7 ms·
Metal foam obliterates bullets
- aftbit 10y agoSweet - when can I buy level IV plates made out of this stuff?
- kibwen 10y agoNeat, though of course this raises the question: what would it take to engineer a foam-piercing bullet?
- userbinator 10y agoA bullet made out of metal foam?
- blisterpeanuts 10y agoTwo projectiles. First one explodes on impact and compromises the target. Second one penetrates the target.
- SEJeff 10y agoThis is exactly how a Soviet style RPG works. Ironically, it is also why the "bird cage armor" works so well against the RPG. Here is a picture of a Stryker combat vehicle from when I was in Mosul Iraq circa 2004ish: http://www.digitalprognosis.com/album/images/iraqpics/the-stryker.jpg http://www.digitalprognosis.com/album/images/iraqpics/the-st... The slats are smaller than the height of the outer explosive and prematurely detonate it. As a result, the penetrator simply bounces off the armor harmlessly.
- refurb 10y agoI thought the slats were to provide stand off distance for explosively formed projectiles. If the explosively formed jet forms more than a few inches from the armor, it's way less effective.
- Jommi 10y agoThe Vampir uses a tandem charge -- Two successive charges. The point of this is to counter reactive armor, which is designed to counter explosively formed projectiles. The "cage" slats can be effective against both.
- spatulan 10y agoThat's backwards. Explosively formed jets need space to form, so work better if they detonate a little distance from the target.
- refurb 10y agoNo, you're right. Explosively formed projectiles work best when formed a few inches from the armor. However, they have a sweet spot and if the distance is too far, they don't work. I figured that's what the cages were for.
- SEJeff 10y agoNope, we had them in Iraq before EFPs were really a thing (Thanks Iranain Quds Force for that). They were specifically for RPGs, which was one of the few things that could take out a Stryker without it. They even tried those Soviet parachute anti-tank grenades, but the Stryker is much faster than a tank and just moved away in time. That being said, the I'm sure this slat (birdcage as we called it) armor would help with that as well.
- grkvlt 10y agoI thought an RPG _was_ an EFP? The round is just a shaped charge with a copper liner that penetrates the armour. So the slatted armour stops both RPGs and EFP-based IEDs.
- hga 10y agoThe usual RPG with a HEAT shaped charge doesn't destroy by forging a penetrator that then potentially travels some distance to the target, it produces an intense, narrow jet that'll cut through a lot of material.
- spatulan 10y agoI though slat armour worked because RPGs only had a detonator in the nose, so unless you were very unlucky and the tip of the RPG hit a slat, the RPG would just jam itself between two of the slats.
- zardo 10y agoThen they make the new guy get them out with a pry bar.
- SEJeff 10y agoI saw that a few times actually, but only when the idiot firing the thing didn't pull the safety pin out of the warhead. The RPG is surprisingly safe when you neglect to remove the safety and will happily fire, but not explode in that circumstance. It was around the height of the Fallujah offensive we saw that happen.
- awalton 10y ago...which is already defeated by reactive armor, which you'd presumably layer underneath this ablative mesh armor layer to prevent this kind of attack. So, three projectiles in the same spot?
- dexterdog 10y agoBetter start with four so you're ready for the next shielding upgrade.
- JoeAltmaier 10y agoHow about 180? https://www.youtube.com/watch?v=xe-QP8s1ZJc https://www.youtube.com/watch?v=xe-QP8s1ZJc
- hvm 10y agoI've seen that before and I am so disappointed in the slow motion part. I wish I could see those bullets going one behind the other in a perfect 8 pattern.
- PhasmaFelis 10y agoI'm not an expert, but after some Googling, I think the bullet they're using there consists of a steel core inside a lead envelope inside a copper or copper-nickel jacket. So, at a guess, you'd want to replace the steel with something much harder and/or denser. Tungsten, maybe? I dunno. Depleted uranium would probably do it; I've never heard of it being used in anti-personnel rounds, but in cannon sizes it pokes holes in tanks quite nicely.
- extrapickles 10y agoThere are several rounds the military uses for small arms. 50 BMG and 5.56 NATO both have tungsten versions, though they are expensive, and hard for non-military to buy (when found, $50/rnd). Even the military does not normally issue them due to the cost, which is ~2-10x of a standard lead+steel round.
