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Message no. 1
From: dhinkley@***.ORG
Subject: Underwater Explosions
Date: Sun, 5 Jan 1997 15:27:39 +0000
I am currently developing a set of rules for the use of depth charges and similar
devices as a part of a submission I am preparing for the current
NERPS project. I have worked out the basic concept but I lack a bit
of technical knowledge to finish them.

As a explosion underwater is basically the same as one in the air. The
extremely rapid combustion of the explosive creates a expanding cloud
of hot gases. This cloud is sperical in shape and as it expands it
creates a shock wave that radiates from the center of the expostion.
As it expands the strength of the wave decreases. Please note that I
am only conserned with the explosion and am not considering any
fragments from the bomb case.

As I understand it the difference between the effects of the same
amount of explosive detonated in the air and in water, is that
because water is relatively uncompressable the shock wave remains
stronger longer. That is the effective damage radius of an underwater
explosion would be greater then the same amount in the air.

What I don't know is how much more effective. My thought is to adapt
the basic explosion rules from SRII pages 97-98 by adjusting the
Power Level reduction. The question is how much.

Any thoughts, data, or suggestions would be greatly appreciated .


David Hinkley
dhinkley@***.org
******************************************************
They that can give up essential liberty to obtain a
little temporary safety deserve niether liberty or
safety.
Ben Franklin
Message no. 2
From: Gurth <gurth@******.NL>
Subject: Re: Underwater Explosions
Date: Mon, 6 Jan 1997 12:33:01 +0100
dhinkley@***.ORG said on 15:27/ 5 Jan 97...

> What I don't know is how much more effective. My thought is to adapt
> the basic explosion rules from SRII pages 97-98 by adjusting the
> Power Level reduction. The question is how much.

Phoenix Command gives underwater explosions a x10 multiplier to the Base
Concussion, but unfortunately this doesn't mean anything for the blast
radius of the explosion in that system -- BC is the damage done to a
target in the open at a certan range. For example, an M67 grenade does 190
damage at 1 hex (=2 yards) distance from the explosion, so underwater this
would be 1900 points.

Apart from this little bit, I have no idea how much more effective an
explosive is underwater.

--
Gurth@******.nl - http://www.xs4all.nl/~gurth/index.html
Suppress it if you can.
-> NERPS Project Leader & Unofficial Shadowrun Guru <-
-> The Plastic Warriors Page: http://www.xs4all.nl/~gurth/plastic.html <-

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Message no. 3
From: "Paolo Falco, Explorer" <Falco@****.IT>
Subject: Re: Underwater Explosions
Date: Mon, 6 Jan 1997 17:15:38 +0000
5 Jan 97, 15:27, on the downward time curve to Armageddon,
dhinkley@***.ORG said:

> I am currently developing a set of rules for the use of depth
> [...]
> What I don't know is how much more effective. My thought is to adapt
> the basic explosion rules from SRII pages 97-98 by adjusting the
> Power Level reduction. The question is how much.

Well you could try using the density ratio of air/water, but I'm no
military expert...

Since you can VERY effectively fish with grenades, I'd say between 5x
and 10x, but I admit that I'm just guessing since the density ratio
must be much more than 10:1 (I'm sorry I don't want to get up and
look at it)...

------------------------------------------------------------------
Paolo Falco | "And they'll never know the gold, or the copper
(Explorer) | in your hair" (S.Vega:"The world before Columbus")
------------------------------------------------------------------
http://www.geocities.com/SoHo/2717
Paradoxal Skating page for Gamers with AnarcoLemming view on life
Message no. 4
From: Keith W Suderman <ksuderma@******.ACNS.FSU.EDU>
Subject: Re: Underwater explosions
Date: Tue, 7 Jan 1997 13:10:43 -0500
I'm not sure if this sheds any light on the subject (in fact, I'm pretty
sure it doesn't), but the density ratio of water to air is 825:1. (At
least that's what I tell beginning scuba students).
We also tell them that sound travels four times as fast (and that
that's why they can't tell what direction the sound is coming from).
Maybe that's (slightly) more useful to the discussion.

Unfortunately, beginning scuba doesn't really cover underwater
explosions very thoroughly. A pity- I bet we'd get more interesting
students if it did.... :)


Keith
Message no. 5
From: Jon Camfield <griffjon@****.UTEXAS.EDU>
Subject: Re: Underwater explosions
Date: Tue, 7 Jan 1997 13:10:33 -0700
> Unfortunately, beginning scuba doesn't really cover underwater
>explosions very thoroughly. A pity- I bet we'd get more interesting
>students if it did.... :)
>Keith

Maybe you should petition for the inclusion of explosion coverage-- you
never know when you might get an airtank rupture....

Is there going to be a large section on underwater ops? I am unable
to find any info on scuba gear, or those nifty propellor things, or heck,
submarines, underwater combat (which guns work, new guns, harpoon guns, etc)
TN modifiers for swinging melee weapons underwater, movement modifiers, and
can a mono whip swing underwater?

