“Off switch” makes explosives safer | Hacker News Reader

“Off switch” makes explosives safer

physics.aps.org

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Ah, Los Alamos, exactly what I though. What this really is, is an external manifestation of the eternal struggle between the military, which wants the weapons to detonate on time every time, and the safety-minded engineers and politicos who would rather eat an occasional fail than start a nuclear war. The safety people being the engineers tend to keep finding new ways to be safe and applying them without necessarily securing the DoD’s permission, but they don’t always work out the way the engineers intended. For a period of time, there was a piece of cobalt tape on Trident missile warheads that would ensure they fizzle unless removed. Except the adhesive dried up and then the release force exceeded the torque of the motor intended to remove the tape, so something like 75% of the Trident missiles were duds for years.

Read Eric Schlosser’s Command and Control. Absolutely fascinating.

> the military, which wants the weapons to detonate on time every time

Well, the military sure is also concerned about avoiding non-intentional detonations due to accidents or by being hit by enemy fire. E.g. the IMX series of explosives that have apparently started to replace TNT and Comp B in some applications.

https://en.wikipedia.org/wiki/IMX-101

As we've seen in Ukraine, sensitive munitions kill a lot of tank, IFV and artillery crews.

Part of that is the design of Russian tanks as well. Because of the design of the autoloader they use the turret has to sit on top of the shells in Russian tanks. Other countries use a human loader that puts the shells in an armored box with intentional weaknesses so any fires or explosions have a safer direction to expand than into the crew compartment.

Even with the compartment design, surely it would be preferable that the munitions don't all explode if hit.

And the same thing holds for the depot where all those explosives are stored before being loaded onto vehicles. https://www.cnn.com/videos/world/2023/01/04/russia-weapons-a...

If they're not already filled in the magazine you're increasing the time it takes to reload the gun dramatically and adding the need to haul all the water around required to activate all the ammo. Doesn't sound like a great option to me.

Sure, this particular solution might not be very practical for that use. Such is the nature of research.

I can't find anything on Google about cobalt tape or Trident missiles — but there was a cadmium wire in the W47 warhead, the one for Polaris missiles, which has a story very similar to yours:

- "Because the test ban prohibited the testing needed for inherently safe one-point safe designs, a makeshift solution was adopted: a boron-cadmium wire was folded inside the pit during manufacture, and pulled out by a small motor during the warhead arming process. Unfortunately, this wire had a tendency to become brittle during storage, and break or get stuck during arming, which prevented complete removal and rendered the warhead a dud. It was estimated that 50-75% of warheads would fail. This required a complete rebuild of the W47 primaries.[7]"

https://en.wikipedia.org/wiki/W47?useskin=vector#Reliability...

Yeah, looks like boron coated cadmium tape. The relevant excerpt from Command and Control...

> To avoid the embarrassment of relying on a Los Alamos design, Teller used Livermore’s new core but added a mechanical safing device to it. A strip of cadmium tape coated with boron was placed in the center of the core. Cadmium and boron absorb neutrons, and the presence of the tape would stop a chain reaction, making a nuclear detonation impossible. During the warhead’s arming sequence, the tape would be pulled out by a little motor before the core imploded. It seemed like a clever solution to the one-point safety problem—until a routine examination of the warheads in 1963 found that the tape corroded inside the cores. When the tape corroded, it got stuck. And the little motor didn’t have enough torque to pull the tape out. Livermore’s mechanical safing device had made the warheads too safe. A former director of the Navy’s Strategic Systems Project Office Reentry Body Coordinating Committee explained the problem: there was “almost zero confidence that the warhead would work as intended.” A large proportion of W-47 warheads, perhaps 75 percent or more, wouldn’t detonate after being launched. The Polaris submarine, the weapon system that McNamara and Kennedy considered the cornerstone of the American arsenal, the ultimate deterrent, the guarantor of nuclear retaliation and controlled escalation and assured destruction, was full of duds. For the next four years, Livermore tried to fix the safety mechanism of the W-47, without success. The Navy was furious, and all the warheads had to be replaced. The new cores were inherently one-point safe.

