Rockets Carried by Naval Aircraft –A Perspective
Published ET-Aviation & Defence Review Dec 2018
Rear Admiral Dr S Kulshrestha, retd
Naval Aviation entrenched itself in May 1912 when Commander Samson, flying a modified S 27, designated as S38 took off from HMS Hibernia which was underway and making a speed of 10.5 knots during the Royal Fleet Review in Weymouth Bay, England. The United States, Germany, Russia, Japan and France followed soon after that with their own Naval Air Wings.
In September 1914 the Japanese seaplane carrier Wakamiya carried out air raids against German land and sea targets during the Battle of Tsingtao. The first use of a Naval weapon, the torpedo, against the enemy was in August 2015 when a Turkish supply ship in the Sea of Marmara was sunk by Flight Commander Charles Edmonds flying a Short Type 184 aircraft. The capability of seaborne ‘air to land’ strikes was established in December 1914 during air raids on a German Zeppelin base at Cuxhaven. Naval Aviation has never looked back since and has entrenched itself as a formidable component of Sea Power.
The Short Type 184 flown by Flight Commander Charles Edmonds, was armed with 1 x .303 Lewis Machine Gun and 1 x Torpedo (14″ diameter)/520lb of other drop stores. The problem with carrying a mounted gun was that it was useful as long as the pilot could fire it from his line of sight without hitting the propeller. This led to the development of the Gun Synchronizer so that the gun could fire through the arc of the rotating propeller. The German Eindecker fighter was the first to be fitted with such a device followed by a better designed hydraulic device ‘Constantinesco gear’ for the British aircraft. The aircraft continued to be fitted with two forward firing synchronised rifle calibre machine guns, firing forward through the propeller. The roles for Naval Aircraft kept expanding, and so did the requirements for a bigger weapon package. The requirement to increase the number of weapons led to armament being mounted under the wings. Central gun mounts were discarded when propeller less jet propulsion rendered Gun synchronisers redundant.
The German submarines had caused extensive damage during the WWI which lead to the development of aircraft-mounted submarine detectors as well as bombs and depth charges to neutralise the submarines. The role of Naval Aviation after that included the Air-Anti Submarine warfare.
The Naval Aircraft depending upon their role, carry a wide array of weapons namely, air to air missiles, air to surface missiles, anti-ship cruise missiles, depth charges, bombs, rockets, laser-guided bombs, Naval aerial mines, and lightweight torpedoes. This article aims to provide a perspective into the rockets carried by fixed-wing Naval Aircraft.
The rockets are unguided projectiles with their propulsion system in which the propellant burns fiercely producing exhaust gases at high pressures. These gases are discharged through a calibrated nozzle to impart forward motion to the rocket body. The main components of any rocket used as a weapon comprise rocket motor, warhead and fuse.
Rocket motor: A rocket motor generally consists of a metallic motor tube, propellant grain, ignitor, stabilising rod, inhibitor, nozzle and fins. The warhead and nozzle & fins are attached to the motor tube at the forward and aft end respectively. The solid propellant grain has its integral fuel and oxidiser and does not require atmospheric oxygen to burn. Generally, it is a double base solid propellant. The double base propellant has two monopropellants, one being low energy and stabilising component and the other bringing the high energy content. This combination provides reasonably high energy for use as Aircraft rockets and reduces production of smoke. Nitrocellulose gel with dissolved nitro-glycerine with some additives constitutes such a propellant. The burning of the propellant is done by use of an igniter, which is a disc containing gunpowder composition and an electrical squib. The burning rate is controlled using the inhibitor coating of cellulose acetate variants, a salt coated stabilising rod inside the propellant prevents unstable burning. A constant rate of thrust is maintained by perforating the propellant core using different shapes; typically, a star shape is prevalent. The nozzle controls the characteristics of the exhaust gases to provide increased velocity. Fins help in providing accuracy to the rocket flight. In case the rocket fish tails the drag increases and the air stream hits the fins which in turn correct the motion of the rocket.
