The Agni missile (Sanskrit: अग्नि, Agnī "Fire") is a family of Short to Intermediate range ballistic missiles developed by India under the Integrated Guided Missile Development Program. As of 2008, the Agni missile family comprises three deployed variants:
Agni-I was first tested at the Interim Test Range in Chandipur in 1989, and is capable of carrying a conventional payload of 1000 kg (2,200 lb) or a nuclear warhead. Agni missiles consist of one (short range) or two stages (intermediate range). These are rail and road mobile and powered by solid propellants.
The Agni I has a range of 700-800 km while the Agni-II as a range of 2,000–2,500 km. They are claimed to be a part of the "credible deterrence" against China and Pakistan. The Agni-II can only reach most parts of western, central and southern China. With the successful test of Agni-III which has a range of 3500 km, it falls within the reach of most major Chinese cities, including Beijing and Shanghai. Agni-III is the third in the Agni series of missiles. Agni-III was tested on July 9, 2006 from Wheeler island off the coast of the eastern state of Orissa. After the launch, it was reported that the second stage of the rocket had failed to separate and the missile had fallen well short of its target. Agni-III was again tested on April 12, 2007, this time successfully, from the Wheeler Island off the coast of Orissa.On May 7, 2008 India again successfully test fired this missile. This was the third consecutive test; it validated the missile's operational readiness while extending the reach of India's nuclear deterrent to most high-value targets of the nation's most likely adversaries.
It has been reported that the missile's Circular Error Probable (CEP) lies in the range of 40 meters, which, if confirmed, would make the Agni-III one of the most accurate strategic ballistic missile of its range class in the world. This is of special significance because a highly accurate ballistic missile increases the "kill efficiency" of the weapon; it allows Indian weapons designers to use smaller yield nuclear warheads (200 Kiloton thermonuclear or boosted fission) while increase the lethality of the strike. This permits India to deploy a much larger nuclear force using less fissile/fusion material (Plutonium/Lithium Deuteride) than other Asian nuclear powers. Older, less accurate ballistic missiles, such as those deployed by earlier nuclear powers require larger yield (1-2 Megaton) warheads to achieve the same level of lethality. It has also been reported that with smaller payloads, the Agni-II can hit strategic targets well beyond 3500 km.
In May 2008 Indian scientists announced they had developed and patented a path-breaking technology increases the range of missiles and satellite launch vehicles by at least 40%. The enhanced range is made possible by adding a special-purpose coating of chromium based material to a rocket's blunt nose cone. The material acts as a reactive-ablative coating that forms a thin low density gaseous layer at the tip of the rocket as it approaches hypersonic speeds; this super-heated gas layer reduces drag by 47% (at mach 7-8), thereby allowing range enhancements at least 40%. It has been announced that this technology will be incorporated in future Agni deployments after having undergone ranging and calibration tests. These same scientists who developed this new material also intend continue development to create materials that will generate a plasma shield envelope around launch vehicles, to further reduce drag.
On October 5, 2007, a nuclear-capable Agni I was test fired from Wheelers' Island, a defense base in the Bay of Bengal on Orissa coast at Bhadrak, Orissa; and again on March 23, 2008 from the same site.
Agni-II, providing a breadth of payload and range capabilities. The Agni-I is a short range ballistic missile (SRBM) with a single stage engine. While the Agni-II is an intermediate range ballistic missile (IRBM) with two solid fuel stages and a Post Boost Vehicle (PBV) integrated into the missile's Re-entry Vehicle (RV). The Agni's manoeuvring RV is made of a carbon-carbon composite material that is light and able to sustain high thermal stresses of re-entry, in a variety of trajectories. The Agni-IIAT is a more advanced version of Agni-II, albeit with more sophisticated and lighter materials, yielding a better range and operating regime.
