In the 19th century steam took over from sail. After all a steamship could travel much faster than a sailship and wasn't at the mercy of the weather the way a sailship was.
Then in the early 20th century the Diesel engine replaced the steam engine. After all it provided far more power than steam and didn't require constant attention from the crew the way the coal burning steam engine did.
Today we are in an era of huge ships. Cargo carriers ranging from 200 to 1000 tons. There is talk of fitting these huge ships with nucelar reactors in the future.
Is it feasible? Well many navies have done it with warships. First nucelar powered submarines then aircraft carriers. And modern reactors are relativly safe. When that Russian nucelar sub Kusk sank in the Arctic it didn't poison the water cause the reactor is designed to shut down if the ship sinks. Early reactors in Russian and Chinese subs were dangerous to the crew but have since been much improved.
Could the nucelar reactor be the future of ocean transport?