You might want to read a bit about the design of WWII-era conventional bombs, or WWI-era artillery shells, or magazines in sailing ships, or ...

Militaries that have wanted to win (vs. blow themselves up) have been laboriously working to make sure that explosives do not explode when they shouldn't for centuries.

They're pretty good at it, too.

You can set RDX (the explosive in C-4) on fire, and it'll burn, not explode. Even small arms fire won't trigger it.

> who would rather eat an occasional fail than start a nuclear war.

A nuclear detonation on allied territory that originates from your own weapons isn't going to cause a nuclear war. The point at which a nuclear warheads needs to explode is "when it's about 1km above it's target". The war is already happening if it got anywhere near there.

I work as a drilling and explosives engineer at an active mine. I don't see the value-add here, to be honest. Modern explosives management (in a mining context) is extraordinarily well managed. ANFO (ammonium nitrate fuel oil) which is the dominant explosive type is so hardy that you can hold a flame to it or shoot it with a firearm and you will not succeed in detonating it. 3-stage explosives systems (detonator-->booster-->ANFO) is a fantastic way of managing risk. Detonators cannot set off ANFO, the booster is required middle step.

I won't pretend to have studied the phenomenon, but the only undesired detonations I've heard of so far in my career have all been a result of detonators inadvertantly set off. The latest examples I know of being wireless electric detonators (which are being phased out as they're inferior to electronic detonators,which offer more protection) set off because of malfunctioning devices emitting the required radio waves, yikes! The explosion in Beirut can hardly be considered in the same category as that was an explosion of explosive precursor, effectively unrelated.

I'm struggling to understand what the target market for this type of innovation is. Is it bulk transport of explosive materials between the manufacturer (like Orica or Dyno-Nobel) and individual mine sites? That part is already extremely safe. You'd need specialized equipment at each mine to mix the water back in, with maintenance and calibration requirements. There's no way this could be between the surface and the holes into which the explosives are loaded, for so many reasons. I also wonder about the consistency and quality of the resulting product, the balance for these explosives is already such a tuned and precise.

There are a number of very high-profile accidents with ammonium nitrate[0].

It can be detonated without a detonator+booster, although the mechanism isn't well understood, seems like in a fire it can form more volatile compounds with soot and other contaminants.

Still, I would agree, it's generally a very safe compound. It's handled every day in enormous quantities.

[0]: https://en.wikipedia.org/wiki/List_of_ammonium_nitrate_disas...

Good call out. It’s generally very safe, but when it goes wrong, it’s catastrophic. Grandparent’s comment feels out of touch - looking at it from another lens: flying is generally safe but there is a certain unique set of circumstances that cause catastrophic failure and plane crashes. Do you just ignore the process and materials improvements because that certain set of events is super rare? No, you include the improvement in your process. That attitude has allowed FAA and Airlines in general to become much safer over the past 40 years (1).

1: https://www.bts.gov/content/us-general-aviationa-safety-data

Good counter, I suppose it's irresponsible to act as though ANFO / ammonium nitrate alone is fully innert. What you'll notice looking through that list though is the vast majority of those accidents are related to fertilizer production. It seems silly but partly it's a volume matter, partly it must be an industry attitude. When people think of mines, explosives come to mind. There's relatively few companies controlling the worlds' supply chains so good practices are widespread. The same cannot be said for fertilizer products though, given the ubiquitous use, high tonnage, and lack of consolidation and awareness.

Safe until filled with water is probably not that useful. Water is everywhere and things in military use tend to get wet.

There are binary explosives now, where both components are nonexplosive by themselves. Those are used commercially, for road work and such.

Depends how it's designed. If it needs to be drenched to be explosive, then simple drains holes at the bottom keep it safe.

Plug the holes and fill with a hose when you want to use it.

Yeah, damp or drizzle isn't going to activate these, if I'm understanding them correctly. If anything, I was wondering at first how they were going to deal with air bubbles (but I suspect they're fine as long as there aren't too many).

Ah, yes, but think those olive drab steel Ammo Cans. These are a simple, cheap, tried-and-true tested method of preserving military supplies; heat proof, water proof, dust proof, (somewhat) nuke proof, biological proof, and fire proof.

