In the beginning of March this year, Russia launched its biggest aerial attack in its ongoing war with Ukraine. The attack comprised a variegated weapon mix, the most interesting one of which was reported to be six air-launched Kinzhal (literally ‘dagger’) hypersonic missiles with a speed of Mach 10 and a payload of 480kg. Although hypersonic weapons had been used earlier during the war, this was the first time that six were used in a single wave. The Kinzhal is a modified version of the Russian Army’s Iskander Short Range Ballistic Missile (SRBM) which is a truck mounted weapon system. The Kinzhal version is launched at high altitude from modified MiG-31 aircraft to get maximum range out of its onboard fuel. Intriguingly, Putin, during an interview in March 2023 just before his visit to occupied Ukranian city Mariupol, stated that Russia had hypersonic weapons, but had not used them in the Ukraine war.
This innovative improvisation of the Kinzhal highlights the developments underway in the area of hypersonic weapons which are the nub of a global arms race. While US, China and Russia are leading the race neck and neck, other players are Australia, Brazil, France, Germany, India, Iran, Israel, Japan and the two Koreas. Russia is the first nation to induct hypersonic weapons into its military namely the Avangard and Kinzhal in 2018 and Tzircon in 2019 and the first to use hypersonic missiles in anger in Ukraine.
Realising the combat value of hypersonic weapons, India has been making endeavours to develop them on its own and has successfully demonstrated an indigenously developed vehicle. This article addresses the significance of hypersonic weapons, and developments in that field in India.
What Exactly is Hypersonic?
The Mach 5 (five times the speed of sound) barricade between supersonic and hypersonic weapons serves to emphasise the engineering challenges that face designers creating aerial platforms capable of speeds of Mach 5 and above. But what exactly is Mach 5 speed? During their trajectories, most hypersonic weapons go up to high altitudes where the atmosphere is rare. The ‘Mach’ relationship to speed of sound depends on the composition, temperature and density of the medium the vehicle is travelling through. The speed of sound in a gas medium which air is, is proportional to the square root of the gas temperature. As the vehicle moves higher and higher, the atmosphere becomes inconsequential and measurements related to the speed of sound become meaningless.
According to the Stockholm International Peace Research Institute (SIPRI), scientists and engineers agree that it makes sense to talk about Mach numbers up to altitudes of 30km. Beyond that altitude, the relevance of this concept reduces. However, there is no internationally agreed altitude up to which the definition of ‘hypersonic’ speed would find universal concurrence. As sound does not travel in vacuum, the Mach number is undefined in vacuum conditions.
There are other grey areas in defining ‘hypersonic weapons’. The term ‘hypersonic’ seems to imply that speed is the primary characteristic that defines a hypersonic vehicle. However, that is not an exclusive definition. The V-2 rocket could reach a speed of Mach 5 briefly, but is never referred to as a hypersonic missile. Similarly, most ballistic missiles reach much higher speeds than Mach 5, some touching Mach 20, especially during descent and re-entry into the earth’s atmosphere, but are not called hypersonic weapons. The generally accepted attribute of the hypersonic vehicle (besides a Mach 5 speed) is the ability to manoeuvre during its entire flight including while flying at hypersonic speeds. By that logic, the rocket powered X-15 Hypersonic Test Vehicle (HTV) flown by US National Aeronautics and Space Administration (NASA) in 1959 was the first vehicle to fly hypersonic (Mach 6.7). Since then, several major developments have taken place in the hypersonic R&D space.
Hypersonic weapons are essentially of two types. Hypersonic Glide Vehicles (HGVs) are generally launched piggy back on ballistic missiles and then released to glide back through the atmosphere towards their designated target. Manoeuvring control is achieved through control surfaces on the weapon airframe. Russian HGV Avangard is an operational example. Hypersonic Cruise Missiles (HCMs) execute self propelled, powered flight all through their mission which is generally flown entirely at hypersonic speeds. Kinzhal and Tzirkon are operational Russian HCMs. There could be hybrid versions as also variations like the air-launched Kinzhal mentioned earlier.
Hypersonic Objects of Military Desire
Technology levels, design features and engineering ingenuity differentiate within hypersonic weapons, but some of their common characteristics make them objects of desire. The foremost advantage they offer is their low visibility to ground-based radars. While ballistic missiles go up considerably high, almost to the edge of earth’s atmosphere, HGVs launched by ballistic rockets are released at much lower altitudes and are thus not easily visible to ground radars. HCMs, of course, fly at considerably lower altitudes typically just around two hundred feet above ground level, the only limitation being the reaction time for manoeuvring over terrain at high speeds. Moreover, hypersonic weapons are manoeuvrable and, thus, can be routed tactically and be flown to avoid anti-missile systems. The current effectiveness of air defence systems against incoming hypersonic vehicles is extremely low and most proof of concept hypersonic test flights bypass modern defence systems with ease. It may be mentioned however, that some nations are working on placing detection sensors in space for aerial vehicle sensing although that is an area of complex challenges and is still ‘work in progress’.
