Stop, Drop the Beat, and Roll
March 24, 2015 7:13 AM   Subscribe

For their senior project, George Mason University students Seth Robertson and Viet Tran decided to ignore all of their professors and classmates who told them their idea was terrible. They proceeded to invent a fire extinguisher that uses sound waves instead of chemicals to put out fires. The project was partially inspired by the fact that traditional fire extinguishers do not work in space.
The Robertson/Tran sound wave device is free of toxic chemicals and eliminates collateral damage from sprinkler systems. Mounted on drones it could improve safety for firefighters confronting large forest fires or urban blazes. "Fire is a huge issue in space," said Tran. "In space, extinguisher contents spread all over. But you can direct sound waves without gravity," explained Robertson.
If you want to learn more about the planning and construction process, you can still read through their Senior Project Prezi presentation.

Given the use of fluorocarbons in traditional fire extinguishers and the history of other dangerous chemicals used in their manufacture (halons were only removed from the spray mixture in 1994), there are many potential uses for this technology. One profession already interested in the bass frequency generator is Emergency Services, since they have reason to be concerned about how dangerous it is for firefighters and other first responders to potentially inhale the chemicals currently used in extinguishers, which have been linked to cardiac arrest and acute respiratory distress.

And which bass works best? “Initially, both students thought big speakers and high frequencies would douse a fire. "But it's low-frequency sounds – like the thump-thump bass in hip-hop that works," said Tran, who joked that rappers like 50 Cent could probably douse a fire, and that hip-hop celebrity endorsements might be just the ticket to hawk their fire extinguisher.”
posted by a fiendish thingy (48 comments total) 29 users marked this as a favorite
 
But! There's no sound in space!
posted by MartinWisse at 7:21 AM on March 24, 2015 [6 favorites]


Great idea, but unfortunately, sound waves don't work in space either.
posted by I-Write-Essays at 7:23 AM on March 24, 2015


There's also no conventional fire in a vacuum, what with the need for oxygen. The use case here is a space station or other pressurized zero-gravity environment.
posted by Holy Zarquon's Singing Fish at 7:24 AM on March 24, 2015 [40 favorites]


Or fire.

So I assume they're talking about spacecraft. With pressurized atmospheres maybe?

Damn it, Holy Zarquon's Singing Fish!
posted by Naberius at 7:25 AM on March 24, 2015 [2 favorites]


Oxidation (i.e. fire) doesn't work in space either.
posted by LionIndex at 7:25 AM on March 24, 2015


There is no oxygen in space either, brainiacs - he's talking about inside the spacecraft.
posted by Pogo_Fuzzybutt at 7:25 AM on March 24, 2015 [31 favorites]


Fastest pedant in the West!
posted by Holy Zarquon's Singing Fish at 7:27 AM on March 24, 2015 [57 favorites]


BASS! How low can you GO? Kitchen fire? Wha-what a brother know!
posted by flapjax at midnite at 7:27 AM on March 24, 2015 [27 favorites]


Yep, if you read the links, you can see that they are talking about fires inside spacecraft, where the particulates from traditional extinguishers would damage the equipment (and the human lungs) onboard.
posted by a fiendish thingy at 7:27 AM on March 24, 2015 [1 favorite]


I wonder whether this would be more useful in a fixed installation as a fire or flare-up preventer. Why have sprayers over a griddle which will then shut you down for the cleanup period - and thus discourage people from deploying the solution - if you could have a first wave method like this?
posted by phearlez at 7:28 AM on March 24, 2015 [3 favorites]


While this is amazing, practical, and incredibly useful, even here on Earth (since you don't have to worry about the extinguisher being "full") - I can't help but wonder at all the wonderful bowel-disrupting possibilities of this device.
posted by enamon at 7:31 AM on March 24, 2015 [3 favorites]


The real problem - and they talk about this in the article - is that while soundwaves will disrupt oxidation they do nothing to cool the burning material, so as soon as you stop the sound the fire comes back, and whatever was burning will still be dangerously hot even if you keep the extinguisher on. So there's still a need for water or chemical extinguishers or something else that will either cool the area or neutralize the fuel.
posted by Holy Zarquon's Singing Fish at 7:31 AM on March 24, 2015 [6 favorites]


enamon: needing electricity counts as a kind of "need to be full". And the brown note is a myth.
posted by idiopath at 7:33 AM on March 24, 2015


