tons

[mike wightman]

A 100t cargo hold can only carry 100 metric tons by mass or it breaks the whole ship paradigm - as my example above shows.

When determining the contents of a cargo, the players and referee must be certain to correlate the established price of goods with the cost per ton. For example, the base price of a shotgun is Cr150, while a ton of firearms as trade goods has a base price of Cr30,OOO. A strict weight extension of the shotgun (3.75 kg per shotgun) would indicate 266 shotguns. Extension should be instead based on price, with weight as a limiting factor. Thus one ton of shotguns would contain 200 guns, at Cr150 each. The extra weight can be considered packing and crates. Similar calculations should be made to keep prices in line on other trade goods. Some goods (those results 51 - 56, and 66 on the table) are sold individually instead of by the ton. Quantity is expressed in single units; tonnage and base prices must be determined by the players or referee in accordance with established prices and equipment.

The example clearly shows the cargo ton is 1000kg.

Note that if a cargo ton is 14 cubic metres you can cram a lot more than 266 shotguns into that volume.

 

[kilemall]

A 100dt cargo hold filled with 1400 metric tons of water (the volume capacity of the hold) will allow you to make 155 metric tons of hydrogen, which means you are better off carrying water than additional fuel tankage

Very true if you are using magic M-drives where mass isn't an issue, which may be the case if you put your gravitics on overdrive.


I think it's more fun to take on wiseguys that pull that sort of advantage play and figure in physics penalties- those who live by science die by it.


For instance, maybe you were floating on the water surface fine- until you took in that last 10 dtons/140 metric tons......

 

[kilemall]

A 100t cargo hold can only carry 100 metric tons by mass or it breaks the whole ship paradigm - as my example above shows.

The example clearly shows the cargo ton is 1000kg.

Note that if a cargo ton is 14 cubic metres you can cram a lot more than 266 shotguns into that volume.

One point to keep in mind- RL containers often ship with empty space along with the cargo, if the cargo is too heavy/dense to pack into the load bearing capacity of the container.


The question is, is the load bearing 1 metric ton per cubic meter as per water, or 1 metric ton per 1 Traveller dton?


One gets you empty space just for items that are denser then water, the other gets you a lot of empty space even for light cargoes.

 

[AnotherDilbert]

By MT & TNE that discussed this in detail merchant ship's generally float, e.g. Free Trader:

Volume 2700 m³, Mass (loaded) 2280 tonnes.

Armoured ships generally don't float.

 

[BwapTED]

By MT & TNE that discussed this in detail merchant ship's generally float, e.g. Free Trader:

Volume 2700 m³, Mass (loaded) 2280 tonnes.

Armoured ships generally don't float.

Thanks for this info.

 

[BwapTED]

That just means you aren't understanding the units involved. This may be a side effect of referring only to CT77, a rule set written during the dawn of RPGs by a group of people that did not include an engineer or physical scientist.

True, it is made all much clearer in later materials (1979/80).

I understand the real world principles and measurements. I am sure you do, too.

The obvious fix is to call the volumic Traveller ton a v-ton or an f-ton and dispense with the confusing reference to ''mass displacement'', if no fluid mass is being displaced by the vessel.


EDIT

It occurs to me that some of this comes down to the Space is an Ocean trope.

Traveller is meant to evoke an Age of Sail feel, right?
So maybe 'mass displacement' does fit star-ship design,even if they aren't actually floating in a fluid medium.

Marines with cutlasses.

Navy as the 'space force.'

Hmm...

https://tvtropes.org/pmwiki/pmwiki.php/Main/SpaceIsAnOcean

Game books aren't just technical manuals. (Most games, anyway. )

If I look at this from the style end of things, it makes a lot more sense.

 

[GypsyComet]

A 100t cargo hold can only carry 100 metric tons by mass or it breaks the whole ship paradigm - as my example above shows.

The example clearly shows the cargo ton is 1000kg.