Very off-topic, but I have to relate this incident. I was hitchhiking up the US East Coast in the spring of 1983, and stopped in Washington, D.C. While there, I picked up an ammo can from a Army Surplus store (it seemed cool, never used it for anything, still have it).

While walking around DC I met a guy who worked in the Capitol, and he invited me into his building. At the entrance, there was a security post checking bags. They patted down the sides of my backpack, but never even looked inside the ammo can.

I guess it was too obvious.

I believe this is more intended for civilian (mining, demolition) or combat engineering explosives than it is for actual armaments, where having to have lots of watertight storage available to store your low density explosives isn't that big of a concern.

> where both components are nonexplosive by themselves.

in plenty of binary explosives the components are explosive, but less so and even harder to set off.

> They used a 3D printer to produce......

Wow really upping the pucker factor in one of my favorite hobbies.

Tip: Don't heat the print bed when printing with TNT.

Its melt castable and not the easiest thing to get going, so you probably could print with it.

Probably would also give you megacancer.

Apparently TNT melts at 80°C. If we are to believe [1], liquid TNT is quite sensitive while confined, and gets more sensitive the hotter it gets, but if allowed to flow it's actually very difficult to set off. Autoignition happens at about 265°C, according to [2], and again according to [1] temperature doesn't play a major role in the sensitivity of solid TNT.

So I guess don't heat the print bed too much, and if you do make sure the TNT can flow freely until it solidifies again, and you should be fine.

Edit: and as nibbleshifter suggests, you could print with it given these parameters, just be careful with the TNT in the hotend.

1: https://www.cdc.gov/niosh/mining/userfiles/works/pdfs/itass....

2: https://www.govinfo.gov/content/pkg/GOVPUB-C13-36e8df81dfe03...

Would be pretty cool to be able to order custom shapes SendCutSend style. Would be real useful in demolition and construction settings in cases where you don't do enough of a specific job to buy or rent expensive non-explosive equipment to do it.

That's easy with plastic explosive. It's a putty like consistancy. It's explicitly designed to be sized and shaped in the field.

There are to this day many an explosive product that is cast by pouring molten explosive material into the shell. In some cases, poured by hand from jugs.

Steady!!!

I recently read about the Oppau disaster (https://en.wikipedia.org/wiki/Oppau_explosion ), where the workers were getting bored with using pickaxes to break up a huge pile of compressed ammonium sulfate and ammonium nitrate, and decided to use dynamite to loosen it up. What could possibly go wrong?

The crazy thing about that is they had broken up the Ammonium Sulfate/Ammonium Nitrate mixture thousands of times before the incident. It was incredible that they managed to do so for as long as they did. All it took was one day where the mixture wasn't mixed very well and everyone dies. An industrial version of Russian Roulette.

It was considered safe at the time because the mixture is usually not very sensitive. Hindsight is 20/20.

> It was considered safe at the time

I know they thought so, but also wonder why they thought so.

Yes, https://en.wikipedia.org/wiki/List_of_ammonium_nitrate_disas... says:

“the factory had used this method of disaggregation over 20,000 times without incident”

But it also mentions what happened less than two months before the Oppau explosion:

“July 26, 1921: workers tried to dislodge 30 tonnes of ammonium nitrate that had aggregated (solidified into one mass) in two wagons. When mining explosives were used on this solid mass the wagons exploded and killed nineteen people”

Separation between the two disasters is about 1,000 km, but both were in Germany. Surely, they must have heard what happened there. Why didn’t that make them reconsider using this technique?

And why didn’t that second explosion prevent what happened in Tessenderlo in 1942 “An attempt to disaggregate a pile of 150 tonnes of ammonium nitrate with industrial explosives killed 189 people and wounded another 900”?

That’s about 300km, as the crow flies, from Oppau.

Famous saying in Safety Engineering: everything that can go wrong will go right most of the time.

You wouldn't download a shaped charge

Anybody want to go to http://thingiverse.com and search for "shaped charge nuclear detonator"? Extra points for doing so with cookies enabled.