The real problem - and they talk about this in the article - is that while soundwaves will disrupt oxidation they do nothing to cool the burning material

No problem, the extinguisher will just use Vanilla Ice.
posted by Steely-eyed Missile Man at 7:34 AM on March 24, 2015 [9 favorites]


The roof, the roof, the roof is on fire... no, wait, we're good.
posted by dywypi at 7:36 AM on March 24, 2015 [8 favorites]


"The house burned down because all Dave had on his phone was Bette Midler."
posted by jimmythefish at 7:45 AM on March 24, 2015 [11 favorites]


Oh, I see.... so it really is all about that bass.
posted by mondo dentro at 7:48 AM on March 24, 2015 [1 favorite]


Did anyone mention that there's no fire in space 'cause of the vacuum? Oh, they did? Oh.
Cool article, didn't know you could do that. In fact, I hadn't the faintest idea at all. I mean, I'm just boggled.
posted by From Bklyn at 7:50 AM on March 24, 2015




Note that most regular fire extinguishers you see have a powder inside them that may settle, so you are advised to knock them on the ground or tap the sides before use to loosen it up, or else you may find that you run out really quickly.

I wish the demonstration video had been longer, and they'd shown it used on different materials.
posted by Catblack at 7:56 AM on March 24, 2015


This looks like a fascinating and impressive student project. However, at this point, from a practical standpoint the article seems to have hyped it a bit too much.

From the end of the Post article:

In 2012, the Defense Advanced Research Projects Agency conducted a project on “acoustic suppression of flame” and found that it worked on small levels but could not determine if it would work at “the levels required for defense applications,” the agency said.

Kenneth E. Isman, a clinical professor in the University of Maryland’s fire-protection engineering department, said that the question of scale is important. “It’s one thing to put out a tiny fire in a pan,” Isman said. “But how much power would you need to deal with a couch or bed on fire, which is a common scenario in deadly fires?”


And they don't seem to have done anything significantly different than the DARPA researchers did:

IFS performers succeeded in demonstrating the ability to suppress, extinguish and manipulate small flames locally using electric and acoustic suppression techniques. However, it was not clear from the research how to effectively scale these approaches to the levels required for defense applications.
posted by Mr.Know-it-some at 7:59 AM on March 24, 2015 [1 favorite]


I like these two kids. They weren't afraid to fail. In fact they expected to. And most of their potential advisers on the project get a fail for refusing to let these two try something that may or may not have worked. Kuddos to Prof. Brian Mark. Success is built on the ashes (*ahem*) of failure.
posted by 724A at 8:01 AM on March 24, 2015 [7 favorites]


Holy Zarquon's Singing Fish: "The real problem - and they talk about this in the article - is that while soundwaves will disrupt oxidation they do nothing to cool the burning material, so as soon as you stop the sound the fire comes back, and whatever was burning will still be dangerously hot even if you keep the extinguisher on."

Regular old convection and radiation will eventually cool the combustibles if you suppress the fire long enough. Mounting these inside a commercial hood as an initial extinguisher method would be an ideal application (with a much larger potential market than spacecraft). You could just leave the power on, for hours if necessary, until the stove cooled off. Removing the source of ignition is going to suppress many grease/oil fires all on its own.
posted by Mitheral at 8:12 AM on March 24, 2015 [1 favorite]


I think this would be useful for electrical fires. You already have a power source, and for the sort of hardware we're talking about, you can make space for a subwoofer in the same box as the electronics live. This would put out the fire and leave most of the electronics intact.

To cool it -- well, there's going to be a cooling system in any supercomputer to begin with? This is for when that's not working fast enough.
posted by LogicalDash at 8:13 AM on March 24, 2015


And, well, you could use this thing in conjunction with an ordinary fan, in order to prevent the flames from licking anything they shouldn't.
posted by LogicalDash at 8:15 AM on March 24, 2015


Fire in a spacecraft is a serious, no bullshit, bad deal.

1) You can't run. You open the door and, well, the fires out, and so are you.

2) With the exception of the ISS, there's nowhere to run. One room, no waiting.