Another advantage is that they can be launched from land, sea or air and thus offer flexibility in terms of operational deployment. Another flexibility feature is that they can be dual use i.e. capable of carrying a conventional or a nuclear warhead. While the combat use of a hypersonic vehicle with a nuclear warhead is not a very likely event, the capability exists. Moreover, because of the very low vulnerability to enemy air defences, the high degree of sophistication in satellite navigational accuracy and very large, continental ranges, hypersonic vehicles are capable of delivering even conventional loads with such precision that the impact is strategic. The Kinzhal has reportedly been used against strategic targets like munitions storage facilities and critical bridges. For strategic effect, they could also be employed for precise strikes on command and control installations or fortified bunkers and potentially time-sensitive moving targets such as combat ships. Russian warship Moskva, the flagship of the Russian Navy’s Black Sea Fleet, was hit by a cruise missile in April 2022 although the missile was not hypersonic.
Hypersonic weapons add a new dimension to the concept of retaliation. Firstly, their low vulnerability to defences assures almost certain retaliatory capability and secondly, the retaliation can be escalated gradually from conventional to threat of nuclear use. Even when hypersonic weapons are used collateral damage is kept to a minimum due to the high accuracy and controlled payload of the vehicle. Thus, it could be argued that hypersonic weapons assure penetration, permit scalability of assuredly delivered conventional payloads and thus avert nuclear crises.
India’s Hypersonic Quest
R&D on hypersonic weapons in India goes back to 2007. In his address at the Defence Research and Development Organisation (DRDO) Directors Conference held on February 21, 2007, Dr APJ Abdul Kalam had stated that he visualised hypersonic cruise missiles as one of the defence systems that would be needed by India in the next 15 years. India’s primary hypersonic pursuit is premised on the remarkably successful BrahMos (portmanteau word combining Brahmaputra and Moskva) medium range, supersonic cruise missile also designated PJ-10 which can be launched from air, land or ships and submarines. It was the fastest supersonic cruise missile at the time of its introduction and was the result of a joint venture called BrahMos Aerospace between India’s DRDO and Russia’s NPO Mashinostroyeniya. The hypersonic missile programme underway at BrahMos Aerospace is expected to produce the BrahMos-II missile fashioned after the Russian Tzirkon which is a scramjet powered anti-ship HCM that can travel at Mach 9, climb to 28km (92,000 feet) altitude and travel to a target up to 1,500km away. It is ship/submarine launched but a land-based version is reported to be under development in Russia.
BrahMos Aerospace was formed in 1998 and the BrahMos missile was first test fired in 2001. Several versions including an air-launched one are in service in India – in the Indian Navy in 2005; in the Indian Army in 2007; in Indian Air Force in 2020. BrahMos-II development started under an agreement between Indian and Russia in September 2009 and it was expected to be produced by 2015 initially. As is typical of all DRDO related programmes, BrahMos-II project is running far behind schedule. Reportedly, according to a recent statement by BrahMos Aerospace, once government approval is given, it will take eight years before BrahMos-II is ready for trials. Although media reports keep surfacing about ever new expected dates for trials, the latest one being touted by media being 2024. Reportedly, Konstantin Biryulin, the Deputy General Director of Korporatzia Takteecheskoye Raketnoeye Vooryzhenuye (KTRV), the major holding company for missile manufacture under which the Russian partner of BrahMos (NPO Mashinostroeniya) operates, Russia is ready to pass on hypersonic technologies to friendly nations.
According to him, the BrahMos-II should be ready by 2028. The supersonic and hypersonic versions of BrahMos will be usable only by India and Russia as India is a signatory to the Missile Technology Control Regime (MTCR) which prohibits sale/export of any missiles over 300km in range or capable of carrying over 500kg of payload to a third country besides Russia. India has signed a deal with the Philippines in January 2022 for the sale of BrahMos missiles; but those will have a curtailed range of 290km in deference to MTCR. Delivery is expected to commence this year. Indonesia has also shown interest in the BrahMos. However, while a BrahMos with 290-km range makes moderate sense, having a hypersonic missile with a sub-300-km range would not.
As the US has demonstrated unpredictability in the matter of imposing sanctions on nations in the past, to forestall any sanctions on Russia and/or India related to BrahMos-II, India followed another parallel programme in pursuit of hypersonic weapons capability. Since 2008, the DRDO worked on a Hypersonic Technology Demonstrator Vehicle (HSTDV) with the objective of demonstrating scram jet performance at altitudes up to 20km and speeds up to Mach 6. The scramjet is said to have been developed indigenously although there are doubts about it as Indian R&D in the power plant area has not produced an engine for even the Light Combat Aircraft programme. The HSTDV project was dual use in nature, with multiple civilian applications including launching satellites at low cost and powering long range cruise missiles of the future. The scramjet or supersonic combustion ramjet uses atmospheric air as oxidiser and uses its high speed to compress incoming air before it enters the combustion chamber. It differs from a normal ramjet inasmuch as the ramjet decelerates air to subsonic velocities before combustion while in the scramjet operation, air is at supersonic speeds throughout.
