98 Of all the different types of military mission being tackled today by uncrewed systems, anti-submarine warfare (ASW) is arguably the most complex. To detect and help defend against some of the stealthiest and most dangerous vehicles on Earth, navies are increasingly leveraging a broad array of highly advanced autonomous systems across air and sea. Diesel-electric submarines in particular are extremely silent and hence difficult to detect compared with nuclear submarines, and although the former would traditionally have to surface every few days to take in air, hybrid and electric powertrains for submarines are becoming more efficient. There is increasing availability of air-independent hydrogen-fuel cell powertrains, such as those made by Infinity Fuel Cell (Issue 47, December 2022/January 2023) or used by Cellula Robotics in its long-endurance, extralarge uncrewed underwater vehicles (XLUUVs) (Issue 30, February/March 2020). This is enabling submarines to travel silently underwater for extended periods of time and power longerdistance sensors for 3D-modelling subsea targets up to 1000 km away at very high fidelity. Such distances make detecting targets even harder, so submarine crews will find it increasingly easy to spy on and eventually attack foreign assets with impunity unless someone can engineer a new type of subsea passive antenna capable of detecting them. Such an antenna would need to pick up ultra-low frequency (ULF) signals of 0-100 Hz, as the lower the signal’s frequency, the further it propagates (resolving the issue of distance by detecting the lower part of submarines’ noise spectrum). To overcome the painfully low volume of such noise, the antenna would need to be massive: picture the size of antennas presently used by astronomers to study celestial phenomena across the galaxy and you’ll have an idea of the scale needed. So, how does one build such a huge antenna, and still cover the vast swathes and different directions of ocean across which hostile submarines may hide without utterly draining their defence budget? The answer, says Thierry Brizard, president and co-founder of Arkeocean, is to create a swarm of autonomous micro-AUVs, which, through their collective hydrophones, form a giant April/May 2024 | Uncrewed Systems Technology Rory Jackson reports on a firm using a group of autonomous micro-AUVs to hunt and find hostile submarines Swarm tactics French AUV manufacturer Arkeocean’s micro-AUVs work together as a sparse antenna for cost-effective antisubmarine monitoring (Images courtesy of Arkeocean)
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