Note that if a cargo ton is 14 cubic metres you can cram a lot more than 266 shotguns into that volume.

That's a real world piece of knowledge being dragged into a game mechanic, and is the source of your problem. The game makes no statement regarding the density of a given cargo item as shipped. That is entirely your assumption based on what you know about shotguns and what form their shipping containers would take.
Uranium has already been brought up, for example. Refined uranium is very dense, and 1000kg would occupy about one 55-gallon drum. Of course, that's not a shipping container; that's an active radiation hazard. Safe transport of a ton of uranium is probably going to fill the displacement ton on a ship.

As far as the ship is concerned, a cargo ton is only volume. What you put into that space, whether it is the whole chickens or just their feathers, is irrelevant to the design of the ship at the Book 2 level. Your example only shows that the designers assumed that the conversion from mass ton to volume ton was 1-to-1 in the one place where data entering the equation was in kilograms. Why? Because no other mechanism is offered. Occam's Razor applies.

 

[BwapTED]

Shotgun shipping container=crates.

Enough packing peanuts to fill the 14 cubic meters seems excessive and silly, neh?

But I agree about uranium.

The rules on page 43 actually note container weight as a limiting factor, and rounding off amounts of cargo items by price and quantity.

This looks like a referee call, use common sense.

That 14 cubic meters bit isn't anywhere in the 1977 rules. If we are using it (and I'm not saying one should not)then perhaps the best way to read the rules is that the cargo (including containers) must not exceed the metric tonnage allotted and must also fit in the volume allotted.

Overload volume= cargo must be strapped outside ship or towed or stuffed in a spare stateroom.

Overload mass= takes more energy to push ship about space, fuel use increase, downgrade performance...

This approach may be too finicky for some refs and players.


The referee has to make some calls or refer to later materials.

 

[kilemall]

[FONT=arial,helvetica]

[/FONT] By MT & TNE that discussed this in detail merchant ship's generally float, e.g. Free Trader:

Volume 2700 m³, Mass (loaded) 2280 tonnes.

Armoured ships generally don't float.

So my rough estimate of density of 10 metric tons per dton works out (well, more like like 11.4).


That example says the ship itself is 5.65 metric tons per dton. A fair amount of light equipment and/or space. It might be instructive to compare these to say fighter planes vs. airliners.


Assuming a classic 82 tons or so of cargo space, that leaves us with a density of 14.02 something. Virtually the exact definition of a metric ton- IMO not a coincidence.


Well, no 200+ shotguns I know would fit into a cubic meter. So we are left with a load bearing of 1000kg plus packaging and volume of 14 cubic meters as at least a shipping standard for parsec transport.


Still would like to know what we get if that is exceeded- greater payout for greater tonnage? Lift problems? Load bearing problems risking the ship itself?



Yes armor should make for a sinking ship. You could of course go for a High Guard equivalent of the American scheme to armor, effectively have different rates of armor coverage for different components. Floating on water might not be high enough value to skimp on coverage for most space navies but high hydrography planets may not have a choice.


https://en.wikipedia.org/wiki/All_or_nothing_(armor)



[FONT=arial,helvetica][/FONT]

 

[mike wightman]

That's a real world piece of knowledge being dragged into a game mechanic, and is the source of your problem.

It's not my problem
Are you seriously suggesting that we should leave real world knowledge at the front door when discussing Traveller?

The game makes no statement regarding the density of a given cargo item as shipped. That is entirely your assumption based on what you know about shotguns and what form their shipping containers would take.

But it does make a statement with regards to the mass of a shotgun being so many kg and 266 of them therefore fitting in one ton of cargo (reduced to only 200 to match the cost} - therefore one cargo ton is 1000kg. It really can not work any other way.

Uranium has already been brought up, for example. Refined uranium is very dense, and 1000kg would occupy about one 55-gallon drum. Of course, that's not a shipping container; that's an active radiation hazard. Safe transport of a ton of uranium is probably going to fill the displacement ton on a ship.

