Feasibility of Destructive High-Wattage Laser Arrays

First-time poster here, so excuse me if I commit an LPF faux pas or two, but I have a few questions about the (in)feasibility of using a 20 diode array of 5-6w modules to create a 100-120w device. That being said, please accept the following as a hypothetical thought-experiment about the practicality of DIY laser arrays as destructive weapons.

The rough idea is to create a circular array of ten 9mm modules in the fore row and a second row behind them staggered such that the beams emit from the aft array between the modules of the fore array. The structure of the array would be made of copper and several copper-water heat pipes (like those used to cool high-wattage computer equipment) would be integrated into the structure on both the interior and exterior of the circular array to draw heat to larger, external, air-cooled heat sinks.

The 20 beams would then be focused with a convex lens and straightened with a concave lens, like so:



Power would be supplied by high-drain nominal 3.7v LiMn 18650 batteries, wired in series-parallel to provide a maximum of 8.4v and a minimum of 6v once the batteries are drained. Of course, each laser module will have it's own driver, but with the recent advent of very high-drain LiMn batteries, as few as six 18650s in series-parallel could safely power the device, assuming each driver pulls 5-6A. However, I would likely use 10-20 18650s to give the device a longer period of usage before recharging or switching battery packs

Of course, such a device could easily cost 6,000-10,000 USD, but ignoring that hurdle, what other obstacles would keep this device from working?

I've never worked with high-wattage modules before, so I don't know how much cooling is necessary. I assume one heat pipe per module would be a good number to suck heat from the array and take it safely away to larger external heatsinks. Of course, making sure the heat pipes interface effectively with the array structure would be the hardest part, but I think it could be done, even in a DIY environment.

I've found what I think would be good lenses (link)--available in 50mm diameter--for the project that should be effective in focusing the array into a single beam, however, I worry that the lenses themselves could be damaged by the heat or potentially crack from rapid heat expansion. Is this something I should be worried about, even with lenses tuned to specific wavelengths of lasers?

The absolute most difficult issue would be aligning the individual modules to be perfectly parallel in their array. Is this possible with quality CNC machining and some delicate press work, or is getting 20 modules to line up and play nice just too difficult to be accomplished? Another related challenge would be getting the distance between the lenses exactly perfect so as to fight beam divergence at range, but i feel like it could be done with a fine enough adjustment method. Maybe.

Knowing a little about how light works, I'm guessing the longer the wavelength the better as far as giving the device good destructive range. What commercially available diodes in the infrared spectrum could supply this kind of wattage? Is it feasible that a DIY-er could buy them for around $200 per diode (or preferably much less)? What kind of effective destructive range could I expect with infrared? Though my research has dredged up nothing, are there any diodes in the microwave spectrum that can be purchased?

To do any amount of damage I'm assuming I would need to use continuous wave diodes, but am I wrong? Could pulsed lasers do the trick? It seems I could get a lot more wattage for my dollar with pulsed lasers like these(link), but it seems like a pulsewidth of 100ns and a duty cycle of 0.1% would result in way less effective heat downrange, not to mention the difficulty of supplying the amperage 20 of them would require. But am I wrong? Could I deliver more heat with those?

Of course, building/using a device like this would be wildly dangerous, but that's kind of the general idea. Aside from igniting clothing or surrounding environment, inflicting tiny but painful superficial burns and causing permanent blindness, would 100 watts of infrared penetrate enough to cause incapacitating damage? Could a device like this only be used on stationary targets, or would it deliver enough energy to ignite something virtually instantaneously?

The last, and weirdest obstacle that could happen would be the weakening of the beam via destructive interference (link). Is that likely/possible when concentrating multiple beams into a (hopefully) singular beam?

I apologize if talking about lasers as weapons is something generally considered taboo by LPF, but for me, it's the most interesting aspect of lasers and the trend towards ever-higher wattage diodes. I would understand if moderators decide to delete the post, but I hope we can generate an interesting conversation regarding the possibility of DIY laser weapons. Thanks for reading my novel, and please feel free to poke/burn as many holes in this crazy idea as you want!

I'm sure the military are feverishly working away on developing top-secret hand-held laser weapons/devices like the one you're proposing. Iv'e heard that there are one or two people on here who are working on similar concepts, albeit on a smaller scale.

