis,
earthquake and fire – the latter being of
particular significance within Australia.
The need for insightful analysis to inform
incident prevention and management
becomes even more apparent with the
knowledge that some outcomes are counterintuitive.
In one such example, a column
put inside the doorway of a building,
partially obstructing movement, can actually
smooth crowd flows. Another example is
that the use of roadblocks to control traffic
flows during a bushfire emergency can
make flow conditions more unstable.
After looking at existing crowd behaviour
models, Dr Reid found they offered
somewhat limited capabilities. Firstly,
they were only able generally to simulate
crowd behaviour in simple confined
spaces, such as a stadium or building
interior. Secondly, the simulations were
descriptive only, offering no understanding
as to why behaviour may change, and
with no ability to predict this change.
Teaming up with fellow DSTO mathematician
Dr Vladimir Ivancevic, he set about
investigating ways of improving on the
simulation capabilities available.
New way of modelling
crowd behaviour
A basic problem identified by the DSTO
researchers with previous models was
that they derived states for crowd
behaviour by calculating the state of
each individual component and adding
all of these to produce a sum effect – a
‘bottom-up’ form of approach.
The DSTO view of things is somewhat more
complex. “The individual has an effect on
the crowd and the crowd also influences the
behaviour of the individual, so there is an
interactive process involved,” says Dr Reid.
“This is why crowd movement is
chaotic, which is to say, the outcome is
exquisitely sensitive to small changes
in conditions and earlier events.”
His analysis proposes a system with
three levels in play simultaneously;
the individual, the overall crowd,
and a meso level in between where
aggregate motions are formulated.
“Only by representing what’s going on at
these three levels simultaneously can we
expect to characterise the different overall
chaotic motions and sudden changes of
motion – called phase transitions – that
real crowds can display,” says Dr Reid.
Entropy and crowd behaviour
Another major difference to previous
modelling is the use of a theoretic
framework based on entropic geometry,
entropy being a measure of the level
of disorder that exists in a system.
Out of this has come an approach
Dr Reid terms ‘behavioural composition’
that draws together previous
approaches in a single framework.
“Whereas other models see either the
whole emerging from its parts, or the
whole being reduced to its parts, our
approach attempts to unify both notions.
“Simulating crowd behaviour processes
in this way requires solving what
mathematicians refer to as ‘large coupled
systems of nonlinear Schrödinger equations’.
“For this purpose, we therefore need not only
vast amounts of computing power, but also
algorithms that can accurately solve these
large and complex systems of equations
without the results becoming effectively lost
in numerical noise – and both of these needs
pose major practical problems,” he says.
A further significant aspect of DSTO’s
modelling approach, the use of quantum
probability theory, deftly solves an intractable
problem facing previous approaches and
also gives it a predictive capability.
In previous approaches, modelling of
individual behaviours with high accuracy
was required in order to arrive at an
accurate aggregate crowd model, which is
extremely difficult. This difficulty can be
avoided using a probability theory approach
because, even though the motions of
individuals cannot be predicted with any
accuracy, those of the crowd overall can.
The way is then made open to not only
describe the chaotic motions of a crowd at
any time but to also generate predictions of
likely motions for a given set of preconditions.
More realistic environments
for scenario studies
In addition to the advances being made
in modelling crowd behaviour processes,
the research has arrived at modelling
capable of simulating crowd events in
more complex environments. These
involve a mix of terrain types, rural and
urbanised, some parts freely traversable
and some more constricted, with crowd
flows taking multiple paths through them.
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DEFENCE SCIENCE AUSTRALIA
The modelling includes details as small as
individual trees and shrubs, the presence
or absence of which can have significant
effects on pathways taken, and thus,
simulation outcomes. This approach to
terrain modelling more accurately represents
the real-world conditions in which many
large-scale human movements occur.
In the demonstration models developed by
DSTO to date, one of the most advanced
environments is a rural environment with a
country town threatened by an approaching
bushfire front. Another is a model of a
city environment facing a fire threat.
The initial conditions for these can be set in
various ways to study different problems.
