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[Rolepgeek]

Coilguns are pretty simple to make at that simple level, with railguns, AFAIK, being even simpler physically, but harder to make because of the more dangerous forces involved. The issue is that neither is up to chemical-ballistic standards as of yet.

Won't be too long. Size and logistics will be the bigger hurdles, I think. DARPA has an experimental coilgun mortar with 45 stages, and the U.S. Navy was looking/is looking into railguns for use as bombardment weapons on warships.

Basically, the forces and heat involved are just really, really silly. I'd imagine things with the thermal resistance to absorb it without partially vaporizing are too brittle to handle the physical blast.

Also true, but don't forget that the scraping action of the sabot as it moves along the rails, especially since the rails are gonna be getting pushed out, at least on a micro-level, from the projectile, where they're in contact as compared to in front of the projectile, is gonna be damaging the barrel.

Railguns are cheap, but logistically expensive. I've heard that coilguns are considered sensitive or finnicky or whatnot, but they're also reliable in a different sense than railguns are. Railguns are rugged, but you need new barrels basically all the time. Coilgun barrels are a lot more expensive to start with, and maintenance might be more necessary, but they're also far more reusable and will undergo a lot less wear, I suspect. Neither will be usable in small arms for a very, very long time, by which point these issues will be mostly solved, I suspect. (A railgun where the magazine and barrel are an integrated unit would be interesting)

[GiglameshDespair]

Coilguns are pretty simple to make at that simple level, with railguns, AFAIK, being even simpler physically, but harder to make because of the more dangerous forces involved. The issue is that neither is up to chemical-ballistic standards as of yet.

Won't be too long. Size and logistics will be the bigger hurdles, I think. DARPA has an experimental coilgun mortar with 45 stages, and the U.S. Navy was looking/is looking into railguns for use as bombardment weapons on warships.

Basically, the forces and heat involved are just really, really silly. I'd imagine things with the thermal resistance to absorb it without partially vaporizing are too brittle to handle the physical blast.

Also true, but don't forget that the scraping action of the sabot as it moves along the rails, especially since the rails are gonna be getting pushed out, at least on a micro-level, from the projectile, where they're in contact as compared to in front of the projectile, is gonna be damaging the barrel.

Railguns are cheap, but logistically expensive. I've heard that coilguns are considered sensitive or finnicky or whatnot, but they're also reliable in a different sense than railguns are. Railguns are rugged, but you need new barrels basically all the time. Coilgun barrels are a lot more expensive to start with, and maintenance might be more necessary, but they're also far more reusable and will undergo a lot less wear, I suspect. Neither will be usable in small arms for a very, very long time, by which point these issues will be mostly solved, I suspect. (A railgun where the magazine and barrel are an integrated unit would be interesting)

It is very possible magnetic weapons will never be used for small arms.
My argument comes down to energy efficiency, at its root. A soldier can carry a limited amount of weight, so you want as much bang for your buck as you can get.

A gun is 30+% efficient. As in, you put 100X energy in, a bit more than 30X of that energy goes to propelling the bullet. The rest of the energy is lost to bullet friction on the barrel (approx 2%), to heating said barrel (30%), a percent or so to propellant not burning and the remainder stays in the hot gas once it leaves the barrel, so is wasted that way.
The longer the barrel, the more efficient it is, but the gain is less than the volume ratio. That's why is you shoot the same round out of two guns, only differing in barrel length, the longer barrelled gun will be more powerful. Larger cannons also have a better volume-to-surface ratio. High barrel diameter is also helpful because lower barrel friction is induced by sealing compared to the accelerating force. The force is proportional to the square of the barrel diameter while sealing needs are proportional to the perimeter by the same pressure.

Wikipedia uses a .300 hawk as an example at 32% efficiency. Now, I couldn't find the actual muzzle energy of a .300 hawk, because for some god-unknown reason they used a wildcat catridge as their example. But for the sake of simplicity and 'good enough', I'll take that as a standard efficiency.

