sub9 released

[Uncle_Rand]

Instead of metaphased shields, why not just have Jason devise a phased ship. Like in that Star Trek Voyager episode where the crew was being experimented on by beings that were out of phase with our reality? Then he wouldn't even have to worry about being fired on, as they would never see him. Or did someone already cover this, and I missed it?

Uncle Rand

[Shadowhawk]

About avoiding Faey gravitation(al) detectors: there is and idea for Faster Than Light (FTL) travel, that the ship should be surrounded by "bubble" of space with some exotic properties. What about using some kond of "bubble" around the ship, which smoothes the gravitational waves. If you cannd hide completely, you can at least diffuse image and make it harder to spot. Think camouflage.

[Lochar]

It would be fun, but it wouldn't be possible. There is such small thing like the laws of physics: conservation of momentum and conservation of energy. You have to take some energy for recoil absorber. And what is most impurtant third law of Newton: action equals reaction.

Since the Faey seemed to have a better grip on things than we do, how about the bubble of space that their plasma runs through?  Could you channel the recoil into a space something like that?  The recoil wouldn't be a problem then, and you might be able to send it around into the projectile, or use the energy in some other way.

I don't know how feasible this all is, I'm stretching waaay out of my boundries for this. LOL

[Shadowhawk]

I have thought about rail driver/gauss rifle, it's recoil and laws of physics.

• Is the recoil absorber really needed? In ordinary rifle there is in the moment of shoot impulse force which propels bullet thru the barrel, and the butt of the gun into the shooter. In the gauss rifle/cannon the bullet/projectile is accelerated in the length of the barrel. So I think that the force is not so sharp, and the impulse can be lower even though the velocity of bullet is higher. BTW. how heavy the bullet is, how fast it is and how long the barrel is?
• How to make recoil absorber in gauss rifle? In ordinary rifle the gasses after the bullet leave the barrel "jerks" the gun away from shooter, if I am not mistaken. How to do something like that in the gauss rifle?

Well, one can always use some buzzwords (e.g. inertia control, recoil adsorber)... but it is not what I want...

[Finn]

Now my grasp of physics may be somewhat weak, but I'm thinking that the way the gauss gun accelerates the projectile along the barrel, and doesn't force the bullet out, the recoil would be a whole lot less, due to the fact that it isn't actually using any pressure against the barrel to overcome the inertia of the bullet? By the time the projectile has reached the end of the barrel, it's travelling fast enough not to affect the gun itself the way a bullet would...

Like Shadowhawk said, the gun works on gases expanding within the barrel forcing the bullet out, causing force in both directions (thus the kickback), for a bullet smoothly accelerated, there wouldn't be that force backwards (unless the projectile was particularly dense)

There would be some foldback somewhat since holding the barrel steady against a lateral force would produce some level of kickback, but a gyroscope in the gun could help with that, although, at the speed the projectile is fired, it may be a moot point...

[Hallmist]

*Engineering Geek Mode ON*

Ok, so I'm going to try to stay as non technical as possible for all of our sakes, but here's recoil as I seem to remember it from my phisics classes.

Every object has a property called momentum, which is mass*velocity (mass times velocity).  In any collision or reaction, momentum is conserved.  So if both objects have the same momentum beforehand, then they will have the same momentum afterwards.

So, enough with technical speak, what does this actually mean?  Well, if we say that both the gun and the bullet are not moving (velocity of both = zero) before it is fired, then after it is fired, the bullet is moving very fast, and the gun is still sitting there.  MOSTLY.  But the momentum of the bullet is still equal to the momentum of the gun (just in different directions)

So the bullet flies out from the gun very fast (since it has very little mass) and the gun just jerks a little bit (since it has a lot of mass) , but if you multiply, you'll get the same numbers.  For a normal (combustion) rifle, the bullet flies out close to the speed of sound (or slightly over it), and the gun jerks back into the shooter's shoulder.  For the railgun this jerk-back would dislocate, if not completely remove (ouch), the shooter's shoulder; due to the extreme velocity of the round.

One other point, even though the propulsion in the railgun is due to magnetism, rather than expanding gasses, Newton's third law (every action has an equal an opposite reaction) is still in effect.  The magnetic coils create a force on the round, but they are also forced backwards by the round.  So you'd still need a recoil absorption system.

