| In
1956 Admiral Arleigh Burke, then CNO, requested that the
Committee on Undersea Warfare of the National Academy of
Sciences to study the effect of advanced technology on
submarine warfare. The result of this study, dubbed
"Project Nobska" was an increased emphasis on
deeper-diving, ultraquiet designs utilizing long-range
sonar. The Permit class was based on Project
Nobska’s recommendations. Hull streamlining, reduction in
sail dimensions by approximately 50%, quieting of the
propulsion plant and an increase in test depth all led to a
dramatic advance in submarine operational capabilities and
stealth.
The
SSN-594 Permit class was the world's first modern, quiet,
deep-diving fast attack submarines, integrating such
advanced features as a hydrodynamically shaped hull, a large
bow mounted sonar array, advanced sound-silencing features,
and an integrated control/attack center with the proven S5W
reactor plant. These submarines were a major advance over
previous submarine designs, and established the pattern of
all successive American attack submarine classes, in several
extremely important respects:
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They
were the first submarines to have hulls constructed of
High Yield-80 (HY-80) steel alloy, which allowed
operations at substantially greater depths than
previous submarines. |
|
They
were the first submarines to have raft mountings for
turbines, motors and other equipment, resulting in
substantially quieter operations. |
|
They
were the first submarines to have a large bow-mounted
sonar requiring the installation of torpedo tubes
amidships, aft of the forward crew compartment. |
Although
they were larger than the previous SSN 585 Skipjack class,
and used the same nuclear power plant, their hull design did
not compromise their underwater speed. Designed for
prolonged periods submerged, they were limited only by the
amount of food that she can carry, and were capable of
sustained operation at high speed.
These
submarines were originally designated the THRESHER class,
but the USS Thresher (SSN 593) was lost 200 miles off the
coast of New England on 10 April 1963. According to
investigators, a seawater pipe in the aft engine spaces
broke, spraying water into the engine room and shorting one
of the main electrical bus boards. The sub lost electrical
power and couldn't operate the reactor. Darkness, a sea
mist, and sheer terror inhibited the crew from manually
actuating the valves. The aft part of the sub filled up with
water and tilted down. With no power to get back on line,
the sub drifted down to crush depth and imploded. A ghastly
death for an entire crew, and one the US Navy vowed never to
allow happen again.
The
ill-fated USS Thresher (SSN-593) and her crew did not suffer
in vain. Out of that terror and the lessons learned grew the
SubSafe Program. Through this program, every submarine in
the US Fleet, every pressure hull integrity-related system
aboard those subs, and every pressure-related part within
those systems must be certified as being 100% safe for use
on a submarine. The goals are to ensure that in case of a
casualty, the ship and its crew can be recovered and to
ensure that the integrity of the material used on the ship
can operate at design test depth. Directly related to the
Thresher tragedy, sea-connected joints can no longer be
brazed; they must now be welded. The SubSafe program brought
other controls, too. Now when an emergency arises aboard a
sub, all vital equipment which sailors would need quick
access to in the event of an emergency is clearly marked and
easily accessible. At all times an operator is one second
away from flipping the emergency main ballast tanks to vent,
so the sub can rise to the surface.
The
Navy took other steps to ensure such a tragedy never occur
again. Following the recommendations of a special
Presidential Deep Submergence Review Group, the Deep
Submergence Rescue System was developed in the mid-1960s.
The deep submergence rescue vehicles Mystic (DSRV 1) and
Avalon (DSRV 2) of the Deep Submergence Unit are the genesis
of that program.
The
last three units of this class [Flasher, Greenling,
Gato] were modified during construction to
incorporate lessons learned from the loss of the Thresher.
Fitted with heavier machinery and a larger sail, they were
ten feet longer than the other units of the class to correct
stability problems caused by weight growth.
The
SSN 605 Jack was fitted with an experimental
direct-drive propulsion system coupled with a pair of
counter-rotating propellers. The engine spaces were
lengthened by ten feet and the shaft was lengthened by seven
feet to accomodate this additional equipment. Although
counter-rotating propellers had previously produced
impressive gains in speed on the experimental Albacore, in
this instance the results were disappointing and led to the
abandoment of this approach in subsequent submarine design. |
