Sunday, December 4th, 2022 20:29:08

Hypersonic weapons  A massive force multiplier

By Amartya Sinha
Updated: February 1, 2021 5:22 pm

The Defence Research and Development Organisation (DRDO) created history on September 7, 2020 when it successfully test-launched the much-awaited HSTDV (Hypersonic Technology Demonstrator Vehicle). The technology is the basic prototype of India’s next generation cruise missiles and hypersonic aircrafts. “The DRDO has today successfully flight-tested the Hypersonic Technology Demonstrator Vehicle using the indigenously developed scramjet propulsion system. With this success, all critical technologies are now established to progress to the next phase,” said Defence Minister Rajnath Singh in a statement soon after the execution of the flight.

“DRDO with this mission, has demonstrated capabilities for highly complex technologies that will serve as the building block for next-generation hypersonic vehicles in partnership with industry,” an official statement from DRDO endorsed and further validated the test-firing results. The historic flight witnessed India joining the elite league of three other global military superpowers (United States of America, Russia and China) who have successfully demonstrated a working scramjet engine-powered hypersonic cruise missile prototype.


Political will behind HSTDV test

While HSTDV was approved by then Prime Minister Atal Bihari Vajpayee-led NDA-1 government in early 2000s and the design for the airframe attachment with the engine was completed by 2004, the following UPA-1 and UPA-2 governments led by Prime Minister Dr Manmohan Singh failed to make any significant progress in the vehicle’s development and testing. A year before taking over as the DRDO chief, Dr Vijay Kumar Saraswat had stated, “The HSTDV project, through which we want to demonstrate the performance of a scram-jet engine at an altitude of 15 km to 20 km, is on. Under this project, we are developing a hypersonic vehicle that will be powered by a scramjet engine. This is dual use technology, which when developed, will have multiple civilian applications. It can be used for launching satellites at low cost. It will also be available for long-range cruise missiles of the future.”

While DRDO scientists were getting ready with the critical technologies for the missile, the UPA-2 government imposed severe restrictions on Dr VK Saraswat’s financial powers thereby crippling many of the R&D efforts. The momentum for development of the aerial vehicle and the maiden test finally picked up pace after the NDA-2 government led by Prime Minister Narendra Modi was elected to power in May 2014. With significant progress being made towards a flightworthy vehicle within a five-year time period, the weapon was finally test fired on June 12, 2019, thereby rejuvenating and reinstating the strategic vision of scientists, policymakers and the ruling political establishment in the national security doctrine. But the June 2019 maiden test-firing of HSTDV didn’t go as per expectations as the Agni-1 booster failed to reach the required altitude of 30 kms for a successful scramjet engine ignition of the test article. The preparations for the second test began soon after conclusion of the maiden unsuccessful flight.


A deadly capability in the making

HSTDV will be one of the most devastating tactical-level hypersonic cruise missile in India’s arsenal when it is commissioned into service with the Indian Armed Forces in the next five years. Powered by an indigenously developed scramjet engine and capable of flying at speeds of up to Mach 12 (14,817 kms an hour), it can evade any kind of current generation anti-aircraft and anti-missile systems in the world due to its high-hypersonic terminal velocity.

The prototype tested on September 7, 2020 was a 5.6-metre-long aerial glide vehicle featuring a flattened octagonal cross-section with midbody stub-wings and raked tailfins along with a 3.7 metre rectangular section for air intake. The scramjet engine was located under the mid-body with the aft-body serving as part of the exhaust nozzle. Two parallel fences in the forebody were meant to reduce spillage and increase thrust. Part span-flaps were provided were provided at the trailing edge of the wings for roll-control. A deflectable nozzle cowl at the combustor end was capable of deflecting up to 25 degrees to ensure satisfactory performance during power-off and power-on phases of the flight. Surfaces of the airframe’s bottom, wings and tail were made up of Titanium alloy, while Aluminium alloy comprised the top surface. The inner surface of the double-walled engine was Niobium alloy and the outer surface was made from Nimonic alloy.

After designing and ground testing of technologies related to engines, hot-structures, aerodynamics and aerothermodynamics were complete, the work was completed on mechanical and electrical integration, control and guidance systems along with their packaging, checkout system, HILS (Hardware in Loop Simulation) and launch readiness.

