# Full body bullet resistant armour

The "people" wearing this are 10 times stronger than humans and have near unlimited muscular endurance so weight is of little (but not no) concern.

Their ballistic and gun technology is as advanced compared to the modern day as the modern day compared to WW2.

• RPM (Rounds per minute)
• FPS (Feet per second)
• Ammunition Capacity
• Ability to mass produce

The majority of the population who are regular humans (10 billion) wear US Marine Corps style armour when in the military.

• These are the "enemies" who will need to be unable to penetrate the armour.

However, the other people (will refer to them henceforth as "the OP") wear very flexible (negligible effect on movement compared to combat gear) armour that is:

• Nigh on indestructible even under heavy fire from armour piercing rounds out of a Barrett 50 BMG.

Do not worry about vehicular armaments as for reasons I cannot fit in a few lines those are not used in combat.

I need to know if there is a theoretical way to make this armour possible.

Ideally it should cover every part of the body.

• Comments are not for extended discussion; this conversation has been moved to chat. – James Aug 1 '18 at 21:33
• It seems that is a fair bit of confusion around this question. Please address the comments (that have been moved to chat) and organize your post so that is clear who the two teams are, what they can do, and what they have. Also be more clear on the outcome you want to achieve and we can get the hold taken off the question. – James Aug 1 '18 at 21:34
• @James Done, as stated all I did was make the bits nobody was reading bold and italicized and added 1 line. – P.Lord Aug 1 '18 at 21:40
• Armor that protects against the a Barrett shooting .50BMG just means that the enemy will find something bigger. – RonJohn Aug 1 '18 at 21:45
• It clearly states that vehicular armaments are not in the universe. Post a picture of you running around holding an anti tank rifle and I will gladly accept you are right. – P.Lord Aug 1 '18 at 21:49

Consider the energy in the bullet. When the bullet stops, where does the energy go? It could go into heating or breaking a piece of metal that it hits. Or the bullet could hit nothing, and its kinetic energy turn into heating of the bullet itself. That is my proposal:

Induction armor.

The principle will be the same as that used in induction brakes

A conductive surface moving past a stationary magnet will have circular electric currents called eddy currents induced in it by the magnetic field, as described by Faraday's law of induction. By Lenz's law, the circulating currents will create their own magnetic field which opposes the field of the magnet. Thus the moving conductor will experience a drag force from the magnet that opposes its motion, proportional to its velocity. The kinetic energy of the moving object is dissipated as heat generated by the current flowing through the electrical resistance of the conductor.

The possibility of stopping a bullet with eddy currents was discussed on the physics stack: https://physics.stackexchange.com/questions/238332/can-we-stop-moving-bullets-by-eddy-currents

Instead of a metal train rail moving past an electromagnet, here the electromagnetic field is produced by the armor and the bullet moves into it. The armor is composed of futuretech room temperature superconducting coils spread around the body. A small electromagnetic field is maintained at all times on each coil, and this magnetic field projects a small distance out past the body. https://physics.stackexchange.com/questions/478/is-it-possible-to-project-a-magnetic-field-at-a-location-in-space

When a bullet made of conductive material enters one of the fields it generates its own field opposing it, which is instantly detectable. A capacitor is discharged into the region of the armor generating the penetrated magnetic field. This in turn increases the eddy current of the incoming bullet. The strength of the field is proportional to the speed of the bullet, and so it is slowed most when moving fast, and less when moving slow. Red hot bullets moving slow might make it to the armor and gently bounce off.

You can make your room tech superconductor out of whatever you find plausible (I like metallic hydrogen mined from Jupiter), or you might decide it is unneccesary and make your electromagnets out of carbon fiber.

Benefits:

1: Individual cells can power up when they need to repel a bullet and stay in ready mode the rest of the time and so it conserves power.

2: The armor is not used up or damaged when it repels bullets.

3: Because it is powered it does not need to be as bulky as armor which uses mass to deflect bullets.

4: It is total scifi, but plausible scifi.

5: Magnetic fields this strong might have other effects which would be fun in the story.

Drawbacks:

1: If you are really in a storm of bullets, you might discharge all your capacitors and then you are toast.

2: You might run out of batteries or otherwise damage your power source.

3: Purely nonconductive projectiles (e.g. ceramic, rubber) will not be deflected at all.

4: A very slowly moving red hot bullet might gently bounce off the back of your helmeted head and fall down your collar.

• So this wouldn't stop melee aswell... that sounds perfect. Also I could solve the slow bullet and non-conductive by having ceramic and diamond/graphene coating. Also they are strong enough I can probably give then lots if batteries and maybe use a bit of magic (which somewhat exists). Thank you – P.Lord Aug 1 '18 at 2:10
• There wouldn't be enough time for the magnetic fields to slow down the bullets. – RonJohn Aug 1 '18 at 2:44
• Wouldn't this armor make it extremely hard to move around anything made out of metal? Because as you move your creating all this resistance force in everything around you. You would also run into issues if other people had similar armor, as well as around anything else powered using electricity. – Shadowzee Aug 1 '18 at 3:36
• It is an interesting question as to whether a diamond coating would be conductive enough to slow a chunk of iron oxide inside it. @RonJohn it is always good to read from you and if you are interested, look at the calculations on the linked physics stack question about this; the physicist calculates time needed with a field of given strength. – Willk Aug 1 '18 at 15:54
• @Shadowzee - good question. The eddy currents produced by a magnetic field are proportional to velocity. The faster something enters the field, the more it is slowed. Move slow and there is not much effect. All sorts of interesting stuff could happen with this armor. For example, if I fell spread eagled onto the deck of a battleship could my armor keep me from hitting hard? – Willk Aug 1 '18 at 15:56

Their ballistic and gun technology is as advanced compared to the modern day as the modern day compared to WW2.

