Agni (missile)

Agni missile system

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:

  1. Agni-I short range ballistic missile, 700- 800  km range,
  2. Agni-II medium range ballistic missile, 2,500  km range,
  3. Agni-III intermediate range ballistic missile, 3,500  km range
  4. There will not be an Agni-IV missile, with DRDO leapfrogging from intermediate range Agni-III to the almost ICBM-like Agni-V.
  5. Agni-V intermediate/intercontinental ballistic missile, ~5,000  km range (in development)

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.

Agni I

Agni-I is a single stage, solid fuel, road and rail mobile, medium-range ballistic missile (MRBM). This shorter ranger missile specially designed for targets in Pakistan. The need for the Agni-I was felt after the Kargil war with Pakistan. It took DRDO 18 months to develop the Agni-I after having completed Agni-II development. It is propelled by solid fuel, giving it a shallow re-entry angle. Maneuvering RV body-lift aerodynamics give it the ability to correct trajectory errors and reduce thermal stresses. The MRV has a velocity correction package to correct launch trajectory variances. Some Agni RV versions use a set of solid fueled thruster cartridges of predetermined impulse, allowing the onboard guidance controller to trim velocity, using discrete combination of impulse quanta along the desired spatial orientation. The 15 metre tall Agni-1 missile, weighing about 12 tonnes, is capable of carrying both conventional as well as nuclear warheads of 1000 kg.

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

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.

Description

The Agni-II was first tested on 11 April 1999 at 9:47 a.m. IST (Indian Standard Time), from a rail carriage, with a carriage roof that slides open to allow the missile to be raised to the vertical for launch by two large hydraulic pistons. The launch process is controlled from a separate railcar. The missile was launched from the IC-4 pad at Wheeler Island, Balasore. Splash down was 2000 - 2100 km. down range in the Bay of Bengal, on a trajectory designed to simulate a range of 2800 - 3000 km. The Agni-II missile can also be launched from a road TEL vehicle, as demonstrated in the second test flight on 17 January 2001, at 10:01 a.m. IST (Indian Standard Time) to a range of 2100 km. This missile has a theoretical maximum range of some 3000 km with a 1000 kg payload (conventional or strategic).

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.

Propulsion

First Stage: The Agni-II's first stage is largely similar to that of Agni-TD's first stage. However, the Agni-II booster is believed to employ more energetic fuel; Booster ISP of 269 (vacuum) and 237 (sea-level). It has a propellant mass of about 9 tons and estimated mass fraction of 0.865.

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.

Manoeuvring Re-Entry Vehicle: Agni RV-Mk.2

The 1980-vintage RV was reportedly designed to be able to carry a BARC-developed, boosted nuclear weapon of 200 KT yield weighing 1000 kg, also of 1980 vintage design. After making room for new and lighter Indian thermonuclear weapon payload, of 1995 vintage design, the MRV has room for about 200 kg (estimated) liquid fuel in pressurized vessels. Although for velocity correction, approximately 50 to 80 kg is estimated to be sufficient. At least one MRV variant type uses a set of solid fuelled cartridges for velocity trimming. The RV is reported to have an attitude control system and aerodynamic manoeuvre fins, presumably to make missile defense more difficult. Unconfirmed reports suggest that an improved optical or radar terminal phase correlation system has been developed to provide accuracy of around 40 meters CEP, although later reports have suggested that the accuracy was around 100 to 200 meters CEP. The RV largely inherits the basic shape, design and technology of the earlier Mk.1 RV of the Agni-TD.

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.

Key Features of the Agni-RV Mk.2

  1. The manoeuvring fins that allows it to;
    • Execute a non-ballistic trajectory to make interception more difficult.
    • Overcome any perturbation due to high altitude atmospheric disturbance.
    • Enable use of body lift at hypersonic velocity to glide the missile over longer ranges, thus reducing the thermal and physical stress at a modified Max-Q point.
    • Trajectory error to be determined late into the flight and corrected using aerodynamic force during re-entry.
    • Terminal manoeuvre dive for a more acute target interdiction angle improving CEP.
    • Support a wider range of payload weight and configuration.
  2. Integrated velocity correction package for greater precision; has a set of solid fuelled cartridge(s) that are used to correct impulse variances of solid fuelled stages and subtle launch trajectory perturbation.
  3. Integrated High Altitude Motor (HAM) which is liquid fuelled. Depending on the actual payload configuration, the HAM fuel load can be increased to trade range for a lighter and more compact weapon.
  4. Larger internal volume allows more sophisticated ABM (anti-ballistic missile) counter-measures.

