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INTEGRAL RAM ROCKET (IRR) PROPULSION SYSTEMS

Fuel-efficient air breathing propulsion system was developed exclusively for Project Akash.  IRR propulsion system provides powered range right up to target intercept enabling high maneuverability and tail chase capability unlike solid rockets.

Following subsystems were developed ab initio for realizing IRR propulsion system.

  • Light weight, high pressure rocket motors using indigenous maraging steel, an indigenous high strength alloy steel.
  • Secondary chamber liner / thermal protection system using carbon phenolic fiber.
  • Composite propellant booster grain in free standing configuration.
  • A special grain with variable burn rates was developed and productionised at OF, Itarsi which is also specific to Akash & application.
  • Air intakes and caps are designed for ramjet application.

The IRR propulsion system is first in the country & it has potential application for long range air launched missile systems for air-to-air and air-to ground role.  Not many countries have worked in the complex area of ramjet propulsion

C4 I SYSTEM HARDWARE AND SOFTWARE FOR AIR DEFENCE APPLICATION

Akash medium range surface to air for area defence weapons system employing Group mode functioning.   A group head quarters is a C4 I center which controls and coordinates the air defence activity over area against the airborne threats.

 

DUAL CONTROL DIGITAL AUTOPILOT & PN GUIDANCE

Akash missile uses tail and wing control simultaneously for stabilization and maneuver. Digital autopilot controls six actuation channels in closed loop for achieving the missile control. The autopilot uses adaptive gain scheduling technique to maximize the control effectiveness for entire trajectory of the missile for various target engagement condition. The autopilot is implemented in high-level language in the onboard computer.

The latax control is through the two wing channels in both pitch and yaw planes. The rate stabilization is through two pairs of TCP channels. Roll control is through differential deflection of four TCPs. The control strategy for stabilizing both roll and rates using same TCPs employ dynamic sharing logic to effectively utilize the available maximum TCP deflections.

During boost phase of the missile, attitude hold is implemented to minimize the missile dispersion about the nominal launch attitude for assured gathering by Radar at designated position in space. The autopilot has been extensively flight tested for various regimes of missile kill zone and proved to be very effective and robust.

SUPERPLASTIC FORMED HP AIRBOTTLE  

High pressure air bottles are used to store moisture and oil free compressed air at 400 KSC to provide regulated supply of air for electro pneumatic actuators of control system of Akash missile. Air bottles are made out of Ultra high strength titanium alloys. Conventional manufacturing techniques are not suitable for forming of hemispheres. Raw material is heated to plastic stage and specially designed tools are used to form hemispheres having very low d/t ratio. The entire process has to be carried out in controlled atmosphere to avoid oxidation at elevated temperatures.

The air bottles have been used in all the flight vehicles flight tested so far and reliability of the performance has been established.  

TANDEM WARHEAD SYSTEM

The ‘NAG’ warhead is an indigenously developed shaped charged Tandem warhead for antitank role. It consists of two shaped charges namely the Precursor Charge and the Main Charge.  

The Precursor Charge is designed to defeat the Explosive Reactive Armour (ERA) protection and the Main Charge is designed to neutralize the main armour of the tanks.  The warhead is provided with an Impact Sensing Mechanism (ISM) and a Safety Arming Mechanism (SAM).  On impact of the missile on the target, the impact sensing mechanism generates a command, which initiates the charges through safety arming mechanism. The Safety Arming Mechanism ensures safety during storage, handling & missile firing.  It enables arming of the warhead at a safe distance and detonates warhead on impact of missile on target.

In shaped charge, Warheads High Speed metal jet produced by the collapse of a metallic cone under explosive loading inflicts the desired target damage.  This metallic jet acts as a carrier of energy and transports portion of explosive energy to the target. 

 

THERMO STABLE LIQUID FUEL CHARGING TECHNOLOGY

   

The BrahMos Missile is propelled by two stage propulsion system of liquid and solid propellants. For the Liquid Ram Rocket Engine, there is an essential need to fill in a highly purified gas free liquid fuel of exact volume into the fuel tank.  The conditions applied for this are very stringent for the gas concentration in the fuel.  The de-gasification process is carried out by Nitrogen gas purging and spring methods. To ensure this, a system has been indigenous developed in DRDL with

complete indigenous design and manufacturing technology.  The system consists of double wall tank for de-gasification of liquid fuel within the stipulated time.  This fuel is also being used in hydraulic actuation systems.  The total fuel processing and charging procedure is carried out under vacuum conditions to avoid contamination during the process.  

FIRE CONTROL SYSTEMS  

BrahMos Fire Control System, known as BFCS is indigenously designed and developed for BrahMos Supersonic Cruise Missiles. It aids the user in planning the trajectory, Pre-Launch preparation and Launch of missiles. It has an option to introduce waypoints in the trajectory for better exploitation of BrahMos system. The FCS can be configured to launch the missiles in either single or salvo mode with an option to program the launch interval.

Two versions of FCS have been designed and developed: Ship Borne FCS for Indian Navy and Shore Based FCS for Indian Army.  

EVOLUTION OF AERODYNAMIC CONFIGURATION OF HYPERSONIC AIR BREATHING VEHICLE 

The crucial requirement for the hypersonic vehicle is the stability at cruise and positive thrust margin. Satisfactory performance has been achieved under power on and power off conditions. The aerodynamic configuration is non-circular (octagonal), which is non-conventional too. The performance enhancement has been obtained by incorporating fences at forebody and rearbody. Cowl extension at the nozzle improved the stability of the vehicle at cruise. 

