573
1 INTRODUCTION
Liferafts are the lifesaving appliances used on all
typesvessels.Theirmainadvantagesarelowweight,
low space demands and availability in cases of
sudden disasters. In these cases the life raft,
automatically launched from 45 m depth, by the
hydrostatic release system, is the only chance to
surviveforpeopleinthewater(GerigkM.,2004).
Forthedozensofyearsoperationalcharact
eristics
of liferafts did not change a lot. The main
improvementswere:introductionoflightermaterials,
insulated floor, insulated canopy for better thermal
protection of survivors and different designs of
boarding platforms for easier entry from the water
(AbramowiczGerigk&Burciu, 2012; Abramowicz
Gerigk&Burciu,2014).
Thegeneralobjectivesinliferaftdesignarest
illthe
economic issues‐low cost and wide availability of
service. Not very high operational demands are
related to the rules of the International Life Saving
ApplincesCode(LSA),ConventionforSafetyofLife
at Sea (SOLAS, 2008; IMO Resolut
ion MSC. 48(66),
1996)andEuropeanUnionstandards(EUDirectiveof
MarineEquipment96/98/EC,1996).Theresultsofthe
field tests give satisfying results as they are carried
outingoodweatherconditions.
ThesuccessofSARactionatseaisdependenton
time of search and rescue operations. The ti
me to
search,detectionandrescuethesurvivors shouldbe
shorterthantimetosurvive. Timeofsearchaction
T
Risthesumofthreecomponents(BurciuZ.,Grabski
Fr.,2011):
T
R
=T1+T2+T3 (1)
where:
T
1‐timetoreachthetheatre,
T
2time of the search in the determined area to the
momentofthesearchobjectdetection,
T
3‐timetogivetheeffectiveaid.
ThedetectionmethodsusedduringSARactionare
visualobservations,radarandthermalimaging.
The research conducted in real sea conditions,
have shown that the main difficulties in search and
detectionofliferaftsare related to theliferaftshape,
constructionmaterial,colourofthecanopy,colourof
the outside pa
rt of the floor and operational
characteristics.
The most important problems recognised in the
liferaftoperationareasfollows:
difficultentryintotheliferaftfromthewatereven
ifboardingplatformisavailable,
Innovative Liferaft
T.AbramowiczGerigk,Z.Burciu,J.Jachowski,E.Kornacka&W.Stefurak
GdyniaMaritimeUniversity,Poland
ABSTRACT:ThepaperpresentthelatestresultsofresearcgcarriedoutwithinR&Dprojectonnewsolutionsof
liferaftconstuction.CFDsimulationsofliferaftperformancearepresented.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 9
Number 4
December 2015
DOI:10.12716/1001.09.04.15
574
notsufficientprotectionfromhypothermia,dueto
thewaterinsidetheliferaft,
difficult or impossible detection by radar, due to
small radar reflective surface, which reduces the
probabilityofdetection,
insufficientstabilityinheavyweatherconditions.
2 LIFERAFTDETECTION
The improved liferaft detection can significantly
decreasetime
tosearch.TheinstrumentsusedbySAR
services can detect search objects using daylight
cameras, thermal imaging and radiolocation. The
improvement can be achieved by increasing the
liferaftsignaturesinallrangesofdetection:thevisible
(VIS and NIR), LIR (thermal IR) and radar. Use of
modern materials, structural elements
and
technologiesenablestoincreasethethermalsignature
andincreasereflectionoftheliferaftradarsignal.
2.1 Detectionusingthermovision
The temperature relative to the background is an
essential parameter in the search using the thermal
imaging. The improved detection of liferafts in
thermalimagingcanbeobtainedbytheuse
ofworm
materials on the whole surface of the canopy or
applicationofwormelementsonlystrengtheningthe
thermal signature. The example of the thermal
illuminationhistogram ofthematerialsampletested
fortheapplicationontheliferaftcanopyispresented
infigure1.
Points
Points
Figure1 Thermal illumination histogram of a canopy
material‐sampleno10after3minutesfor12V.
2.2 Radar detection
Thetraditionalliferaftsaremadeofrubberorcoated
fabric, which are very good dielectrics. This is the
reasonthey arealmostinvisible onthescreenofthe
navigationalradars.
Thereareseveraltypesofpassiveradarreflectors
used to increase the liferaft reflective characteristics.
Thereflectorsareunfoldedautomaticallyafter
thelife
raftislaunchedortheyshouldbemanuallyinstalled
ontopofthecanopy.Inheavyweatherconditionsthe
process of installation can be very difficult or even
impossible. The chance of the liferaft detection is
therefore dependent mainly on the applied or not
appliedradarreflector,proper
radarinstallationand
itseffectivereflectionarea(Technicalreport,2014).
The effectiveness of radar reflectors used on
liferaftsislimitedduetotheirlowpositionabovethe
water surface about 1.5 m, note less than m (LSA,
2013) The detection also depends on disturbances
causedbywaves.
Theliferaftechoand
disturbancesfromwavescan
make the liferaft invisible in the navigational radar
display(fig.2).
Figure2. Radar echo of a liferaft and disturbances from
waves presented in the navigational radar display
(Technicalreport,2014,SzklarskiA.)
The maximum range of the radar detection very
seldomexceedsthedistanceof0.5‐0.6Nm(Nautical
mile). At the sea state 8 the intensive disturbances
fromthewavesmaketheliferaftinvisible.
Theincreaseofradardetectionprobabilitycanbe
obtainedintwoways:
using the improved radar reflector
mounted
directlyontheliferaftcanopyoronasmallmast,
preferablypneumatic,
addingthereflectiveoutershellonthecanopyor
makingthewholecanopyofthereflectivefabric.
The radar signatures for different reflective
materials in dependence on the distance from the
liferaftarepresentedinfigure
3.
distance [m]
amplitude [V]
Radar signatures
Figure3. Diagram of radar signatures (Technical report,
2014)
The 2D and 3D images of radar reflectivity of a
reflective material sample are presented in figures 4
and5.