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Message no. 1
From: Gurth <gurth@******.NL>
Subject: Newton's 3rd law (was Re: Advanced Weapons)
Date: Sun, 14 Sep 1997 13:06:50 +0100
Mike Bobroff said on 2:49/14 Sep 97...

> > The short answer: because there's a projectile shooting out of it, and
> > Action = -Reaction (ask Newton about that one).
>
> Ahh, but a kinetic rail-gun has no recoil because the shell being fired from
> it has not imparted any energy to the gun casing, other than air
> displacement.

*big sigh* One last time: if the railgun pushes the projectile one way,
the projectile pushes the railgun the other way.

Let's do a little test: Are you sitting on an office chair? Then pull
your feet up onto the chair, extend one of your arms horizontally, and
move it horizontally back and forth. Notice how the chair turns in the
exact opposite direction from the movement of your arm?

Would you attribute that to air displacement? Oh wait, perhaps to movement
of your spinal column that makes your lower body turn the chair? Believe
me, it isn't. The chair turns to the right because your arm goes to the
left, nothing more and nothing less.

All this is very basic physics: something moves one way, then something
else goes the other way, even if there's no visible connection between the
two. Ask any physics teacher if you need more detail and examples.

After this I'm not going to say more about why railguns have recoil.
Honest.

--
Gurth@******.nl - http://www.xs4all.nl/~gurth/index.html
Go see the profiteer
-> NERPS Project Leader & Unofficial Shadowrun Guru <-
-> The Plastic Warriors Page: http://www.xs4all.nl/~gurth/plastic.html <-

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Message no. 2
From: Peter David Boddy <pdboddy@****.CARLETON.CA>
Subject: Re: Newton's 3rd law (was Re: Advanced Weapons)
Date: Sun, 14 Sep 1997 09:06:53 EDT
Gurth writes:
> *big sigh* One last time: if the railgun pushes the projectile one way,
> the projectile pushes the railgun the other way.
>
> After this I'm not going to say more about why railguns have recoil.
> Honest.

Gurth is quite correct in this matter, I believe the law is "For every
action force, there is an equal and opposite reaction force". The key
here is the word force. That projectile that is being fired out of the
railgun is pushing as hard on the gun as the gun pushed on the projectile.
The reason why the gun doesn't go flying in the opposite direction, is the
the gun, it's mount, and it's controller provide more mass to hold the gun
in place. Nothing is holding the projectile in place, so off it goes
towards your target (if you're anywhere near a good enough shot =) ).

Try firing that railgun in space, no friction, low, or no, gravity, end
result: projectile goes one direction, gun and firer the other (unless
it's mounted on something big).

Now if everyone were to step off on the left foot at the same time....nah.

Pete

Pete aka Spitfire
----------------------------------------------------------------------
Peter David Boddy
Carleton University
Email address: pdboddy@****.carleton.ca
Email address: pdboddy@******.carleton.ca
Email address: bx955@*******.carleton.ca
----------------------------------------------------------------------
Message no. 3
From: "J. Keith Henry" <Ereskanti@***.COM>
Subject: Re: Newton's 3rd law (was Re: Advanced Weapons)
Date: Sun, 14 Sep 1997 10:44:25 -0400
In a message dated 97-09-14 07:10:04 EDT, gurth@******.NL writes:

>
> *big sigh* One last time: if the railgun pushes the projectile one way,
> the projectile pushes the railgun the other way.
>
> Let's do a little test: Are you sitting on an office chair? Then pull
> your feet up onto the chair, extend one of your arms horizontally, and
> move it horizontally back and forth. Notice how the chair turns in the
> exact opposite direction from the movement of your arm?
>
Gurth, take a step back from what you are saying. The "getting up from a
chair", uses direct physical imparting of energy from one state/object to
another. A Kinetic Rail gun has a different form of imparted energy.
Correction, a different method, in which the energy is being imparted upon
the object. You example, and thus this direction of your argument is
invalid. If you want to use a scientific method guy, use one that has
relevance. If you do not operate within the areas of relevance, you
invalidate not only yourself, but your argument which will move beyond you
and influence others. That is called misinformation.

