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Hypersonic Defence series.  
(Access to other chapters at the end of this article)

When enemy forces are threatening to launch hypersonic missiles, capable of hitting your population centres, harbours or airports within minutes, the protective shield that needs to be activated involves several steps. Early warning, command & control, as well as detection, identification and tracking of incoming missiles… they are all key enablers, as explained in the previous episodes in this series.

But one protective step is arguably the most essential. That is the one that physically prevents the enemy’s missiles to arrive at their targets, never mind their hypersonic flight characteristics. This is the actual engagement of the threat: its destruction-in-flight or shooting-down. It is the face of the shield, or perhaps more appropriate: the spearhead of a theatre-wide defence capability.

And it’s not a simple task. One dilemma to consider, for example, is whether to intercept the threat when it is in the glide- (cruise-) phase of its flight; or alternatively, during the terminal phase when it is already homing in on its target.
 

Glide- or cruise phase interception

The first option (glide- or cruise phase interception) offers the possibility to defend population centers and other high-value assets that are spread out over a larger area. This approach benefits from the circumstance that hypersonic missiles are less able to maneuver in this phase of their flight. Provided that the interceptor missile’s propulsion system can sustain high velocity and agility at high altitude and for sufficient time, the intercept can be achieved easier and can be done covering a larger flight domain (footprint).
Furthermore, engagement in this phase opens up the possibility of a “shoot-look-shoot” approach: should the initial attempt fail, there will be time for a second shot, using terminal-phase interceptor(s).
 
However, both the speed and the altitude of such engagements will always be high, making weapon system allocation more complex. Note that it is more difficult to predict the hypersonic missile’s intended target when it is still in the cruise phase. Importantly, the flight altitudes involved require a long-range interceptor of a type that doesn’t exist today (development programs are running), as well as the associated fire control capability.

Moreover, glide- or cruise phase engagement almost inevitably will raise political issues at a multinational level (potential issues include who decides, who intercepts, where to intercept, rules of engagement and debris/fragments issues).
 

Terminal phase interception

The second option is terminal phase interception. This is suitable only for local point defence (smaller defended footprint). Typically, terminal phase engagement is used for the protection of sensitive military assets such as C2 centers or fixed sensor sites, to prevent their destruction. It is not adapted to defend large areas or sprawling population centers.

Advantages of terminal phase engagement are that the threat’s speed is reduced and its flight altitude is lower, and that improved versions of existing interceptors can be used.
But there are also drawbacks.
Because of the lower altitudes at which the threat is to be intercepted, dynamic pressures will be high (the lower the altitude, the more dense the air). That means that for being able to defend a fairly large area, the price to pay for interceptor propulsion will be high (because of the acceleration needed in short time). 
Also, the trajectory of the incoming hypersonic missile is less predictable at this stage, because of their ability to now exploit their hypersonic maneuvering capabilities. This creates confusion in the engagement plan and can lead to possible exhaustion of interceptors.
There’s no second chance if the intercept fails. 
Finally, interception in the final phase will generate debris that may come down and cause casualties or damage in the defended area.

As discussed in the previous chapters, an optimal approach involves the use of :
•    diverse active and passive space, air and ground-based sensors in a sensor grid architecture, with dynamic sensor tasking to enhance early detection, identification and tracking;
•    integrated C2 across domains and across countries, boosted with AI to accelerate the “OODA” (observe, orient, decide, act) loop.

This collaborative approach improves threat detection, evaluation, tracking and engagement, thereby enhancing accuracy, lethality, range, and coordination in countering hypersonic threats.
 

Collaborative engagement

The hypersonic threat engagement capability encompasses collaborative force planning, threat evaluation, and initial engagement coordination within the organic structure of a battery. It involves optimizing weapon system assignment based on a common threat list and leveraging sensor and C2 quality of services through the grid.
 
Additionally, the capability entails collaborative engagements optimization through "kill chains" (find, fix, track, target, engage and assess), gradually opening up to advanced levels such as: 
•    Engage-On-Remote (the engaged target is tracked by an external sensor) or 
•    Engage-On-Network (“Any Sensor, Best Shooter” approach). 

Interception performance management is based on the sensor grid, communication characteristics, kill-chain type, and expected threat behaviour, ensuring effective weapon allocation and engagement in response to hypersonic threats.

The evolutions would involve the development of a dynamic networking approach to enhance performance of existing national systems, while maintaining interoperability and enabling on-demand activation of interactive dynamic modes. 
Additionally, there would be an emphasis on improving interactivity, performance, and resilience of future Integrated Air & Missile Defence (IAMD) / Ground-Based Air Defence (GBAD) systems. This can be achieved through the optimization of sensors, C2, and engagement methodologies, intelligent dynamic networking, and the implementation of smart modes at the weapon/fire control systems level. 
Furthermore, a standard for dynamic planning, management, and tasking within IAMD and GBAD Weapon Clusters would be established and shared.
 

Functional requirements

The main functional abilities encompass a cost-effective system-of-systems architecture with smart functionalities, facilitating fluid data and command exchange between heterogeneous national weapons clusters. 
It involves dynamic interactivity between multi-layered IAMD/GBAD weapon clusters through real-time data, service, and resource exchange. As well as performance optimization with adaptive resources management and AI-enhanced tactical modes. 
Dynamic management and tasking of sensors and weapon grids are tailored to changes in the C4I environment, including re-assignment of system parts in case of vital part malfunction. These capabilities ensure optimized interaction, resilience, and adaptability across the integrated defence systems.
 

Expected benefits

The system-of-systems seeks to improve engagement performance by effectively combining sensors and effectors for target neutralization. This adds value to national capacities while ensuring system compatibility under C4I chain control. 
It delivers the capability of intercepting highly manoeuvring and hypersonic threats, minimizing engagement loop delays, and enhancing the effectiveness and resilience of IAMD/GBAD systems. These objectives encompass improved capacity against multiple threats, hypersonic manoeuvring TBMs, and complex drone swarms, thus bolstering overall defence capabilities.
 

Thales contributions

Thales contribution to Hypersonic Missiles engagement includes the integration of interceptor missiles and their fire control into end-to-end solutions, as well as active participation in relevant European or US weapon system studies.

A key example is Thales’s involvement in the Hypersonic Defence Interceptor System (HYDIS) programme, which is as stated on the website a “wider European collaborative response to the pressing need for a new interception solution able to effectively protect European territory, population, high value assets and deployed forces in the years ahead.”
HYDIS falls under the auspices of the European PESCO initiative TWISTER (Timely Warning and Interception with Space-based Theatre surveillance), and is supported by collaborative effort between the EU, industry and government, bringing together 19 partners and more than 30 subcontractors from 14 European countries.