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-   -   ULTRATECH guass weapon system design rules? (http://forums.sjgames.com/showthread.php?t=156351)

hal 03-08-2018 01:49 PM

ULTRATECH guass weapon system design rules?
 
Hello Folks,
Does anyone have a design system they've been using for use with describing the ultratech guass weapons?

Using Doug's spreadsheet formulas - I get a 442.9 grain (28.7 grams) bullet moving at 2650 feet per second, will produce 12d6+0 damage with a 10:1 aspect length (Dart) bullet. The presumption is that the dart is made of a tungsten/Titanium core mixed with lead etc for a rough density comparable to depleted uranium. That works out to a bullet that weights roughly .06 lbs per shot for those who wonder.

As such, using the Ultratech rules for bullet damage, high tech bullets improve the damage from 12d6 to 12d6(2) or 12d6(3) with Armor-Piercing Enhanced Penetrator designation.

If that's the case, what is the energy required as input assuming 25% efficiency (per other threads on Gauss guns and batteries etc)?

Yes, the stats I'm going for mimic the stats in the book, but I wanted to see just what would go into a design system for getting gauss weapons made where one could create the bullet stats first, determine the velocity you wanted the bullet to travel at the muzzle - and then determine how many shots each battery type would enable the user to fire. I'd like to be able to design some alternative diameters other than 7mm for the sniper rifle or the 4mm weapons given in the book. For instance, a 5.56 bullet made not as a dart, but as a simple bullet might be interesting to see what happens. Yes, I'd suspect that the weapon's accuracy might suffer - but then again, it would be interesting the explore the options - something a design system would be NICE if existed.

If necessary, I'll go to GUNS GUNS GUNS design rules - but then use the spreadsheet developed by Doug to determine actual damage values etc.

Question for you out there who know answers...

Is there anything to keep from having a sabot that actively interacts with a barrel as it exits by propulsion via electromagnetic means? In other words, assume you have a sabot whose only purpose is to be comprised of material that allows the magnetic fields to function/grip the bullet. Suppose that plastic were soft enough that it could be forced through the barrel much like a lead bullet is propelled through a conventional fire arm. Could not rifling in a gauss gun barrel, acting upon the sabot material itself - spin the bullet as it exits, and then fall away once it passed the end of the barrel?

Just curious.

If such a concept is viable - it would prove to be interesting in its secondary effects. For instance, anyone who wants to police up their firing vantage point, would need to pick up the sabot halves after the shot is fired. Crime scene investigators might be able to develop forensics that measure the residual magnetic field imprint on the plastic halves - on the presumption that no two gauss rifles/guns leave the same pattern. That's probably NOT a real science issue (after all, if one can "dial a shot" and use variable level power - would that affect magnetic field strengths and such?) But it is sort of interesting to figure out the ramifications of the new technology approaches. Might not the same forensic techniques that work on bullets - also work on the sabot sleeves after they leave the barrel?

Also - if the Chinese Navy gets a working prototype Rail gun for their navy within say, the next five years - does that make their weapon a TL 9 weapon in late TL 8 society, or does it mean that Rail Gun Technology should be deemed a TL 8 innovation, and Gauss guns that are man portable should be considered TL 9?

AlexanderHowl 03-08-2018 02:16 PM

Re: ULTRATECH guass weapon system design rules?
 
You actually need to use a bronze sabot around a nickel steel bullet with a tungsten core. Bronze possesses the lowest friction coefficient of any metal and possesses the third highest heat capacity of any common metallic alloy. Tungsten possesses a relatively high friction coefficient and possesses a relatively low heat capacity, meaning that tungsten will actually vaporize in a gauss weapon before bronze even softens.

Depending on the design of the projectile, the sabot should be designed to not separate until impact (which is different than normal sabots) in order to prevent the bullet from melting in the air. When the projectile hits, the bronze sabot will peel away while the nickel steel bullet will crack the armor of the target. The tungsten core will then perforate the structure of the target.

Humabout 03-08-2018 03:02 PM

Re: ULTRATECH guass weapon system design rules?
 
Honestly, you probably don't want a sabot if you can avoid contact with the rails in a railgun; you could just make the rails helical and use a maglev-type configuration to float the projectile in the weapon. Current could be transmitted by plasma (this is one layout, minus the helical rails, that has been proposed for railguns).

For coil guns, you can just use the magnetic field itself to impart a spin on the projectile. This, again, is probably more efficient than a sabot because you are not losing a ton of energy to friction and you don't have to contend with the heat buildup in the gun, either. After all, circuits generally don't like heat.

