The target missile used by DRDO to test an anti-ballistic missile in Odisha. Photo: PTI
India’s most ambitious foray into missile development is the Defence Research and Development Organisation’s (DRDO’s) anti-ballistic missile (ABM) system, designed to shoot down incoming nuclear-tipped ballistic missiles fired from Pakistan or China at Indian cities.
This technologically challenging and controversial programme has made steady headway. On March 1, an interceptor missile, fired from Abdul Kalam Island in Odisha, detected and destroyed a simulated enemy missile when it was 15-25 kilometres above the earth. The DRDO has claimed full success in most of the dozen-odd ABM tests conducted so far.
ABM systems are controversial because they destabilise the nuclear balance between two adversary countries. When one adversary, eg India, deploys an ABM shield, it incentivises the other, eg Pakistan or China, to build (and in a conflict, fire) more nuclear weapons to defeat that shield by swamping it with missiles. During the Cold War, the US and the Soviet Union guarded against this by signing an ABM treaty that sharply restricted defensive measures on both sides. Pakistan already has the world’s fastest growing nuclear arsenal, with its Khushab reactor producing plutonium full-steam.
Then, there is the technological challenge of developing an ABM shield. Striking an incoming ballistic missile is as hard as hitting a bullet with a bullet. Depending upon how far the incoming missile is fired from, it would approach the target at 1,500-3,000 metres per second (the further, the faster). With the interceptor travelling at 1,500-2,000 metres per second, the two missiles would approach each other at a relative speed of 3,000-5,000 metres every second. Guiding the interceptor to the target missile, and exploding within a few metres of it, requires precision of the highest order.
In developing an ABM shield, the designers’ first decision is: at what stage of its flight should the incoming missile be engaged and shot down? Depending upon where it is fired from, the incoming missile may have travelled just a few hundred kilometres (from Pakistan) or as much as several thousand kilometres (from China, or North Korea).
Whatever the distance, the missile would journey through three phases: boost phase, mid-course or coast phase, and terminal phase. While an ABM system could be configured to shoot it down in any of these phases, each presents its own technological complexities.
The boost phase is the most vulnerable stage in a missile’s flight trajectory, when it blasts off its launch platform and picks up speed, accelerating into space for 180-300 seconds, depending upon the missile’s range. This is when the missile travels at its slowest and cannot perform evasive manoeuvres or deploy decoys or counter-measures. The difficulty, however, is that since the missile is at its launch pad, intelligence satellites would have to monitor enemy territory to pick up indications of a launch. Then, in the short time available, the interceptor missile would have to be fired and travel all the way to the launch area.
Next comes the mid-course phase, in which the missile travels through space towards its target. This lasts just seconds for a short-range ballistic missile fired from Pakistan; or as much as 20 minutes for long-range ballistic missiles fired from several thousand kilometres away. Mid-course engagement provides a longer time-window for sensing, decision-making and engagement; and a shorter distance for the interceptor to travel.
However, ballistic missiles often release decoys in this stage, requiring the interceptor to differentiate between the decoys and the mother vehicle.
The final engagement opportunity is in the terminal phase, when the incoming missile starts descending, re-enters the atmosphere and hurtles towards its target. “Terminal phase engagement” gives the ABM system maximum time for detection and decision-making and requires the interceptor missile to travel the least distance. The downside is that many ballistic missiles are programmed to carry out manoeuvres when they re-enter, making them difficult to target.
India’s ABM shield
An ABM shield has three functional components: First, a radar network that can detect enemy ballistic missiles as soon as possible after launch; and then track them along their flight path. While a ground-based radar’s range is limited by the earth’s curvature, a satellite-based radar can pick up a ballistic missile’s fiery plume as soon as it is fired. The DRDO’s primary ABM radar is the Long Range Tracking Radar (LRTR), developed in partnership with Israeli company Elta.
The LRTR is based on Elta’s EL/M-2080 Green Pine radar, which is the nerve centre of Israel’s vaunted Arrow ABM system. Separately, the DRDO is working on a satellite-based sensor that would be integrated into the ABM system, once perfected.
The second functional component of the DRDO’s ABM system is a sophisticated, computerised command and control system that plots and predicts the intruder missile’s flight path and assigns interceptor missiles to destroy it. With very little time available for humans to weigh choices, almost all decision-making relating to engagement choices is automated.
The third component is the interceptor missiles, of which the ABM shield has two different types. One is an exo-atmospheric (or “outside atmosphere”) missile called the Pradyumna which intercepts the intruder while it is 50-80 kilometres above the earth. The other, called the Ashvin, is an endo-atmospheric (“inside atmosphere”) missile that intercepts the enemy ballistic missile at altitudes of 20-40 kilometres. They are normally fired together (in a “salvo”) to increase the chances that at least one missile will destroy the target.
After they are launched, the guidance radar directs them towards the target; once in its vicinity, a “proximity fuze” explodes the warhead, damaging the intruder missile and warhead.
Range is a key determinant
Given how close India is to Pakistan, it takes just 5-15 minutes for the entire engagement, from launch to interception. A missile fired from a Pakistani launch site would take just 5-6 minutes to reach targets in north India, a few hundred kilometres away. Targets in south India, 1,500-2,000 kilometres away from Pakistan, would take 10-15 minutes to reach. Paradoxically, being close to India is a disadvantage to Pakistan because the closer a missile is fired from, the slower it travels in its terminal phase, making it easier to intercept.
India’s ABM shield is geared to intercept missiles fired from up to 2,000 kilometres away. A short-range Pakistani ballistic missile like the Shaheen 1A (Hatf IV), with a range of 900 kilometres, would have a warhead re-entry speed of about 2,000 metres per second, which Indian ABM interceptors can manage.
The Shaheen-II (Hatf VI), with a range of 2,000 kilometres, would have its payload re-enter at 2,500-3,000 metres per second, which is just within the range of the Indian ABM system.
Pakistan’s longest-range missile is Shaheen III, with a range of 2,750 kilometres, which was developed to bring the Andaman & Nicobar Islands into range. The Shaheen III, like China’s longer-range missiles, cannot yet be intercepted by India’s ABM system. However, paradoxically, Pakistan’s lack of geographical depth means the Shaheen II and III cannot be used against north Indian targets like New Delhi, which is barely 1,500 kilometres from Pakistan’s farthest regions. To avoid overshooting Delhi, Pakistan would have to use the shorter range Shaheen I, which is easier to intercept.
Future of ABM
In 2011, former DRDO chief Avinash Chander told Business Standard that an ABM shield would protect the national capital within three years. Chander’s predecessor, VK Saraswat, had provided even more optimistic time-lines, raising concerns worldwide over the erosion of deterrence in South Asia.
Since then, the government has issued strict orders to the DRDO not to speak about the system. Currently, the development of the ABM system can only be gauged mainly from reports of interceptor test flights and the move of radars to sensitive locations like New Delhi. Over recent years, two LRTRs were moved to Delhi and integrated into the Indian Air Force national surveillance network.
Even as the ABM system successfully crosses developmental milestones, analysts warn against excessive optimism and overblown expectations. In most nuclear war-gaming in the US, ABM defences have been overcome relatively easily by expedients as simple as swamping the defences with missile salvos, or with multiple independently targetable re-entry vehicles (MIRVs), that are essentially several independent warheads fitted onto a single missile.
On January 24, Pakistan test-fired its new Ababeel ballistic missile, which it claimed was a MIRV system, “aimed at ensuring survivability of Pakistan's ballistic missiles in the growing regional ballistic missile defence (BMD) environment”. The cat and mouse game with missile defence seems set to continue.