US Navy Patents A Sound Weapon?

[BPSCG]

This is making my BS detector ping, if you'll pardon the expression. (http://blog.wired.com/defense/2007/04/navy_patents_ca.html?huzzah)


Imagine a day when a submarine could blast a target to smithereens using nothing more than acoustic energy. That's the idea behind a recently granted U.S. Navy patent for a cavitation weapon. The powerful weapon would use sonar to generate "acoustic remote cavitation," i.e. a big pressure bubble, that would destroy everything from torpedoes to mines.

Why?

Not a news story - a blog;
The link to the alleged patent is to a video game;
I wasn't aware the US military patents its secret weapons;
As someone posted in response to the story, using a weapon that makes a ginormous noise would be kinda like broadcasting to everyone within a hundred miles, "Here we are!" which is something subs generally try to avoid doing.So, while I'm not ready to discount the story entirely, I'm wondering if anyone else knows more about it.

[Cuddles]

I suspect this is refering to this (http://www.newscientisttech.com/channel/tech/mg19426011.900-underwater-weapons--the-next-wave.html) New Scientist article. There are acoustic weapons being developed, and even some in use already. The vast majority are anti-personell and would have no chance of even damaging a ship, let alone destroying it. The general idea is that a low power warning could be sent out and then increase in intensity to force divers to surface. The worry about subs letting people know where they are is not a problem because these are designed as defenses to protect coastal facilities and ships from attack, and if someone is attacking it's a fair bet they alreay know where you are.

For some reason I can't access the blog, but I suspect it is simply exagerating things and adding a little futurism rather than actually being woo.

[Beady]

Is this a variation on The Brown Note?

[fuelair]

Not quite - but cavitation involves very small bubbles and intense temporary
heat. I am quite uncertain how you could use sound to generate the tiny bubbles and move them - and I am certain you could not generate the number/intensity needed to damage a ship. One big one hits scifi in my book.

[alfaniner]

Does this mean we'll eventually get to hear "Fire the Wave Motion Gun!!!"?

[Horatius]

http://www.google.com/patents?id=3PkTAAAAEBAJ&dq=cavitation+weapon


Searching on Google Patents for "cavitation weapon" found this. "Sonar weapon" and "sound weapon" only tuned up things like you'd expect - using sonar to guide weapons, or limiting the sonar detection of weapons fire.

This isn't quite what was described, but I could see someone misunderstanding it that badly. Sort of. Almost.

[Jackalgirl]

Howdy --

Not that I have much more to add here, but I'm looking at the OP's cited Wired mag article and it doesn't sound like Horatius' patent link at all (although the latter is really interesting). The quotes are pretty specific:

A method is disclosed of generating a predetermined field of cavitation around a remote target in an underwater environment. The method includes the steps of identifying a remote target location, generating at least two acoustic beams, each at a high power output, from an underwater acoustic source, and controlling the generated acoustic beams to intersect with each other at the remote target location and thereby create a destructive cavitation field at the intersection of the beams. The acoustic source and target can be located in unconfined underwater space and at a distance of at least 100 m apart.

It also quotes this:

The underlying physics is based on the intense heat and high-pressure pulse from the sonar sources 12, 14, and 16 as the damage mechanisms by virtue of the intense acoustic power of the sonar sources. An ensuing cavitation bubble formation and collapse and shock propagation will also inflict damages on underwater objects 18 targeted for removal. The technical drivers are the cavitation lethality on the undesirable objects 18 and the acoustic power of the sonar sources versus range and depth.

As a sonar tech, I'm...intrigued...by the amount of acoustic power that would be necessary to destroy a torpedo. That's what makes my BS detector go off.

Ah, found it. Here's the link to the patent, number 7,206,257 (http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.htm&r=2&p=1&f=G&l=50&d=PTXT&S1=(((acoustic+AND+beams)+AND+intersect).BSUM.+or+ ((acoustic+AND+beams)+AND+intersect).DETD.+or+((ac oustic+AND+beams)+AND+intersect).DRWD.)&OS=spec/(acoustic+and+beams+and+intersect)&RS=SPEC/((acoustic+AND+beams)+AND+intersect))

In the patent, they describe other technologies that either inspired them to do this, or that they're citing as supporting technologies -- things like using water jets to cut stuff, or sonics to clean stuff. Now, I am no scientist, but it seems to me like there might be a scaling error: sure, you can clean semiconductor wafers by putting them in a sonic bath, but I'm not sure that this translates into something that will destroy, say, a torpedo (and they mention that the stuff they cite works in regards to constrained environment, whereas they're designing something to work in free water).