Perhaps I could work on some of this if it's not already been taken.

________________________________________________________________________
Jon Camfield | I thought it was alive
GriffJon the Sinistral Minstrel | Thought I could empathize
vis_jmc@****.shsu.edu | With its downward flight, but
GriffJon@****.utexas.edu | It was only a leaf
http://www.shsu.edu/~vis_jmc | Falling in late summer.
________________________________________________________________________
She asked why, I answered, "Because tears fall like blood, not shatter like
crystal, like a breaking heart" and she understood.
Message no. 6
From: Keith W Suderman <ksuderma@******.ACNS.FSU.EDU>
Subject: Re: Underwater explosions
Date: Tue, 7 Jan 1997 18:31:49 -0500
[Sorry to everyone who pays by volume- I tried to answer in only a few
short lines....]


Jon wrote:
>
I am unable
> to find any info on scuba gear, or those nifty propellor things, or heck,
> submarines, underwater combat (which guns work, new guns, harpoon guns, etc)
> TN modifiers for swinging melee weapons underwater, movement modifiers, and
> can a mono whip swing underwater?
>
> Perhaps I could work on some of this if it's not already been taken.
>

Jon,
I can spam the list for days, itemizing my wish-list... I won't-
but I can help with a few of your questions:

-nifty propellor things-
a.k.a. DPV's (Diver Propulsion Vehicles), but we just call them scooters.
Oceanic Mako (was DV-100 and DV-3X before that) weighs 54 pounds,
neutral in fresh water. Approx 30" long, 15" dia. Constant speed motor
drives a variable-pitch prop. Top speed (what else would you use???) is
150-200 feet per minute and lasts about 50-60 minutes. Varies with the
size and especially the proficiency of the rider. (Note that 200 fpm
is about walking speed. Not fast, until you try it underwater in
limited visibility...)Looks like a stubby black torpedo. Attaches to belt
with a harness, rider is towed along behind it. Cost: $1300+
AquaZepp weighs around 100 pounds. Approx 6' long. Top speed is
a sizzling 300 fpm- enough to remove your mask if you look sideways.
Looks like a long orange rocket with a steering vane on the nose. Rider
actually lays on top, sits on a T-bar, and really rides this beast. Cost:
$6000.

All I know about submarines- well, the most interesting thing I
know about submarines, anyway- is that one of my aquaintences (sp?) is
building one. It is a one-man, unpressurized (i.e. pilot wears scuba)
submersible called the ROBOTUNA. Uh-huh. The guy building it answers to
the name "Bubba" so there you go...

Movement underwater... sucks. Tough work. Drag increases twice
as fast as speed (am I saying that right?). What I mean is that it takes
four times as much energy to go twice as fast. And even the best
regulator feels like breathing through a straw when you're working hard at
depth.
In full cave-diving kit [doubles, canister light, etc, etc], I can
relax and enjoy the dive at 40 fpm. If I am pushing it, I can maintain
about twice that- but I'm not enjoying myself anymore. Short bursts of
higher speed are quite possible, but running out of breath is not much
fun- I don't recommend it. Scooters are really the way to go.

I know zip about underwater combat. Well, sometimes we have some
pretty spirited dogfights on the scooters, they aren't lethal (so far).

I was about to list some guesses for gear prices, but an accurate
list can be found at:
http://www.infinet.com/~toddl/caverig/parts.html

Feel free to ask more questions- I like to talk about diving
almost as much as I like doing it.

Keith


Oh yeah- these are all my opinions and perceptions. YMMV!
Message no. 7
From: Calvin Hsieh <u2172778@*******.ACSU.UNSW.EDU.AU>
Subject: Re: Underwater explosions
Date: Wed, 8 Jan 1997 11:36:11 +1100
On Tue, 7 Jan 1997, Keith W Suderman wrote:

> I'm not sure if this sheds any light on the subject (in fact, I'm pretty
> sure it doesn't), but the density ratio of water to air is 825:1. (At
> least that's what I tell beginning scuba students).
> We also tell them that sound travels four times as fast (and that
> that's why they can't tell what direction the sound is coming from).
> Maybe that's (slightly) more useful to the discussion.

I don't suppose anyone out there has a basic physics textbook out there.
I can no longer remember the "n" for water (as for waves).

Shaman
Message no. 8
From: "Paolo Falco, Explorer" <Falco@****.IT>
Subject: Re: Underwater explosions
Date: Thu, 9 Jan 1997 10:17:59 +0000
8 Jan 97, 11:36, on the downward time curve to Armageddon, Calvin
Hsieh said:

> On Tue, 7 Jan 1997, Keith W Suderman wrote:
>
> > I'm not sure if this sheds any light on the subject (in fact, I'm
> > pretty sure it doesn't), but the density ratio of water to air is
> > 825:1. (At least that's what I tell beginning scuba students).
> > We also tell them that sound travels four times as fast
> > (and that
> > that's why they can't tell what direction the sound is coming
> > from). Maybe that's (slightly) more useful to the discussion.
>
> I don't suppose anyone out there has a basic physics textbook out
> there. I can no longer remember the "n" for water (as for waves).

