Image Courtesy: Hindustan Times
Article 9/2024
Introduction
It was a stunning announcement from the Prime Minister of India on March 11, 2024, when he said that Agni-V has been tested successfully with Multiple Independently Targetable Re-entry Vehicles (MIRV) as ‘Mission Divyastra’. A release by the Ministry of Defence simply said, “The Mission accomplished the designed parameters”. Since the time a NOTAM was issued on March 7 for a 3550-Km range missile test from the Odisha coast anytime between 11th and 16th March, there had been speculation about what kind of missile it could be. It could have been the regular missile testing by the DRDO or the Strategic Forces Command (SFC). There was also speculation, and perhaps hope, that it could be a submarine launched ballistic missile (SLBM), like K-5 or even K-6.
The curiosity peaked when it was learnt that the Chinese ‘research vessels’ were lurking around near the NOTAM area, at mid-way as well as at the terminal points. The PLAN sent its ‘research’ vessel Xiang Yang Hong 01 (XYH-01) to a position in the Bay of Bengal right below the intended trajectory of the missile. It had also positioned its other ‘research vessel’ Xiang Yang Hong 03 (XYH-03) almost near the end point of the test range. Of late, the Chinese have tracked many Indian missile tests under the guise of doing ocean-research in the Indian Ocean Region (IOR) in the Exclusive Economic Zones (EEZs) of either Sri Lanka or the Maldives. The Xiang Yong Hong 03 was allowed to dock at Male port on February 8 following the visit of the Maldivian President Muizzu to China. It left the port on February 28, but it did not travel much, lurking instead about 300 nm southeast of Male and doing the usual ‘survey pattern’. On many occasions earlier, this vessel has been known to operate with its Automatic Identification System (AIS) turned off, therefore raising concern about its actual activities. Though this vessel, along with XYH-01, is classified as ‘hydrographic survey vessel’, unlike the ‘missile tracking’ instrumented ships like PLAN’s Yuan Wang series, it is likely to have signal and optical intelligence (SIGINT) capability. The Chinese are used to masquerading their assets in various forms in order to avoid detection. We have seen their survey ships masquerading as fishing vessels. In November 2022, when India tested its ballistic missile defence (BMD) AD-1 missile, Yuan Wang-05 was located in China-leased and operated Hambantota port in August 2022 and was later found loitering in the IOR when DRDO conducted its AD-1 endo-atmospheric missile test.
Agni-V
The Indian missile program which has its genesis in the Integrated Guided Missiles Development Program (IGMDP) which was launched in c. 1983 with the intention of developing and operationalizing Surface-to-Surface SRBMs/IRBMs and MRBMs (Prithvi and Agni-series), anti-tank missiles (Nag) and short-range and Medium-range surface-to-air missiles (Trishul and Akash) concluded in c. 2008 by which time many of these missiles had either been realized or were well on their way to realization. Further developments have led to supersonic cruise missiles for land and sea attacks (BrahMos), submarine-launched ballistic missiles (K15, K4), ballistic missile defence (BMD) missiles (AD-1, AD-2), anti-satellite missiles (ASAT), artillery rockets (Pinaka) etc.
The longest-range missile in India’s missile armoury today is the Agni-V. This is a strategic missile which will carry only nuclear warheads, leaving no scope for confusion in enemy minds. When a dual-use missile is fired, that is a missile which can carry conventional as well as nuclear warheads, the enemy can mistake the incoming conventional missile as a strategic missile and react with a nuclear strike leading to unintended catastrophe. It is for this reason that India discarded the dual-use Prithvi-I SRBM. While Agni-V’s range and throw-weight are classified, open-source intelligence indicates that this three-stage solid-propellant, road-mobile and cannisterized missile has a range in excess of 7000 Kms and can carry a payload of 1.5 tonnes. The road-mobility is achieved through a Transporter-Erector-Launcher (TEL) which consists of a three-axle tractor pulling a seven-axle trailer carrying the cannisterized weapon and the launcher. The hermetically sealed cannister preserves the integrity of the weapon, enables easy movement and a quick launch. A gas generator at the bottom of the launcher ejects the 50-Tonne missile in a matter of a few seconds out of the cannister. It is believed that Agni-V has a Circular Error Probable (CEP, which is a measure of the accuracy of the missile) of 40 metres at full range. This means that at least 50% of the time Agni-V would impact within a circle of radius 40m of the target after travelling the full range. It has been stated that it has always performed better than that. One of the top DRDO officials associated then with Agni-V is on record saying that the test resulted in a “pinpoint, single-digit accuracy”.
