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While the term Deflective Shield comes up in a lot of space science fiction, I wasn't thinking about plasma shields, magnets, or personal energy shields.

Instead, I was thinking about bullet-proof armor.

Most designs for bullet proof armor are based around absorption: the bullet's energy is absorbed by the Kevlar/bullet proof vest which has a high enough strength to stop it from killing the wearer. However, there aren't that many other ways to stop bullets: most tank and vehicle armor is designed around absorption. Composite, metal, and ceramic plating are all designed for the round to penetrate but stop in the armor plating. This means that given enough time and rounds, the armor would be shredded and a bullet proof vest-wearing user would die from internal bleeding.

But, what if instead of absorbing the bullet, the outer shell could deflect it?

Now, before someone brings up 50. Cal rounds, I do know that this is very theoretical, and would probably fail to get attention from DARPA. Yet deflecting bullets is possible: that was the idea behind old WW2 helmets: granted, they were useless against high caliber rounds, but they had the chance of deflecting lower caliber rounds.

With innovation in super-strong materials, and given a time of 100 years, could it be possible to create a kind of wearable outer plating, with a specific geometry and design, which could deflect low caliber rounds with minimal wear and tear?

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    $\begingroup$ Tanks today have no problem deflecting low caliber rounds without much wear and tear. $\endgroup$ – A. C. A. C. Nov 30 '17 at 23:23
  • $\begingroup$ Gimmie a sec... $\endgroup$ – WorldCraftTrainee Nov 30 '17 at 23:26
  • $\begingroup$ Ricochet depends on many factors like bullet/target shape, materials, spin, speed, etc. Note that even in ideal case there will be some amount of energy being absorbed by the target however small. $\endgroup$ – user6760 Dec 1 '17 at 5:03
  • $\begingroup$ It's a good idea to wait at least 24 hours before accepting an answer so that people from every time zone get a chance to weigh in. $\endgroup$ – sphennings Dec 1 '17 at 12:33
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    $\begingroup$ The reason body armor doesn't deflect bullets is because it's a really bad idea. How would you like it if your chestplate bounced a bullet up into your chin? Into the guy next to you? Into the control instruments of your vehicle (etc)? $\endgroup$ – Draco18s Dec 2 '17 at 22:27
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So, from what I'm reading, you want armor that deflects projectiles based on angled or sloped armor? While such armor has been in use in tanks and other armored vehicles since their first appearance on the battlefield, I don't feel as though you can quite as easily apply this principle to personal armor. Tanks fight in a predefined orientation to their opponents. They are never upside down, laying down, rolling about, etc. (At least hopefully not.) Thus, one of the big benefits of sloped armor is lost. Sloped armor increases thickness without increasing the thickness of the armor itself.

An example I found to illustrate my point.

Additionally, if I do deflect your projectile, where does it get deflected to? A metal plate on my chest deflecting bullets upwards directly into my head and neck is not exactly ideal. Though, I've seen this issue addressed by adding shielding in these areas.

Because I have no guarantee of what angle your projectiles are going to hit me from, I will need to make my armor thick everywhere or curved rather than sloped. Thus, I think we need to start thinking archaic and take a look at traditional plate armor designs.

Plate armor was designed not only to stop incoming blows but to deflect them as well. You'll notice a general trend in this armor towards rounded and conical shapes designed to deflect swings rather than take them head-on. Traditional plate armor, however, died due to the firearm. This was not because the design was faulty, but rather that available materials simply could not withstand the force of a bullet.

Now, in your question you mentioned this being 100 years into the future. It is not that we do not already have the materials to make this armor, AR500 for instance, it is a weight problem. However, your time frame fixes this for us. If you aren't opposed to the idea, robotic exoskeletons solve almost every problem there is when it comes to armor. They increase wearer mobility in the armor and essentially negate weight limitations.

While fictitious, I think this armor's design checks a lot of the boxes. It has generally rounded armor shapes, a shield around the neck to protect from bullets deflected off the chest plate, and appears to be assisted by an exoskeleton beneath the armor plating.