To me, harnessing the power of light to produce a weapon is just a natural progression of the science. It's going to come sooner or later (in fact it's already here with T.H.E.L and L.A.W.S) and when it does come I suppose it will consign guns and ballistics to the history books in a similar way that the clubs and spears of our ancestors eventually disappeared.

As to the feasibility of your proposal I'll leave that to the more technically enlightened members of the group of which there are many. Hope it works out!

playludesc, this is inappropriate for a first post. I am not being rude, I am just telling you because someone else was just recently banned in their first days because of this very same thing. No doubt some will suspect you are him so I am sure the moderators will check your IP address. Please fill out your profile with more info, especially your location and your age. No one is going to talk to you about this if you are too young, in fact some businesses and people won't sell to someone without proof of age. So you may want to post a photo of yourself too like many of us do, not required though, there are two places for that. Your first post should be in the welcome area where you can tell us a little about yourself so people can get to know you better. This is a very international forum with members around the world. How do we know your not with Hezbollah, FSA, ISIS, Hamas, etc. There is a flaw in your idea and a better way but am not going to answer just yet, maybe someone will but I doubt it.

Alan

As PI R said post in the welcome thread first and fore most. The thing is with large projects like this is that they tend to be A) expensive. B) time consuming, and C) and a cluster. This is a military application if I have ever heard of. As former military this device as I am going to call it has the potential to be used and abused. So really no responsible member is going to really tell you how to do it. There have been other members in the past that have done some thing with in this realm of sci fi but for now fill out your membership card

All jokes aside, I'm sorry for jumping the gun with my post. I spend most of my time on forums where talking about improvised weapons is expected and encouraged and I might have blended cultures a bit too much here.

Additionally, I've never worked with lasers before (outside of playing with my cats) and I really just assumed that my idea would end up being discarded as hair-brained and totally impractical, something like a fun armchair-engineer's debate where we go back and forth about advantages of DEWs vs traditional kinetic weapons and try to spitball something that could theoretically work.

Lastly, I had a feeling that this might be ill-received, so I actually did spend some time trying to figure out the best way to "join the party". I even read the rules in the terms of service and more than one guide on how to be accepted by LPF. (Still a little boggled why a forum would need more than one of those and how a user could read both and still violate the unspoken rules, lol). I guess my biggest mistake was that I didn't evaluate my audience well enough and assumed that there were enough other people who thought lasers were cool because they burn things to make a post like mine seem a little overeager but generally acceptable.

To assuage any fears, I'm (clearly) an American who strongly supports the second amendment (sorry about that), I'm an owner of an advanced vaping shop (hence my affinity for 18650s), I enjoy tinkering with dangerous things like fast (and slow) cars, and I enjoy tackling difficult DIY projects. Lasers have fascinated me for years, but I've never really had the budget to get into them. Now that budget is starting to look like a possibility. I'll likely never build something as crazy as the abovementioned, but I would love to talk about it.

You need to please put the state at least of were you reside. Just stating USA does not invoke a sense of confidence in the older members of LPF. As some one that also likes to use firearms, blades, midevil weapons, and other things that get your blood going. I will state that Lasers are no laughing matter. It is not that we frown on crack pot Ideas. Heck I have had some my self. But your taking a direct energy weapon of sorts. this in not a joke, this is not some thing that we take lightly. Laser Hobbyist like my self are tired! We are tired of getting blamed for every crack head, idiot, moron that thinks that shining lasers at people, aircraft, cars, and every thing else. Every day we hear about some one doing some thing with a laser on the news and we get hit with more sanctions because of them.

Just in the last five months I have heard of at least ten on the west coast with people using lasers with out having a Idea what they are doing.

