Gauss Weapons - Zero-G?

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NOLATrav
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Gauss Weapons - Zero-G?

Postby NOLATrav » Tue Nov 07, 2017 6:36 am

I've searched the forums but haven't had any luck so...

Curious why gauss weapons do not have the zero-g trait. In all additions back to Classic the weapons are described as using electromagnetic effects to deliver the rounds. No chemical explosion hence no recoil... right?

I suspect at TL12 some sort of dampening mechanism would be trivial to integrate into the weapon to mitigate what must surely be minor recoil, if any. Accelerator weapons (rocket-propelled bullets) do have the zero-g trait so how are they getting their rounds out of the barrel before the rocket booster ignites?

With a nod to 'equal and opposite reaction' I notice that ship-based railguns (also an electromagnetic weapon) do not throw ships off course when firing. I know, much easier to dampen any recoil effects at that scale, computers take it into consideration when offering firing solutions, handwavium in effect, etc.

Just looking at v2 Core, we have lasers and accelerator weapons for zero-g and nothing else. I really want to add gauss weapons to that mix. Curious what others think.

cheers
baithammer
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Re: Gauss Weapons - Zero-G?

Postby baithammer » Tue Nov 07, 2017 8:22 am

Just remember to brace before shooting any recoil based weapons.
Annatar Giftbringer
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Re: Gauss Weapons - Zero-G?

Postby Annatar Giftbringer » Tue Nov 07, 2017 9:30 am

If I remember physics correctly, it goes something like this:
Exploding gunpowder is one way to suffer recoil, but the important part is the law regarding actions and opposite reactions. When one fires a bullet, the gunpowder explodes, turning into hot gas that wishes to rapidly expand. The easiest way to do so is to push the bullet out of the way (through the barrel, towards the target). The recoil the firer feels is the exploding gunpowder 'pushing' against the weapon.

The bullet from a gauss weapon also needs to push against something, it can't just magically gain speed and momentum. Rather than expanding gas pressing backwards, the bullet in a gauss weapon will press against the barrel via magnetic field. One way to reduce the recoil is to lower the velocity of the bullet, so it doesn't need to push as hard to fly away. This will drastically reduce range and damage, though.

Accelerator weapons are (almost) recoilless due to their two-stage launch. The bullet is fired from the rifle with a low-powered charge, just enough to get the projectile free from the weapon. Once in flight, a rocket motor is ignited that pushes the bullet towards its target. The recoil is still there, but suffered by the rocket exhaust rather than the weapon.

Laser weaponry gets around the recoil issue by not throwing any projectile at all.

It would be interesting to see a gauss weapon with zero-g mode - an alternate fire mode with lower damage and range, but zero-g trait.

One way to compensate for the lower damage might be to fire bullets that don't rely only on momentum to cause damage, such as high explosive rounds.

On a related note, would mag-boots suffice to either remove the dex test, or at least provide a boon?
Condottiere
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Re: Gauss Weapons - Zero-G?

Postby Condottiere » Tue Nov 07, 2017 12:53 pm

Slower build up acceleration, but you'd need a longer barrel.
Reynard
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Re: Gauss Weapons - Zero-G?

Postby Reynard » Tue Nov 07, 2017 4:39 pm

Not to be stupid at the moment but does the series of magnetic sources yanking the bullet forward as an action force still create a reaction to the gun? In other words, is the force pulling both the bullet and the barrel?
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Re: Gauss Weapons - Zero-G?

Postby Annatar Giftbringer » Tue Nov 07, 2017 5:03 pm

You could say that, yes. English is not my native language and it was some time since I studied these thing, so I might stumble on the words a bit, but... The magnetic field “wants” to accelerate anything that is placed within it, such as a bullet. Accelerating the bullet means that a counter-force is applied to the rifle. If the rifle is attached to something extremely heavy and sturdy, the rifle won’t move noticeably, but if we on the other hand insert an infinitely heavy bullet into the magnetic field/barrel, then the rifle will fly backwards instead.

Think of it like this: there is a box on the floor. You decide to push it. Your feet have a good grip on the floor and the box is light, so it moves. If the floor is slippery, both you and the box will move. If the box is heavy and the floor slippery, you’ll slide away rather than the box.

How you push the box doesn’t really matter, you could be leaning towards it and pushing with your hands, or use a radio-controlled toy car to push it, same way the bullet can be propelled by gunpowder, magnetic field or a string (bow & arrow).