Could someone take a look at Figure 3 (http://patimg2.uspto.gov/.piw?docid=US007206257&PageNum=4&IDKey=FB0DBFDEEBED&HomeUrl=http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2%2526Sect2=HITOFF%2526u=%25252Fne tahtml%25252FPTO%25252Fsearch-adv.htm%2526r=2%2526p=1%2526f=G%2526l=50%2526d=PTX T%2526S1=(((acoustic%252BAND%252Bbeams)%252BAND%25 2Bintersect).BSUM.%252Bor%252B((acoustic%252BAND%2 52Bbeams)%252BAND%252Bintersect).DETD.%252Bor%252B ((acoustic%252BAND%252Bbeams)%252BAND%252Bintersec t).DRWD.)%2526OS=spec/(acoustic%252Band%252Bbeams%252Band%252Bintersect) %2526RS=SPEC/((acoustic%252BAND%252Bbeams)%252BAND%252Bintersec t)) and help me understand it? I'm not smart enough to understand what that chart -- supposed to show what the acoustic power requirements are at various depths and 30kHz -- is saying. What I'd like to do is translate that into a required decibel level...

[Bob Klase]

I'm not sure- is the U.S. Navy (or any other part of the U.S. government) even allowed to patent something? I don't think so. I'm sure that the federal government can not copyright anything. Any patents would have to be applied for by a private company- perhaps contracted by the navy, but the patent would belong to the company and not the navy or the government.

[Slimething]

Some secret weapon! I saw a movie (http://en.wikipedia.org/wiki/The_Incredible_Mr._Limpet)about it when I was a kid.

[Jackalgirl]

I'm not sure- is the U.S. Navy (or any other part of the U.S. government) even allowed to patent something? I don't think so. I'm sure that the federal government can not copyright anything. Any patents would have to be applied for by a private company- perhaps contracted by the navy, but the patent would belong to the company and not the navy or the government.

Good question; I'm not sure. The inventor is, as listed on the patent, "Meng; James C. S. (Poulsbo, WA) (http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.htm&r=2&p=1&f=G&l=50&d=PTXT&S1=(((acoustic+AND+beams)+AND+intersect).BSUM.+or+ ((acoustic+AND+beams)+AND+intersect).DETD.+or+((ac oustic+AND+beams)+AND+intersect).DRWD.)&OS=spec/(acoustic+and+beams+and+intersect)&RS=SPEC/((acoustic+AND+beams)+AND+intersect))". But the assignee is "The United States of America represented by the Secretary of the Navy".

[fuelair]

Good question; I'm not sure. The inventor is, as listed on the patent, "Meng; James C. S. (Poulsbo, WA) (http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.htm&r=2&p=1&f=G&l=50&d=PTXT&S1=(((acoustic+AND+beams)+AND+intersect).BSUM.+or+ ((acoustic+AND+beams)+AND+intersect).DETD.+or+((ac oustic+AND+beams)+AND+intersect).DRWD.)&OS=spec/(acoustic+and+beams+and+intersect)&RS=SPEC/((acoustic+AND+beams)+AND+intersect))". But the assignee is "The United States of America represented by the Secretary of the Navy".

And, when I mentioned this to my wife, she told me about a neighbor her family had had ca 40-50 years ago who was a Navy Officer - handling Patents and patent law for the Navy - especially as related to systems, potential infringement and near end of protection maneuvers.

[Cuddles]

I'm not sure- is the U.S. Navy (or any other part of the U.S. government) even allowed to patent something? I don't think so. I'm sure that the federal government can not copyright anything. Any patents would have to be applied for by a private company- perhaps contracted by the navy, but the patent would belong to the company and not the navy or the government.

They definately used to be able to. Read Feynman's stories about Los Alamos, where any ideas about applications for nuclear energy were bought by the government for a dollar so that thye could be patented by the government rather than the workers.

[Cuddles]

Looking at the patent, I can't see anything about power levels needed, but I suspect they would be rather high. However, the New Scientist article says that the purpose of most acoustic weapons (and I think they refer to this one) isn't to destroy anything but to simply prevent humans (or other animals) from getting close to things or sabotaging them. The power needed to sink a ship might be too high, but using the same technique to incapacitate a diver wouldn't be all that hard.

