> Liquid hydrogen is less than 1/3 the energy density of diesel by volume Yes, but in a ship volume is not a concern. > Liquid hydrogen also has difficulties

> Liquid hydrogen is less than 1/3 the energy density of diesel by volume Yes, but in a ship volume is not a concern. > Liquid hydrogen also has difficulties in terms of converting that energy into work Check [1] out. Current diesel engines can be retrofitted to burn a mix of diesel and hydrogen that reduces emissions by 86%. “If you just put hydrogen into the engine and let it all mix together you will get a lot of nitrogen oxide (NOx) emissions, which is a significant cause of air pollution and acid rain,” Prof. Kook says. “But we have shown in our system if you make it stratified – that is in some areas there is more hydrogen and in others there is less hydrogen – then we can reduce the NOx emissions below that of a purely diesel engine.” > Again nuclear powered shipping has already existed for decades. The better part of a century, in fact. Piracy and rogue states have not been a problem. Nuclear powered warships have existed for decades. Civilian nuclear power ships were a rarity. Most were Russian icebreakers, operating in the arctic, where pirates are quite hard to find. The idea you are proposing is to start putting nuclear reactors on thousands of ships that would criss-cross the world's oceans on a daily basis. It's just not going to happen. And if you want to put them only on a handful, why bother? They won't make a dent in the emissions. [1] https://newsroom.unsw.edu.au/news/science-tech/new-system-retrofits-diesel-engines-run-90-cent-hydrogen https://newsroom.unsw.edu.au/news/science-tech/new-system-re...