The funny thing is, gun technology has plateaued in recent decades. We're at a point of refining designs that are known to work. Here's a few speculative things that never quite off the ground which might be in your world.

This is all centered around increasing hit probability and increasing the amount of ammunition one can carry.

RPM (Rounds per minute), FPS (Feet per second), Energy (Dispersed to target), Ammunition Capacity, Ability to mass produce

Two of these things are not like the others in terms of "advanced": energy and RPM.

The energy of your standard military rifle round peaked in WW2 and then dropped when everybody switched to intermediate rounds. Full rifle rounds like .30-06 or 7.62x54 deliver 3000+ J and are designed to still be effective at 2000 meters, but were found to be unnecessarily heavy and difficult to control in burst or automatic fire. Most shooting was found to be done at 300 meters or less, so everyone switched to lighter and more controllable intermediate cartridges like 5.56 NATO and 5.45x39.

Similarly RPM has generally dropped to allow for more controllable fire. Many battle rifles dropped their fully automatic settings and instead are single-shot or burst fire.

While we're certainly capable of producing monstrous rounds with high rates of fire, your average soldier probably won't be carrying them unless there's a good reason, like an arms race with advanced armor.

...armour that is nigh on indestructible even under heavy fire from armour piercing rounds out of a Barrett 50 BMG

Assuming this is the goal, 50 BMG packs quite a punch: 18,000 J. No current body armor will stop it, the scale ends at Type IV designed to stop armor piercing .30-06 with 4000 J. 50 BMG will go through 20mm of steel at normal combat ranges. Furthermore, designing body armor to stop one round is one thing. Designing body armor to stop a hail of rounds is another thing.

The surface area of your average adult human male is about $2 m^2$. At 20 mm thick that's 40 L of steel. At about 8kg/L that's about 320 kg of steel. If these folks are 10 times stronger, that's the equivalent of 32 kg. Heavy, but very good for full body armor. And that's just the upper end using steel. You can use whatever handwavium you like to further reduce the weight.

Small armor plates which overlap ingeniously, connected with smart, flexible handwavium, will provide flexibility yet never leave a gap.

As discussed above, if your average soldier has to hump around and fire 50 BMG their effectiveness and hit rate will drop dramatically. 50 BMG is already enormous with a tremendous kick. Soldiers won't be running around firing 50 BMG. It has to be either a specialty weapon, such as an anti-material sniper, or vehicle mounted. Carrying and firing anything much larger or hotter gets ridiculous.

Instead of ratcheting up the calibers and energy they'll probably switch to 20mm HEAT rounds and man-portable anti-tank weapons such as Javelin but shrunk down. While they'll be able to penetrate the armor, this will still greatly reduce the effectiveness of the average soldier as now they get a few slow shots whereas before they could carry hundreds of rounds. The armor will still have done its job.

• Thank you very much, yes my goal was to make these soldiers rare enough that the probability of an enemy army having enough heavy weapons to easily kill them was quite low. – P.Lord Aug 1 '18 at 19:58
• @P.Lord Oh, I got the impression this was every soldier. If they're rare they'll be dealt with like any other armored vehicle, just a lot smaller and easier to conceal. Most modern units have some sort of anti-armor capability either on them or on call (artillery, air support, nearby mobile anti-armor group). – Schwern Aug 1 '18 at 20:08
• More realistically Plate armor averaged about 2mm thick and weighed 50lbs, so you are probably looking at something closer to 500lbs (which will feel like 50lbs does to us), so about the same limitations on mobility. The real issue with plate is flexibility, solid plate would severely limit mobility even if they weighed nothing. – John Aug 1 '18 at 22:42
• @John Note that we're using kg. Well crafted plate armor is a good comparison as it was surprisingly flexible and distributed its weight well. Modern ergonomics would do even better. Plate armor weight varied between 10 and 50 kg. This figure also included padded undergarments, leather straps, and a mail coat all of which can be made lighter and more flexible with advanced materials. – Schwern Aug 1 '18 at 22:53
• surprisingly flexible is not the same as does not limit mobility, typically the metal makes up 75% the mass of platemail. so yes you could save some weight with modern materials but not much the density of steel is not significantly different. Consider also all parts of your system with end proportionally larger to account for the dimensional. The square cube law is the bane of creativity. – John Aug 1 '18 at 23:10

I don't think a full-body armor is possible. The reason I say that is you have to move, and anything that moves is weaker than something that doesn't. An analogy: in medieval times if you could get your sword between plates or inside the elbow/knee, you'd wound the other combatant.