Oh come on,get a grip - weapon dmg silly

[iainjcoleman]

on the subject of guns - can someone tell me why gauss rifles have low recoil? Even with a small bullet (4mm), higher velocity should mean higher recoil. f=ma and all that...

If we assume that the damage done by the projectile is proportional to its kinetic energy, which is a reasonable simplification, then for a given level of damage a faster bullet will have less recoil. This is because recoil is determined by the momentum of the bullet, while damage is determined by kinetic energy.

Momentum p = mv

Energy E = (1/2)mv^2

With a little algebra, this becomes p = sqrt(2Em). So, for a given E, reducing the mass m by a factor x reduces the momentum, and therefore the recoil, by a factor sqrt(x).

 

[katadder]

its the way they are fired. due to using magnetic rails to accelerate things it has nothing pressing backwards. unlike a normal rifle that has all the eplosive gases propelling it which has to push against the rear of the gun for forward momentum.

No it isn't. Conservation of momentum means the momentum of the weapon must be equal and opposite to the momentum of the projectile.

maybe with standard weapons of today as they use a chemical reaction with a chemical reaction actually pushing the round out so it has to push against something (as the gases push both directions but only one direction has any give in it).
a rail weapon uses magnetic acceleration, so its not pushing against anything, therefore less recoil.

 

[iainjcoleman]

its the way they are fired. due to using magnetic rails to accelerate things it has nothing pressing backwards. unlike a normal rifle that has all the eplosive gases propelling it which has to push against the rear of the gun for forward momentum.

No it isn't. Conservation of momentum means the momentum of the weapon must be equal and opposite to the momentum of the projectile.

maybe with standard weapons of today as they use a chemical reaction with a chemical reaction actually pushing the round out so it has to push against something (as the gases push both directions but only one direction has any give in it).
a rail weapon uses magnetic acceleration, so its not pushing against anything, therefore less recoil.

The railgun projectile puches against the railgun via the magnetic field, just as the bullet pushes against the slugthrower vie the explosive gases.

Look, conservation of momentum is one of the most fundamental laws of the universe, deeply connected to the symmetries of spacetime. If the projectile gains momentum p, then the gun must gain momentum -p. This is not in any sense a controversial issue: it has been settled scientific fact for some centuries.

 

[katadder]

why does the railgun push against the gun? its a magnetic rail that accelerates it and theres no pushing backwards. at most you have to overcome the friction of your round which wont be much. which is why alot less recoil than a chemical reaction slugger

 

[mhensley]

hmm.. i just found this interesting bit-

http://www.newton.dep.anl.gov/newton/askasci/1993/physics/PHY24.HTM

Recoil and Rail Guns

Question: Do magnetically powered "rail guns" recoil less?
---------------------------------------
No. No kind of gun can be truly recoil less. Newton's third
law, the conservation of momentum, guarantees this. Even a laser has some
recoil, since photons have momentum. In the rail gun, the momentum given to
the projectile must be matched by the momentum given to the "stationary" part
of the gun. If the gun is firmly anchored, this momentum is given to the
entire mass of the planet and you will not see much recoil. But the force on
the gun during the launch will be quite high, equal to the force on the
projectile.

 

[iainjcoleman]

why does the railgun push against the gun? its a magnetic rail that accelerates it and theres no pushing backwards. at most you have to overcome the friction of your round which wont be much. which is why alot less recoil than a chemical reaction slugger

My usual rates for physics tuition start at £20 per hour. Fortunately, there are free resources on the web. You could start with the following:

Newton's Third Law of Motion

Newton's Laws of Motion

Conservation of Linear Momentum

I hope this is helpful to you.

 

[mhensley]

This may explain the low recoil-

http://www.military.com/soldiertech/0,14632,Soldiertech_RailGuns,,00.html

Finally, since the individual magnetic fields created in the rails are repulsed by one another, a tremendous strain is placed on the rails as they try to push away from one another. While rail guns do not suffer from the traditional recoil forces associated with conventional expanding gas weapons, this repulsive effect can be equally destructive if not properly compensated for.

 

[katadder]

the energy created is not kinetic in the use of a rail weapon though so there is not going to be recoil, this energy would probably return to the capacitor.
yes that has to be a result from moving something but doesnt mean recoil or movement of the weapon.
consider the magnetic power of something used in a gauss weapon compared to the size of the projectile, if there is any pushback it will be so negligable as to be unnoticed. if you move a magnet towards an iron filing the filing will move away and you will not feel any resistance, the same would apply I am sure to the light weight railgun round compared to the magnetic forces placed upon it, the firer would feel next to no recoil.

 

[iainjcoleman]

the energy created is not kinetic in the use of a rail weapon though so there is not going to be recoil, this energy would probably return to the capacitor.

Of course it's creating kinetic energy. It's making a projectile move at speed. What in the name of Christ do you think kinetic energy is?

Anyway, the issue here is momentum, not energy.

yes that has to be a result from moving something but doesnt mean recoil or movement of the weapon.