Outcomes are delivered both in numerical
form as probabilities that particular
eventualities will occur, and as threedimensional
(3-D) animations of the
event that can be observed on screen.
The outcomes given include not only the
direction of travel of the crowd but also the
mood prevalent, and any changes arising.
Verifying the modelling will be carried
out by running simulations of a readily
observable real-world situation, such as
rush-hour crowd flows in a city setting,
and studying the outcomes compared to
data and video footage obtained from
actual events. Initial work has shown the
models to produce true-to-life outcomes.
Developmental challenges
Despite the seemingly advanced state
of the work, the researchers are in fact
still defining the problems associated with
producing this capability. So far, various
approaches have been devised and then
tested for limitations – ‘looking for things
to break’, as Dr Reid puts it – to see
where further development is required.
Drs Reid and Ivancevic are confident,
meanwhile, that the basic framework
of approach adopted is viable for the
modelling capability they want to deliver.
With some simulations currently taking
several days to run before outcomes
can be observed, investigations are also
underway to optimise the use of available
computing resources via parallel and
distributed computing techniques.
A long-term aim is to harness computing
resources sufficient for running
simulation exercises in real-time,
allowing changes in conditions to be
introduced during the simulation and
the effects observed immediately.
Plans for further work include a number
of modelling refinements, such as the
ability to model the influence of injuries
and explosions as well as weather on
mood, and the behaviour of agents.
The effect agents can have on crowd
behaviour involves analysis in terms of three
groupings, designated ‘blue’ for those who
intervene to stabilise events, ‘red’ for those
who act as destabilisers, and ‘whites’ for
those who begin as neutral participants.
The researchers expect they could be
ready to undertake subsequent clientrelevant
work in about a year’s time.
Above: Dr Darryn Reid (rear) and Dr Vladimir Ivancevic with crowd
behaviour modelling software.
Above left: Frames taken from a DSTO crowd behaviour modelling animation.
5

A better analytical tool for
‘hit or miss’ situations
DSTO Fellowship Program
research has delivered
a more efficient way to
study complex system
operations, greatly
benefiting investigations
in areas such as guided
missile target tracking.
Systems analysts and engineers attempting to
predict the outcomes of complex systems with
highly variable inputs often use a statisticalbased
simulation known as Monte Carlo for
the purpose. This approach produces a set
of probabilities of certain events happening
for a particular set of input variable ranges
by running hundreds of simulations.
For complex systems, in which input variables
interact in linear mathematical ways, another
method of performance analysis is being
explored by DSTO’s Dr Domenic Bucco. Known
as adjoint simulation method, it provides a
quicker and more economic means of study.
“Adjoint theory has its origins in work done
several hundred years ago by mathematicians
to solve certain kinds of differential
equations,” explains Dr Bucco. “This has
since been developed into a means for
performance analysis of linear time varying
systems, referred to as LTVs in short.
“Given an LTV system with ‘n’ inputs and ‘m’
outputs, the adjoint method can generally be
used to determine the sensitivity of any of
the outputs at a fixed time to each of the ‘n’
inputs. The technique provides analysts with
a simple but powerful alternative to the Monte
Carlo method for systems where a linearised
form of modelling approach is acceptable.”
The method has been successfully applied
to the study of guided missile homing loops
as well as to the preliminary and conceptual
definition stages of many new missile programs.
Dr Domenic Bucco explaining the adjoint method modelling approach to a colleague.
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Block diagram depictions for research
Applying the method involves representing an
LTV system in block diagram form depicting
all the effects in sequence with any feedback
paths that impact on system outcomes.
The elements of the block diagram are then
manipulated by a set of mathematical rules
to arrive at a second block diagram, this
one now being in adjoint system format.
If the LTV system is simple, the conversion
process can be readily undertaken manually
by the analyst in ‘pen and paper’ manner.
However, for very complex systems with
many feedback paths, application of the
adjoint rules can be extremely tedious,
time consuming and error prone.
Automation
Dr Bucco therefore saw the desirability
of automating the adjoint system
construction process. The approach he
devised was predicated on the use of two
commercially available software packages.
One of these is known as MATLAB,
a computing environment and
programming language widely
used by industry and academia in
engineering, science and economics.
