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 Prithvi 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.
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.
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.
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.