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Saurav Jha
Saturday , August 30, 2014 at 16 : 53

Some notes on DRDO's PDV ballistic missile defence interceptor


In late April, the Defence Research and Development Organization (DRDO) unveiled the PDV, which has been designed to serve as an exo-atmospheric interceptor for India's emerging two-tier ballistic missile defence (BMD) system consisting of both endo and exo atmospheric interception capability. The PDV's first test was essentially used to validate the capabilities of its on-board imaging infrared (IIR) seeker as well as the capabilities of a new target missile used for this test. As such neither an actual hit to kill (HTK) nor an explosive intercept was orchestrated by DRDO technologists in this test since the idea it seems was to glean as much data as they could from both the IIR seeker as well as the target missile. Nevertheless, this maiden outing for the PDV seems to have validated its integration with the detection, tracking and automated launch control systems associated with the two-tier BMD scheme.

Future tests will however look to prove the new kill vehicle (KV) used by the PDV for destroying an incoming warhead besides testing the entire envelope of its solid propulsion system. Once the development of the PDV is successfully completed it would signal the maturing of Phase-1 of India's BMD program which is designed to provide credible capability against theatre ballistic missiles (TBM) launched from up to 2000 kms away. The emergence of the PDV also makes the case for expediting work on new missile test ranges stronger, which would in any case be required for the range and geometry considerations associated with Phase-2 of India's BMD.

The PDV essentially replaces the PAD, which was first tested in 2006, as the kill vector in the high altitude interception leg of the two-tier system conceived under Phase-I of the BMD programme. However while the PAD was essentially a high endo-atmospheric system with a ceiling of around 85 km, PDV is a true blue exo-atmospheric interceptor capable of intercepts at up to 150 km. Indeed, the late April test involved a 'near miss' at an altitude of 120 km. This puts the PDV in a different category in terms of its propulsion system, navigation set-up and homing seeker capability. Instead of sporting a radio frequency (RF) seeker like the PAD, the PDV uses a new IIR seeker developed by DRDO's Research Centre Imarat (RCI) that has interestingly drawn on its work over the years with the Nag seeker which has an array size of 128 x 128 pixels.

Exo-atmospheric interception certainly has its advantages in terms of extending the amount of time time available to the BMD system to direct the interceptor towards the target.

On the other hand interception outside the atmosphere of a medium range ballistic missile (MRBM) re-entry vehicle (RV) may require that the BMD system distinguish between it and decoys, that might be released by the boost vehicle in order to create false targets. This target discrimination is achieved in the 'cold' of space by using an IIR seeker. In this first test, the PDV's inertial guidance package consisting of possibly a mature fibre optic gyroscope moved the missile towards the estimated point of the interception as calculated by ground based radars and fed to the guidance package before the IIR seeker took over in the end game to track the RV.

A new interceptor of the class of the PDV also requires a new MRBM class target missile for effective trials. With this test DRDO also unveiled a new two stage target equipped with new motors that successfully mimics the 3-5 km/sec re-entry speeds of a 'hostile ballistic missile approaching from more than 2000 km away'. The target missile was fired from a naval platform sitting offshore but it is unclear whether this first test involved decoys.

Now, one of the things to check in a layered approach to BMD is the modularity of the systems involved which allows the use of different interceptors with a command and control network that is the same leading to cost savings through logistical simplicity and interoperability characteristics. The first PDV test in that sense demonstrated the integration of this new interceptor with DRDO's proven ground based automated response network that forms the backbone of the two-tier BMD scheme.

The PDV test served as yet another chance to validate DRDO's BMD architecture which consists of both over the horizon and X-band fire control radars which detect and track the incoming missile, a mission control centre (MCC) that fuses input(which may come from satellite based sensors also) processes it and sends orders for engagement to launch control centres (LCCs) situated 1000 km away via mobile communication terminals (MCTs). The LCCs then orchestrate the final launch sequence with the mobile interceptor sitting nearby. Repeated tests of the two-tier system, including the latest PDV test has given enough confidence to DRDO to recommend the freezing of the current configuration for Phase-I.

