How about hundreds of cargo drones capable of lifting containers to transfer them from one ship to another? Something like this: https://www.cognitiveseeds.com/395-2/
Don't forget - a nuclear-powered ship that's not moving has a lot of free electricity: enough to charge all the drones (likely, bearing supercapacitors, as their flight from one ship to another will be very short)
Building drones that can lift containers from cargoships requires electricity/energy storage densities that are so far beyond anything realistic. A container can weigh up to 28 tonnes, there was exactly one helicopter that could carry this kind of load the Mil Mi-12 and that looked really more like a plane. Moreover if we would have those kind of densities why would we even use nuclear ships?
Nuclear drones!!1one! Problem SOLVED. Gee I'm smart. ;)
Let's see. There are two variables here in regards to power subsystem: power and energy capacity. Let's start with the power:
>A container can weigh up to 28 tonnes, there was exactly one helicopter that could carry this kind of load the Mil Mi-12 and that looked really more like a plane.
According to ([1]), we need around 0.28 kW/kg of thrust. Assuming that the drone weights twice more than a container, we need to have a lift of around 84 tonnes-force minimum, and ~100 tonnes-force in reality. That translates to 0.28 * 10^5 kW = 28 MW. This is close to what Mi-12 had (19.2 MW).
LTO batteries from Toshiba ([2]) advertise 3.5 kW/kg of energy density, which gives us 28 MW/3.5 kW/kg = 800 kg of batteries. Reasonable, given that our budget for drone dry weight is 56 tonnes.
Let's consider the energy capacity. To transfer a container from one ship to another standing 200 meters apart moving at 10 km/h, we would need 144 seconds for roundtrip. Let's make it 300 seconds for redundancy.
28 MW * 300 seconds = 2333 kWh. At 84 Wh/kg ([2]), we get 27.8 tonnes of batteries. Not great, but within out weight budget of 56 tonnes.
The gotcha here that I see is the longevity of these batteries (they are rated for 8000 cycles). Do you see any other issues? I mean, basic physics seems to allow for such drones (not saying it's trivial to make).
1. https://store.tmotor.com/goods.php?id=974
2. https://www.electrive.com/2022/01/12/toshiba-presents-new-20...
If one container move generates $10, and the drone moves 12 containers per hour, 12 hours a day, it will only take 6 months to earn the quarter of million mentioned.
Also, it might actually sound like a very cheap option compared to the ship-to-shore container cranes, which cost $20M-$40M each: https://www.freightcourse.com/port-cranes/
As for recharging: if our power train is 28 MW, why not charging it at the same speed as we discharge it? Why settle on 500 kW, which is really low? For comparison, Tesla supercharger is up to 300 kW, and a car is a much smaller EV.
As for charging at 28 MW: might work, given that the battery is physically larger, so there's more space to dissipate heat. I agree that it's not proven by the napkin math that it's doable.
What I really suspect is that if Los Angeles refuses to accept nuclear container ships, Mexico would let them in, and then the regular railway will be used to move them to the US. A much simpler solution. :)
But the biggest issue is is recharge, you can't recharge every 5 min. I mean how many of those drones are you going to employ? I mean a panamax class ship has 5000 containers. So either you need 5000 of those drones (good luck with them managing the off-onloading in 5 min) or some small subfraction, which then need to be recharged. Even if we assume we need to only move 500 containers (and use 500 drones), That means we either need to recharge 500 2333kWh batteries in 300s, how are you going to do that out on the ocean, or more likely you have 5 drones operating which need to work for 100 times as long, which increases you weight by 100. It just doesn't add up.
There is absolutely nothing wrong with port cranes.
As for can be offered: we're talking about moving a container from ship to ship which stand just hundreds meters away. The physics / math works, see my other comment.
As for drones to handle cases of ports which don't allow nuclear ships to dock: this is just a potential workaround. I kind of guess, that they will just focus on other ports first, and then eventually (like, in 5-10 years timeframe) everyone calms down and just allows such ships to dock in LA / NY / other US ports.