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Mailing List Logs for ShadowRN

Message no. 1
From: olafur gunnarsson <olafurg@******.IS>
Subject: Re: Submarines
Date: Tue, 15 Oct 1996 00:49:25 GMT
Has anyone got any info he´d like to share about Submarines in 2057
how big are they what are they being used for who´s got them and why
and most important any stats. Ive only seen one sub For shadowrun on the =
WWW
and i was wondering if anyone had anymore.
Olafur G
Message no. 2
From: Pete Sims <petesims@********.DEMON.CO.UK>
Subject: Re: Submarines
Date: Thu, 17 Oct 1996 17:04:55 +0100
In article <199610150049.AAA00148@*****.mmedia.is>, olafur gunnarsson
<olafurg@******.IS> writes
>Has anyone got any info he´d like to share about Submarines in 2057
[snipped]

Hope all that junk was useful to you Olaf, erm... I think somewhere in
this pile of garbage around my 'pooter I've got a fully fledged undersea
research/exploration/farming facility. Also a couple of mining/research
facilities down near the Marianas Trench. If your interested, let me
know, and I'll send it to you.
(assuming I can find the thing) :)

Pete
--
Pete Sims
A Smith and Wesson beats four aces.
Message no. 3
From: Marc Renouf renouf@********.com
Subject: Submarines
Date: Fri, 16 Jul 1999 12:48:38 -0400 (EDT)
On Fri, 16 Jul 1999, Geoff Skellams wrote:

> Actually, IIRC, I believe that submarines are far more efficient
> underwater than on the surface.

That is correct.

<naval architect mode>

The reason for this is because a ship's drag has three components
- friction drag, form drag, and wave drag. Friction drag is exactly what
it sounds like. Form drag is related to how the shape of the vessel
displaces water around the hull (for instance, long skinny ships don't
require as much transverse energy to "part" the water in front of them as
a ship with a flat prow would). Wave drag is the energy that's wasted in
making waves (i.e. the wake). A handy way to think of it is like building
up pressure in front of the vessel and creating suction behind the vessel
as it moves through the water.
As a side note, my esteemed GridSec colleague Graht brought up the
thing about the bulbous bow. Let me explain: A submerged bulb on the
front of a ship is designed specifically to create a bow wave, and is
"tuned" for a specific speed (because the waves caused by a ship propagate
through water at the same speed as the ship - you can tell how fast a
ship is travelling from a photograph by looking at the wavelength of the
transverse waves in its wake). The bulb is designed so that at the target
speed, the bow wave will cancel out the stern wave - basically you still
have the "pressure" of making the bow wave, but you've removed the
"suction" of making the stern wave, and thus reduced your overall wave
drag. Unfortunately, it only works well for a specific speed (related to
the type of bulb and the overall length of the vessel)
At higher speeds, wave drag becomes the dominant component for
surface vessels. However, in the case of submarines, if you're not
wasting any energy making waves, you only have to worry about friction and
form drag. Once a submarine reaches a certain critical depth (determined
by its speed), it no longer causes any significant waves on the surface,
so it loses wave drag all together. Granted, the friction drag is higher
because there's more hull surface area in contact with the water, but the
increase in friction and form drag is more than made up for by the
decrease in wave drag. This is why modern subs are much faster under
water than they are on the surface.
Further, there is the matter of cavitation. Propeller cavitation
is the result of sharp high-to-low pressure transitions across the fins of
a propeller (these pressure transitions are what give you "thrust"). If
the low-pressure side of the transition drops below the vapor pressure of
water, the water turns to steam (though not because it's hot). This
causes local bubbles to form. Unfortunately, since the water hasn't
raised in temperature, as soon as the pressure increases to its normal
level (i.e. as soon as the bubble gets away from the low pressure area),
it collapses. This has two effects: first, the impact of bubble formation
and collapse causes tiny shockwaves to hit the propeller, like hitting
thousands of times a second with a tiny hammer. This causes some prettey
intense wear and tear on a prop. Second, those same collapse-induced
shockwaves also propagate through the water, where they make a godawful
racket to any listening sonar.
Fortunately, the deeper you are in the water, the higher the
ambient pressure. The higher the ambient pressure, the less likely it is
that your propeller pressure transition will result in a sub-vapor level
pressure. It's like the water is "squeezed" harder, so it's harder to
make bubbles. Less bubbles = less noise. Less noise = more sneaky. More
sneaky = happy sub commander.

