Introduction
France, in 1794, was the first nation to use aerial balloons for reconnaissance purposes. Subsequently, it took almost 100 years for the German military to realize that small cannons could be used to intercept those balloons. The ‘Ballonabwehrkanone’ using a 3.7 cm cannon mounted on a horse carriage can be considered the first active air defence weapon, albeit with a very low rate of success. Target tracking, aiming and firing the cannon was mostly based on the gunners’ talent.
Technological advances over the last 100 years have helped to significantly improve air defence weapons and in parallel improved adversaries’ air capabilities. However, in the latest iteration of this cat-and-mouse endeavour the most recent technological advances could elevate Surface Based Air and Missile Defence (SBAMD) systems to a whole new level; in effect, changing the ‘game’. This article will illuminate how some new ways of system integration, and new means of target interception, might affect the effectiveness and efficiency of, and employment options for, SBAMD systems. Also, it will suggest options for national contributions to future SBAMD networks.
Fixed Sensor and Effector Combination
In general, surface-based air defence systems are designed to counter surface-to-surface or air-to-surface threats by either destroying the opposing effector (e.g. missile) in the air or by destroying the carrier of an aerial weapon before it can be launched. They can also be used to engage other enemy platforms delivering adversary non-kinetic aerial effects such as intelligence, surveillance and reconnaissance, electronic and cyber-attack, and airborne command, control and communications. In order to engage a potential aerial target several factors need to come together. The target needs to be found, identified, tracked and a suitable interceptor needs to be available that can be led to the target. After engagement, a kill assessment needs to be performed. This defines the so-called ‘Kill Chain’. The invention of radar made automated, or at least supported, searching, identifying, tracking and kill assessment possible and enhanced overall situational awareness in the third dimension. Radar engagements progressed from helping to manually aim the cannon, to automatically creating a fire-solution for the canon, to automatically guiding an air defence missile to its target. This engagement paradigm is true for all kinds of potential tracks, such as airplanes, drones or ballistic missiles.
From Isolated AD Applications to Networks
Historically, various technical developments produced distinct sensor-interceptor combinations, which created their own independent equipment ‘ecosystems’, good examples being NIKE1 and HAWK2. Those systems had multiple radars for various tasks, which, in turn, gave air defence units a large footprint on the ground. Later, systems like PATRIOT introduced multi-function radars, which combined all tasks in one machine, but still maintained the fixed inter-unit sensor-effector relationship.3 The net result is that newer systems are smaller and harder to target, but even more effective.
Currently, two ideas are being used to describe the efficiency of surface-based air defence systems against ballistic missiles, and these are the footprint and the battlespace. The footprint is a two-dimensional correlation of ground impact points with calculated intercept probabilities, based on a certain threat from a certain direction that a system can defend. The battlespace is the three-dimensional space within the interceptor’s range where it can effectively intercept targets, and is used to calculate the footprint. The battlespace, in addition to other variables, is limited by the parameters of the interceptor but also by the available track data being locally produced by the system’s organic sensors. In other words, SBAMD systems can normally only shoot as far as they can ‘see’, which historically is a greater limitation than the actual range of the weapon. Future concepts should lead to a maximized battlespace for interceptors by networking sensors to allow earlier target acquisition and engagement. Such layered defence could not only create second shot opportunities but also allow interceptors to use their full potential since freed up from sensor constraints.
The development of tactical data link (TDL) networks, like Link-16, with sufficient reliability and reduced latency opened new possibilities for air defence systems. Connections between weapon systems and Command and Control (C2) networks allowed for changed responsibilities in the ‘Kill-Chain’ and for complex emission control patterns. Systems like PATRIOT can receive cueing data which optimize its own radar and interceptor capacities and maximize the overall battlespace. This is accomplished because cueing a radar helps to significantly reduce target search times for organic tracks. However, the actual engagement is still performed by the fixed sensor-interceptor complex.
Launch on Remote, Engage on Remote and Missile Handover
There are three options readily apparent for exploiting networked sensors and C2 to expand the battlespace and in turn the footprint for modern SBAMD systems.
Launch on Remote (LOR). In this option, a unit fires a missile at a remote target it cannot yet see with its organic sensors based on cueing from the network. The only requirement is that the launching unit must have a local track during the final phase of the engagement, meaning launch must wait until the target is close enough to enter organic sensor range and allow terminal guidance of the interceptor. This concept pushes the boundaries of the battlespace, but is still limited to the maximum range of the organic sensors.
Engage on Remote (EOR). In this option, a unit fires a missile without available organic sensor track data, since it could rely on the interceptors capability of executing the final phase of the engagement automatically based on active sensors and highly accurate, very low latency remote target data. If EOR capability is implemented, organic sensor range and visible tracks are not the limiting factor anymore. Targets outside a line of sight (e.g. behind mountains) could be engaged without local radar coverage but with maximum interceptor range.
Interceptor Handover. A third option is to have the firing unit guide the interceptor to a point in space where a remote unit can take control over the interceptor and provide guidance updates to execute the last portion of the engagement. This option does not necessarily demand interceptors with an active sensor and still gives the option of exploiting the maximum range of the interceptor, however this also comes with its own limitations. Missile guidance communication is based on certain frequencies, protocols and, most likely, encryptions, which are unique to a weapon system, nation or the producing company, which may prevent, or at least complicate, a hand-over.
These concepts reallocate responsibility for certain parts of the ‘Kill Chain’ to various other systems. However, since a typical weapon system life cycle can easily be half a century from conception to its phasing out, it is not that easy to find a common technical basis for a shared ‘Kill Chain’. Adding to the complexity are the administrative challenges for effective information sharing among nations or even different companies. Additionally, the usability of shared information via TDL networks is very dependent on the target set and the network update rates. E.g., target refresh rates over Link-16 are dependent on the network’s technical implementation and management and can last several seconds.4 For a high flying, slow-moving target this might be sufficient, but for ballistic missiles or future hypersonic targets with speeds of several kilometres per second, it is not.
