Theoretically, yes, however, remember that railguns work on a somewhat different calculus than traditional kinetic firearms. Part of what makes railguns effective is that they fire very massive projectiles: these are small, but they are heavy and deliver good penetrating power. This is an evolution of traditional firearm bullets, which are likewise heavy and relatively small. The smaller the package you put the force into, the better it is at avoiding armor. Now, nominally, a railgun can simply adjust mass to achieve a "silent" projectile, increasing the weight in order to reduce the speed (as some traditional firearm cartridges do) to a subsonic level. However, the detriment of this is that you lose many of the benefits of a railgun: the ability to fire projectiles at far supersonic speeds with much more controllable recoil and other functional benefits. This means that projectiles need to be increased in size, which is not easily achieved, as doing so will almost certainly mess with the feed mechanism (which is going to be more complex; recoil actions, the traditional and friendly way to deal with firearm feed systems, require recoil from a combustion). Although it is possible for a railgun to fire projectiles of an arbitrary size if the feed mechanism is designed for this, there are only a few ways one can get the projectile to fit those specifications, and at the very least you would see reduced ammunition capacity. Range falls significantly with the switch to subsonic speeds, and armor penetration does too. The effective range just can't stack up because of the fact that projectiles are more susceptible to environmental forces due to increased travel time and the small but important fact that things are still in motion. Armor probably doesn't care a whole lot with the projectiles involved in railguns, and with an appropriate payload you could probably wind up with a very effective weapon, but IIRC there is an increased deflection chance at reduced velocities, though that may just be a flaw with weapons not achieving strictly identical performance with subsonic loads IRL, and would not apply to a properly designed railgun for various reasons. If you are increasing the impact-point's area, it will have a negative impact on armor piercing. TL;DR: The actual damage and armor piercing are likely only negligibly effected, but you do see a major decrease in accuracy, range, and ammunition capacity relative to the desired amount of ouchie. Higher-performance subsonic railguns could overcome some of these difficulties by either shifting down in performance (becoming more akin to a traditional firearm in performance), accepting the loss of magazine capacity relative to volume and increasing magazine capacity, or utilizing the fact that the increased projectile volume means more opportunity for bonus effects (e.g. homing rounds, explosive rounds), most of which will negate some of the silencing factor of a railgun. Total silence is also somewhat unlikely: while the machinery is likely silent compared to most things, you'll at least hear the operation of mechanisms and perhaps some electric discharge as the weapon fires, so it's perhaps approaching the Hollywood mouse fart that silencers are believed to allow, but similar performance can be achieved by almost every weapon class in EP. Some of the point of stealth is lost by the fact that almost everything is meshed, though. Unless you're operating in certain environments, the loss of a unit will be immediately clear to your opponent's C3. If you're operating against civilian/low-cohesion paramilitary targets, you likely will be able to achieve a modicum of stealth, but transhumans go down less quickly than unaugmented humans and can shout a lot louder thanks to endos.

Sure. I think railguns can fire at slower speeds. Just have less electro magnets active, or just reduce the power used. I don't know why rules for that weren't included. But not only that, I want to be able to fire arrow or crossbow bolts from my railguns. You know, like what Yoko did on Gurren Lagann. You could turn a railgun into a hunting weapon with reusable arrow ammunition. I'd like to hunt me up some critters on my next gate trip*. *Not really. I don't know if the local lifeforms are going to poisonous or, you know, silicon based. Plus if you put the money into a good maker, food quality is not going to be a concern.

Excellent point on that last bit there. Yea. It wouldnt be audibly noisy, but electrical sense, enhance vision, and maybe radar could detect it. If you have equipment set up in advance you could totally detect it like you would a radio signal. And with eclipse phase tech, the em bloom only lasting a few nano seconds shouldnt matter. So then... there should be a faraday cage barrel mod for railguns.

MrWigggles wrote:

That would surprise me if damage and ap isnt really effected by its decrease in speed. I did fail to consider making it harder to aim with a 'slow' railgun. Part of what makes railgun nifty, is their speed makes them able to travel stupid distance before the effect of gravity starts to make the projectile curve down. Isnt a lot of the killing part of the Railgun from its supersonic speed? The tl;dr equation is f=ma. And there is a lot of accretion. I know the actual math isnt that, this is just for guestimating.

If you took a 5 gram projectile and replaced it with a 500 gram projectile, you could see good effect, though, again, that has obvious downsides (namely, the fact that your 500 gram projectile is going to take up more magazine space, require more robust loading systems, et cetera. It is typically the case that railguns depend on velocity, rather than mass, for energy, but a very massive projectile could still work. It would just be odious to operate in some conditions.

