Astra MkII

Astra MkII- A new member of India’s AAM programme

-Amartya Rai

Astra project was sanctioned in 2004 with the hopes of it being the primary BVRAAM alternative on fighters like LCA Tejas, Su-30MKI, MIG 29, and Mirage-2000. Astra features a smokeless solid propellant rocket motor for propulsion, along with the indigenously designed and developed Ku-band Active RF seeker.

Performance and ECCM capability of indigenous RF seekers were extensively tested in captive flight tests against Banshee drone Targets covering multi-launch against multi-targets. Warhead trials with the destruction of targets and the coverage of the launch in the supersonic envelope of Su-30MKI were deemed successful. India has yet reached another major milestone with a successful ballistic launch from the ground launcher in Integrated Test Range today. Moreover, captive flight trials of missiles are bound to be held soon as IAF has provided 4 Su 30 MKI airframes with modifications to carry this missile.

Update on Astra MKII

The missile system was supposed to be tested a couple of months ago but due to technical glitches, the test was postponed. Since the testing rally has started again, it’s a matter of time when this crucial missile system will be tested.

A detailed analysis on Astra MK II would likely have to wait for more detail to come up but we would still cover some basic aspects of this missile. It is likely to feature a dual pulse rocket motor which gives it better range over Astra MK I which features a single stage solid propellant rocket motor. In single-stage solid propellant rocket motors, “grain”( propellent, it is basically a composition of fuel and oxidizer in plastic form ) to be burnt are already stored with compressor chamber inside missile body. Once ignited it is designed to burn smoothly at a predetermined rate on all the exposed internal grain surfaces. The resulting hot gases flow through the nozzle to impart thrust.

However, one major drawback of this design is that once ignited it is designed to burn in a uniform manner until and unless all the grain/ propellant has been used up. Thus it cannot fulfill the requirement of varying thrust on demand which multi-pulse  (dual pulse as in Astra MK II ) rocket motors provide.

Dual Pulse Rocket motor

The dual pulse rocket motor consists of two combustion chambers separated by a barrier called a pulse separation device. It prevents the ignition of grains in the second combustion chamber during phase one, which is the operation of combustion of grains in the first chamber closer to the nozzle. After burnout of the first pulse when the missile needs high maneuverability and momentum for kill/interception, the second pulse is fired. At the start of the second pulse, the pulse separation device breaks down for exhaust gases from the second combustion chamber to escape from the nozzle to provide thrust.

During the initial propulsion phase, control steering is provided by jet vanes until the missile reaches sufficient speed for the control surfaces to take over. Jet vanes are basically surfaces that are installed directly in the exhaust path of the nozzle. When the position of the vanes is changed, the exhaust is deflected causing the thrust to be directed in opposition to jet vanes. This method allows us to change to the direction of the line of action of the thrust vector in our desired favor to control the moment of the missile along different axes. A jet vanes control is also featured on Dhruvastra ATGM.

Astra MkII Configuration

Configuration of Astra MK II also features a significant change with regard to the placement and shape of control surfaces of operational Astra MK I missiles. MKI features cropped delta wings around the middle section of the missile and a set of four trapezoidal fins around the rear end for flight stability. Astra MK II might feature an indigenous Software-Defined Radio (SDR)-based active seeker with better ECCM’s capability than the current Astra seeker, which DRDO is seemed to be working on together with a private firm.

Other components of both variants of Astra missiles are likely to same such as high-explosive pre-fragmented warhead which is highly effective against fighter class targets and DRDO developed radio proximity fuse.

Check out something more about Astra MK-2.