Escape through Time
In the 1950s, use of inflatable life rafts became widespread in the maritime
community, when large ships began to carry them as spare survival crafts. These
early inflatable rafts could automatically float free of a sinking ship,
inflate and be ready for use if lifeboats could not be used. By 1960, life
rafts became mandatory for passenger and cargo ships.
In 1974, the International Convention on Safety of Life at Sea, or SOLAS,
required cargo ships to have enough life rafts to accommodate half of the
people permitted on board the ship. These were float-free life rafts intended
to be used in the event that lifeboats were unavailable. Drafters of the 1983
SOLAS treaty, agreeing that not providing life rafts for the remaining 50
percent of crew members could lead to a Titanic-style disaster, mandated enough
rafts for all on board.
Inflatable life rafts have also increased safety on smaller ships, which have
limited space. Most modern units have carbon dioxide cylinders that automatically
inflate the raft. Due to the increased reliability of these rafts, the 1983
SOLAS treaty allowed cargo ships shorter than 280 feet in length and passenger
ships carrying fewer than 200 passengers the option of carrying only life rafts
(no lifeboats), as long as they were in sufficient numbers to accommodate
everyone on board. Since these life rafts have no means of propulsion, these
ships must carry at least one rescue boat, which facilitates
man-overboard rescues, assists other ships in distress, and tows life rafts
away from danger.
As for lifeboats, several totally enclosed lifeboats—better known as TEMPSC's, for
Totally Enclosed Motor Propulsed Survival Craft—were designed and built as early as
the first decade of this century. The conventionally hulled,
self-righting "Lundin housed lifeboat" was built, for instance, in 1914.
Another designed by Ole Brude, a pioneer in the field, looked something like a
torpedo and, instead of being lowered by wires, slid off the low side of the
ship on rails. In spite of the obvious advantages of the totally enclosed
lifeboat, these heavy, expensive steel boats never caught on.
From its start as a spare survival craft on ocean-faring ships, modern self-inflating life rafts have become much more prevalent in sea safety. In some cases they have even been used to replace the traditional lifeboat.
It was only in the 1960s, when transportation and seafloor drilling of oil grew
dramatically, that TEMPSC's became a necessity. A number of countries began
working on versions that would be able to travel for five or ten minutes
through fire on water. Eventually, designers determined that TEMPSC's should be
made of fiberglass-reinforced plastic and equipped with an exterior water spray
system and an interior air supply system for the engine and occupants.
To battle the hypothermic effects of cold climate sea emergencies as well as to solve the dilemma of deep sea oil rig evacuations, the Totally Enclosed Motor Propulsed Survival Craft was developed to provide shelter for its passengers.
Following two serious sea disasters in 1973, the design of lifeboat launching
systems underwent closer scrutiny. The result was the free-fall lifeboat.
Relying on TEMPSC technology, Joost Verhoef developed an inclined launching
system which, using the natural force of gravity, would allow a totally enclosed
lifeboat to simply slide down a ramp and plunge into the water below. Today,
free-fall TEMPSC's have been tested at heights of up to nearly 100 feet.
They are found on many tankers and most mobile offshore drilling rigs.
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Early life jackets, fashioned in the Victorian era, were made of cork. Worn
by lifeboat crews during rescues, they were effective at keeping men afloat.
However, they had a major failing. Since buoyancy was equally distributed
around the body, if a person became unconscious and lay facedown in the water,
he would remain in that position and would drown. Further, the lack of neck
support would result in a person who was losing consciousness to drop his or
her head forward, again usually resulting in drowning.
A demonstration of the Victorian cork vest. Despite its buoyancy, the life vest would fail to keep the head of the passenger, if unconscious and face down, above water.
Life jackets came into their own after the heroic tests of Dr. Edgar Pask. In
order to determine how an unconscious person floated, Pask allowed himself to
be anaesthetized and immersed in water wearing only a standard life jacket and
a breathing tube. Pask's daring experiments revealed that the best position for
the body to be in when bobbing in the ocean is leaning back with the head at a
45-degree angle to the sea surface.
