Underwater Technology Vol 28 No 1
Winter 2008
A
Personal View
The role of subsea in the UK
B Jones
Technical
Papers
Moisture levels in compressed breathing air
TG Anthony and PR Clarke
Abstract:
The purity and quality of compressed breathing gases
are specified to cover both their physiological and engineering safety aspects.
The permissible water content specified in British Standards Institution BS EN
12021 (BSI, 1999) for compressed air at pressures less than 40 bar are
confusing. This paper proposes guidance for the diving industry on maximum
permissible water content for compressed air at pressures less than 40 bar. The
relationship, based on the Magnus equation, of the pressure within a compressed
air system, the ambient temperature, the water content (i.e. volumetric
humidity) and the pressure dew point (i.e. temperature at which liquid water or
ice will form) was used to identify operational guidelines. Two tabular format
operational guidelines, one simple and the other flexible, have been developed
for the water content of compressed air at pressures less than 40 bar. The
'simple' tabular system has been proposed as the preferred system.
Technical
Papers
Antenna design for the propagation of EM waves in
seawater
CK Yip, A Goudevenos and J Lucas
Abstract:
A new design for a transmitting antenna suitable for
generating subsea EM waves for the frequency range 1–100MHz is given in this
paper. It operates by electrically exciting water molecules to emit dipole
radiation. The new design of antenna uses a parallel wire transmission line
immersed in pure water contained within a PVC barrel, in order to efficiently
generate the dipole oscillations. This mode of dipole radiation generation has
an optimum signal output when the dipole dielectric conductivity is compared
with the water conductivity. When using distilled water having a conductivity of
2x10-4S/m, this occurs for frequencies above 20MHz.which is suitable
for subsea video signal propagation at 25 frames per second. The barrel antenna
produces up to a 40dB increase in emitted signal when compared with a coated
double-loop antenna placed directly in the seawater. However, a conventional
coated, double-loop antenna in seawater is suitable to be the receiving antenna.
The reason is because the double-loop antenna, w2hen operating as a transmitter,
has to initially generate on electric field within the seawater., which then
excites the water molecules. The receiver can directly pick up the propagated EM
wave. A less efficient design of the new antenna, which is however more compact,
has been achieved by placing the parallel-wire transmission-line dipole
transmitter within a water-filled cylindrical PVC tube. For short-distance
propagation or diver-to-diver communications, this more compact structure is the
preferred design.
Technical
Papers
The feasibility of remotely sensing marine sediments
using a parametric array
PA Lepper and B Woodward
Abstract:
The design, development and testing of a parametric
sonar system was carried out during two multidisciplinary international projects
to investigate the feasibility of remote sensing of marine sediments using
acoustics. Developments included improved drive signal generation for phase
steering the sonar beam, and the implementation of a dynamic stabilisation
technique to compensate in real time for wave-induced motion of a tow-fish
deployed behind the tow-fish deployed behind a survey ship. This ensured that
the transmitted acoustic signals could be detached by a streamer array behind
the tow-fish. Sea trials demonstrated the potential for the use of a parametric
source to sense, and eventually to characterise, marine sediment geophysical
properties.
Technical
Briefing
SotonAUV: the design and development of a small,
manoeuvrable autonomous underwater vehicle
J Aktman, M Furlong, A Palmer, A Phillips, SM Sharkh
and SR Turnock
Abstract:
The University of Southampton's entry into the
Student Autonomous Underwater Challenge – Europe (SAUC-E) 2007 was a sutom
designed and built autonomous underwater vehicle (AUV) named 'SotonAUV'.
Originally developed for SAUC-E 2006, the vehicle was significantly upgraded for
the 2007 competition. The mechanical design of the vehicle is described, and an
overview of the autonomy and control approaches employed is provided. The
updated vehicle successfully competed in SAUC-E 2007, winning first place in the
overall competition and taking the BAE Systems prize for innovation in autonomy.
Book
Reviews
Archaeological Oceanography by Robert D
Ballard
Reviewed by G Momber
Underwater Technology Vol 28 No 2
Spring 2009
A
Personal View
Ocean geo-engineering: science in the spotlight
E Hill
Technical
Papers
The use of towed camera platforms in deep-water
science
DOB Jones, BJ Bett, RB Wynn and DG Masson
Abstract:
Towed camera platforms have been important in the
study of the deep sea for over 30 years. The use of towed camera platforms in
deep-water science is reviewed, drawing from the experiences of the National
Oceanography Centre, Southampton's (NOCS) towed cameras, the wide-angle seabed
photography (WASP) vehicle and the seafloor high-resolution imaging platform
(SHRIMP). Practical considerations for towed camera platform use are outlined
with particular reference to sensors, flying altitude and comparison between
photographs and video. Although the technology for towed camera platforms will
change over time, the concept remains of great value in studying the remote
deep-sea environment.