*Engineering Geek Mode OFF*

Now for those of you brave enough to read through that, I first thank you, and then apologize.  :)

[straechav]

This is by now rather interesting thread. Incidentally, I decided to see what kind of rail/gauss gun theories you might find online and I stumbled upon this site (not difficult to find, by any means, though):

http://www.powerlabs.org/index.html

Heh. There is actually someone trying to build a railgun, and not the kind that's been built before (which is about the size of a truck). Which is interesting to say at the least. But when I kept reading the specs, I got a nasty surprise. 100,000 ampers just to propel the projectile? Shit! Anyone has any idea how much power that is?

Another interesting revelation was that the projectile should be actually moving PRIOR the magnetic pulse, since otherwise the high amounts of electricity involved would instantly render the railgun as highly complex spot welder...

Another fun thing was the three videos of the muzzle flare (yes, you read right), the flare is actually a spray of plasma that the gun shot...

Check it out. It is interesting, even if the technical specs and such are a bit vague. I don' think this contributes whole lot to the conversation, but I found it interesting.

Neither I am sure if anyone else has posted the link, but hey, there you go. I am too lazy sonofabitch to read the beginning of the thread once again.

[Shadowhawk]

The momentum conservation is important, but I think what is more important is the force acting on gun and shooter, i.e. the momentum change divided by time, or rather dp/dt (p - momentum, t - time).

So it might be while the velocity and the momentum is larger for rail driver, so is the time of accelerating the bullet/projectile.

BTW. is Jason's gun rail driver or gauss (coil) rifle?

[Forbidder]

For all you people who rather not see equations and physics and math, please ignore my message, I'm just a math/physics nut, so I can't help it that I think in these terms/equations.

Ok I did note the physics momentum of the rail gun slug = impulse the rail gun imparted on the slug = force rail gun applied to slug times the duration of time the force was applied.

massXvelocity = momentum = impulse= force X time

gun, short time big force, large kick back.
rail gun, more time, less force less kick back.

But then I began thinking about how Jason's slugs had enough kinetic energy to blast holes in mountains.  And I'm thinking, where is all that momentum coming from?

because that kinetic energy = mass X velocity X velocity.

Now take all that into account and you wonder if that time is long enough for the force to be small enough not to send Jason flying backwards.  Thats what I was thinking all that time I sat with the compose message screen until I decided to accept the recoil absorber idea as a perfect solution.

And now I attempted to calculate the stuff some from data given by Fel in the story, some from guesses I had to make, here is my results:

(STORY)"14730 miles per hour" velocity of slug = 6585.204 meters/second
to recharge and reload = 0.5 seconds to fire

[slug]
(STORY)"0.22 caliber" = 0.002794 meters radius
(GUESS) 2 inch long slug
(CALC)volume 0.00000124585 m^3
(WEB)Density of steel = 7850 kg/m^3
I'm neglecting the titanium because it is such a thin layer.
(CALC)mass = 0.009779936732101807 kg

(CALC)impulse of slug = 64.402878487983747863628 kg m/s
slug impulse = impulse of rail gun without absorbers
(WEB)impulse of some average rifles today = 22.120792 kg m/s


KE of slug = 424,106.09303 Joules
4.184E9 joules in 1 ton of TNT
So the rail gun slug would have a blast of about 0.2 pound of TNT when it hits.  That is quite some blast, I think, it's like around stick of dynamite going off whereever the slug hits.

I have the feeling that Fel also did some calculations which he hasn't shown us.  And a lot of my calculations depend on the mass of the slug, which depends on the length which I guessed to be 2 inches.

But it sorta gives you an idea of the proportions of the weapon.  Of course if I have made any mistakes which is very likely as I am half asleep, please tell me.  I like having a perspective on the magnatude of power the rail gun would produce.

I'm going to check out that rail gun link now

[Forbidder]

• How to make recoil absorber in gauss rifle? In ordinary rifle the gasses after the bullet leave the barrel "jerks" the gun away from shooter, if I am not mistaken. How to do something like that in the gauss rifle?

So as you said ordinary guns have recoil absorbers vent gases ventrally so it won't add to the recoil.

But for a rail gun there is no gases.

I can imagine up multi stage spring loaded chambers where it would recoil back as the slug is shot out, and over time return to it's original position.  This is bad, it's slow, it cuts your impulse on your slug by half, but you would get a lot of reduction I think.

I can also imagine a reverse firing rail gun balancing the forward fireing one.  But you then have the problem of making sure the backwards one doesn't hit anything important.

In short, you can't use a mass driven technique in Jason's case because his rail gun doesn't eject backwards mass.

So no we need to look at "fictional" methods.  Perhaps useing parts of the technology that moves his ship.  We know his ship does not expel gasses or move air in order to thrust itself.  It's based on a gravity drive.