More efficient than either of these is using a fin-stabilized projectile, or if the round is large enough, an actively-stabilized and possibly guided projectile. If you don't like fins, a lot of current research is being done in the use of piezoelectric and memory-materials to create deformable control surfaces for everything from entry vehicle heat shields to airplane wings that deform instead of having control surfaces. This could be extended to the surface of a projectile, if miniaturized (which, frankly, is probably easier than making an airliner's wing deform)

With all of that said, this is ultra-tech, so you can really just make up whatever material you want. Some bioferrous smoothium-balongite nanocomposite discarded sabot totally works if you need to justify it!

AlexanderHowl 03-08-2018 04:36 PM

Re: ULTRATECH guass weapon system design rules?
 
It is almost impossible to avoid contact with the rails though, at least in any man portable system, as your weapon can only be so large. Bronze is just a nice logical solution.

Minuteman37 03-08-2018 07:23 PM

Re: ULTRATECH guass weapon system design rules?
 
Excuse my ignorance if this comes off as totally off base, I'm a layman through and through, but do you really need bronze and depleted uranium approximating alloys for effective manportible gauss weaponry?

I understand the desire for the optimal weapon, but this doesn't seem to address longistics and price points for a consumer market.

Refplace 03-08-2018 07:43 PM

Re: ULTRATECH guass weapon system design rules?
 
Rahleu? Had some on his blog.

AlexanderHowl 03-08-2018 08:41 PM

Re: ULTRATECH guass weapon system design rules?
 
Bronze is essential for man-portable systems or else the heat from the friction will broil the user around the same time that it melts the barrel. Depleted uranium is unnecessary with a tungsten core. If you do not care about penetration, you can just use a bronze sabot around a nickel steel bullet (probably (2) rather than (3) armor penetration).

Minuteman37 03-08-2018 10:39 PM

Re: ULTRATECH guass weapon system design rules?
 
Quote:

Originally Posted by AlexanderHowl (Post 2164010)
Bronze is essential for man-portable systems or else the heat from the friction will broil the user around the same time that it melts the barrel. Depleted uranium is unnecessary with a tungsten core. If you do not care about penetration, you can just use a bronze sabot around a nickel steel bullet (probably (2) rather than (3) armor penetration).

Does Bronze posses the ideal characteristics to not melt the gun or are their better, but much more expensive options?

AlexanderHowl 03-08-2018 11:46 PM

Re: ULTRATECH guass weapon system design rules?
 
Bronze possesses the lowest friction coefficient of any metallic alloy so, when combined with its relatively high (for a metal) specific heat, it ends up winning the prize. It also radiates heat much faster than the majority of metal alloys, so you do not have as much heat retention as with other materials (so the physical armature should be made of bronze as well, though the magnetics have to be behind the armature). Now, with larger weapons, you can avoid contact with the rails, so you can use more effecient processes and get to higher velocities, but I think that you are going to be using a lot of bronze for man-portable systems.

Humabout 03-09-2018 07:21 AM

Re: ULTRATECH guass weapon system design rules?
 
Quote:

Originally Posted by Minuteman37 (Post 2164039)
Does Bronze posses the ideal characteristics to not melt the gun or are their better, but much more expensive options?

It's worth noting that specific heat isn't the only - or necessarily the most important - factor. Heat doesn't transfer in bulk instantaneously, so you should really be at least as concerned with the heat resistance of the material. This is inversely proportional to a material's heat conductivity, k. Furthermore, the contact time in the weapon should be excruciatingly small if the gun is reasonably sized and functional. So even if the heat tranfer rate is high, the time of transfer in the gun is similarly small. All in all, there is a very good chance that you really don't need - or necessarily want.

For comparison, bronze has a thermal conductivity of 16 W/m-K Titanium ranges between 19 and 23; carbide ceramics can be as low as 0.65, and silica aerogel (not suitable for other reasons) is only 0.017.

AlexanderHowl 03-09-2018 08:18 AM

Re: ULTRATECH guass weapon system design rules?
 
Titanium possesses a higher friction coefficient and a lower heat capacity though, and it burns in an oxygen atmosphere. At the energy levels of a man portable railgun, a titanium armature will ignite. Of course, you can have titanium as the support structure, just as long as it does not contact the round you should be fine (a railgun made from bronze and titanium would actually be quite beautiful).

Fred Brackin 03-09-2018 08:46 AM

Re: ULTRATECH guass weapon system design rules?
 
Quote:

Originally Posted by hal (Post 2163948)
Hello Folks,
Does anyone have a design system they've been using for use with describing the ultratech guass weapons?

