When it comes to shipping, humans crews are inconvenient. They need places to sleep and to take care care of bodily functions, they probably require food and a place to prepare that food, and they can only work so many hours a day. Also, crewmembers and their accommodations have weight, which means increased fuel costs for ocean-going vessels. All told, it's expensive. If it were possible to move ships to and from ports without humans, shipping could get a lot cheaper, says Rolls-Royce's head of marine innovation Oskar Levander. The future of shipping, much like that of flying vehicles and land-based ones, may well be unmanned.