
Cargo ships that ‘liquefy’ (2018) - ClintEhrlich
http://www.bbc.com/future/story/20180905-the-cargo-ships-that-liquefy
======
killjoywashere
This problem is well understood in naval architecture. Some good engineering
articles:

[https://en.wikipedia.org/wiki/Free_surface_effect](https://en.wikipedia.org/wiki/Free_surface_effect)

[https://en.wikipedia.org/wiki/Metacentric_height](https://en.wikipedia.org/wiki/Metacentric_height)

tl;dr version as I recall: keep holds either mostly full or mostly empty, make
assymetric holds and tanks, and use baffles if you have no other options.

~~~
gingabriska
But it seems it can be easily solved having dividers in cargo compartment.

Think of box with a grid inside it

Once the cargo is filled

The grid lines are raised (hydraulics) which compartmentize the whole cargo
into blocks.

Invidual compartment will not have enough mass of material inside it to break
the dividers if designed properly.

~~~
dsfyu404ed
Sounds expensive and complicated.

It's probably cheaper to just have baffles and vacuum the cargo out.

The status quo is cheaper still

------
dwater
Reposted by the BBC from The Conversation:
[https://theconversation.com/mystery-of-the-cargo-ships-
that-...](https://theconversation.com/mystery-of-the-cargo-ships-that-sink-
when-their-cargo-suddenly-liquefies-101158)

Discussion of the original article:
[https://news.ycombinator.com/item?id=17884382](https://news.ycombinator.com/item?id=17884382)

~~~
ClintEhrlich
Funny, I posted this today specifically because HN prompted me to.

Not sure what led to my submission of the BBC article from 10 months ago being
targeted for a re-post.

But thanks for the link to the earlier discussion!

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crummy
Is this the same process that doomed the supply rocket to Mark Watney in The
Martian?

~~~
jschwartzi
Pretty much.

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err4nt
This might be a stupid question - but could ships tug or tow their cargo, and
let it roll around?

~~~
hirundo
I'd think that towing anything in violent weather would be dangerous. If self
propelled rather than towed your idea becomes a merchant submarine. That would
have to greatly complicate things and be slower and/or use much more fuel.

~~~
gpm
It doesn't have to be underwater to be either towable or self propelled. See
the other comment about barges on the Mississippi for towing and SpaceX's "of
course I still love you" (and friends) for self propelled.

Autonomous and underwater would be hard, radio doesn't travel well through
water.

~~~
TeMPOraL
> _Autonomous and underwater would be hard, radio doesn 't travel well through
> water._

You mean "remote-controlled and underwater"? As "autonomous" kind of implies
not being in need of constant communication.

~~~
gpm
No, I mean autonomous too. Autonomous vehicles still want access to GPS, you
still want to know where your stuff is, you still want to be able to give new
orders if something changes, etc.

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ohazi
What about anti-slosh baffles?

~~~
CalChris
A Panamax bulk carrier already has seven cargo holds.

------
Scoundreller
> about the possible liquefaction of the relatively new solid bulk cargo
> bauxite (an aluminium ore).

Is bauxite really new cargo? Or do they mean ship-operators need to be careful
when switching to bauxite cargo?

And any particular reason for loading these cargoes with water? Why not dry?

~~~
Brian_K_White
At a guess, it's probably easier to pump slurry than to shovel dry material.
Maybe also dust.

~~~
raws
Sounds like they may want to remove water out of the cargo for transport and
pump it back in for unloading

~~~
nicthesailor
Yes for the first part, but we definitely don't want to pump it back in for
discharge.

Dry bulk cargo is almost always discharged with grabs and cranes, not pumps.

------
zcat
video demonstrates this
[https://www.youtube.com/watch?v=zdyrQSypPBQ](https://www.youtube.com/watch?v=zdyrQSypPBQ)

------
nbevans
Why not pump the 'water' out of the bulk into a separate containment vessel.
This way the ship's crew could neutralise the risk without reducing the weight
of their cargo. When unloading they can give back the 'water' component of the
cargo separately. So the weight of the cargo is basically unchanged.

~~~
RWSen
Because the water would need to be separated from the sand grains. The "water"
in the sand is very little: it's more akin to damp sand we're talking about,
or in the "wettest" case mud.

Drying that would require a lot of area, effort, and sun, or some type of
oven. Any method of making sand drier costs orders of magnitutde more than the
sand itself.

------
ulrikrasmussen
Can't cargo hulls be compartmentalized to alleviate this? Or are the forces
too great for this to be practical?

~~~
simonh
Compartmentalisation is fine for liquid cargoes, but make it a lot harder to
load and unload particulate solids like these because the walls and baffles
get in the way.

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rolltiide
well that's terrifying

the cargo containers should just vibrate the whole time to keep things in
liquefied state throughout the whole trip.

~~~
uponcoffee
The amount of energy to vibrate 25-25000 tonnes for any extended duration of
time would be staggering. Then you have to manage forces this subjects the
ship to... maintence would be a fright

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xyzzy_plugh
why on earth does bbc.com redirect to http from https??

~~~
hexadec
Because they like to verify the integrity of the data they send you and HTTPS
should be the default for all web traffic possible.

[https://https.cio.gov/everything/](https://https.cio.gov/everything/)

~~~
bzbarsky
Yes, but the point is that if you load it over HTTPS they will redirect to
HTTP. So if you type [https://www.bbc.com/future/story/20180905-the-cargo-
ships-th...](https://www.bbc.com/future/story/20180905-the-cargo-ships-that-
liquefy) in your web browser url bar, you will end up at
[http://www.bbc.com/future/story/20180905-the-cargo-ships-
tha...](http://www.bbc.com/future/story/20180905-the-cargo-ships-that-liquefy)
instead. That's the somewhat-surprising part.

------
mlurp
Interesting article, but the sporadic bolding of a few words is killing me:

>The International Maritime Organisation __has codes __governing...

~~~
DoreenMichele
Based on a spot check of some of the bolded words, bolding seems to be used
here to highlight links.

The old way of indicating "this is a link" was underlining. That seems to have
largely fallen out of favor and most websites seem to use color coding these
days.

~~~
mlurp
Ahhhh, that makes sense. I'm on mobile. The choice of "bolded" words seemed to
make no sense...

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JackFr
Add rice to the hold. Problem solved.

[https://en.wikipedia.org/wiki/Mr._Midshipman_Hornblower](https://en.wikipedia.org/wiki/Mr._Midshipman_Hornblower)

"Hornblower and the Cargo of Rice"

~~~
DoreenMichele
Is this just a joke? If not, do you have a better source to back up the
suggestion?

I'm asking because it's a fictional story and the sink ships because of the
wet rice expanding. It doesn't actually save the ship, though it does likely
delay its demise.

~~~
m463
It must be a joke because the rice took down the ship.

~~~
DoreenMichele
That's what I'm guessing, but I know basically nothing about cargo ships. I'm
googling around to see if there are any potential prevention methods along the
lines of "just add a bit of rice to your ore..." 0_o

~~~
m463
I would assume if you dropped your cargo in water, putting it in rice should
dry it out. Like your phone...