Using Doug's spreadsheet formulas - I get a 442.9 grain (28.7 grams) bullet moving at 2650 feet per second,

Note that contrary to much of the later posts at this quite modest performance regime railguns that are in danger of melting themselves are not necessary. It wouldn't be that hard to achieve with cordite much less more modern powders.

For this ballistic profile I would expect instead of railguns that a "contactless coilgun" would be used instead. Such a weapon has no friction issues.

Or propellant issues either. Much of the fire and fury seen in prototype railguns comes from the plasma arc that travels along the rails and pushes the projectile forward.

The advantages of the coilgun over a conventional chemical propellant weapon of similar output would be the relative lack of thermal signature and less recoil due to no mass of propellant gasses. 30-40% less recoil.

A sabot might be useful if the actual projectile is poorly conductive but that sabot itself would be chosen for electrical conductivity. Plastics are improbable.

Any field-ready EM gun would be TL9. We are very close (probably) to the end of TL8 and no one has a deployable weapon yet. I have no idea why a Chinese version would be definitive. They are generally several years behind the Western defense/aerospace establishment in any area except press releases.

DouglasCole 03-09-2018 11:48 AM

Re: ULTRATECH guass weapon system design rules?
 
Quote:

Originally Posted by Fred Brackin (Post 2164103)
Note that contrary to much of the later posts at this quite modest performance regime railguns that are in danger of melting themselves are not necessary. It wouldn't be that hard to achieve with cordite much less more modern powders.

This is a 15% velocity boost on a .416 Rigby cartridge, for example. One could probably work up this load in a jiffy and maybe not even break anything. Well, except maybe your shoulder.

hal 03-09-2018 01:15 PM

Re: ULTRATECH guass weapon system design rules?
 
Some of what I'm reading is that the energy required to send the projectile moving isn't 100% efficient. In other posts, I think I came across the figure that David Pulver was using 25% efficient. So, if the figure (say, 400 joules) were to be required to get a projectile moving, presumably, the applied energy is closer to 1600 joules - no?

If so, what happens to the remaining 1200 joules applied to the process?

If the projectile is jacketed Tungsten or depleted uranium for instance, then you'd get the mass with the relatively small volume. If using a dart form, then you're dealing with out having to spin the projectile for stability purposes. Right now, I'm just trying to keep things reasonable so that anything that I want to use in game, has some reasonable structure behind it. What I miss the most about the GURPS VEHICLES 2nd edition rules were the weapon design rules. If I'm going to have gauss pistols, or gauss submachine guns, or what have you - I'd like to be able to craft something that makes sense.

Back when I created stats for the Cohen Battle Tank, using a rail gun cannon system, I also created battle suits along with a battle suit taxi (think battle taxi but for battle suits) along with what I called the integrated combat team system.

Long story short - the tank contained the main battle computer, and was a network node for all of the battlesuits assigned to work with the tank as a team. The gatling gauss and the Heavy Automatic Gauss Gun (HAGG) had definite roles in the concept, and it was FUN designing the weapon systems for what I called the Narco-Terrorist War set in Columbia in the near future.

Problem is - there has never been any real conversion system between the older "Classic" GURPS and the newer 4e GURPS. The design system modifications are all ad-hoc with no real foundation one way or another.

Now Doug did write the Pyramid Article Interior and Terminal Ballistics for GURPS a while back (back in 2002). He also provided us all with his spreadsheet for estimating damages for weapons based on actual physical world data. So, there seems to be little reason not to try and determine the following:

How much energy from a power cell is required to send a round flying towards its target (that determines how many shots per cell is required). There is nothing to keep us from determining how fast the projectile is travelling (Muzzle velocity) nor diameter of bullet nor its mass.

In reality? The only thing missing from the design sequence is how much material goes into the rest of the gun proper, and how much it costs.

So, if we're really talking about a weapon that requires roughly four times the actual energy in joules produced by the gun's handling characteristics - then knowing the muzzle velocity in joules for a 5mm round with a given mass - let's us say how many shots from what power cell, how much damage it does, half damage range, max damage range etc. Determining acc or recoil or what have you seems to be the other "seat of the pants" stuff or ad-hoc stuff that I wish didn't have to be pulled out of thin air. Then again? Until we see the vehicle design system, or a weapons design system comparable to what I'm seeing for armor design - but for weapons, we'll just never have those tools.

:(

Maybe the Vehicle Design System will never see the light of day. If so, then those of us who want a little more differentiation in weapons are either going to give up or make up their own system. Before GURPS HIGH TECH firs edition came out, I remember using the AFTERMATH! system for gun design. It worked out ok, but I liked it even better when GURPS VEHICLES 2nd edition came out. ;)

On that note... I'll catch you guys a bit later.