> in the military world, for example, over 500 accidental explosions occurred at munitions sites between 1979 and 2013, according to a survey

This is false in the US and NATO. The study they site is counting incidents in Albania, Bosnia, Croatia, Montenegro, Serbia, and Slovenia.

https://www.jstor.org/stable/resrep10678?seq=2

Water has a tendency to get into places it's not supposed to. I'd hate for a roof leak to cause a warehouse explosion.

Presumably there would be more safeguards in place than just the water. All the safeguards that currently exist could still be used.

My understanding is that right now 'our explosives got wet' fails safe. This would invert that situation.

Loved the read. I know I am on a list somewhere now, but I don't care. This is what HN is all about. Interesting knowledge.

safe unless submerged in water! Great. It's of course incredibly unlikely for unattended store rooms to ever be exposed to this unusual substance that occasionally falls from the sky and fills up entire towns.

Those are the names of Javascript libraries right?

If such a thing can be scaled and made reliable, the implications are staggering.

Imagine ammunition that fits in existing firearms and is fully self-contained, mixing into a viable round only when entering the chamber. And then made “smart”, such that it can be geofenced and therefore refuse to mix near schools or stadiums or government buildings, etc.

If this becomes possible, then all traditional ammunition may become legislated or litigated out of existence.

That would require a battery, a GPS chipset, and either a sizable database or a cellular radio, in the base of every cartridge.

I'm pretty sure ammo makers aren't shaking in their boots on this one.

You could probably do it with something like Bluetooth LE in the bullet. You'd need some sort of base station, worn on a belt loop or something.

Binary explosives certainly exist so it should be in theory possible. Not sure how well they "scale down" though, and I don't know if any have a blast velocity low enough to be workable. I'm not a gun guy, really, outside of my interest in naval warfare. 16" shells have slightly different design params though.

Actually, thinking about it more would the barrel act like a faraday cage?

It would make considerably more sense to use standard ammunition and conditionally release the firing pin based on logic in the firearm, but to be clear this is all still well within the realm of flagrant silliness, to the point where if n-gate (pbuh) were still around this thread would probably qualify as bait.

Ammo is really really safe as it is. Ammo doesn’t accidentally go off. The modifications you’re talking about would go on the gun, not the ammo.

That "gun digitally safed" concept was tried before and pretty roundly rejected. Even electrically ignited primers were a market failure. Gun people are more paranoid than even InfoSec researchers when it comes to tech in their toys. If you truly believe your guns are for self defense, it makes a little more sense.

I haven't heard of any electrically ignited primers that made it to market, but every attempt that's gone through military trials have had abysmal reliability.

See Remington EtronX https://www.youtube.com/watch?v=8qP6Q9ZEsEo (but it obviously was a commercial failure)

Interesting. I missed that one.

The M61 Vulcan (https://en.wikipedia.org/wiki/M61_Vulcan) in common use by the US Military for many years is electrically fired.

Forgotten Weapons on YouTube has a video on the Armatix iP1 "smart" pistol, the technology behind it, it's development and why it was a commercial failure.

1. Why would you install all this into the ammo, rather than the gun? Any mechanically-inclined idiot with a garage workshop can make his own ammo.

2. Guns are a political problem, not a technological problem. If you want to reduce gun violence, ban handguns. If you want to reduce mass shootings, ban handguns and semi-automatic long guns. If you want to stop a dedicated idiot with a garage workshop from building his own pipe shotgun that he will use to execute an MLM cult leader, you can't, he's going to do that regardless.

I'm not sure banning semi-automatic weapons is an effective way to stop mass shootings. California has one of the most restrictive semi-automatic weapon bans in the country and it has one of the higher rates of mass shootings. That seems to be pretty good evidence that this policy is restricting people who care about the law from possessing these weapons and not the people actually committing the crimes.

California's surrounded by 49 other states, most of which have no such restrictions, and does not have any border controls with any of them.

The formula of access changes substantially when you don't have opportunities for jurisdictional arbitrage.

Criminals don't sit in a pentagram and magick weapons up out of thin air, they source them (legally and otherwise) from legitimate owners. A few of them are also legitimate owners, who choose to use them for crime.

