Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Magnetoelectric antennas could transform how underwater robots talk

newatlas.com

Post reply on HN
Print view View original

21–30 of 37 posts

Re: Magnetoelectric antennas could transform how underwater robots talk

#21

Post by miduil »

cyanydeez wrote: post #2

youd think optic fiber like Ukraine is diing would be viable to some extent.

I was just looking into the topic recently, there is a decent graphic explaining how fiber is already used for submarine communication for quite some time.

Page 13 shows the diagram of an undersea fiber network separating into durable heavy and lightweight wires.

    Sea surface
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        |
        | near-surface armored cable
        |
     [Depressor]
          \
           \  fiber cable
            \  0.010 inch diameter
             \ up to 40 km long
              \
            [Float pack]
                 \
                  \ 50 m secondary cable
                   \
                 [Vehicle]
https://sundowner.colorado.edu/seefeldt/ptc-2005_2016/2013_p...

Re: Magnetoelectric antennas could transform how underwater robots talk

#22

Post by raffael_de »

XorNot wrote: post #20
raffael_de wrote: post #8

Earlier quoted context omitted.

But isn't torpedo steering still dependent on wire?

The issue is it doesn't really matter and radio isn't much benefit: you get much higher bandwidth, better reliability, immunity to ECM, and fiber-optic wires in Ukraine are over 50km long. The exact application for this is autonomous underwater vehicles where what you would like to do is communicate quickly and without a tether in arbitrary scenarios - i.e. think a bunch of autonomous vehicles which might need to rel…

fair enough but afaik torpedoes aren't tethered by a fiber optic cable like drones. it's a much thicker cable that possibly contains a fiber optic cable.

Re: Magnetoelectric antennas could transform how underwater robots talk

#23

Post by ninalanyon »

mcswell wrote: post #19
adrian_b wrote: post #11

Earlier quoted context omitted.

When a wave passes through different media, its frequency remains the same, but its velocity changes. The wavelength is the ratio between velocity and frequency, so it changes proportionally. If you multiply 36 kHz by 8326 m, you get a value only slightly less than the speed of light in vacuum, which is true for the propagation of electromagnetic waves in most gases. On the other hand, with 170 m, you will get a spee…

I tried to do a little (web) research on this. It is of course the reason a prism separates white light into its components. I didn't find out much about sea water, though. And then there's "slow glass", in which the passage of light through half an inch of glass takes years; the subject of the short story "Light of Other Days" :).

One of my favourite stories, heartbreaking though it is.

Arthur C. Clarke and Stephen Baxter wrote a novel of with the same title, but the two stories have nothing in common. It's worth a read in these surveillance heavy times.

Re: Magnetoelectric antennas could transform how underwater robots talk

#24

Post by m4rtink »

Klaus23 wrote: post #14
raffael_de wrote: post #6

my first association here would be steering of torpedoes. the US Navy must have been on this for decades and very deep pockets.

Torpedoes are usually steered using fibre-optic wires, like the fibre-optic drones in Ukraine today, so there is no need for problematic low-frequency radio.

Terminal homing phase sub-torpedo drone swarm use case for this ? ;-)

Re: Magnetoelectric antennas could transform how underwater robots talk

#26

Post by DoctorOetker »

this transduces between magnetic acoustic electric domains, via acoustic pressure.

does this result in some acoustic side channel emissions? can an adversary track subs by correlating acoustic with EM noise if this were employed on second strike submarines?

conceptually its like a 3 port device: a magnetic port, an electric port and an acoustic port.

One would be especially interested in the scattering parameters S_mag-acou , S_acou-mag , S_elec-acou, S_acou-elec at the used frequencies, for passive detection, and for wider frequency range for active detection...

Re: Magnetoelectric antennas could transform how underwater robots talk

#27

Post by vitally3643 »

DoctorOetker wrote: post #26

this transduces between magnetic acoustic electric domains, via acoustic pressure. does this result in some acoustic side channel emissions? can an adversary track subs by correlating acoustic with EM noise if this were employed on second strike submarines? conceptually its like a 3 port device: a magnetic port, an electric port and an acoustic port. One would be especially interested in the scattering parameters S_m…

One of the most challenging thing about submarine communications is that EM waves don't propagate through water. To communicate from the surface to a submarine, we use radio waves on the order of 100Hz, with incredibly large antennas running at very high power. Submarines cannot communicate back without sending a more conventional antenna up to the surface.