Anthony 03-09-2018 01:23 PM

Re: ULTRATECH guass weapon system design rules?
 
Quote:

Originally Posted by hal (Post 2164161)
Some of what I'm reading is that the energy required to send the projectile moving isn't 100% efficient. In other posts, I think I came across the figure that David Pulver was using 25% efficient.

I don't think an efficiency number has ever been given for gauss weapons (and 25% seems low), but it's a realistic estimate for conventional firearms.
Quote:

Originally Posted by hal (Post 2164161)
If so, what happens to the remaining 1200 joules applied to the process?

Heat, noise, escaping propellant (for conventional guns), escaping magnetic pulse (for EM guns). A tiny amount (usually less than 1%) goes into recoil.

starslayer 03-09-2018 02:25 PM

Re: ULTRATECH guass weapon system design rules?
 
An important thing to consider in this discussion:

Gauss != Rail.

A railgun (so called because of the linear rails) accelerates due to lorentez force, you put a tremendous difference of voltage on rail A and Rail B, and the arcing through the projectile causes the projectile to move forward. Much like how in a jacob's ladder the arc will happily climb up between the two antennas, but much faster and carrying a projectile.

You radically increase efficiency by shortening the arc distance required, so ideally you want the projectile touching the rails, and this actually reduces heat (open arcs = arc welder running on the inside of your railgun). Using any kind of sleeve or sabot would be bad as most low friction materials are also high insulating (teflon, etc), and you want to encourage the arc, not resist it. Bronze is about as close to ideal as possible because it has a low friction coefficient, is soft, AND is conductive.


In a gauss weapon you are using multiple magnetic rings to accelerate your projectile, each ring pulls the object one more 'click' forward until it exits the barrel. Closer is better for magnetic transference, but the ultimate loss from having an air gap is actually quite minimal. You can also use an ultra low friction sleeve or sabot (or both) on the projectile, as long as the magnetic force (gauss) can reach the projectile all is well. As a downside you need VERY sophisticated electronic controls to manage the magnetic activation. An ideal gauss weapon would balance the magnetic forces to actually levitate the projectile in a tiny air gap in the middle of the barrel.

Humabout 03-09-2018 04:16 PM

Re: ULTRATECH guass weapon system design rules?
 
Quote:

Originally Posted by AlexanderHowl (Post 2164099)
Titanium possesses a higher friction coefficient and a lower heat capacity though, and it burns in an oxygen atmosphere. At the energy levels of a man portable railgun, a titanium armature will ignite. Of course, you can have titanium as the support structure, just as long as it does not contact the round you should be fine (a railgun made from bronze and titanium would actually be quite beautiful).

There is no reason to use a metal at all. Titanium was simply listed as one of many materials that have lower thermal conductivity than bronze. Personally, i'd look at ferromagnetic ceramics.

AlexanderHowl 03-09-2018 04:24 PM

Re: ULTRATECH guass weapon system design rules?
 
1200 J is not a lot of energy though (three hundred milligrams of sugar possesses that much chemical energy). If you are talking about a 25% efficiency, that means the projectile possesses on 400 J, which is less than the energy of a 9mm. If you want a powerful weapon, the equivalent of a .50 BMG, you need a minimum of 18,000 J, which would mean that you would have 54,000 J of wasted energy at 25% efficient (you could actually reach 50% efficiency using a bronze railgun due to the low friction coefficient, though you would still have to deal with 18,000 J of wasted energy).

If we assume a 25% efficiency though and that 2/3 of the waste energy is heat from friction, that ends up being 36,000 J of heat for a .50 BMG equivalent (18,000 J for the bullet and 18,000 J for the armature). The problem is that the heat is being created on the magnetic armature, and the armature will lose magnetism if is not allowed to cool down. A 2 kilogram armature with a generic specific heat of 450 J/K/kg will heat up by 20 K every shot, meaning that you will lose magnetism within a few shots if you fire more than once every few seconds (using the same assumptions, the 50 gram bullet will gain 800 K).

Rupert 03-09-2018 06:10 PM

Re: ULTRATECH guass weapon system design rules?
 
Quote:

Originally Posted by DouglasCole (Post 2164139)
This is a 15% velocity boost on a .416 Rigby cartridge, for example. One could probably work up this load in a jiffy and maybe not even break anything. Well, except maybe your shoulder.

It's only 6% more energetic than a standard .416 Weatherby Magnum load. A .460 Weatherby would out-recoil it quite handily.

starslayer 03-09-2018 06:25 PM

Re: ULTRATECH guass weapon system design rules?
 
