Advanced multistatic sonar: a high-potential option for anti-submarine warfare (ASW)

ASW: the resurgent discipline of the 21st-century

ASW has come roaring back onto naval agendas in recent years. Three decades ago, only a handful of major powers had effective submarine capabilities but, today, fleets in operation around the world are growing rapidly. It’s sobering to think that emerging superpowers, like China, can add naval capacity equivalent to a European country’s in the space of a few years.

The threat from submarines is serious and ever-more difficult to counter. They can block a key trade corridor, destroy a high-value asset, and deliver devastating land strikes. What’s more, streamlined designs and quieter propulsion encourage forays into previously impenetrable zones.

Multistatism: a robust naval response to new ASW realities

Navies are responding to this resurgent threat, demanding better technology and more collaborative ASW. Anti-submarine warfare has always been a team effort, but, today, a major enabler is the concept of multistatism. This involves one (or more) active emitters, a host of passive receivers and (potentially) a range of platforms.

Provided the “team” coordinates its behaviour carefully, only the emitter will be visible to an invasive submarine—a significant advantage. As a result, the effectiveness of classical evasion manoeuvres, like minimising the surface area facing sonar, can be rendered a game of chance. But, for all its potential, multistatism is no panacea. The challenges are immense.  All the sonar in use must be fully interoperable; they must be able to seamlessly exchange information for synchronisation and processing; and environmental conditions (like salinity and temperature) must be known over large areas if data is to be interpreted accurately. In the face of this, sonobuoys can offer an advantage: fixed in position and able to transmit information to a single aircraft, they can, among other things, easily solve synchronisation issues. It’s perhaps no surprise that, with increasing submarine activity and advancing technology, navies are taking a keen interest in sonobuoy multistatism.

SonoFlash: a major step forward in sonobuoy multistatism

Multistatism has reached buzzword status in naval circles, but in reality the road to using it robustly will involve gradual steps forward. Aware of its challenges, navies are looking for sea-proven solutions—not mere technical possibilities. Yet, the next step forward may be a big one, as Thales unveils, at Euronaval 2018, a next-generation sonobuoy: SonoFlash. Its cutting-edge design incorporates a set of characteristics that bring the future of multistatism a step closer. First, advanced features: today’s sonobuoys are either active or passive, but SonoFlash combines both—a powerful emitter (that can descend to depth), and a high-performance, low-frequency, passive sensor.

What’s more, it’s designed for long endurance, transmits real-time information for airborne processing, and, thanks to its multipurpose capabilities, will be an acoustic sensor of choice for tomorrow’s UAVs.

Second, it’s fully interoperable with other Thales sonar families. Together, these features make it highly flexible, opening up a range of new tactical options. A field of SonoFlash buoys, each able to emit and listen, can be combined with each other, and other powerful platforms—like Thales’ Captas or Flash—in a menu of permutations. Such advanced sonobuoy multistatism can’t eliminate the threat from modern submarines, but its combination with other advancing sonar platforms, and powerful processing and HMI tools (such as Thales’s BlueTracker), could make serious inroads into mitigating it