Avionics, Navigation and Control

The Agni family of missiles uses a strap-down INS system for flight control and navigation. Necessary inertial sensors were indigenously developed for the purpose, including laser rate gyros.

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 [42]. 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.

Accuracy

The Agni-II's navigation and aiming uses an advanced ground based beacon system using a TDOA (Time Delay Of Arrival) technique, similar to a GPS system, that constantly provides missile flight position and velocity updates and has been proven in test flights. The TDOA system reportedly improved the accuracy by three times. India has demonstrated a measure of mastery in navigation sensors and flight control through its space program. The placement accuracy in GTO (involving powered flight of 1000 seconds much of it in sub-G or gravity free environment) is far more complicated and delicate than that of the sub-orbital trajectory of an IRBM. Thus the GSLV-D2 and F01 GTO Apogee accuracy of 1965 PPM and 361 PPM respectively that compares with Agni-II's 40 meter CEP at IRBM ranges with 13 PPM accuracy.

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:

  1. Small velocity correction thruster package and/or
  2. Aerodynamic manoeuvring during re-entry (this requires active RV configuration with integrated INS and control system).

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:

  1. Accuracy of determining geographic coordinate of target and launcher.
  2. Accuracy of hitting the designated coordinates that is determined by missile's navigation and control system.

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.

Range

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.

Conclusion

As the backbone of the Indian land-based nuclear deterrent, the real significance of the Agni-II is the fact that it is both road and rail mobile. This is an indication of India's desire not to put its missiles into vulnerable silos. The mobility of the Agni-II, combined with the sheer physical size of India renders the mobile IRBM a very secure and survivable delivery system. Its range of strategic weapons payload and good accuracy make this strategic weapon useful for counter value as well as first strike role.

Agni III


Agni III an intermediate-range ballistic missile was developed by India as the successor to Agni-II. Designed by the Indian government's Defence Research and Development Organisation, Agni III is intended to be a two-stage ballistic missile that is capable of nuclear weapons delivery. 

Agni III is expected to be India's nuclear deterrent against People's Republic of China.

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.

Propulsion

The Agni-III features two solid fuelled stages and with overall diameter of 2.0 meters. This diameter is compatible with a recently tested Indian sub-surface launch system, which has a 2.3 meter diameter launch tube aperture.
First stage booster
The first stage booster is made of advanced carbon composite materials to provide high mass fraction. It weighs about 32 tonnes, is 7.7 meters long and diameter of 2 meter. The Isp is comparable to similar large solid motor of ISRO.
Second stage
The second stage made of maraging steel weighing about 11 tonnes and a length of 3.3 meters. The second stage has flex nozzles, to provide necessary flight trajectory control.

Maneuvering re-entry vehicle: Agni RV-Mk.4

Agni-III supports a wide range of weapons, with total payload weight ranging from ~600 kg to 1,800 kg including decoys and other ABM countermeasures. Instead of conventional bus architecture, the RV (Re-Entry Vehicle) is self-contained with velocity correction package, navigation and re-entry control systems. Lighter and tougher RV body with all carbon composite re-entry heat shield with multi directional carbon re-entry nose tip and control surfaces, the new lightweight composites can withstand temperatures of up to 6000 degrees Celsius, and capable of greater re-entry velocity. The all composite RV has no metal backup.

Flight tests

The first test for Agni III was conducted from Wheelers Island off the Bhadrak coast on July 9, 2006. The launch proved to be unsuccessful with the missile falling into the sea off the coast of Orissa, short of reaching the target. According to DRDO, the failure was due to a first stage anomaly that was caused by recirculating hot gases entering the missile-base shroud and damaging the electronic components. Indian Defence Minister Pranab Mukherjee reported it as "partial success" (a trade euphemism to indicate the test generated useful data for diagnosis and correction) as the missile was air-borne for only 5 minutes instead of the expected 15 minutes.

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.

Agni-III SLBM

DRDO is working on a Submarine Launched Version of the Agni-III missile, which will provide India with a credible sea based second strike capability. The SLBM version is a miniaturized version of the Agni-III which is expected to be test fired shortly.

Agni V

According to one of the country's top defence scientists, Dr M Natrajan, DRDO scientists are working on an upgraded version of the Agni III known as the Agni-V (Earlier known as Agni-III* (Agni-III star) and Agni-IV). The missile will have a range of about 5000-6000 km and the first test flight is expected in 2010 end.

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.

See also

References

External links

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