Size and Weight of Ships

[pigboy1537]

In Travellers I was interested on the size and the weight of ships to get a prospective on how big was big. I Googled ocean going ships to see if they had a comparison and I found this.

It give you a size chart to compare to the star ships in Travellers.

 

[AnotherDilbert]

grt or Gross Register Tonnage is not mass, it is basically volume. 5 grt ≈ 1 Traveller displacement ton.

E.g. the Jahre Viking at 260 000 grt (Traveller: 52 000 Dt) would mass about 650 000 tonnes fully laden or 83 000 tonnes completely empty.

 

[Xerxeskingofking]

as Anotherdilbert says, the Gross Register Ton, the traveller Displacement Ton, and the short/long/metric Tons of weight are all different, and not interchangeable.

a real worlds ship displacement tonnage is also different form what its traveller DTonnage would be, RW tonnage is based on the volume of water displaced by a floating ship, where as traveller tonnage is the volume of Liquid Hydrogen displaced by a fully submerged ship.

since Lhyd is much less dense than water, the volume displaced for a "ton" is bigger, and since its the total volume of the ships enclosed spaces, not just the volume of the ship below the waterline, the two measures are very different.

 

[mike wightman]

A GRT is 100 cubic feet, as AD points out a unit of volume. It is the total volume of the ship in cubic feet equivalence.

A Traveller dt is 500 cubic feet a unit of volume (very few Traveller rule sets have even tried to pin down the mass of the ship).

So if you want to compare the above ship sizes to Traveller ships just divide their GRT by 5 and you get their volume in T dt. Since both the GRT and the T dt are units of volume all you need is the conversion factor.

 

[Xerxeskingofking]

A GRT is 100 cubic feet, as AD points out a unit of volume. It is the total volume of the ship in cubic feet equivalence.

A Traveller dt is 500 cubic feet a unit of volume (very few Traveller rule sets have even tried to pin down the mass of the ship).

So if you want to compare the above ship sizes to Traveller ships just divide their GRT by 5 and you get their volume in T dt. Since both the GRT and the T dt are units of volume all you need is the conversion factor.

what he said,


I realise I was mixing up a real world ships displacement and traveller displacement, which differ in the ways I mentions, but I forget that GRT is just a volumne measurement, and can be directly converted.

to put those ships into a traveller context the Jahre Viking, at 52 Kdt, is about "heavy cruiser" sized, or 50-25% of the average BB (assuming 100-200KDt BBs)

 

[kilemall]

Freelance Traveller article on the topic-

https://www.freelancetraveller.com/features/shipyard/tonnage.html

 

[pendragonman]

A GRT is 100 cubic feet, as AD points out a unit of volume. It is the total volume of the ship in cubic feet equivalence.

A Traveller dt is 500 cubic feet a unit of volume (very few Traveller rule sets have even tried to pin down the mass of the ship).

So if you want to compare the above ship sizes to Traveller ships just divide their GRT by 5 and you get their volume in T dt. Since both the GRT and the T dt are units of volume all you need is the conversion factor.

TNE/FF&S works with mass somewhat.

 

[Brandon C]

TNE/FF&S works with mass somewhat.

GT uses mass, in particular in determining acceleration of a ship (thrust/mass).

 

[infojunky]

TNE/FF&S works with mass somewhat.

As does MegaTraveller...

 

[Timerover51]

The USS Nimitz full load displacement of 95,000 tons reflects the mass of the carrier when fully loaded for a combat mission, and does not reflect the volume of the ship whatsoever in terms of gross register tonnage. What it does reflect is that 95,000 tons of salt water, at a nominal volume of 35 cubit feet per ton, is displaced by the underwater portion of her hull. As a carrier has a large amount of open space inside of the hull for the hanger deck, a possible gross register tonnage for the ship might be 2 to 3 times its full load displacement tonnage.

For those concerned with how much a ship masses based on its Traveller Displacement tonnage, the World War 2 Liberty ship was roughly 1400 Traveller Displacement tons by its gross register tonnage, and massed about 3200 tons light ship, which would be the condition of the ship ready to sail but without cargo, stores, or fuel. If you assume the hull made from the equivalent of 20 pound per square foot steel plate, so not armored, a Traveller ship without cargo or fuel could be view as massing in metric tons 2.0 to 2.5 its tonnage in Traveller displacement tons. So a 200 Ton Free Trader might mass, empty, between 400 and 500 metric tons. A passenger ship is going to mass a bit more than a cargo ship because of the passenger spaces onboard, compared to open cargo holds.

As for cargo, you can assume between 5 and 15 metric tons per Traveller displacement ton of cargo space. Five tons per Traveller displacement tons would be equivalent to a general food cargo of preserved foods. Twelve tons would be equivalent to a general cargo of ammunition. Fifteen tons and higher you would be looking at ore or processed metals. That would be about right for wheat carried as grain as well.

 

[Brandon C]

In GT, most merchant ships come in at 2.5-3.5 stons per dton (average cargo is 5 stons per dton) and most warships 5-10 stons per dton. Other ships are quite variable, but 2 stons per dton is common.

 

[infojunky]

As for cargo, you can assume between 5 and 15 metric tons per Traveller displacement ton of cargo space. Five tons per Traveller displacement tons would be equivalent to a general food cargo of preserved foods. Twelve tons would be equivalent to a general cargo of ammunition. Fifteen tons and higher you would be looking at ore or processed metals. That would be about right for wheat carried as grain as well.

