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Comment by beerandt | Hacker News Reader

Usually auv means no cables, and rov means tethered, but they describe their unit as auv/rov.

So not sure of this specific setup, but for most auvs there are hipap integrated acoustical modems with limited transmit / receive rates, for critical status messages and a control link. Everything else is held on hdd until it surfaces.

https://www.kongsberg.com/maritime/products/Acoustics-Positi...

In the event of a comm disconnect, it probably has a limited amount of instructions to continue carrying out (like surveying to the end of the current grid line) and then holding for a limited amount of time before aborting to the surface. If a connection can be re-established, it continues. It's also possible to have navigation connectivity without 2 way comms, so there are different abort scenarios possible.

If it aborts to surface, then you've got amplified wifi, sat phone, and even an eprb type beacon.

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Abort to surface seems non-trivial in a situation where you're hella deep under a thicc ice shelf. I wonder what sort of failsafes they've got in place to handle that particular situation.

Yeah, I thought about that- my experience was in warm water, but we did have certain infrastructure pre-programmed to avoid. We'd call it geofences today, but I'm not sure it had a term then.

You could hope for a semi-operable abort, and leave an acoustical beacon out to the side of the glacier to home on. Sort of a "proceed to x, then abort to surface".

There are stories though, of when the navy was initially testing this tech ~20+ years ago, of having to basically keep mini-subs and full time salvage crews on standby, for all the times the things would get their nose stuck in the mud.

They quickly came up with a front facing acoustical Doppler sensor for terrain collision avoidance. Even then, it sometimes backfired, like steering up into the face of a cliff, instead of turning laterally.

But maybe that's the reason for the /rov tethered configuration.

if (hellaDeep && iceShelf.isThicc) { // TODO }

You are right that abort to surface is non-trivial.

I didn't work on Icefin, but I did write the comms-lost procedure (among many other things) on a previous ROV/AUV that was deployed in Antarctica to go under the Ross ice shelf. Britney Schmidt (one of the investigators quoted in the article) was the PI of the grant for that project as well.

Our AUV was deployed through a hole drilled in the sea ice and controlled via a fiber optic cable. It was used as an ROV in most circumstances, although we could preprogram an entire mission to be carried out autonomously. In the event of the cable breaking the submersible had to navigate via dead reckoning to get back within range of the acoustic beacon at the deployment spot. The AUV would follow the acoustic beacon until it was within visual range of a flashing led rod and then use computer vision to guide the AUV into docking on that rod so it could be recovered.

If an error occurred under sea ice then we could surface and bring out heavy equipment to drill a new hole to recover, but the ice shelf was too thick to drill through. We did have a magnetic beacon on the AUV that helped with location if we needed to recover after a failure under sea ice.

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