So with this gravity drive technology, you only need to create a large pushing gravity behind while you are accelerating the slug forward.  The onboard computer can control how much gravity and when the system should be on.  That would be my guess how Jason did it, but there are many other possible ways, perhaps the gun uses another set of magnetic coils to push off the megnetic fields around it?  So the gun is pushing against eath's magnetic field as it shoots the slug.

You're imagination is the only limit

[Greymist]

Thanks for the numbers Forbidder, I couldn't be bothered doing it myself but it's nice to know/

The gun is actually a coil gun, it has been mentioned in the story that coils are wrapped around the barrel to generate the EM pulse, not rails that a slug touches to complete the circuit *insert stuff about rail guns here*

A bit about the recoil, the recoil for a coil gun is specifically in relation to the coils, they're what is being pushed backwards and it has been said that they're hard mounted to the barrel, hence the whole unit gets pushed backwards.

perhaps the gun uses another set of magnetic coils to push off the megnetic fields around it?  So the gun is pushing against eath's magnetic field as it shoots the slug

I did think about something like that myself, but the magnetic field the other set of coils produces would screw with the fields the firing coils produced generally messing things up.

I did think of one other solution which breaks the laws of physics as we know them but hey, the reason the coils on current coil guns are pushed back is because they react to the EM field they create, I know this will sound like crazy **** but if the coils Jason uses can somehow produce an EM field but be non conductors they wouldn't be effected by the field......still how something goes about producing a magnetic field when it's a non conductor I don't know.

[Hearly]

I've always considered the "rail gun" to be more like a Particle Accelerator vs a true Rail gun, If I remeber correctly a rail gun works by using a gas to move the mass at high speeds, while Magnetic driven stuff is normally used in Particle Accelerators.

[Shadowhawk]

I've always considered the "rail gun" to be more like a Particle Accelerator vs a true Rail gun, If I remeber correctly a rail gun works by using a gas to move the mass at high speeds, while Magnetic driven stuff is normally used in Particle Accelerators.

See the link mentioned here, http://www.powerlabs.org/railgun.htm, or just searcg Google for "Rail Launcher", "Rail Gun", "Gauss Rifle" or "Coil Gun".

To put things simple, Coul Gun (Gauss Rifle) works using coils as electromagnets to propel metal bullet, using magnetic force to accelerate the bullet. Rail Launcher takes advantage of the fact that two wires with antiparallel current repels each other, wanting the area of circuit grow; if one of the wires is the bullet/projectile it gets accelerated. The linear particle accelerators (linacs) works similarly to coil gun, but there are capacitators instead of coils and electrostatic force instead of magnetic one accelerating e.g. electrons. Some elmag rifles may use gas as pre-propellant (see e.g. the rail launcher mentioned in the link).

[Forbidder]

Yeah now that I know what the difference between a rail gun and guass rifle is, I would definately call Jason's gun a Guass rifle.  For a Rail gun would either cause the slug to melt into a heap of plasma each time it was shot out because the slug would be connecting very high currents together, or it would melt the two prongs of the rail gun.  Jason's gun doesn't seem to experience any extreme temperatures, and seem to have components for magnetic fields.

As for Jason calling it a rail gun it could be because he didn't feel like explaining what a Guass rifle is to everyone who bothered to ask, as many people have probably heard about rail guns.

As for the recoil absorbtion,  all he would need would be a secondary coil further back maybe in the stock of the gun to produce the exact opposite fields of the primary coil.  Given that the recoil from guass rifiles is from the magnetic fields acting on the coils themselves, and not from the mass being expelled because there is no mass to mass contact.  The secondary coils would need to be identical in conductive properties and mass as the primary ones to produce a near exact counter force while the gun launches the slug.  And since magnetic  fields are very inverse R squared in their field strength, enough distance but physically mounted on the same frame which is study enough, should make the Guass rifle have near zero recoil and yet unaffect the slug that is being launched...

[Shadowhawk]

One can avoid small amount of recoil by allowing the coils to go back a little (on springs or something like that). Unfortunately, this removes some of the power from rifle. Secondary coil used for recoil absorbtion would not do: please remember that this second coil would act on bullet as well, slowing it considerably.

I think one can avoid some of plasma/discharge flash in rail gun by turning off the current before the bullet flies from the rails/barrel.

BTW. I'd like to have info from Fel on the approximate mass of the bullet/projectile in Jason's Gauss rifle (called rail launcher).