Agni-V takes its first stage from Agni-III, with a modified Agni-III second stage and a miniaturized third stage to ensure long ranges. The 2nd & 3rd stage rocket motor casing is made entirely of carbon-filament wound composite - carbon fiber reinforced polymer (CFRP) while the first stage was of maraging steel, which was also converted to CFRP by c. 2022 which helped in reducing the weight of the missile and thereby increasing the range and/or throw-weight. In a TV interview, a defence official had stated that the range was in excess of 7000 Kms, thus making Agni-V an Inter-Continental Ballistic Missile (ICBM)-class of missiles. Since there is scope for further reduction in weight, we can only expect more range and payload capacity for Agni-V. The SFC did the first firing after induction on October 27, 2021, which was also a night trial. The December 15, 2022, test by SFC was after weight reduction of the first stage and the missile was tested up to a range of 5400 Kms from Odisha. In the initial configuration, up until the latest test, the third stage was conical and carried a single warhead.
There are three stages of flight regime for a Ballistic missile, the initial boost phase, the mid-course phase and the terminal phase. During the boost-phase which largely takes place within the atmosphere, an ICBM can reach typically 24000 Kms/ Hr. (~20 Mach). Such missiles cannot still attain earth orbit because at that altitude the velocity needed would be ~7.7 Kms/sec (~27,000 Kms/Hr.) and so they would eventually fall to earth following a ballistic trajectory (a free fall under gravitational pull). During the mid-course phase, the rocket is no longer firing, and the stages have separated leaving the delivery-platform (called ‘bus’ or ‘post-boost vehicle’, PBV) to fly unpowered. The nose cone covering the bus would fall-off exposing the RV(s). While the bus may still be ascending during the initial part of the mid-course phase, its maneuver’s itself precisely by adjusting its attitude (by firing small vernier rockets embedded around the bus) and velocity and begins a ballistic free-fall at the apogee (the highest point reached). The warhead (RV) is separated at this point, after the bus has ‘aimed’ it at the target. Typical of ballistic missiles, an Agni-V would release a re-entry vehicle (RV) carrying the warhead after the apogee by which time it is estimated that Agni-V had reached 600 Kms altitude. The RV would be released in a trajectory chosen to hit a pre-determined target. Since Earth’s atmosphere starts around an altitude of 100 Kms (Karman Line), the RV needs to be protected against aerothermodynamic heating using a thermal protection system so that the RV does not burn-up in the atmosphere. Once the RV of an ICBM enters the atmosphere, it would hardly take a minute for it to hit the target because of its tremendous velocity of about 5 Kms/Sec. At that stage, it is almost impossible to destroy it through ballistic missile defense (BMD) systems because of two reasons, a very limited window of opportunity and high velocity. That is why the best course of action for BMD systems is to attempt a kill in mid-course or in boost phase or left-of-launch which attempts to eliminate the missile threat before it is even launched.
