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Torpedoes are the primary weapons of most submarines and anti-submarine warfare platforms. Torpedoes are self-propelled guided projectiles that operate underwater and are designed to detonate on contact or in proximity to a target. With advancements in technology, a modern torpedo can destroy a target at a range of 40 km and a speed of about 50 kts. For the Navies, the modern torpedo enables submarines to defeat surface and undersea threats and gives surface ships and aircraft the means to reach beneath the surface and attack submarines.
Torpedoes are the primary weapons of most submarines and anti-submarine warfare platforms. During World War II, submarine and aircraft-dropped torpedoes sank hundreds of merchant ships and warships. Unlike the numerous aerial bombs or cannon shells required to sink large warships, just one or two torpedo hits could and sometimes did suffice to sink huge aircraft carriers and battleships.
They are typically classified as being either lightweight (air-dropped or rocket-delivered) or heavyweight (submarine or ship-launched); with lightweight torpedoes carrying smaller warheads and having reduced range and endurance. Torpedoes primarily vary in their guidance mode: wire-guided, and autonomous fire-and-forget types; and performance characteristics such as maximum depth, maximum speed, and sensor performance. They can also be launched from a variety of platforms like ships, submarines, rotary wing and fixed-wing aircraft.
Lightweight torpedoes are typically ASW-only weapons with no ability to engage surface targets. Torpedoes primarily vary in their guidance mode and performance characteristics such as maximum depth, maximum speed, and sensor performance. Torpedoes can be countered with acoustic countermeasures, decoys, and even anti-torpedo torpedoes.
Torpedoes are the most preferred lethal underwater weapons for naval platforms such as submarines, surface vessels, aircraft and helicopters. But limited range has long been the torpedo’s major drawback. Unlike a missile which travels through the thin atmosphere, a torpedo must fight harder to reach its target. The medium of seawater offers resistance to its movement at high speeds. In addition, it limits the propagation of electromagnetic waves and underwater communication and detection.
Countries are in race to develop long range lethal torpedoes with unlimited range. The range of the Lightweight torpedoes is further enhanced when delivered by aircraft or rocket, and typically have a warhead in the 40kg range. A lightweight torpedo is designed to be dropped very close to the target, and therefore has no wire guidance and frequently begins a programmed search pattern on entering the water.
The range of torpedoes can be further enhanced by employing them as the payload of missiles. Anti-Ship missiles typically use a jet or rocket engine, to deliver: an explosive warhead such as a depth charge, or; a homing torpedo. They are carried from a launch ship, or another platform, to the vicinity of a target such as a submarine.
Anti-submarine missiles, as well as rockets, with torpedoes as warheads, are not new. For instance, the U.S. Navy fields the RUM-139 Vertical Launch Anti-Submarine Rocket (VL-ARSOC), which is fired from standard Mk 41 Vertical Launch System cells and carries a Mk 54 lightweight torpedo. Another example is the Russian RPK-6, a Soviet-era design that NATO also calls the SS-N-16 Stallion. There are also already at least one supersonic design, Japan’s Type 07 vertically-launched anti-submarine rocket, in service.
MK 54 Lightweight Torpedo
The MK 54 built by Raytheon is the most used light weight torpedo platform in the word and utilises the proven technologies of MK 50 and MK 48 ADCAP torpedoes. The torpedo can be fired from over 20 launch platforms and can be effectively launched from surface vessels, helicopters and fixed wing aircraft against any current submarine navigating at its full operating depth.
The torpedo weighs 276kg and can be integrated with a 44kg high-explosive warhead and with the AN/AQS-22 Airborne Low Frequency Sonar. The propulsion system powered by liquid propellant provides the torpedo a maximum speed of 40kt. The MK 54 Lightweight Torpedo, an antisubmarine warfare weapon, is used by U.S. surface ships, fixed-wing aircraft, and helicopters.
Aerojet Rocketdyne has been awarded a $63.2 million Other Transaction Authority by the U.S. Navy to develop an advanced propulsion system for the MK 54 MOD 2 Advanced Lightweight Torpedo (ALWT). “We have developed mission critical propulsion and power systems for the U.S. Navy for more than 60 years,” said Eileen Drake, Aerojet Rocketdyne CEO and president. “Aerojet Rocketdyne is a world-class developer of high performance propulsion systems and we look forward to applying our expertise to support the development of the Advanced Lightweight Torpedo.”
