Anime: Railgun
 

I've picked up a new anime "Railgun" about psi(mutant?) powered individuals. Young girls, naturally....

The top psi is an electro-controller nicknamed "Railgun" for her signature ability. She controls electric fields (static and flowing) around her body, and is able to fire off coins at 1024 m/s.

First, is this actually possible (using tech, of course) firing projectiles just through manipulation of electric fields?

Second, how should this be modeled in GURPS? (3e AND 4e)

Re: Anime: Railgun
 

Every electric field has a magnetic field of equivalent strength perpendicular to it.

So if she can make electricity flow around her body, she must be able to make magnetism do the same.

Re: Anime: Railgun
 

When I allowed creation of a character with a similar ability, I based it on his control of magnetic rather than electric fields; that's what real world designs for railguns use. Of course you can set up a moving electric field and generate a magnetic field, per James Clark Maxwell.

Doing it this way, you'd need projectiles made of ferrous metal.

In principle, you could repel small objects electrostatically, but you'd need an opposite charge somewhere, which might attract them. I suppose you could psionically put the opposite charge on your target! Electrostatic repulsion isn't all that powerful; I'd have to dig out Halliday and Resnick to check the equation.

Bill Stoddard

Re: Anime: Railgun
 

Only every changing electric field. A static field has no magnetic effects.

Bill Stoddard

Re: Anime: Railgun
 

Hence the word "flow".

Re: Anime: Railgun
 

There's a fair amount of bad physics in A Certain Scientific Railgun (for example, a coin at 1024 m/s is actually rather underwhelming), but it is certainly possible to accelerate metal objects with electromagnetic effects.

Re: Anime: Railgun
 

I can't answer much for 3rd edition, since I'm no longer using it and don't have the books handy. Might be possible with the Psionics rules, either with Electrokinesis or by adapting Telekinesis.

In 4e, there are a couple ways to handle it. The most literal is with Telekinesis limited to only apply to ferrous objects. You then use your TK strength to "throw" the object. That can get complicated rules-wise though, so I'd recommend building the "throw" as a separate Innate Attack, an Alternative Ability to the Telekinesis. For more details on building these sorts of powers, and a plethora of ready-made examples, I'd recommend picking up Psionic Powers. The Powers book itself would also be helpful.

Re: Anime: Railgun
 

why? bullets 400–475 m/s, with a bullet weight of ~16–22 grams

of course the heaviest Japanese coin is 500yen Nickel-brass Coin

Material : Cu72%, Zn20%, Ni8%
Diameter : 26.5mm Weight : 7.0g
Edge : Milled
Year of First Issue : 2000

the lightest 1yen Aluminum Coin

Material: Al100%
Diameter: 20.0mm Weight: 1.0g
Edge: Smooth
Year of First Issue: 1955

however speed has a bigger impact the mass.

Re: Anime: Railgun
 

For a bullet, you're looking at a minimum of 6.4 kg-m/sec linear momentum, and 1.28 kJ kinetic energy. For the heaviest coin, you're looking at 7.2 kg-m/sec linear momentum, and 3.6 kJ kinetic energy. But I suspect the drag force is going to slow it down and cost you range.

Bill Stoddard

Re: Anime: Railgun
 

also note Iron (Fe), Nickel (Ni), Cobalt (Co), and Gadolinium (Gd) are all ferromagnets.

so nickle in the coins doe give railguns something to work with, but it is inferior to iron for that purpose so takes stronger fields.

Re: Anime: Railgun
 

It's about the energy of rifle bullet. In the anime it hits more like a tank gun.

Re: Anime: Railgun
 

In principle it can be done. An electric field will pull the charges in an object that it is attracted to closer to it, and push the charges it is not attracted to farther away (called polarization). If the field is not uniform across the object, this leads to unballanced forces (for example, the field from a point charge falls off with distance, so the charges it is attracted to are pulled closer, where the field is stronger, and the charges that it repells are pushed away where the field is weaker, so the field pulls the object toward it). This effect is sometimes noticable (as when you can get an empty aluminum can to roll toward a statically charged plastic wand), but is not usually used to get high speed projectiles.

