What are Hypersonic Weapons?
Very basically, a hypersonic weapon is one that can travel at speeds greater than five times the speed of sound (5 Mach). This works out to 6174 km/h or for better comprehension, 1.6 Kms per sec. Hypersonic weapons have two other characteristic signatures. These are:-
(a) Unlike the conventional ballistic missiles which are initially boosted by one or multiple stages of rocket motors and then left to follow a predictable ballistic trajectory, hypersonic weapons are all-the-way-powered till the end-game enabling them to achieve the kind of speeds as stated above.
(b) Such weapons unlike ballistic missiles (which normally fly for most of their trajectories in the upper atmosphere thus making their ballistic trajectories highly predictable) remain low with unpredictable trajectories.
Why the need of Hypersonic Weapons?
Why hypersonic weapons have become such a hot priority area of development for the front-ranking nations of the world today ( US, Russia, China) is because of their four signature characteristics. These are:-
1. Unstoppability.
With speeds in excess of Mach 5 (up to Mach 10 realized) , hypersonic weapons can hit anywhere on the earth in less than an hour. Weapons hurled at this speed totally out beat the minimum reaction-time cycle of any known conventional air and missile defence system. Such a cycle, howsoever compressed, still requires the target to be detected, identified as hostile, tracked for engagement, assigned to systems and weapons launched at them. This proves to be too long for tackling a weapon closing in at hypersonic speeds. This makes all known conventional air and missile defences redundant when it comes to countering hypersonic weapons.
2. Un-detectability.
In the context of hypersonic weapons , it is stated that ‘speed is the new stealth’ simply because, the current generation of sensors which require a basic minimum time to process target echoes ( active or passive) to achieve detection will simply be beaten by the time window granted by hypersonic threats make such weapons nearly undetectable by conventional sensors.
3. Unpredictability
Again as a function of its speed, hypersonic threats can quickly change their targets beating the defender’s time cycle to re-adjust and re-align. This unpredictability has a multiplicative effect since hypersonic weapons, once launched can keep huge swaths of areas under immediate threat forcing the defender to commit disproportionate resources.
Very basically, hypersonic weapons are being developed in two classes, namely, Hypersonic Cruise Missiles ( HCMs) an Hypersonic Glide Vehicles (HGVs).
HCMs are basically cruise missile in terms of their accuracy (sub-metric), guidance, and low altitude radar-evasive trajectories. These become HCMs because of their capability to fly at hypersonic speeds; a feat which is made possible by keeping the missile all-the-way powered. Hypersonic magnitudes of speeds are possible by use of special engines called the supersonic combustion ram jet (SCRAMJET) engines. Such engines, as the name suggests permit the combustion of gases at supersonic speeds which can produce supersonic acceleration (technical details of SCRAMJET not explained further).
HGVs are based on a different philosophy. These are small aerodynamically shaped glide vehicles that are propelled by booster rocket motors to such tremendous speeds where the shock waves generated by their own flights start acting as lifting surfaces. These waves greatly reduce the drag and increase the lift so tremendously that the vehicle riding on such shock waves achieves speeds in excess of Mach 5 and more. Due to this peculiar phenomenon, HGVs are also called ‘wave-rider’ weapons.
4. Catastrophic potential
What is the effect of kinetics on warhead can be judged from the fact that one kg of warhead hurled at a speed of 5 Mach has an effect that is 36 times higher than the same warhead atop a ballistic missile. That said, one can imagine he catastrophic kill potential of many hundreds of kgs of warheads riding at super hypersonic speeds on board hypersonic weapons.
Hypersonic threat in a nutshell
The emerging hypersonic threat from China today is as under:-
(a) China has both the HCMs as well as HGVs. Both these are in the development and proof-of-concept stage.
(b) While the work on hypersonics stared in China way back in 2002-03, it matured over the next decade and a half.
In Dec 2017 and again in May 2018 China demonstrated an HGV aboard a DF 17 Ballistic Missile. The HGV flew for 1400 kms and impacted the target in the Xinxiang district. China is working on the HGV project on board DF 41 ICBM 2.
On 03 Aug 18, China reportedly flew an HCM named Xingkong II (also called Starry Sky -2) This HGV flew for about 10 minutes at speeds of 5.5 to 6 Mach (6738-7350 Km/hr) achieving an altitude of 30 Km.
Later Sep 2018 China conducted hypersonic tests on three scaled down hypersonic aircraft models of differently shaped designs. These ‘wide-speed-range-vehicles’ were codenamed D18-1S, D-18-2S and D 18-3S respectively. The special characteristics of this test was, that the speeds of the vehicles were adjustable for a precision strike of an ‘unstoppable nuclear capable’ weapon.
The above suggests that hypersonic threat is gradually but surely building up from China. Currently it is in the developmental stage. The same is likely to become full-blown in a few years from now (specific figure not quoted)
India’s progress in Hypersonic Domain.
Much like China, the hypersonics began in India way back around the turn of the millennium . Some salient points of the journey are stated:-1. Around 2003-04 preliminary work on a hypersonic air frame was started in the DRDO.
In 2008, Dr V K Saraswat , the then DG DRDO hinted at the possibility of dual use of the hypersonic technology which could be utilized both for the low-cost satellite launch vehicles, as well as, a hypersonic cruise missile.
In the period from 2010-16/17, lot of work took place in the hypersonic field. This included multiple tests on experimental vehicles using the tri-sonic wind tunnels made available with the help of Israel, as well as, by the indigenous National Aerospace Laboratory, Bangalore.
The main aspects on which development and testing was carried out included hypersonic aerodynamics and hypersonic thermal dynamics (special heat shields needed to be developed to withstand super high temperatures developed during the hypersonic processes). Other tests included the integration of mechanical and electrical components for operation at hypersonic speeds and putting in place a guidance and a control system that can steer such vehicles to their destined targets.
It was in Jun 2019, when the first HGV got ready for range testing. This vehicle was carried on board Agni 1 to provide it the initial boost. The tests were partially successful. After a gap of about three months HSTDV was tested again on 07 Sep 2020. Some salient points about this launch are covered:-
The flight of the HSTDV was tracked all-the-way from the launch till the end game by a series of sensors deployed on the fully-anointed Interim Test range at Chandipur. These included ground-based tracking radars, electro-optical systems, telemetry stations, as also ship-borne radars. In a matter of just 20 sec time of flight, the vehicle achieved Mach 6 and an altitude of 30 km.
Challenges ahead:
a. Achieving still higher Mach speeds and altitudes.
b. Increasing the time of flight of the HCMs.
c. Experimenting with larger and heavier aerodynamic vehicles capable of higher ranges and higher payloads.
d. Achieving better and better accuracies (sky is not the limit for this).