In earlier generations of ICBMs, the aiming of the target was done during the boost phase when ‘thrust vector control’ of the stages can be utilized to accurately align with the target. However, the dynamic load on the RV by the atmosphere and other disturbances such as errors in the inertial navigation system (INS) can deviate the warhead from the target thereby increasing the CEP or in other words, reducing the accuracy of the missile. Nowadays, normally, single warheads use a Maneuverable Re-entry Vehicle (MaRV) in which the angle at which the RV enters the atmosphere is made shallow thereby letting the RV glide along the edge of the atmosphere, controlled by actuating surfaces such as fins on the body of the RV. This can be used to enhance the range of the missile, evade the BMDs and also increase accuracy. The earlier version of Agni-V used MaRV warheads. This could still be used for a single warhead situation involving bigger nuclear warheads.
MIRV has been implemented in ICBMs for several decades now. In this case, the bus carries multiple RVs, each one of which can be made to hit a different target or even the same ‘hardened’ target repeatedly, at the terminal point. However, the targets will be within the ‘ground track’ of the ICBM, separated by a few hundred kilometres, at the most. The ‘bus’ (or the post boost phase vehicle) repositions itself accurately before releasing each RV of the MIRV. This technique is exactly similar to launching multiple satellites from a single rocket. MIRV has an economical advantage as a single missile launch is enough to hit multiple targets, besides overwhelming the BMD systems of the enemy and thereby ensuring the probable success of a nuclear strike. Besides, the accuracy of the missile warhead is considerably enhanced leading to implementation of counterforce deterrence, rather than a countervalue deterrence provided by ICBMs with higher CEPs. It is such countervalue weapons that prompted Chairman Mao to famously say, "What if they killed 300 million of us? We would still have many people left." Modern warfare has moved to targeting militarily, politically and economically significant targets precisely without much collateral damage. The successful implementation of MIRV in Agni-V therefore raises the deterrence value of our nuclear arsenal. Besides actual warheads, a MIRV bus would also carry some decoys in order to confuse the enemy BMD systems. The decoys will behave almost exactly like the RVs and confuse the enemy radar systems and BMDs in such a way that their wrong choice to intercept the decoys would allow some nuclear warheads to penetrate and hit the targets.
The MIRV capability of DRDO has not come as a surprise because India has been launching multiple satellites into accurate orbit with a single rocket, for a decade now. Though there are some differences, the technology barrier had been overcome a long time back. Many believe that the ‘system on chip (SOC)’ which was tested during the multi-satellite PSLV launch on 25 February 2013 is a precursor for MIRV capability. After the successful first user test by the SFC, a DRDO official said, “The high speed on board computer [ system on chip (SOC) based on-board computer (OBC) ] and fault tolerant software along with robust and reliable bus guided the missile flawlessly” . Another successful test was conducted on June 3, 2018. On December 10, 2018, a successful test of a cannisterized (also known as a ‘wooden round’) Agni-V from a road-mobile launcher was carried out.
It therefore looked likely that MIRV implementation on an active missile was only a political decision to make. The decision by China to increase massively its MIRVd silo-based DF-41/DF-51 missiles probably hastened our decision. As early as c. 2012, China had tested its MIRV-capable (maximum 10 warheads) DF-41 missile of 14000 Km range. In early 2021, amidst raging Wuhan China Coronavirus pandemic, China started building 119 missile silos [with another 26 DF-41 silos already in place] across more than 700 square miles in the Gansu desert (Gobi Desert). Later, another site for 110 silos was detected in the city of Hami (over an area of 800 Sq. KMs) in Eastern Xinjiang. There are also 12 silos at Jilantai, Inner Mongolia, ostensibly for training purposes. They also have 20 silos for liquid-fuelled DF-5 ICBMs. It is expected that the Chinese arsenal would triple to over 1000 nuclear weapons by c. 2030.
