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I want a weapon that can:

  • Chew through reinforced concrete like it were popcorn,
  • Blast through 4-inch frontal armor plating of tanks like it were papier-mâché in the wind
  • Has a high (or continuous) rate of fire, or makes a high rate of fire unnecessary through sheer murderous awesomeness.
  • Be man-portable (a grunt can carry it and use it in a firefight).

Initially I was considering railguns, but I'm starting to suspect the combination of iron plasma and the recoil would probably kill even exoskeletoned and full-body armored infantry.

So what will my Death Legions wield? Lasers? Relativistic shard guns? Some sort of particle weapon? Superacid projectors? The relevant criterion is that they be conceivably manportable and not physically impossible (even if not feasible now, and even if heavy enough to say require a powered exoskeleton, but must be possible and plausible -- i.e. no known way to manipulate gravity besides moving heavy objects around).

Edit: Have been asked about Tech level. I'm quite flexible, from near-present to advanced-miniaturized-fusion reactors, maybe even very early antimatter tech. I'd steer clear of Zero-Point, since a mug's worth of empty space energy could boil our planets oceans. Seems like overkill, even for Marines. Generally, the sooner I can have them, the happier I am with the answer, so slight bias towards presently reachable tech.

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    $\begingroup$ You want something that is feasible? I think you're going to run into an energy density problem. You can't store enough accessible energy and the weapon to direct it on a human that can do damage like that for any interesting amount of time. Unless, you go with the obvious and have grunts carry nuclear warheads. Do they need to live? $\endgroup$ – Samuel Jan 8 '15 at 18:09
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    $\begingroup$ Alternatively, can they use exo-skeletons to use it? That might also answer @Samuel's question -- there could be motors and nuclear shielding (lead?) in the armor. $\endgroup$ – Shokhet Jan 8 '15 at 18:12
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    $\begingroup$ Davy Crocketts only output something like 20 tons of TNT per warhead. That'd be more like a light hand grenade... I mean obviously this won't be achievable with current tech alone. Can't power my death rays off of nine volt batteries. $\endgroup$ – Serban Tanasa Jan 8 '15 at 18:13
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    $\begingroup$ "Chew through reinforced concrete" Genetically enhanced rats? $\endgroup$ – KSmarts Jan 8 '15 at 18:41
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    $\begingroup$ What technology level are your death legions at? Do they have antimatter-based power systems on their backs? Can they manipulate gravity? Available technology would be helpful in not making this question entirely open ended. $\endgroup$ – ckersch Jan 8 '15 at 19:43

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As other mentioned, there is no scientifically plausible way to pack energy dense enough to be man-portable for your usage. Nuclear weapons are not portable enough, and chemical energy in explosives is the densest we can do now or in foreseable future. We don't know how to make backpack fusion generator to power lasers.

So let's add sufficiently advanced technology (which we cannot distinguish from magic): Backpack-portable matter-to antimatter converter. It swaps electricity charge in nuclear particles, making positrons from electrons, and anti-protons from protons, keeping total charge the same, and not needing any energy to do it.

Now you can pick pebbles, feed them to your converter, and annihilate your opponent. Only energy you need is to accelerate your anti-pebbles, which is easy. Bring lots of sunscreen, it will be bright!

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  • $\begingroup$ Ha, +1 for sunscreen reference. Not quite sure if this qualifies as 'early' anti-matter tech, but good idea $\endgroup$ – Twelfth Jan 13 '15 at 19:53
  • $\begingroup$ Thats not true. You CAN do man portable nuclear weapons. $\endgroup$ – Jorge Aldo May 7 '15 at 15:34
  • $\begingroup$ Yes, in theory you can pack supercritical chunks of plutonium in a backpack, if you do not waste weight on shielding. So grunt can walk in, set timer, store backpack under a bench in a park, and run like a hell to hospital to have chance surviving radiation burn, maybe. Cowardly way of fighting, cannot kill tanks (unless they are in the vicinity), cannot direct fire to target - does not match OP specs. $\endgroup$ – Peter M. - stands for Monica May 7 '15 at 15:42
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Each of your Death Legionnaires should be equipped with an AK47 assault rifle, loaded with bullets laced with inactive nanite disassemblers. The barrel of said AK47 should be tipped with a combination silencer/nanite-activation device such that as bullets leave the weapon, the nanites inside them start waking up. By the time those bullets reach their targets, the nanites are ready for breakfast.