We are not singling you out for having a idea. We are just concerned that you to will be another one of these people. We have had to many persons as of late coming up with these kind of ideas and most of them are either spammers, trolls, idiots, or young people thinking laser are cool and you can do any thing you want with them. It is going to come down to it sooner than later that it will be illegal to own lasers unless your a scientist working in a lab, military, or police. Then say bye bye to the hobby. So please fix your avatar, do a welcome thread, and think carefully about what it is you want out of this hobby and how it is going to be perceived by other members

Nice avatar. If you own a vaping shop the 510 threaded laser modules may be something of interest to you, see this thread: http://laserpointerforums.com/f52/dtr-le-adapter-v1-92612.html
You can buy them here: https://sites.google.com/site/dtrlpf/
He also sells some of his stuff on Amazon: http://www.amazon.com/gp/aag/main?i...=ATVPDKIKX0DER&orderID=&seller=A1NFWW2PTPQL0U
And I think on eBay too.

Also please check out our two gun threads:
http://laserpointerforums.com/f57/gun-discussion-79239.html
http://laserpointerforums.com/f57/post-your-gun-pics-52331.html
I recommend not discussing guns outside of those two threads, this is a global forum and there are many different opinions.

Alan

Alrighty, I made an intro post in the welcome forum, I hope it gives you guys a good idea of who I am and why I want to get into the laser hobby!

http://laserpointerforums.com/f37/new-member-interested-long-range-burning-93793.html

[Ignoring everything but the technical side for a moment...]

The problem isn't so much can it be done, but rather, why do it when there are solutions that work far better which are far less expensive, more reliable, and safer.

Consider a SLA powered water cooled backpack driven 100W/150W/etc CO2 Laser. The money you save from the diode design could/should be put into better collimating and beam expanding (divergence reducing) optics for the 10.6um emission, which would enhance the device's range greatly. Several of us have already done these systems for 10/15/40W units.

When it comes to diode lasers it is best to assume 20% efficiency when designing heatsinking for continuous use, i.e. if you want 200W out you need to remove 800W of heat. This alone makes the design you proposed unrealistic.

Sigurthr said:

[Ignoring everything but the technical side for a moment...]

The problem isn't so much can it be done, but rather, why do it when there are solutions that work far better which are far less expensive, more reliable, and safer.

Consider a SLA powered water cooled backpack driven 100W/150W/etc CO2 Laser. The money you save from the diode design could/should be put into better collimating and beam expanding (divergence reducing) optics for the 10.6um emission, which would enhance the device's range greatly. Several of us have already done these systems for 10/15/40W units.

When it comes to diode lasers it is best to assume 20% efficiency when designing heatsinking for continuous use, i.e. if you want 200W out you need to remove 800W of heat. This alone makes the design you proposed unrealistic.

Click to expand...

Exactly , Sigurthr

playludesc --It is a daydream about destroying things with lasers based upon burning things and popping balloons--without any practical knowledge about what lasers can and can't do and why.
There is a whole field of light-matter intereactions knowledge that comes into play. Is a lot more complicated than you imagine.
A laser beam has no temperature - there is no inherent "temperature" to a laser beam. Heat is the random motion of matterparticles (atomic or molecular particles). A laser beam itself is not made of matter but of ‘photons, which have no mass, thus a laser beam can have no temperature."Heat" is caused by a laser beam energy being absorbed by a material surface and turning from light energy to heat energy. Effectiveness at heating up a material with a laser depends on the energy output of the laser , the energy density of the laser beam, the wavelength of the laser, and said materials ability to absorb the energy of same.
If you are thinking to use photon transmitted energy/laser output to heat something, you need to know what wavelengths your target can pass, absorb and reflect and how efficiently and under what conditions.
Is not like a Star Trek Phaser or plasma beam at all.

Here is a recent thread about world's most powerful handheld laser 15.4W. Was built by LPF member ricktrent4 : http://laserpointerforums.com/f65/worlds-most-powerful-handheld-visible-lase-86729.html

You can simply buy 100W or greater lasers that exist---no need to reinvent the wheel see: http://www.synrad.com/fseries/f100.htm

Is not like your the only one who thinks about such things--see this site to get a better understanding: How to Build a Laser Death Ray

Lockheed Martin successfully tested its 30-kilowatt fiber laser weapon system which burned through the engine manifold in a matter of seconds from more than a mile. Through a technique called spectral beam combining, multiple fiber laser modules form a single, powerful, high-quality beam that provides greater efficiency and lethality than multiple individual 10-kilowatt lasers used in other systems. Highest Power Ever Documented by a Laser Weapon of its Type---- see: http://www.lockheedmartin.com/us/news/press-releases/2015/march/ssc-space-athena-laser.html

Sigurthr said:

if you want 200W out you need to remove 800W of heat. This alone makes the design you proposed unrealistic.

