Naval mines aren't 'sexy'. Even mine countermeasure ships aren't sexy. Especially not so while sitting on a reef, of course.
Mine countermeasures (MCM) get very little love. Even in Germany, one of the leading proponents of MCM during the Cold War.
I've scraped together many bits of info on naval mines, from mid-19th century to basically 1990's technology. One of the striking findings was in my opinion the turn of events for minesweeping: Minesweeping became much less useful with the introduction of 'smart' acoustic mines. A magnetic or hydrostatic/seismic sensor wakes up the dormant mine, while the acoustic sensor listens to the ships' noises, analyses them with algorithms, compares them to a library of ship sounds and identifies the target. Together with electrostatic sensor and stuff this allows the identification not only of ship class, but also of the ship's name (not necessarily in face of countermeasures, though). That is, if proper intelligence preparation is available and it's not some much less savvy export mine.
Minesweepers were originally meant to cut cables of tethered mines, they may also on some sea bottoms try to catch a mine similar to how fishermen catch some bottom-dwelling seafood. Neither works with a bottom mine on uneven bottoms or against a mine burrowed in a soft sea bottom. Other sweeping techniques involve faking of signatures, such as magnetic and electric fields and noises (in order to entice it to blow up harmlessly). You may also use a minebreaker on canals and rivers in order to trigger hydrostatic fuses (a ship which triggers the mine itself, but is either built to survive or is expendable).
The problem is that the minesweeper doesn't necessarily know which ships would trigger the mines. Minesweeping has thus difficulties to fake signatures that match the ones the trigger will respond to.
On top of that, it's an old technique to build counters into mines; they don't necessarily explode on first contact, but sometimes after 5, 10 maybe 17 or so. The minesweeper captain won't know how often he will need to sweep. He may have a perfect library of the signatures of all ships of a convoy planned to leave a harbour, and still couldn't complete the sweeping in front of the harbour with good confidence in a reasonable time. Published modern MCM against acoustic mines does (as far as I can tell) don't offer confidence that smart acoustic fuses can be defeated by sweeping. Some navies don't even add the ability to emulate specific acoustic signatures to their MCM; they instead just make general noise that affects primitive acoustic fuses only.
That's part of why minehunting (actively seeking mines, mostly with sonar) has become so important.
We don't need a minehunter ship to handle geographic bottlenecks or the vicinity of a harbour, though. This could be done with a radar and drone boats with control being exercised from containers on the shore. Don't tell this to navies, though. A mine countermeasures ship isn't sexy, but at least it's a ship, and naval bureaucracies love having as many ships as possible. Officer jobs and so on.
|Naval mine goes boom (shock test of a warship)|
Well, this was an excerpt about the troubles of those facing the (offensive) naval mining. Now on to the offensive part itself, in order to show why I believe naval mining campaigns could be much, much more mean than is widely appreciated. For a historical analogue, look up Operation Starvation (also here).
First, I'll admit that I'm mostly writing about incredibly gold-plated concept here, and that insiders no doubt can make up an even more mean design.
The mine shall be deployed by air or other means, but if dropped by air it might be a glider with a combined GPS and INS navigation so it will actually impact on water very close to a pre-planned location.
Once there, it may be a bottom mine if the bottom is difficult enough for spotting mines with active sonars (such as close to reefs and so on). It may also be a self-propelled mine. Those mines look quite like a torpedo and can travel quite some distance. Their observation by radar during the glide phase would thus not give away their actual location. The release from the aircraft could be farther away, adding glide distance and self-deployment range for stand-off range. The self-propelled mine could accelerate and bury itself in the soft bottom well enough to be fully covered by mud. Additionally, it could have a mildly sound absorbing outer layer so bottom-penetrating sonar would have a tougher job. A minimised magnetic signature of naval mines themselves in general is an obvious design choice.
These mines could then wait and wait with practically no energy consumption at all. Once triggered by a magnetic or electric field, they could switch on their confirmation sensors; mostly acoustic and possibly hydrostatic. The computer compares the readings with his library and decides to either fall asleep again or to fuse (probably with some delay in case of the bottom mine). The bottom mine may be too deep for good effect, though. Thus it might rise quickly (for example by by filling a balloon with gas) and once at a promising depth it would blow up.
The more torpedo-like self-deployed mine would behave differently; it would go into reverse, un-bury itself, then move to confirm the contact in its proximity. Electric field readings, wake pattern, comparison of acoustic (revolution speed of screws yielding a speed estimate) with hydrostatic readings (a certain speed of a certain ship should yield a certain water pressure wave) and so on. It could use the wake riding technique or an imaging active sonar to discern a decoy from the real thing.
Its computer might also decide to not engage the target and the torpedo-like mine would run deep into the soil again.
I have a strong suspicion based on unclassified info that today's mine countermeasures are not even remotely meant to counter such a high end super-mean naval mine design. Instead, much attention is still being paid even to tethered mines.
An alternative to gold plating is of course always quantity; such as with the Quick Strike naval mine concept. There aren't enough minehunters to cope with thousands of mines quickly. Quantity is especially easy in defensive minelaying, for this makes deployment easy.
Today , the United States lacks modern mines and there is only a handful of trained mine specialists. The U.S. stockpile is significantly smaller than North Korea’s estimated 50,000 mines, while the Chinese Navy might have on the order of 100,000 and Russia has been estimated to have 250,000.
So why don't navies seem to pay much attention to MCM, especially shore-based MCM? My suspicion is just the same as for the almost non-existing preparation of decoy sets for deployment on civilian shipping and so on: It's (a) not sexy enough and (b) naval bureaucracies have an overpowering urge to have both impressive and many ships.
A German admiral once publicly complained that during the few years he headed the German navy he wasn't able to christen a single new warship. This was a perfect summary of a naval bureaucracy's interests, while a taxpayer might have expressed his satisfaction that peace was maintained without spending more on warships.
Sophisticated military forces are always first and foremost bureaucracies, and tend to behave like one. It's their civilian master's job to make sure navies pursue national interest, not bureaucratic self-interest. I consider several naval developments - amongst them the low priority given to MCM - as indications that the civilian masters fail in their job (probably due to incompetence).
Then again, I may be full of it instead. This is about the naval domain, which is very much technology-driven and thus full of fog obscuring my insight into it.