It is the way of things, you know this. :)
-K
Message no. 4
From: David Thompson <david.s.thompson@****.EDU>
Subject: Re: Newton's 3rd law (was Re: Advanced Weapons)
Date: Sun, 14 Sep 1997 13:36:38 -0400
At 10:44 AM 9/14/97 -0400, you wrote:
>In a message dated 97-09-14 07:10:04 EDT, gurth@******.NL writes:
>
>>
>> *big sigh* One last time: if the railgun pushes the projectile one way,
>> the projectile pushes the railgun the other way.
>>
>> Let's do a little test: Are you sitting on an office chair? Then pull
>> your feet up onto the chair, extend one of your arms horizontally, and
>> move it horizontally back and forth. Notice how the chair turns in the
>> exact opposite direction from the movement of your arm?
>>
>Gurth, take a step back from what you are saying. The "getting up from a
>chair", uses direct physical imparting of energy from one state/object to
>another. A Kinetic Rail gun has a different form of imparted energy.
> Correction, a different method, in which the energy is being imparted upon
>the object. You example, and thus this direction of your argument is
>invalid. If you want to use a scientific method guy, use one that has
>relevance. If you do not operate within the areas of relevance, you
>invalidate not only yourself, but your argument which will move beyond you
>and influence others. That is called misinformation.
>
>It is the way of things, you know this. :)

Gurth's example was of conservation of angular momentum, close enough in
terms of explaining action/reaction if you ask me.

--DT
Message no. 5
From: Jaymz <justin@******.NET>
Subject: Re: Newton's 3rd law (was Re: Advanced Weapons)
Date: Sun, 14 Sep 1997 12:45:20 -0500
At 09:06 AM 9/14/97 EDT, Peter David Boddy wrote:
#Try firing that railgun in space, no friction, low, or no, gravity, end
#result: projectile goes one direction, gun and firer the other (unless
#it's mounted on something big).

Umm, even the Mir would be affected by this.

I guess that's a bad example.

But if one *was* trapped in space with only a gun and an oxygen tank,
they'd be able to crontrol where they were going until they ran ou of Ammo.

--
/--justin@****.mcp.com----------------------justin@******.net--\
|Justin Bell NIC:JB3084| Time and rules are changing. |
|Simon & Schuster | Attention span is quickening. |
|Programmer | Welcome to the Information Age. |
\------------ http://www.mcp.com/people/justin/ ---------------/
Message no. 6
From: Matb <mbreton@**.NETCOM.COM>
Subject: Re: Newton's 3rd law (was Re: Advanced Weapons)
Date: Fri, 12 Sep 1997 21:33:52 -0700
> I guess that's a bad example.

> But if one *was* trapped in space with only a gun and an oxygen tank,
> they'd be able to crontrol where they were going until they ran ou of Ammo.

A very rough approximation of "control" there. Actually, this reminds
me a lot of college psychology course; there's a 'survival checklist' of
about fifteen items you might want if you were stranded on the moon, and
a CO2 pistol is listed among them, for exactly the reason you described.
Message no. 7
From: James Lindsay <jlindsay@******.CA>
Subject: Re: Newton's 3rd law (was Re: Advanced Weapons)
Date: Sun, 14 Sep 1997 18:44:33 GMT
On Sun, 14 Sep 1997 13:36:38 -0400, David Thompson wrote:

> At 10:44 AM 9/14/97 -0400, you wrote:

> >Gurth, take a step back from what you are saying. The "getting up from a
> >chair", uses direct physical imparting of energy from one state/object to
> >another. A Kinetic Rail gun has a different form of imparted energy.
> > Correction, a different method, in which the energy is being imparted upon
> >the object. You example, and thus this direction of your argument is
> >invalid. If you want to use a scientific method guy, use one that has
> >relevance. If you do not operate within the areas of relevance, you
> >invalidate not only yourself, but your argument which will move beyond you
> >and influence others. That is called misinformation.
> >
> >It is the way of things, you know this. :)
>
> Gurth's example was of conservation of angular momentum, close enough in
> terms of explaining action/reaction if you ask me.