3) As the fire burns the oxygen you need to breath, you start dying even faster.

4) Zero G makes firefighting harder -- because things don't lie down. You hit something with a stream of anything, it moves.

5) Oh, speaking of that. Do you know what we call a fire extinguisher in zero g? That's right, it's a bottle of ΔV!

There are some controlling factors, though. Microgravity means no convection, which means no chimney effect drawing in air, only contact. Fires spread out in a sphere. If you can get on top of it quickly, and your buddy can hold you in place while you hit the fire, you can usually knock it down quickly. And, of course, if you're in a station with multiple modules, the fastest way to make the fire go away is to get everyone out of the modules, close the hatches, and dump pressure.

Unless you're on Mir, and the thing that's on fire is on the oxygen generator, which is getting *plenty* of oxygen from...somewhere. That fire was nasty. Thankfully, Mir and the ISS have normal 14.7psi 70% nitrogen atmospheres, not the 5% pure oxygen atmosphere of the Apollo spacecraft.
posted by eriko at 8:16 AM on March 24, 2015 [8 favorites]


And most of their potential advisers on the project get a fail for refusing to let these two try something that may or may not have worked.

It's not entirely clear that they were rejected as much as they were told they would be held responsible for failing to accomplish something. Since the article doesn't explicitly say and calls it a senior project, I presume they're undergrads. Expecting them to do something practical and attainable and demonstrate competency is the point at this level, not new research. I think it's quite reasonable for advisors to try to steer them to something that will produce results, even if it's maybe not as new and sexy as they wanted.

Apparently Prof Mark was willing to work with them to let them show process and effort and mastery even if the end result was non-functional, but that's an above and beyond thing. He deserves kudos but the others expecting the students to work within the constraints of an undergrad-appropriate structure isn't a "fail."
posted by phearlez at 8:16 AM on March 24, 2015 [1 favorite]


I didn't see anything explaining what happens when a prankster holds this up to someone's ear and pulls the trigger. Was that mentioned anywhere?
posted by YAMWAK at 8:17 AM on March 24, 2015


Ar, but ye carn't use that as an emergency EVA thruster in space, can ye? The old ways are the best, I always say.

Never mind that the delta-V imparted by the entire contents of a 10kg extinguisher to 100kg of Sandra Bullock + space suit is probably like around 5kph
posted by George_Spiggott at 8:21 AM on March 24, 2015 [1 favorite]


WALL-E doesn't mass much, I guess.
posted by Artw at 8:27 AM on March 24, 2015


"The real problem - and they talk about this in the article - is that while soundwaves will disrupt oxidation they do nothing to cool the burning material, so as soon as you stop the sound the fire comes back, and whatever was burning will still be dangerously hot even if you keep the extinguisher on."

I can still see some applications where this would still be really useful. If nothing else it would be a good way to buy yourself some time to think so you can figure out a way more permanently put out the fire.

It might be that to put out a large fire of the type that they're worried about in space you need such powerful vibrations that it will rattle your spacecraft apart but there are smaller applications where this would be really handy.

And I would think that there are weird ways to generate sound waves other than just get a big speaker and put a signal to it. There must be some way to generate waves so that they combine in some way at a certain point or something right? Sort of like how noise cancelling headphones work but reversed.

I imagine the advanced version of this being a couple of tiny, computer controlled speakers with the sound they make being inaudible unless it happens to be your ear that's on fire or something.
posted by VTX at 8:30 AM on March 24, 2015


I didn't see anything explaining what happens when a prankster holds this up to someone's ear and pulls the trigger. Was that mentioned anywhere?

Same thing as when pranksters go around spraying people in the eyes with foam or CO2 fire extinguishers?
posted by EndsOfInvention at 8:30 AM on March 24, 2015 [2 favorites]


Can you use it as your sound system when it's not putting out fires?
posted by Four Flavors at 8:37 AM on March 24, 2015


Apparently Prof Mark was willing to work with them to let them show process and effort and mastery even if the end result was non-functional, but that's an above and beyond thing. He deserves kudos but the others expecting the students to work within the constraints of an undergrad-appropriate structure isn't a "fail."