Warheads: There are many types of high explosive HE fillings for the warhead casings which are utilised for the aircraft rockets, depending upon the type of target against which they are likely to be launched. HE fragmentation warheads are used against lightly protected targets wherein the fragments cause significant damage. Anti-Tank and Anti-Personnel warheads are shaped charges which explode from base resulting in an explosive jet which penetrates the target. A general-purpose warhead is based upon the combination of the designs of the fragmentation and armour piercing warheads. It is used against a variety of targets utilising, a nose fuse or a solid nose plug and a base fuse variant. Warheads dispensing high velocity pointed metallic objects are classified as Flechette warheads. These are used with a base fuse against personnel and lightly protected vehicles. Incendiary warheads are used to ignite/set fire to targets. Flare dispensing warheads are used for various purposes like illuminating an area or deflecting missiles depending upon the constituent of the flare. Smoke warheads are used to mark a target by using smoke generating composition like plasticised white phosphorous. Dummy or practice warheads are weight balanced inert filled warheads for practice firings and loading/unloading training activities.
Fuses: These can be classified based upon their physical position or upon the way they operate. The warhead could be fitted with a nose fuse or a base fuse; further fuse could function depending upon impact, time, acceleration or deceleration, delayed action, proximity, and any combination of these. The fuse is a highly sensitive explosive component and therefore necessitates inbuilt safeties not only during transportation and handling but up to the time it is required to initiate the warhead. The built-in safeties include a time delay for separation from the aircraft as well as minimum acceleration and deceleration thresholds among others. Fundamentally all explosives in the fuse are aligned and initiate only after all the safeties are removed and impact conditions are met. Fuses which function on impact are either fitted in the nose or the base in the warhead. Mechanical Time fuses incorporate a timing device or a clock mechanism which introduces a pre-set delay after safeties are removed. Acceleration-deceleration fuses function in a fashion similar to the impact fuse, but they require that a minimum acceleration be achieved by the rocket for arming and a minimum deceleration for it to function. Proximity fuses sense the physical presence of target electronically. These are used for air/over the ground bursts. Fuses often have a combination of technologies depending upon the effect desired on the target.
Precision strike capability: Efforts are being continuously made by countries to develop and deploy highly accurate rocket systems to achieve precision hit capability. Precision hit would reduce the number of rounds to be fired per target as well as limit the collateral damage. The Advanced precision kill weapon system kit (APKWS) by BAE Systems utilises laser guidance and is in use in the US Armed forces. Guided Advanced Tactical Rocket (GATR) is a laser guidance kit by Elbit Systems for 68/70mm rockets to convert them into precision-guided weapons with high-precision strike capabilities. Low-Cost Guided Imaging Rocket LOGIR, by US Navy, guides the rocket to a pre-supplied position and uses imaging infrared in the terminal phase. The TALON by Raytheon is a digital semi-active laser guidance and control kit for rockets. Smart Tactical Advanced Rocket (STAR) also by Elbit Systems can be installed on 80mm rockets.
MIG 29 K – Rockets:MiG-29K is an aircraft carrier-based multirole fighter operated by the Indian Navy among others. It carries Rockets of the type S 5, S 8, S 24 in addition to a cannon, various missiles and bombs.
S-5: The S-5 is a 55 mm (2.2 in) calibre unguided, solid fuel rocket with a range of 3 to 4 kilometres. Each rocket is ~1.4 meters long and weighs ~5 kg, depending on the type of warhead and the fuse. Its fin assembly has eight attached fins which open as soon as the rocket leaves the launcher tube. The fins provide stability to the rocket by spinning at ~750 rpm. It is available with various types of warheads.
S 8: The S-8 is an enlarged version of the unguided S 5 rocket. It has six stabilising fins and achieves greater accuracy and firepower than the S 5. Its range varies from 2 to 4.5 km depending upon the type of warhead used. The S 8 has a diameter 82 mm body with 384 mm wingspan. Its length is 1.7 m with a weight of 13 kg. It has a variety of warhead types like thermobaric and runway penetrator in addition to the standard categories.
S 24: The S-24 rocket is ~2.33 metres long, and weighs ~235 kg. Its 123 kg warhead is of the blast-fragmentation type. The warhead spreads ~4000 fragments in a radius of 300-400 m. For deployment against hardened targets, it is equipped with a nose fuse. Its range is ~2–3 kilometres, and it is carried individually on weapon pylons.
Looking Ahead: The Rocket has retained its place in the weapon packages of the aircraft since its advent in WW II, this has been possible primarily because the rocket is more accurate than the bomb and cheaper than the missile. With the advances in microelectronics, computer programming and development of more lethal but safer explosives, it would not be out of place to forecast that in future the current rocket may undergo a complete overhaul. The future rocket would be a smaller, accurately guided, fire and forget weapon. It would be launched from a smart launcher from the aircraft and would be equipped with a smart fuse to enable maximum damage on the desired target.