Now you are brining real world knowledge into this... I'm not allowed to but you are?
Anyway that is precisely my point. IMTU they would transport 1000kg or uranium in one cargo hold displacement ton, not 14 cubic metres of the stuff, which masses 266 tons.

As far as the ship is concerned, a cargo ton is only volume. What you put into that space, whether it is the whole chickens or just their feathers, is irrelevant to the design of the ship at the Book 2 level.

Which is heavier a ton of feathers or a ton of lead? The example clearly states that one ton of cargo is 1000kg.

Your example only shows that the designers assumed that the conversion from mass ton to volume ton was 1-to-1 in the one place where data entering the equation was in kilograms. Why? Because no other mechanism is offered. Occam's Razor applies.

Exactly - Occam's razor, one cargo hold ton is 1000kg.

Or better yet use FF&S to design ships so you can track mass and volume.

The disconnect in all of this is that the shipboard displacement ton as it was later defined is a unit of volume, the cargo ton is a metric ton, and ship mass has nothing to do with drive performance, it is all about volume.

The sensible solution has now been suggested by about three different people - one cargo (displacement)ton container can not exceed one metric ton by mass or fourteen cubic metres by volume.

 

[Brandon C]

This argument reminds me of why GT has my favorite Traveller ship design rules: volume and mass are tracked separately and both influence design and performance.

 

[mike wightman]

I don't like their power slice abstraction

I much prefer the GT:ISW design system.

Best of the lot remains FF&S

 

[aramis]

No, sorry, it is not a mass unit. Top of Page 10 has the definition. Hulls are repeatedly referred to as having a "size", not a mass. The drive tables use "Mass" as an abbreviation for Mass Displacement, which is explained just below the table. For that usage to change mid-process would make no sense whatsoever.

While fuel is not explicitly defined in Book 2-77, it IS stated that unrefined fuel is skimmed from gas giants (page 9), which narrows the range of candidates considerably. The Technology table in Book 3 (Page 11) defined TL8 and above as using Fusion. At the time of writing, that really only meant hydrogen.

The argument that nautical displacement tons and Traveller 77's "mass displacement" are the same is missing the conversion factor inherent to the nautical unit: Boats gotta float. A nautical vessel that displaces X tons of water has an actual mass that is very close to that because the need to float converts the unit back to mass. Traveller's displacement ton is not the same thing. There is no flotation conversion to take "mass displacement" back to "mass".

*Traveller "mass displacement" is in fact a volume, and a volume only.
*The entire ship construction and economic system uses mass displacement, even when it says only "mass".
*Any other conclusion assumes a conversion that is never stated, clarified, or even hinted at.

There's the issue of known quantities:
Remember: LHyd expands with increasing temperature - from a high of 0.0799 ( at 20° K) to a low of about 0.0708 (at about 33° K), for 12.52 to 14.12 cubic meters per tonne (metric). We'll use a nominal 14.

• at naval full-submergence displacement (ie: 1 cubic meter or 35 cf per Td),
  • a stateroom is only 4 cubic meters - barely enough for a bunk and access to the bunk. Comparable to the two-petty-officer "Cabins" on subs
  • The standard seat on small craft becomes 0.5 cubic meter - a coffin-sized space.
  • A tonne of fuel takes 14 dtons storage
• At standard ratio of enclosed to displaced naval dTons (ranging from 3:1 to 5:1, nominally about 4:1)
  • A stateroom is 16 cubic meters - livable, but cramped. Actually, assuming half-in-room/half-in-corridors, 2x2x2 meter living space, and 4x2x1 ≅ 4m of narrow gangway.
  • The seat becomes 2 cubic meters - about proportional to first class on modern jets.†
  • LHyd Fuel becomes 3.5 dTons per tonne mass
• Using later explicit 14 cubic meter displacement tons...
  • Staterooms are 56 cubic meters, and 28 in room. that's a nice 3.5 × 4 × 2 room, comparable to a modern cruise ship cabin.
  • The small craft seat becomes 7 cubic meters - comparable to the volume is a large pickup-bed-carried camper's space for 2 persons.
  • Fuel mass is close to the dTon. ±10%.