It would seem, then, that those surrounding states should have even higher per-capita mass shooting rates than California, given they have a higher concentration of those sorts of weapons. They don't. In fact the states surrounding California are substantially lower.

It seems apparent that this strategy is both misguided and ineffective.

You played a sleight-of-hand, by conflating mass shootings with gun homicides in general. I'm talking about both, with a bigger emphasis on homicides overall.

California is #44 for gun homicide rates, and is significantly lower both on this metric, and on gun ownership than than its immediate neighbours.

Speaking of firearm homicide rates, #1, #2, and #3 are Mississippi, Wyoming, and Louisiana, [1] all of which have gun ownership rates that are double-to-triple that of Cali.

'Immediate neighbour' isn't a relevant term to this. There are no border checkpoints anywhere between the lower 48. Practically speaking, access to firearms is set by the availability of firearms in the most permissible state. Illegal guns don't appear into existence on their own, they start life as legally purchased guns, that are then sold to criminals, or are stolen by them. This is especially prevalent on the East Coast, where 3/4 guns used in New Jersey and New York crimes come from out of state.

[1] https://www.cdc.gov/nchs/pressroom/sosmap/firearm_mortality/...

I'm not the one playing sleight of hand here, this whole comment chain is talking about mass shootings. You're moving the goalposts to a subject nobody but you is talking about.

If you really want to do something good, don't ban semi-autos, or long guns at all.

Make it way harder to get a pistol. That's what's used in the vast majority of murders.

Those two mass shootings in California earlier this year? Both pistols.

I also think that concealed carry should generally be banned for most civilians, and open carry legal.

My views on guns tend to generally annoy both sides...

I won't go so far as to say I'm on your side, but it's a valid way of looking at the issue. It's the statistical approach - target the biggest part of the problem.

IIRC handguns are used in 75% of firearm deaths from all causes (homicide, suicide, accidents).

> IIRC handguns are used in 75% of firearm deaths from all causes (homicide, suicide, accidents).

kind of a distorted figure there because suicide dominates by a wide margin, and gun availablity doesn't change the suicide rate. e.g. when controlling for latitude you get similar suicide rates in places without guns, people just use different means.

Guns have by far the highest success rate.

Yet the suicide rate in the US and UK-- where there is more or less zero access to guns-- are essentially the same, especially after correcting for age and latitude.

It's not that wide of a margin, and different aggregations (geographic region, year, etc.) see a more even 50/50ish split;

https://www.pewresearch.org/fact-tank/2022/02/03/what-the-da...

Interestingly enough, this was the original intent of the NFA - banning pistols. Eventually we ended up carving out an exception for allowing pistols but kept the restrictions on short barrel rifles, which were included only so people wouldn't turn rifles into pistols after they were banned. The law is a funny thing sometimes.

Generally, I agree on pistols. The whole point of the second amendment is that people should be free to defend themselves from tyrannical governments and other threats. Handguns are much less useful in that capacity than long guns. Handguns are excellent if you need to conceal a weapon but I'm not sure there is a constitutional case for that.

My concern about banning pistols is that it won't stop there, though - see current Canadian gun legislation.

Liquid propellant could be useful in varying the amount used per shot. In some large guns (ship guns mainly) you put bags of propellant in the gun and you're limited to whole bags. If you need a half bag you have to vary your aim to get the desired target. It sounds very difficult but might be worth it for space savings and for not having explosive ammo laying around.

As for making guns stop working in certain places, why wouldn't crime just target those places? My walk home passes malls, a school, government buildings, and two stadiums. Why would I accept a defensive tool that didn't work most of the time?

If we make gun ownership too onerous we risk people ignoring the law altogether - after all the risk of being injured is more serious than being caught defending yourself - which would increase the black market and aid criminals.

It's a little surprising to see all these replies with none of them mentioning that this discovery applies to high explosives, which aren't used in small arms ammunition. Ammunition uses propellants, which burn quickly (deflagration) but not as quickly as high explosives (detonation); the latter would burst the firearm. Therefore this discovery is unlikely to have any relevance to small arms ammunition.

There was at one point some research done on seeing if artillery could replace propellants with high explosive. From what I understand it concluded that is was completely impractical.

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