Remote Sensing Bombs Could Stem Terrorism

If you understand technology, there were a lot of things hard to explain on Star Trek. Transporters, doors that were smart enough to open unless you hit them during a fight, and the universal translator all defy easy explanation. But one of the hardest things to explain were Mr. Spock’s sensors. From the ship or with a tricorder, Spock could sense at a distance just about anything from chemical compositions, to energy, and even the presence of life (which, today, at least, is difficult to determine even what that means).

Remote sensing would have a very distinct use in today’s world: finding terrorist bombs earlier. A recent article published on New Scientist by [Debora MacKenzie] points out that stopping attacks like the recent one in Brussels is difficult without increasing congestion. For example, putting checkpoints at doors instead of inside transit stations is common in Asia, but causes lines and delays.

detecThe United States has used ion mobility spectrometry (IMS) to detect explosive traces on swabs (using machines like the one on the left). However in the early 2000’s they experimented with a version of the device that used puffs of air to determine if people had explosives while they passed by the machine. By 2010, officials decided the machines broke down too often and stopped using them.

Remote Sensing in Practice

According to an expert at Rand Corporation, remote sensing is likely to employ imaging or sniffers. However, imaging solutions are easy to fool since a bomb can take the shape of an ordinary object. Sniffers, including biological sniffers (known as dogs), are harder to fool. The problem is that deploying thousands of dogs to cover the world’s airports is difficult.

A security firm, Morpho, is working on something they call “the tunnel of truth”–pedestrians walk through the tunnel, and it scans them with multiple sensors, including things like IMS, facial recognition, and even analysis of eye movements to detect nervous people. To Sci-Fi fans this sounds like the public transportation scanning from the movie Total Recall which is where the image at the top of the post comes from.

The Sounds of Micro Explosions

Lincon Laboratories has another remote answer. Dynamic photoacoustic spectroscopy (see figure below) uses a laser to sense remotely gasses and aerosols. Looking for the right signature can allow that device to find explosives from a distance (up to 100 meters away).


Curiously, the system works by listening for the sounds of tiny detonations. The laser uses a frequency that vaporizes molecules found in explosives, and the device listens for the nearly undetectable sound of that event. Researchers claim it can detect 200 nanograms per square centimeter of material on a moving car door handle.

There are other laser-based systems including G-Scan, which uses Raman spectroscopy and a green laser. Some systems employ microwaves. Everyone agrees that a system that could detect explosives quickly and without many false positives from a distance would be a good thing. In fact, some systems could even detect bomb making facilities and stop a bombing before the bomb even exists.


At Hackaday, we often talk about hacking for the greater good. We have a large community of smart people. Maybe we need to start thinking about this problem. A simple open source explosive detector that worked could be a game changer, not only against terrorism but perhaps solve other problems like land mines.

I’m hoping the comment section will generate some ideas on how this might work. Don’t just think of cameras and spectroscopy. Think outside the box–that’s what our community is best at doing. A good enough idea might attract some interest and maybe one day soon we’ll feature a project that can detect suicide vests or other dangers to innocent people. That’s a hack that would make the world a better place for everyone.

84 thoughts on “Remote Sensing Bombs Could Stem Terrorism

  1. I got TSA’d at Denver last year after I failed a ‘swab’ test while waiting in line. After a thorough but not embarrassing search they decided that this Brit was no danger to anyone.
    “Sir, have you handled explosives or weapons while you have been in the United States?”
    “Nope, but I did take the city bus here”

    1. I had my balls fondled by a young negro with a big afro when leaving L.A. airport to fly to central America. Not knowing the local customs I just assumed it was a Californian customs custom and not not complain.

  2. Yeah. Remote sensing explosives for HaD readers. I’m sure some guy in his basement is going to come up with the answer. First you need EXPLOSIVES, the possession of which is oftentimes ILLEGAL without the proper paperwork.
    SO now you need expensive EXPLOSIVES on hand and expensive legal PAPERWORK.
    And to be useful you need a multitude of explosives about because they all have differing chemistry and bad guys, well damn it, they like to use different stuff depending on wildly varying factors, often times home made stuff that is rather unstable and dangerous, much like HaD readers themselves. This has no place good to go…

    But the humble honey bee may be the answer. They can be trained to “lick” the air looking for drugs and the like by using a little bait and switch with sugary treats and the substance you are interested in finding. Some lab made a sniffer gun of sorts that inhales air and then lets some bees inside do a bit of a survey, if the survey is in the positive above a certain threshold, then they likelihood is good there are materials of interest to be found. depending on which cartridge of trained bees you install, you can detect all sorts of stuff. But you need to get a good sample of air, which would go back to puffer machines.

