A container ship can carry up to 24,000 containers. Even if they don't build to the max size, it still takes 1-3 days to unload an average container ship on the shore using the giant container cranes. I can't imagine how long it would take to unload at sea onto smaller vessels but there's pretty much no way it's going to be economical with technology available in the next 20 years.

I agree that the old way of doing things won't work.

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)

It's interesting how further up someone accused people of opposing nuclear energy for ideological reasons and then read proposals like this, which are completely removed from reality.

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?

> Building drones that can lift containers from cargoships requires electricity/energy storage densities that are so far beyond anything realistic.

Nuclear drones!!1one! Problem SOLVED. Gee I'm smart. ;)

>It's interesting how further up someone accused people of opposing nuclear energy for ideological reasons and then read proposals like this, which are completely removed from reality.

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...

Issue number 1 is cost. At $100 per kwh, each of these drones will cost a quarter million dollars (just for the batteries). Also, since each trip will require recharge, if we assume that the batteries can charge at 500kw (which is really high), it will take about 5 hours to transfer 1 container. That seems pretty much untenable.

Cost on its own is rarely an issue. The thing that matters is payback time.

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.

25 MW charging sounds great, but that does restrict you to 4 drones charging at a time per nuclear reactor (comparing to reactors used on carriers), which might be a little bit limiting (not to mention that making a battery that can be charged this quickly without overheating would be a triumph of engineering). Also your example of 12 containers per hour 12 hours a day for 6 months would be 26000 recharges, which is roughly 3x as long as the battery will last given current battery technology. In other words, this workload would require spending somewhere around $1M per year in batteries for a drone that takes roughly 12 minutes to unload a container. For comparison, a port crane, can unload 30 to 50 containers an hour, and will use far less electricity since it is lifting 1/3rd the weight (and isn't hovering).

Yes, the battery lifespan is the big issue (as pointed out in my original post).

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. :)

I know this has been a couple of days ago, but still meant to reply. Regarding your numbers, not that that ~3.5 kW of _power_ density is for 10s when the charge is _at least 50%_. Moving back and forth between two ships is also likely more than 300s, they can't just let the containers drop, they have to be carefully placed. A bigger issue is that you can't just scale the numbers of a 500g battery up to 800kg, I mean just getting the heat away will require significant effort. There is a reason the Tesla battery is ~500kg.

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.

It's one thing to do something completely counter productive like using gasoline powered drones to unload/load your electric ship. It's another to assume that the same capability can even be offered by electric drones.

There is absolutely nothing wrong with port cranes.

Yes, port cranes are much better, if they can be used. The drones are suggested as a potential alternative to handle "LA does not allow nuclear ships to dock", so that a transfer from a nuclear- to battery-powered container ship happens in the international waters.

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.

That site users an image from the movie Airplane to illustrate their autonomous pilot.

How much is that going to cost to develop, manufacture, deploy, train, maintain etc? Shipping is a VERY price conscious industry.

I assume that the majority of the cost would be to design and build nuclear ships. And it's still worth it, as fuel is 50%-60% of operational costs.

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.

In most forms of bulk goods transport the power unit can be decoupled from the part the goods ride in. Seems possible that might also work for ships.

Oh, good point!

Hmm, I consider myself a “rational green” in favor of nuclear power, but I’m not sure I think nuclear reactors operated by foreign companies in a highly competitive industry that booms and busts with tight margins is a good idea.

I share the same feelings. The thing is that these foreign companies won't ask the US for permission. And if it's profitable, they will (eventually) do it.

Yes, such ships will likely have to stay away from the US territorial waters, but there's plenty of routes where this won't be a problem.

As for tight margins: fuel costs represent 50%-60% of overall costs ([1]) and if these expenses are replaced with CapEx (hopefully, benefiting from economy of scale), then the tight operational margins suddenly become amazing, and there's a room for quality.

1. https://www.morethanshipping.com/fuel-costs-ocean-shipping/

> Yes, such ships will likely have to stay away from the US territorial waters

if it turns out that such shipping via nuclear reactors is much more cost efficient (including all currently externalized costs such as emissions), then the US will have no choice but to accept it - or be uncompetitive in the global markets.

I’m with you. It’s why I don’t look forward to autonomous airplanes. I firmly believe airlines would have “acceptable losses” that include passengers if they didn’t have two really hard to replace people sitting in the front.

Maybe I’m too jaded these days.

Fair point but what about a Chinese nucular boat from one Belt and Road port to another

Why though make batteries the size weight and shape of shipping containers charge them in ports then the ships can replace empty batteries with charged batteries just like they do containers. I think the world would prefer that over a few thousand nuclear powered ships 1 ship wreck away from making the world sea nuclear contaminated. Which if you understand the water cycle would mean the whole world is nuclear contaminated

I don't think you realize just how big the sea is and how good it is at containing radiation. Heck, we're even figuring out how to mine uranium from seawater, because it's already in there.