Well, we disagree on what is an undergrad-appropriate structure. I may be over extrapolating, but putting the AYSO everyone gets a trophy mentality to focusing more on process and effort and positive results rather than just process and effort regardless of results seems like a mistake in the long run. We all need to learn to fail and to try even if we expect we might fail. Why take the end result out of the equation and learning process? We can still learn about process and effort even if the end result is not success.

Maybe you've hit on something. The profs that turned them down are just playing within the system. The system needs rethinking.
posted by 724A at 8:37 AM on March 24, 2015


That would explain why there are no fires at Burning Man.
posted by ZenMasterThis at 8:42 AM on March 24, 2015 [3 favorites]


Undergraduate degree programs are basically intellectual obstacle courses. Your ability to jump through any one particular hoop doesn't say very much; it's really your performance in aggregate, over the entire program, that says something. Your job in the "real world" probably won't have a direct connection to the curriculum anyway, but it does matter that you spent a few years working the necessary brain muscles while marinating in the nomenclature of your chosen field.

This is an observation, not a normative statement of how I think it should work.
posted by anifinder at 8:57 AM on March 24, 2015 [1 favorite]


This could be really useful to buy time for evacuation, if you placed the speakers along exit routes to keep them clear of fire. Or, in sealed or inaccessible equipment! High voltage equipment, engine compartments, stuff like that.

I wonder if you could make a wearable version as a sort of protective field for firefighters.
posted by jason_steakums at 9:04 AM on March 24, 2015


I'd like to see this technique demonstrated on a more energetic fire. Like an actual stove-top grease fire. The fire in the pan was good, but nothing like a pot of deep-fry oil blazing away on the stove.
posted by Thorzdad at 9:39 AM on March 24, 2015


I didn't read the article but I assume that in the case where the fire was not started by us, it plays that Billy Joel song, or if it is a house fire then it plays that Talking Heads song
posted by Ratio at 9:51 AM on March 24, 2015 [3 favorites]


Well, we disagree on what is an undergrad-appropriate structure. I may be over extrapolating, but putting the AYSO everyone gets a trophy mentality to focusing more on process and effort and positive results rather than just process and effort regardless of results seems like a mistake in the long run. We all need to learn to fail and to try even if we expect we might fail. Why take the end result out of the equation and learning process? We can still learn about process and effort even if the end result is not success.

Unpopular a belief as it may be, but process and effort and positive results are what most people's professional careers are going to amount up to. An undergraduate degree represents 120 credits worth of work, about sixty of which are basics and/or general knowledge materials. The majority of that engineering student's other major classes are going to be narrow focus subject material - say, for example, signals - which will have projects that don't amount of to a lot of useful results, just proof of concepts. The final project represents a chance for the student to put all that together and create something using those skills and displaying organization and management.

If you want to draw a parallel to AYSO it's not everyone gets a trophy it's the project as the first chance after all the drills and training and practices to go actually play a game. It's not that it's impossible for some properly motivated students to create a project that reaches farther, but the reality is there's still miles more potential room for advancement and study at the point of a BA/BS. The illustrated guide to the PhD expresses this nicely.

You want to reward ambition and exploration, and that's a fine and noble thing. But new learners often want to go out and fly before they can walk, and pushing them to attain competency first is very often the most important way we ready them to eventually truly excel.

If these students had gone after this lofty concept and been thwarted they could have ended their education without ever actually doing something fully under the umbrella of the institution. Personally I don't think that's always a bad thing, but the same people who are often always wanting to shoot for the moon rather than some grinding foundation-laying are often the same ones in the engineering/software disciplines who whine about how students don't learn practical things while going after their degrees.

They eventually convinced someone they could, in fact, do the work in a sufficiently rigorous way such that they could explore and prove mastery. Clearly the opportunities are there for the motivated and determined. But treating people initially like they are part of the average group who just needs to get in the practice isn't unreasonable.
posted by phearlez at 10:09 AM on March 24, 2015 [1 favorite]


So they want to stop a fire with sound? I'd like to put these guys in a room with some speakers that make sound with fire, and see if they cancel each other out.
posted by sol at 10:14 AM on March 24, 2015


Would be nice if this could be retrofitted to existing sound cannons used for crowd control.
posted by ZeusHumms at 10:15 AM on March 24, 2015


Sure, until someone accidentally flips the polarity and it turns the crowd into a riot that's on fire.
posted by VTX at 10:18 AM on March 24, 2015 [4 favorites]


"The real problem - and they talk about this in the article - is that while soundwaves will disrupt oxidation they do nothing to cool the burning material, so as soon as you stop the sound the fire comes back, and whatever was burning will still be dangerously hot even if you keep the extinguisher on."