Both the radars and the LCC receive and send information via target update transmitters (TUTs) based on CDMA technology. While the MCTs of the MCC are themselves connected via an IP wide area network, data-links for the entire setup also include fibre optic communication channels and line of sight relays.

It is unclear whether the long range tracking radar(LRTR) used in this test is DRDO's legacy Swordfish with a range of 600-800 km or a new design that has been in development and can track cricket ball sized targets up to 1500 km away. The test probably did however involve the 3D Multi-Function Control Radar (MFCR) developed by DRDO's LRDE in collaboration with Thales.

The PDV itself, given its role as an exo-atmospheric interceptor is obviously larger and has more on-board fuel than the AAD endo-atmospheric interceptor. The PDV uses solid propellants which have high burn-rates and can function effectively in temperatures ranging from minus 40 degrees to 50 degrees Celsius above zero. This kind of an operating paradigm needs special casting for the propellants developed by DRDO's High Energy Material Research laboratory (HEMRL). PDV is also designed to have a shelf life of 10 to 15 years and its motors have a high margin for safety while retaining quick reaction capability - all of which contribute to it being a ready to use package slaved to an automated launching mechanism. Moreover PDV's motors obviously have to be fairly robust to withstand the rigours and vibrations induced by mobility.

Even as DRDO's BMD programme accelerates, there is a need for quicker forward movement on building the new missile test ranges in Machilipatnam in Seema andhra and Rutland Island in the Andamans. These ranges will cater to varying geometries and facilitate tests that involve intercepting salvos of incoming missiles. DRDO till date has been unable to conduct an all up salvo interception test precisely on account of this range limitation issue. Till date it has conducted only a 'partial' salvo trial in 2012, which included an actual endo-atmospheric intercept and an electronically simulated exo-atmospheric intercept.

While the new range in Machilipatnam is being built at an estimated investment of Rs 1,000 crore and may be operationalized in the next three years, the timelines for Rutland Island are still unclear. As part of Phase-2 of the BMD programme DRDO is developing two new interceptors AD-1 and AD-2 which are capable of neutralizing RVs delivered by ballistic missiles fired from more than 5000 km away. This would mean intercepting RVs flying at 6-9 km/s and this cannot be done without new ranges that are located some distance away from each other. The future growth of DRDO's BMD system therefore requires that the new ranges are operationalized expeditiously.

Left unsaid in this latest BMD test by DRDO is the clear demonstration of the low earth orbit (LEO) capabilities of the PDV. The PDV is actually a predecessor to another exo-atmospheric interceptor currently under development that can neutralize RVs at an altitude of over 300 km. Taken together this means that India has all the elements in place for a direct ascent counter space system that can easily be used for anti-satellite purposes. This in turn means that India now has a very strong hand in the Space NPT that is currently being quietly negotiated by the world's nuclear powers.

Follow Saurav Jha on twitter @SJha1618. Send your feedback to geekatlarge1618@gmail.com


More about Saurav Jha

Saurav Jha is an author and commentator on energy and security affairs who writes regularly for numerous publications including The Telegraph, World Politics Review, The Diplomat, Le Monde Diplomatique and Nuclear Engineering International. He has degrees in economics from Presidency College, Calcutta and Jawaharlal Nehru University, New Delhi. His first book, The Upside Down Book of Nuclear Power (HarperCollins India) was released to critical acclaim in 2010. His next work on sustainability issues due for release in late 2015 and tentatively titled The Nexus (Hachette India) explains how the nexus between energy, food and water pushes urbanizing economies towards stagflation. He has also co-authored The Heat and Dust Project (HarperCollins India) with wife Devapriya Roy, chronicling a 16000 km long backpacking trip through India on an extremely tight budget.