Ikara (missile)

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Ikara
Ikara missile on launcher
Type	Anti-submarine
Place of origin	Australia
Service history
In service	1960's-1990's
Used by	Australia, Brazil, Chile, New Zealand, United Kingdom.
Production history
Designed	Circa 1959-60
Manufacturer	Australian Government Aircraft Factories/Commonwealth Aircraft Corporation (CAC)/Australian Defence Scientific Services (ADSS)[4]
Produced	Early 1960's
Specifications
Weight	513 kg (1,129 lbs)
Length	3.429 m (135 inches)

Warhead	Mark 44 (two versions) Mark 46.
Detonation mechanism	none

Engine	Bristol Aerojet Murawa two-stage solid-fuel rocket engine.[5]
Wingspan	1.524 m (60 inches)
Operational range	10 nautical miles - Min (safety) range under 914 m (1,000 yards)
Flight ceiling	335 m (1,100 ft)
Speed	Boost max = 713 km/h (443 mph) Cruise = 658 km/h (409 mph) Maximum boost acceleration 10.9G. Boost burn time 1.96 seconds. Launcher maximum elevation 55°. Maximum range time interval 100 sec.
Guidance system	Command guidance
Steering system	Elevons
Launch platform	Ship-borne

The Ikara missile was an Australian ship-launched anti-submarine missile, named after an Australian Aboriginal word for a "throwing stick". It launched an acoustical homing torpedo to a range of 10 km, allowing fast-reaction attacks against submarines at ranges that would otherwise require the launching ship to close for attack, placing itself at risk. Also, by flying through the air to the general area of the target, the engagement time was dramatically reduced, giving the target less time to respond.

1 Tactical concept
2 Tactical rationale
3 Power unit
4 British variant differences
5 Ikara fitted ships
6 Operators
7 External references

[edit] Tactical concept

Ikara was a Rocket-Thrown-Weapon with similarities to the American RUR-5 (and later RUM-139) ASROC, and the French Malafon. It differed from ASROC in that the torpedo was recessed underneath the missile body rather than at the nose, and it was a cruise-type winged missile that 'flew' to its target, whereas ASROC was a 'point-and-shoot' ballistic rocket. Ikara's range at 10 nautical miles (19 km) was double that of ASROC.[6] Ikara was generally considered a superior system to ASROC as it was accurately guided during flight to ensure optimal targeting. A submarine would be aware from sonar contacts that it was about to be attacked and could engage in evasive changes of course. In ASROC's flight time to maximum range of 55 seconds,[7] a submarine travelling at 25 knots (46 km/h) would move 700 metres from its position at launch, and a prediction would be made of the submarine's likely position at torpedo splashdown. But at Ikara's design stage around 1960 the acoustic seeker range of the Mk.44 torpedo was limited to 457 metres (500 yards), although this was later improved,[8] and consequently its kill probability was low. See the illustration of miss distances possible.

ASROC worst case miss distance when attacking a submarine travelling at 25 knots (46 km/h) with the ASROC and Mk 44 torpedo combination. Attempting to splash the torpedo so that the submarine was within range of the torpedo acoustic seeker was entirely dependent upon a prediction of the submarine movements. An astute submarine captain would take immediate and unpredictable evasive measures when hearing the sonar echo. Only if the submarine maintained its approximate course and speed could the acoustic seeker be certain to lock-on the target, and even then a kill was not assured, especially if the missile's margin of error placed the torpedo astern of the submarine.

The Turana target drone was designed and built in Australia as a development of the Ikara anti-submarine weapon system. It was a target drone with remote control that was launched from the Ikara launcher for use in naval anti-aircraft target practice.

[edit] Tactical rationale

The tactical rationale or operational requirement for rocket-thrown-anti-submarine weapons deserves some explanation here, since without it the raison-d'être for these weapons can be obscure.

With the development of nuclear power, submarine performance, especially speed, improved dramatically, as did the threat they posed to large cities with their armaments enlarged to include strategic nuclear-armed missiles. Simultaneously, sonar detection capability at long range was also improving significantly. But the weapons available to surface escort warships was still of the short-range variety:

Mortars. The final British development was the Limbo ahead-throwing mortar, its range being a maximum of 914 m or ½ nautical mile, no more than twice the length of a modern U.S. aircraft carrier.
Torpedoes. Even the latest modern Mark 46 lightweight torpedoes are limited in range to 4 nautical miles (7.3 km), and at their speed of 28 knots (52 km/h) would take 8.5 minutes to travel that distance, and are consequently unable to attack time-urgent targets at extended ranges. A missile submarine, knowing itself to be threatened, could fire several missiles (at approx 30 second intervals) before a torpedo reached its target.

The four principal methods of delivering an acoustic homing torpedo or a Nuclear Depth Bomb at long range from a surface escort. Only the rocket-thrown weapons (ASROC and Ikara) are available for use in all-weather conditions and at instant readiness.