For the Authority, Aerojet Rocketdyne will develop a prototype Stored Chemical Energy Propulsion System (SCEPS) power plant and afterbody/tailcone which would ultimately be integrated into the ALWT. The SCEPS improves the capabilities of the MK 54 torpedo.
A244/S Mod 3 Lightweight Torpedo
The A244/S Mod 3 lightweight torpedo from EuroTorp is the latest member in the A244/S family of fire-and-forget ASW torpedoes used by more than 16 Navies. It has been designed to counter any conventional and nuclear submarines with advanced anti-torpedo countermeasures.
The torpedo weighs 254kg and incorporates sophisticated acoustic seeker, advanced counter-counter measures capability and a blast type warhead. The maximum operating depth of the A244/S Mod 3 is over 600m. The A244/S Mod 3 is powered by a DC motor driving two counter-rotating propellers, ensuring a top speed of 36kt and a maximum range of 13.5km at low speed.
Eurpean MU90
Resulting from a Franco-Italian cooperation, the MU90 is the only totally new lightweight torpedo in the world. It is claimed , to be capable of countering any type of submarine, even if acoustically coated, deep diving, fast evasive, deploying anti-torpedo eff ectors or grounded in coastal areas. Its impressive embedded acoustic and dynamic capabilities also allow the weapon to be used in anti-surface missions and, with few adaptations, in anti-torpedo roles.
The MU90 can be operated without any performance degradation from any type of platform such as surface vessel, fixed and rotary wing aircraft and missiles. It features a unique and comprehensive range of presets – including specific confined water search modes – which
optimise target search and attack. Whatever the surface or air platform, DCNS offers a full range of launching systems, from stand alone to fully integrated solutions. All operational modes and training functions are included whatever the solution retained
Sea proven with more than 250 trials, including warshot fi rings, and over 1,000 units produced, the MU90 guarantees full operational maturity and reliability. It is the deterrent weapon to protect your maritime approaches and your naval forces deployments.
Propulsion
The weapon is powered through a silver oxide-aluminium (AgO-Al) sea-water battery using dissolved sodium dioxide powder as electrolyte and incorporating an advanced closed-loop electrolyte re-circulation system. The battery offers depth-independent power and constant
Warhead Ignited via an impact type exploder, the direct energy shaped charge warhead is composed of 32 kg of highly compressed V350 explosive. It is proven to penetrate any type of double hull submarines and to grant depthindependent target destruction capability.
Acoustic seeker
The advanced acoustic seeker features digital multi-preformed transmission and reception beams. Its multi-frequency, parallel processing and simultaneous acoustic modes operation allow multitarget tracking, classification and analysis:
■ operational bands > 4,
■ operational bandwidth > 10 kHz,
■ acoustics coverage 120°H x 70°V,
■ active detection range > 2,500 m,
■ echo sounding navigation,
■ simultaneous targets: up to 10.
Safety
The MU90 is the only totally safe LWT:
■ the AgO-Al battery electrolyte only starts when the torpedo has entered into the sea water,
■ the warhead is an insensitive munition compliant with STANAG 4170 and 4439 requirements. energy performances. The torpedo is
propelled by an electronically controlled high-RPM brushless motor driving a cavitation free pump-jet. It allows a continuously variable torpedo speed automatically selected by the tactical operation system and a very low engine noise
DRDO successfully flight tests supersonic missile assisted release of torpedo
India says that it has successfully tested a new supersonic anti-submarine missile. This missile carries a lightweight torpedo as its warhead and releases it over the designated target area, after which that weapon operates as normal and uses its own guidance system to seek out the enemy submarine. These rocket-assisted torpedoes is that they can cover around 350 nautical miles in a supersonic speed. When launched from a warship or a truck-based coastal battery, SMART takes off like a regular supersonic missile. Just when it approaches close enough to the submerged submarine, the missile will eject the torpedo system into the water and the autonomous torpedo will start moving towards its target to take out the submarine. This would mean a quantum leap for the Navy’s anti-submarine warfare capabilities, given the very-long range and supersonic speed.
Dubbed the Supersonic Missile Assisted Release of Torpedo, or SMART, this could give Indian warships, and potentially shore-based units, a valuable additional stand-off tool in the face of growing submarine threats from adversaries, especially China. China is continuing its relentless development of both nuclear-powered and conventional submarines. A report on China’s naval modernisation by the US Navy’s Office of Naval Intelligence noted that by 2030, China could have as many as 76 submarines. Further the Beijing is moving ahead to develop bases in Indian ocean region including Pakistan and Cambodia.
