No, they often fly private jet which makes commercial First Class look like steerage.
Now, there are times when flying makes more sense than other modes of transportation, but that’s usually due to either time or security being a major factor.
I don’t think humanity is going to give up flight. I do think we might have a future where it’s more expensive and less common if we can find acceptable alternatives for most people traveling.
I think another problem is the square-cube law. Something the size of an ocean liner or giant container ship is too heavy to be a practical sailing ship.There’s a reason these replaced clipper ships despite the difference in fuel costs.
A ship twice the dimensions is 8 times the weight, but can only present 4 times the sail area - not to mention the issue of building masts tall and strong enough (and braced enough) to handle that amount of wind pressure. OTOH, it can carry 8 times the cargo. There’s a limit to how big a sailing ship can get. Maybe the future is thousands of small autonomous container sailing ships, all computer controlled.
Mass to thrust only matters for acceleration, and while big ships are slow to accelerate compared with a car, it still makes very little difference over a long trip: The time to reach maximum speed is small compared with the total trip time. And what determines maximum speed is the thrust and the drag forces, and drag will also mostly be proportional to dimension squared. In other words, a ship of twice the dimensions will have four times the sail area, and also push against four times as much water, so should have a comparable top speed (slightly lower, because there’s also viscous drag, but that’s not as large).
That’s true for sailing from Shanghai to Antwerp, but those big ships often make several port stops at each end of the journey. A 1 day trip is going to be all acceleration, and a 48 hour trip is going to be 50% acceleration.
Or so I was told. Maybe somebody who’s recently served on a container ship could comment?
Seems unlikely, just from the basic physics. The Emma Mærsk produces 99 MW on the main shaft. Fully loaded (157,000 t, approx), and at top speed (13.1 m/s), it has 13.5 GJ of kinetic energy. It needs only 136 s to produce the energy needed to reach that speed.
Obviously, significant portions of the power go to fighting drag, producing a wake, etc., but you’re saying this figure is off by a factor of 600. I have a hard time believing that less than 0.2% of the prime mover power actually goes into increasing kinetic energy.
I don’t know: that’s what I was told by a ex-ships-engineer: that it takes all day to reach full speed.
He didn’t say that it was a limitation of how much power the engine could produce.
I explored around on marinetraffic.com, and while it’s a bit hard to find examples (especially with a free account), it didn’t take too much time to spot this one:
https://i.imgur.com/do2uhyb.png
Just a couple of hours out of port and it’s at 19.4 kn. Based on the speed it would take a little over two days to make it from PEF to NYC, which is inline with the estimates here (I’m guessing that link will do out of date pretty quick though). It’s not the biggest container ship around but it’s not tiny, either.
Maybe your friend was talking about some specific situation which doesn’t apply universally. But overall I can’t really believe that big ships usually spend the first day accelerating. Especially since it seems easy to find counterexamples.
The speed curve would be somewhat asymptotic though, wouldn’t it? Initially the energy would almost entirely go into speeding up, but then more and more would be lost to drag. Not saying 1 day wouldn’t be an exaggeration, but it could be the first 90% goes relatively quickly and then it takes subjectively “forever” for the remaining 10%.
This assumes they always cruise at the absolute maximum possible speed, which seems unlikely. A SWAG on my part is that they might accelerate with the engine set to a power output that gives maximum engine efficiency - and then reduce power a bit to hold a steady cruise speed that gives the most economical tradeoff between ton-miles per gallon and shipping time (i.e. you can probably get very good ton-miles per gallon if you cruise very slowly, but your profitability falls off if you don’t cover very many ton-miles per day).
Cavitation may also limit how fast they can accelerate while at very low speeds. Would be interesting to hear from a container ship captain/crew on management of speed/acceleration.
I considered mentioning that, but figured I was already making semi-educated guesses far outside my knowledge. Though I did once attend a three day seminar on designing and testing cargo-ship models.
I specifically noted that a cruise ship is moving and pointed out that it is the main difference.