The other is called Simulink, which
provides a means to graphically design,
simulate, implement and test timevarying
systems, such as communications,
missile guidance, signal processing,
and video and image processing.
These were harnessed for adjoint system
operations by Dr Bucco with a suite of software
tools called COVAD that he developed.
Easy-to-use system
Via graphical user interface, the COVAD tools
facilitate the creation of a simulation block
diagram, which can then be automatically
converted into adjoint block diagram form at
the touch of a button.
Following this, a simulation of the system’s
performance is run, and the results can be
displayed in graph form. In guided missile
studies, for example, these plots may be
rendered as miss distance versus flight time.
Superior to Monte Carlo
The upshot of Dr Bucco’s work is
that his approach produces results
from a single simulation run that
are of comparable accuracy to
those obtainable with the Monte
Carlo method requiring several
hundred runs, thus delivering
findings much more quickly.
The adjoint simulation method also
provides data from its single run
about error effects for each input in
the system. A plot of these, known
as an ‘error budget’, can then be used to
show which input sources pose the greatest
problem for successful system performance.
Further developments of the work will
focus on enhancing the COVAD analysis
capability to more realistic missile
guidance systems such as those that
contain on-board digital processors.
Dr Bucco’s work was assisted with funding
from the DSTO Fellowship Program, which
was set up in 2006 to encourage scientific
innovation and creativity within the
organisation. Six researchers have now
benefited from this form of assistance.
Top left: Screen capture of adjoint method modelling software developed by Dr Bucco.
Above: Dr Bucco with graph comparing the predictive performance
of adjoint method modelling with that of the Monte Carlo approach.
7

Sound way of detecting
hidden aircraft flaws
Australia and its defence partners are developing a means to find defects in aircraft
parts and structures by the use of a technique called sonic thermography.
The work was carried out as a project
mounted by The Technical Cooperation
Program (TTCP) involving the United States,
Canada, Great Britain, New Zealand
and Australia.
The issue at large here is the need to keep
today’s military aircraft flying long past the
end of their design lives because of their
very high replacement cost. Maintenance
inspections to detect parts that are defective
due to effects such as corrosion, cracking
and delamination have therefore become
increasingly vital, and much research effort
is being put into finding ways that reduce the
expense and aircraft downtime required.
“One particular problem for inspection work
is posed by small fatigue cracks that arise in
many aircraft structures and tend to remain
closed under normal conditions, making them
very difficult to detect,” says DSTO researcher
Dr Kelly Tsoi.
“Early detection is essential in the case of
parts that are critical to the safety of flight.”
Several non-destructive inspection techniques
are currently in use, involving such means as
liquid penetrants, magnetic particles, eddy
currents, x-radiography and ultrasonics, but
these are seen to be less than optimal for
detecting certain types of flaws.
Enter sonic thermography
In 2002, the TTCP consortium began a study
on the potential of sonic thermography,
another non-destructive inspection
technique, with the hope of partly filling this
performance gap.
Use of the technology involves the
exposure of a test specimen to high frequency
sound energy, which induces frictional
heating at the surfaces of defects that are in
close contact. This heating is then detected by
an infrared camera.
One advantage it offers is the speed and
ease of inspections involving large areas and
Above: DSTO researcher with sonic thermography apparatus.
complex shapes. It is also environmentally
benign, not requiring the use of x-rays,
hazardous petrochemical liquids for
immersing or dousing of parts being tested.
Furthermore, it can usually be performed
on a structure directly, without the need
for disassembly or removal of parts to a
laboratory or hangar.
An early concern held about its use, however,
was whether the mechanically irreversible
and somewhat violent processes involved in
crack detection would in fact contribute to
further crack growth.
Dr Tsoi explains, “We found ourselves facing
a rather fundamental question – was the
technique in fact nondestructive?
“As a potential ‘show-stopping’ issue, it
needed to be settled as soon as possible. We
at DSTO undertook to investigate this in a
laboratory study, which fortunately confirmed
that there was no measurable ill effect caused
by the inspection process.”