How 'bout this. Place a piece of 1/8" steel plate on a table top.
Take a magnet and try to pick up the plate _without_ touching it. As
you might expect, the plate will "jump" up and come into contact with
the magnet. However, you will also notice another force trying to
pull the magnet out of your hand, *downwards* towards the steel plate
(and it ain't because the force of gravity suddenly changed :)

In _this_ example, imagine that the steel plate is your projectile and
the magnet is your linear accelerator. The applied force is even the
same in both cases: magnetism.

James W. Lindsay Vancouver, British Columbia
"http://www.prosperoimaging.com/ground_zero";

"Give me the strength to change the things I can,
the grace to accept the things I cannot,
and a great big bag of money."
Message no. 8
From: "J. Keith Henry" <Ereskanti@***.COM>
Subject: Re: Newton's 3rd law (was Re: Advanced Weapons)
Date: Sun, 14 Sep 1997 15:03:36 -0400
In a message dated 97-09-14 14:45:10 EDT, jlindsay@******.ca writes:

> How 'bout this. Place a piece of 1/8" steel plate on a table top.
> Take a magnet and try to pick up the plate _without_ touching it. As
> you might expect, the plate will "jump" up and come into contact with
> the magnet. However, you will also notice another force trying to
> pull the magnet out of your hand, *downwards* towards the steel plate
> (and it ain't because the force of gravity suddenly changed :)
>
> In _this_ example, imagine that the steel plate is your projectile and
> the magnet is your linear accelerator. The applied force is even the
> same in both cases: magnetism.
>
a major question arises. Is the proportion of the "plate" vs. the
"magnet"
the same as it is a Rail Gun? Consider the mass/volume comparisons to a
Bullet/Chemical(explosive) discharge.

I realize there is a reaction corelation, but for Rail Guns to "be all they
are", the proportional ratios are not so vast as to cause the
equivalent/comparisonal recoil ranges.

-K
Message no. 9
From: Gurth <gurth@******.NL>
Subject: Re: Newton's 3rd law (was Re: Advanced Weapons)
Date: Sun, 14 Sep 1997 21:42:16 +0100
J. Keith Henry said on 10:44/14 Sep 97...

> Gurth, take a step back from what you are saying. The "getting up from a
> chair", uses direct physical imparting of energy from one state/object to
> another. [rest snipped]

Nobody said anything about getting up from a chair; I suggest you read a
little more carefully before you reply to a message.

However, I admit the example wasn't all that good, but it was the first
thing that came into my mind when thinking about an example for action =
-reaction, apart from the "jumping out of a boat" thing which isn't as
easy to do immediately because not many people have a lake and a rowboat
handy when reading email.

--
Gurth@******.nl - http://www.xs4all.nl/~gurth/index.html
Go see the profiteer
-> NERPS Project Leader & Unofficial Shadowrun Guru <-
-> The Plastic Warriors Page: http://www.xs4all.nl/~gurth/plastic.html <-

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Message no. 10
From: James Lindsay <jlindsay@******.CA>
Subject: Re: Newton's 3rd law (was Re: Advanced Weapons)
Date: Sun, 14 Sep 1997 22:11:40 GMT
On Sun, 14 Sep 1997 15:03:36 -0400, J. Keith Henry wrote:

> In a message dated 97-09-14 14:45:10 EDT, jlindsay@******.ca writes:
>
> > How 'bout this. Place a piece of 1/8" steel plate on a table top.
> > Take a magnet and try to pick up the plate _without_ touching it. As
> > you might expect, the plate will "jump" up and come into contact with
> > the magnet. However, you will also notice another force trying to
> > pull the magnet out of your hand, *downwards* towards the steel plate
> > (and it ain't because the force of gravity suddenly changed :)
> >
> > In _this_ example, imagine that the steel plate is your projectile and
> > the magnet is your linear accelerator. The applied force is even the
> > same in both cases: magnetism.
> >
> a major question arises. Is the proportion of the "plate" vs. the
"magnet"
> the same as it is a Rail Gun? Consider the mass/volume comparisons to a
> Bullet/Chemical(explosive) discharge.

