underwater weapons technology is multidimensional encompassing almost all
disciplines of engineering and science. Due to technology denial, the
scientists face the most challenging task to develop every bit of
technology indigenously for which infrastructural and industry backup are
lacking. DRDO has been engaged in the development of torpedoes, sea-mines,
deep mobile target, decoy, fire control system, versatile acoustic target
and simulators. The technologies related to development of light-weight
torpedo, wire-guided torpedo, processor-based mine and fire control system
have been developed. Thermal propulsion technology, the most guarded
technology with the developed countries for heavy weight and long range
torpedoes, has been realised and will be integrated with a weapon system
soon. To meet the requirement of reduced self noise of torpedoes and to
make them more stealthy, a pumpjet propulsion system has been developed
and integrated with the torpedo. Many emerging technologies are under
development to deliver the most advanced underwater weapons to the Navy.
Torpedo is the most dynamic and
lethal underwater weapon. Design of this sophisticated and complex system
calls for technologies relating to mechanical engineering, propulsion,
power source, electronics, signal processing, control and guidance,
hydrodynamic study, aerodynamic study, suspension and release devices,
computer and software, explosive, exploder mechanism, etc. Torpedo, being
a fire-and-forget type of weapon, comprises an intelligent homing system
which has to perform an optimum search, detect target amongst decoys and
eventually guide the weapon on to the target to hit it for exploding the
explosive onboard. The shells and mechanical components used in the
torpedo are required to be of very high weight-to-strength ratio to enable
it to withstand the ambient pressure as well as the launch impact at the
same time without adding to its weight. It requires very light-weight
high-power batteries, motors, homing device, actuators and control
Different types of shells, including
composites for different torpedoes, sea water activated batteries for
electric propulsion, contrarotating motor, propellers, homing head with
PZT sensors, electronic system, onboard computers, signal processing unit
and actuation system have been developed. The first-ever indigenously
developed anti-submarine light-weight torpedo of air/ship launch version
has completed user evaluation and cleared for limited series production.
This weapon also contains the first-ever homing system to be developed by
DRDO. All sub-systems for the torpedoes have been developed indigenously.
Sea water activated Mg-AgO primary
batteries for light-weight torpedoes and Ag-Zn secondary batteries
for heavy-weight torpedoes have been developed in collaboration with High
Energy Batteries Ltd, Tiruchirapalli. Contra-rotating motors have been
developed using rare earth permanent magnets to achieve high degree of
efficiency within a smaller volume. Contra-rotating propellers have been
developed to facilitate high-speed, low-noise, cavitation-free and
roll-balanced performance for torpedo. A digital control technology has
been developed to achieve a high degree of accuracy in torpedo control and
guidance. It involves development of precision sensor, an onboard computer
based on 80486 processor and high torque and light-weight controllers.
The accuracy and hit probability of
any guided underwater weapon depends on its homing capability. Such a
system incorporating the latest signal processing techniques such as
constant false alarm rate algorithms, signal adaptive filtering etc to
counter the reverberation multipath acoustic propagation and acoustic
countermeasures has been developed. Detection algorithm, post-detection
processing techniques and mission requirement are all
software-controllable. Low-noise, high-efficiency, compact underwater
electroacoustic transducers have been used for the homing system.
For increasing the speed of
torpedoes, a thermal propulsion system will be required. DRDO is engaged
in active research in this area and has made a few significant
achievements. Fuel and oxidiser have been synthesized and technology
transferred for bulk production. An external servo-controlled swash plate
fuel pump and air impulse turbine with transmission systems have been
Contra-rotating propellers are
unable to generate high speed due to cavitation at speed exceeding 45
knots. A pumpjet propulsor has been developed successfully in
collaboration with Indian Institute of Science, Bangalore and Turbo Tech
Precision Engineering Company, Bangalore. The pumpjet propulsor has been
tested to develop more power and low-noise performance.
The submarine under the threat of an
attack from a torpedo uses several evasive methods to get away from the
attack. One such evasive method is to fire an expendable decoy which is an
electronic and acoustic countermeasure against the active-passive torpedo.
Decoys have been developed that are housed in a small FRP shell and use
lithium-sulphide batteries. These decoys can be ejected through a
cartridge. The acoustic system with transducers creates acoustic noise
mimicking that of a submarine and decoys the attacking torpedo. The
buoyancy of the decoy is critically controlled for slow descent rate.
Signal design is implemented to decoy either passive or active homing
system. Targets, mobile and static, are generally needed for training the
sonar operators and ASW crew in practising torpedo firings. The targets
imitate and simulate the submarine acoustically. The targets generate
broadband frequencies from very low to high frequencies. Several target
parameters can be set to include target strength, pulse-length, Doppler
shift and radiated nose level. A static target, called versatile acoustic
target (VAT) has been developed and extensively used in the evaluation of
torpedoes and mobile target called programmable deep mobile target (PDMT).
Mines continue to be a
cost-effective deterrent in naval warfare. These have become more and more
intelligent since World War II types of contact and magnetic mines.
State-of-the-art sea mines have been developed that work on the influence
of any one or a combination of magnetic, acoustic and pressure signals.
The pressure transducer used in the mine has also been developed
indigenously. Three types of mines, processor-based ground mine, moored
mine and processor-based exercise mine developed by DRDO, have been
accepted for production after extensive trials by the Navy. The
processor-based ground mine is already under production at KELTRON.
A triple tube torpedo launcher has
been developed and is in use onboard naval ships. Three torpedoes can be
loaded and launched from this tube.
(Courtesy : Technology
Focus, October-December 2000)