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Unlike traditional firearms railguns don't have to be built with self-sealing barrels, only rails or coils (in reality [railgun]!=[coilgun]). The source of gunshot sound is the sudden release of pressure the moment after bullet leaves the barrel. with railguns there is no extreme buildup of pressure and any that occurs due to moving projectile can be relieved by openings in the barrel. Therefore the only sound that IDEAL railgun should make is the sound of moving bullet. With high Mach speeds of the projectile this sound would be quite loud altough probably not in human hearing spectrum.

Yes, but again this is a limitation of ideal versus practical. In Eclipse Phase, the sound is likely the last place to actually indicate the use of the weapon (or at least, the last place that most people directly engaged would get information, as literally every other piece of information comes in at supersonic speeds). Keep in mind that I intentionally avoided talking about pressure when looking at noise sources (though, again, to mitigate EM interference you might have some sort of containment for the railgun mechanism, which would create an opportunity for pressure differentials, and if you are using very large projectiles to reduce the required kill speed of the projectile, you wind up displacing more volume). I suspect that any railgun will be using an electric feed mechanism akin to a minigun; while there's likely no huge noise from this (the mechanism is smaller, for instance), when you're dealing with transhuman perception you need to be a little less charitable to "stealthy" weapons. I think that the level of energy involved with a traditional railgun projectile would be such that even if it does not hit the human hearing spectrum there could well be a shockwave. I doubt that this would have any meaningful effect on even a flimsy biomorph, but it would probably be something that alerts a savvy target to the presence of a weapon.

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Other consideration is that railguns are basically giant electromagnets. They do not make a sound in the spectrum that we are able to hear but EM spectrum is different. Radios, apropriate sensors and other EM detectors would probably be able to not only "hear" them, but localise them with accuracy of meters.

In this sense, a stealth railgun will inherit some of the issues of a traditional firearm when being made stealthy. You will need to add components to reduce the amount of perceptible operation of the weapon, to the point where you could wind up with a railgun "silencer" that reduces its EM signature. As you do this, you are going to wind up increasing the size of the weapon and making it more bulky. That said, you could find single-shot/disposable faraday case enclosures to limit the exposure from a single shot, but that's going to degrade.

I blame weber for making hyper velocity micro projectiles able to rip entire torso's off popular:P there is a problem with armor piercing projectiles and soft bodies, Spycraft actually has mechanics for this, and after a certain point of penetration effectiveness we go from Armor penetrating to armor defeating. fire a railgun slug at an unprotected flat and that round is going to go right through it with little more damage than the entrance and exit wound. this happens because the kinetic energy of the projectile can not transfer to the soft tissue fast enough except that which is directly in the way. Same applies for rigid bodies but the threshold for armor defeating is harder to achieve a not specifically on faraday cages, they need to be grounded in some fashion, not sure how to work that in a vacuum

ORCACommander wrote:

I blame weber for making hyper velocity micro projectiles able to rip entire torso's off popular:P

Great author, but not really. Weber could be the greatest hard military sci-fi writer that ever lived. But he doesn't have an editor. Or it seems so.

SquireNed wrote:

Energy transfer would still be non-negligible for a hypervelocity projectile, though there is certainly a concern regarding impact area versus high speed and projectiles simply going through targets like a hot knife through butter.

When the projectile hits the target it has to displace the matter that it "travels" through. When it has multiple Machs in velocity the "flesh shockwave" could be more damaging than the bullet itself. Check out internal damage in car accidents.

SquireNed wrote:

That said, the only way a railgun shot is taking off a torso or limb is if it is sufficiently large or combined with some secondary effect (e.g. an explosive, which would have a yield commensurate to its size).

I always imagined that hypervelocity shotguns leave their victims like thermites their wood. Full of holes but not disintegrated. If you suplemented it with explosives it could really be disintegration, splatter and Psycho-Pass style death.

For the game mechanics of a subsonic round I'd use base kinetic weapon damage minus 1d10 but leave the AP intact (because the AP is functionally reduced anyway), and have all targets count as one range category higher than normal. Regarding the thematics, silencing a railgun is fairly simple. The only mechanism is the ammo feed, and that can be done away with by using actuators instead of springs to move the rounds. Suppressing the magnetic effects should actually be really straightforward. Even without any considerations the overflow 'has' to be minimal, otherwise you'd blow out your mesh inserts and all wifi-connected gear the first time you fire, not to mention the internal circuitry. Beyond that, magnetic fields attenuate [i]quickly[/i] with increasing distance, with the exact rate depending on the field geometry. Ever messed around with strong magnets? Place them together and it's a nightmare getting them apart, but with just a little bit of space the attraction becomes imperceptible. Practically, this can be achieved through clever magnet design, using room-temperature superconductors to create a covering impermeable to magnetic fields (incidentally increasing the field strength within the covering), or using EM coils to actively counter the field. That said, the first time you actually shoot someone they're going to be screaming about your presence onto their network or they're going to drop out due to 'user mortality', so suppression beyond that point only prevents them from using audio for exact positioning – they still know you're there and can see you via spines. Blanket-jamming prevents this but very blatantly announces your presence, so again it's usefulness is limited.