No it is not, but that wasn't my point. I was trying to get across
the idea that weapons built around the principles of magnetic fields
still produce recoil. This was just a simple experiment that anyone
could do to prove my point about conservation of momentum with regards
to magnetism.

> I realize there is a reaction corelation, but for Rail Guns to "be all they
> are", the proportional ratios are not so vast as to cause the
> equivalent/comparisonal recoil ranges.

The same could be said for conventional firearms (bullet mass is on
the scale of about 0.5% that of the mass of a rifle). Momentum is
still calculated as "mass x velocity". This fact does not change
whether the weapon is a rail gun or not.

As I pointed out in another post, there is a *major* difference
between *raw* recoil and *perceived* recoil.

James W. Lindsay Vancouver, British Columbia
"http://www.prosperoimaging.com/ground_zero";

"Give me the strength to change the things I can,
the grace to accept the things I cannot,
and a great big bag of money."
Message no. 11
From: Les Ward <lward@*******.COM>
Subject: Newton's 3rd law (was Re: Advanced Weapons)
Date: Mon, 15 Sep 1997 10:34:14 -0400
I don't claim to have the answer to this whole rail gun recoil thing, but
it seems to me that several things are being ignored.

People are only talking about what happens inside the barrel of the gun.
While this is fine for conventional weapons, rail guns are a different
beast. Rail guns work because inside the barrel _part_ of a magnetic field
is directed down the length of the barrel. If you can picture of diagram of
the thing, all the "force lines" go one direction; however, the field
extends outside the barrel as well in an equal and opposite direction. In a
non-firing rail gun (well, in a solenoid, anyway), the magnetic field is
on, but the gun does not move because the field directs force in two
directions at once.

In a conventional weapon, no force is exerted on anything until the trigger
is pulled. Once pulled a large force is created at the back of the barrel.
Many people seem to be of the opinion that the bullet somehow exerts force
back on the gun. This is not true. The expanding gasses that push the
bullet, however, do push back on the gun (and against the barrel).

When you throw a ball in space, the ball moves forward and you move
backward. This happens not because the ball "pushed back", but because your
arm muscles pushed against your body.

Which brings us to Gurth's point
> *big sigh* One last time: if the railgun pushes the projectile one way,
> the projectile pushes the railgun the other way.

This seems to me to be the wrong way to look at the problem, because the
railgun does not push anything, nor does the projectile. The magnetic
field, however, pushes both the gun and the projectile, in opposite
directions.

I have no conclusion about all this, but it seems to me, without
remembering a whole lot of the physics, that the rail gun may generate less
recoil because nothing changes about the forces acting on it bewteen firing
and not-firing; the magnetic field stays the same. This is not true of
conventional weapons, where huge force is generated quickly from nothing.
Secondly, conventional weapons do not have any forces acting outside the
barrel (apart from the user), and rail guns do.

