Section: Ballistic Missiles; Updated on: December 13, 2008;
Special Thanks to Frontline and India Today
The Agni (Fire) is an Intermediate Range Ballistic Missile which had begun development in 1979. It became part of India’s Integrated Guided Missile Development Program (IGMDP) in 1983. The first Agni test occurred on 22 May 1989, and two more tests were conducted on 29 May 1992 and 19 February 1994. These tests were technology test-beds (TTBs) for developing vehicle structure, integration, navigation and control, flight dynamics and re-entry vehicle technology. The TTBs achieved a maximum range of 1500 km, however the main drawback was the missile’s solid-liquid propulsion configuration, which seemed unsuitable for an operational IRBM. Thus the Agni-II was developed, which had a length of 20 metres, a diameter of 1.3 metres and weighs 16 tonnes, and is an improvement over its predecessor which had a length of 21 metres and weighed 19 tonnes.
The first prototype of an operational variant, the Agni-II, was tested on 11 April 1999 at 9:47 a.m. IST (Indian Standard Time). The missile was tested to a range of ~2100 km, taking 11 minutes to reach target and was a perfect textbook launch. This first test of Agni-II occurred exactly 11 months after India’s nuclear tests on 11 May 1998. A second Agni-II test occurred on 17 January 2001 at 10:01 a.m. IST (Indian Standard Time) and was tested to a range greater than 2100 km. After the second test, Agni’s Program Director - Professor P.N. Aggarwal - said, “The flight test results have indicated that mission objectives were met satisfactorily.” Although this was the second Agni-II test, it was for the first time that the missile was test-fired in its final configuration. Reportedly, the focus of the test was to observe the accuracy at an increased range. An official, connected with the Agni-II program said, “The re-entry control and guidance technology have already been tested, but accuracy at increased ranges was to be tested.” A maximum range of 3000 km can be achieved, using specific payloads.
Test flight of the Agni TTB
Test flight of the Agni-II
Both stages of the Agni-II have a solid propulsion system, which allows the missile to be mobile and flexible. This was confirmed, as the test which was conducted on 11 April 1999, was a rail-based missile launcher. The solid-fuel motor in the first stage of Agni-II, is similar to the first stage in the technology test-bed, itself based on the SLV-3 Space Launch Vehicle. However the solid-fuel motor in the second stage of Agni-II, has been reportedly designed anew for the missile. For manoeuvrability and thrust control, the second stage has a flex nozzle which enables small changes in the thrust vector direction in flight. The flex nozzle can be exploited with the help of an on-board closed-loop guidance & control system. Till now, the flex nozzle has been used only in the third-stage motor of the PSLV. At a range of 2000+ km, Agni-II has an apogee (the farthest point from earth) of 405 km, a re-entry speed of 3.9 km/second and a boost phase of 110 seconds. The re-entry vehicle uses its manoeuvring fins to porpoise the warhead, to avoid missile defenses while manoeuvring to its target, employing a terminal guidance radar operating in the C- and S-bands.
The then-incumbent Scientific Advisor to the Government and DRDO Chief, Dr. Abdul Kalam, has said that what is unique about the Agni-II is the trajectory shaping and guidance that is possible through software. Agni-II, has appropriate on-board thrusters fitted on the second stage of the missile. This is because solid fuel is allowed to burn completely, which means that the velocity increment achieved before re-entry could be more or less from the mission perspective. Further, there is considerable dispersion or variation in the burn and thrust time of solid fuels. Any compensation that is given to the missile during its ballistic phase (which happens once the second stage is fully burnt out) should be based on the on-board sensor data and should be amenable to being adjusted reactively. These on-board thrusters are driven by liquid-fuel and provide small increments in the appropriate directions to shape the trajectory depending upon the target of the mission. It is these thrusters that give the manoeuvrability during the missile’s re-entry phase. This has apparently been optimised through on-board software which, based on the initial trajectory fed in, does an appropriate velocity trimming. In effect this is a hot gas active velocity correction system.
Agni-II, on a road-mobile launcher, at the 1999 and 2000 Republic Day Parades
Agni’s Project Director, Avinash Chander, said the effort to operationalise the missile system was complex, as it involved reducing the host of computer’s processing information, both inside the missile and ground control systems, to a single control system. To ensure greater reliability of the missile, they reduced the mass of over 600 different sets of communications channels, involving 24 km of cabling, to just 10 pairs requiring one-eighth of the original wiring. A new concept has been adopted for the on-board navigation system, which is the 1553 Data Bus. It is the standard that is adopted in civilian aircraft (circuit routing and device mounting) and all the software in the Agni-II has been designed around this bus. DRDO sources claim that this reduces the number of connectivities and also making the missile a little more rugged. However, certain missile analysts feel that a standard bus may not be the best path to follow. They say that a customised bus is better because in a standard bus, one tends to use off-the-shelf electronic devices whose performance may not be optimal. However most modern missiles are moving towards digital buses using commercial off-the-shelf technology and which enables affordable sub-system replacement. A customized bus would lead to more delays and increased costs which should be avoided to prevent needless expenditure.