Longer ranges were achieved by air-delivered weapons, usually either an acoustic homing torpedo or a NDB, and there were several methods available, and all suffered from similar constraints:

Escort-based or aircraft carrier-based embarked helicopter, sometimes referred to as MATCH (Medium Airborne Torpedo Carrying Helicopter) or in the U.S. as LAMPS (Light airborne multi-purpose system). Referred to here as LAMPS.
Shore-based MPA (Long Range Maritime Patrol Aircraft) eg. U.S. P-3C Orion, U.K. Nimrod, or the Soviet Tu-95 Bear.
Carrier-based fixed wing dedicated anti-submarine aircraft, eg. S-3 Viking.

All of these suffer to varying degrees from being weather-dependent, not being available when needed because of maintenance, other taskings, low-fuel-state, or having expended their weapon load, and most crucially for the escort commander, a slow response time from first detection to weapon delivery, often as a result of these air assets not being under the direct control of the escort commander. An additional drawback is that the submarine target can detect the approach of helicopters and propeller-driven aircraft from the vibrations emitted, and take evasive action, or even seek to destroy the aircraft with a SAM launch. The U.K. Nimrod and U.S S-3 being jet-driven offer better stealth capability, but otherwise have all the other defects.

Ideally, what an escort commander required was:

An all-weather, all-conditions, urgent-attack weapon at instant readiness to fire.
Able to attack at extreme sonar ranges.
Short flight-time to the target.
Under the escort commander's direct control, not to have to seek the consent of other commanders on the battlefield.

Based aboard the commander's escort vessel, only a rocket-thrown weapon, or a short-range cruise missile such as Ikara could meet these requirements, and they led to the development of rocket-thrown anti-submarine weapons for both surface escorts and nuclear-powered hunter killer submarines by Australia (Ikara), the United States (ASROC and SUBROC), the Soviet Union (RPK-2 Viyuga) and France (Malafon).[9] [10]

[edit] Power unit

Ikara was powered by a two-stage in-line solid-fuel Murawa rocket engine developed by Bristol Aerojet Ltd in the UK [11] and was guided by radio command link until it reached the vicinity of the submarine, determined by the ship's sonar contact, where it would first jettison the rear ventral fin and torpedo rear covering and then release its Mark 44 or Mark 46 acoustically-guided anti-submarine torpedo. The torpedo payload would descend by parachute while the missile itself was programmed to splashdown some distance away to avoid interference with the acoustic torpedo's seeker head. The torpedo would then begin either a circular- or snake-search pattern to find and lock-on a submarine contact.

Cutaway drawing of the Ikara missile largely based on declassified documents located in the National Archives, [1] London, and photographs taken by the artist of museum exhibits at the Bristol Aero Collection[2] at RAF Kemble and the Royal Navy Submarine Museum, Gosport, Hampshire, UK.[3]

[edit] British variant differences

Test missile on display at Bristol Aero Collection, Kemble, England.

A variant fitted to the British Royal Navy's Leander class frigate differed in several respects from the original Australian version designed to operate in the Pacific. The Royal Navy required changes to the frequencies used, to enable Ikara to be used in the NATO area, where different electronic warfare conditions and international frequency agreements had to be taken into account. The Australian-built analogue computer system was incompatible with the ADA digital battle-control computers being fitted into Royal Navy ships, and this was also changed. The UK-manufactured version of the Mark 44 torpedo also differed from the US-built version purchased by the Australians for their Ikara missiles. The British also required the missile payload to be changeable aboard ship to permit different payload combinations to be used, including a Nuclear Depth Bomb (NDB) option, and this, together with the different ship internal layouts required further changes to the missile, storage and handling arrangements. The Australian practice was to combine the missile and payload at a shore-based ordnance facility, before issuing the complete unit to a ship. Repair or maintenance was only possible ashore, whereas in the British ships, the changes made enabled a faulty torpedo to be removed and replaced on a functioning missile, and thereby increasing the flexibility of use of very limited stocks aboard. Especially on lengthy deployments around the globe, as was more common with British ships than their Australian counterparts. The facility to change a torpedo payload aboard ship also permitted a change from a conventional torpedo to a WE.177A NDB, a facility for a nuclear option that was not needed on ships fitted with the Australian variant of Ikara.[12]

[edit] Ikara fitted ships

Ikara was fitted to all of the Royal Australian Navy's River class frigates / destroyer escorts and Perth class guided missile destroyers. It was also operated by the Brazilian Navy, Chilean Navy, Royal Navy, and Royal New Zealand Navy. It was phased out in the early 1990s. The British purchased Ikara to fit to the two new CVA-01 aircraft carriers planned (and later cancelled) in the 1960s, and their escorts, the Type 82 destroyers, of which only one, HMS Bristol was built. With the cancellation of the remaining escorts, the British were left with purchased Ikara missiles in storage, and opted to fit them into eight existing Batch 1 Leander class frigates in need of modernisation.[13] These escorts were HMS Ajax, HMS Arethusa, HMS Aurora, HMS Dido, HMS Euryalus, HMS Galatea, HMS Leander and HMS Naiad. The Leander class had low emitted-noise levels compared to their more modern, gas-turbine-powered successors, and were a good choice to install Ikara since the low noise level assisted the Type 2030 sonar fitted circa 1970 to frequently achieve impressive submarine detection ranges of more than 100 nautical miles (190 km) in good conditions, adding to the usefulness of the long-ranged Ikara missile.