Wordman
wordman@*****.com
Message no. 12
From: David Thompson <david.s.thompson@****.EDU>
Subject: Re: Newton's 3rd law (was Re: Advanced Weapons)
Date: Mon, 15 Sep 1997 19:33:39 -0400
wordman@*****.com wrote:

>This seems to me to be the wrong way to look at the problem, because the
>railgun does not push anything, nor does the projectile. The magnetic
>field, however, pushes both the gun and the projectile, in opposite
>directions.
>
>I have no conclusion about all this, but it seems to me, without
>remembering a whole lot of the physics, that the rail gun may generate less
>recoil because nothing changes about the forces acting on it bewteen firing
>and not-firing; the magnetic field stays the same. This is not true of
>conventional weapons, where huge force is generated quickly from nothing.
>Secondly, conventional weapons do not have any forces acting outside the
>barrel (apart from the user), and rail guns do.
>

This is not strictly true. The magnetic field may be on the whole time
(though, it wouldn't have to be, you could turn on the current only to fire
-- and that would probably save power), but the magnetic field is not the
force. The force is produced by the interaction of the magnetic field with
the moving charge in the projectile, so it is only while current is running
through the projectile (ie, when it is being fired) that you have force.
Therefore, force is exerted on the projectile only when it is being fired
(there is no force when it is not fired -- same as a chemical firearm),
force must therefore be exerted on the gun. (Or, in momentum terms, in the
system of gun-projectile, the lorentz force is an internal force, so
momentum must be conserved, so there is recoil -- whether or how it is
perceived is a different issue.)

Note, before people freak out, the above is in response to a statement
about railguns, and may not apply specifically to coilguns and other
accelorators, but in general the conclusion is correct -- there is recoil,
dammit!

--DT
Message no. 13
From: Spike <u5a77@*****.CS.KEELE.AC.UK>
Subject: Re: Newton's 3rd law (was Re: Advanced Weapons)
Date: Mon, 15 Sep 1997 14:14:05 +0100
|All this is very basic physics: something moves one way, then something
|else goes the other way, even if there's no visible connection between the
|two. Ask any physics teacher if you need more detail and examples.

Or as the old saying goes...

"Every ACTION has an EQUAL and OPPOSITE REACTION"

--
______________________________________________________________________________
|u5a77@*****.cs.keele.ac.uk| "Are you pondering what I'm pondering Pinky?" |
|Andrew Halliwell | |
|Principal subjects in:- | "I think so brain, but this time, you control |
|Comp Sci & Electronics | the Encounter suit, and I'll do the voice..." |
------------------------------------------------------------------------------
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|5++ X+/++ R+ tv+ b+ D G e>PhD h/h+ !r! !y-|I can't say F**K either now! :( |
------------------------------------------------------------------------------
Message no. 14
From: "J. Keith Henry" <Ereskanti@***.COM>
Subject: Re: Newton's 3rd law (was Re: Advanced Weapons)
Date: Tue, 16 Sep 1997 19:35:57 -0400
In a message dated 97-09-14 15:41:14 EDT, gurth@******.NL writes:

> > Gurth, take a step back from what you are saying. The "getting up from a
> > chair", uses direct physical imparting of energy from one state/object
to
> > another. [rest snipped]
>
> Nobody said anything about getting up from a chair; I suggest you read a
> little more carefully before you reply to a message.
>
<snipped the part on "not being a good example" that followed this>

Gurth, I did read the part and it mentioned a chair. Someone else responded
with material on the concept of "angualr physics".
-K
Message no. 15
From: "J. Keith Henry" <Ereskanti@***.COM>
Subject: Re: Newton's 3rd law (was Re: Advanced Weapons)
Date: Tue, 16 Sep 1997 19:53:13 -0400
In a message dated 97-09-14 18:18:45 EDT, jlindsay@******.ca writes:

> > I realize there is a reaction corelation, but for Rail Guns to "be all
they
> > are", the proportional ratios are not so vast as to cause the
> > equivalent/comparisonal recoil ranges.
>
> The same could be said for conventional firearms (bullet mass is on
> the scale of about 0.5% that of the mass of a rifle). Momentum is
> still calculated as "mass x velocity". This fact does not change
> whether the weapon is a rail gun or not.
>
I understand all of that, but the recoil in a chemical/conventional firearm
isn't from the bullet leaving the chamber entirely. It is from the explosive
release of energy of the propellant.

