The hesitancy to embark on revolutionary, or markedly different, submarine designs is readily understandable. Economy of effort, satisfaction (more or less) with the way things are going and avoidance of risk, militate against dramatic changes. But the fact is that, on the other side of the coin, we must expect changes in anti-submarine warfare whether we like it or not; and, although there is nothing yet to imply that the oceans are becoming transparent as some people would have us believe, it would be unwise to reckon on the tactical balance between current submarines — big SSNs specifically — and ASW units (including ASW submarines) remaining as it is today.
It might be said that the major navies have drifted into a Cadillac philosophy; and some lesser navies are bent on following if they can. More rationally, a nation like India may feel that the acquisition of nuclear submarines will make it prohibitively expensive for a major power to interfere in what India deems to be its private lake. Canada seems to want a fleet of SSNs for both reasons.
Big submarines have been necessitated by powerful nuclear plants and a multiplicity of weapon systems. Designers have been unable to meet wide-ranging operational requirements with smaller boats. Generally speaking, besides being able to carry a heavier and more varied weapon load, a bigger submarine can go faster and further than a little one.
With submarines becoming quieter on all sides, and with non-acoustic signatures probably becoming more important, it seems that active detection will tend more and more to replace passive methods and make small submarines more attractive. Finding enemy submarines in broad areas of the oceans is becoming inefficient using passive means and bringing enemy submarines to battle is increasingly more difficult.
A disinterested observer would say experience shows that the best place to strike at an enemy is at his base or as close to it as possible. He would propose that there are two reasonable places to annihilate killer bees. They can either be swatted while they buzz around a honeypot or they can be destroyed in their nest. The first method is apt to be expensive both in honey and effort: in terms of cost-effectiveness it is better to kill them in their nest. He adds, by the way, that anyone who tries to hit killer bees between their nest and the honeypot will soon discover that the attrition rate is low and the hunter is exposed to painful surprise flank attacks from his quarry.
In submarine ASW, as in bee-hunting, there are two reasonable places to seek and kill the enemy; and neither are on his underwater transit routes where there are doubts about the success rate measured against own losses. The first is in a focal zone to which the enemy is attracted (around a convoy, fleet or in a missile-launching area); the other, is near to his base –even inside it if practicable — before he is properly underway. There is reason to think that maritime strategy does not envisage forward submarine operations that are quite so far forward as the latter option — at least not against the USSR. It is, presumably, unthinkable that SSNs would venture into the Kola complex although they might very well lurk off potential enemy ports elsewhere in the world. Moreover, the potential of SSNs is largely wasted in shallow or confined waters; and we certainly can not imagine them penetrating ports or anchorages anywhere. Nor, are even the smallest current NATO SSKs suitable for buccaneering in the style of World War II midgets such as X-craft.
So it looks as though very desirable under-water onslaughts at, or close to, enemy bases — other than with long-range missiles whose effectiveness is problematical against enemy submarines in the process of deployment — are not a practical proposition with large submarines.
However, the picture changes radically if we take into account a revolutionary small design submarine which, virtually unnoticed, has been under development by the Italian company Maritalia since the early 1970s, — and deserves urgent consideration. Unfortunately, the only expert team from outside Italy to display serious interest was sent — not long ago by the Pentagon. Reactions elsewhere indicate that nobody wants to rock either the nuclear boat or the new hybrids which are coming along in Germany and Sweden.
Signor G. G. Santi, the inventor of a totally new integrated submarine system reasoned that a primary problem with submarine construction was finding space for a propulsion plant which would give both high speed and long endurance while still affording plenty of room for weapon systems. Generally speaking, with traditional power either diesel-electric or nuclear — it is the propulsion system (which would include batteries, or a reactor, and its shielding) which has initially dictated the size of a hull.
Alternatively stored chemical energy of the right kind is perfectly capable of supplying an anaerobic closed-circuit engine for practically any desired performance — just so long as there is sufficient storage space. Santi, an advocate of midget submarines and intent on reducing size while achieving high performance, asked himself how sufficient energy could be stored without taking up an undue amount of space and thereby requiring a large hull. The elegant answer was to use the hull itself.
If the hull were constructed of circular pipes welded together to look rather like a Michelin Man on his side, each torus could be used for energy storage — gaseous oxygen at 350 bar was chosen — while diesel fuel could be carried in tanks either internally or externally. The engine itself would be a compact closed-cycle diesel; and its exhaust was also to be stored rather than ejected to sea, thus avoiding difficulties resulting from back pressure at depth while not leaving a detectable wake.