Edit: Incidentally, I particularly liked this part of the patent:
The underwater object 18 targeted for destruction is shown generically in FIG. 1 and may include mines, incoming torpedoes, marine fouling barnacles, and emergency rescue operations.
Specicially designed for destroying rescue operations. :)

[Horatius]

Could someone take a look at Figure 3 (http://patimg2.uspto.gov/.piw?docid=US007206257&PageNum=4&IDKey=FB0DBFDEEBED&HomeUrl=http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2%2526Sect2=HITOFF%2526u=%25252Fne tahtml%25252FPTO%25252Fsearch-adv.htm%2526r=2%2526p=1%2526f=G%2526l=50%2526d=PTX T%2526S1=(((acoustic%252BAND%252Bbeams)%252BAND%25 2Bintersect).BSUM.%252Bor%252B((acoustic%252BAND%2 52Bbeams)%252BAND%252Bintersect).DETD.%252Bor%252B ((acoustic%252BAND%252Bbeams)%252BAND%252Bintersec t).DRWD.)%2526OS=spec/(acoustic%252Band%252Bbeams%252Band%252Bintersect) %2526RS=SPEC/((acoustic%252BAND%252Bbeams)%252BAND%252Bintersec t)) and help me understand it? I'm not smart enough to understand what that chart -- supposed to show what the acoustic power requirements are at various depths and 30kHz -- is saying. What I'd like to do is translate that into a required decibel level...

Looking at the patent, I can't see anything about power levels needed, but I suspect they would be rather high.



That's what Fig. 3 seems to be showing - Power needed at various ranges and depths. Note that the power scale is in MW (megawatts), which seems a bit unrealistic for a portable device.


It's interesting to note, from a patent examiner's point of view, that the cited references on the front page all seem to be the same references the inventor cites in his description, which leads me to suspect the examiner did a half-assed job on this one. So, consider it in that light.

He also talks about ranges up to 1km, but fig. 3 only goes up to 500m. I wouldn't have let him get away with that :)

[robinson]

There have been multiple reports of whale and dolphins beaching themselves after Navy exercises in the area. One autopsy showed extreme damage to the inner ears of dead whales.

Hmm....

[Jackalgirl]

That's what Fig. 3 seems to be showing - Power needed at various ranges and depths. Note that the power scale is in MW (megawatts), which seems a bit unrealistic for a portable device.

I've been looking at the various sources of information (found via Google -- I'm lazy) regarding power <--> deciBel and I'm afraid I'm still rather clueless. I know that dB is a comparison -- it is a ration between two power levels, yes? So how does it work -- if you output, say, 30 kHz into the water at x MW, what will the sound intensity be? It's the ratio between the power you're outputting and a reference power level, is that correct? I just want to make sure I'm understanding this system correctly (I may be a sonar technician, but I am also an art major -- not to pooh-pooh art majors, but I am stereotypical in that the advanced mathematical concepts are beyond me).

[Horatius]

I've been looking at the various sources of information (found via Google -- I'm lazy) regarding power <--> deciBel and I'm afraid I'm still rather clueless. I know that dB is a comparison -- it is a ration between two power levels, yes? So how does it work -- if you output, say, 30 kHz into the water at x MW, what will the sound intensity be? It's the ratio between the power you're outputting and a reference power level, is that correct? I just want to make sure I'm understanding this system correctly (I may be a sonar technician, but I am also an art major -- not to pooh-pooh art majors, but I am stereotypical in that the advanced mathematical concepts are beyond me).



This isn't something I know anything about, unfortunately. But I figure, if you're putting in megawatts, however you convert it, it's going to be loud. Unless your conversion efficiency really sucks.


http://tokyo.usembassy.gov/e/p/tp-20060417-72.html

Operation of naval reactors is also different from that of commercial reactors because of the different purpose they serve. First, naval reactors are smaller and lower in power rating than typical civilian reactors. The largest naval reactors are rated at less than one-fifth of a large U.S. commercial reactor plant. Also, naval reactors do not normally operate at full power. The average power level of reactors on nuclear-powered aircraft carriers over the life of the ship is less than 15% of their full rated power. In contrast, commercial reactors normally operate near full power.


I know most commercial plants are about 1000MW reactors, so a naval reactor would likey be about 200MW. Looking at fig. 3 again, they go up to about 60MW. So you'd need around a quarter of the maximum output of your reactor. A lot, but maybe doable.

[Jackalgirl]

...I know most commercial plants are about 1000MW reactors, so a naval reactor would likey be about 200MW. Looking at fig. 3 again, they go up to about 60MW. So you'd need around a quarter of the maximum output of your reactor. A lot, but maybe doable.

I wonder if, at that point, you'd be successful in transmitting a sound pulse that far, or simply end up boiling the water by your transducer array. I understand that the point of the device is to cause an effect in a small area produced by the convergence of two sound energy lobes (i.e., a constructive effect area), but I still have to imagine that the power requirements for producing even one of these lobes would be pretty high, and thusly the energy transmitted to the water would be high.