Twelve steps towards a proven
technology
The TTCP research program involved a
series of twelve steps undertaken between
2002 and 2008.
The last of these was a ‘round robin’ study
to determine the effectiveness of sonic
thermography as an inspection tool, and to
compare the performance of the different
thermographic inspection systems developed
by the participating TTCP countries.
This involved testing carried out by all TTCP
systems on the same aircraft component; the
main wheel rim of a Lockheed Martin F-16
Fighting Falcon having accumulated a number
of service hours.
Cracking on such components is known to
occur at stem structures spaced equally
around the rim, which are formed as part of
the rim when cast from molten alloy.
For DSTO’s test procedure, a commercially
available hand-held 1200-watt ultrasonic
plastics welder was used as the sound
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DEFENCE SCIENCE AUSTRALIA
energy source. This was interfaced to an
infrared camera with DSTO-developed
software that ensured synchronous operation
of the two devices.
The DSTO software suite also featured a set
of powerful image processing algorithms
for extracting very small temperature
perturbations from the infrared signals
captured by the camera. Through this means,
temperature changes of well under one tenth
of a degree could be detected.
Testing of the wheel rim was undertaken both
in the state it was received, painted matt
white, and then again after being coated by
DSTO with a water-based high emissivity
paint, being done to improve the infrared
signal quality and eliminate background
thermal reflections.
Study outcomes
The DSTO investigation found that cracks had
developed at four of the five stem sites on
the rim. For three of these four instances of
cracking, the damage was not visible to the
naked eye, being hidden beneath the white
matt paint.
Of particular note in terms of outcomes, the
sonic thermography cracking signals reported
by DSTO were the largest obtained by any of
the labs involved in the ‘round robin’ study.
The position of the welder horn tip during
the testing process was found to have a
large influence on whether or not cracks
were observable. This was of particular
importance in the detection of smaller
cracks not visible to the naked eye.
Several areas on the main wheel rim were
investigated for placement of the sound
energy source. One of these positions, just
above the main bulk of a stem delivered
a virtually non-existent infrared signal. In
contrast, a position on the edge of a stem,
a relatively short distance away, produced
substantially improved results.
Pondering on the physical processes
involved here, Dr Tsoi observes, “An efficient
transfer of acoustic energy into the structure
is vital for generating a significant thermal
signature from the defect.
“While a wheel may seem to be
a simple object, it is, in fact, a complex
structure from a dynamics viewpoint,
comprising a collection of waveguides
that cause a complex flow of
acoustic energy.
“One of the key challenges for
implementation of this technology is
ensuring that the energy gets to where
it is needed, and crucial to that is the
location of the acoustic horn.
“While intuition and experience
are often good guides to optimal
energy source placement, our
long term objective is to develop
mathematical models to accurately
predict power flow.”
Continuing work
Further work undertaken by DSTO has
revealed that sonic thermography can
ably detect defects known as ‘kissing
bonds’ – defective adhesive bonding
between surfaces – as well as impact
damage in composite bonded repairs
(CBRs) and structures, cracking beneath
CBRs and also loose-interference fit
fasteners in metallic structures.
Although sonic thermography has been
shown to operate well in detecting flaws,
the researchers find themselves facing
fundamental difficulties when attempting
to achieve the necessary repeatability of
excitation in cases where defects need to be
characterised rather than merely detected –
as, for example, when determining the closure
forces acting on cracks.
The key problem in this regard is the fact
that the use of sound energy to excite a test
object produces chaotic responses, meaning
that it is very difficult to produce precisely the
same excitation in a test object in subsequent
test runs.
Ongoing research at DSTO is facilitating
progress in this area by providing more
insight into the way energy transfer is made
between the energy source and the test
object. The research has made possible the
identification of materials that can be used as
interfaces between the sound energy source
and the test object, which thereby allow for
efficient transfer of energy into the structure.
“These outcomes offer an encouraging basis
for improving the techniques being applied
here,” says Dr Tsoi.
The quality of the work being done by the
DSTO researchers and their international
collaborators was sufficiently impressive to
earn them the TTCP Achievement Award,
presented late last year.