Quote:

Originally Posted by AlexanderHowl (Post 2164217)
1200 J is not a lot of energy though (three hundred milligrams of sugar possesses that much chemical energy). If you are talking about a 25% efficiency, that means the projectile possesses on 400 J, which is less than the energy of a 9mm. If you want a powerful weapon, the equivalent of a .50 BMG, you need a minimum of 18,000 J, which would mean that you would have 54,000 J of wasted energy at 25% efficient (you could actually reach 50% efficiency using a bronze railgun due to the low friction coefficient, though you would still have to deal with 18,000 J of wasted energy).

If we assume a 25% efficiency though and that 2/3 of the waste energy is heat from friction, that ends up being 36,000 J of heat for a .50 BMG equivalent (18,000 J for the bullet and 18,000 J for the armature). The problem is that the heat is being created on the magnetic armature, and the armature will lose magnetism if is not allowed to cool down. A 2 kilogram armature with a generic specific heat of 450 J/K/kg will heat up by 20 K every shot, meaning that you will lose magnetism within a few shots if you fire more than once every few seconds (using the same assumptions, the 50 gram bullet will gain 800 K).

This is not quite as horrible as it seems on the surface

This is only if the armatures have no:
Active cooling
Heat sinking
Other methods for dealing with heat.

Further as the barrel heats up the more heat that the projectile will absorbe.

Again we are getting gauss and rail confused as the 'same type of weapon'. Rail won't care if it heats up enough to loose magnetic coefficiency, it propels via lorentez force, not inherit magnetisim (It will care that resistance increases, but that is an entirely different temperature scale that will allow a much more significant temperature delta for faster radiation, of course being that amateur science projects can melt copper rails in a lab setting using no more than wall power and some capacitors that may be moot.).

Gauss by comparison will actually IMPROVE in efficiency as the coils heat up (It is unlikely that any sort of gauss weapon will use permanent magnets since the goal is to selectively subject the projectile to magnetic force then turn it off, 'toy' gauss gun demonstrations today that use permanent magnets do so because the software for electromagnet control is really hard to get right).[1]

[1] https://www.omicsonline.org/open-acc....php?aid=75409

tanksoldier 03-10-2018 03:23 PM

Re: ULTRATECH guass weapon system design rules?
 
Quote:

Bronze possesses the lowest friction coefficient of any metallic alloy so,
There probably a ceramic that would do both better.

hal 03-10-2018 03:52 PM

Re: ULTRATECH guass weapon system design rules?
 
So I played around with GUNS! GUNS! GUNS! to create what I hoped would be a good analog example of the 7mm Sniper gauss rifle. I used GGG tech level 14, which is analogous to 2200 AD give or take.

The design goal was to attain 13d6+1 damage using a 10:1 length/diameter aspect (ie a fin stabilized dart).

Net result?

Semi-automatic Rifle, firing a 7mm steel dart, weighing 281.33 grains (18.23 grams)
Muzzle velocity: 3613.71 feet per second (1101.46 meters per second)
Damage 13d6+1
1/2 damage range (yds): 1746
Max Range (yds): 11428
Muzzle Energy: 11,000 Joules

uses 31,900 joules per shot. Magazine battery holds 319,000 joules for a total of 10 shots. Magazine itself holds both the battery and 10 rounds.

1/2 damage: 1746 Max Range: 11428

Base weight: 16.39 lbs
Weight without magazine: 15.03 lbs

Cost in "credits" per GGG: 3,160

Contrast this with the Gauss Sniper Railgun in GURPS ULTRATECH page 142 at $18,000, weighing 20 lbs, RoF 1, damage 6d*2(3) 1/2 damage 2400, max range 10,000 yards.

Yes, both systems produce different results to be sure. The difference being, the one system has a design sequence that can be followed to create different caliber weapons - while the other one we can't modify or use to our heart's content.

Note that I did not strictly use the GGG's damage conversion rules or the 1/2 damage rules etc. Those I got strictly using the spreadsheet from Doug Cole where the bullet weight, muzzle velocity, aspect ratio and bullet diameter is all that is required to determine damage, 1/2 damage range, max range, etc. What I used the GGG rules for was the physical aspects of the gun itself. I think the next thing to do is determine what the GURPS Powercell stats would be in the GGG set up and work from there.

I'm still working on Accuracy values for the weapons, but in GGG, the author used the following categories for his range classes, they should be a good fit for GURPS somewhere along the way...

Snub-nosed pistols

Pistols

Carbines

Rifles (maximum for shoulder-fired)

Light cannon (small autocannon)

Medium cannon (tank guns)

Heavy cannon (artillery)

Superheavy cannon (siege guns)


Still more work to go to be sure, but at least it seems like it might work.


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