That's pretty decent.

The DARPA coilgun mortar was 22% efficient.
That's not awful, and it's not unusable for something you don't need to be lugging about by hand in a direct fight.
Can that be improved? Perhaps, but so far it hasn't, so I'm using that figure. Apples and oranges, but at least they're both fruit.

But energy storage is pretty heavy, particularly electrical energy. Chemical energy can be pretty good, which is why our civilisation is built on it.

A M855 5.56mm NATO round through a 20 inch barrel has a muzzle energy of 1974 J. A catridge weight, minus the bullet, is 12.31 - 4.02 = 8.29 g for 1974 J of energy delivered. 338.12 useful J per gram.

An alkaline D battery seems to have the most energy in it of the D batteries and a weight of 135g, according to this site. It has 74970 J in it. At 22% effeciency that gives us 16493.4 J. That would give us 8.36 equivalent 5.56mm shots.  122.17 useful J per gram.
Quite a difference. I chose the D battery because that's the largest common battery I can think of that isn't, say, a car battery. Perhaps handheld coilguns would be like hellguns from 40k and attached to a backpack power source, but I've not looked at that.

 Remember, that's using the 45-stage mortar, not any handheld coilgun, though I'm not confident enough to ballpark any figures for a lesser stage weapon. The coilgun in this video (though it is just a hobbyist project and not representative) has an 'estimated efficiency of 1-3%'. I'm guessing that a handheld coilgun might get an efficiency somewhere between that and the mortar.

It's not really a fair comparison, being overly lenient towards the coilgun as it is, but hey, it's rough.

Energy isn't quite the same issue if you've got something like a battleship or a vehicle you can suck power from, so no doubt they'll end up on there sooner or later. It's also at that sort of scale the benefits of a magnetically accelerated projectile start coming about.

---

When it comes down to it, what benefits would a magnetically accelerated weapon give your infantryman? Power isn't always a must for a soldier, because they dropped down to the 5.56mm from the more powerful 7.62mm round. It would weigh more. It'd probably be less sturdy. It might shock you if it gets damaged with a lethal voltage. rate of fire might be limited by how fast the capacitors could charge, but I'm less knowledgeable about electronics like that, so I couldn't say. A conventional gun probably has less and more sturdy parts than a coilgun.

It would presumably fire a supersonic projectile. This would mean they would hear the supersonic cracks of your round, so the rifle wouldn't be silent. Modern metal baffle suppressors can reduce muzzle flash and noise without reducing velocity, so there's not a huge benefit going mag if that's your main concern.

You'll still have recoil. Sir Isaac Newton may the deadliest son of a bitch in space, but that's true on the ground as well.

---

"But Gig," I hear you say. "What if energy storage and coilgun efficiency both improve?"
Well, they'd still have quite a bit to go before they matched conventional propellants. And even if they did... who says a better propellant for small arms won't be developed, either? After all, black powder gave way to smokeless powders.

---

I'm not looking at railguns for small arms because carrying around more barrels as well as everything else is just an awful idea. Like coilguns but shittier.

TL:DR magnetic weapons suck at man scale

Also goddamn this post is longer than I expected. Did I fuck up any of the maths? Probably. It's all rough, anyway.

[Rolepgeek]

Coilguns are also able to use most any munition size below their barrel diameter. Don't need a seal, after all. So logistics gets a bit easier, and with recharging in the field via portable solar cells or from centralized generators found in the vehicles that also use such weapons and the like, it could be a significant advantage. Once/if we get room temp/hot supeconductors, inefficiency should be less of a problem. Not none, but 35-40% could very well be possible. Especially if we can get super capacitors and the like to store electrical energy more effectively.

