ON 29 March 2023, the United States officially announced that it is planning to end its Air-launched Rapid Response Weapon (ARRW) program after an all-up-round prototype test failed earlier in the same month. The decision came when Russia and China have already fielded their hypersonic weapon programs in different capacities. US Air Force has commented that it will shift focus from ARRW towards its air-breathing weapon concept, Hypersonic Attack Cruise Missile (HACM). Both systems are hypersonic; however, the key differences lie in the propulsion systems of these weapons which have evolved overtime and offer different possibilities. The different hypersonic technologies, in turn, dictate the desirability of the state to acquire the type of hypersonic weapon based on their operational requirements.
Hypersonic flight technology is not novel. The history of an object which could fly five times the speed of sound, or Mach 5, goes back to the first American-manufactured object to enter space, a Corporal missile on the top of a German V-2 rocket, which attained hypersonic speed in 1949. Since then, advancement in technology has been rapid; especially after the US dedicated X-15 hypersonic research program to explore high-speed flight and the resultant X-15 aircraft was able to reach speeds of up to Mach 6.7. However, the novelty of today’s hypersonic flight technology lies in the weapon’s ability to fly at hypersonic speed within the atmosphere or below 100 kilometres altitude. These objects experience a phenomena unique to the atmosphere, such as extremely high temperatures, intense flow friction, ionisation of the surrounding gases and plasma production. To qualify as hypersonic, a weapon must be able to withstand such circumstances.
Currently, the worldwide efforts to operationalise hypersonic weapons include two types of weapons systems: boost-glide missiles and cruise missiles. The ARRW is a boost-glide system, while HACM is an air-breathing cruise missile. Boost-glide vehicles are launched from a rocket booster and are released when they reach hypersonic speed and glide their way toward their target in a flat trajectory compared to an inter-continental ballistic missile. Hypersonic cruise missiles (HCMs), on the other hand, are powered by air-breathing jet engines called scramjets which utilise oxygen from the atmosphere as fuel as they cruise toward their target at an altitude of around 20 kilometres. A state’s procurement efforts of either of these hypersonic weapon systems depend upon which one will best serve its strategic goals.
Although boost glider technology is more advanced than that of air breathers and HCMs, the US is more invested in air breathers. HCMs can easily fit on an aircraft as air breather engines of HCMs do not need to carry their own oxygen and are much smaller than the boost-glides whereas boost gliders are mostly ground-launched or sea-launched. HCMs can easily integrate into the US military’s existing operational capabilities in striking time-critical targets or conducting sustained operations over continental distances in strategic operations that typically involve global objectives.
On the other hand, China has heavily invested in boost-glide vehicles. It revealed its first ‘combat ready hypersonic weapon’ DF-ZF hypersonic glide missile carried on Dong Feng 17 (DF-17) in 2019. This missile operates from the ground as it is mounted on a specialised launcher that can be transported by a wheeled vehicle. It allows military campaigns across multiple geographic regions to achieve theatre-level operations, especially in the South China Sea and the Indo-Pacific.
Likewise, Russia has also deployed its own hypersonic boost-glide vehicle, Avangard, which entered serial production in 2018 and can attain the speed of Mach 27. Russia, in fact, leads the hypersonic arms race as it launched its first-ever submarine-launched hypersonic cruise missile Zircon/Tsirkon, in January 2023, which can attain a speed of Mach 8. These weapon systems grant strategic flexibility by allowing Russia to strike targets quickly and from unexpected directions, secure its strategic objectives and help maintain its position as a major global power. The country also became the first to have claimed to use six of its hypersonic Kinzhal missiles in Ukraine last year (2022). These missiles can travel at the speed of up to Mach 10.
Other countries, including Australia, North and South Korea, Brazil, Iran, Germany, Israel, India and Japan, are also developing hypersonic programs. The consistent advancement in hypersonic flight technology over the previous decades has the potential to yield a wide spectrum of hypersonic weapons designs ranging between these two major types. However, the procurement of the type of hypersonic weapons will remain dependent upon the wider strategic goals that the states want to accomplish vis-a-vis the cost of the weapon. Similarly, in the case of Pakistan, for any such pursuit, strategic benefits would have to outweigh the cost of these weapons.
—The writer is a researcher at the Centre for Aerospace and Security Studies (CASS), Lahore, Pakistan.
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