Flexible Sensor and Effector Employment and Intelligent Networks
A vision for future SBAMD systems is to have standardized sensor and interceptor interfaces with reliable access to multi-layered, secure, low latency tactical networks with high update rates. These interfaces can be used to create a dynamic network of systems. However, standardized and disclosed system interfaces won’t necessarily mean public access and standardized system architectures. The ‘plug and fight’ concept of the tri-national Medium Extended Air Defence System (MEADS) shows part of this concept on an intra-unit level.5 The goal should be to have these features on an inter-unit, or possibly inter-system, level. This would allow several new approaches for air defence from contributing nations:
- Tailored to the Mission Environment: The concept of a GBAMD battery could be defined in a new, task and mission environment-oriented way. For the past few years the idea ‘Tailored to the Mission’ has been used, where a battery only deploys the equipment needed for the mission, but still has the battery reference as a baseline. However, a preconceived battery construct is not necessary anymore. The battery size and construct is dependent on the mission needs in the operational environment. E.G. if a robust sensor coverage for the operation area is already present, a networked GBAMD battery does not need to have an organic sensor. If the interceptor density in the mission area is sufficient, a battery might only deploy sensor or communication equipment to support target acquisition and tracking. In effect, the GBAMD defence design can switch from a battery-centric approach to a capability centric approach. This could reduce redundancies and create a more balanced defence design overall.
- Allied Modularity: Due to the many components and their tremendous technical complexity GBAMD batteries are a very expensive commodity and due to their life cycle require a long-term commitment in the defence budget. A modular, capability-centric approach would allow smaller nations to purchase only capabilities needed, in the context of an alliance, to fill gaps on the battlefield and to provide specific elements, instead of an entire GBAMD battery. That could mean purchase of a long-range search radar, a high precision fire control radar or just a launching section with 20 interceptors as part of a bigger network, instead of purchasing an entire THAAD, SMP/T or MEADS battery.
- If an independent battery construct is needed, the battery could be comprised of any compatible components on the participating market. In this case the customer can choose from a far broader spectrum of product capabilities and is not bound to a single source solution.
- Since the envisioned sensor, interceptor or communication interface will not be limited to ground based air defence units, the overall system might benefit from many other Army, Navy, and Airforce systems. A secure multi-layered network would allow controlled integration of alliance and non-alliance members, as well as civilian components.
Technically, an organic, local radar might still be the optimal sensor for a potential target engagement. But that does not mean that networked sensor data could not deliver sufficient target information for a comparable result. The flexibility within the defence design and the ability to adapt the design throughout the mission, perhaps due to damaged or destroyed equipment, bears significant potential benefits. An integrated system of systems could ad-hoc manage all connected sensors and shooters to identify the optimal fire solution.
Directed Energy Weapons
It is very likely that potential opponents have more ballistic missiles, air to surface missiles and other air targets than we have interceptors. This is especially true for ballistic missile defence or in a context of defence against dispensable low-cost unmanned aerials systems. In these cases, the highly complex missile based interceptors sometimes cost a multitude more than the systems they defend against. The more complex the target sets become, the more expensive the countermeasures, which leads to a less robust defensive posture in times of reduced defence budgets. With the available number of high-cost interceptors as the limiting factor, alternative ways of defending against adversary aerial targets need to be found.
There are multiple ways of successful intercept, which are heavily dependent on the targets’ characteristics including size, speed, material, altitude or flight path. Overall, it is important to deliver an impact adequate to either fully destroy or sufficiently damage the target to negate the intended effect. Currently, it is necessary to be able to manoeuvre the interceptor during its flight to have an acceptable intercept probability. Recent developments in direct energy weaponry (DEW), such as laser or rail gun technology, are promising developments for the future. DEW have already proven to be able to intercept some targets like drones or artillery shells.6 Since DEW project energy at the speed of light, target speed and manoeuvrability become a smaller issue that should be compensable by sufficient track data and flight path prediction. Once operational status has been reached, DEW will likely mitigate multiple problems, including:
- Cost per shot dilemma.
- Small number of interceptors (shots) available.
- Necessity of LOR, EOR or any kind of interceptor hand over.
- DEW will also significantly simplify the engagement process and allow concentration of effort on target detection, tracking and the network.
Obviously, DEW still has some obstacles to overcome, like the blooming effect, which defocusses a high-powered laser beam over great distances, or the fact that some targets are actually designed to sustain very high amounts of thermic energy, like ICBM re-entry vehicles. Also, it has to be taken into consideration that there is no way to stop or control directed energy after it has been released, which might have unwanted effects on other systems in the air or space, like satellites. Overall, it is very likely that DEW will be part of the future battlefield soon, starting with simple targets at short distances but encompassing more complex targets and larger distance over time.
Conclusion
Standardization of sensor data networks and interceptor interfaces can allow a much deeper integration of a variety of weapon systems. This will create improved flexibility in weapon system employment that is directly tailored to the specific mission needs and will create opportunities for smaller Allies and non-NATO nations to contribute to the overall defence. Easier integration of newer systems will also simplify the expansion of capabilities. Considering the rapid pace of developments in radar, networking and computer technology, it would be counterproductive not to take advantage of this progress. These developments give new options for target engagement, alternatives to tailor units to the mission environment and will allow us to leave old SBAMD paradigms behind, subsequently saving money and increasing effectiveness of our forces. The future should be a synergetic and effects-oriented network of C2, sensor and effector elements, with the inclusion of DEW or other methods of energy projection, to ensure a robust and always optimized defence for the Alliance and partners.
