174…
The Last Resource
descend to 15,000 feet is essentially an aluminium submarine and
few other submersibles can operate as far down as 6,000 feet. Much
of their equipment, including batteries, is placed outside the main
pressure chamber in a free—ooding ‘super—structure’. This metal
01 breglass shell may be strengthened and be given additional
buoyancy by a packing of syntatic foam——a composite material
consisting of glass ‘micro—balloons’ bonded together with epoxy resin.
An early submersible which ts neatly into this description is the
Alvin, built in the United States by the Applied Sciences Division
of Litton Industries in 1965. Alvin, with a depth range of 6,000
feet, was designed specically for oceanographic research—in fact
the submersible is named after oceanographer Allyn Vine, who was
deeply involved in its development. Weighing 26,000 pounds,
Alvin is 22 feet long with an 8—foot beam. It has a top speed of
4 knots, a cruising speed of 2 knots and a range when submerged
of 15 to 20 miles. The 7—foot—diameter pressure sphere is made of
high—strength steel (HY—100), 1—33 inches thick. Inside there is
room for a pilot and one or two observers, together with instru—
ments and life support equipment sufcient for twenty—four hours
or more. Four viewing ports enable the pilot and observer to see
ahead of and beneath the vehicle. A mechanical arm can be used to
take samples from the sea bed, although naturally the equipment
which the submersible carries varies from dive to dive, according
to its mission.
To compensate for dierences in weight of personnel and instru—
ments, as well as for changes in the density of sea—water, Alvin has
a
variable ballast system in the free—ooding outer casing. The
system consists of aluminium spheres lled with oil and connected
to collapsible rubber bags. When oil is pumped from the spheres
into the rubber bags, the amount of sea—water displaced by the
vehicle is increased (thus increasing the buoyancy), while the
weight of the vehicle remains the same. The overall eû”ect is to
make the vessel ‘lighter’. And obviously pumping oil from the bags
into the pressure spheres has the reverse effect. In this way the
density of the submersible can be adjusted to make it neutrally
buoyant—neither sinking nor rising. Major components such as
batteries and the motors which drive the craft’s three propellers,
one on each side and one at the stem—are all mounted outside the
pressure vessel. Because they displace water, they do not ‘weight’
as much as in air and they are completely compensated for by a
The Last Resource
descend to 15,000 feet is essentially an aluminium submarine and
few other submersibles can operate as far down as 6,000 feet. Much
of their equipment, including batteries, is placed outside the main
pressure chamber in a free—ooding ‘super—structure’. This metal
01 breglass shell may be strengthened and be given additional
buoyancy by a packing of syntatic foam——a composite material
consisting of glass ‘micro—balloons’ bonded together with epoxy resin.
An early submersible which ts neatly into this description is the
Alvin, built in the United States by the Applied Sciences Division
of Litton Industries in 1965. Alvin, with a depth range of 6,000
feet, was designed specically for oceanographic research—in fact
the submersible is named after oceanographer Allyn Vine, who was
deeply involved in its development. Weighing 26,000 pounds,
Alvin is 22 feet long with an 8—foot beam. It has a top speed of
4 knots, a cruising speed of 2 knots and a range when submerged
of 15 to 20 miles. The 7—foot—diameter pressure sphere is made of
high—strength steel (HY—100), 1—33 inches thick. Inside there is
room for a pilot and one or two observers, together with instru—
ments and life support equipment sufcient for twenty—four hours
or more. Four viewing ports enable the pilot and observer to see
ahead of and beneath the vehicle. A mechanical arm can be used to
take samples from the sea bed, although naturally the equipment
which the submersible carries varies from dive to dive, according
to its mission.
To compensate for dierences in weight of personnel and instru—
ments, as well as for changes in the density of sea—water, Alvin has
a
variable ballast system in the free—ooding outer casing. The
system consists of aluminium spheres lled with oil and connected
to collapsible rubber bags. When oil is pumped from the spheres
into the rubber bags, the amount of sea—water displaced by the
vehicle is increased (thus increasing the buoyancy), while the
weight of the vehicle remains the same. The overall eû”ect is to
make the vessel ‘lighter’. And obviously pumping oil from the bags
into the pressure spheres has the reverse effect. In this way the
density of the submersible can be adjusted to make it neutrally
buoyant—neither sinking nor rising. Major components such as
batteries and the motors which drive the craft’s three propellers,
one on each side and one at the stem—are all mounted outside the
pressure vessel. Because they displace water, they do not ‘weight’
as much as in air and they are completely compensated for by a