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  • $\begingroup$ Well, minus the 'how do you prevent the wholesale destruction of the planet' portion of the problem - I like this solution, except that you're limited on ammo. Reminds me of a truism: Logistics trumps tactics, because a gun is only a weapon if it has ammunition. $\endgroup$ – user3082 Jan 8 '15 at 22:26
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    $\begingroup$ 600rpm, 100rpm effective - 27 rounds/pound == 22lbs per minute at the high end, 3.7lbs on the low-end of "high" rates of fire. And you'll burn thru your barrel, without water-cooling. OTOH, you shouldn't need multiple shots; one shot, one kill. $\endgroup$ – user3082 Jan 8 '15 at 22:34
  • $\begingroup$ So swap the AK47 for a sawed-off shotgun with the same nanite enhancements and nanite ammo. Plus lots of spare inactive shells and some anti-nite armor (laced with nanite disassemblers which target only the ammo's nanites) to defend against blow-back. Give the ammo nanites a limited lifespan which shortens with every generation so that the planet doesn't go grey goo. How's that? $\endgroup$ – Henry Taylor Jan 9 '15 at 1:13
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    $\begingroup$ "Nanite disassemblers" don't need to lead to grey goo. That's only if they are self-reproducing. So the easy solution is: don't make them self-reproducing, in addition to the limited lifespan. $\endgroup$ – KSmarts Jan 9 '15 at 22:13
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    $\begingroup$ Ksmarts, how do you get enough of them on-target without self-reproduction, from the volume of less-than-a-bullet? How do they gain enough energy to do the work necessary to make them effective in a reasonable time as a weapon? If they work slowly enough that I can wash them off, or bring my tank around to blow up the Death legionnaire, I think OP won't be happy with them classified as a "weapon of MMD(M)". $\endgroup$ – user3082 Jan 10 '15 at 14:37
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LASERS

If you can get the energy density, a megawatt FEL will burn through 20 feet of steel per second. Which should be enough to do the damage you want. Needs some technological shrinking (it's a shipboard weapon) - but they were well on their way to this in 2011.

Cold fusion backpack reactor?

(corrected, thanks: ckersch)

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  • $\begingroup$ I think that's the number for a megawatt FEL, not a kilowatt. wired.com/2011/02/… $\endgroup$ – ckersch Jan 8 '15 at 21:49
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As Samuel notes in comment there are some pretty serious energy density issues. Apart from the difficulty of storing enough energy, there is a serious problem with the side effects the release of energy has on the user. With both kinetic weapons and energy weapons a significant percentage of usable energy would be released as heat and pressure waves at the weapon. As such the only real solutions are liquid projectors and weapons shooting explosive grenades where these side effects are suffered by the target.

Liquid projectors have two issues. First, they generally are area effect weapons and have poor penetration, which does not match the desired effects. Second, while there are chemicals dangerous enough, dangerous chemicals have an annoying habit of being dangerous. I can't really think of a safe way to go beyond melting or igniting armor. And that type of effect is very different from what you want. You'd probably kill most things you attack, though.

If we dropped the plausibility requirement and assumed a "nuclear stabilization" technology, you could have particle accelerator shooting ions of unstable isotopes of heavy elements. The ions would then penetrate armor and decay inside it. This would destroy almost any armor eventually with an effect matching the desired one.

A weapon shooting HEAT grenades would be the one plausible way to get the effect wanted. Every hit destroys some armor and weakens the area, so a weapon capable of doing accurate rapid fire with even small HEAT grenades would disintegrate the armor. A four inch armor was mentioned. That is roughly 116 mm. Wikipedia gives a typical penetration of 7 times the charge diameter. That would suggest that a 30 mm HEAT warhead could penetrate up to 210 mm with optimal design and circumstances. Since we only want half of that and are more interested in destroying the armor than penetrating it, 30mm or even 25mm should be enough.

An automatic weapon shooting grenades in this range is plausible, as is a man portable weapon shooting grenades this size. As HEAT does not need high muzzle velocity, recoil compensation should be an solvable issue.

There is one serious issue, though. The weight of ammunition. A 25/30mm HEAT grenade isn't that heavy, but if you want to fire them full auto to really chew through walls or armor... Well, with a special carrying harness and ammunition belt-fed from a backpack. Why not? I sure wouldn't want anyone to shoot me with a weapon like that.

