Modern blue water navies have the ability to project a sustainable threat in three dimensions; namely sub-surface, surface and airborne; at large distances across seas, far away from their home ports. This in turn implies integral capabilities of blue water navies to trounce threats from underwater, surface and air; to their constituent units, while carrying out their assigned tasks. In the author’s opinion, the concept of ‘limited area ocean dominance in three dimensions’ is likely to change to ‘limited area oceanic-space dominance’ in the next decade as the navies grapple with satellite-based surveillance and weapon systems of the enemy and acquire wherewithal to counter threats to their operations from space as well.

There are three major classes of weapons currently in the armoury of a naval ship to tackle threats from underwater, surface and the air, which include the naval gun in dual role, the heavy weight torpedo and the cruise missile.

The Naval Gun

The naval gun made its appearance sometime in the 16th century on board ‘Galleys’ which enabled them to fight enemy ships and also carry out attacks against shore-based fortresses. Advances in chemistry and metallurgy by the middle of the 19th century led not only to heavier and larger calibre naval guns but also to solid shots being replaced by explosive filled shells. The increase in the calibre of the naval gun however was somewhat countered by the advent of the quick firing gun, the ships started carrying both a light QF gun (~6 inches calibre) as well as a heavy medium calibre main gun (~12 inches calibre). In the 20th century, the improvements in the rate of fire of big guns made the navies to switch over to ‘all big-gun’ battleships. The rise in calibre of guns (to as much as 18.1 inches in case of Japanese Yamamoto!) was however halted post World War II with the arrival of the aircraft carrier and the surface-to-surface missile. With the emphasis shifting to the missile, the naval gun lost its place as the main armament of the battleship. Modern warships usually carry a three to five inch calibre gun capable of anti-surface, shore bombardment and anti-air missions and/or a rapid firing small calibre gun for anti-missile and anti-air defence.

Current developments in the naval gun are based on two approaches, first, the gun would only have a secondary role to play as compared to the missiles and the carrier based aircraft. It would be useful in shore bombardment and for use against smaller ships. Second, the naval gun would still have a general purpose potential as an anti-aircraft, anti-missile and anti-fast missile boat weapon. The former has led to the American 5″ Mark 45 and the British 4.5″Mk.8 (20-25 rpm at ~25 tonnes), and the later to the development of the widely used Italian Oto Melara 76.2mm (120 rpm, 7.5 tonnes in super rapid version) amongst others.

The 127mm Oto Melara, offered by the Italians; with a firing rate of 45 rpm and total weight of 22 tonnes and the ability to fire the ammunition of American 5″ Mark 45; is an attempt to combine both approaches. Further, the Vulcano rounds high-explosive fin-stabilised discarding sabot (HEFSDS) are a family of long-range rounds for the Oto Melara 127mm gun. These include, global positioning system/inertial measurement unit guided ammunition capable of engaging land-based surface targets at a range beyond 100 km and unguided 70 km range ammunition with an infrared seeker, terminally guided version, for the engagement of surface naval targets. The Russians have developed three fast firing automatic guns, AK-176M: L/59 calibre, 120 rpm, AK-100: L/59, 60 rpm, and AK-130: L/54, 84 rpm calibres. The favourite appears to be the 100mm A190 (E) variant which is claimed to offer three times the accuracy of AK-100 with 80 rpm, apart from the unguided shells; it is also available with rocket-assisted, and guided and long-range shells.

Trend

The naval gun has moved towards a general purpose role with the current developments leading to medium calibre, lighter weight, swifter rate of fire and more potent longer-range ammunition. As technology advances, the gun mount weight will get further reduced and the rate of fire enhanced. The general purpose naval gun will continue to be in use for anti-surface, anti-aircraft, anti-missile and naval gun fire support roles albeit with much smarter munitions. The above developments indicate that the naval gun is apparently not going to be discarded in favour of the missiles in near future, at least not until the missiles become cost beneficial as compared to the naval gun.

Torpedoes

The Spar Torpedo was perhaps the first torpedo designed to attack a target. It comprised of a long spar (~ 30 ft) with an explosive fitted at the end. This torpedo would be positioned underwater in the forward section of a warship and detonated when it came in contact with the target ship. The explosive would usually rip open the hull below the waterline. The USS Housatonic is understood to have been sunk by Confederate submarine H.L. Hunley using a spar torpedo. The word torpedo had been associated with various types of hidden explosive devices in the past like land mines, sea mines and booby traps, etc, till the self-propelled torpedo appeared on the scene and claimed the word exclusively. The self-propelling torpedo is perhaps the most feared of underwater weapons against ships and submarines, since its invention in the 1870s.The heavy weight torpedo (HWT) is the weapon of choice for the submarines not only against enemy ships but also against moving/static bottomed enemy submarines. HWTs are also carried by ships for attacking submarines.

The torpedoes are an embodiment of a synergetic mix of engineering disciplines ranging from mechanics, hydraulics, electronics, acoustics, explosive chemistry, etc to sophisticated software and computing. Their development has therefore involved differences in propulsion designs from steam engines to electrical motors to thermal engines and rocket motors. The control and guidance systems have also evolved from simplistic mechanical/hydraulic to sophisticated electronic and onboard computer based systems. The guidance has further diversified into self-guided and wire-guided varieties. The simple straight runners have given way to active passive homers and wake homers to counter moving targets. The warheads have moved from minol based to TNT/RDX/Al and now on to insensitive explosives with a life of over 40 years. The warheads over the years have been fitted with simple contact exploders to acoustic influence and magnetic influence proximity fuses. The diameter of the torpedoes has ranged from 324mm to 483mm to 650mm, and before settling for internationally acceptable 533mm. Interestingly, with the advent of microelectronics, space has never been a constraint for the torpedo and electronic/software updates always get comfortably accommodated in the torpedo.

A major technical feature that sets apart a torpedo from a missile is the fact that a practice torpedo is recoverable for reuse. This enables excellent weapon capability assessment, crew training as well as analysis of vital firing geometry, and it makes torpedo practice firings far more cost-effective and lucrative as compared to missiles.