ULTRATECH guass weapon system design rules?

[hal]

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]

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]

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]

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]

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]

Rahleu? Had some on his blog.

[Fred Brackin]

Originally Posted by hal

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]

Originally Posted by Fred Brackin

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]

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]

Originally Posted by hal

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.

Originally Posted by hal

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.