It’s been my understanding, born of Tom Clancy novels and general reading, that radio waves do not significantly penetrate water. How would a radio-guided torpedo be possible?
I have long known of Hedy Lamarr’s patent involving radio, but never heard of the torpedo connection until now. Obviously if it’s impossible for a torpedo to receive radio transmissions underwater, that would cast doubt on this torpedo connection and perhaps explain why I’d not see it until now.
I suppose the key is how deep radio emission can penetrate into water and still be suitably clear to guide a weapon, and how deep torpedoes run.
It all depends on the wavelength of the signal. If the wavelength is long enough, it can penetrate a fathom or three, and that is plenty deep enough for most torpedo use.
You are correct; radio waves do not work well underwater. However, this is frequency-dependent–the lower the frequency, the more the penetration (and vice-versa).
The idea might be workable work for torpedoes travelling at a shallow depth (for transmitters above the surface) or for deeper torpedoes at distances relatively close to an underwater transmitter, if the frequency was low enough.
But, the lower the frequency, also the lower the “through-put” as it were. IOW, the longer it takes to send x amount of data, and torpedoes kinda need more than x amount every y couple of seconds!
The very low frequency systems that are used to communicate with submerged subs can take an hour to send a short message (and use antenna which are miles long)!
There would need to be tradeoff between rate of data transfer and depth/distance of water to be traversed.
You are now mixing up apples and oranges. There are a variety of low frequency systems, of which ELF (the system you are describing) is only one. An ELF system would clearly not be workable due to the low rate of data transfer, size constraints on the receiving antenna, the power requirements on the sending antenna, and the power generating station needed to generate and transmit the signals (at very low efficiencies) thousands of miles through the Earth’s crust and across the oceans. That’s not what we’re talking about here.
A VLF or an LF system, on the other hand, would work just fine (in theory) for the application being discussed.
Just how much information do you think a torpedo needs? A firing solution is generated before the fish is launched, and would only need a little tweaking to adapt to evasive actions of the target.
Big boats do not change their course and speed easily or quickly.
Given the huge advancements they’ve made with UAVs, they’re literally autonomous now, I would think this would be a more practical approach. Putting a much more sophisticated AI system into a torpedo. One that could let it travel hundreds of miles, recognize IFF signals, etc. Essentially be a UUV!
You what now? Since when do ships have underwater IFF? I know ships tend to have pretty recognizeable signatures, but I’d be a bit nervous about setting a torpedo/UUV to destroy something matching an an enemy gas-turbine frigate and then turning it loose to roam the seas, bearing in mind that all MY gas-turbine frigates might suffer as a result.
At the turn of the last century, Tesla was working on and demonstrating radio controlled torpedoes. Indeed it was part of the research and development he did that allowed for the overturning of Marconi’s patents.
What if many low frequency signals (each with their own frequency) were used to increase the amount of information transmitted per second, seems like that would work.
Updated telemetry at least on the order of 1 Hz; boats may not change vectors quickly, but the game between a submarine and a conventional torpedo is closer to a game of chess than a dogfight; torpedoes are often fired at significant range (too close and the boat being attacked will just fire back, both boats will cut control wires and launch countermeasures, and the odds of interception are low) and a boat can well evade by going beyond torpedo range, ducking under a sonar-reflecting thermocline, getting lost in surface scatter, et cetera. (Those scenes you see in the film adaptation of The Hunt For Red October with Ramius overrunning in a preplotted course and later playing chicken with another sub are pure nonsense; no sub commander who wasn’t terminally suicidal would ever attempt such a thing.)
Conventional torpedoes are controlled via control wires that are fed out with the fish, and modern torpedoes have internal sonar and automated guidance and tracking systems that permit the fish to go solo when the wires are cut; one technique for driving away an attacking sub is to launch a fish without lines and then turn and run, forcing the opponent to do the same.
The Soviets (now Russian Navy) do have a supercavitating torpedo (basically a torp with a small solid rocket motor on the tip that creates and sustains a drag-reducing bubble around the fish) which permits it to go at extraordinary speeds (estimated in excess of 200nmh–conventional prop-driven torps go at about 40-45 nmh, and modern prop-less torpedos can run at about 60 nmh, faster than even the vaunted Soviet Navy Alfa “interceptor” submarine). The original supercavs (‘Shkval’) were just straight-line fish with no maneuvering capability; they’re held off of the surface of the bubble by a set of rotating fins, essentially dancing on the water. (They were designed to carry nuclear depth charges to be detonated within a carrier group, so fine maneuvering capability was unneeded.) Newer ones are alleged to be able to effect maneuvers and even rapid turns without collapsing the bubble; obviously, at these speeds the control wires would introduce substantial drag and thus be undesirable; a low frequency radio controlled system (using high compression telemetry) would be necessary to control this; the fish obviously couldn’t self-direct using on-board sonar for obvious reasons. Other nations are also work on supercavitating torpedoes and even (supposedly) submarine torpedo-launched cruise missiles which pop up in littoral zones and effect a NOE flight course, making them virtually undetectable and unstoppable except by “look down/shoot down” defense. There is nothing in the US arsenal that does this, but I have to believe that the Navy has contractors working on this frantically in some kind of black program.
Radio doesn’t transmit very effectively underwater, as discussed above, but an satelllite-based intense laser of the right frequency to pass through sea water could theoretically penetrate hundreds of feet, assuming you have a clear surface and adaptive optics to compensate for atmospheric turbulence and variable refraction from changes in salinity due to depth. It might be possible to control a fish by communicating from boat or remote station to satellite to torpedo.
Lamarr’s scheme was essentially a variation of frequency division multiplexing, which is easy to implement today but virtually impossible to do with the electromechanical systems of the day in a practical manner. It is highly suspected that Lamarr did not develop this entirely herself (or rather she and composer George Antheil, her co-awardee of the American patent), but rather ‘acquired’ it from her German ex-husband and allowed to patent it to support the war effort and avoid patent conflict issues.
Most UUVs use acoustic modems to communicate with their operator while underwater. They’ll also have an RF link for use when at the surface (usually to get a GPS nav fix).
If the vehicle is smart enough not to need an operator control loop, it’s called an AUV (Autonomous vs Unmanned). They’ll still typically have an acoustic modem and RF link to report back as needed. Of course AUVs with weapon payloads (as opposed to the sensor payloads I’m familiar with) have less of a need to call home.
Stranger, I’m not going to comment on the details of your post for obvious reasons, other than to note that you are a true polymath. There seems to be no limit to the range of subject matter on which you can expound.
One nitpick–the unit “nmh (nautical miles per hour)” is more commonly referred to as a “knot.”
I’m not so much on celebrity gossip or 19th Century bisque dolls. In fact, there is a vast array of things I’m totally unqualified to speak about, which I conceal by (mostly) not writing on thos topics.
True, but the standard in-jargon abbreviations (kt or kn) tend to get confused for other units. nmh is unambiguous and frequently used in technical literature (at least in aerospace industry).