Quick deployment of the Agni-II was possible, by building on the earlier Agni-TD program that provided proven critical technologies and designs required for long range ballistic missiles. Thus when the decision was made to build the Agni weapon system, some quick optimization and ruggedization was done to the basic '1980 vintage' design, including a solid fuelled second stage. Further the solid fuel chemistry, RV and avionics were brought up to state-of-the-art levels. As the Pokhran-II (POK-II) nuclear test proved a family of more powerful and lighter nuclear weapons, the 200 KT thermonuclear weapon is far lighter compared to 1000 kg earlier budgeted for the 200 KT boosted nuclear weapon. Thus a high yield weapon configuration now assumes a payload of 500 kg, including weapon and RV. However, in the interest of rapid development the basic design that was earlier developed continued to be used and keeping the future options open, for more optimized missile design and lighter payload. The Agni-II missile will be used by 555th Missile Group of the Indian Army.
Tested to range of over 2000 km, the Agni-II has an all-solid propellant system. After the January 17th test, the missile was cleared for production and it is possible that a production capacity (under-utilised at present) exists for 12 Agni-II missiles per year. On the January 17th test, the missile was alleged to have covered a range of over 2100 km with a 700 kg warhead. The Agni-II is designed to be launched from a rail-mobile launcher, it is also available in road-mobile configuration. This lends flexibility and reduces vulnerability to first strike.
The Agni-II will 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 previous generation Agni-TD. 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 missile 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. Agni-II is made by BDL in Hyderabad, with a production capacity of 18 missiles/year and costs about Rs.35 crore for each missile.
Second Stage: The Agni-II's second stage weighs ~4200 kg and uses solid fuel propellant. Its case is presumably made of the same material, high-strength 15CDV6 steel, as the booster stage for ease of manufacturing. This solid propellant stage has flex nozzles for thrust vectoring, for precise trajectory control. Unlike the Agni-TD, the solid fuel second stage does not require retro motors for proper stage separation. It uses a vented inter-stage.
Agni is unlike the first generation long-range missiles developed by west where the RV was a passive ballistic load, whose accuracy depends on the launching vehicle's exact insertion into the sub-orbital trajectory. A large inaccuracy associated with the Indian and western first generation RVs, involved spinning the RV for greater stability during re-entry. Second generation western missiles were mostly MIRV (Multiple Independently targetable Re-entry Vehicle) and the accuracy was greatly improved by the payload bus with HAM velocity correction package for more accurate sub-orbit insertion. It also allowed individual MIRV payloads to impart different velocities, so that each can be independently targeted to a different target, albeit in the vicinity of each other. The Agni-RV Mk.2 is an improvement over the first generation RVs, because it embodies proposition, navigation and control all the way to the target. The RV re-enters at an altitude of 100 km, at a shallow angle, with a gliding trajectory .However it does not carry a MIRV payload.
Agni-II introduced a new concept in missile control system by adopting MIL-STD-1553 databus for all on-board communication and control device interconnection --> mainly INS system, Flight Control Computer, actuators and sensors . It is the standard that is adopted in new civilian & military 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 connections and also makes the missile more rugged. However, some missile analysts feel that a standard databus may not be the best path to follow. It is said that a customized databus is better because in a standard databus, one tends to use off-the-shelf electronic devices whose performance may not be optimal. However, most new missiles are moving towards digital buses using commercial off-the-shelf technology and which enables affordable sub-system replacement.
It is worthwhile to note that INS error differs for a ballistic missile versus an aircraft. Ballistic missile accuracy is only dependent on the INS accuracy up to the point when rocket fuel is expended (100 seconds for Agni-II) and it exits the atmosphere (> 90 km altitude), after that the trajectory is purely ballistic that is predetermined and easily computed. INS in a combat aircraft requires continuous operation of IMU and navigation computer throughout the flight during which the error keeps building as IMU sensors drift. A ballistic missile that can update its position and velocity from auxiliary means, can completely eliminate the built up error from INS and continue flight at a precise predetermined path, if necessary correcting the launch error by using:
The Agni-II missile reportedly makes use of both the above techniques. The Agni-II exits atmosphere and expends the second stage at an altitude of 120 km and at a distance of about 150 km. This allows the ground based TDOA system to operate well within Indian Territory and at close range (i.e. robustness against Electronic Warfare interference). The missile maintains LOS (line of sight) well beyond apogee. The overall accuracy is the cumulated sum of:
Launching the Agni from a surveyed site is one aspect of item 1 above. The sub-meter target coordinates, using national surveillance assets, (aerospace, sensors, etc) would largely address the accuracy of target coordinate designation. A long-range ballistic missile (passive RV) targeting error is typically spread in a highly elliptic pattern. The CEP is thus adversely biased by a wide error spread in a longitudinal axis (due to shallow incidence angle). The Agni's active manoeuvring RV with onboard IMU (INS) and control system can perform terminal manoeuvre to correct errors and make a more accurate top attack profile using greater incidence angle significantly reducing the longitudinal spread and overall CEP.