</naval arcthitect mode>

Make sense?

Marc Renouf (ShadowRN GridSec - "Bad Cop" Division)

Other ShadowRN-related addresses and links:
Mark Imbriaco <mark@*********.html.com> List Owner
Adam Jury <adamj@*********.html.com> Assistant List Administrator
DVixen <dvixen@****.com> Keeper of the FAQs
Gurth <gurth@******.nl> GridSec Enforcer Division
David Buehrer <graht@********.att.net> GridSec "Nice Guy" Division
ShadowRN FAQ <http://shadowrun.html.com/hlair/faqindex.php3>;
Message no. 4
From: Patrick Goodman remo@***.net
Subject: Submarines
Date: Fri, 16 Jul 1999 12:51:25 -0500
><naval architect mode>

::snip actual naval architect discussion::

></naval arcthitect mode>
>
> Make sense?

Now my brain hurts....thanks heaps, Marc....

Patrick
Message no. 5
From: Ereskanti@***.com Ereskanti@***.com
Subject: Submarines
Date: Fri, 16 Jul 1999 16:30:45 EDT
In a message dated 7/16/1999 12:41:28 PM US Eastern Standard Time,
renouf@********.com writes:

<SNIP>
> </naval arcthitect mode>
> Make sense?


Yes, and for whatever reason I could follow that section easily enough. Now
how is it I could rarely follow Andrew G's conversations???

-K
Message no. 6
From: Ereskanti@***.com Ereskanti@***.com
Subject: Submarines
Date: Fri, 16 Jul 1999 16:33:45 EDT
In a message dated 7/16/1999 3:15:12 AM US Eastern Standard Time,
atreloar@*********.com writes:

> Modern submarines surface for only a very few reasons. In order of
> frequency, 1) Returning to port (obviously) 2) Covert operations, 3)
> Onboard emergency, 4) Surrendering to the enemy.

Okay, here's a *really* strange idea. I'm going to stick with #1 here
actually, and just twist it a bit. I know the "tower" on most submarines is
only *so* big, but if a submarine were to have this tower modified to
retrieved VTOL type drones (LTA or Vector Thrust, IMO), it could be done, and
it could be done with relative quickness.

> For covert ops, they are usually on the surface for no more than 15
minutes,
> and it's usually less than 5. Being on the surface makes the submarine a
> whole lot more vulnerable for many reasons, primarily being increased
weapon
> damage possibility (ie surface guns and missiles actually work) and the
loss
> of the submarine's primary attribute, it's stealth. Telling a sub
commander
> that he'll have to be on the surface for a long time is the quickest way to
> make him nervous and get his veto of your idea. No sub commander will be
> volunteering for drone recover duty, believe me.

Okay, that makes sense. How about this for an alternative then? Lets' just
make the drones water sealed good for a medium depth (not more than 50 meters
in this case). We don't need 'em to have functional submersible engines, but
that is always a plus. On the submarine itself, can we employ a catch net
either in front or along the sides (retractable to the vessels side at most)
or as a purse net (like those used in Tuna Fishing)?

The drones *land* on the water, and then sink there. The submarine comes
along and scoops them up. Minor adjustments to a "ballast -like" mechanism
would keep the drones from sinking beyond a certain/specified depth.

I know all of this is fairly extreme, but I'm looking for something more in
the science possible this time and not the science probable.

-K
Message no. 7
From: Marc Renouf renouf@********.com
Subject: Submarines
Date: Sat, 24 Jul 1999 20:39:47 -0400 (EDT)
On Fri, 16 Jul 1999 Ereskanti@***.com wrote:

> <SNIP>
> > </naval arcthitect mode>
> > Make sense?
>
>
> Yes, and for whatever reason I could follow that section easily enough. Now
> how is it I could rarely follow Andrew G's conversations???

You're welcome. :) And the reason Adam's physics posts were
often so hard to follow is because he didn't translate the jargon, whereas
I made a conscious attempt to put things in laymans' terms. <shrug> Glad
to see it worked.

Marc

Further Reading

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Thwap!