Of course, you could also combine the two with Explosive/Flux Power Generators. Would probably require a bit larger weapons, but I don't see these weapons being used much for handguns and the like; I suspect that as armor gets better, and handheld infantry antitank weapons become less effective (missilesare starting to hit their 'counters have been developed' stage, if you take a look at this next generation of tanks being developed, for example, though that's be no means certain(same also might be true to a lesser extent of helicopter gunships)), there'll be a push towards powered armor. Whether it can be made or not is another matter, but if it is, I suspect it's most pronounced use will be as the newest type of tank destroyer. Smaller, more agile, possibly faster than typical infantry men, with (relatively) heavy armor and heavier guns. On vehicles, and on these suits, and maybe on a few RPG/Javelin-equivalent weapons for infantry, is where I'd expect to find magnetic weapons. The vehicles use them to pack as much power as they can in their shots, period, the suits want them to have something powerful enough to deal with vehicles and each other, possibly also using them for anti-infantry at lower ammo/power levels. Anti-vehicle equipment for infantry would probably be large and not all that mobile, similar to modern-day TOW missile launchers. However, anti-suit sized weaponry would probably exist, and be both less expensive than missiles (unless the weapon itself was lost), and possibly more effective.

Finally, the modularity of their available munitions would allow magnetic weapons to function in nearly any role, limited only by barrel length and weapon bulk, even more so than current modern weapons. You could also probably set the speed fairly easily on a minute-to-minute basis, allowing for subsonic fire when necessary and full power when things kick off.

[GiglameshDespair]

What did you base that 30-40% figure on?

[Rolepgeek]

Estimate of the probably increase in efficiency as coilgun manufacturing/engineering and the associated technologies improve. It is in relatively early stages, after all. Particularly if room-temp superconductors can be developed. If you're asking me to provide examples, I didn't have any, but quick searching brought up nailguns as an example of commercial use of coil tech. This, in particular, seems quite intriguing.

[GiglameshDespair]

So an arbitrary number.

I'm hesitant to rely on inventions that may or may not ever materialise - nothing more than transient effects have ever been shown for room-temperature superconductors. Same with supercapacitors and storing electrical energy. While they may and probably will improve, you can't accurately predict how much, so pulling out a figure like that is utterly meaningless, really.

The thing about the coilgun nailgun you linked was... interesting. Mainly because they concluded it wasn't worth using at its current state.

Integration  is  likely  impossible;  if  anyone  thinks  they  can  do  this  then  they  should stop eating dog food.

5% efficient - it used more energy, and weighed 15lb (~6.8kg)_{unloaded, I think?}, twice the weight of an unloaded m16 assault rifle at 7.18 lb (~3.26kg). It was more unwieldy since it had a longer barrel than other nailguns. It was more complicated than other nailguns. It couldn't fire automatically, as that would need a second capacitor bank, and that would have added more to the weight.
More the more stages, the more effecient, but you get less and less each time, and more and more weight.

And that's a nailgun, not something anywhere near a military application. Soldiers aren't armed with nailguns.

[Grimlocke]

Ah, someone mentioned power armor, a staple of sci-fi.

I seriously don't think these will be useful in any way beyond logistics, at least not beyond what we typically see in fiction (warhammer, fallout, etc).

They are like infantry, except without all the advantages infantry has: They move quick, can easily hide, take cover and move around difficult terrain. Big clunky power armor negates all these things, but its going to be too small to throw around more firepower than infantry can already carry with them as mortars and such. They are also going to nowhere near as well protected or as fast as an armored vehicle, which would just turn them into fodder for artillery and air strikes.

I suspect they would pretty quickly go the way of the tankette: a convenient self-moving coffin.

If power armor is going to be tactically sound at all, disregarding for a moment the technical soundness, its going to have to be able to move around as well as infantry already can, not make them easier to shoot and still offer reasonable protection again smallarms and nearby explosions/debris.

I think that if your going to be a high profile target, you better be small or fast enough to stay clear of heavy ordnance, or big and strong enough to roll with the punches. Roles like APCs, ATVs, gunships and tanks already seem to stick to this rule. Of course for the latter category, there is always going to be a gun too big for your armor, but those guns are going to be a good bit more noticeable than what could kill a comparatively tiny man-sized tin can.

