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In a semi futuristic setting electronic warfare has advanced to the point that complex wireless guidance systems are nearly useless. As such most combat in space takes place at or close to visual range. To get around this, torpedoes must be physically connected via a long and very thin wire so that the launch vessel can transmit corrections back to the torpedo without being jammed. I have looked at various cold war era wire guided torpedo designs and the lengths of these wires appear to be around 20-30km, after that the torpedo would have to rely on its own onboard navigation system, continue on its last known vector or simply detonate when severed. 20-30km is far too short for any torpedo to be of much practical use in space combat.

Question: How long could these wires potentially be made, and what (known) material would they need to be made of? What are some potential weaknesses of this system?

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    $\begingroup$ Couple of points. 1.) I think the 20-30 km is already a really high number and you might want to say where you have your source for that - I can find a 4 km as the limit. en.wikipedia.org/wiki/…). 2.) Wire-guided missiles are primarily launched from essentially stationary platforms (tanks, trucks, shoulders), as any maneuver would snap most wires. You will, however, get better performance in space, without air resistance. $\endgroup$
    – DWKraus
    Jan 22 at 20:21
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    $\begingroup$ The wires might be 20-30 km long, but that's because they are loose, unspooling freely, and you need a lot more wire than the distance covered. $\endgroup$
    – DWKraus
    Jan 22 at 20:25
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    $\begingroup$ Have you considered laser-guided missiles? No electronic signal, just painting your target and letting the torpedo home in on the laser spot. $\endgroup$
    – DWKraus
    Jan 22 at 23:33
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    $\begingroup$ put the guidance system in the torpedo. before it launches it gets target data, then it is on its own. we do that now. $\endgroup$
    – John
    Jan 23 at 14:53
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    $\begingroup$ Bradley, please keep in mind for future questions that you're supposed to focus on just one question. In fact, one of the vote-to-close reasons (Needs More Focus) is specifically identified as asking multiple questions - and you've asked three. No big deal today, please just keep it in mind. $\endgroup$
    – JBH
    Jan 23 at 21:35

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As such most combat in space takes place at or close to visual range.

Visual range in space is a long, long way. A visible light telescope in space is effectively only restricted by diffraction limits.

Making a wire that can control a missile intended to cross those long distances (hundreds of kilometers, at a minimum!) is going to be exceptionally difficult... that wire is going to to be comparatively delicate and vulnerable, and the thrust of a projectile intended to cross that distance promptly is going to be quite destructive.

torpedoes must be physically connected via a long and very thin wire so that the launch vessel can transmit corrections back to the torpedo without being jammed.

Space, being a fairly good vacuum, is an excellent medium for transmitting light through (which is why "visual range" is such a long way). Without atmospheric interference, a nice light laser beam can be focussed on a receiver array on your torpedoes, allowing easy unidirectional communication which is impractical to jam. A sufficiently large and capable torpedo could have its own return communication laser, if such a thing seemed to be necessary.

Whilst it is entirely reasonable to have a setting without practical laser weaponry, handwaving laser communication away is going to be dubious unless you're going to back to von Braun era technology.

electronic warfare has advanced to the point that complex wireless guidance systems are nearly useless

Be aware of the existence of anti-radiation missiles, and consider the future evolution of things like suppression of enemy air defenses. Jamming and ECM isn't a magic bullet, and compromises will need to be made between jamming enemy fire control systems, and avoiding getting an anti-radiation missile or two right up the phased arrays.

As a simple starter-for-ten, consider launching a screen of untethered anti-radiation missiles, followed by some more conventional guided missiles. If your target lights up their ECM systems, the anti-radiation missiles have something to lock on to. If they light up point-defense radar systems, the same thing happens again, except now they have to engage both the guided missiles and the anti-radiation missiles. If they don't use radar or ECM, the guided missiles will finish them off.

Obviously, no plan survives contact with the enemy and all that, but do bear these little wrinkles in mind.

visual range

Optical sensors are also vulnerable to jamming. If I illuminate the aperture of your telescope with a laser, I might not be able to blow you up with it (depending on tech level assumptions) but I can certainly stop you looking at me through it.