Actually your upper end is a bit too high.... A dTon of grain is about 10 tonnes. But reasonable mass to volume ratios for cargo pretty much tops out about water or 13 tons per dTon. But that is do to limitation of the equipment not the actual density of what is being moved. When they ship gold ingot its 3 or 4 pallets chained down in the middle of a much larger container... Figure 7.5 tonnes per dTon is you average maximum cargo mass...

 

[kilemall]

This image is out there for comparing Traveller ships- no guarantee as to accuracy.

http://i31.photobucket.com/albums/c362/waynepeters/Trav_Ships_plus_TOS.jpg

Photobucket of course is monetizing hotlinking, we'll see if this will display.

 

[Carlobrand]

Actually your upper end is a bit too high.... A dTon of grain is about 10 tonnes. But reasonable mass to volume ratios for cargo pretty much tops out about water or 13 tons per dTon. But that is do to limitation of the equipment not the actual density of what is being moved. When they ship gold ingot its 3 or 4 pallets chained down in the middle of a much larger container... Figure 7.5 tonnes per dTon is you average maximum cargo mass...

I believe Timerover's numbers are correct, especially as he offers a wide range. I observe that modern shipping offers a "flat rack container" for unusually heavy loads such as heavy machinery and building supplies. The reference I have gives them a volume of a little over 30 cubic meters and a maximum load of close to 45 metric tons. More typical intermodal containers max out around about 30 metric tons for about 33 cubic meters. While most will ship substantially below that, and there are much larger containers of the same load for bulky but lighter items, a lot will depend on the specific cargo being transported, so a wide range is justified. A full load of taconite pellets is going to be quite a heavy cargo, and the classic rules would permit a ship to lift such a load.

 

[AnotherDilbert]

So a 200 Ton Free Trader might mass, empty, between 400 and 500 metric tons.

Both MT and TNE has the Free Trader at ~1100 tonnes unladen.

 

[atpollard]

For what little it might be worth, a fully loaded Saturn V, or the Apollo CSM or the Space Shuttle Orbiter all mass about 4 metric tonnes per displacement ton (14 cu.m.) ... which is the figure I use IMTU ... 200 dTon ship = 800 tonnes loaded.

 

[infojunky]

I observe that modern shipping offers a "flat rack container" for unusually heavy loads such as heavy machinery and building supplies.

Yes, yes they do, but neither they nor the arrangements to transport them are the standard.

More typical intermodal containers max out around about 30 metric tons for about 33 cubic meters.

20 foot containers tend to top out around 20 tonnes Tare weight. While a 40 foot container has a Tare of around 26 tonnes. If you ponder those numbers you will find you are up against the limits of handling equipment, not the mass you can stuff in it.

While most will ship substantially below that, and there are much larger containers of the same load for bulky but lighter items, a lot will depend on the specific cargo being transported, so a wide range is justified. A full load of taconite pellets is going to be quite a heavy cargo, and the classic rules would permit a ship to lift such a load.

So what are you arguing?

I am stating that most cargo holds are built to a specific set of characteristics, one of them being the maximum mass you can safely move in said cargo hold. Which I stipulate probably will be similar to current limits.

I didn't say you couldn't ship denser cargos, but they will either be shipped in specialized ships or use methods that would allow them to be shipped on a common carrier.

 

[aramis]

THe TEU is technically a dual standard - both mass and volume limits per TEU. 1 TEU High Cube is 8'8"x8'x20', for about 1386 2/3 cu ft but the walls count about 3" and the floor 6", for about 1128.125 cu foot internal ... ( 39.26 cu m, 31.9 cu m respectively, note switch to metric) and 24 tonnes total mass, of which, 21.6 tonnes is available for content,

The mass limit isn't exactly standardized, but the TEU limit is roughly observed by the manufacturers for a stack 8 high in hold; if you have cleats to take the mass off the lower, its possible to get taller stacks in. Most of the container builders I've looked at build them for 10-high, but list a rating for 8-high.


So, looking at the TEU as a 1 TEU 20' high cube, and a mass limit of 24 tons...
Specific Gravity of Cargo max is roughly 1. 2/3 kg/l, aka 1 2/3 tonnes per cubic meter, or 23 tonnes per Td...

About 2.3 times what FF&S says to limit it to if you don't want to refigure the drive performances.

 

[infojunky]

So, looking at the TEU as a 1 TEU 20' high cube, and a mass limit of 24 tons...
Specific Gravity of Cargo max is roughly 1. 2/3 kg/l, aka 1 2/3 tonnes per cubic meter, or 23 tonnes per Td...

Where are you getting Density numbers from?

But, I am talking about Allowable mass before possibility damage to the vehicles and vessels handling said containers...

In general 20 foot containers are limited to 20 tonnes of mass. And 40 foot containers are limited to 25 tonnes. Those are the road and port limits.

 

[aramis]

Where are you getting Density numbers from?

But, I am talking about Allowable mass before possibility damage to the vehicles and vessels handling said containers...

In general 20 foot containers are limited to 20 tonnes of mass. And 40 foot containers are limited to 25 tonnes. Those are the road and port limits.

I'm talking the max weight allowed by the TEU standard, and dividing that by the volume (external) of the container. I have, in the past, double checked those numbers from wikipedia against the actual standards referenced.

Road limits are often, but not always, lower

Note that they're seldom loaded that dense, but that gives you a peak routine cargo mass per unit volume as a fair high-estimate for loaded mass of cargo ships...

And there are substandards that are higher mass limits, with some regulations on where they can be stacked...