Actually, n, or refraction index, is used for measuring the speed
of light in a medium.
However, speaking with my pals (we are all wannabee physicists) we
decided that the REAL parameter to be used is compressibility...
Sadly, we don't know how much the compressibility of water is. If we
knew, the formula would be:

R(water)/R(air) = Compr(Water)/Compr(air)

We are unsure as wether to add a cubing at the end, since there are
three degrees of freedom, but that would come according to how
compressibility is calculated... :)

------------------------------------------------------------------
Paolo Falco | "And they'll never know the gold, or the copper
(Explorer) | in your hair" (S.Vega:"The world before Columbus")
------------------------------------------------------------------
http://www.geocities.com/SoHo/2717
Paradoxal Skating page for Gamers with AnarcoLemming view on life
Message no. 9
From: ken webb <hbphy009@*****.CSUN.EDU>
Subject: Re: Underwater explosions
Date: Thu, 9 Jan 1997 14:15:10 -0800
On Thu, 9 Jan 1997, Paolo Falco, Explorer wrote:
> However, speaking with my pals (we are all wannabee physicists) we
> decided that the REAL parameter to be used is compressibility...
> Sadly, we don't know how much the compressibility of water is.

<tries to fit into Adam Getchell's shoes>
Compressibility is derived from the bulk modulus (it is the inverse of
the bulk modulus.) As it turns out, water is VERY incompressible (its
volume decreases by .000050 of its original volume for each atmosphere
increase of pressure.) That's why they use water to pressure test pipes
for leaks.

As for how it is calculated: Bulk modulus: B = -V*(dp/dV)
Compressibility: k = 1/B

As for what you were trying to calculate with compressibility, I can't
remember... :)

--________________________________________________________________________--
'Kenneth M. Webb | Geek} GS d->+ s:-- a-- C++ HLU+ P? L++ E W N++ '
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''''''''''''''''''''''''^'''''''''''''''''''''''''''''''''''''''''''''''''
Message no. 10
From: Peter Coxon <coxoff@***.COM>
Subject: Re: Underwater explosions
Date: Wed, 8 Jan 1997 23:14:37 UT
>> Unfortunately, beginning scuba doesn't really cover underwater
>>explosions very thoroughly. A pity- I bet we'd get more interesting
>>students if it did.... :)
>>Keith

>Maybe you should petition for the inclusion of explosion coverage-- you
>never know when you might get an airtank rupture....

> Is there going to be a large section on underwater ops? I am >unable
>to find any info on scuba gear, or those nifty propellor things, or heck,
>submarines, underwater combat (which guns work, new guns, harpoon >guns, etc)
>TN modifiers for swinging melee weapons underwater, movement >modifiers, and
>can a mono whip swing underwater?

>Perhaps I could work on some of this if it's not already been taken.

>Jon Camfield
Hi ((it's a good place to start okay)), I am kind of dealing with the peronal
combat type things...I havn't got loads done, mainly just equipment, if I sent
you a copy, it would kind of give you a place to start if you do want to do
the rules.....
And a note to anyone else..Any equipment suggestion or other stuff would be
gratefully accepted.
tim ntoo
"There is too much blood in my caffeine system"
Message no. 11
From: Jon Camfield <griffjon@****.UTEXAS.EDU>
Subject: Re: Underwater explosions
Date: Fri, 10 Jan 1997 17:12:24 -0700
>>Perhaps I could work on some of this if it's not already been taken.
>
>>Jon Camfield
>Hi ((it's a good place to start okay)), I am kind of dealing with the peronal
>combat type things...I havn't got loads done, mainly just equipment, if I sent
>you a copy, it would kind of give you a place to start if you do want to do
>the rules.....

>"There is too much blood in my caffeine system"

I've been e-maling with Keith about some rules, but haven't developed much
past skills and some massive modifiers for combat. I'm not sure how much
time I'll have this semester, but I'd be willing to try to churn out some
rules. I definitely think that underwater stuff should be looked into
(heck, a whole sourebook, even!)

________________________________________________________________________
Jon Camfield | I thought it was alive
GriffJon the Sinistral Minstrel | Thought I could empathize
vis_jmc@****.shsu.edu | With its downward flight, but
GriffJon@****.utexas.edu | It was only a leaf
http://www.shsu.edu/~vis_jmc | Falling in late summer.
________________________________________________________________________
She asked why, I answered, "Because tears fall like blood, not shatter like
crystal, like a breaking heart" and she understood.

Further Reading

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