New Delhi, 27 March 2016
Goa will have its own proud moments during the prestigious Defexpo being held at Quitol, Goa apart from hosting the mega event first time outside Delhi. A huge bow mounted Sonar Dome designed & developed by Research & Development Establishment (Engineers) [R&DE(E)], a DRDO laboratory based in Pune is going to be flagged off by Defence Minister Manohar Parrikar, Secretary Department of Defence (R&D) & DG DRDO Dr. S. Christopher will also be present on this important occasion. The ceremony will be held at Defexpo site in Goa on March 29, 2016. The Sonar dome will be delivered to Mazgaon Docks, Mumbai.
The Sonar Dome, a first of its kind in the country has been manufactured by a composites manufacturing company in India. This is a huge contribution by Indian Industry to the ‘Make in India’ movement. Only a couple of companies worldwide have the capability of realising such structures.
All anti-submarine warfare (ASW) ships have a sonar array fitted to the ship structure below the waterline. The sonar functions as the ship’s underwater eyes and ears. The sonar dome is a structure fitted over the sonar array so that its electronics and sensors are not exposed to surrounding hostile environment. The sonar dome has to be structurally sound as well as acoustically transparent.
R&DE(E), DRDO, Pune has successfully developed process technologies to realise large composite structures that can be used in Naval ships & submarines. The Laboratory has also developed technologies related Integral Composite Armour that can be used in Combat Vehicles. The Laboratory is also significantly contributing in development of aerospace structures. NPOL, a DRDO Laboratory at Kochi played a significant role in development of the Sonar Dome.
It is prudent to mention that Composite Material Technologies relevant to Indigenously developed Missiles have already been well established. DRDO is also fielding Live Demonstration of number of Systems with Cutting Edge Technologies for the first time in Defexpo.
What Is A Sonar Dome?
Sonar dome is a protective cover to sonar equipment of surface war ships. The dome is designed to house sonar array, and to maximize the performance of the array by reducing the effects of noise of water turbulence and protecting the array from wave slamming, minor collisions etc. In the design of sonar dome, both structural and acoustic considerations come into play. Typical structural constraints may include the deformation of the structure under steady external flow, accelerations, slamming loads and shock loads.
From an acoustic stand point of view, the goal is to maximize the fidelity of incoming sound by ensuring that the self-noise and flow induced noise can be inherently minimized. The current sonar domes in advanced composites bring additional benefits for strength and acoustic performance, extending the ability of the vessel to locate, evade and engage hostile environments. The sonar dome is mounted at the bow of the ship.
R&DE(E) has developed design, analysis and manufacturing capabilities of composite sonar domes. A typical dome consists of stiffeners, acoustic window area (acoustically transparent region), baffle plate, and flange with gasket for water tight connection of the dome to ship. Acoustic window area is a composite-rubber sandwich construction. Lifting hooks are provided for handling dome during handling and fitting.
R&DE(E) has established two manufacturing processes, Vacuum Assisted Resin Transfer Molding (VARTM) and Resin Film Infusion (RFI) for realization of large composite structures. Either of them can be used for realization of composite sonar dome. Both the processes require mold for realization of a structure. Since RFI is a high temperature curing process, it requires oven for curing or a heating system embedded in the mold. Whereas, VARTM can be a room temperature curing process, hence may not require any oven or heating system for curing.
To realize sonar dome, male or female mold may be used depending on factors like dimensional accuracy, surface finish, ease of lay-up, demolding etc. Type of mould shall be chosen depending on the merits and demerits of the process and finished product requirements.
In VARTM process, vacuum and resin points are provided for creating vacuum and sending resin into dry fabric, respectively. These points are decided based on guidelines obtained from process modeling and flow simulation studies. In VARTM process, resin is sucked under vacuum and it flows into the dry fabric until it is saturated with resin. To monitor resin flow online in complex regions, a process monitoring system is also available which can be deployed wherever necessary. After resin infusion, job is allowed to cure at room temperature for 24 hr then the job is demolded. Thus the complete design to manufacturing know-how of composite sonar dome is available with R&DE(E) and can be transferred to interested industry partner for commercial use.
This technology is ready for ToT to Indian Industry for supply of domes to Indian Navy/ Indian Armed Forces/ Other Govt. Agencies only. And now DRDO will hand over the technology to Defence Minister for the use in shipbuilding first by MDL, Mumbai.