Evening star. [volume] (Washington, D.C.) 1854-1972, 1963-09-01
Sub Thresher
Seen Victim
0f'Downdraft'
Ala THE SUNDAY STAR
Washington. D. c.
September ], 1868
By WILLIAM HINES
Star Staff Writer

BY WILLIAM HINES
Star staff Writer
One of the worlds leading
oceanographers believes the
submarine Thresher may have
struck an unexpected down.
draft of water at a crucial
moment last April 10.
ThreSher, believed to be the
worlds fastest atomic sub
marine, was lost with 129 men
in 8,400 feet of water $50 miles
east of Cape Cod, Mass. Debris
from the submarine has been
found, but the hulk has never
been located.
Columbus OD. Iselin, ocean,
ographer of the Woods Hole
Mass Oceanographic Institu-
ton, explained his theory of
Thresher's death in an article
in the monthly magazine
Oceanus. He related the dis
aster to probable conditions
existing in the Thresher dive
area in early April.
The place where the sub was
lost is seward of sub-Surface
feature called Eastern Channel.
This is the principal outlet Of
the Gulf of Maine TO the deep
sea, and was likened by DR..
Iselin to IAN inverse Strait Of
Gibraltar"
Normal Flow Split
Under normal conditions, DR..
Iselin explained, water from the
ocean off Nova Scotia flows
southwestward into the Gulf OF
Maine, which is the shallow
area of water between Cape
Cod and Cape Cod Sable, Nova
Scotia. Normally this SOUTH
westward flow is split by a
shoal called Browns Bank
south of the tip of Nova Scotia,
part of the water entering the
Gulf of Maine north OF the
bank. and part south.
The normal outflow from the
gulf to deep water is restricted
to the Eastern Channel by the
presence of Browns Bank 10
the north and Georges Bank
to the south. Georges Bank is
a famous fishing ground where
the water is only a few hun
bred feet deep.
The situation described thus
far is the normal one, but con-
ditionS were not normal in
early April, DR.. Iselin pointed
out. There had been storm &C
tivity that had bottled up a
great amount Of water in the
Gulf of Maine. BY April 10, the
excess water in the gulf was
beginning to pour out through
Eastern Channel.
So great was the outward
flow, DR.. Iselin theorized, that
the normal inflow south OF
Browns Bank was denied into
the Gulf of Maine and was &C
tually pushed out into coun-
terclockwise eddy right in the
Thresher diving area.
DOwndraft Theory
This set up a condition Of
hiking" between waters OF
different densities, which Gre
ated a downdraft situation not
unlike the misnamed air
pocket" phenomenon of clear
air turbulence encountered by
airplanes.
Normally this would not be
fatal and there would be time
to blow some ballast so as to
tighten the submarine" DR..
Iselin said in his article. But
again things were not normal.
Here a second factor may
well have come into play" the
oceanographer continued. 1.-THE
same storm that disrupted the
normal flow through the East
ern Channel was now off the
entrance to the Gulf of st.
Lawrence (far to the north
east and sending out internal
waves in all directions"
These waves are something
like surface waves familiar to
all seashore vacationers but are
actually travelling beneath the
surface. Dr.. Iselin theorized
that such waves, "as they ap-
proach a funnel like feature
such as the Eastern Channel"
might be up to 300 feet high
from crest to trough with a.
period of as little as eight min
utes from crest to crest.
Wave Time Cut
If Thresher was unknowinglyI
heading into such a wave at a
slow cruise speed of 5 or 6
knots, DR.. Iselin said, the effect
would be to cut the wave pc
Rod in half. Apparently this
would cause the submarine to-
drop as much as 300 feet from
its desired depth in no more
than about two minutes. Com
bined with the other downdraft
situation, this would cause an
alarming increase in depth, DR..
Iselin said.
1.-THE diving officer could
have had his hands full" the
oceanographer noted. AT this
critical point. mechanical or
electrical failure became the
critical factor in regaining the
depth control, and the subma-
rine continued to sink until
collapse depth was reached"