Above left: The F-16 Fighting Falcon main wheel rim used in TTCP sonic thermography studies.
Above: Close-up of the F-16 wheel rim (left), with colour enhanced sonic thermography image
of same (right) that reveals otherwise invisible cracking on lower left-hand side.
9

Improved sonar pictures
of a noisy changeable ocean
Ocean forecast modelling is being applied by
DSTO to assist sonar target detection.
In anti-submarine warfare, the sonar
operator plays an integral part in monitoring
in-water active sonar returns to locate
potentially hostile targets and warn of
approaching attack from any given direction.
Conventional sonar operator consoles
typically comprise a screen with a plan
position indicator (PPI) display that depicts
the range and bearing of active sonar returns.
The work of interpreting what an active
return signal indicates is made difficult
and time-consuming due to the fact that
transmitted sonar energy propagates
in highly variable ways, being affected
by oceanographic properties such as
density, temperature and salinity that
vary from place to place and over time.
For the detection and identification
of faint return signals, this problem is
further exacerbated by the presence of
background noise produced by various
natural and human-made causes.
Correspondingly, sonar operators are
commonly faced with complex and changing
displays that require intense scrutiny and
skilled interpretation to distinguish potential
targets from environmental clutter.
To alleviate these difficulties, sonar
performance modelling is applied using
oceanic parameter inputs to produce output
predictions of how sound will travel through
water plus estimates of probability of signal
detection against submarines. This modelling
aids the process of both operating the sonar
system and interpreting active sonar returns.
Environmental data sources
Conventional sonar performance modelling
tools have been reliant on monthly-averaged
oceanographic data amassed in climatology
databases, along with in situ data gathered
via expendable bathythermographs
(XBTs) that provide a measure of ocean
temperature for a single place and time
from the sea-surface to a certain depth.
For some operational scenarios, however,
the sonar performance modelling outcomes
obtained with these data inputs do not
adequately capture the variability of
the changing ocean environment.
A recently instituted oceanic forecasting
service, called BLUElink, provides a
means of significantly improving on
this situation. BLUElink is an Australian
Government initiative involving the Bureau
of Meteorology, Navy and CSIRO.
The service produces three-dimensional
ocean models of the Australian maritime
region based on data from climatology
databases, satellite remote sensing
and measured at-sea data, featuring
parameters that include ocean currents,
wind stress, temperature and salinity.
The modelling results are available either
as forecasts for use in preparing for future
sonar operations, or hindcasts that can be
used for post-trial analysis, by estimating
what the state of the ocean was most likely
to have been at a particular time in the past.
Contained within BLUElink is a capability
called the Relocatable Ocean Atmosphere
Model (ROAM) for limited area high-resolution
modelling. This has sufficient resolution to
accurately depict smaller-scale shortlived
ocean circulation features, including frontal
boundaries and eddies, that dramatically
impact on sonar system performance through
the effects of refraction and energy scattering.
Seeing great potential in the BLUElink
resource, DSTO researchers Jarrad Exelby
and Han Vu have sought to harness
the higher fidelity modelled data on
offer for better quality predictions
of signal detection probability.
The work has been developed as an
experimental ‘concept demonstrator’,
aimed at proving the validity of the
approach to establish grounds for
applying further time and effort to
deliver a version for operational use.
A plethora of information
at fingertip reach
DSTO’s concept demonstrator currently
operates on a stand-alone laptop that
can be used during at-sea exercises or in
the laboratory for post-trial analysis.
The eventual intended use is to incorporate
both measured and modelled undersea
environmental information into the
real-time displays that sonar operators
view, presented as an overlay on the
conventional sonar display picture.
The demonstrator system has been designed
with functionality that enables a range
of different environmental data inputs
10
Left: BLUElink predictions for ocean temperature, height and surface currents for eastern Australia.
Above: DSTO researchers Jarrad Exelby and Han Vu.

DEFENCE SCIENCE AUSTRALIA
to be depicted as PPI display screens.
These include a two-dimensional map
of bathymetry (seafloor depth), seafloor
sediment type, speed of sound at the
water surface, surface water temperature,
wave height and wind speed.