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  • $\begingroup$ I could also imagine the problem of having, oh, let's say... 50 ships engaged in a battle, each releasing 20 torpedoes, which means there are 1,000 strands of 100Km+ wire being dragged around the battlefield (long enough lengths to touch other ships!). Can you imagine someone on board one of the ships saying, "You know, I remember reading in my college Ancient History class where this defunct intelligence agency called the CIA used something called Skyhook...") or, worse, all those strands tying themselves into a knot that actually affects the outcome of the battle. $\endgroup$
    – JBH
    Jan 23 at 21:49
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    $\begingroup$ @JoinJBHonCodidact I like the idea of the intersection of kite fighting and space combat, though ;-) $\endgroup$ Jan 23 at 21:54
  • $\begingroup$ To be honest I completely spaced on laser communication. I think how I'll have it work is that the older torpedoes use very thin (several atoms wide) and long superconducting wires for guidance but the newer ones use laser communication. Torpedoes are guided by the ship toward the general direction of the enemy and then the simple onboard homing system takes over and finishes the journey. Thank you for your valuable insight! $\endgroup$
    – Boo Radley
    Jan 24 at 17:00
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If all combat is at visual range, firing torpedoes is suicidal. Without an atmosphere to contain debris, stuff will spread at ludicrous speed in all directions. This turns torpedoes more of a M.A.D. thing.

If you avoid that Kessler hell, then consider that light is still faster than torpedoes. Joke's on you, as soon as they see the tip of your torpedoes, they can blow the torpedoes' payload with lasers and there is no ECM for that.

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    $\begingroup$ Come on laser destruction of a projectile is not that easy $\endgroup$ Jan 22 at 21:34
  • $\begingroup$ If they can destroy torpedoes with their lasers as soon as they leave the tubes of the enemy ship, why aren't they using their lasers on the enemy ship directly? $\endgroup$ Jan 23 at 10:48
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    $\begingroup$ @DarthBiomech mission-killing a missile will be a bit easier than mission-killing a warship. The answer, though, is to use high velocity dumb unguided projectiles that can't be mission-killed without being vaporised, making lasers less effective. Railguns and coilguns FTW. $\endgroup$ Jan 23 at 12:43
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    $\begingroup$ Would that actually be true? Using a focused charge against the thrust of the torpedo might not be as suicidal as you claim. In fact, if you could get the torpedo to penetrate the ship and then release a focused charge, you'd be blowing a hole out the other side. (Consequently, is this really an actual answer to the question, or is it a comment in answer form?) $\endgroup$
    – JBH
    Jan 23 at 21:37
  • $\begingroup$ @JoinJBHonCodidact this will lead to very fragile ships being deployed as MAD measures. Torpedo them and they won't contain the charge, so you get Kessler hell anyway. $\endgroup$ Jan 24 at 4:16
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These are skinny-assed wires.

https://www.zdnet.com/article/quantum-leap-the-worlds-thinnest-silicon-wire/

MELBOURNE -- A new study published last week in the journal Science has unveiled the creation of the world's thinnest wire, measuring only four atoms wide and one atom tall.

The breakthrough study showed that the fabricated wires could hold the same electrical current carrying capability of copper, and that the electrical resistivity of the wires (I~0.3 milliohm-centimeters) did not depend on the wire width.

The wires, about 10,000 times smaller than a strand of human hair, were developed by Mr Bent Weber from the Centre for Quantum Computation and Communication Technology (CQCCT) at the University of New South Wales.

These atomic sized wires are able to carry current sufficient to convey commands to the torpedo and carry blurry pictures from the torpedo back to the origin.

The wires are pretty weak. They have plastic coatings to help strengthen them. They are still invisibly strong and useful only in space. It was a trick to unspool them from the torpedo without cracking them and sometimes they still crack. That is why they use 3 wires not just one.

The wires are a million km long. They are so astoundingly thin that the reel is still just a few cm thick. Signal fidelity remains strong even at a million km which is their advantage over laser signals.