    But some HaD reader blasting even trace samples of explosives with lasers and getting correlated data is slim to none unless they work for a company or government entity with a lot of $$$

    1. I don’t know. I have found people are always more resourceful that you think. I’ve been told that we’d never see a computer in the home, for example. Or that SMD would kill homebrewing.

      Granted, maybe you don’t want to start buying explosive components to your workshop. But I’m not willing to rule out that someone out there who reads Hacakday doesn’t have some reasonable ideas. Could we drive it all the way out to a useful product? Maybe not without some help from an institution, but the one way to assure we won’t do it is to not try at all.

      Go back to Mr. Spock. If you had a tricorder, it could probably find bombs. But it probably wasn’t developed to find bombs at first. If you think big, you never know what’s going to happen.

    2. It has been proven that in the recent terrorists attacks, bombs made with acetone, H2O2 and acid (the one you can find in supermarkets) were used. So any hacker in their basement could theorically make one.

      But don’t, you need to know the exact dosage and when you need to add the good ingredient so… Please don’t try this at home !

      1. I was just going to say, many terrorist bombs (at least according to the reports) are home-made. The US Army imanual for improvised munitions is freely available and plenty of people graduate with chemistry degrees.

        OnceOnFire is assuming that criminals and terrorists get their materials through legal means all the time. That kind of thinking is EXACTLY what keeps people from solving this problem.

    3. Paperwork would probably be needed, but small test samples could be made available. I once worked on a modular robotics project with a gamma detector and we had Cs-137 samples available for calibration and testing. I assume some small amount in the realm of the desired detection range could be made available. Or for the more fully vetted homebrew solution hacker perhaps a nice sample case could be provided with a grant large enough to work out of the basement but small enough that they’re saving money over the traditional funding routes.

    4. Yeah, I think this would better be acheived by “experts” to be honest. People who can more easily get access to the required explosives for testing and the information about what types of explosives and realistic scenarios to test. Also, as much as I’m for open source, I don’t think making the details of how any new system works publically available would do anyone any good. I mean, there will always be ways to thwart and bypass any detection systems and the less that is known about how they work, the harder it will be to do that.

  3. TATP (Triacetone Triperoxide) detector exist and could/should be used everywhere. I don’t know why authorities doesn’t use them in public transportation, they know TATP is the explosive of choice for terrorists, they use it as a primary explosive but also to detonate other explosives as well.

    I’m more an hardware/software guy and not very good with chemistry, but I think we should be able to prevent an attack like the ones we saw in Europe and Middle East recently without being intrusive at all. (CA)TSA couldn’t prevent this kind of attacks in an airport, and nothing is preventing anyone to bring this nasty explosive in public transportation, in a stadium or in a crowd.

    Detecting TATP:

    1. I have a special idea, one appropriately only HaD commenters can come up with:
      Take those guys that return from syria, and if they rent an apartment and carry in large quantities of acetone and such then ban them from entering the airport!

      Oh and this is serious stuff so no arduino, instead use a raspi zero to ban them (after first adding a USB hub).

    2. This is much more difficult than you think. The “easy” part is detecting explosive. The hard part is getting enough of a sample to first detect it and second to not have it false positive. There are tomes full of explosive detection technologies like your referenced URL for both point (i.e., you can touch the subject) or remote (up to 100m, nothing really out there that does further well). The issue is, none work in “real life”. They either false positive too much (or miss too much) or are so intrusive in time, space, cost, etc. that it is implausible to use.

    3. This is why I love the hackaday comments section. I did not even know TATP existed!

      Admittedly I’m now undoubtedly on a list somewhere for reading the Wikipedia page but oh well.

      I just hope that they don’t add acetone and hydrogen peroxide to some God damn restricted chemicals list as they are too handy to lose because some fuckwit wants to blow himself up.

    4. Yeah except when all the cash has been thrown into TATP detectors the world over, the terrorists switch to a slightly less effective explosive, that investment was for nought.

  4. The problem, as always, is false positives.

    Detecting explosives is hard, not flagging the particular analytical signature from a plethora of similar compounds (or the same compound used for its intended purpose) is harder. Think of fertilizer on fields, fuel oil heating houses, peroxides in hair and acetone in nail polish.

    The real work has to do with selectivity, base rate bias and methods and devices that work beyond the laboratory.

    1. I wonder how many women carry small containers with acetone with them, especially while traveling. I mean you have to remove that polish once in a while and it makes sense to have something to do that while traveling.