India successfully flight tested the Supersonic Missile Assisted Release of Torpedo (SMART) from Wheeler Island off the coast of Odisha in Oct 2020. All mission objectives, including missile flight upto the range and altitude, separation of the nose cone, the release of Torpedo and deployment of Velocity Reduction Mechanism (VRM), were met perfectly in the flight test. Defence Minister Rajnath Singh congratulated the Defence Research and Development Organisation (DRDO) for the success.
“The DRDO has successfully flight tested the Supersonic Missile assisted release of Torpedo, SMART. This will be a major technology breakthrough for stand-off capability in anti-submarine warfare. I congratulate DRDO and other stakeholders for this significant achievement,” Singh’s tweet read. SMART is a missile assisted release of lightweight Anti-Submarine Torpedo System for anti-submarine warfare (ASW) operations for far beyond torpedo range. This launch and demonstration are significant in establishing ASW capabilities.
Development of SMART began in 2016 and the goal is reportedly for the missile to have a maximum range of 650 kilometers, or just under 404 miles. The missile’s warhead is Torpedo Advanced Light (TAL), also known as the Shyena. TAL, which is an acoustic homing torpedo, reportedly has an endurance of approximately six minutes, which translates to an operational range of around 10 miles at a maximum speed of 33 knots, giving it some additional time in which to find its target after hitting the water.
Speaking about it, Chairman DRDO, Dr G Satheesh Reddy, said, “SMART is a game-changer technology demonstration in the ASW.” The events of today were monitored by the tracking stations (Radars, Electro Optical Systems) along the coast and the telemetry stations including down range ships. A number of DRDO laboratories, including DRDL, RCI Hyderabad, ADRDE Agra, NSTL Visakhapatnam, have developed the technologies required for SMART.
China is developing a supersonic anti-ship missile torpedo
In Sep 2022 it was reported that China is developing a supersonic anti-ship missile that will be able to travel further and faster than any traditional torpedo. The 5 metre (16.4 feet) missile will be able to cruise at 2.5 times the speed of sound at about 10,000 metres (32,800 feet) – the same altitude as a commercial airliner – for 200km (124 miles) before diving and skimming across the waves for up to 20km.
Once it is within about 10km of its target, the missile will go into torpedo mode, travelling underwater at up to 100 metres per second (200 knots) using supercavitation – the formation of a giant air bubble around it which significantly reduces drag, according to the researchers.
It will also be able to change course at will or crash-dive to a depth of up to 100 metres to evade underwater defence systems without losing momentum.
One of the biggest challenges for the developers is the power system, because of the need to produce considerable thrust while breathing in either air or water. But Li’s team said the problem could be solved by using boron – a light element that reacts violently when exposed to both, releasing a huge amount of heat. The team, from the college of aerospace science and engineering in the National University of Defence Technology in Changsha, Hunan province, unveiled a blueprint for the missile’s power system in the September 8 issue of the peer-reviewed Journal of Solid Rocket Technology, published by the Chinese Society of Astronautics.
A Nasa study funded by the US Navy last year found that nanotubes made using boron nitride, a combination of boron and nitrogen, could potentially be used to power hypersonic weapons travelling at speeds above 6,400km/h (4,000 miles per hour).
But most boron-powered engines are designed to work only in the air. Researchers usually choose aluminium or magnesium as fuel to drive supercavitating torpedoes as they react more easily with water. Li’s team said they had designed a boron-powered ramjet engine that could work both in the air and underwater.
There are some unique components, such as adjustable inlets and exhaust nozzles to maintain the boron’s burn efficiency in different environments, but the biggest change is in the fuel rods, according to their paper.
Boron usually accounts for about 30 per cent of the total fuel weight in an air-breathing missile because of the many other chemicals required to control and prolong the strong combustion.
Li’s team has doubled the share of boron in the fuel and estimates the result could produce a thrust greater than that of aluminium in water.
“The cross-media ramjet uses a fuel-rich solid propellant, which burns with the external air or seawater entering into the ram to generate high-temperature gas and generates thrust through the nozzle,” the paper said.“It has the high specific impulse and simple structure as an ideal power source for a cross-media anti-ship missile.”
Lead scientist Li Pengfei and his team said no existing ship defence system was designed to handle such a fast “cross-media” attack. “This can greatly improve the missile’s penetration capability,” they said.
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