Re: IJN and sound velocity profile
- From: "Jack Linthicum" <jacklinthicum@xxxxxxxxxxxxx>
- Date: 29 Apr 2006 04:06:56 -0700
Christophe Chazot wrote:
"Jack Linthicum" <jacklinthicum@xxxxxxxxxxxxx> a écrit dans le message de
news: 1146236647.927647.292980@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Christophe Chazot wrote:
Hello, this is a serious question.
I'm looking for information about possible exploitation of sound velocity
profile (SVP) or bathythermography (BT) by the Japanese during WW2.
As far as I know, no IJN surface warship had any device to measure SVP or
BT, and convoy escorts simply ignored sound propagation conditions when
they
tried and establish a screen around a convoy, leading to irrelevant
position
of sonar-equiped ships. On the other hand, IJN submarines did exploit
temperature gradients to escape from detection, in 1944-45 at least but
maybe earlier. So what ? Did they never exchange their experiences, or
did
they but lacked time / means to inforce relevant tactics in surface
forces?
Has anyone some relevant info ?
Regards,
Christophe Chazot
The Japanese Submarine Force and World War II says the I-400s and
I-13/I-14 had anechoic coating, suggesting the idea was there.
You have clear photographs of this coating on pages 92 - 93 of "I-400,
Japan's secret aircraft-carrying strike submarines" and a short explanation,
but this coating gives no indication that the Japanese knew how SVP or BT
layers had an impact on sound propagation through water.
Later quote "The IJN had very little concern for the protection of
Japanese shipping lanes or ASW tactics and operations. There was no
Japanese navy policy for countering enemy ASW....their lack of fully
modern electronic sensors, slow submerged speed, shallow maximum test
depth and bad manuerverability...made them easy targets for astute ASW
forces"
In December 1942 or January 1943 (my sources are not very clear), the 12th
department of the Naval HQ issued a "doctrine related to the protection of
communication lanes of the great east Asia", which was the first "ASW
policy" of IJN. It was pretty irrelevant at this time but was improved
several times. In October 1944 it had become more consistent, recommending
close cooperation between aircraft and escorts and with search patterns for
MAD-equiped and radar-equiped planes, but rather strangely it does not
mention anything about sound velocity profiles or anything close that could
have helped omptimizing sonar operation or escorts positioning around
convoys. That's why I suspect they hardly had an idea of it. Other clues are
that I've never heard or read anything about a dedicated bathythermograph,
that none of the numerous requisitionned crafts acted as ocean survey ship,
and that US subs frequently noticed that IJN escorts seemed to have no idea
of the role of temperature layers, as far as they could judge from the
reactions of escorts.
But I do not understand how IJN sub captains (or, at least, some of them)
knew that they could hide under layers. Did they learn it from their German
counterparts ? and why didn't they inform the 12 dept.?
BTW, thanks for your answer and cooperation.
Regards,
Christophe Chazot
Redacted to remove excess, Japan seems to have been interested in
ultrasound for flaw detection but seems to have also dropped all
research for WWII. The basic idea seems to have been an outgrowth of
radar and used water as the transmission medium. You need lots of
researchers, each starting from one basic observation, to need to reach
out into other applications. The thermocline phenomena probably was
found empiraclly but some Japanese submarine commanders but the
"attack" doctrine of the Japanese submarine force may have precluded
sharing the knowledge officially.
"In the reflection technique, a pulsed sound wave is transmitted from
one side of the sample, reflected off the far side, and returned to a
receiver located at the starting point. Upon impinging on a flaw or
crack in the material, the signal is reflected and its traveling time
altered. The actual delay becomes a measure of the flaw's location; a
map of the material can be generated to illustrate the location and
geometry of the flaws. In the through-transmission method, the
transmitter and receiver are located on opposite sides of the material;
interruptions in the passage of sound waves are used to locate and
measure flaws. Usually a water medium is employed in which transmitter,
sample, and receiver are immersed.
The equipment suggested by Sokolov which could generate very short
pulses necessary to measure the brief propagation time of their
returning echoes was not available until the 1940s. Industrial use of
ultrasonic testing apparently started spontaneously at around similar
times in the United States and Great Britain. Such technology had also
been in place in Germany and Japan, but developments had been curtailed
because of the second world war.
<snip>
Research into ultrasonics and metal-flaw detection in Japan was
considerably curtailed when World war II broke out in 1941, at which
time the Americans and the Germans were both diligently researching
into ultrasonics and the development of the Radar. The study into Radar
techniques in Japan was also in the disadvantage. As the war ended in
1945, research into high-power electronics was prohibited in Japan for
some time (up till 1948, when developments of non-military electronics
resumed).
http://www.ob-ultrasound.net/ultrasonics_history.html
.
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