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Transonic Submarines.


Pds314

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A transonic submarine is a submarine, most likely powered by nuclear fusion, which moves as fast as or faster than the speed of sound in water.

It does so by supercavitation, e.g., converting the water into a bubble of steam by shear force of impact, and sitting inside said bubble.

The first transonic supercavitating projectiles were tested in the 1990s by the United States military, Russia has had nuclear-tipped supercavitating torpedoes able to move at 100 m/s or so since the early 1970s.

The question is if there is any way to defeat a supercavitating submarine.

Lasers and radar don't work, since water generally obscures them.

Active sonar will only detect it if it is not going towards or away from you, and even if it does detect it, it will be sufficiently far away that if it turned randomly, you would be unlikely to kill it even with a hydrogen bomb.

Passive sonar would still have too long of a delay to detect it.

Waiting for it to run out of energy wouldn't work, as it can just draw in some hydrogen to use for fusion fuel.

Waiting for it to run out of air doesn't work, as it can likely just draw in oxygen from the water and eject the CO2.

Oh, and because it uses fusion as its energy source, it may well have the capacity to recycle any and all matter on board into anything made of the same elements, it is also possible that it could release a probe with a random number generator synced to one inside the ship doing the random maneuvers, the probe goes down to collect whatever matter is needed and then goes back to the ships new predicted location.

Saturating everything within 100 miles with 100-Megatonne bombs works, but is not likely affordable by any standards whatsoever.

Then of course comes the fact that these ships don't have to be very big, they may as well be equivalent to a single fighter aircraft, considering that speed, not armor or durability, are the only factors determining their survival.

The question is, is there anyway to kill one of these without totally bankrupting the person trying to do it, in other words, using materials that would be worth under $100,000,000 in the future when something like this exists, is there a practical way to kill one?

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Surveillance satellites. I imagine your supercav sub is going to be leaving one heck of a contrail through the ocean. You could also use a SOSUS-type array to track its position; you wouldn't have real-time data on its exact position, but you could pin it down close enough to lob a MIRV nuke into the water to kill it/collapse its supercavitation sheath, since at those speeds it isn't going to be doing any hard maneuvers.

Mind, the supercav sub is going to have problems of its own, primarily the fact that it's going to be flying pretty much blind down there: sonar isn't going to work through the cavitation sheath, not to mention it'd be outrunning its own sonar pulses and passive is right out, radar is out, etc.

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An SOSUS array will detect it passing and will get its current path, it would also be able to track it after its passes.

Ordinary sonar would also do this, however your would need multiple who are synchronized to get an direction. the shock-wave would be visible from air unless it goes very deep.

Now hitting it would be hard, an supercaviating torpedo might catch up but would also have serious problem tracking it while caviating.

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What qeveren said: supercavitating subs are far less useless than you'd imagine. The most simple countermeasure are probably good, old fashioned mines. The sub has next to no chance to detect them and even the tiniest interruption of the steam bubble will make the craft disintegrate...

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We wouldn't need sonar. A shock wave that big would easily be visible from the surface, and we could track the submarine using satellites or spy planes. I can't imagine that it would be anywhere near as agile as a normal submarine is, so its projected path would be fairly predictable.

With that in mind, couldn't we just get a warplane to fly ahead and drop a few depth charges? If the bombs will not go to the submarine, then let the submarine come to the bombs.

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I could be wrong about the supercav sub flying blind; apparently the later-generation Skhval supercav torpedoes are thought to have some form of terminal guidance, but I have no idea what the heck they would be using to pull it off. Anyone have an idea?

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  • 1 year later...

This is quite the necro post, but seeing as the issue wasn't solved and it's unlikely that a more recent thread exists, I'd like to put forth my idea of a solution for detection of such a vehicle by a hydrogen bomb-tipped missile.

Neutrinos.

They don't collide with water to a significant extent, they are emitted at a rate of a couple per fusion event, they move at nearly C, which, underwater, is 30% faster than light.

The main problem is that, even though the neutrino brightness of a bypass fusion submarine is likely high, detecting the neutrinos may take prohibitively long or require the detector to be huge.

An alternative possibility is to detect it by smell, and follow it with a faster and more maneuverable torpedo.

What I mean by this is that it will likely leave a trail. At short range, this could be hot, turbulent water with a velocity difference from its surroundings. At long range, it may be that the shock and boiling have changed the concentration of dissolved material in the water, the engine might, depending on how it works, induced the water to change to other isotopes via irradiation, or the sub may have it's skin ablated into the water. Any of these could possibly be detected in its trail, and followed up to where it is now.

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I could be wrong about the supercav sub flying blind; apparently the later-generation Skhval supercav torpedoes are thought to have some form of terminal guidance, but I have no idea what the heck they would be using to pull it off. Anyone have an idea?

The last I looked the guidance system was inertial guidance, other systems where being looked at. At the speeds the Skhval moves at compared to it's target generating a miss is, well, unlikely so you don't need anything to fancy, maybe a magnetic guidance/fuze?

Regards.

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Or, if you've gone for your 'size of a fighter plane' idea, just wait for the pilot to die horribly from the intense neutron radiation. Electronics would barely do better.

Water is a pretty effective radiation shield. Mostly useless in space due to its weight, but in a sub it could do a lot better.

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I'd say a transonic U boat or UUV would have a fairly complex method of maintaining a supercavitation bubble, and that system would likely be dependent on a constant density of the water it's moving through. Just like low pressure, high pressure, or shear winds can create turbulent forces on an airplane, the same forces would affect the underwater vehicle. The difference is that if an aircraft drops ten feet due to a wind shear, it's still in the air. If a transonic U-boat drops even a few inches, it would come into contact with the water, and disrupt its trajectory, possibly even stop it.

You could probably adapt a CIWS like those currently in use to shoot down anti-ship missiles with bullets made of compressed lead powder which would disperse upon impact with the water, and with a high enough rate of fire, CIWS could be made to target an area that the submarine is calculated to pass through, dumping hundreds of kilograms of lead powder into the path of the torpedo and increasing the density of the water, collapsing the bubble when the submarine passes through it, and hopefully crushing it, or slowing it down long enough to take it out using conventional weapons.

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