Ballistic missile defense systems have exploded in prominence across the globe since the United States withdrew from the 1972 Anti-Ballistic Missile (ABM) Treaty in 2002. Designing integrated radar warning systems and interceptor batteries that can shoot down a ballistic missile in flight is often described as akin to knocking down a bullet with another bullet, but the technology to perform such a feat is now entering service in countries like Japan , South Korea and Saudi Arabia.
India’s acute interest in missile defense predates the demise of the ABM treaty, however, as it came uncomfortably close to a full-scale conflict with a nuclear-armed Pakistan during the 1999 Kargil War. This led New Delhi to begin early development of an ABM system which accelerated after the Washington vetoed a bid to acquire the Israeli Arrow-2 interceptor in 2002. With the successful testing of the Prithvi Air Defense missile in 2007, India became only the fourth country to have developed a functioning ballistic missile defense system, ahead even of China.
A decade later, New Delhi has finally begun setting up a two-layer ballistic missile defense shield that initially will protect New Delhi and Mumbai. The Prithivi Air Defense (PAD) system will provide long-range high-altitude ballistic missile interception during an incoming missile’s midcourse phase, while the Advanced Air Defense system offers short-range, low-altitude defense against missiles in the terminal phase of their trajectory. Reportedly the first batteries have begun installation in two villages in Rajasthan.
Together the two systems offer only patchy protection of certain key cities. The Indian Defense Research and Development Organization (DRDO) is currently testing a successor to the PAD—the Prithvi Vehicular Defense—with greater range and speed, and a maximum interception altitude approaching that of the U.S. THAAD system.
The Indian ABMs are cued onto their targets by giant Swordfish Long-Range Tracking Radars, an indigenously built derivative of the Israeli Green Pine radar, which is used in BMD systems in both Israel and South Korea . The Swordfish currently has a range of 500 miles, though there are plans to upgrade it to over 900 miles. It can track up to 200 targets simultaneously, and is claimed to have the resolution to detect an object the size of a cricket ball.
At first glance, the Prithvi Air Defense missile seems quite capable, with a range of 1,250 miles and a maximum altitude of 260,000 feet, making it an exospheric interceptor. The missile is programmed prior to launch by the BMD command center on an intercept trajectory, which it maintains using an inertial navigation system. It receives midcourse updates to its trajectory using data from the Swordfish radar, and then in the terminal approach phase switches to its own active radar seeker and destroys the target with a proximity-fused warhead.
In multiple tests, the PAD has successfully shot down Indian Prithvi short-range ballistic missiles (same name, different system) at altitudes as high as 246,000 feet. Traveling at speeds of Mach 5, the PAD in theory is fast enough to hit speedier, higher-flying medium-range ballistic missiles, but would struggles versus intermediate-range types.
However, a major limitation of the PAD is that the second phase of the two-stage rocket uses liquid fuel. As liquid rocket fuel corrodes fuel tanks when stored for long, the PAD could not be on standby 24/7. Instead, it would need to be gassed up during a period of crisis in anticipation of trouble. This is less than ideal for a weapon intended to defend against an attack which might come at any moment.
For defense at low-altitudes, the solid-fuel Advanced Air Defense system, or Ashwar, uses an endospheric (within the Earth’s atmosphere) interceptor that knocks out ballistic missiles at a maximum altitude of 60,000 to 100,000 feet, and across a range between 90 and 125 miles for local defense. The AAD has performed successfully in most tests against targets at altitudes of 50,000 feet, though an improved model failed a test in April 2015 before succeeding in subsequent attempts. It is claimed the Mach 4.5 missile might also have application against cruise missiles and aircraft.
The new Prithvi Defensive Vehicle looks to be a promising “Phase 2” replacement for the PAD. This new two-stage exo-atmospheric interceptor uses only solid-fuel rockets, and can theoretically hit targets nearly as high as 500,000 feet at a range that may be as far 3,100 miles. Upon leaving the earth’s atmosphere, the interceptor ditches its heat shields and activates an infrared seeker that helps it discriminate between decoys and its target.
The PDV’s first test in 2014 missed its target but was still proclaimed a success. A second test on February 2017 succeeded in striking a Prithvi II missile. The PDV is believed to be faster than the PDA, possibly giving it IRBM-interception capability.