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A former DRDO official estimated the number of warheads in the Agni-V MIRV test to be three, though Agni-V can carry a greater number of RVs. When the number of RVs increases, the range would reduce. The number of RVs that Agni-V can carry also depends upon the type of nuclear warhead it would carry. There are essentially three types of weapons in the Indian arsenal for strategic purposes, simple fission weapon, fusion-boosted fission (FBF) weapon and fusion weapon (also known as thermonuclear (TN) or Hydrogen-bomb). Various estimates indicate that the simple fission device would weigh about 250 Kg for a yield of 100 KTs (Kilo tonnes of TNT) while the weight of a fusion-boosted fission device with a yield of 250 KT could be approximately 500 Kg. and a TN weapon could weigh as high as 1T. We can see that the conical nose of the earlier Agni-V has given way to a more cylindrical shape in the latest test in order to accommodate the MIRVs.
Strategic Implications
The MIRV test has deep strategic implications. Firstly, the deterrence posture of India is verifiably raised to counterforce-level while we continue to stick with the ‘No First Use’ (NFU) doctrine. Thus, today we are at the same technological level as the other P-5 members though we are only a de facto nuclear weapon state (NWS) yet. The MIRV adds muscle to our NFU doctrine which assures ‘massive retaliation’ if attacked. The ‘credible minimum deterrence’ that India has promised to pursue, dictates that as technological developments occur in the neighbourhood, India would take suitable steps accordingly. The current MIRV test is a fall-out of this process.
MIRV capability requires miniaturization of warheads. From open-source intelligence, it appears that the Indian nuclear establishment has been continuously miniaturizing the warheads thereby reducing the weights and providing more accommodation on the MIRV-bus. It is widely estimated that Agni-V can take ten RVs on its bus. Unlike China in our neighbourhood which has global ambitions, our missiles are to assure national security and do not threaten others. The latest MIRV test does not therefore upset the strategic stability in the region.
Unlike China in our neighbourhood which has global ambition's, our missiles are to assure national security and do not threaten others. The latest MIRV test does not therefore upset the strategic stability in the region.
The MIRV capability will take some time to enter into production missiles and the Strategic Forces Command’s (SFC’s) portfolio, because proving needs to be done with repetitive tests. But MIRV will place a bigger demand on the number of nuclear warheads, thereby increasing our arsenal size depending upon the production rate of Agni-V. As K-5 and K-6 SLBMs begin to be deployed, they will also be MIRVd easily once the Agni-V MIRV is validated and fine-tuned. Thus, Agni-V will play the same role for these missiles as the base platform, that Agni-III played in the case of development of Agni-V.
Conclusion
The MIRV capability has been in the works for a very long time and successive DRDO Chiefs have spoken many times since c. 2013 about incorporating this feature in Agni-V. Also, the mature and successful Indian space programme had all the tools and knowledge necessary for MIRV capability. This capability requires an accurate missile which the Agni-V platform readily provided with its impressive CEP which resulted from “redundant Navigation systems, very high accuracy Ring Laser Gyro (RLG) based Inertial Navigation System (RINS) and the most modern and accurate Micro Navigation System (MINS)”. Thus, the latest test has not come as a surprise.
The nuclear weapon scenario in our neighbourhood is worrisome, to say the least. We are situated between two inimical neighbours who have been partners in proliferation and collusion against us. The latest seizure of a CNC machine destined from China to Pakistan under false declarations of ownership prove that transfer of hardware, technology, and training from China to Pakistan in the missile and nuclear fields continue unabated. Various strategic nuclear treaties between the US and Russia have unravelled in the last few years and new and rogue players surround our country. China is openly expanding its arsenal rapidly. China is also talking of placing nuclear weapons in orbit or exploding nuclear weapons in space. The Chinese have successfully demonstrated Hypersonic Glide Vehicles (HGVs) and Fractional Orbit Bombardment Systems (FOBS), both of which can defeat all BMDs. In a way, we are going back to a Cold War era which is much ‘hotter’ now than previously. While such developments and casual talks of using nuclear weapons are abominable to a dharmic country like ours, we nevertheless need to be completely abreast of all technologies such as nuclear, space, quantum, cyber etc. in order to secure one-sixth of humanity within our borders.
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