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Astra-2 Solid Fuel Ducted Ramjet (SFDR)

The Solid Fuel Ducted Ramjet (SFDR) project was started in May 2013 with the objective of developing state-of-the-art SFDR propulsion technology, which can operate at varying altitudes and speeds. The development and demonstration of SFDR propulsion system is a joint venture of DRDO and Russia. Its successful use in missiles will mark India’s entry into a select club of nations that use next-generation missile technology against maneuvering targets, compromising the effectiveness of conventional missiles.

India's new surface-to-air missile is powered by Solid Fuel Ducted Ramjet (SFDR) achieved a speed of Mach 3 during its first test flight in May 2018. The missile, which is viewed as the Indian version of the French Meteor, was launched from the Integrated Test Range facility off the coast of Odhisha.

It was a booster phase test of the missile and the mission was a major milestone for the strategic missile program. The nozzle, less booster, and SFDR was tested successfully. The DRDO will test other components of the missile such as its high technology seeker equipment very soon. The 250-kilogram SFDR missile has been under development since 2013.

The new technology will help both surface-to-air and air-to-air missiles perform better and enhance their strike range, making the weapons more lethal. Now India can have the fastest long-range missiles in the two categories, providing full-fledged and multi-layered aerial protection from hostile attacks.

Calculations indicate that sufficient fuel for short (approximately 20 miles) and perhaps intermediate range (100- 200 miles) missiles can be stored within the combustion chamber proper without occasioning undue internal drag losses. By this expedient, fuel tanks, pumps, meters, injectors and their associated plumbing, and even the pilot and flame holders, can be eliminated. Packaging the fuel within the combustion chamber to eliminate the fuel system components leads to complications as well as simplification. For example, the problem of obtaining fuel-charge geometries having sufficient surface exposed to the air stream to provide the necessary over-all rate of heat release, and yet remain compatible with the requirement of a low internal drag, plagued most of the early investigators.

The present lot of missiles, which use a booster/sustainer configuration with solid or liquid propellants, have limitations against maneuvering targets, since conventional missiles, at the terminal stage, cannot provide enough energy to maintain their speed in order to hit the targets. SFDR technology will exceptionally enhance endgame maneuverability at the terminal stage when the seeker is locked onto a target.

Ramjets require a rocket booster, or gun launch, to achieve a flight condition where thrust is greater than drag, which for missiles is approximately Mach 2, at which point the ramjet is capable of accelerating to higher speed. Since the ramjet propulsion system depends only on its forward motion at supersonic speed to compress intake air, the engine flow-path components have no moving parts. Consequently, it has inherent simplicity, reliability, light weight, and high-speed flight capability not possible with other air-breathing engines. These attributes make the ramjet a good choice for propelling medium-caliber cannon ammunition at supersonic speed.

In a solid-fuel ramjet, air from the inlet flows through the "pipe" of fuel (also known as a "fuel grain"), which burns along its length. Unlike solid rocket propellant whose formulation is approximately 20% fuel and 80% oxidizer, the solid ramjet fuel is 100% fuel and obtains oxidizer from air, with the result being approximately four times the specific impulse (the product of thrust and time divided by propellant weight) as compared to solid rocket propellant. The higher specific impulse translates to either longer range for a given payload weight and volume, greater payload to a given range, a smaller size to a given range, or a combination of all three compared to a solid rocket motor.

The design scheme is very similar to that of Meteor BVRAAM with two air ducts, although DRDO’s 250kg SFDR is around 75kg heavier than 185kg Meteor. Unlike traditional rocket motor, SFDR can throttle its engine during different phases of flight especially while approaching its target it can throttle up and able to maneuver and attack even rapidly maneuvering targets.

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Page last modified: 02-06-2018 18:29:27 ZULU