Technical
Papers
The effects of high altitude on relative performance
of dive decompression computers
PL Buzzacott and A Ruehle
Abstract:
In this paper, dive computer generated no
decompression limits (NDLs) in fresh water at high altitude were compared with
low-altitude single, repetitive and multilevel dives. All computer-generated
high-altitude NDLs exceeded those published for the altitude dived. Computer
rankings by conservatism for single dives at low altitude had negative
correlation with rankings high altitude (r = –0.81). Correlation between
high-altitude square-profile dives and low-altitude repetitive, multilevel NDLs
was significantly higher (r = 0.91, p < 0.01). We conclude
sea-level single-dive NDLs, such as those published in instruction manuals, are
not reliable when gauging the conservatism of dive computers for use at high
altitude. It is recommended that divers using dive computers for planning
high-altitude dives to consider computer-generated real-time NDLs as
experimental.
Technical
Papers
Off-gassing of volatile hydrocarbons in hyperbaric
environments
V Flook
Abstract:
The paper summarises work, carried out on behalf of
diving and manufacturing companies, related to volatile hydrocarbon off-gassing
in saturation diving systems. In the hyperbaric environment, the problem of
off-gassing is compounded by the fact that the divers are exposed to the chamber
atmosphere 24 hours a day, 7 days a week, for several weeks, thus exposure
limits have to be set much lower than in industry in general. The diving systems
themselves are monitored regularly, but work has been carried out to evaluate
off-gassing form some of the products used in saturation diving. These include
the paints used in chambers, the umbilicals used to supply gas to the diver
under water, cleaning agents and new materials planned for use in the new dive
systems currently being built.
It is evident that some materials
do off-gas considerable levels of volatile hydrocarbons. Some substances, such
as paints, sealing compounds and cleaning agents, off-gas to an extent that
would be unacceptable even under normobaric conditions. The soft furnishing
materials that were tested off-gassed at acceptably low levels, however,
modifications were required to the manufacturing process of bell umbilicals in
order to get off-gassing down to an acceptable level.
Material Safety Data (MSD) sheets
are not required to take account of potential off-gassing; indeed, the vapour
phase from substances is virtually ignored in the listing of important
compounds. This mean s that MSD sheets cannot be used as a guide to safety of
the gas phase. New materials destined for diving systems should be tested for
off-gassing. It would seem prudent to continue to make routine checks on the
diving system during diving operations.
Technical
Paper
Estimation of high data rate underwater acoustic
communication channel capacity
Guoqing Zhou and Taebo Shim
Abstract:
Underwater acoustic channels (UACh) require robust
techniques to obtain high speed data transmission to reliable communication.
This paper presents the adaptive transmission technique, in conjunction with the
maximal ratio combining (MRC) diversity technique, to adapt UACh fluctuation
based on a statistical channel model. Simulation analysis shows that the data
rate can be optimised allowing transmitted power to vary with signal-to-noise
ratio (SNR), subject to average power constraint. It also shows that the data
rate can be increased under adaptive techniques in conjunction with two-branch
diversity. Under the optimum data rate, the Matlab simulink of the UACh
quaternary phase-shift keying (QPSK) communication system provides a benchmark
for experiment to be carried out in the actual environment.
Book
Reviews
The History of Oilfield Diving: An Industrial
Adventure by Christopher Swann
Reviewed by B Jones
Underwater Technology Vol 28 No 3
Summer 2009
A
Personal View
Subsea Technology – Where Next?