The range of a missile is greatly influenced by use or non-use of thrusters on the RV (required for velocity trimming) for propulsion as a HAM (High Altitude Motor). There seems to be room in the RV for about ~200 kg fuel (solid or liquid) after allowing for a long but lightweight TN weapon. This RV integrated HAM is referred to as the half stage after the two solid fuelled stages. This stage provides a disproportional increase in range for a lighter RV payload. Thus development of lightweight nuclear weapons is paramount to the missile's range.
When the Agni-II was first launched, then Defence Minster George Fernandes indicated that the maximum range of the Agni-II was 3000 km. Since then, ranges from 2000 km to 2500 km have been bandied about while Dr. Kalam, at Aero India '98, stated that Agni-II had a maximum range of 3,700 km The range of 2000 km can be excluded, as the system has been tested to greater range in both 1999 and 2001. Given the test to 2300 km in 1999 and 2100 km in 2001, with an apparently lighter payload, would indicate that a variation in trajectory was used and it may be possible to extrapolate some more accurate estimates of Agni-II's maximum range.
It would appear that Agni-II has a theoretical ability to hit a target 3000 km away with a 1000 kg overall payload – (a 250 kg RV's deadweight and a 750 kg warhead). It is suggested that a 200 kiloton 'boosted fission' warhead was earlier developed for the Agni system when it was on the drawing board in the late 80s, however after the Pokhran-II series of nuclear test in May 1998, the 200 KT boosted fission design has clearly given way to a 200 - 300 KT two stage thermonuclear design that is expected to be much lighter. From the tables at Effect of payload and stage configuration on Agni-II range, one can see that a number of permutations and combinations are available to DRDO based on the existing Agni-II design and Indian propulsion technology. Range changes can be made by either varying the payload or by altering the engine configuration.
Given the available data, it is therefore clear that Agni-II has a maximum range of somewhere in excess of 3000 km, and possibly as high as 3500 km with a 1000 kg payload. Greater range with a lighter payload however requires the RV to be qualified for higher re-entry velocity and corresponding Max-Q for thermal stress.
The Agni-III has two stages with an overall diameter of 2.0 m. The first stage mass is about 32 tonnes and 7.7 m long, the second stage mass is about 10 tonnes and 3.3 m long. The missile is likely to support a wide range of warhead configurations, with a 3,500 km range and a total payload weight of 2490 kg. The stubby two-stage solid fuel missile is compact and small enough for easy mobility and flexible deployment on various surface/sub-surface platforms.
Agni-III was test fired again on April 12, 2007 from the Wheeler Island off the coast of Orissa. This time, the launch was declared as a success. India's Cabinet Committee on Security announced that "This test confirms the extent of India's nuclear reach and India's nuclear deterrence as the missile can accurately hit targets at distance more than 3000 km away". Already the most powerful and capable in India's missile inventory, the Agni-III is capable of carrying a variety of warheads, including nuclear warheads and can be launched from various platforms giving India intermediate range ballistic missile firepower and greatly extending India's power projection in the region.
Agni III was test fired successfully for third time on May 7, 2008. The missile was launched from Balasore, Orissa. After a flight of roughly 15 minutes defense scientists confirmed that the test fire was successful and that the missile met all parameters. The missile has a velocity of 5,000 meters per second. Agni-III is a nuclear capable fully solid propellant fueled surface-to-surface missile, and has a range of 3,500 km. A new software for navigation system fitted on the missile, will increase accuracy and lethality.
The Successful test on May 7, will open door for next generation Indian Inter Intermediate-Range Ballistic Missile Agni-IV which will have firing range over 6,000 kilometer.
The Agni-V is a three stage solid fueled missile with composite motor casing in the third stage. Two stages of this missile will be made of composite material. Agni-V will be able to carry multiple warheads and will have countermeasures against Anti-ballistic missile systems.