So, the engine can start only after the vehicle reaches a certain velocity for achieving which the vehicle is dependent on some other means of propulsion i.e. a rocket motor. As the scramjet does not carry an oxidiser, unlike a rocket motor, it can operate only in suborbital atmosphere where oxygen is present in adequate amounts to permit fuel combustion in the engine. The HSTDV was first successfully tested in June 2019. This was followed by another successful demonstration in September 2020 up to an altitude of 30km at speeds up to Mach 6.The last test was carried out on January 27, 2023. India is the fourth nation after Russia, US and China to demonstrate hypersonic capability.
An Agni-5 missile test carried out by India in December 2022 was seen by some analysts as peculiar inasmuch as its trajectory was unusually lower than normal for such a test which should have been a high parabolic arch entering space before re-entering the earth’s atmosphere. A section of media conjectured that the launch may have actually tested an HGV. Indian Aerospace Defence News (IADN) posted pictures on Twitter of China’s 2018 DF-ZF HGV launch in Shaanxi province and compared it to the Agni-5 test, pointing out that it showed the “same launch characteristics” and saying that the firing is likely to have tested a Hypersonic Glide Vehicle (HGV) based on its “quasi-ballistic role (and) low velocity rather than a standard ballistic launch.” The DRDO denied any such connection of the Agni-5 test to hypersonic weaponry.
For the sake of completion, a mention must be made of the Shaurya and the Sagarika missiles that India has. The Shaurya is a canister-launched surface to surface tactical missile Medium Range Ballistic Missile (MRBM) developed by DRDO with a maximum range of 1,900km and a maximum payload of 1,000kg which can be conventional or nuclear. It can fly at Mach 7.5 and was inducted into the Strategic Forces Command (SFC) in October 2020. The Sagarika is a Submarine Launched Ballistic Missile (SRBM) with a range of 1,500km and a maximum speed of Mach 7.5. Some analysts believe that the two missiles vary only in their launch location (land versus submarine) but DRDO claims that there is no connection between the two. Sagarika has the designation K-15 and is said to be part of the Strategic Forces Command (SFC) as it has conventional and nuclear warhead carriage capability. Although Shaurya and Sagarika reach hypersonic speeds, their overarching characteristics are more like those of ballistic missiles and less like hypersonic weapons, they neither fit the attributes of HGVs nor of HCMs.
India has a Trisonic Wind Tunnel called thus as it permits testing aerodynamic design of aerial vehicles in three distinct flight regimes: subsonic, sonic, and supersonic by measuring forces, moments and load distributions. It became operational in December 2022. However, the maximum speed that can be tested in is Mach 4 which falls short of hypersonic speeds. This remains a handicap for hypersonic weapons development.
Although Russia is leading the world in hypersonic weaponry, it is China that is the focus of India’s attention on account of China’s impressive strides in the area and the fact that India could be at a possible target for such weapons if a conventional war broke out in the future. China has been working on hypersonic weapons since the turn of the century and its current vision looks at them as apt for both conventional war fighting and strategic deterrence. In 2015, the government gave renewed focus and funding to the technologies relevant to hypersonic weapons: vehicle design, power plant including scramjet, simulation facilities and testing infrastructure. It also set up dedicated clusters of academia and industrial organisations to work on these technologies. China first tested a hypersonic missile in 2018 (Xing Kong-2 HCM) and has tested DF-ZF, an HGV, to be launched from the DF-17 MRBM. It is also said to be testing hypersonic missiles to piggy back DF-21 and DF-26 ballistic missiles which have much larger ranges. A UAV with hypersonic capability has also been reported. Interestingly, the world’s first wind tunnel capable of testing a full-sized hypersonic missile is also operational in China while a similar US project is still work in progress.
These snippets of China’s progress show that India is lagging far behind China in this area. As stated earlier, there are no reliable defences against incoming missiles travelling at hypersonic speeds and interception from the ground or the air is well nigh impossible while space-based defences against hypersonic weapons are still evolving. This fact should provide the impetus for India to accelerate its hypersonic programmes so that viable weapons can deter use of hypersonic weapons by China for fear of retaliation in kind. Hypersonic weaponry technology requires special attention as it is niche and leading edge. The shelving by the US of its five year old Air-launched Rapid Response Weapon (ARRW) hypersonic missile programme in March 2023 after unsuccessful tests, is a portent of the uphill task ahead of Indian R&D.
Speaking on March 21, 2023, at Def-Tech India, an event organised by PHD Chamber of Commerce on ‘India’s Aerospace Capabilities and Technology Requirements’ the Chief of the Air Staff, Air Chief Marshal VR Chaudhari listed hypersonic weapons as a key factor in technology that was changing the conduct of war. Prudence dictates that India heeds this advice and prioritises development of hypersonic weapons as a national security imperative.