Each variable is viewable one at a time,
depicted in shades of black and white.
The modelled probability of detection
performance for the sonar system,
meanwhile, is depicted in hues ranging
from red to blue. This clearly delineates
the two kinds of information and allows
for easy reference between them.
“Any areas of the display coloured red
indicate sonar propagation conditions
under which there is a very high probability
that active sonar emissions will detect a
submarine target, while those in blue indicate
a very low probability,” explains Exelby.
This probability of detection information is
also displayed in graph form as functions
of depth and range, with the options of
viewing this for just the upper 300 metres
of water, or the entire water body.
A further graph presents a prediction of
bottom and total reverberation levels over
the range of sonar detection distances.
The demonstrator overall enables active
sonar returns arising from features such
as canyon walls, seamounts or slopes to
be more readily identified and discounted,
while extra vigilance can be given to
just those parts of the display where
targets of interest may be found.
The system on trial
The performance of the DSTO system was
put to test using data gathered in 2003
off the coast of Western Australia in water
depths extending to around 5,000 metres.
This information was collected with an active
towed array system deployed to detect a
human-generated sonar signal that simulated
return emissions from a submarine target.
During the data gathering exercise, the range
between the towed array and the echorepeater
target was slowly increased over
time, with the position of the simulated target
being logged at constant time intervals.
Meanwhile, XBT measurements of
in situ temperature profiles were taken
at various times during the exercise
and BLUElink hindcasts of sea surface
temperature were obtained later.
Post-event analysis was then conducted
to compare target detection performance
using three different inputs for the
prediction of sound speed in water; single
point measurements obtained via XBT, the
same form of data provided by BLUElink
estimates, and spatially varying data similarly
provided by BLUElink. For all three cases,
wind speed, bathymetry and sediment
type inputs were the same or similar.
The point of comparing single-point data
obtained by the XBT and BLUElink was to
evaluate how well BLUElink predictions
compared against measured in situ data.
The findings overall were that the use
of BLUElink inputs of temporally and
spatially varying kind gave significantly
improved assistance for target detection
over the other two approaches.
Further studies were undertaken
involving at-sea data more recently
gathered by a hull-mounted active
sonar system, with these findings
corroborating those of the earlier study.
The researchers conclude that the ideal form
of support for sonar operators is likely to be
delivered by use of XBT measurements for the
immediate locality of their vessel along with
forecast inputs from BLUElink for the area.
“By incorporating timely and relevant
environmental data into sonar operator aids,
we see this will lead to increased operator
confidence, environmental awareness,
system performance understanding,
and ultimately, better anti-submarine
warfare capability,” says Exelby.
Top left: DSTO’s concept demonstrator PPI display showing
probability of detection data overlying bathymetry.
Top right: BLUElink predictions for the DSTO trials area off Western Australia in 2003.
Above: PPI readings based on single-point ocean measurements obtained with XBT (left)
and readings for the same trial point based on BLUElink inputs (right).
11

Robust and reliable radio
performance in any environment
Recent research by DSTO
to optimise the usability of
modern radio equipment
for Defence has achieved
noteworthy success.
Many new forms of radio communications
equipment feature a technology known
as multiple input multiple output
(MIMO), which uses multiple antennae
for transmission and reception.
MIMO was developed for digital radio
applications primarily to overcome
interference caused by multi-path radio
wave reflections from environmental
features and buildings. By harnessing
several signal paths, less power is required
for good quality transmissions than would
be possible otherwise. The key to MIMO’s
success here is that if the signal from one
path becomes too attenuated or distorted,
another can be called upon to fill the gap.
Through such means, MIMO also helps
maximise the efficient use of radio waveband
resources, an increasingly important issue as
the airwaves become ever more crowded.
Suitably adapted though MIMO may
be to the challenges of transmission in
urban settings, it does not perform well
in wide-open undulating to flat terrain
where radio path scattering occurs less
readily. This poses a particular problem
for Defence and emergency services
which often operate in such terrain as
well as more constrained settings.
DSTO researcher Dr Songsri Sirianunpiboon
has undertaken to develop MIMO designs
delivering robust and reliable performance
in environments of both kinds.