Well for stovetop grease fires where it's possible to do so, the prescribed solution is to put the lid on the pan that is burning, which similarly deprives it of oxygen without cooling it. As stated above you can rely on hot things cooling down normally, as long as you can keep them from burning.

I think this would be useful for electrical fires. You already have a power source,

I disagree. When there's an electrical fire, the first thing you want to do is cut the power, so whatever started the fire stops adding more heat to the system. Depriving an overheating short-circuit of oxygen won't stop it from overheating, it will just extinguish the other stuff that got lit on fire by it. So you want the fire extinguisher to be run on its own power, so when you do cut the power to the whole room/building it still works.
posted by aubilenon at 10:45 AM on March 24, 2015 [1 favorite]


Hmm, very interesting. It seems to me though that, if you're using the wave to displace oxygen, your wavelength would need to be longer than your fire, which is probably why they are getting results at 30 and 60 Hz. But if you have a very big fire, that is going to be very difficult indeed. The other worry would be that sound reduces in intensity very rapidly, so I'm not sure this would work at ranges much farther than, well, right up close. So yeah, while I see the coolness with a small fire up close, I'm not sure about its broader implications. I'll be interested to see what happens with it though.
posted by Lutoslawski at 10:46 AM on March 24, 2015


Never mind that the delta-V imparted by the entire contents of a 10kg extinguisher to 100kg of Sandra Bullock + space suit is probably like around 5kph
Predictably, when I looked up "delta v of a fire extinguisher" on Google, I got an solution in a KSP forum. It's actually more like 25kph (7m/s) for a typical C02 fire extinguisher. Apparently some exotic types of extinguishers could get you up to 100m/s, though! That could be enough to get you out of low earth orbit (and barely into the atmosphere) in some cases (not that that would likely make your day any better, just much shorter).
posted by WaylandSmith at 12:41 PM on March 24, 2015


Apparently some exotic types of extinguishers could get you up to 100m/s, though!

The biggest question is "what is the exhaust velocity?" The equation is simple enough, but I just have no idea how fast the CO2 is coming out of the extinguisher, and it would be coming out substantially slower here on Earth (thanks to the 1atm back pressure) than it would in space, so I really don't even have enough experience to hazard anything but a really wild guess. But hey, this is Sparta Metafilter. Let's make a really wild guess.

If it's 50m/s, and we assume the extinguisher loaded weight is 30kg, then M0 is 130kg, M1is 120kg, the mass fraction end up 1.083, the log of that is .08, and we multiply that by the exhaust velocity, so 4m/sec, or just short of 9mph, or 14.4kph.

For 7m/s, you need a bit higher exhaust velocity, but that's not improbable, so yeah, I'll buy that as a reasonable answer.

Basically, in rocketry, ΔV comes from two things -- how much mass you throw out the nozzle, and how fast you throw it. You can, in fact, trade these off. A xenon ion thruster throws very little mass out the back, but throws it out very fast indeed. An RP-1/LOX engine throws lots and lots of mass out the back, but at a much lower velocity. In terms of ΔV, you can end up with the exact same amount from both engines.

(However, there's more that one way to categorize an engine, and you'd better have that big RP1 monster on your liftoff stage. The thrust to weight ratio determines if you lift off or not, and ion thrusters suck at TWR.)
posted by eriko at 1:35 PM on March 24, 2015


Would be nice if this could be retrofitted to existing sound cannons used for crowd control.
posted by ZeusHumms 6 ½ hours ago [+]

Sure, until someone accidentally flips the polarity and it turns the crowd into a riot that's on fire.
posted by VTX 6 ½ hours ago [3 favorites −] Favorite added!

Given the politics and proclivities of the increasingly hostile police forces around the country, such a polarity-flipping might not be so *accidental*
posted by flapjax at midnite at 4:45 PM on March 24, 2015


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