The case for hypersonic missiles

Nations often aim at developing credible weapon systems that would strengthen their non-conventional or conventional deterrence. Credibility is ensured when states possess weapons that can reach targets on time. Weapon systems that are capable of evading enemy missile defence systems further strengthen deterrence by ensuring that the weapon systems are credible. One of the biggest challenges for states has been to develop weapon systems that could reach time sensitive and mobile targets that requires weapon systems with greater speeds. The concept of ‘Prompt Global Strike’ whereby the United States plans to develop a family of weapon systems that can reach any part of world within an hour is precisely to address the issue of reaching time sensitive targets. The need to reach time sensitive targets in a timely manner was realised in 1998 when the US Tomahawk cruise missiles were fired against terror hideouts of Osama Bin Laden but in vain as by the time the missiles were fired, Laden had already escaped.

Hypersonics, therefore is emerging as an option to reach time sensitive targets. Hypersonic weapon systems will travel at speeds of Mach 5 and above that require a massive technological breakthrough. Work on such technologies took place in the United States during the times of Cold War. Progress was made on scramjet technology that would provide the basis for developing hypersonic systems as these missile systems require scramjet engines rather than depending on ramjet ones. Not only the United States, but Russia and China have also been working on both hypersonic cruise missiles as well as hypersonic technology vehicles (HTVs) or rather hypersonic glide vehicles (HGVs) on a war footing. HTVs and HGVs can be mounted atop long-range ballistic missiles to enable them to evade enemy missile defence systems. Unlike the United States that is developing conventional HTV technology, Russia and China have progressed with nuclear capable ones.

It is a known fact that China and India have territorial disputes and to add to this, both the countries possess nuclear weapons that can be delivered by sophisticated ballistic missiles. If China develops a capability, India will need to follow suit in order to maintain the stability-instability paradox. Deterrence whether conventional or nuclear is usually strengthened when there is parity between two adversaries as otherwise, it could lead to conventional or nuclear blackmailing by the state which possesses more capable weapon systems than the adversary. In addition, the Missile Technology Control Regime (MTCR) does not mention the nuances of hypersonic systems and to add to it, China is not a party to the MTCR also. Hypersonics carry little or no payload for the system to fall under the MTCR restriction category of 500 kg payload and above. Thus, technology control regime also can do little do prevent the development of such deadly weapon systems. Hence, for India, the only way to strengthen its deterrence vis-à-vis China is to develop similar systems as ‘defence by denial’ strategy to defend against hypersonic systems would be a cumbersome and expensive and not a full proof process for India.

India is already making progress towards a hypersonic version of the BrahMos supersonic cruise missile. In June 2019, India also conducted a test of Hypersonic Technology Demonstrator Vehicle (HSTDV). The trial has failed to provide fruitful result when the Agni-I on which the

HSTDV was mounted atop failed to reach the desired altitude. The missile lost control midway and hence, the HSTDV could not undergo trials. But now the success of the second test of HSDTV on September 7, 2020 has instilled new rays of hope among the scientific and strategic community.

Scramjets are Supersonic Combustion Ramjet engines that allows for improvement over the ramjet-powered propulsion modules and ideally suited for air-breathing technologies. Air breathing technologies use atmospheric oxygen as oxidisers. Since the technology would use atmospheric oxygen as oxidiser, there is no hassle to carry oxidisers with it. Air breathing technology makes the weapon system lighter and capable of carrying greater payload at greater ranges. Tandem boosters may be used for BrahMos-2 in case they are canister launched.

ISRO is reported to be using hydrogen as fuel that is easily flammable resulting in small amount of energy required for ignition that help it burn faster resulting in generating huge thrust. However, many systems like the US designed X-51A Wave Rider uses hydrocarbon fuel that is denser than hydrogen fuel and suited for scramjet engines.

In fact, the successful flight test of the scramjet technology in 2016 was viewed by the Indian Space Research Organisation (ISRO) as an important development for its Air Breathing Propulsion Project. In this flight test, according to ISRO, critical technologies such as ignition of air breathing engines at supersonic speeds, air intake mechanism and fuel injection systems were successfully demonstrated. During the flight test, ISRO was able to handle several challenges akin to hypersonic and scramjet systems including supersonic combustor, development of materials withstanding very high temperatures, computational tools to simulate hypersonic flow, ensuring performance as well as engine operability during varied range of flight speeds, thermal management and ground testing of engines.

If India manages to develop successfully the HTVs or HGVs that could be mounted atop the solid propelled Agni-class of missiles, it will provide a greater deterrence vis-a-vis China as well as Pakistan. China and Pakistan would find it difficult to neutralise the weapon system during times of war. Agni forms the backbone of India’s land based nuclear deterrence, and HTVs on Agnis would strengthen nuclear deterrence, and since the missile could be difficult to be intercepted it would strengthen India’s posture of ‘credible minimum deterrence’ and doctrine of ‘no-first use’ as well.