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    $\begingroup$ What sort of weapon would you like someone to shoot you with? $\endgroup$ – KSmarts Jan 9 '15 at 16:53
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    $\begingroup$ @KSmarts A harmless one. Preferably without significant noise or distracting flashes of light. $\endgroup$ – Ville Niemi Jan 9 '15 at 17:40
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    $\begingroup$ @VilleNiemi I think you are looking for Nerf. www.nerf.hasbro.com/‎ $\endgroup$ – James Jan 9 '15 at 20:08
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    $\begingroup$ @VilleNiemi But if it is harmless, is it still a weapon? $\endgroup$ – KSmarts Jan 9 '15 at 22:16
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    $\begingroup$ @KSmarts Yes, specifically, the kind of weapon I'd like to be shot with. More seriously, militaries actively develop harmless weapons for use in training and spend lots of resources trying to make hostile weapons harmless. So "harmless weapons" really is a real thing. $\endgroup$ – Ville Niemi Jan 10 '15 at 8:25
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How about a miniature belt-fed rocket launcher with 3-stage rockets?

Stage 1 merely gets the rocket to the target, so you aren't wasting too much force on recoil. Once it gets there, it clamps on to the material it hits and fires off stage 2.

Stage 2 acts like a shaped charge and drills through the material using the first stage as a back plate.

Stage 3 blows up.

There you have it. A shoulder-mounted semi-auto bunker-buster. Maybe stage two doesn't get all the way through your 6 feet of concrete, but after stage three puts a massive hole in it, two seconds later you are hit with another round.

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  • $\begingroup$ Nice one! I like it! $\endgroup$ – Serban Tanasa Jan 13 '15 at 1:25
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I would guess you're going to need something like the 25mm cannon on the Bradley fighting vehicle. I would expect it to be a smaller caliber to make it portable (maybe a team of 2 or three) and it would have to be set up to use (we already have teams and emplacements for the 50 Cal.) The big thing the 25mm has is multiple types of ammo available. Mostly High Explosive (HE) and Armor Piercing (AP) rounds, but that doesn't mean more couldn't be designed.

Of course the problems are that you want to punch a hole in something and other times you want to 'blow it up'. There might be other problems to, like needing to disperse groups, so having some tear gas rounds could work for that.

Punching holes usually needs mass traveling at high speeds, which means something has to push really hard on it. Newton explains how that works.

Lasers as weapons are problematic primarily because of the sheer power needed to burn a hole in anything worth burning a hole. acid? problem getting enough of it to the target to do good, especially more good than a high velocity round. Acid is also pretty slow when compared to other types of weapons.

EDT: Just thought I'd add, Zion in the matrix was protected by people in Exoskeletons with 25mm Vulcan canons

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The main problem you have here is recoil, anything you fire out forwards pushes the gun backwards.

This can be fixed if we make the bullets self propelled (essentially tiny rockets). Antimatter would provide sufficient energy density for this. For bonus points the remaining antimatter would cause a small explosion when you strike the target and the result would be catastrophic for anyone hit as these bullets would be high caliber, extremely fast, high explosive force...and would even home in on the target with a very basic guidance system.

From a technical/scientific point of view the antimatter would need to be generated somewhere, but the real trick is going to be storing it.

If the antimatter is stored in the bullets then they would need some sort of hard vacuum chamber suspending the antimatter in the center somehow. Containment breaches would be bad and very hard to avoid.

A more likely system would be to have the gun store or even better (safer) generate the antimatter on demand (this would involve some serious power sources though so containment might be the only option) and the bullets are filled with antimatter as part of the firing process.

An enemy strike on the antimatter reservoir of a gun would be seriously catastrophic for anyone in the area though. Expect shielding those to be a high priority.

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What you want is a Davy Crockett device.

http://en.wikipedia.org/wiki/Davy_Crockett_%28nuclear_device%29

It is a man portable nuclear launcher. It has a high rate of fire, lots of destruction power and can render areas uninhabitable.

Its problem was that they killed the program. If it had been continued, the accuracy problems would have been resolved, smaller devices would have been made, small enough to be carried by a human(javelin size is small for this sort of things).

Mount these on an a-10 and you have one big terror weapon.

p.s. OP wants a weapon of utter destruction, so radiation is a up-side on this matter. He would likely never try to clean it up.

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  • $\begingroup$ Well, as long as all the radiation stays fictional... $\endgroup$ – Serban Tanasa Jan 9 '15 at 11:37
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Just use a two-barrel gun.

The simplest two-barrel gun is capable of destroying a bunker, if you load it with antimatter bullets. The only issue is the design of the bullets themselves.

So, a standard cartridge has three parts: bullet, case and gunpowder. Do not modify case nor gunpowder, but make the bullet a bit different: an antimatter container. A small amount of antimatter suspended in an electromagnetic field.