Propulsion is more straightforward if you have a projectile-to-be that is charged, but maintaining a high charge on an object can be problematic.

Modern tech uses either magnetic fields (coilguns) or a combination of electric and magnetic fields (railguns) for propulsion.

Luke

Re: Anime: Railgun
 

Haven't seen the anime, but in 4e, you'd model something like this with an Innate Attack (probably pi+ or pi++, possibly cut), having the coins as either a special effect or a -5% Nuisance Effect. Give her a limited TK as an Alternate Ability, and you're good to go.

Re: Anime: Railgun
 

You also want the skill Innate Attack (Projectile), but it's a DX/Easy skill.

Bill Stoddard

Re: Anime: Railgun
 

Psionic Powers (p.53) has TK Bullet, an ability that seems to be almost exactly what you are looking for.
It is a great book for lots of power builds & super powers. Not just for Psi.

Re: Anime: Railgun
 

Probably with "Sharp Edge" or the Armor Divisor Enhancement.

Re: Anime: Railgun
 

In the case of mentally guided projectiles, shouldn't it be IQ-based?

Re: Anime: Railgun
 

I wouldn't do it that way. TK is normally described as like having a remote pair of hands, and you use hands with DX. Here you're sort of throwing something, but it's still moving through physical space.

Bill Stoddard

Re: Anime: Railgun
 

Not hence. The electric charges flow, but the magnetism doesn't flow "the same". The magnetic field will have a static character with constant electric charge flow.

Re: Anime: Railgun
 

Normally, yes - but in this particular case, the OP is trying to model a certain fictional character.

Is the character described as aiming physically or mentally? That would determine whether the appropriate skill is based on DX or IQ.

Re: Anime: Railgun
 

What exactly does "aiming physically or mentally" mean? In terms of RAW skills, the only ranged combat skill that's IQ-based is Artillery, which is distinguished from Gunner by being indirect rather than direct fire. That sounds as if the question is whether you are shooting at something you see, or calculating where to aim, more or less.

Bill Stoddard

Re: Anime: Railgun
 

The first episode shows lots of limb-directed power displays, so DX is appropriate on that count. You can always add talent or enhancements if you need to hit anything you see.

Re: Anime: Railgun
 

That depends on the setting, which I'm not familiar with.

(Thus, I'm asking questions rather than offering answers.)

Re: Anime: Railgun
 

By the way, is the the series A Certain Scientific Railgun? An old friend was writing to me about this as his new discovery in anime just recently.

Bill Stoddard

Re: Anime: Railgun
 

I believe so - what little I know of the show matches the OP's description.

Re: Anime: Railgun
 

Okay, so this is a bit of a spoiler to those who haven't watched the series, but...

In the universe of To Aru no Kagaku Railgun (and the series it's a spin-off from, To Aru no Majutsu Index), magic is basically caused by calling down the power of God and his angels through rituals based on religion (intentionally or otherwise), and psychic powers are the result of a project by Aleister Crowley to create an artificial angel.

Basically, rather than calling upon the power of God through the construct of a religion, each Esper creates their own through the processing powers of their brains, and this manifests through the creation of an AIM field that contains their Personal Reality (and, in particularly high-level Espers like late-series Accelerator or the AIM Burst, the development of angelic characteristics like wings and halos).

The reason that Misaka's Railgun acts so strangely (e.g. doing disproportionate amounts of damage considering its mass and velocity, or the fact it stops dead when it hits its maximum range) is because she's not really launching a coin at her enemies; she's using her power to vaporise a coin into a stream of plasma, and using it to conduct/amplify her AIM field/Personal Reality, which is what probably does most of the damage.

So, if you want to represent a Toaruverse Esper in GURPS, at the very least they should all have Intuitive Mathematician, and the Esper Power Talent (which would probably be a modified version of Magery) should add to all rolls possibly assisted by mathematics, the same way the corebook Magery talent adds to the Thaumaturgy skill.