- hga 10y agoIndeed. The AP M2 round is the standard for National Institute of Justice (NIJ) Level IV rifle plate armor, but to the best I've been able to determine it's not a "serious" AP round, rather, it has a pill of relatively soft steel inside the normal lead and was developed in the run up to our involvement in WWII as much for the lower cost as the increased penetration. The latter of which was appreciated towards the end of WWII when I've read it became ubiquitous, and for example in city fighting one or more 20 round BAR magazines of this were used to knock holes in masonry walls between buildings. It was probably made the NIJ standard because it's the only somewhat common AP ammo a US cop is likely to go against on the street, as noted by extrapickles the serious AP ammo is a lot more expensive, and I'll add not really legal any more since there are some pistols that'll fire it. Notably, ESAPI military equivalent plates also aren't certified to stop anything more serious than AP M2, and I assume again for the same reason, there is or was a lot of surplus AP M2 ammo out there at one time. In the US civilian marketplace it's pretty much dried up as I understand it, e.g. see the few hits this GunBroker.com search finds and the prices: http://www.gunbroker.com/Ammunition/BI.aspx?Keywords=ap+m2 http://www.gunbroker.com/Ammunition/BI.aspx?Keywords=ap+m2 and I can't find any demilled bullets there or with a couple of minutes of Google time, whereas they were commonly available not too many years ago, certainly within the last decade.
- ceejayoz 10y ago> Last year, with support from the Department of Energy's Office of Nuclear Energy, Rabiei showed that CMFs are very effective at shielding X-rays, gamma rays and neutron radiation. Designers of spacecraft and lunar/Mars bases are likely pretty happy about this development.
- hyperion2010 10y agoHere's the doi for that paper: doi:10.1016/j.radphyschem.2015.07.003 Unfortunately I could only find the paywalled version here: http://www.sciencedirect.com/science/article/pii/S0969806X15300104 http://www.sciencedirect.com/science/article/pii/S0969806X15...
- Wingman4l7 10y agoThe subreddit /r/scholar or the Twitter hashtag #icanhazPDF can help out.
- M2Ys4U 10y agoTry putting the DOI into sci-hub.io
- ZanyProgrammer 10y agoAre there any potential downsides to this stuff? It seems too good to be true.
- patio11 10y agoIt's going to be expensive, may not meaningfully improve survival in actual combat situations, and may not actually be successfully deployed. How could this be extraordinarily effective at stopping bullets but not meaningfully improve survival? Fairly few American soldiers are killed by gunfire which directly strikes them; even fewer of these soldiers are killed by gunfire which directly strikes them on their armor. (This is partly because armor is fairly effective, partly because bullets are often non-fatal, and partly because medical care is very good.) Improved body armor may not meaningfully improve survival against other threats such as, for example, IEDs (once 60%+ of fatalities, down these days) or "the helicopter impacted terrain at a high rate of speed."
- PhantomGremlin 10y agoWhat about vehicle armor? Something like this would be a great improvement over the very heavy homebrew plating that our guys in Iraq and Afghanistan were forced to improvise on their Humvees? I.e. before MRAP type vehicles made it into the field. Lighter and better armor isn't just for people, it's also for vehicles.
- InclinedPlane 10y agoIt's actually very similar in a lot of ways to chobham armor, which is layers of ceramic and high strength metal in a composite structure. This seems to work similarly but with a more consistent mixture of both materials throughout a material, which might make it easier to manufacture and to work with, and possibly lighter as well.
- mrob 10y agoIf existing armor is already effective enough, improved materials means we can have the same effectiveness at lower weight. This could improve survival by increasing mobility or allowing soldiers to carry heavier non-armor equipment.
- colordrops 10y agoWould this be effective against micrometeoroids and orbital debris?
- patio11 10y agoThis presumably depends mostly on what your delta-V is. You can be wearing Epic Foam Platemail of the Whale +5 but if your orbital velocity is 7 km/s and you hit a 100g rock at the same velocity but going the other direction physics says you're about to have a very bad day.
- ben-schaaf 10y agoDelta-v is defined as "change in velocity", ie. how much a spacecraft can change its velocity. I think you're talking about relative velocity.
