[siod]

I love the concept of submarine cargo ships but there are three main issues that make them less appealing than ships.

Subs require significantly more thrust per cubic metre of cargo.

Communication and navigation are more difficult because GPS and satellite comms don't work underwater.

Loading and unloading in comparable times to a standard container vessel.

[BoxOfRain]

>Communication and navigation are more difficult because GPS and satellite comms don't work underwater.

That's a really good point, how do you get a signal to a submerged unmanned submarine under all that conductive saltwater? Military submarines use VLF radio waves that can penetrate saltwater fairly deep, but those long wavelengths require enormous aerials and powerful transmitters that are one thing if you're the navy of a nuclear power, quite another if you're a shipping line looking to make a profit.

[nradov]

Submarines can't transmit on VLF bands. They can only receive from land based transmitters.

[lowestprimate]

One of the reasons to use quantum gyroscopes is that will be accurate to within 1m or so after a day long underwater traverse of 1000 km or more. Communication while fully under still sucks though.

[femto]

Powerful lasers, as used by laser depth sounders, will penetrate water to an 80m depth [1]. Might be possible to do a laser link directly to an overhead UAV or satellite? If they are following regular shipping lanes, it might be possible to have communication buoys (or nodes on the seafloor connected by fibre/cable) at regular intervals along the route, with laser or sonar communications to passing submarines. It would be a bit like "sections" of track in railways, with vehicles checking in as they enter/leave each section.

[1] https://www.navy.gov.au/ran-aviation-history/laser-airborne-...

[jhgb]

Surely a GPS mast shouldn't be a problem? And an IMU may be more expensive than a GPS receiver, but compared to the cost of the whole vessel, it's probably negligible.

[siod]

Yeah a mast or tethered transmitter probably they way to go, but now you have the problem of operating both a submarine and a pseudo surface vessel.

Nothing insurmountable, but it's not as simple as running under everyone which is what the article implied (to me atleast).

[tgb]

Doppler velocity log is likely what they'd want.

[newsclues]

Less turbulence to move the cargo, which could lead to less breakage.

If subs are designed for cargo then unload/loading operations can be optimized.

[munk-a]

Deep water subs require serious fixed reinforcement (like gigantic periodic rings) to prevent being crushed at low depths that would stop you from easily exposing the interior for unloading - but given that they're only going 50m deep I'm sure you could have some mechanism to pop the sub in half and get all the access you need. I feel like turbulence is sort of a solved problem by way of pallet packing - but that actually raises a larger concern of mine - the sub they display is pretty tube-shaped which means it's either not going to use pre-packed pallets (definitely the case if the image shown is to scale) or it's not going to use pre-packed pallets efficiently. Habours leverage pallets to minimize the manual labour needed for loading/unloading so while the ship might open like a sardine can it's not going to see a lot of use if someone needs to lift boxes out of it one at a time.

[femto]

If there are no people on board, couldn't the air pressure be boosted to match the external water pressure?

If the pressure is balanced, removing the need for a pressure hull, the sub could have a more rectangular cross section, allowing it to be packed full of regular shipping containers.

[belorn]

I am not sure how thick the reinforcement actually need to be in order to comfortable cover the minimum 6 atmospheres of pressure at 50m. My intuition with diving gear tells me its should not be that bad, but I don't know how much things scale with volume.

[newsclues]

Missile subs have large vertical tubes that can quickly be unloaded and loaded with a crane. If a sub can have big missiles you can pack it with pallets of bottles