Something like that, hope it makes sense :)

A longer barrel is one way to lessen recoil while keeping the same damage, as Condottiere said.
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Re: Gauss Weapons - Zero-G?

Postby dragoner » Tue Nov 07, 2017 5:10 pm

Yes, in Newtonian or classical physics, Gauss weapons have recoil; KE=0.5mv^2
NOLATrav
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Re: Gauss Weapons - Zero-G?

Postby NOLATrav » Tue Nov 07, 2017 5:20 pm

Excellent, thank you Team Traveller!

Although disappointed I am happy to be corrected.

I do like the idea of a low-power gauss weapon having the zero-g trait, thank you. I may play around with that a bit.

cheers
Galadrion
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Re: Gauss Weapons - Zero-G?

Postby Galadrion » Tue Nov 07, 2017 5:29 pm

Short answer: unless there is some sort of inertial dampening system or the weapon is firing something massless, there will be recoil.

Accelerator weapons, aka gyrojet guns, get around this problem (as stated by Annatar) by using a low-power charge to get the projectile out of the weapon itself, theoretically causing a recoil small enough to be essentially completely compensated for by recoil suppression systems. The projectile itself picks up most of its velocity (and thus power) by being what amounts to a miniature rocket.

Laser weapons avoid recoil by "firing" (actually, releasing) massless particles, photons, coordinated in such a way as to deliver significant amounts of energy with acceptably low losses. Since recoil is a force, and force equals mass times acceleration, if you're firing something with zero mass you have zero force. It's somewhat of a simplification, but it explains why laser weapons are considered recoilless.

As for why ship-based weaponry (apparently) doesn't take recoil into account: simply put, the recoil forces are negligible in comparison to the other forces involved. After all, you have a firing platform which masses (at the least) in kilotons (if you use earlier editions' estimates of the approximate density of a starship at approximately 15 mass-tons per displacement ton, then a Type A masses around three thousand tons) and which can accelerate at (depending on the ship you're talking about) anywhere from one to six gravities, that is a huge amount of force. For any given platform size of starship, you're just not going to be throwing ordinance with enough force to deflect the ship significantly, certainly not over the length of time of a starship combat round. It's similar to our large warships; a cruiser's heavy guns, if they're firing all-out, certainly generate enough force that the crew notices and even feels the ship reacting a little - but even firing all-out and all in the same direction, the deflection the ship is subject to is easily compensated for at the helm.
Annatar Giftbringer
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Re: Gauss Weapons - Zero-G?

Postby Annatar Giftbringer » Tue Nov 07, 2017 5:36 pm

NOLATrav wrote:
Tue Nov 07, 2017 5:20 pm
I do like the idea of a low-power gauss weapon having the zero-g trait, thank you. I may play around with that a bit.

cheers
Your question’s already got me working on something - hopefully I’ll have something ready to post later tonight :)
Annatar Giftbringer
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Re: Gauss Weapons - Zero-G?

Postby Annatar Giftbringer » Tue Nov 07, 2017 7:30 pm

Ok, so this is a rough draft, I haven’t done any calculations to support the numbers, I’ve just gone for “does this feel kind of ok?” And made stuff up :)

This could be seen as alternate house-rules for gauss weaponry, or it could be variant gauss weapons, alongside the regular ones.

Here goes...

Variable power output: by adjusting the power of the magnetic field, a gauss weapon can control the muzzle velocity of its projectiles, in order to perform optimally under various conditions.

Gauss pistol - zero-G
Range 10
Damage 2D
Traits zero-G, auto 2

Gauss pistol - standard
See central supply catalogue

Gauss pistol - high power
Range 50
Damage 4D
Traits AP 6, bulky



Gauss rifle - zero-G
Range 50
Damage 3D
Traits Zero-G, auto 3

Gauss rifle - standard
See central supply catalogue

Gauss rifle - high power
Range 1,000
Damage 5D
Traits AP 10, bulky



Something like that. Anyways, this is just a rough draft. I’m pondering to perhaps raise the auto value by 1 when firing in zero-G mode and/or not remove auto from high power mode. Rapid-firing in high-power mode might even warrant very bulky and perhaps a mechanic that might lead to overheating or exploding weapons if not allowed to cool between shots...

Thoughts, tweaks and suggestions welcome!
Reynard
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Re: Gauss Weapons - Zero-G?