Yes it does.

consider the magnetic power of something used in a gauss weapon compared to the size of the projectile, if there is any pushback it will be so negligable as to be unnoticed. if you move a magnet towards an iron filing the filing will move away and you will not feel any resistance, the same would apply I am sure to the light weight railgun round compared to the magnetic forces placed upon it, the firer would feel next to no recoil.

You're fumbling towards something correct here. The recoil momentum of the weapon is equal and opposite to the momentum of the projectile. As momentum p = mv, where m is mass and v is velocity, the velocity of the weapon is given by the velocity of the projectile multiplied by the ratio of the projectile mass to the weapon mass.

Two points to note about this result:

1) it is only really interesting in the context of firing projectiles in free-fall

2) it explicitly depends on precisely the physical argument about conservation of momentum that you have been rejecting for the past few posts.

That'll be £5 please.

 

[katadder]

the energy created is not kinetic in the use of a rail weapon though so there is not going to be recoil, this energy would probably return to the capacitor.

Of course it's creating kinetic energy. It's making a projectile move at speed. What in the name of Christ do you think kinetic energy is?

i did mean no kinetic energy on the weapon, yes there is on the round. the energy put on the weapon is heat and others which has to be bled away in other ways, but this doesnt produce recoil.

 

[iainjcoleman]

the energy created is not kinetic in the use of a rail weapon though so there is not going to be recoil, this energy would probably return to the capacitor.

Of course it's creating kinetic energy. It's making a projectile move at speed. What in the name of Christ do you think kinetic energy is?

i did mean no kinetic energy on the weapon, yes there is on the round. the energy put on the weapon is heat and others which has to be bled away in other ways, but this doesnt produce recoil.

What part of "conservation of momentum" do you not understand?

 

[zozotroll]

Check out any number of current projects on railguns. Look at the effort they take to tie them down so they dont go flying off backwards.

Look at it this way, if it cant puch the gun, then it cant puch the projectile. If it can push the projo, then it can push the gun.

It is not complicated, if you push something one way, it also pushes back in the same amount. The magnet pushes the iron filing because the mass difference is so great you dont note the reaction. Try it with a really big magnet and a shotput, bet you notice that.

Or are you declaring that the laws of physics dont apply to magnets?

 

[katadder]

no try with a really big magnet and a lightweight but tough dart that would be fired down it. thats the same differance as my small magnet and and iron filing. basically you wouldnt feel it. most pressure as pointed out by mhensley is on the 2 opposing rails, pushing apart not back.
not saying the projectile wouldnt have backwards force but this would be against the magnetic field which can be converted into other energy and certainly not enough to effect the firer in any significant way.

consider current rifles - with the speed the round flys out the barrel if all this also went backwards then you would lose your shoulder, however because the round is so much smaller then ii requires alot less pressure so the recoil isnt huge. this is the same with gauss weapons except theres even less backwards pressure because of the way they accelerate the round. the reason that current gauss type weapons are strapped down is not because of massive recoil but to actually keep it steady because even slight recoil would end up with the round going anywhere and something moving that fast you dont want to happen, basically simulating someone holding it, if they could hold something that big.

 

[iainjcoleman]

no try with a really big magnet and a lightweight but tough dart that would be fired down it. thats the same differance as my small magnet and and iron filing. basically you wouldnt feel it. most pressure as pointed out by mhensley is on the 2 opposing rails, pushing apart not back.
not saying the projectile wouldnt have backwards force but this would be against the magnetic field which can be converted into other energy and certainly not enough to effect the firer in any significant way.

consider current rifles - with the speed the round flys out the barrel if all this also went backwards then you would lose your shoulder, however because the round is so much smaller then ii requires alot less pressure so the recoil isnt huge. this is the same with gauss weapons except theres even less backwards pressure because of the way they accelerate the round. the reason that current gauss type weapons are strapped down is not because of massive recoil but to actually keep it steady because even slight recoil would end up with the round going anywhere and something moving that fast you dont want to happen, basically simulating someone holding it, if they could hold something that big.

This is getting silly.

You are deeply confused between energy and momentum. They are different things. Whatever happens to the energy, whatever form it is in, the momentum of the projectile must nevertheless be balanced by the recoil momentum of the weapon.

But that's ultimately a minor point. It doesn't really matter whether or not you understand the workings of a sci-fi gun. What is much more important - for you, at least - is the attitude you take towards learning.

You don't understand physics. You like to talk as if you do, but you don't. Various people who do understand physics have tried, with varying degrees of patience, to explain to you some physical principles that you don't understand. You have remained impervious to this new information, and have insisted on pressing on with your misconceptions.

The world is big and complex. It is full of things you do not yet understand. If this is the attitude you take in general to people trying to explain things to you, you will never ever understand any more of the world than you do right now. And that is a tragic thing in a human being.

I urge you, in all humanity, to abandon this sorry thread. Read up on some physics with an open mind, if you're still interested in how these things work. Or do something else with your time. But, at all costs, seek out new knowledge, welcome new learning, and strive to understand the world a little more each day.

 

[mhensley]

If we assume that the damage done by the projectile is proportional to its kinetic energy, which is a reasonable simplification, then for a given level of damage a faster bullet will have less recoil. This is because recoil is determined by the momentum of the bullet, while damage is determined by kinetic energy.