[Tuxfanturnip]

This is why I envisioned the split that I mentioned earlier, between exoskeletal armor focused on moving its own weight quickly and efficiently and one-person tanks that happen to be humanoid. Actuators could probably improve agility overall, though as always power becomes an issue...

[Tack]

Yeah power armor got worked over about 5 pages ago.
But your input does make sense.

[i2amroy]

Ah, someone mentioned power armor, a staple of sci-fi.

I seriously don't think these will be useful in any way beyond logistics, at least not beyond what we typically see in fiction (warhammer, fallout, etc).

They are like infantry, except without all the advantages infantry has: They move quick, can easily hide, take cover and move around difficult terrain. Big clunky power armor negates all these things, but its going to be too small to throw around more firepower than infantry can already carry with them as mortars and such. They are also going to nowhere near as well protected or as fast as an armored vehicle, which would just turn them into fodder for artillery and air strikes.

The key is that rather than going the WH40K "STOMPY POWER ARMOR" type of armor you want to go a light, powered exoskeleton path instead. If you go the light path than you could conceivably create an exoskeleton that would trade a couple of milliseconds of reaction time (which is so small compared to normal human reaction time to only be a very, very small penalty) and a very tiny amount of agility for increased strength, increased running speed, and most importantly, nigh-unlimited endurance. Any amount of armor or increased weaponry that is heavy enough to have a real effect would, as you mentioned, essentially result in the ruining of all of the things that infantry are useful for. If, on the other hand, we just focus on the mobility aspect, and design it so that rather than carrying all of your gear it interfaces over the top of the gear infantry already have... and I think that you'd find many a commander that would make the trade to gain the ability for infantry to move as fast as vehicles and never get physically tired from exertion.

This is why I envisioned the split that I mentioned earlier, between exoskeletal armor focused on moving its own weight quickly and efficiently and one-person tanks that happen to be humanoid. Actuators could probably improve agility overall, though as always power becomes an issue...

Honestly one person tanks just aren't really feasible compared to normal vehicle tanks due to two simple ideas, ground contact area and center of gravity. Because humanoid shapes have a much smaller area of contact with the ground, this means that they sink in more. As you need to pile heavier and heavier armor on something for it to actually be useful against higher powered weapons, that means you're going to be sinking more and more into the ground. It doesn't matter how cool your armor is if you sink 4 inches into the ground with every step; your mobility is hampered so much that you essentially become static (and your ability to climb over things isn't exactly going to be helped either; a normal tank can run over a normal car or pile of debris, crushing it, but your smaller contact area is just going to result in you becoming ensnared as it collapses beneath your feet but nowhere else). And the higher center of gravity doesn't help much either; you are going to be much, much easier to knock over than a normal tank is going to be, and you're going to share the same problem that normal tanks have, i.e. that if they get flipped there isn't exactly much they can do about it, since with every additional bit of power you lump into the pushing power of the arms all you are going to do is raise the center of gravity even higher, making it even easier to tip you over.

[wierd]

lightweight exoskeletons already exist.

exhibit A), the Hybrid Assisted Limb from Cyberdyne

exhibit B) Phoenix mobility rig from SuitX

exhibit C) HULC from Lockheed-Martin

That's THREE already existing lightweight exoskeletons.  One of which is already made for military applications.

IIRC, Boston Dynamics has/had one as well, but I cant remember the name of it.

[Cryxis, Prince of Doom]

wow I go absent for a month and one of my threads becomes popular XD yay!

[Tack]

It's one of the most brilliant ideas for a thread I ever.
My heart almost skipped when I saw it.

[Dirst]

My heart almost skipped when I saw it.

There must be a way to weaponize this...

[Tack]

Have we discussed Zombies yet?
Nanomachines, yes, but not specialist viruses, I don't believe.

Well, it doesn't have to be zombies. But they probably do good work as a terror weapon.
Unless the virus decides not to die before occupation day.