      Mind you yo can also use ethyl acetate for nail polish removal, but I bet that that too can be turned in an explosive of some sort.

      But on the other hand, it’s not about being 100% non-false positives, if you can just reduce the amount of people needing to go through the anti-terrorist checks during alerts then things will get more manageable

      1. Then make it a rule that you can’t Carry acetone on a plane or into an airport. We’ve been living with similar limitations for over a decade. Wouldn’t really be too difficult to just buy some when you get there. The stuff isn’t that expensive.

        1. NO!

          We already have too much restrictions, e.g. this silly ban of liquids which also rules out water. They even have bottle scanners at the airport now, but they don’t use it, only for baby food. They still force you to throw away your water.
          We have to advance technical capabilities not bureaucracy!

      2. None carry acetone. It was banned due to its carcinogenic properties. Nail polish is made with ethyl acetate, what is also used in some glues. It is a bit less carcinogenic.

        1. I bought a liter of generic nail polish remover a few months ago specifically because it was 100% acetone and I use it in 3d printing. You can still easily find acetone sold as nail polish remover in Connecticut.

    1. I had to look it up. The ADE 651 is a fake bomb detector that was sold all over the world.

      Lincoln Laboratories is a credible research institution. Their work is cutting edge so it’s no surprise to see them working on this particular problem. As [OnceOnFire] mentioned above the test methods, and test substances are problematic so LL is a perfect example of who *should* be working on explosives detecting hardware.

      The ‘Tunnel of Truth’, that could be totally fake. I found many sites mentioning it but no real specs on what it’s all about.

      1. That “tunnel of truth” is a commercial fiction of one of the vendors trying to peddle this gear. The idea of detecting “nervous people”, whether by human or automated observation, as being potential terrorists has been widely discredited as ineffective and pseudoscience.

        The problem with all these detectors is that they don’t really solve the terrorism problem only address one symptom – and even that poorly and too late. Even if you had a detector on every train, bus, airport entrance, public building entrance, etc. it wouldn’t do much good (except for lining the pockets of the vendors of this gear). Why?

        Well, if I was a terrorist and knew that e.g. an airport is using using a scanner, I am not going to go there with my bomb to be caught. Terrorists are fanatics, not morons. They will pick another target. Heck, if I wanted be really cynical, the bad guy will just detonate it *in the queue* caused by the checkpoint/scanner at the entrance – the queuing crowd being a very convenient, concentrated target. This has happened before at checkpoints in Israel and elsewhere, exactly for this reason – concentrated mass of people makes an ideal target where a lot of casualties is inevitable. What will you do then? Buy another detector to protect the detector at the entrance?

        There is no way of having a cop and a bomb/weapon detector everywhere unless we are willing to lock ourselves in a prison, so there will always be targets like this – city centres, public transport, shopping malls, etc.

        The only effective way to minimize these types of attacks is to arrest the bad guys before they try it. And that’s where the good old police work comes in – knowing your area, good relationship and trust with the people there, so you get valuable intel, being actually useful to the community so that they work with you and not against you. And when the previous intelligence is actually obtained, it needs to be acted upon, not just filed away and lost somewhere. This is what has failed so badly in Belgium and in France.

        Unfortunately, these days everyone seems to think that technology and button pushing is the solution to every problem and cops in the streets are not needed anymore – and when there are cops in the street, it tends to be a SWAT team …

        1. “The only effective way to minimize these types of attacks is to arrest the bad guys before they try it. And that’s where the good old police work comes in – knowing your area, good relationship and trust with the people there,”

          As long as the cops hands aren’t tied with “Political Correctness, Profiling, and etc.”

      2. “Tunnel of Truth” is this an adaptation of the “Tunnel of Lights From Hell” between United Airlines concourses at Chicago O’Hare?
        It’s been a couple of decades since I’ve been through it, maybe in a fleeting sense of good taste they removed it…

  5. Travelling through an Airport with a bunch of lads after a four day long weekend drinking session for a stag a good few years ago. I remember that two were tagged with that green paste that turns pink if it detects ammonia in their luggage (ammonia being a compound common to a lot of explosives). Sweaty socks and bombs apparently have a lot in common. Avoiding false positives is the real problem.

    1. I’d be more concerned about false negatives. And as long as the false positive rate of a more automated system isn’t any worse than the current implementation, costs less, and takes less time I’d consider it a success.

  6. Another nauseating article from HaD. To stem terrorism, one must examine the (social, economic) causes of it. Rest is propaganda and pretexts and HaD is doing a great job at spreading those. Shame on you, HaD!