Ok, if we can safely assume that the gauss rifle's low recoil is due to the small weight of the round, why does it do more damage than a normal rifle? The small bit of reading I've done on guns all point to small, very fast rounds not being that good at doing damage to people. They tend to go right through you and not disrupt a lot of tissue on the way. Usually it's the bigger, slower bullets that do more damage. Example- the 4.6 mm round from the FN P-90 is thought to have very poor stopping power.

 

[atpollard]

I have one thought on reduced recoil for gauss guns vs chemical bullets not based on violation of conservation of momentum.

If I remove the bullet from a cartridge, place my hand over the barrel of the gun and fire just the gunpowder ... I will still 'shoot' a hole in my hand because of the gas shooting out of the gun. The powder (converted to a gas) must also be accelerated out of the gun and must also have momentum and, therefore, recoil.

If I remove the bullet from a gauss-gun, place my hand over the barrel of the gun and fire just the magnetic field ... I will NOT 'shoot' a hole in my hand because of the magnetic field accelerating down the gun. There is no momentum and, therefore, no recoil.

The recoil of the cartridge is based on accelerating both the bullet and the powder. The recoil of the Gauss gun is based on accelerating just the needle.

 

[mhensley]

I don't remember hardly any recoil from shooting blanks from M-16's. Of course, they don't have much recoil to begin with.

 

[zozotroll]

How bullets damage people is a complex and not so well understood area. There are a great many proffesional people for whom this is thier main job, and they dont agree, and argue about it a lot, sometimes rather bitterly.

One school believes that big bullets tearing big holeswill kill or incapacitate best. Most people at least understand this part.

Another school pushes hydrostatic shock. This is where a high speed bullet causes what is known as a temparary wound cavity. That is, as the bullet travels through a person, it causes your insides to stretch for a brief period of time, then go back to how they where, with just a little hole. The idea is that the stretching causes additional damage.

For many years this has gone one. I read about it in collage over 30 years ago. One side or the other gets on top for a bit, but currently it seems the hydro guys are down, and still sinking. Turns out human flesh is pretty elastic, and unless the temp cavity is huge, you are not to bad off, for being shot.

Much of the initial push for high speed darts came from a US artillery round called a beehive. This was used in vietnam, and basicly was a huge shotgun shell that shot flechettes. there are a good number of cases where it was used, and many of the wounds are horrific.

Later research has shown that most of the nasty wounds where not cause by good flechettes, but by ones that where damaged on fireing and tumbleing. The normal straight flying ones just made little bitty holes.

So, likely gauss guns should not cause extra damage. but this is a sci-fi game. Lasers are also not likely to be very good weapons. In fact they mostly suck. But again, what sci-fi game wants to use normal weapons? So lasers and gauss get a big boost. It is tradition for traveler. And in the 1970's, it seemed the way things where going to go. but like so many things, it was wrong. no big deal, still a great game.

 

[zozotroll]

I don't remember hardly any recoil from shooting blanks from M-16's. Of course, they don't have much recoil to begin with.

A big word here is hardly. Even with live rounds a 16 does not kick that hard. And a blank uses less powder, and pushes very little so recoil is very small. But not non-existant.

The heavier something is, and the faster you push it, the more recoil there is. The heavier the gun shooting, the less recoil you feel. But it is still there.

If you dont want recoil, then claim the magic tiny invisble fairys fly the bullets to the target. its your game, and you can do that. but in the real world, whn you push something, you get pushed back. It doesnt matter what does the pushing, if it is gas or a magnet.

Unless you want to rewrite the basic laws for your game you are stuck with that.If your players dont have a highschool level of physics, you can probably get away, with no recoil. Or if they dont care about it, then again no problem. but if you insist that you have a hard science game, and make silly claims like there is no recoil cuz it has magnets and they are to koowl to have recoil, you are likely to get a great deal of disbelief.

 

[Ishmael]

I experimented with a variant of MT where pen was based on muzzle energy and caliber, but that dam was based on bullet momentum. Using a form of AHL's damage table, the pen and how well you hit game a number that you multiplied the dam rating by to get final damage.
I was going by an idea that target damage was based on the energy transfered from the bullet to the target through momentum transfer. It seemed to work okay. It made big bore guns 'feel' more natural ( .54 Hawkins, for example ). Although it really didn't make a huge difference in big slow slugs vs. small faster bullets, the idea made it possible to guage being hit by wrecking balls and buses. ( and melee weapons )

I don't think lasers would be good weapons because I think they'd just cause a flash steam explosion on the skin surface ( still hurts ) vs. burning a hole through a body all quick and neat... but I have nothing to back up that idea. I'll probably just figure damage as an explosion using a percentage of the total beam energy.
Fusion/plasma gun should be a combo of the two.... pen and momentum transfer from the plasma bolt AND a a surface ( sub-dermal?) explosion with a portion of total plasma energy minus the energy associated with the plasma's momentum.

I guess I have too much time on my hands....or at the least, I'm wasting too much time.
oh well...its what games and hobbies are for.