I dug through <a href="http://en.wikipedia.org/wiki/Decibel">Wikipedia entry on decibels</a> and there's a formula in there for converting Watts to decibels. It works out that 1kW = 30 dB, and that "[i]t will be seen that there is a 10 dB increase (decrease) for each factor 10 increase (decrease) in the ratio of X [ the input watt level ] to X0 [ the reference watt level, in this case, 1W ], and approximately a 3 dB increase (decrease) for every factor 2 increase (decrease)."

I can't get the formula to work out very well; the calculator is telling me that 60 MW is about 77 dB (which sort of squares with a rough estimate of the number of 10-fold increases from 1 thousand to 10 million - I chose 10 million instead of 60 million because it's easier for this poor art major to comprehend). That doesn't seem right. I mean, 77 dB? The threshold for pain / damage in a human is, what, 80dB? TWICE as loud as something using 60 MW of power? What am I doing wrong? : (

(I realize that we'll eventually be talking about sound levels in water, which are different than sound levels in air. But I still feel like I'm majorly messing something up)

[NoZed Avenger]

MMMMMaaaaaaaaauuuuuuuuuuuuddd - DiiB!

[ktesibios]

Decibel measurements always express a ratio between two quantities. Decibels can be used to express an absolute quantity e.g. sound pressure, voltage, power etc. only as the ratio of that quantity to a reference, and the reference must be specified.

For example, it's correct to say that 1 kW = +30 dBW (read as "decibels referred to one watt", or if you're in a hurry, "dee-bee-doubleyou"). Similarly, 1W = 0 dBW and 1 mW = -30 dBW.

To say that 1 kW = 30 dB is meaningless.

Some other common reference levels used for electrical quantities are the dBm (dB referred to 1 mW, used by RF engineers and the phone company), dBV (dB referred to 1 volt) and dBu (dB referred to the voltage that will produce 1 mW of power in a 600 ohm resistance, or sqrt(0.6) volts), both of which are used in pro audio.

For sound pressures, the standard reference level for sound propagating in air is a pressure variation of 20 uPa RMS, which corresponds to an intensity of 1*10-12 W/m2.

In water, the standard reference level is different- 1 uPa. Because the characteristic acoustic impedance of water is around 3600 times that of air, this corresponds to an acoustic intensity of approximately 6.75*10-19 W/m2.

For power ratios, dB = 10*log10(p1/p2)
For voltage, current or pressure ratios, dB = 20*log10(v1/v2)

You can calculate the acoustic intensity produced by a sound source at a given distance if you know the acoustic power output and directivity of the source- divide the power by the surface area of a sphere having a radius equal to the distance and multiply by the directivity. To express this in dB SPL (sound pressure level) divide the result by the reference acoustic intensity, take the common log of the quotient and multiply by 10.

This neglects the effect of power dissipation in the air or water (what acousticians call "excess attenuation") and assumes that the measurement is being taken on the axis of greatest intensity, if the source is directional.

[teemacs]

I'm not sure- is the U.S. Navy (or any other part of the U.S. government) even allowed to patent something? I don't think so. I'm sure that the federal government can not copyright anything. Any patents would have to be applied for by a private company- perhaps contracted by the navy, but the patent would belong to the company and not the navy or the government.

The short answer is, yes, the US Government and its various agencies and departments are in no way inhibited from appliying for intellectual property rights. Moreover, as the United States is now a sigantory of the Berne Convention, copyright is automatic in any written work - there is no need to apply for it. (The United States still maintains a registration mechanism for copyright, by which you can apply for it, and this gives certain advantages in the USA over straight Berne Convention copyright).

[Soapy Sam]

I'm not sure- is the U.S. Navy (or any other part of the U.S. government) even allowed to patent something? I don't think so. I'm sure that the federal government can not copyright anything. Any patents would have to be applied for by a private company- perhaps contracted by the navy, but the patent would belong to the company and not the navy or the government.

John von Neumann famously assigned the patent on the nuclear chain reaction to the British Admiralty.
All your atom bombs are belong to us.

[Tez]

what the heck is the pistol shrimp ( http://en.wikipedia.org/wiki/Pistol_shrimp ) going to do with all those royalties?

[teemacs]

John von Neumann famously assigned the patent on the nuclear chain reaction to the British Admiralty.
All your atom bombs are belong to us.

Mr. von Neumann had nothing to do with the first chain reaction, so I doubt whether he ever filed a patent application:

http://hep.uchicago.edu/cp1.html