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Comment by raffael_de | Hacker News Reader

my first association here would be steering of torpedoes. the US Navy must have been on this for decades and very deep pockets.

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Torpedoes are usually steered using fibre-optic wires, like the fibre-optic drones in Ukraine today, so there is no need for problematic low-frequency radio.

Terminal homing phase sub-torpedo drone swarm use case for this ? ;-)

As funny as your comment sounds, I wouldn't rule out the Ukrainians actually doing it. At least for sea+air and air+air, sub-drones are already a reality.

Yeah, there is at least one case where they (critically ?) damaged a Kilo class submarine using an underwater drone last year:

https://en.defence-ua.com/news/why_damaged_russian_kilo_clas...

Navies are known to use low frequency radio to send messages to submerged subs.

But isn't torpedo steering still dependent on wire?

The issue is it doesn't really matter and radio isn't much benefit: you get much higher bandwidth, better reliability, immunity to ECM, and fiber-optic wires in Ukraine are over 50km long.

The exact application for this is autonomous underwater vehicles where what you would like to do is communicate quickly and without a tether in arbitrary scenarios - i.e. think a bunch of autonomous vehicles which might need to relay a message or communicate with dropped assets. Using radio in those scenarios solves the problem of a consumable (the wire), and also the problems associated with sonar like fouling of the array.

fair enough but afaik torpedoes aren't tethered by a fiber optic cable like drones. it's a much thicker cable that possibly contains a fiber optic cable.

Right but they're heavier with far fewer weight concerns then an aircraft. Torpedos are large, heavy and expensive.

The point is a very thin wire had a surprisingly long range - versus this system which has a very low bitrate much past 1km.

For an active weapons system it's just not a great choice when you already have the wires and they work.

But for sensors or vehicle meshing, where you can't lay wires in advance? Potentially huge.

This uses the same principle, but the traditional method required immense antennas and very high power radio transmitters.

Such antennas and transmitters cannot be installed in a small submarine.

Here a new kind of antenna is used, which is efficient under water even at small dimensions, so it can be installed in small submarines, for communication at distances of up to a few hundred meter.

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