[ShabbyDoo]

Most of the comments here presume that it's unacceptable for a drone ship to break down in the middle of the ocean and be without crew to repair it. What if these ships were designed so that nothing too awful would happen if they floated around in the middle of the ocean for awhile awaiting another ship with a human crew to perform repairs. Or, maybe another drone ship or two to tow a broken one back to land?

My understanding of container shipping is that customers make SLA choices much akin to us Americans choosing between UPS Ground/2nd Day Air/Next Day, etc. UPS uses these varied SLAs to smooth out its use of fleet capacity and for price discrimination. Shippers operate transshipment ports as part of distribution networks much like the hub & spoke designs of the major airlines. These ports have a bunch of shipping containers sitting around awaiting capacity.

Consider the needs of companies that must transport low-value, high weight/bulk cargo. These companies likely already choose the "UPS Ground" equivalent for container shipping. Due to low product value, inventory costs are low (in transit goods are inventory), so it's probably less expensive to have buffers of goods in the supply chain than it is to pay for tight shipping SLAs. Why should these companies care if the variance they experience in shipping duration is due to capacity constraints of manned-ships or that it took an extra two weeks to fix the ship upon which their cargo was in transit?

[LeChuck]

It very far from certain that a ship without propulsion will just stay afloat for a while. Even big ships can disappear in a hurry if the weather's bad enough.

See for example the sinking of the Derbyshire. http://www.youtube.com/watch?v=9tN4xROtMjI