Agni-series missiles fitted with multiple independently targetable re-entry vehicles (MIRVs) and HTVs would provide greater scope for ensuring nuclear deterrence vis-a-vis China. HTVs will also have less or no adverse effect on the range of the missile, thus, letting the range of the missile intact as opposed to other countermeasures like MIRVs, depressed or lofted trajectory of ballistic missile that significantly reduce the range of the missile.

With India and Russia also moving closer to their joint venture of developing hypersonic BrahMos cruise missile called the BrahMos-2. According to BrahMos Aerospace, the hypersonic weapon’s immense destructive power will result from massive kinetic energy making it best suited to target hard and deeply buried targets. A weapon system that strikes a target at Mach-6 will always create greater impact than the weapon system striking its target at Mach-1. In the coming decade, BrahMos will be able to strike targets at Mach-7 speed.

The hypersonic version of the cruise missile will not use the same engine ramjet engine used by the supersonic missile but will be replaced by scramjet ones. In fact, many sources claim that the BrahMos-2 can use the same scramjet engine as used in the Russian Zircon hypersonic cruise missile system. The supersonic missile has been modified over the years to be able to be fitted into ships, submarines, combat aircraft and also can also be ground-launched. It would be a matter of time to see how successfully India can make the hypersonic version of the cruise missile capable of being launched from the sea, air and ground.

The hypersonic version of BrahMos will have a strike range of 600 km with the ability to manoeuvre through hostile air and missile defence systems. The weapon may have stealth technologies as possessed by the supersonic cruise missiles. According to Late President Dr APJ Abdul Kalam, “In the emerging network centric warfare scenario, the fast development of hypersonic missile systems will be necessary to maintain our force level supremacy.” Long range hypersonic systems, according to Kalam, will not only deliver payloads, but can return to base after mission leading to reusable class of cruise missile. Given the geographical proximity between India and Pakistan and ability of hypersonics to remain undetected, their quick response and high manoeuvrability provide not just tactical advantage to India but also a huge strategic boost.

Defence against hypersonic cruise missiles

While the US Terminal High Altitude Area Defence (THAAD) is reported to be capable of defeating hypersonic cruise missiles, its success rate is yet to be known. Technologically, defeating hypersonic cruise missiles would be a herculean task. In addition, there is no known defence against HTVs or HGVs. Space-based weapon systems may be used to defeat these technologies, but they are still at their nascent stage of development in the United States. In fact, space-based assets may remain confined to warning, launch detection, surveillance, acquisition and tracking rather than the actual task of interception, though the United States has ventured into a ‘Glide Breaker’ for space-based interception. Laser-based weapon systems are being developed to defeat a ballistic missile at its boost phase itself so that the counter measures like HGVs find no scope to function.

While hypersonic or even very high-speed interceptors could be a solution, how far they will be credible can only be known if they are developed. Kinetic energy interceptors and directed energy weapons (DEWs) can become a solution to defeat hypersonic cruise missiles, but that too is also at an experimental stage. Other options to defeat them may include particle beams and non-kinetic weapons. Cyber and electronic attacks could help to attack networks (intelligence, surveillance, target acquisition and reconnaissance that support such hypersonic weapon systems and their functioning. Destroying the launch platform is another ideal solution, however, launch platforms themselves would have their own countermeasures against enemy defence systems.


The future unfolds

Possessing these technologically advanced weapon systems will always increase India’s status and prestige at global high tables. It will provide massive strategic and tactical gains against Pakistan and China. HSTDV will be capable of carrying conventional, nuclear, and thermonuclear warheads up to unspecified ranges. If India develops scramjet-propelled manoeuvrable hypersonic atmospheric re-entry vehicles that can be fitted atop the Agni-V and the upcoming Agni-VI ballistic missiles in the near future, such HGV (Hypersonic Glide Vehicle)-based warheads can be installed as MIRV (Multiple Independent Re-entry Vehicle) strike packages in the payload-fairing of long-range ballistic missiles, thereby massively enhancing the weapons’ ranges. Moreover, other than the next generation cruise missiles, the technology can also be applied for developing low-cost space-launchers on the lines of SSTO (Single-stage-to-orbit) and TSTO (Two-stage-to-orbit)-based spaceplanes in the not too distant future. With the second test of HSTDV being dubbed a roaring success, DRDO is also in the process of stepping into the next level of hypersonic aerospace propulsion research with a third test being planned in the first quarter of 2021. The third test (codenamed- HS-03) may witness the launch of a modified booster with slow burning propellant. There is no going back from here, and the process of technology development and weaponisation should continue unabated.


By Amartya Sinha

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