Acoustics is the entire game under water. You can only detect nearby objects with visible light or sound. A great deal of submarine design goes into minimizing the amount of sound emitted into the environment because water is astonishingly good at transmitting sound waves very long distances with little loss.

Re: Magnetoelectric antennas could transform how underwater robots talk

#28

Post by rpaddock »

In World-War-One J.H.Rogers invented and patented an antenna that worked well underground or underwater. It was used to communicate with Subs at the time.

According to the late, and somewhat controversial, T.E.Bearden the Rogers system has been rediscovered and then "lost" at least five times since WW1.

"James H. ROGERS Underground & Underwater Radio ( Static-free Reception & Transmission Underwater & Underground )"

https://www.rexresearch.com/rogers/1rogers.htm

There is also

Wallace MINTO Hydronic Radiation Transmitter

Radio-Electronics (May, 1967), p. 37-38.

“Build a Hydronic-Radiation Transmitter”

by Jack Althouse

“Scientists in Florida have discovered a new form of electromagnetic radiation which propagates under water as well as radio does in air”.

https://www.rexresearch.com/hydronics/hydronics.htm

While not indented for water use the Sutton & Spaniol et.al.'s "Black Hole" Antenna is always of interest when it comes to VLF/ELF. This work was done for NASA. Dr Sutton described it to me this way:

"Re: ACTIVE ANTENNA From: John and Helen Date: 10/02/05 10:54 pm

Hi Bob,

The synchronous detectors were used in temperature monitors and temperature controllers designed to control temperatures on spacecraft at 60 milliKelvin +/- a few ucroKelvin. The preamplifier had to have a gain of 10E5 after which the demodulated signal had to be converted by a 16 bit ADC, with +/- 1LSB allowable error.... so of course, you can see that we were working with extremely small signals buried in the noise, and we had to go all out in an effort to beat down the noise. That's why we had to use a new improved synchronous demodulator. This project was as close to being impossible as you can get! I still have trouble believing that we actually made it work.

The active ("Black Hole") antenna was developed in another project, where we didn't want to transport a two meter long antenna that weighed 200 pounds.....so we miniaturized the hardware while simultaneously expanding the antenna field cross section. We wanted to receive the entire ELF-VLF bands all at once, so we had to have an extremely broadband antenna....like four decades of bandwidth or more. You wouldn't believe the arguments I had with the reviewer at Physics Essays. He just couldn't believe that one could do what we did....and if it was indeed true, then why hadn't someone done it years ago?.., "and what makes you so smart", .so, of course, "this must be nonsense, etc....." Progress in physics is so bloody difficult because most physicists think that everything worthwhile has already been discovered....so they expect nothing new. This is negative feedback which, of course, makes the system stable, I suppose.

The one text book that includes diagrams of the antenna-external field interaction is listed as one of the references in the Physics Essays paper. Sorry, I can't remember the name of the author or the title.

John Sutton, Ph.D."

https://web.archive.org/web/20120722112702/http://www.unusua...

Re: Magnetoelectric antennas could transform how underwater robots talk

#29

Post by Klaus23 »

m4rtink wrote: post #24
Klaus23 wrote: post #14

Earlier quoted context omitted.

Torpedoes are usually steered using fibre-optic wires, like the fibre-optic drones in Ukraine today, so there is no need for problematic low-frequency radio.

Terminal homing phase sub-torpedo drone swarm use case for this ? ;-)

As funny as your comment sounds, I wouldn't rule out the Ukrainians actually doing it. At least for sea+air and air+air, sub-drones are already a reality.

Re: Magnetoelectric antennas could transform how underwater robots talk

#30

Post by pineaux »

vitally3643 wrote: post #27
DoctorOetker wrote: post #26

this transduces between magnetic acoustic electric domains, via acoustic pressure. does this result in some acoustic side channel emissions? can an adversary track subs by correlating acoustic with EM noise if this were employed on second strike submarines? conceptually its like a 3 port device: a magnetic port, an electric port and an acoustic port. One would be especially interested in the scattering parameters S_m…

One of the most challenging thing about submarine communications is that EM waves don't propagate through water. To communicate from the surface to a submarine, we use radio waves on the order of 100Hz, with incredibly large antennas running at very high power. Submarines cannot communicate back without sending a more conventional antenna up to the surface. Acoustics is the entire game under water. You can only detec…

And a lot faster than on land. 5 times if I recollect correctly.
Post reply on HN