Modern life jackets are designed with this in mind. A splint braces the neck,
and all of the buoyancy lies in the front of the body. In addition, a splash
guard is fitted to the front of the life jacket. If a person can pull it out
before losing consciousness, the splash guard will block any incoming splashing
water from blocking the airways.
The modern life vest incorporates an inflated collar, which props the wearer's head above water, and a splashguard, which prevents water from entering the airways of an unconscious wearer.
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Lifeboats and life rafts keep people out of the water until they can be
rescued, but how do rescuers know where to find them or even know that there
has been a casualty? In the past, many ships carried portable lifeboat radios,
but they could weigh 40 pounds or more and be difficult to operate.
In 1975, the United States began requiring its large oceangoing merchant ships
to carry emergency position-indicating radio beacons (EPIRBs). These devices
are designed to float free of a sinking ship and automatically send a distress
signal on aircraft distress frequencies. Depending on its altitude, an
overflying aircraft can pick up the signal and either alert rescue forces or
enable them to home in on the beacon.
A modern innovation to replace the often clumsy and confusing lifeboat radio, Emergency Position-Indicating Radio Beacons (EPIRBs) allow life rafts and lifeboats to emit a radio signal, which can be picked up by aircraft and satellites in order to pinpoint their position.
The 1983 SOLAS treaty contained a new EPIRB requirement for two EPIRBs
on either side of a ship. These EPIRBS are intended to be carried to one of the
lifeboats or life rafts on that side of the ship, where they will provide a
signal for rescuers to home in on.
In 1988, SOLAS amended its regulations to include satellite EPIRBs within its
search-and-rescue procedures. Satellite EPIRBs send a signal that is received
by U.S. and Russian weather satellites, and relayed to ground stations.
As the satellite passes overhead, the digital data and frequency change
of the distress signal are used to identify and pinpoint the vessel in distress.
Morse code, which has long been used for distress communications at sea,
has now been phased out.
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Water transfers heat from the human body 25 times faster than air of the same
temperature. In cold water, heat is removed faster than the body can replace
it. The result is that the victim eventually becomes helpless and either drowns
or succumbs to the effects of hypothermia itself. To prolong survival time in
cold water, it is necessary to keep water from coming into contact with the
skin and to provide insulation between the water and the skin.
To prevent individual survivors from getting hypothermia, buoyant immersion suits were invented as an improvement to standard life vests in icy waters. Above is a demonstration of the immersion suit in action.
Attempts to provide protection against hypothermia are not new. The use of
rubber suits dates back to the early part of the century. Although these suits
are credited with having saved lives, they were heavy, they generally required
a life jacket to be worn underneath, and they tended to leak and fill with
water. The danger they posed in terms of lost thermal protective value and
added weight for victims trying to climb out of the water spurred the
development, during WWII, of lighter-weight suits made of synthetic rubber.
It took modern materials to make today's "exposure suit" a practical reality.
The material that made the difference was neoprene foam sheeting. This
material, which first came into use for divers' wet suits, is a closed-cell
foam made up of individual air cells, so it floats and also provides excellent
thermal insulation. With a nylon fabric bonded to each side to protect the
foam, this material is ideal.
The modern immersion suit incorporates the use of neoprene fabric to allow the wearer to sustain body heat and flotation.
Since 1983, small cargo ships that carry inflatable life rafts as their only
survival craft and require survivors to jump from the deck to the rafts have
stocked immersion suits for everyone on board. Larger ships with conventional
open lifeboats have had to carry only three immersion suits for each lifeboat.
These are for the crew operating the lifeboat; passengers in the boat have
"thermal protective aids," a type of orange, aluminized suit.
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(1) Zodiac International; (2) Norsafe AS; (3,4) NOVA/WGBH Educational Foundation;
(5) Prosat Technologies; (6,7) Imperial International, Inc.
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© | Updated November 2000