I would have placed this into the answer directly, but it isn't an https link, so I cannot. http://orig01.deviantart.net/920f/f/2009/345/a/4/space_vagabonds__assaulter_by_ukitakumuki.jpg

Now, with helmets, you can take more advantage of traditional sloped armor designs, as the orientation of the head relative to incoming fire is relatively predictable. Thus, placing a sloped plate of armor over the wearer's face is viable. Additionally, you may want to look into designs that incorporate a feature akin to a hinterschild to protect against deflected projectiles traveling into the wearer's neck.

An example of a helmet with a hinterschild. An example of a helmet with a hinterschild

Interesting note, this design carried over into more modern designs like the WW2 German stahlhelm.

Yet another example...

Hope at least some of this was useful. Have a good one.

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    $\begingroup$ I have to disagree with a minor part of this answer: Sloping armor does not provide additional armor thickness for a given weight, that's a common misconception. In order for it to enclose a given volume, a sloped plate of armor must be longer by a factor equivalent to the additional protection it provides, resulting in a net equivalency of protection-to-weight. Sloped armor is used primarily for its increased resistance to shaped charges (eg HEAT) and greater chance of deflecting high-velocity projectiles through geometry, but it doesn't save any weight. $\endgroup$ – Catgut Dec 4 '17 at 18:37
  • $\begingroup$ This is true, I probably should have found a better image. I simply sourced one that illustrated the primary point, that being the deflective capabilities and increased thickness. I may alter the answer to reflect this if I can find another image that illustrates this point. $\endgroup$ – DJKnarnia Dec 4 '17 at 18:46
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If you look at early modern body armor it was constructed of steel plates. An example of this would be the armor used by the outlaw Ned Kelly. Equipped with this armor he and his companions were effectively immune to bullets, at least the bits of them that were covered in armor in any case.

The primary problem with the armor was that it was extremely heavy, weighing in at 44 kilograms (97 lb). Such heavy armor would greatly decrease the combat effectiveness of any force.

Further advancements like kevlar and ceramic plates both provided protection against more energetic projectiles at a greatly reduced weight.

There is also the cost of the armor to consider. Newly developed alloys tend to be prohibitively expensive and may not be worth the added protection they provide.

It's also a good idea to remember that if the bullets are bouncing off the armor there is the risk of them hitting someone else. There will always be spots that can't be effectively armored and if high velocity bullet fragments are flying off you only to hit your companions it's probably not going to be appreciated.

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Deflecting is possible but it is highly dependent on the angle of the incoming bullet. If the bullet was to hit the armors surface at a right angle, it would impart all its force evenly across the surface and even the best armor wouldn't be able to deflect it. It would have to absorb all the force since there is no direction for it to go. You can always increase the hardness of the armor and the thickness, but there would be no way to deflect all shots from every angle with conventional armor used today.

Now if you increase the thickness or hardness of the armor, you can absorb more, but then the bullets just get larger, can use heat to soften the material and penetrate it and it sort of just becomes a cycle.

If you were to try used angled armor, where the surface of the armor is a set of ridges and so on, you would still end up exposing places ditches(not sure of the word) in the armor where a bullet wouldn't be deflected. You could also try applying multiple levels of armor, but then you are just increasing the effective thickness and weight of it.

This leads to your plasma shields, magnets or personal energy shields. I assume with plasma, you are attempting to destroy the bullet before it reaches you. You get hit with some molten metal, but it losses most of its penetration since its no longer a solid or much softer and deforms much more upon impact. With a magnetic, you are trying to alter the course of the metal bullet so it hits you at a better angle and can deflect off you. You would need a very powerful magnet do even alter the course a tiny bit, but the bullet won't be able to hit you head on, and hits at a much more favorable angle. The principle is to affect the bullet so it doesn't hit you at full force or hits you in a more favorable condition so that it cannot impact of of its energy on you in a meaning full way. The only way conventional armor can achieve this would be something akin to an advance detection system that would angle the armor plating to deflect bullets. But that wouldn't work for all angles due to the sheer operational volume a machine like that would need to be able to deflect all bullets.