      1. Exactly, HaD is one of the few places where talking about the technical aspects of the matter makes sense. It’s the big news orgs that are in charge of the bullshit and panic seeding.

    1. We can do better than hacking the entire social and economic systems. Scanning the chemical soup of someone or something quickly and with few false positives (or negatives) seems too difficult. However, most landmines. IEDs, and suicide vests/belts seem to be constructed with metal casings or packed with items for metal fragmentation (nails, ball bearings, etc). At least media articles/ Wikipedia seem to allude to this idea. Since you either A) need a huge shock wave or B) need a lot of shrapnel (or both) to make a mess it seems metal might be the best way to go for an open source detector. If someone looks normal but they scan like ironman then you know something is up, at least for explosive vests and belts packed with metallic shrapnel. But this is not new tech either just a good old metal detector. You could squirt everything with magnetic dust. Like a real life version of Wooly Willy. More magnetic hair means more caution. Luggage would be a whole different game though (imagining a university band boarding a flight).

      1. Hate to burst your bubble, but a plethora of ceramics can be effectively used as bomb shrapnel and metal detectors will not be bothered by them…
        Once the explosive charge is big enough (think about a handful depending on what it is), it doesn’t even need a casing to rip big hole in a airplane fuselage, explosive decompression will take care of the rest.

        Last but not least, let’s not forget the possibility of DIYed chemical weapons, even some of the easy ones are rather scary.

        1. This is true. Airplanes are a different story though. I am not convinced that the average IED or explosive vest (deployed anywhere) is manufactured with much sophistication. And I don’t believe we’ve even seen this level of sophistication on airplanes either. These are of course assumptions based on news articles and could totally be wrong. But the bad guys may be headed there anyway. We will definitely need to scan the chemical soup (at great cost in terms of money, person power, and time) to catch the sophisticated ones. But maybe we can push the barrier to entry a little higher with something open source. You seem knowledgeable. What do you think?

          1. the issue is that any such safety is inherently an illusion unless one creates complete utter control of everything everywhere.

            there will always be a way, the only reason we don’t see anything more sophisticated today is because nothing more is needed, just look at how IED’s have evolved during 10 years of fighting and i guarantee the people looking for those IED’s in a war zone are about as motivated as human beings can get.

            now that doesn’t mean we shouldn’t try to find a solution but we should also be prepared for those solutions to be stop gap measures, they might plug a leak somewhere for some time but it wont plug all the leaks nor will it stop any leak for all time, i think it is much better to focus on the underlying cause or targeted prevention.

      2. The trouble started when people began combining primitive tribal theocratic rhetoric, modern warfare, and systemic poverty/ignorance. The pattern is clear:

        “Terrorism” was redefined to include anything that may undermine the financial, technological, or legal authority over individuals in a global society. Thus, such social problems can never truly have a technological solution, and have already fundamentally damaged the foundations of due process.

        The hypocrisy of modern media narrates anger/violence can solve ones problems, but many fail to acknowledge this assertion is illogical. However, there are many who profit from this delusion, and perpetuate the cultural bias. One must accept you can’t control what others will do, and beware of sociopaths who suggest they can:

    2. very true sir.

      In fact, I was about to address the same issue by pointing out, that the vast majority of bombs which are used to kill innocent people won’t be found by scanning random people, but by just knocking at the gates of military bases all around the world.

      Dear editors, when covering such politically biased topics, pretty please check for neutrality. You did such a great job in keeping hackaday from becoming yet another “murica or die” blog… Don’t let it become one.

    3. The problem with that approach is that airport security is highly politicized, and the current administration blames global warming for terrorism. So I don’t think that’ll work too well in our favor.

      Plus, applying this logic to a home: I’d like for the crime rate to go down, but no matter how low it is I’m still going to have locks on my doors.

      1. But we *can’t* do that! It’s *profiling*! We have to treat everyone equally, as if everyone and no-one might be a terrorist. To do it any other way just isn’t fair!

        Nevermind that El Al hasn’t had a single (successful) terrorism incident since 1973, when they adopted security measures that actually work.

  7. “Curiously, the system works by listening for the sounds of tiny detonations. The laser uses a frequency that vaporizes molecules found in explosives, and the device listens for the nearly undetectable sound of that event. ”

    The potential for false positives here sounds wild.
    I imagine most “ordinary” people would freak out if they knew how many common substances can act as an explosive if aerosolized. (Non-dairy creamer comes to mind.)

