1/9 What does "run aground" mean? -silly sodan
\_ When a ship or boat goes through water that is not deep enough,
the bottom of the boat, usually the keel, kits the "ground".
Typically the boat was moving forward at the time of impact
and a sudden loss of forward speed produces an uncomfortable
and a sudden loss of forward speed (lurch) produces an uncomfortable
sensation at the least, and damage at the most. Depends
if the bottom is sand or rocks. Big difference..
\_ Thanks. So does subs have sensors to detect these things?
\_ The run of the mill sonars you'll find on commercial fishboats
give a pretty decent image of the bottom of the ocean, and I'm
guessing that a nuclear sub would have something way way
better imaging in all directions, not just along the axis
of travel of the boat. Something or someone fucked up, and
I'm guessing the real story will not be reported in the news.
\_ How funny. I thought the same thing when I read the same news article.
\_ Active sonar maps fairly well. Subs are often trying to run
silent, and active sonar defeats that. They rely on charing
done by surface ships.
\_ In sufficiently deep waters there's a certain depth at
which sound speed stops decreasing with depth (because of
colder water) and starts increasing (because of increasing
pressure). If you put your sub on the bottom side of this
depth it impedes the ability of surface ships to detect you
because the change in sound speeds reflects some of your
sounds back down. If you have a ship running silent (with
their depth-on-keel gague off) and trying to keep under
this fixed depth, you could have a problem if the water is
not too deep and there's a charting error. So... what you
said.
\_ This is a lot of congecture based largely on Clancy novels
and watching Hunt for Red October, but I think the difference
between fishing boat sonar and nuclear sub sonar is that
fishing boats use active sonar and subs try to stay hidden
and use passive sonar. With passive sonar, you would rely
mostly on accurate sea floor maps for navigation. If mis-
calculate speed, heading, or time then you could be off course
enough to hit things you are trying to avoid in tight spaces.
I'm not sure they still use innertial navigation. It definitely
seems plausible. -saarp
\_ I believe they use high freq sonar for getting through
icy regions without giving themselves away. Perhaps
there's something similar they use for keel depth?
\_ How funny. I thought the same thing when I read the same news
article.
\_ what news is this? -- sodan who get all news from the motd
\_ I read it on the front page of cnn yesterday.
\_ Is it something about the South Asia earthquake reshaping seabeds
because it elevated seafloors and the tsunami moved around ships
that sank decades ago?
\- New motto of US submarine fleet: Run silent, Run agound.
How did a sailor get killed? ... flung into something by
sudden deacceleration? |
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