Click to expand...

What about cryogenics? Compressor/Stirling combo cryocoolers are tiny and can be found on eBay for usually ~$600. I've even seen some go for $200. Perhaps a "coldsink" could be used to "store" the low temperatures, and then cool the laser after it fires.

Sigurthr said:

The problem isn't so much can it be done, but rather, why do it when there are solutions that work far better which are far less expensive, more reliable, and safer.

When it comes to diode lasers it is best to assume 20% efficiency when designing heatsinking for continuous use, i.e. if you want 200W out you need to remove 800W of heat. This alone makes the design you proposed unrealistic.

Click to expand...

Thanks for your response Sigurthr! This is exactly the kind of feedback/discussion I was hoping for. Like I said, even I don't think this is a particularly great idea, but I really want to bounce it around and see how practical a device like this might be.

I feel like cheaper might be debatable. The 100w Firestar CO2 laser that Encap linked costs about $13000 new and others in that power range seem to cost at least $7-8000 new. All of that is not to mention the batteries I'd have to purchase to safely get up to 96 volts and 18 amps. I agree with you that there are definitely easier projects, but sometimes a DIY project isn't about ease. As far as working much better, you're probably very right. Getting 20 beams to play nice together sounds like a nightmare, but other similar arrays have been made and do exist, like the array for which styropro is getting a GB together.

As far as the heat issue, the heat pipes I'm looking at are rated to transfer 40w each with an extremely low coefficient of thermal resistance. With a diameter of 4mm that can be crushed or bent to shape as needed without really affecting performance, I feel like I could cram at least 20 of them in the hollow center of the array and around the outside of it. That gets me 800w of cooling as long as I attach the other end of the heat pipe to a big enough heatsink. In a rifle-sized device and a few fans, I should have plenty of room to mount heatsinks to dissipate the estimated 400-500 watts necessary to keep the lasers in their comfort zone. Heck, plenty of graphics cards can generate upwards of 150 watts of heat, so some very rough math tells me that I need about 4 times the area of heatsinks used on high-end graphics cards. 160 square inches of low-profile, good quality heatsinks should do the trick. Again, on a rifle-sized device that's inconvenient, but not an insurmountable problem.

The trickiest part of cooling is effectively interfacing the heat pipes with the structure of the array. My easiest solution is clamping or wedging the heat pipes against the array and plenty of Arctic Silver. Crazier solutions involve placing the heat pipes in the hollow center of the array and pouring molten lead into the remaining crevices between the heat pipes and the array (before the lasers are mounted of course). Lead isn't the best of heat conductors, but the increased area of contact it offers might make up for it.

tl;dr: Heat may not be as difficult an issue as you might think, but still a very important consideration.



To respond to Encap, I understand pretty much all of those things regarding lasers. It will be a long time before a hand-held laser can achieve the anti-material capabilities of virtually any rifle, but I think we're at a time in the evolution of the technology that enables us to make something that lands somewhere between the capabilities of a good slingshot and .22lr rifles--and that would be pretty freaking cool.

I saw Rick's posts and videos before I posted my own idea, which definitely encouraged me; but with a big enough budget (and good enough optics), this just proves the point: even as a DIY enthusiast, we can make a hand-held laser that's a viable (albeit wildly un-economical) weapon.



So, what's next? I feel like the biggest obstacles are properly aligning the beams and focusing them into a single, effectively small beam. I assume the biggest sub-issue of that larger issue is getting the beams parallel as they exit the array, which will likely involve a lot of pressing, focusing, measuring, and redoing.

Secondly will be the challenge of getting those 20 beams to come together. Are the lenses I posted in the original post a decent solution to that? Is there something off-the-shelf that would work better? Do I need to worry about cracking the lenses with the intense heat they will (hopefully not) absorb?


To respond to Pi R, I was really excited when I saw that DTR was putting together ready to use modules with a 510 connector. I'm definitely going to get one and it's definitely going on one of these with two 18350s inside.

playludesc said:

To respond to Encap, I understand pretty much all of those things regarding lasers. It will be a long time before a hand-held laser can achieve the anti-material capabilities of virtually any rifle, but I think we're at a time in the evolution of the technology that enables us to make something that lands somewhere between the capabilities of a good slingshot and .22lr rifles--and that would be pretty freaking cool.