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  • $\begingroup$ While I appreciate your honesty with deflection of bullets, the plasma, magnet, and energy shields were just a way so I could disambiguate from conventional sci-fi protections. However, you did bring up a good point using magnets $\endgroup$ – WorldCraftTrainee Dec 1 '17 at 5:31
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    $\begingroup$ Magnetic fields don't work well on non-ferrous metals. Most light rounds are copper jacketed lead. The heaviest rounds are depleted uranium. Neither of which respond to magnetic fields that could be generated on a person. Secondly, to bypass magnetic fields, spherical ammunition would be fielded. Magnets need an edge to grab onto( gross oversimplification), so spherical rounds would be ignored completely. $\endgroup$ – Stephan Dec 1 '17 at 14:17
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Your missing several very important points.

  • You never want to deflect a projectile because that is an uncontrollable event. You don't know where the deflected item will go, and it's just as likely to go somewhere you don't want it to go.

  • Any single substance hard enough to stop a bullet can be made into a bullet. That's basically the reason why people stopped wearing medieval plate armor (that... and it's really heavy). You might get around this with laminates... until someone figures out how to create a laminated bullet.

  • People need to walk and move. Deflection requires rigid surfaces, minimizing movement, making it easier to take advantage of unprotected weakness (aka, joints). It didn't take the modern military very long to discover that mobility was its greatest friend. Anything that restricts mobility (light weight and rigidity) can be overcome with mobility.

Therefore, the answer is at best, "yes, but only briefly, and that's assuming that anyone would want to give up the advantages of not using it."

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    $\begingroup$ You say Any single substance hard enough to stop a bullet can be made into a bullet. But actually you are not looking for the same material properties in bullet and in armors. For armors you are looking for something very strong and not too heavy. For a bullet, the ideal material would be not too soft and very dense. Many bullets are made out of lead (at least partially), which would be a very bad armor material. $\endgroup$ – Legisey Dec 1 '17 at 7:42
  • $\begingroup$ @frouil, that may be true, but it doesn't change the fact that you can make a bullet out of the same material you used to make the armor. But, in case my point was missed... any material you use to make armor deflective will soon enough be superceded by a bullet that can pierce it. $\endgroup$ – JBH Dec 2 '17 at 0:28
  • $\begingroup$ @frouil, let's turn the example around. Regardless what ideal elements you would like in armor, given that the OP is specifically looking for a material dense enough to deflect incoming bullets, one of the best materials available to penetrate said armor would be the material used to create it. $\endgroup$ – JBH Dec 2 '17 at 0:35
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Theoretically, yes. But it all depends on the caliber of the round and the velocity at impact and the materials of the armor. That said, there is current research in using non newtonion liquids as a body armor. They're soft and flexible, yet become hard on impact. As far as any form of weighty metal alloy armors, it's safe to assume that in 100 years, sufficient advancement in battery and small scale power generation will allow for powered exoskeleton armor suits.

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  • $\begingroup$ Answering whether it's possible, not whether or not it's practical. $\endgroup$ – Stephan Dec 1 '17 at 14:20
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If you can't deflect the bullet because of a bad angle, you have to be able to stop it so it will not kill you by punching a hole in your organs. However, the kinetic energy will still be absorbed by your body. This becomes problematic with heavier calibers. But I saw this article the other day. Its idea is to make a vehicle suddenly so heavy that it won't be blasted away by an explosion. Your question made me wonder if it would be possible to adapt it to a body armor. So if you apply this to your case, it might maybe be possible to:

  • Make an explosion to deflect the bullet, or to deviate it to a better angle
  • If a heavy caliber bullet is hitting you, but is not going to puncture the armor, it could help mitigate the blunt force trauma

And, bonus point:

  • Resist an explosion without flinching (including exploding bullets)
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Except for at shallow angles, it is better to absorb an impact than to deflect it.

If you absorb an impact the energy that you receive stopping the bullet is the momentum of the bullet.

If you deflect a bullet, you have to not only stop the bullet but then send it back with a large percentage of it's original speed. That is roughly 2x the bullets momentum.

Also, all of the acceleration from deflection (stopping and sending it back) must happen in a very short time. With absorption, that acceleration can be spread out causing less instantaneous stress on the armor.

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