No flight of fancy

The test flight of India’s subsonic cruise missile Nirbhay, which can carry both nuclear and conventional warheads and has a range of 1,000 km, goes exactly as scripted.

Nirbhay, with its wings deployed, a few days before its launch in March 2013.

IT was a flight that far exceeded the expectations of the missile and aeronautical engineers of the Defence Research and Development Organisation (DRDO) on October 17. It was only the second flight of Nirbhay, India’s subsonic cruise missile, which takes off vertically like a missile, jettisons its booster engine and then starts flying horizontally like an aircraft at a subsonic speed of 0.7 Mach.

However, the smooth flight of Nirbhay on that day for more than an hour, covering a range of 1,010 km, demonstrated not only the DRDO’s ability to blend missile and aeronautical technologies into a single contraption but also filled a vital gap in India’s arsenal. While India’s supersonic cruise missile BrahMos has a range of just 290 km, and can carry only a conventional warhead, Nirbhay is a long-range missile that can attack targets 1,000 km away. Besides, it can carry both nuclear and conventional warheads. In addition, it is a “treetop” missile: it can fly at a height of just five metres, undetected by radars. It is a “loitering missile” as well: it can hover above an area for several minutes, pick out a target and attack it with precision. In several DRDO engineers’ reckoning, Nirbhay is the base on which more powerful subsonic cruise missiles with longer ranges can be developed.

The sky was clear at 10-05 a.m. at the Integrated Test Range (ITR) near Balasore, Odisha, when Nirbhay lifted off from a mobile launcher, a TATRA truck. This is the sequence of its test launch: Nirbhay’s booster engine revved up; it rose vertically to a height of 800 metres; a mechanism in the missile tilted it horizontally; the booster engine fell away; the turbo-jet engine, akin to an aircraft’s, ignited; and with its wings spread out Nirbhay started cruising like an aircraft at an altitude of five km. It was carrying a 300-kg dummy warhead. It flew for more than an hour and 10 minutes, traversing more than 1,010 km against the targeted 800 km. It progressed from one waypoint to another, covering 16 waypoints on its flight path. At the end of 1,000 km of flight, with its aviation turbine fuel exhausted, Nirbhay plunged into the Bay of Bengal. All along, a Jaguar fighter-aircraft of the Indian Air Force tailed it, videographing its flight.

Avinash Chander, Scientific Adviser to Defence Minister and Director-General, DRDO, called Nirbhay “a new addition to our weaponry because it can penetrate [areas] where aircraft cannot reach”. Since it can fly at heights varying from five metres to 5 km, “it can go deep into the enemy territory, undetected by radars. It is unstoppable,” said Chander, a missile technologist himself. Nirbhay can attack targets with a precision of one to two metres. In other words, its circular error probability is one to two metres. On October 17, “the missile maintained an accuracy better than 10 metres throughout its path,” said Chander. It performed steep dives too. It was carrying a dummy warhead, “simulating the final warhead”.

In Chander’s estimate, Nirbhay performed better than expected. While DRDO engineers expected it to fly around 800 km, it covered 1,010 km. The DRDO is currently working on its variants, which can be launched from land, ships and submarines so that they can be used by the Army and the Navy.

“It was more than a textbook flight,” said K. Tamilmani, Director General (Aeronautical Systems), DRDO. “This is the base for cruise missile technology which can be adapted for a higher range,” he said. DRDO can build cruise missiles which can attack targets 1,250 km away, he added. He appreciated the private industry’s contribution to the mission’s success. The eight-metre long, surface-to-surface, long-range cruise missile was designed by the Aeronautical Development Establishment (ADE), Bangalore, a DRDO facility.

Only four other countries have long-range subsonic cruise missiles: the United States, Russia, China and Pakistan. Informed sources said that Pakistan’s Babur cruise missile was not a home-grown missile but largely a gift from China. China is now concentrating more on long-range supersonic cruise missiles, informed sources said.

Nirbhay’s performance on October 17 was remarkable compared with its debut flight on March 12, 2013, that ended in failure. On March 12, 2013, after the missile took off vertically, it took a horizontal turn and flew for about 20 minutes, traversing more than 200 km. Soon after, problems arose in a component in its inertial navigation system. So it deviated from its path and started heading towards the Odisha coast. In a written reply to the Rajya Sabha on May 8, 2013, the then Defence Minister A.K. Antony explained what happened after the missile crossed the first waypoint. “Deviation was observed while going to the second way-point. When the deviation exceeded the safety limit, mission abort command was issued from the ground and the destruction mechanism inside the missile was activated.”

The debris fell near Gadaharishpur, Odisha. A Sukhoi-30 aircraft had chased the missile and the Sukhoi pilot said the missile had flown perfectly, as if it was being driven by a pilot till it was destructed, an ADE engineer said later.

“We traced the problem to an electronics component in the inertial navigation system and we redesigned the entire electronics system,” explained the young G. Satheesh Reddy, Director, Research Centre, Imarat (RCI), near Hyderabad, a DRDO laboratory.

Thus, the reliability of this primary navigation system was enhanced. Besides, the RCI introduced a redundant navigation system. “To take care of any failure [of the primary navigation system], we put the redundant system,” Satheesh Reddy explained.

On D-day, after Nirbhay started flying like an aircraft, “it perfectly touched the 16 waypoints as planned and reached the targeted area, more than 1,000 km away,” said Satheesh Reddy. The missile got within five to six metres of the targeted area in the sea. When asked how Nirbhay flew more than 1,000 km while the targeted range was “800 km plus”, he replied: “We keep some margins when we conduct a test flight. We were confident [that we will achieve 1,000 km], but before the test flight, we were a little conservative.” He added that it was definitely the cheapest missile of its class in the world. It cost less than Rs.10 crore.

P.S. Krishnan, former Director, ADE, was delighted over the success of the test flight. “I feel elated because more than 100 per cent of the mission objectives were met. It feels great to achieve such a big success in the second flight itself of a missile of this class,” he said. “The best part of Nirbhay is that we were able to combine the best of two systems, missile and aeronautical, and make a product,” Krishnan said.

What was creditable about the mission was that the DRDO was able to make the missile on its own. “We were able to conceive, design and develop it. It is a totally different situation when we can make our own missiles,” Krishnan said. He also emphasised that Nirbhay can be adapted to be launched from different “sites”, that is, land, ships and submarines.

The RCI’s contribution to the missile were: the primary navigation system called the ring-laser gyro inertial navigation system, the redundant navigation system/ micro-navigation system, the control actuators and battery systems. The Research and Development Establishment (Engineers), Pune, DRDO, specifically designed the mobile launcher. The Advanced Systems Laboratory, DRDO, Hyderabad, contributed the missile’s booster motor.