When the bullet impacts the tank or bunker, it just breaks, like any other bullet. On doing so, the EM field device just breaks as well, the antimatter gets released, contacts matter, and givs you a shiny beatiful explosion.

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  • $\begingroup$ An EMP would be rather unpleasant for the Death Legions, then. Or not, because if the electromagnetic containment broke, they probably wouldn't be around long enough to notice. $\endgroup$ – KSmarts Jan 13 '15 at 20:56
  • $\begingroup$ An EMP should not affect something inside a Faraday jail... like a metallic bullet. $\endgroup$ – Envite Jan 14 '15 at 16:27
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While I agree with Peter Masiar that the energy density is unobtainable I don't think you need to violate the laws of physics that greatly to get a solution.

Rather, lets hypothesize a device based on extreme gravity control--able to project internal fields approaching those of a black hole. The weapon consists of a tube with the generators in it and whatever support equipment is needed. When fired the weapon sucks in air from the back and uses it's gravity field to pinch the flow through an incredibly tiny and incredibly thin aperture. The result is fusion--but since it isn't instant the fusion occurs on the far side of the aperture. Some of this energy is captured to power the weapon, what isn't captured comes out as a plasma beam moving a few percent of lightspeed.

You'll probably want to tone the weapon down a bit to keep the radiation from the beam from frying the operator. (This wouldn't be nearly as much of an issue if the weapon were being fired by someone in powered armor.)

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  • $\begingroup$ How did you get the impression that your answer is closer to the laws of physics than Peter Masiar's? $\endgroup$ – celtschk Jan 11 '15 at 16:02
  • $\begingroup$ I'm only hypothesizing a gravity generator, not something that violates a conservation law. $\endgroup$ – Loren Pechtel Jan 12 '15 at 3:09
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This is similar to the answer of Peter Masiar, but not quite the same: I Think the best way is to use a positron beam. Positrons are the antiparticles to electrons. They are very lightweight, thus they'll not create a big recoil even if you pump out lots of them. And they'll annihilate with electrons in matter. Since the electrons are ultimately what holds the matter together, a sufficiently strong positron beam will effectively destroy matter. In addition, the annihilation will release a lot of energy, so anything surviving the annihilation will then be destroyed by the generated heat. As a bonus, it generates hard gamma rays, so you'll kill the victims even before the ray has eaten through the material all the way to them.

Main disadvantage: The gamma radiation goes in all directions and thus will probably also kill the shooter, so portable antimatter weapons are really only for suicide terrorists. Well, unless you manage to create a body suit that protects from hard gamma rays.

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    $\begingroup$ was thinking about similar problems with the relativistic shard gun: how do you prevent the weapon from blowing up the air molecules right by the nozzle? I was thinking to use a gamma ray laser as a path-breaker, leaving a momentary near-vacuum thought which a relativistic shard or a positron beam can safely go through. $\endgroup$ – Serban Tanasa Jan 11 '15 at 16:55
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Make a nuclear suitcase using Californium-252. Its minimal critical mass is 2,7Kg. Thats equivalent to a pretty heavy wallet at circa 10kg with all supporting devices. Caveat is that Californium is a powerfull neutron emitter and no lead in a wallet will block this and stay man-portable. You must accept that delivering it is a suicidal mission. Another caveat is price, Californium is not a naturally ocurring material. It is created inside nuclear reactors, so it is quite costly to recover.

References:

Californium

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  • $\begingroup$ I don't believe such a weapon is possible--while the neutron radiation is a problem the real issue is that it cooks itself. (And I think you need an atom smasher, not a reactor to get it.) $\endgroup$ – Loren Pechtel May 8 '15 at 2:34
  • $\begingroup$ Say that to the Davies Crokett rocket developers... $\endgroup$ – Jorge Aldo May 8 '15 at 16:06
  • $\begingroup$ The Davy Crockett got unjustifiably tarred based on a lack of understanding of how it would be employed. Yes, at max yield the warhead had a lethal range in excess of the flight range. That doesn't mean it was a suicide weapon, though--the threat was neutron radiation which is a direct path only threat. Fire the bomb and dive in a foxhole. It wouldn't need to be deep in order to provide near total protection for the crew. $\endgroup$ – Loren Pechtel May 9 '15 at 13:50
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If you are willing to create new element with a low critical mass you could have small nuclear explosives. If critical mass is a few grams it should still powerful enough to destroy a tank or a building, but would fit in a large caliber bullet (20 mm or so). Of course a burst from that would be pricey.

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