- tyre 10y agoI believe GP was referring to delta as in mathematics, which refers to difference and not necessarily change. So the delta between +7km/s and -7km/s is 14km/s. You are technically correct, though based on common usage patio11 got their point across.
- patio11 10y agoYep; appears I misremembered a long-ago physics class.
- paulsutter 10y agoI asked Dr Rabiei that very question by email yesterday, and she is working on it: "Let me start by saying that it is not a crazy idea and is actually what I have been working on recently. I even have a proposal in DARPA on testing the performance of the material at supersonic speeds. At this time, our data covers up to a speed close to 1Km/s as you mentioned. We have not tested the performance at higher speed and that is what I was hoping to conduct soon." (I asked if it could be used for space debris at 8-15km/s, and apologized for asking a crazy question)
- swehner 10y agoWhat if you shoot twice at the same spot?
- Tloewald 10y agoArmor of all kinds doesn't behave as well when hit a second time in the exact same spot.
- PhasmaFelis 10y agoIf you can reliably hit a target that small, you could just shoot the other fellow in the eye and not worry about armor.
- dredmorbius 10y agoNo. You're confusing consistency with accuracy. To hit someone in the eye, you've got to aim at their eye and land a round there. That is, accuracy at hitting a pre-specified target. To hit armour in the same location twice, you need either two (or more rounds) delivered consistently on whatever happens to be where the first round lands. It's a case where being a Texas Sharpshooter actually works (painting bullseyes around the bullet holes you just shot into a barn). A compound impactor with a leading and secondary round might work, for example. Difficult to package into a small-arms round, but possible. Keeping everything on the same impact point would be the crucial element.
- PhasmaFelis 10y agoAt that point, wouldn't it be easier and just as effective to use a single, larger round? .50-cal rifles already exist; no need to invent a big bullet that turns into two smaller bullets. (Unless you mean something that starts out the same size as the one in the video, in which case I can't imagine that two halves of a .30-06 would penetrate any better than one whole .30-06.)
- dredmorbius 10y agoThere's often an advantage do a dual-mode strike. That's how many existing armour-piercing weapons operate. E.g., tungsten-alloy armor piercing rounds: http://www.tungsten-alloy.com/armor-piercing.htm http://www.tungsten-alloy.com/armor-piercing.htm Another alternative, depleted uranium, relies on the exceptionally dense, and self-sharpening DU penetrator to defeat armour. Rather effectively.
- lolc 10y agoThe part about shielding radiation sounds dubious to me. I thought shielding from radiation was mostly about mass. How is that foam supposed to shield better than cast metal of the same weight? Maybe the "foam" deteriorates less?
- rdtsc 10y ago> I thought shielding from radiation was mostly about mass. Not for all types of radiation. Neutron radiation for example is absorbed better by a hydrogen rich material like say polyethylene. But then during absorbtion it would emit gamma rays sometimes, so metal shielding is needed as well.
- feelix 10y agoif you have something that interrupts the wave it blocks the whole wave. that's why the gauss on the microwave front door works yet you can see through it, because microwaves (the actual waves) are in the order of centimetres wide.
- dubyah 10y agoThey outperformed aluminum because of the iron content in the steel of the sphere walls or the matrix itself of the steel-steel composite metal foam. The composite metal foam that was comparable to lead utilized steel with higher concentrations of tungsten and vanadium.
- SixSigma 10y ago"foam" is the right way of thinking, it's not some thin bubbles of mostly air, from comment above : > The metal foam is made of 2mm-diameter hollow steel spheres in a stainless steel matrix (created using powder metallurgy).
- viraptor 10y agoI found the post-impact part of the video interesting. The article says "turn an armor-piercing bullet into dust on impact". But in the video, it looks like it turns it into a lot of metal particles / shrapnel. As a body armor it looks like it could be increase the danger to those around a person getting hit.
- fiatmoney 10y agoIn practice, you'd probably wrap the plate in fabric that would tend to catch the fragments, if nothing else because you need a plate carrier.
- jdfellow 10y agoThe effect is called "spalling" and current steel and ceramic armor plates are coated in a layer of rubber material to catch the fragments.