  8. The best was to detect things that go bang is to put them in an armoured box and subject them to an EMP and a shock wave. Clothing will not be harmed by this, but it will set off a bomb. People just have to separate their electronics into another smaller bag to be x-rayed. It will not stop all bombs (ones as small as a phone battery etc.) but it will stop 99% of the most dangerous devices.

  9. “Clothing will not be harmed by this”- Bull. A shock of sufficient intensity to set off even a sensitive binary explosive would shred your luggage. Primary explosives are more sensitive, but they are buried in the clothing and explosive. An EMP won’t set off all detonators, especially slapper detonators, and bridgewire detonators (exploding or not), won’t be set off unless the circuit is armed already, and won’t be set off at all (even if the circuit is armed) if a spark gap trigger is used.

  10. “Curiously, the system works by listening for the sounds of tiny detonations. The laser uses a frequency that vaporizes molecules found in explosives, and the device listens for the nearly undetectable sound of that event. ”

    This is false. There is no chemical reaction (and hence no explosion) occurring. A molecule has a discrete energy spectrum below ionization. This energy spectrum (and selection rules) determines its absorption and emission spectra where the spectra are a function of the optical wavelength of the light which is incident. The photo-acoustic effect is just the material (or trace molecules) absorbing the light (if it belongs to the absorption spectrum) and then causes heating (perhaps recoil at absorption and eventual emission(s) … or by emitting thermal infra-red). By modulating the the incident light at “acoustic frequencies” these heating/cooling cycles produces pressure waves which are detected…

    For the hacker who wish to play with an emulation of this challenge without actually using explosives can first try this on different pieces of paper painted in different colours (attached to piezo disks?) and lighting them with audio-modulated beams of light of different colours (perhaps a tunable laser scanning a range of the spectrum, perhaps different discrete light sources of differing spectrum, perhaps a strong “black body” [filament? tungsten?] filtered with rotating prism or grating to scan the spectrum).

    1. But where does it end? They could just contaminate all public transportation with small doses on seats, generating deliberate “false positives” … The constant cleanup would be a huge burden on society…

      1. That is why I suggested something else for airports, and because there are some forms of “explosive” that don’t contain nitrogen or detectable molecules. You need to screen luggage more directly and have waiting lines that do not expose large groups to a potential blast.

        1. Yes, I agree the world is not a line, it is better approximated by a surface, so doubling the radius of entry points around a facility does halve the flux of people passing that entry point… but then we have to do this for each cinema, shopping mall, train station, airport, market square, bus stations hub … ?

          1. Not if you have secure zones and open zones, layers of control. The point is people should be able to have freedom in most places, but less freedom and more security in other places. We have this in a non-systematic way now, it is just matter of applying it to some public spaces. Once medicine has found a way to detect and cure for the sorts of mental illnesses that undermine empathy perhaps we can have more freedom again, without any greater risk, but for now what can you do except control potential threats to reduce their ability to do harm?

    2. And I read about the case of a victim who survived the airport attack (but would he have been contaminated chemically?) sent a text to his spouse he was OK only to perish in the metro attack…
      After the first explosion all the fleeing people would set off false positives everywhere…).

      And what about policemen and people who legitimately use explosives, whenever they fire a gun or smth everyone needs to shower? get new clothes? ….

  11. Im starting to think chemical accounting per person & company would somewhat help (but especially help environmental pollution more than anti-terrorism), all the sewers etc… but you don’t stop a real chemist….

  12. Ok, here’s a cheap landmine detector, train chihuahuas to piss on land mines (they’re too small to set them off), and feed them something to make their urine fluoresce, then at night (when less people are around) use a .50 rifle and a UV spotlight to shoot the mines from a distance.

    1. A couple of problems with detonating land mines is 1. damage, 2. shrapnel flooding the area making it difficult for metal detectors to detect others.
      I’m not saying your method wouldn’t work in detection, but detonating the mines should be a last resort.

    2. I watched a story about rats being trained to sniff out mines. They carried little GPS backpacks on them, and sent the data to a logger so the mines could be mapped out and detonated latter.

  13. Tests don’t have to be amazingly accurate, just better than flipping a coin. Example:
    Complimentary bacon butty, Offered to all passengers at checkin.
    Has a low false negative rate (in NA & Europe; will depend on your flavour of terrorism, not so great at detecting Marxist extremists in LATAM), but a high false positive (Jews, Jains, non-extremist Muslims, non-extremist vegetarians). But these probably account for <50% of passengers in most airports (ok, not so great at Tel Aviv!), so you've halved the lines for additional scans, saving time and cash, and ensuring you don't have long queues (targets) for security. Concentrate resources on those who reject bacon.

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