Eclipse Phase tech is really well shielded. I'd expect the gun to make less EM than a purpose built grenade, and those only mess up radios.

Could you please elaborate on what you mean by solid technology? As far as I know Eclipse Phase electronics are still built from circuits, and circuits are prone to induced currents.

You can't [i]negate[/i] magnetic fields, but you can suppress them by introducing additional magnets to alter the geometry. Essentially you would be 'squishing' it so that it's more focused within the barrel or so it extends along the barrel axis. Ideally, the only person capable of detecting the magnetics of you firing a railgun is the person you just shot with a railgun. Changing the weapon layout works too. If you extend the barrel length (totally not a reason to give railguns silencers) then you increase the duration the round is accelerated reducing the required field strength. Now that I think about it, DivineWrath's RailBow would actually make sense. Making the projectile long and narrow increases the applied force whilst the reduced barrel diameter increases the barrel flux. Another idea I've played with is having railguns fire tubular rounds, with the primary coil running through the center to decrease the portion of the field not doing useful work.

Eclipse Phase computers are stated to generally be photonic computers IIRC, though I suspect there's a lot of nanomechanical computing as well, considering how advanced EP nanotech is. They'd still need to be pretty well shielded though.

http://guns.connect.fi/rs/bulnoise.html Really loud, but still a lot quieter than a gun (~160 Db). Railguns are potentially louder though, as they fire about twice the max speed on the chart. One important difference is that it's the bullet not the gun making the sound though, which makes it much harder to tell where the shot was fired from.

"Railgun operation makes no flash and is silent except for the supersonic crack of the projectile." P. 336 EP, in the 4th Printing.

[s]Strange that would be added in 4th, i think the text i was looking at was from 2nd print. Will have to download a fresh one from dtrpg instead of using the html, if I get a game going again.[/s] [i]edits: okay, first it looks like I'm just blind and it has always been there. Second, I seem to have some EP stuff in my DT library I've never read or don't remember buying, so that is a nice surprise.[/i] Have to agree with Camillus, it seems whacky. I can imagine some magictech scenarios where it might be "explained" but none are less offensive than just calling it a coilgun if it needs to be silent. EP seems to straddle a wierd place between fantastic 'Trek-like magictech, and gritty Aliens or 2300AD style "hard" SF. My own tendancy is to push it toward the later, but the unique charm of the setting is to explore the boundary. The game needs to be paired with something like "Shock" to explore the broader ramifications of these oddball things.

you can listen to the audio of modern railguns -- everything from US Navy models to home made things that people shoot in their garage or through car doors. Enjoy some youtube. I stand by the screeching train thing; it is just that it is only screeching for a few milliseconds. And, as you say, is exerting a much smaller force on the rails than something as heavy as a train. Trains tend not to ablate their rails into hot ionized metallic gas though, so the forces involved are non-trivial. (of course, train rails tend not to be made of copper...)

I dont know how modern ones work, but antique arc-lights used to have adjustable elements that you could screw in. Bring them closer together as the electrical arc wore down the graphite, or whatever. Slightly more modern ones had clockwork mechanisms that automatically screwed them in at a constant rate. I assume modern stuff is just bulbs, but the big searchlights and beacons and such might have something similar. Anyway, maybe the rails mechanically screw in as they ablate. Thus lengthening the time between changes :)

It would probably need active cooling, if we assume the weapons are meant to be used in vacuum and and atmosphere. I suppose if Eclipse Phase went the route of shadow run there would be vacuum and atmo variant of guns. But I think we have to assume their compromise to work well in both. And I think it needs active cooling.

A bullwhip goes supersonic. Not a lot or for long but it does. So that's about the noise level, aka "not quiet". You can argue that a projectile is smaller except that it is supersonic over its entire flight path while the bull whip is only supersonic over a couple of centimeters so I'd say the total volume of distorted atmosphere is comparable. As to the damage of lower velocity rounds, here is a simple analogy. Railguns do damage by piling on speed to an undersized projectile. Take the speed away and you have an undersized projectile firing at gunpowder speeds. You almost need to take the base weapon and subtract the rail gun modifiers. I.e a light rail gun dialed back to subsonic does 2d10-2 with a -3 AP. On the plus side, the batteries will last a lot longer so you can fire more of those low velocity pebbles.

I would suspect that the noise range gets put out of human hearing. It would probably be ultra sonic.