I Gallett
Technical
Papers
The Nereus hybrid underwater robotic vehicle
AD Bowen, DR Yoerger, C Taylor, R McCabe, J Howland,
D Gomez-Ibanez, JC Kinsey, M Heintz, G McDonald, D Peters, C Young, J Buescher,
B Fletcher, LL Whitcomb, SC Martin, SE Webster and
MV Jakubata
Abstract:
The Nereus vehicle will enable scientists to
explore remote regions of the oceans, such as under the polar ice caps and deep
trenches, up to depths of 10 972m (36 000ft). Technology limitations have
prevented routine, cost-effective access to these remote regions, and the final
4500m of the ocean remain largely unexplored. New solutions to deep diving are
described. The Nereus hybrid remotely operated vehicle (HROV) is designed
for exploration and research needs as a single system. It can operate as an
autonomous vehicle for seafloor surveys, or in a tethered/ROV mode to sample
rocks or deep-sea animals The HROV Nereus transforms between its two
modes of operation to accomplish all these tasks during a single cruise
deployment. Sea trials of Nereus took place off the Hawaiian Islands at
2500m in November 2007. An overview of the vehicle and results from its initial
trials are reported here.
Technical
Papers
Autosub6000: its first deepwater trails and science
missions
S McPhail, M Furlong, V Huvenne, J Perrett, M Pebody
and P Stevenson
Abstract:
In September 2007 on RRS Discovery, the
Autosub6000 autonomous underwater vehicle (AUV) completed its first deepwater
engineering trials and, fitted with a multibeam bathymetric mapping sonar,
carried out its first science missions less than a year later as part of a
geology and geophysics science cruise onboard the RRS James Cook. This
paper describes how the issues of energy storage, navigation and buoyancy
control were tackled that specifically affect a deep-diving AUV, capable of
operating with true autonomy independently of the mother ship.
Technical
Papers
A review of sublittoral monitoring methods in
temperate waters: a focus on scale
HB Van Rein, CJ Brown and R Quinn
Abstract:
A plethora of methods to monitor shallow sublittoral
benthic habitats and communities are available to the marine researcher today.
The most widely used methods are reviewed and evaluated, with reference to the
spatial scale at which they operate. For ease of comparison, methods are
categorised as operating over broad (>1km), meso (10m 1km) and fine scales
(<10m). A measure of efficiency and data resolution are provided by exploring
the range of sampling techniques and strategies at each of these spatial scales.
Recommendations are made regarding which methods are most effective at each
scale: light detection and ranging (LIDAR) and multibeam sonar over broad
scales; sidescan sonar, drop-down cameras, towed cameras and remotely operated
vehicles (ROVs) over meso scales; and grab samplers, sediment corers for soft,
unconsolidated sediments and photoquadrats, and video transects for hard,
consolidated sediments at fine scales. Emphasis is placed on the development of
standardised methodologies for sampling each scale within a nested design, for
the monitoring programmes of the future.
Technical
Paper
Underwater wet welding made simple: benefits of
Hammerhead®
wet-spot welding process
D Keats
Abstract:
A new method of wet welding was investigated to
evaluate potential improvements in weld quality, ease of use, increased welding
speed and the elimination of welding skill. The new welding process, which has
been called Hammerhead `wet-spot' welding, eliminates the need for skilled
welder-divers as well as traditional cleaning and preparation techniques
normally associated with conventional manual metal arc (MMA) wet welding. In
addition, the process also allows welding to be conducted in nil visibility, yet
remains a MMA process, using a specially designed Fe Cr Ni Mo electrode. The
process utilises a control device, which must be pre-set before the diver enters
the water. Through this device, weld parameters are controlled and quality is
maintained, thus the role of the diver is simplified to three steps: make
contact with the material, strike the arc and maintain pressure to the electrode
while welding. A series of spot welds were produced both wet and dry on 8.0mm
carbon steel plates. The welds were evaluated with regard to ease of use and
setting up of the device, speed and final weld quality. Initially, the
performance of the process was assessed and usage diagrams produced. Work
regarding an automated version of the system has also been proposed.
Meeting Note
Selected Summary Highlights from the 30th
Consultative Meeting (LC30) of Contracting Parties to the Convention on the
Prevention of Marine Pollution by Dumping of Wastes and Other Matter 1972
(London Convention 1972) and the 3rd Meeting of Contracting Parties to the 1996
London Protocol (LP3) to the London Convention (London Protocol), 27 31 October
2008 in London at the International Maritime Organization
P Verlaan
Book
Reviews
The Andaman Express by Lorne Gifford
Reviewed by I Gallett
Underwater Technology Vol 28
No 4
Unmanned Underwater Vehicle Showcase Special Issue
Autumn 2009
Guest
Editor's Note
UUVS Special issue on navigation, guidance and
control of unmanned underwater vehicle
R Sutton
Technical Papers
Towards supervisory-switched control
of hybrid underwater vehicles
AJ Sørensen and J Refsnes
Abstract:
The paper presents automatic control
system design considerations for underwater vehicles conducting a
diversity if intervention and inspection missions. Such multitasking
vehicles are here denoted as 'hybrid underwater vehicles'. Dependent
on the various operations, the vehicle particulars – such as mass,
breadth, length or centre of gravity – may change considerably due
to changing payloads, such as tool and instrumentation packages.
