Now, here’s a thing

Whenever powerful new military technologies and the operational concepts and tactics that flow from them threaten to disrupt existing capabilities or lines of development, counters to them are immediately sought. This process is unfolding now as uncrewed systems developers and operators strive to mitigate the potential – and likely soon actual – impact of high-power microwave (HPM) weapons on drone swarms, writes Peter Donaldson.

A key advantage of offensive drone swarms is their ability to overwhelm air defences, for example, by presenting them with targets so numerous as to deplete stocks of missiles and anti-aircraft gun ammunition faster than they can be replenished, and to force the expenditure of very costly intercept missiles – typically, two at each target – against drones several orders of magnitude cheaper in terms of both money and real resources. HPM weapons mounted on ships, ground vehicles and even aircraft could turn this around by frying the electronics aboard multiple drones with each directed burst of radio frequency (RF) energy, consuming only electricity and the energy used to generate it.

The counters to this counter are multifaceted, involving the application of both established and cutting-edge protective technologies, and the adaptation of emerging system-level concepts of operation that themselves rely on other evolving technologies.

Physical protection of drones from this threat is possible but, as always, presents size, weight, power and cost (SWaP-C) challenges, particularly for smaller vehicles. Established technologies focus on electronic hardening with Faraday cages that conduct induced currents around sensitive electronics, plus filters on power and signal lines to block high-voltage surges, for example. The use of optical signalling for internal communication, fly-by-light control and fibre-optic datalinks – the latter now well established in small drones – reduces the attack surface vulnerable to HPM energy.

Nearer to the technological cutting edge is plasma shielding containing charged particles that absorb and reflect incident RF energy before it can harm sensitive electronics. Such plasma shields can be passive, generated purely by the physical interaction in which the HPM energy ionises special gas mixtures – or active, where sensors trigger some combination of lasers, microwave beams and/or electric arcs to ionise a specific block of air between the threat and the vehicle.

However, HPM weapons have a critical vulnerability in that their powerful emissions make them inherently detectable, locatable and therefore open to counter-strikes – if a sufficiently responsive kill chain is in place. Small UAS can form part of this kill chain, particularly when used in swarms, but will require miniature HPM detectors to be developed – within tight SWaP constraints, and demands precise time synchronisation, calibrated receivers and low-latency mesh data links.

Operationally, some or all of the drones in a swarm can serve as expendable sensors. If at least one drone detects an HPM pulse and transmits its last known position it will have fulfilled its mission, even if it is subsequently disabled. Furthermore, swarms can be configured such that some drones survive to guarantee that the position of the HPM threat is injected into the kill chain in time for a networked weapon to destroy it. Inexorably, the endless battle between measure and countermeasure continues.