THE Defence Research and Development Organisations (DRDO) prowess in advanced software that goes into the making of interceptor missiles was proved convincingly on March 6 when a Prithvi interceptor missile achieved a direct hit-to-kill on an enemy missile. The interception took place at an altitude of 80 kilometres when a modified Dhanush missile, launched from the naval ship INS Subhadra in the Bay of Bengal, was in its descent phase and hurtling towards Wheeler Island, off Orissas coast. Dhanush was simulating the final phase of the trajectory of ballistic missiles with a range of 1,500 km, such as Pakistans Ghauri missile. At the end of over five minutes of heightened suspense at the Launch Control Centre (LCC) on Wheeler Island, the Prithvi interceptor missile cut into the path of the incoming Dhanush missile, knocked it out and also pulverised the latter with its new manoeuvrable warhead.
Such was the accuracy of the interception that those scanning the plot-boards at the LCC celebrated like never before. India was finally on the way to acquiring a ballistic missile defence shield to thwart enemy attacks. In terms of strategic importance, the success established Indias capability to intercept Pakistans Hatf and Ghauri missiles.
Our strength is our software, V.K. Saraswat, Programme Director, Air Defence, DRDO, had declared in November 2008. In the ballistic missile defence shield, if there are glitches in the software, it cannot be excused. It has to work thoroughly. There are a million lines of code. The onboard software runs in real time in the interceptor missile.
Saraswat called the March 6 success a major test in assembling the ballistic missile defence system as part of network-centric warfare. He added: In the next 25 years, you will see a growth in the direction of network-centric warfare. So we are making these building blocks.
It was the third success in a row for the DRDO, which has been making all-out efforts to acquire a two-layered ballistic missile defence shield with interceptors that can shoot down incoming missiles. It tasted success in its first mission on November 27, 2006, when a Prithvi missile intercepted a Prithvi-II missile at an altitude of 48 km in what is called the exo-atmosphere. It was a direct hit. The interceptor was called Prithvi Air Defence (PAD-01). Again, on December 6, 2008, an Advanced Air Defence (AAD) missile shot down a modified Prithvi missile at an altitude of 15 km in what is called the endo-atmosphere when the attacker was in the final stage of its flight. It was a direct hit too. With the March 6 direct hit, the DRDO has achieved a hat-trick.
If the interception on March 6 took place at an altitude much higher than in the previous missions, there are distinct advantages to it. The debris will take longer to fall through the atmosphere and become cinders because of re-entry heat. In an actual war, this will reduce the effect of any fallout of the debris of a nuclear warhead and the risks associated with radiation.
Three features stood out in the latest mission: the Prithvi interceptor missiles gimballed/manoeuvrable warhead, which can rotate 360 degrees; the interceptors coasting phase, which can take care of the manoeuvres performed by the attacker; and the very advanced software residing in the computers of the interceptor. The warhead is called a directional one because it can be directed to explode towards the target. Only the U.S. and Russia have gimballed directional warheads.
Regarding the software used in the interceptor, Saraswat said: The software of the guidance, control and navigation systems, which was generated by our scientists in Hyderabad, is practically the high watermark of the technology of our ballistic missile defence system. It will not be out of place to say that while many countries have been struggling for many years to get this kind of performance, it is to the credit of the young team at the DRDO that it made this mission a success. As far as the programme is concerned, this is a major milestone in proving the capability of our ballistic missile defence shield. The computer controlled, navigated and guided the vehicle towards its target, besides performing a series of mission-sequencing tasks. Besides, the interceptor had a special software to discriminate the terminal phase of the enemy missiles flight. Interceptions would take place in the terminal phase.
Dhanush, the enemy missile, was a single-stage missile with a diameter of one metre, a weight of 4.5 tonnes, and a height of 9.4 m. Propelled by liquid fuel, it quickly climbed to an altitude of 150 km, cut a parabola and started heading towards Wheeler Island. About 50 seconds into its flight, radars at Konark and Paradip in Orissa tracked the missile and relayed the information to the Mission Control Centre (MCC) on Wheeler Island. The MCC then analysed whether it was a ballistic missile or an aircraft. Within five seconds, the MCC concluded that it was a hostile target which would impact close to Wheeler Island very soon. This information was received by the LCC, which used it to compute the trajectory of the interceptor to engage the incoming ballistic missile. It then decided that the interception should take place at an altitude of 80 km when Dhanush was in its descent mode. The LCC also quickly decided when the interceptor, named Prithvi Air Defence (PAD-02), should lift off. When the launch computer gave the command for it to blast off, the two-stage interceptor, 10 metres tall, weighing 5.2 tonnes and having a diameter of one metre, rose from a truck on the beach-head on the island. While its first stage was powered by liquid fuel, the second stage had solid propellants.
About five minutes and ten seconds later, when the interceptor had reached an altitude of 80 km, its homing seeker acquired the target when it was 25 km away. Using this information, the interceptors computer guided it towards the target and brought it within a few metres of Dhanush.
At this point of time, the radio proximity fuse (RPF) of the gimballed directional warhead calculated the distance from Dhanush and the time at which the warhead should detonate.
When the interceptor and the target were practically colliding with each other, the warhead was detonated, which led to the fragmentation of the target and the interceptor. It was a direct hit and also a warhead detonation. A large number of fragments formed due to the collision and detonation of the warhead were tracked by ground radars and the radars on ships. We could see on our plot boards hundreds of new tracks being formed, confirming that it was both a direct hit and a detonation, Saraswat said.
The highlights of the mission were proving the technology of the gimballed directional warhead and demonstrating the interceptors coasting phase, using a vernier thruster. This coasting phase in the interceptors trajectory helps it to decide at what stage it should intercept the enemy missile. If the attacker does a manoeuvre, the interceptors guidance system will take care of it. To make the seeker effective, the DRDO used a wide-beam RPF in the warhead, which was a mini-radar. So even if there is a manoeuvre by the enemy missile in the last 500 milliseconds, the RPF will be able to take care of it. The directional warhead will be ignited on the basis of the data given by the RPF, said Saraswat.
Another major element employed in the mission was the advanced battle management command, control and communication software, which resided in the MCC. The entire event was tracked by a number of ground stations with complete mobile and static communication systems provided by satellites, fibre optics and line-of-sight communication.
Saraswat said: It was a mission planned, designed and executed with clockwork precision. It proves the robustness, reliability and repeatability of the design of Indias emerging ballistic missile defence system, which can take care of incoming missiles with a range of 300 km to 1,500 km. It demonstrates that the DRDOs ballistic missile defence shield has reached a great level of maturity.
W. Selvamurthy, Chief Controller, DRDO, predicted that in the wake of the hat-trick of successes, Indias ballistic missile defence shield would be ready for deployment in about four years. It will take us a couple of more trials before our system is ready to be offered for deployment. In the next trial, we will do combined interceptions in both the exo-atmosphere and the endo-atmosphere, he said.
Saraswat praised the synergy and the collective skill and knowledge of the DRDO laboratories which made the mission a success. They included the Research Centre Imarat, the Advanced Systems Laboratory and the Defence Research and Development Laboratory, all located in Hyderabad and collectively called the missile complex; the High Energy Materials Research Laboratory, the Armament Research and Development Establishment, and the Research and Development Establishment (Engineers), all located in Pune; the Electronics and Radar Development Establishment, Bangalore; the Terminal Ballistics Research Laboratory, Chandigarh; and the Vehicle Research and Development Establishment, Ahmednagar.