DESIGN OF HYPERSONIC AIR INTAKE 

External compression in the forebody and internal compression in the air-intake have been achieved for the hypersonic flight. Analytical and computational methods have been developed for the design of air-intake enhancing pressure   recovery and minimizing loss. The starting performance has been evaluated through CFD.

Suitable experiments are designed and conducted. Starting of isolated intake and integrated intake using suitable air intake cowl opening mechanism have been designed and realized. Enhancement of the performance with boundary layer bleed has also been attempted. 

DEVELOPMENT OF SCRAMJET ENGINE TEST FACILITY 

The scramjet engine development is the critical path towards realization of the HSTDV. The Engine is designed for hydrocarbon (Kerosene) fuel combustion, which would make the hypersonic vehicle economical for the service usage. Connect pipe test facility with elaborate instrumentation and data logging capability has been established. The operation of the facility is fully automated through PLCs and other control devices.

Two versions of scramjet combustors viz., strut based fuel injection and ramp cavity based fuel injections are being developed. Half width model combustor static tests (10 Nos.) have been conducted so far. Extensive CFD analysis has been carried out for half width model and full scale model combustors. The full scale engine is being realized for conducting static tests in the connect pipe facility. 

MANUFACTURING PROCESS FOR THE SCRAMJET ENGINE

The scramjet engine construction is a double wall construction with special alloy used for the inner wall facing combustion region and the outer back up of another special alloy to provide the structural strength. These two alloys have to be joined continuously along the surfaces of their contact. The explosive welding gives the quickest way of joining these materials effectively. The explosive welding trials were done. This manufacturing process has been established to realize engine hardware for subsequent testing. 

DESIGN OF AEROSPACE MECHANISMS FOR THE HYPERSONIC VEHICLE 

The HSTDV mission is mechanisms intensive. They are viz., the air intake flap mechanism, separation mechanism, unfolding mechanisms for the wings and tails of the cruise vehicle and the nozzle flap mechanism. The design of these mechanisms is the high temperature environment of the hypersonic flight is realized. 

CONTROL GUIDANCE ALGORITHM FOR CLOS GUIDANCE 

In order to achieve shortest possible range of a weapon system, it is essential to develop CLOS guidance scheme in which missile is guided to the LOS in the quickest possible time. This technology has been developed for the first time in the IGMDP. Trishul system has been developed using this technology and it was demonstrated through 80 flight tests using various kinds of platforms. Required miss-distance (» 10 mtr.) has been demonstrated repeatedly through live firings against targets.  

HEIGHT LOCK LOOP GUIDANCE ALGORITHM:

Trishul is the first indigenous supersonic missile having capability of flying 5 meters above the sea-surface. This has been possible by design of a sophisticated height lock loop guidance algorithm using a precision Radio Altimeter as a height sensing device. The sea-skimming capability of Trishul missile has been demonstrated through a large number of live firings from Naval Trishul Shore Installation at INS Dronacharya.  

LITHIUM THERMAL BATTERY 

Lithium Thermal Batteries have high power density and very long shelf life (in excess of 20 years). Trishul missile borne lithium thermal batteries have been indigenously developed, qualified & produced in large numbers.  

DUAL THRUST ROCKET MOTOR 

Dual Thrust Rocket Motor has been designed and developed indigenously for Trishul missile. Smokeless composite propellant has been indigenously developed for this Rocket Motor. Rocket Motor has been flight tested several times without any flaw.  

LAUNCH CONTAINER 

Trishul missile is delivered as ammunition in a FRP canister. This launch container has been indigenously developed with various mechanisms like automatic umbilical retraction, transport-locking mechanism etc., along with its electrical interfaces.  

FOLDING FIN TECHNOLOGY 

In order to have minimum dimension of the launch container to accommodate more number of missiles on the launcher, folding fin mechanism has been developed for Trishul missile. All the four fins are folded when the missile is within the launch container. They automatically are deployed as soon as the missile moves out of the launch container. Design and implementation of the fin folding Mechanism has been a real challenge. Folding fin mechanism has been qualified through large number of flights tests without any failure.  

FLOW FORMING TECHNOLOGY 

Novel manufacturing technique called flow forming has been established for manufacturing of Trishul airframe structures. This technology has been successfully utilised for manufacturing of maraging steel rocket motor tubes, and other airframe structures of Trishul. This technology has played crucial role in reducing the hardware weight of Trishul missile.  

MATERIALS FOR HYPERSONIC VEHICLE 

The materials have to be chosen to retain the required strength levels at the elevated temperatures. The short duration mission materials are required for the engine walls to withstand high temperatures, another special alloy as a structural back-up to the first alloy, a Titanium alloy for airframe and carbon composites for high temperature regions. These materials with appropriate coatings would be suitable for the short missions.        

The thermal barrier coatings (TBCs) bring down the surface temperature levels to the ones within the capability of the materials. Many TBCs were tried out by thermal tests and erosion tests and it is found that ceramic based coating developed which is best suited for the application. The technology development is done in various work centres. Based on the testing and feebback from the designer, the technologies will be improved.

 

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