Come on folks, even I knew that one.
-K
Message no. 16
From: James Lindsay <jlindsay@******.CA>
Subject: Re: Newton's 3rd law (was Re: Advanced Weapons)
Date: Wed, 17 Sep 1997 05:34:42 GMT
On Tue, 16 Sep 1997 19:53:13 -0400, J. Keith Henry wrote:

> In a message dated 97-09-14 18:18:45 EDT, jlindsay@******.ca writes:
>
> > > I realize there is a reaction corelation, but for Rail Guns to "be all
> they
> > > are", the proportional ratios are not so vast as to cause the
> > > equivalent/comparisonal recoil ranges.
> >
> > The same could be said for conventional firearms (bullet mass is on
> > the scale of about 0.5% that of the mass of a rifle). Momentum is
> > still calculated as "mass x velocity". This fact does not change
> > whether the weapon is a rail gun or not.
> >
> I understand all of that, but the recoil in a chemical/conventional firearm
> isn't from the bullet leaving the chamber entirely. It is from the explosive
> release of energy of the propellant.

The explosive release of energy may take place in all directions but
the design of the weapon lets the gases escape in only one direction.
To do so, it must push a slug of lead with a certain mass at a certain
velocity in one direction. Mass x Velocity is momentum, and an equal
amount of momentum exists in the rifle moving in the opposite
direction. The actual momentum of a rifle would be equal to the
combined mass of the projectile and propellent gases, times the
combined velocity of the same. The explosive gases don't play a big
enough part for their mass and velocity to be included, however.


James W. Lindsay Vancouver, British Columbia
"http://www.prosperoimaging.com/ground_zero";

"Give me the strength to change the things I can,
the grace to accept the things I cannot,
and a great big bag of money."
Message no. 17
From: "Paul J. Adam" <shadowrn@********.DEMON.CO.UK>
Subject: Re: Newton's 3rd law (was Re: Advanced Weapons)
Date: Wed, 17 Sep 1997 22:22:41 +0100
In article <970916194714_-1734240515@*******.mail.aol.com>, "J. Keith
Henry" <Ereskanti@***.COM> writes
>I understand all of that, but the recoil in a chemical/conventional firearm
>isn't from the bullet leaving the chamber entirely. It is from the explosive
>release of energy of the propellant.
>
>Come on folks, even I knew that one.

The recoil of a firearm is because a bullet is being accelerated from
rest to muzzle velocity, and the weapon reacts in the opposite
direction.

Crossbows have recoils. Railguns have recoil. Coilguns have recoil.

The only way to get around recoil is either to use a rocket launcher -
where the weapon is just a guide rail for a self-propelled projectile -
or the Davis Gun principle, where you throw a projectile one way and an
equivalent impulse (originally a charge of grease and lead shot, later a
high-velocity blast of gas or a pack of plastic slivers) in the opposite
direction.

--
There are four kinds of homicide: felonious, excusable, justifiable and
praiseworthy...

Paul J. Adam paul@********.demon.co.uk
Message no. 18
From: Tobias Berghoff <Zixx@*****.TEUTO.DE>
Subject: Re: Newton's 3rd law (was Re: Advanced Weapons)
Date: Tue, 16 Sep 1997 13:04:00 GMT
on 15.09.97 david.s.thompson@****.EDU wrote:

[Railguns and recoil]

dst> Note, before people freak out, the above is in response to a statement
dst> about railguns, and may not apply specifically to coilguns and other
dst> accelorators, but in general the conclusion is correct -- there is
dst> recoil, dammit!

Yup! To make this short: Does the word 'impulse' ring any scientific
bells? That was that thing about it always being the same in a close
system. A railgun is a closed system, so the same power that is stored in
the bullets speed is the same as your recoil (If anyone wants to calculate
the exact recoil, here's the fromula: mass1 * delta-velocity1 = -(mass2 *
delta-velocity2) or 'm1 * v1 = -(m2 * v2))



Tobias Berghoff a.k.a Zixx a.k.a. Charon, your friendly werepanther physad.

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