The net result was a wakeless and truly air-independent submarine of modest size — a midget with no need of a snorkel or a large battery and an exceptionally large usable internal volume in proportion to its envelope displacement. In fact, his first fully operational midget, completed in mid-1988, has eighty percent internal space free (for whatever) which compares with twenty-five percent available in a comparable plated hull with traditional propulsion.
By 1988 a closed-circuit gaseous oxygen/ diesel propulsion plant had run for some 25,000 hours underwater without problems; and, being to all intents and purposes an ordinary diesel engine, it proved easy to maintain with minimal training for the engineers. No shore infra-structure was required other than an oxygen-producing plant and a compressor.
Meanwhile, a trial toroidal hull was subjected to pressure testing in a tank. A normal hull of steel of the same weight would have been expected to show weakness at the equivalent of 206 metres depth. The toroids however held up until, eventually, one section caved in at the equivalent of 1186 metres which is about what the Soviet ALFA is able to withstand with an immensely expensive titanium hull.
The diameter of the toroids, and the thickness of their metal (ordinary steel) would be dependent, naturally, on the energy storage required, the size of the submarine being built and its required diving depth. It seems that relationships follow a constant formula; and it is considerably easier to build an ideal tear-drop or ALBACORE shape — by reducing toroidal ciroumferences successively from the center — than it is to bend thick sheet metal in two planes.
The generic title given by Maritalia to submarines built on these lines is gst, standing for gaseous storage toroidal; and gst boats can come in all sizes to suit. All would be completely independent of the atmosphere.
The initial midget examined was a ‘3gst9’ meaning that the toroid pipes are of three-inch diameter and the overall length is in the 9 metre bracket. A scaled up larger mini-sub was built at 100 tons standard displacement and 27 metres long. The latter craft are naturally, more capable of distant offensive inshore operations than the smaller which are primarily intended for harbour-penetration, mine-planting or as challengers to enemy mini-subs, swimmers and swimmer delivery vehicles.
There is a wide variety of weapon systems for the 27 metre boat: options include ground mines, mine-delivery vehicles, torpedoes (heavyweight or lightweight) together with active/passive sonar and fire-control, and Commando vehicles. Attacks on enemy ports and anchorages are entirely feasible with any of these variants. The range of the 27-metre midget, fully submerged throughout and carrying two heavyweight torpedoes, is 2,000 n. miles at a transit speed of eight knots: burst speed is 25 knots and sustained top speed is 16 knots.The entire Mediterranean and Adriatic are within reach from an Italian base.Obviously the Kola, if that ever becomes the target, is not attainable without a forward base — but the base could be a ship or ‘mother’ submarine. The cost, incidentally of a 27 metre midget is estimated at around $33 million plus $3.6 million for Plessey Hydra sonar.
However, the prospect of middling-sized submarines, each armed with six bow tubes and a dozen or more reload weapons, may excite more interest, in some quarters, than mini-subs. The following performance can be confidently predicted for a 2,800 tonne gst boat:
These figures,impressive though they be,do not equate with SSN high-speed endurance. Eye-brows will undoubtedly be raised at Maritalia’s claims; but there is no reason to doubt them if midget performance, so far, is extrapolated.
Thus, from the evidence available, the size problem has been solved.
Gst radiated noise levels have not been published but they are expected to be low. The toroids muffle radiated noise in the same way as a double hull; there is no noisy exhaust system (because exhaust gases are stored); airborne noise is certainly very low and one-inch thick sound-absorbent quilting lines the inside of a hull around the engine space.
The gst diesel-generators provide ample power for all conceivable purposes including high performance sonar; and a modest battery is available for ultra-quiet period~. Noise arising from vortices is largely eliminated forward by substituting an Archimedian ram, nested amongst the torpedo tubes, for forward hydroplanes in a 2800 tonne design. This instantly changes dis-placement at the bows to achieve pitch or maintain a level trim: it is, in effect, a static hydroplane.
Active sonar detectability is reduced by a 48 mm anechoic coating applied in two layers of strakes like a clinker-built boat: it would appear that strakes are much less likely to drop off than tiles.
In short, what is offered is a series of exceptionally fast, powerful and hard-to-detect little submarines which might be termed Minitruders.
Some disturbing questions spring to mind. What if Third World navies, hitherto content with fairly pedestrian submarines, acquire an affordable minitruder capability? What if Iran had effective midgets instead of the reputedly unsatisfactory craft she has herself assembled? What of maritime strategy for the major powers if get submarines proliferate?
What indeedl It would surely be advisable for the leading navies to investigate get potentialities very carefully indeed for themselves — and, if possible, prevent Maritalia’s designs getting into the wrong hands.