Another major feature in terms of operational configuration is that Agni-II is designed to be launched from a rail-mobile launcher; one that can move on a standard broad-gauge rail system. The technology test-beds, however, had been designed as a road-mobile system. There are pluses and minuses to this change. A rail- and/or road-based missile system reduces vulnerability and allows for greater operational flexibility, while critics feel that the cost of these mobile systems could be higher and that they greatly increase the time for moving from one place to another. Considering that except in some parts - for instance, India’s north-eastern region - road infrastructure is available wherever rail tracks are available, the decision to become rail-mobile could mean, in strategic terms, that deployment in India’s north-eastern region is to be considered a serious possibility. Assuming that Agni-II is to be deployed in India’s north-eastern region and even given a 2,000+ km range, Agni-II can still not reach vast parts of China - including Beijing, which is over 3000 km away. Therefore, a longer-range Agni variant may well be required if the need for a deterrent against China is being seriously felt.
Agni-II’s various flight stages
Agni-II on the launch pad
While a new and longer-range system can certainly be developed if the Services require it, the present configuration is in operational mode, says Dr. Kalam. Range, he adds, could be optimised by appropriately configuring the payload mass. According to him, a road mobile version would also be available and it would be then left to the Services to choose according to their operational convenience. He also says that additional tests are not needed to operationalise the Agni-II. This indicates that the re-entry vehicle has been rigorously tested in its previous flights over all the dynamic parameters and is qualified. If inducted, Agni-II will reportedly always be in a ready-to-fire mode and can be launched within 15 minutes as compared to almost half a day of preparation for the technology test-beds. A longer-range version, designated Agni-III, is being planned and K. Santhanam - former RAW officer, DRDO technical advisor, nuclear scientist and presently IDSA Director - stated that Agni-III is indeed in the developmental stage. The missile will be rail-mobile, with a range of 3,500 - 4,000 km and a first test may occur in 2003.
Reports of the missile having a GPS (Global Positioning System) is not true, as Dr. Kalam has said, and adding that it depends on several external influencing factors and this would make the system vulnerable to external interference. However, many tactical missiles the world over do use GPS systems. DRDO officials say that the use of GPS had been considered for Agni-II at some point of time. It is possible that, GPS augmented mode could be used for conventional versions to increase accuracy. A Japanese newspaper report stated that Agni-II achieved a Circular Error Probable of 40 metres. This however, has yet to be confirmed from reliable sources. If true, it certainly is an improvement since the technology test-beds reportedly had a CEP of ±100 metres. DRDO’s Chief Controller of R&D (Missiles), Dr. A.S. Pillai, stated after the Agni-II test, “We have improved accuracy by a factor of at least three. It is a far more lethal missile now.” He also said that the missile would have a unique on-board energy management system and an on-flight guidance process using navigational sensor technology.
The rail-mobile Agni-II being wheeled out of a hangar
The road mobile Agni-II in front of India Gate at New Delhi
Dr. Kalam, said that the complete re-entry hypersonic flow was simulated in the Computational Fluid Dynamics, on a super-computer. Import content in the Agni-II is less than 10%, as stated by Dr. Kalam. Cost estimates for the Agni-II vary and are subject to change depending on the number produced. Many conventional warheads have been developed for use with the strategic missile, everything from bomblets to guided munitions to even fuel air explosives. The low CEP is thus needed for the conventional mission. The most important warhead the Agni-II is designed to and will carry is a one-tonne nuclear device, using a thermonuclear design, which was tested successfully on 11 May 1998. Dr. Kalam confirmed that nuclear warheads can be fitted on the Agni-II in April 1999.
Although the Indian Government denies that the Agni-II will be nuclear-armed, many Indian analysts point out, that the missile costs too much to develop for just delivering conventional payloads. Reportedly Bharat Dynamics Limited (BDL), Hyderabdad, is planning to manufacture 10 to 12 Agni-IIs annually. In May 2001, and again in July 2001, the then-incumbent Defence Minister Jaswant Singh informed the Cabinet Committee on Security (CCS) that the Agni-II is operational, limited production had begun and induction being planned during 2001-2002. On 14 March 2002, Defence Minister George Fernandes informed Indian Parliament that the Agni-II has entered the production phase and is under induction.