This can lead to both structural and parametric model variations
that will be time-varying, though partly known, depending on the
given mission. Both the modularity in the controller design and the
ability to switch between the appropriate banks of controllers
enable the design of automatic supervisory-switched control systems.
This paper also presents recent research work at the Norwegian
University of Science and Technology (NTNU) on nonlinear model-based
control of slender-body underwater vehicles. In particular, results
from a study using a Minesniper MKII will be discussed, describing
two of the model regimes as proposed for supervisory-switched
control concept.
Technical Papers
Fòlaga: a low cost AUV/glider for
coastal environmental sampling
A Caffaz, A Caiti, G Casalino, L Gualdesi and A
Turetta
Abstract:
The paper describes the current
evolution of the class of Fòlaga underwater vehicles, whose
actuation mechanism is hybrid between oceanographic gliders and
standard, self-propelled autonomous underwater vehicles (AUVs). The
Fòlaga vehicles have been designed for coastal oceanography and
environmental sampling: the application-oriented design approach has
resulted in light-weight, low-cost, low-maintenance vehicles. A
description of the vehicles' design and guidance, navigation and
control capabilities is given, together with data from recent
experimental trials.
Technical Papers
A flexible multi-mode of operation,
high resolution survey platform for surface and underwater
operations
D Toal, S Nolan, J Riordan and E
Omerdic
Abstract:
This paper describes the ROVLATIS,
a multi-mode of operation flexible platform for high-resolution
near-seabed survey from shallow inshore waters to depths beyond
1000m. The paper further describes the operation modes of the
vehicle. Special system features include: deployment flexibility for
both small inshore boats and larger research vessel; fault tolerant
controls; onboard computer control enabling real-time disturbance
reaction, autopilot functionality and autonomous underwater vehicle
(AUV) experimentation; and topside augmented reality operations
support, simulation for remotely operated vehicle (ROV) pilot and
sonar operator/hydrographer training. Vehicle and control
development using the University of Limerick (UL) virtual underwater
laboratory/simulation tools and hardware-in-the-loop testing is
described. The paper includes test results from the March 2009
offshore sea trials with the ROVLATIS.
Technical Paper
Underwater vehicle technology in the
European Research Project VENUS
G Conte, L Gambella, D Scaradozzi, S
Zanoli, A Caiti, V Calabrò, A Alcocer, J Alves, B Cardeira, R Cunha,
F Curado, P Oliveira, A Oliveira, A Pascoal, M Rufino, L Sebastião
and C Silvestre
Abstract:
This paper describes the work carried
out during the first part of the European research project Virtual
ExploratioN of Underwater Sites (VENUS) by two of the participating
teams. As the project is aimed at developing a set of best
practices, procedures and tools for exploring underwater
archaeological sites, part of the work concentrated on the use of
unmanned underwater vehicles for gathering optical and acoustic data
on field and their use in constructing photographic maps. At the
same time, the use of unmanned surface vehicles for long-range
exploration and construction of large-scale acoustic maps was
investigated.
Concentrating the
first point, the main results consist of a series of best practices and
procedures for collecting correlated and geo-referenced optic and acoustic
images, which are used for constructing online two-dimensional photographic maps
of the explored area during the survey, as well was offline three-dimensional
representation of the site in a virtual reality environment. The construction of
two-dimensional photographic maps represents a major innovation towards
conducting archaeological exploration and defines a new, efficient way of
governing it, at logical level, in a closed loop fashion. Integration of the
information into a geographic information system (GIS) has also been developed
to help archaeologist interpret the results of the ongoing exploration with
respect to larger scenarios, and possibly to modify or adjust the mission
parameters during its execution accordingly. The basic capability of surface
vehicles in connection with the objectives of the archaeological exploration has
been investigated as a basis for an integration between underwater and surface
vehicles in that activity.
Book Review
Masterclass in AUV Technology for
Polar Science edited by Gwyn Griffiths and Ken Collins
Reviewed by J Evans