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    $\begingroup$ (1) Resistivity is one thing, and resistance is a very different thing. Resistivity, true, does not depend on wire diameter; this is as true of copper as it is of this fancy wire. Resistance, on the other hand, is inversely proportional with the square of the diameter. Those extremely thin wires will have very high electrical resistance. (2) Old joke: at the universal exhibition, the Germas show the world's thinnest wire, 1/10,000 of a human hair. The Japanese take the wire and return it the next day with a hole down the middle. The Swiss take the wire and apply a screw thread to the hole. $\endgroup$
    – AlexP
    Jan 22 at 23:07
  • $\begingroup$ @AlexP - hm. I did not know that (about resistivity vs resistance, or about the Swiss). I wonder if any meaningful signal could traverse such a wire. $\endgroup$
    – Willk
    Jan 22 at 23:10
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    $\begingroup$ At those dimensions the structure kind of acts like a waveguide but yes a signal can be carried. There are some experiments that are relatively easy to do where you can measure the conductance of a relay contact, and as the relay arm leaves the contact pad and for a small amount of time you have a small wire of a few atoms in diameter and ultimately only an atom or two carrying the signal. What is interesting is that you can also see how the conductance is quantized in units of planks constant. $\endgroup$
    – UVphoton
    Jan 23 at 3:23
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    $\begingroup$ Lasers excel at long-range communications. The LLCD experiment demonstrated a 622 Mbps link across 385000 km. The Psyche mission will have a laser link, and it's likely the next relay-capable Mars satellite will as well. Lasers will far outperform a long wire. $\endgroup$ Jan 23 at 16:13
  • $\begingroup$ @ChristopherJamesHuff - Agreed. All things being equal lasers would be better than a wire. Radio would be better than lasers. But OP states "complex wireless guidance systems are nearly useless" which I read to include anything without a wire which is all EMR. $\endgroup$
    – Willk
    Jan 23 at 16:52
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Noise induction

If a wireless guidance systems can be jammed, then a wired guidance systems can be failed by inducing noise by radio frequency radiation.

Shielding

If you shield the wires, the wires will be thick and heavy.

cut wires with lasers

The Square-Cube Law says,

they can blow torpedoes' payload with lasers

totalMongot says

laser destruction of a projectile is not that easy

How about if they cut wires with lasers?

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  • $\begingroup$ I think getting lasers focussed on the wires might be quite awkward, due to depth-of-field issues and the awkwardness of focussing down to a nice tight spot on something you can't actually see and aren't entirely sure of the location of. Not impossible, but probably not worth trying. $\endgroup$ Jan 23 at 12:40
  • $\begingroup$ I think they'd be pretty easy to target. You'll know roughly where the wires are, and they'll be very vulnerable due to their low thermal mass. You know how carbon nanotubes can be ignited by a camera flash? The intensities required to sever or weaken them won't be that high...far lower than those required to disable the torpedo itself. You could probably break the link with a laser that wouldn't even mar the paint on the torpedo. $\endgroup$ Jan 23 at 16:25
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As others have pointed out, fine wires would themselves be vulnerable to interference or damage, and could even be an attack vector themselves: even if shielded, they would be very vulnerable to a strong electromagnetic pulse, and ship and missiles connections to the wire would need to be hardened as if it was an antenna or other long electrical conductor connected to sensitive circuitry. As others mentioned, optical communication would be a very robust and effective approach, a tightly-filtered receiver on the missile tracking a narrow-band laser on your ship being very resistant to interference.

However, I think just the idea of having the torpedos be remote controlled is suspect, especially in a high-ECM environment. With that approach, the enemy ECM suite only has to focus on your ship: if they can disrupt your sensors, they can blind or misdirect every missile you have in flight. If the missiles instead independently track the target, the target's countermeasures have to deal with each missile separately.

Also, your ship is much further from the target than your missiles. Your ship will require extremely precise data on the position and velocity of both the target and its missiles, while a seeking missile can intercept the target with much cruder sensors working at much shorter range.

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Your wire guided 'torpedo' is actually going to have a rocket engine. This is going to complicate the design because you would want the trailing wire to, if possible avoid the hot exhaust plume (hot expelled gasses) leaving the engine. And in a vacuum the problem is that the exhaust plume will fan out in a more 'ball like' configuration at the rear of the rocket rather than the usual 'vertical' plumes you see when rockets launch from the ground (air pressure comes into play). And if you can't avoid it (and I'm not sure you could) your going to have to reinforce/insulate it so that means more mass/more complexity etc etc. How much additional mass/protection would be needed? I have no idea.

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