- personjerry 10y agoYes, I understood that as "turns bullet into shrapnel" which sounds rather problematic.
- madeofpalk 10y agoSales opportunity.
- PhasmaFelis 10y agoIt's hard to say for sure since there's only five frames of video post-impact, but it looks like those fragments are slowing down really fast. In the first couple of frames they're moving faster than the bullet was, but in the last couple they barely move at all. It seems possible that they're only dangerous within a foot or two of the impact point, which seems like a very acceptable trade-off for the benefits. Even if I'm wrong, unless it catches somebody in the eye, I don't think those little fragments could do worse than a flesh wound.
- visarga 10y agoAnd a big ass gun /
- deleted 10y ago[deleted]
- dang 10y agoWe detached this comment from https://news.ycombinator.com/item?id=11464777 https://news.ycombinator.com/item?id=11464777 and marked it off-topic.
- dkbrk 10y agoThis doesn't have much in the way of interesting details, you need to go to the paper for that. The armour is a composite sandwich, with boron carbide on the front face (a hard ceramic), followed by the metal foam, and either aluminium or kevlar on the rear face. The boron carbide layer blunts the bullet and distributes the compressive stress over a large area of the metal foam. The metal foam is made of 2mm-diameter hollow steel spheres in a stainless steel matrix (created using powder metallurgy). The metal foam deforms plastically under the compressive stress, absorbing the kinetic energy of the projectile (i.e. the spheres get crushed). The backplate provides tensile strength and stops the foam from tearing apart due to residual tensile stresses.
- chillydawg 10y agoPresumably very expensive and one-time usable. I guess that's true of most types of armour anyway.
- coldtea 10y ago>and one-time usable It's not like you want it to save your life more than once...
- hga 10y ago"Once" though is one event, which might include your body armor getting hit more than once. If you're up against automatic weapons, especially the more stable heavy ones (e.g. belt fed General Purpose Machine Guns), a plate getting hit more than once in one moment is fairly likely. The military SAPI and ESAPI standards require stopping 3 hits: https://en.wikipedia.org/wiki/Small_Arms_Protective_Insert https://en.wikipedia.org/wiki/Small_Arms_Protective_Insert
- rmelly 10y agoDragon Skin (https://en.wikipedia.org/wiki/Dragon_Skin https://en.wikipedia.org/wiki/Dragon_Skin) claimed to withstand multiple hits without loss of performance, although there was some controversy around it. https://www.youtube.com/watch?v=aYaSRIbPWkM&nohtml5=False https://www.youtube.com/watch?v=aYaSRIbPWkM&nohtml5=False
- redacted 10y agoI did modelling work for a group researching metal foams in my past academic life. Very interesting stuff with a lot of applications if the manufacturing processes can be nailed down. Our funding was a mixture of European Space Agency and a car conglomerate: light armour for space vehicles and crumple zones / reinforcement respectively (less acceptable to research military applications in EU in my experience).
- fudged71 10y agoI'd love to chat more about these materials, could you message me? tom[at]printtopeer[dot]com cheers!
- jp555 10y ago"showed that CMFs are very effective at shielding... gamma rays..." Really? That would be quite an achievement.
- perlpimp 10y agohttp://www.youtube.com/watch?v=wfFcs25KmMc http://www.youtube.com/watch?v=wfFcs25KmMc more about the inventor.
- camoby 10y agoThis reminds me of an old Mythbusters experiment where they showed that covering a wall in the same stuff people put in the bottom of their trucks can protect the wall from explosions.
- guard-of-terra 10y agoI read about it as a child. On earth, molten metals readily lose gas by the force of gravity, but in space, you can easily make metal foams that will be very strong and light. Sounds like a good material for spacecrafts. Also, how about glass foam? I imagine you can blow large and cheap hulls from foamed molten glass.
- onetimePete 10y agobubbling asteroids :)
- tim333 10y agoLooking at the ammo channel for I think the same ammo the results don't seem that remarkable. The foam article quotes "less than an inch", the ammo test article has about 1 inch for mild steel and 0.319 inches for AR500 plate http://www.ammochannel.com/30-06-30-cal-m2-ap-armor-piercing/ http://www.ammochannel.com/30-06-30-cal-m2-ap-armor-piercing...