Evening star., 1963-05-15

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checkouts of the submarines
condition in water that no
where exceeded q thousand
feet in depth. For April 10,
the two ships would move out
into the deep water beyond
the continental shelf.
At 1922 pm. on April 9,
Thresher's matches were closed
for submergence, never to be
opened again. Her tests began,
and the events on the first
day proceeded uneventfully.
with all systems apparently
checking out well.
No Difficulty Expected
A low-pressure water tank
that had ruptured during dock
tests March 10 and had been
repaired gave no trouble. No
one was anticipating difficulty
in any case; for four solid
days before sailing Thresher
had undergone hydrostatic
tests at dockside. Every ele-
ment Of her plumbing that
would be subjected to pressure
at sea was tested to $50 per
cent Of maximum anticipated
conditions - to collapse
depth" pressure. Everything
had checked out properly.
The hull was not hydro
statically tested, Of course, but
that was no cause for concern.
1t was proved strong by 40
earlier dives to test depth, and
by partial-depth dives whose
combined stresses on the hull
added up to the equivalent Of
more than $50 test-depth ex-
cursionS.
Thresher's pressure hull had
been cut open during her stay
in Portsmouth, q normal pro-
cedure for removing and in
stalling bulky equipment. Also.
a new garbage injector had
been installed, a sort Of air
lock through which waste ma
terial can be dumped over
board. Both openings were
carefully inspected with radio
graphs, or X-rays, after being
welded shut again, and ac-
cepted as adequate by Harvey.
The Thresher skipper ap-
parently did not share the mis-
givings voiced by the father
of the nuclear Navy, Admiral
Rickover. OF industrial radi-
ography, the outspoken admiral
had commented last winter
that some inspectors "are no
better qualified to read radio
graphs than a layman is to in
terpret his own chest X-rays."
No Evidence Hull Was Weak
Today, after lengthy investi-
cation, there is no evidence
that Thresher's hull was the
weak point-indeed, the ship
yard plans officer termed this
''inconceivable." But the fact
that its integrity was preached
in the yard cannot be over
looked. Neither can the testi-
mony Of one officer aboard
Skylark that he heard q sound
like q ship breaking up-a
recollection which a tape re-
cording might have backed up
or retuted.
Through the shallow dive
maneuvers, Thresher's COM
plement had no cause for
alarm. Reports passed rou-
timely from the submarine to
her escort, with hearing con-
ditions varying as sea condi-
tions changed. Between two
submarines at depth, commu-
nication by underwater tele-
phone (called UQC or Ger
trude") is usually quite clear,
Of quality comparable with
big-city local phone service
over ranges of many miles,
Between q submarine and the
surface, however, communica-
ton is never quite that good,
and is sometimes quite poor.
What happens when Ger
trude quality fades is this:
sound waves, travelling
through water at a mile q
second Give times the speed
Of sound in air) strike a stra-
tum in the water where tenn
perature and density suddenly
change. AS sound waves pass
this "thermocline," they are
DETECTED and distorted, and
what Is received by the surface
ship is frequently garbled.
Oceanographers have long
beaten the thermocline, in
studies of fish noises. by tow
ing a hydrophone on a wire
long enough to go below this
; troublesome zone. Skylark, the
! submarines only communica-
tions link for this series OF
tests, had a phone mounted
on her hull, and an enlisted
man with q logbcok and pen
} nothing so advanced as a
: towed hydrophone backed up
; by tape recorder.