Postby Reynard » Tue Nov 07, 2017 9:08 pm

I was under the impression gauss guns fired tiny tungsten darts at high or even hyper velocities to impart the impact energy. Wouldn't that help reduce recoil to levels a person without some recoil reduction system could handle?
Galadrion
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Re: Gauss Weapons - Zero-G?

Postby Galadrion » Tue Nov 07, 2017 11:03 pm

Reynard, recoil is determined by muzzle energy, period. It doesn't matter if you're firing great big slugs at a slow velocity or teeny-tiny hypervelocity darts, if the muzzle energy is the same, so is the recoil.
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Re: Gauss Weapons - Zero-G?

Postby AnotherDilbert » Tue Nov 07, 2017 11:57 pm

Isn't recoil a matter of moment, not energy (mv not mv²)? Hence a small, fast projectile would have less recoil for the same muzzle energy?

Basically:
Equal moment: Mw × Vw = - Mp × Vp, where Mw is the mass of the weapon and Vp is the velocity of the projectile.
So, for a given muzzle energy Ep = Mp × Vp², the moment would be Mp × Vp = Ep / Vp.


And a gauss weapon would have less recoil than a firearm with the same muzzle energy (of the projectile) because the recoil determined by the acceleration of both the projectile and any ejected gasses from burning powder?
baithammer
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Re: Gauss Weapons - Zero-G?

Postby baithammer » Wed Nov 08, 2017 12:07 am

As the gauss weapon doesn't use a combustible propellant, the projectile mass is smaller and the energy required is also smaller.
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Re: Gauss Weapons - Zero-G?

Postby AnotherDilbert » Wed Nov 08, 2017 12:37 am

According to wiki perceived recoil is actually the energy imparted to the weapon by equal moment:
Equal moment:
Mw × Vw = - Mp × Vp
or in energy:
Ew / Vw = - Ep / Vp
Hence:
Ew = - Ep × Vw / Vp = Ep × Mp / Mw

So, for a given muzzle energy Ep, the recoil (Ew) is proportional to the mass of the projectile and inversely proportional to the weight of the weapon.

So, a smaller, faster projectile with the same muzzle energy would impart less recoil.
Reynard
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Re: Gauss Weapons - Zero-G?

Postby Reynard » Wed Nov 08, 2017 2:46 am

I was trying to imagine what happens in the barrel of a gauss gun (nothing better to do at work tonight). There's a series of circular coils that line the barrel. The first one tugs the projectile into motion. I picture the coil holds the dart in frictionless suspension. It moves and the coil turns off instantly replaced by the next coil. The dart has inertia from the previous coil and no drag. The next coil turns on accelerating it more and this is repeated numerous times very rapidly. The sum of each tug creates the final velocity. Would the accumulation of momentary magnetic pulses still end up breaking the shooter's shoulder or would they distribute the energy enough over time to reduce the reaction energy?

I just don't have my college physics book nearby.
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Re: Gauss Weapons - Zero-G?

Postby AnotherDilbert » Wed Nov 08, 2017 3:23 am

There is always drag...

I don't think the shooter will feel the pulses even if discrete coils are used to accelerate the projectile.

If we accelerate the projectile to 1000 m/s in a 1 m barrel (at constant acceleration):
v = at, so at₁ = 1000.
d = at²/2, so 1 = at₁ × t₁/2 = 1000t₁/2 ⇒ t₁ = 1/500 s
it would take 0.002 s.
Condottiere
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Re: Gauss Weapons - Zero-G?

Postby Condottiere » Wed Nov 08, 2017 8:38 am

It's usually implied the slug is pushed, as gunpowder traditionally does.

On the other hand, if it's pulled forward like attraction rather than repelled, do you get a forward momentum rather than recoil?
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Re: Gauss Weapons - Zero-G?

Postby Linwood » Wed Nov 08, 2017 11:37 am

There’s also a timing piece. For greatest acceleration I think you’d want the next coil powering up so as to grab the projectile at its peak acceleration from the previous coil. Unless magnetic concerns dictate the projectile has to clear the previous coil.

You could ramp the power on and off to each coil (rather than a square wave) to damp any pulsation effects. Might hurt overall acceleration though.

Would venting the barrel between coils help performance? I’m assuming a barrel is still required to help direct the energy. Or maybe flux rings between each coil?

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