Polarisation for
performance
improvement
A key aspect
investigated by the
research program
is the phenomenon
of polarisation – a
property of twodimensional
transverse
waves, such as radio
waves, in which the
orientation of the
wave oscillation
is perpendicular
to the wave’s
direction of travel.
“By using an antenna that is dual-polarised
or by using multiple antennas with
different polarisations, the dimension
of polarisation is added to those of
time, frequency and space to expand
the diversity of available transmission
pathways,” explains Dr Sirianunpiboon.
“The use of polarisation as a source of
multipath diversity works particularly
well in wide open spaces where line-ofsight
conditions between transmitter
and receiver commonly occur, since the
polarity aspect of transmission is mostly
preserved under such conditions.”
Theoretical investigations were carried out
on systems using dual polarised transmit and
dual polarised receive antennae in terrain
ranging from one extreme to the other.
These revealed ways in which polarisation
can be exploited for better MIMO radio
operations. An important proviso, however,
is that the transmitter and receiver must be
fixed in aligned positions to each other.
In consideration of scenarios where the
transmitter or receiver might move out
of alignment, as would happen with the
mobile use of radio systems, studies were
conducted on the use of triad-shaped
antennae, showing these to be a viable way
of maintaining MIMO system performance.
Solutions for signal
processing problems
A further part of the work focused on
the signal processing part of the MIMO
radio system, involving an aspect
known as ‘space-time’ codes that
are crucial to message delivery.
With digitally-based radio communications,
the signal is encoded into discrete packets
of digital-form data for transmission, which
then have to be decoded and assembled in
real-time by the receiver for a transmitted
voice, image or data signal to be intelligible.
This is additionally complicated in the
case of MIMO reception by the need to
manage the assembly of data fragments
from several pathway sources and types.
While several types of space-time
encoding applications can be used for
polarised signal transmissions, they are
computationally very complex to decode.
Moreover, the one most suited to the
task is prone to cause computational
overload in line-of-sight conditions.
Decoding algorithms
Dr Sirianunpiboon has thus undertaken
to develop decoding algorithms able to
cope with quickly changing transmission
conditions, and which require only
modest amounts of computing power.
“The fast fixed-complexity decoding
algorithms we have developed are
based on a technique called conditional
optimisation, which is widely used in
statistical estimation and signal processing,
but has not previously been exploited in
decoding algorithms,” she explains.
Further developments planned for the work
are to test these techniques experimentally.
This research project was conducted
under the DSTO Fellowship Program.
Above: DSTO researcher Dr Songsri Sirianunpiboon.
12

DEFENCE SCIENCE AUSTRALIA
Briefs
Getting the sulphur
chemistry right for
Defence aviation fuels
Investigations are being carried out
by DSTO on sulphur compounds in
jet fuels in anticipation of tighter
Australian regulations on sulphur
emissions from jet engine exhaust.
Aircraft fuel, like any hydrocarbon-based
fuel, naturally contains small amounts of
sulphur compounds, which have various
effects – some beneficial, some not – on fuel
quality, performance and stability as well as
having certain environmental consequences.
While sulphur levels in Australia’s petrol and
diesel supplies have been reduced to meet
environmental goals, jet fuels have been
exempted to date. However, with tighter
regulations expected to come into force
eventually, various issues for jet aircraft
operations have emerged, one of which
is that engine wear and fuel degradation
occurs quicker with use of low-sulphur fuels.
DSTO researchers have been conducting
studies to see what kinds of sulphur
compounds are present in jet fuels, drawing
on work done in various parts of the
world to establish a range of compound
isolation and characterisation techniques.
The technologies applied for
characterisation include the use of gas
chromatography, together with either
mass spectroscopy or atomic emission
detection, that enable the structure of
molecules in question to be established.
The work overall will inform the use
of jet fuel in regard to how particular
sulphur compounds impact on corrosion,
fuel lubricity, storage and thermal
stability properties. The researchers
envisage the possibility that after the
advent of low-sulphur fuels, some
sulphur compounds could in fact be
added back at very low levels (or antioxidants
with no sulphur content) to
enhance certain performance aspects.
