Cargo space and tonnage needed

[Rooster Cogburn]

If I wanted to create a landing craft that could haul 4 ATAVs (Mongoose Supplement 6 p 28) with M^3 = 8 and weighing 2,331kg, would all I need is 10t of free cargo space (10t * 1,000kg/ton = 10,000kg / 2,331kg/per ATAV = 4.29)?

Or do I need to take the ATAV's M^3 into account as well?

Thanks.

 

[steventirey1985]

If I wanted to create a landing craft that could haul 4 ATAVs (Mongoose Supplement 6 p 28) with M^3 = 8 and weighing 2,331kg, would all I need is 10t of free cargo space (10t * 1,000kg/ton = 10,000kg / 2,331kg/per ATAV = 4.29)?

Or do I need to take the ATAV's M^3 into account as well?

Thanks.

You need to use their volume. A starship is not measured in tons (weight). It is measured in displacement tons. 1 displacement ton is 13.5 (0r 14) cubic meters. Actual weight usually doesn't matter at all. 4 8 cubic meter ATAVs could fit in 3 tons.

A 10 ton fighter is not 10 tons of wight, but 10 displacement tons of volume - 135 or 140 cubic meters of stuff.

 

[Rooster Cogburn]

So to just make sure I understand, if my Free Trader Type A lists a cargo capacity of 88 tons, that is for displacement purposes not weight. Is that correct?

 

[McPerth]

Yes, that's why they are usually said as dtons (displacement tons). Each one means 14 cubic meters (13.5 in MT), regardless of its true weight.

In some rules sets (e.g. MT), the ships are rated by its dtons (volume), but also are computed by their weigth (in metric tons, each one 1000 kg).

 

[Rooster Cogburn]

Yes, that's why they are usually said as dtons (displacement tons). Each one means 14 cubic meters (13.5 in MT), regardless of its true weight.

In some rules sets (e.g. MT), the ships are rated by its dtons (volume), but also are computed by their weigth (in metric tons, each one 1000 kg).

I've seen dtons and did understand that for meaning displacement tons but thought that only applied to the actual ship and not the cargo bay. Thanks for clarifying.

 

[aramis]

I've seen dtons and did understand that for meaning displacement tons but thought that only applied to the actual ship and not the cargo bay. Thanks for clarifying.

Note that, in TNE, (actually in the Brilliant Lances Tech Book, IIRC) there is a limit of 10 tons metric per cargo Ton-Displacement.

Also, if you see Td, that's Tons-Displacement.

 

[jshiggin]

So to just make sure I understand, if my Free Trader Type A lists a cargo capacity of 88 tons, that is for displacement purposes not weight. Is that correct?

Yes. Remember the cargo hold is just a big box with a door. If it fits, it ships.

If it doesn't, and you try to ship it anyway, all the air will leak out the open door.

Note that even in MT, where you calculate the mass of your ship (in addition to the volume), the mass of the cargo only matters if you're trying to decide whether the starship will sink if you land it in the ocean (usually, no, unless you're carrying a particularly dense cargo, or have an armoured hull).

 

[rancke]

Note that even in MT, where you calculate the mass of your ship (in addition to the volume), the mass of the cargo only matters if you're trying to decide whether the starship will sink if you land it in the ocean (usually, no, unless you're carrying a particularly dense cargo, or have an armoured hull).

In GT (and unless explicitly[*] ignored for game purposes in any remotely realistic setting) it affects maneuver drive performance.

[*] That is, the rules acknowledge that they're doing it wrong but it's easier that way and don't make enough difference to matter.​

Hans

 

[McPerth]

Note that even in MT, where you calculate the mass of your ship (in addition to the volume), the mass of the cargo only matters if you're trying to decide whether the starship will sink if you land it in the ocean (usually, no, unless you're carrying a particularly dense cargo, or have an armoured hull).

That's only if you use gravitic or thrusters maneuver drives (as most ships do). If you use low tech drivs (as seen in One Small Steep, in HT), from solid fuel rockets to fusion rockets, it's you loaded mass what gives your acceleration.

And also loaded weight is used in MT to calculate Agility (there's not much of in in MT).

For all those calculations, the cargo weight is set at a flat 1 kl= 1 Metric ton (as if loaded with water).

 

[BytePro]

...
If it doesn't, and you try to ship it anyway, all the air will leak out the open door.

Though never forget to tie on the radar reflective neon yellow ribbon at the trailing end of yer load... or the authorities might pinch you for an intrasystem safety violation infraction.

Also - for maker-sakes - always tie down your load, no matter how many AUs you plan on going...

 

[drkem99]

One of the best discussions of displacement tons vs. actual mass and comparing starships to surface warship and freighter tonnage measurements is by Ken Pick and is at: http://www.freelancetraveller.com/features/shipyard/tonnage.html

Your ATAV's weigh just about 300 kg per cubic meter which agrees nicely with his article (surface warships massing between 0.35 and 0.5 metric tons per cubic meter depending on armor.) Armored vehicles are heavier; the M1 Abrams, for example, approaches 1 metric ton per cubic meter (as do our current submarines and presumably, system defense boats.) I would have to say that 1 metric ton per cubic meter (14 metric tons per dT) as an estimate for cargo will tend to be high except for very specialized cargoes (refined metal ores, heavy machinery, etc.)

If you plan to ship your ATAV's boxed up as cargo, I agree they could be shipped in 3 dT or a little less. If you plan to be able to walk around the vehicles and load them, repair them, and so on, I would treat them as double their volume (since most vehicles tend to be low and wide sitting on the deck and do not use the full 3 meters of height per dT in the standard cargo bay.) I would also add about 30% volume around them (similar to hangar space requirements) for access.

As a GM, I would make my players allocate a full 8 dT of cargo space to have them stored in walk-up-to-and-get-in-comfortably-and-drive-off condition.

 

[BytePro]

Its really, really simple - just like parking a vehicle in a garage in the RW... if the deck is high enough, the volume required is going to be largely based on the length and width required (including any desired clearance).

Ex:
M1 tank, overall ~ 10 m long by 3.7 m wide by 5.3 m tall.
=> For 1.5 m squares, would squeeze in to 7 long by 3 wide deck squares. Since it would require a double height deck, that works out to 21 dTons for a fairly tight park, but with access to the turret crew hatch...

A CT type ATV (10 mass tons vs Abram's 60+) that supports 8 people for a duration, could easily share such overall dimensions. If the doors/airlocks use internal (iris, sliding types, etc) opening then the deck plans don't need clearance except for maintenance and exterior stowage...

If you don't want a double deck height, then make your ATV shorter (and maybe with lifters), etc. Maybe it fits in 12 dTons, or 8 - whatever.

CT didn't define dTons for vehicles because it is something that should be treated on a case by case basis. Any general 'rule' is going to fail when applied to given ships - as volume does not account for shape.