This just proves the point: even as a DIY enthusiast, we can make a hand-held laser that's a viable (albeit wildly un-economical) weapon.

Click to expand...

Depends on what you call a weapon--what makes you imagine it would be a weapon any more than an expensive boat anchor?
I think the imagined device is way better in imagination than it would be in real world for many reasons.

Take the case of burning wood--there are many other variables as well, such as dust, ect in the air, color of the object, and humidity but assuming they don't count--- to cause ignition of live wood (wet) @ 10+ ft, would require CO2 lasers @ 1kw for more than 3seconds. scorching would occur but actual ignition of damp wood is far harder. Kiln dried wood (plywood) @ 35' with a 5kw CO2 took less than 1 sec to burst into flame, but @ 100' took longer than 5sec. this was with an unfocused beam straight out of the resonator @ aprox 2.5" dia. Not much of a weapon as weapons go.

Encap said:

this was with an unfocused beam straight out of the resonator @ aprox 2.5" dia. Not much of a weapon as weapons go.

Click to expand...

So... You're saying that beam collimation is important if we want this to work? I mean, you're right, that's a lot of watts for very little results, but I think we can do better with our device. The approximate energy density of the laser you mentioned is something like 150 W/cm^2. If we could get our laser well focused at even 5mm, we're talking 3-4 times that energy density. Not to mention we might be able to use a more effective wavelength for common targets than IR vs wet wood. And we did it all for a fraction of the price of a 5kW CO2 laser (lol).

Edit: thinking about it, I'm realizing 5mm is perhaps too optimistic at a decent range, but who knows, it's not an impossibility with enough work.

Perhaps you could somehow make a tiny COIL laser? An interchangeable "clip" could contain all the necessary chemicals.

playludesc said:

So... You're saying that beam collimation is important if we want this to work? I mean, you're right, that's a lot of watts for very little results, but I think we can do better with our device. The approximate energy density of the laser you mentioned is something like 150 W/cm^2. If we could get our laser well focused at even 5mm, we're talking 3-4 times that energy density. Not to mention we might be able to use a more effective wavelength for common targets than IR vs wet wood. And we did it all for a fraction of the price of a 5kW CO2 laser (lol).

Edit: thinking about it, I'm realizing 5mm is perhaps too optimistic at a decent range, but who knows, it's not an impossibility with enough work.

Click to expand...

Everything is possible in imagination---not so in the real world. Many real world reasons are not imagined in your idealized imanginary "weapon" design considerations but good luck reinventing the wheel.


"Diode-laser arrays have long generated high powers by combining the outputs of many laser stripes. That works well for applications, like diode pumping, that do not require high beam quality. However, combining outputs in that way cannot increase the radiance beyond that of a single laser stripe. “The ‘holy grail’ of beam combining is to take a bunch of lasers and get a single Gaussian beam out,” says T. Y. Fan of the MIT Lincoln Laboratory (Lexington, MA) A large military research program 15 to 20 years ago tried to combine diode-laser beams, but met with little success"

From: Encyclopedia of Laser Physics and Technology - coherent beam combining, tiled-aperture, filled-aperture, mutual coherence, amplifiers, arrays
"Overall, methods for coherent beam combining have not been very successfully applied, although many different approaches have been investigated. The main difficulty is to obtain phase coherence at high power levels in a sufficiently stable manner, working not only in a quiet laboratory environment but also in a mechanically more noisy industrial setting. Another challenge is the need to match precisely and stably wavefronts and polarization directions. "

A picture being worth 1000 words maybe some of these will give you a more realistic idea: https://www.google.com/search?q=combining+20+laser+beams+into+one+beam&rlz=1T4FUJN_enUS494US494&tbm=isch&tbo=u&source=univ&sa=X&ei=LS1cVYXKFdPksATY7YLIBQ&ved=0CC8QsAQ&biw=1342&bih=531

PS maybe google laser beam combining to get some idea of that field then google air-matter interactions and study up that field--might help understanding better.