Thermal boost
for unmanned
aircraft
performance
DSTO researchers recently
participated in trials in
New Zealand to study
the abilities of autonomous flight-control
software for unmanned aircraft vehicles
(UAVs) to identify thermals and to guide
the craft into a circling path centred
on the updraft to ride the rising air.
The purpose of the work is to
enable UAVs to fly further and more
efficiently by taking advantage of these
naturally occurring air masses.
The trials were carried out at the Kaipara
Weapons Test Range in collaboration with
the New Zealand Defence Technology
Agency (DTA) using a 2.3-metre
wingspan Kahu UAV developed by
DTA for intelligence, surveillance and
reconnaissance (ISR) missions.
Strong coastal winds and the associated
problem of windblown sand made for
challenging flight conditions. Nevertheless,
the UAV successfully found and rode a
number of thermals, demonstrating the
potential of this technology to draw energy
from the environment for mission purposes.
The trial work was founded on earlier
studies conducted via computer-based
simulations that examined the flightcontrol
system’s ability to identify
and exploit thermal updrafts.
Future research will be undertaken to
validate the use of thermal soaring with
greater autonomous control and to study
how this innovation can be optimally used
during ISR missions. The team hopes
that Kahu’s current mission endurance
of two hours can be extended by up
to six times on daytime missions.
The research program was
conducted under the five-nation
Technical Cooperation Program.
DSTO and DTA researchers with Kahu UAV at the Kaipara
Weapons Test Range, NZ.
New weapons
fragmentation
recovery facility
A DSTO-developed apparatus for research
on air burst weapons has delivered a major
advance in study capabilities by improving
recovery rates of the fragments they produce.
The outcome of this new capability is better
characterisation of weapon lethality, which
serves to help Defence understand the
performance of weapons against potential
targets and also the vulnerability of assets.
The device consists of a large metal tank,
open at the top, with the weapon under
study placed on a stand in the centre so
that several metres of water surround it
on all sides. The weapon is contained in a
waterproof housing big enough to create
a surrounding air gap. The housing both
keeps the weapon dry to ensure proper
detonation and also allows fragments
to form normally as they would in air.
Upon detonation, the fragments thus
formed by the weapon pass through the
air gap and housing walls, then into the
water where they quickly give up their
energy and sink to the bottom of the
tank. These are subsequently collected
for analysis with size, mass and total
number of fragments recorded.
The process enables fragment recovery
rates of greater than 90%, markedly
improving on those attainable using
previous methods. The apparatus was
recently used during explosives trials
conducted at the Port Wakefield Proof
and Experimental Establishment.
13

Calendar
27 - 28 Feb 2011 AUVS Australia Conference
Inaugural conference hosted by AUVS Australia with delegates invited
from around the world for discussions on the theme ‘Future unmanned
capabilities for Australia – military and civil’, mounted in conjunction
with the Australian International Airshow.
Melbourne CBD
http://australia.auvsi.org/auvsi/australia/events/conference/
default.aspx
28 Feb - 3 Mar 2011 Health and Usage Monitoring Systems 2011
A DSTO-mounted international forum for review of developments in
health condition and usage monitoring. Presented as part of the Australian
International Aerospace Congress, held every two years in conjunction with
the Australian International Airshow.
Melbourne Convention Centre and Avalon Airport (3 March, 2011)
http://www.dsto.defence.gov.au/hums2011/
28 Feb - 3 Mar 2011 14th Australian Aeronautical Conference
Also part of the 14th Australian International Aerospace Congress.
Melbourne Convention Centre
http://www.aiac14.com/
28 Feb - 3 Mar 2011 3rd Asia-Pacific International Symposium on Aerospace Technology
Also part of the 14th Australian International Aerospace Congress.
Melbourne Convention Centre
http://www.aiac14.com/
1 - 6 Mar 2011 Australian International Airshow
The premier aviation, aerospace and defence event for the
Asia Pacific region.
Avalon Airport, Geelong, Victoria
http://www.airshow.net.au/avalon2011/conferences/index.html
14