Now, the actual mass of an acceleration couch is nowhere near 500 kg. They're more like 100 kg, and even the more corpulent passengers top out about 250 kg (above that, and they can't wedge themselves through the doors, nor into a seat).

There's a dichotomy here - the stateroom sizes for passengers are a best fit at 14, while seat sizes are best at 4, as are crew cabins.


† Using the 717-200 Treating the cabin space as a 3 × 1.1 rectangle, and a 3 to 1 × 1 mirrored trapezoid, at 0.8 seat pitch for coach... so (3.3 + 2) × 0.8 = 5.5 × 0.8 = 4.4 cu m; that's 5 seats, so 0.88 cubic meters each, including only seat, seat-side aisle, and overhead bins. First class is 4 seats and 0.9 to 1 m pitch, so 4.95 cu m, or 1.23 to 1.35 cu meters per each.
Adding freshers, access to the aisle, kitchen, and 0.2 cu meters of cargo space for checked baggage...

Some references for the above:
https://www.researchgate.net/figure...in-with-the-main-dimensions-20_fig2_309327917
http://www.aeronewstv.com/en/lifest...he-weight-of-a-fighter-jet-ejection-seat.html
https://www.flyradius.com/boeing-717/200-interior-cabin

 

[BwapTED]

How much space of the total volume for The State Room is taken up by life support? I'll go downstairs and grab High guard and see what the 1979 answer is, if there is one. But for design purposes it seems to me that staterooms including life support might stay around the same volume but the livable area gets bigger at higher Tech levels as life support can be miniaturized slash packed into the walls/bulkheads.

 

[BwapTED]

Now about crew chairs, perhaps they are very large if one assumes no or strictly Limited gravitic and inertial compensation / manipulation. Then it would be more like flying inside some kind life support tank. You don't just sit down in the heavily cushioned chair and strap yourself in for the ride. No, you crawl inside the clamshell and auto-injectors push into your body ready to dispense drugs that help you fight the effects of extreme acceleration. Machines inside this tank help you to breathe help your heart to pump blood etc etc. Of course if this is the case then I would think that staterooms would probably be fitted with these as well. And that's going to take up more space in those rather large staterooms, so if you do want to retain a somewhat cramped feel it can still be done at 14 cubic meters per ton.

 

[Timerover51]

Commercial nautical shipping does not worry about ship displacement except for making sure that the ship's draft does not exceed the depth of any port that is to be entered. Commercial shipping uses the gross register ton of 100 cubic feet, the measurement ton of 40 cubic feet, and the number of 20-foot container equivalents that the ship can carry. All are used as an indication of the revenue generating ability of the ship. A cruise ship is evaluated on the basis of what is the total number of passenger berths on the ship. The other major factor in commercial ship construction is the size of any locks or canals that the ship may be using. The Panama Canal still is a factor in how large any cargo ship is going to be, with the new larger locks allowing for larger ships. A ship listed as "Panamax" means that it is the largest hull that can safely pass through the Panama Canal locks. The locks on the St. Lawrence Seaway set the limit on ship size on the Great Lakes in terms of length, beam, and draft. Displacement in terms of water displacement is not a factor at all. It either fits or is does not.

The gross register ton is most applicable to the old cargo liners which might carry 400 to 500 passengers and 10,000 tons of cargo between Plymouth, United Kingdom and Beunos Aires, Argentina on a regular commercial run.

The measurement ton is more accurate at assessing the break-bulk cargo carrying of non-container ships, giving an idea as to the maximum deadweight tonnage of cargo that could be carried. The Liberty Ship, with a measurement tonnage of 11,886, could carry 10,800 deadweight tons of cargo, assuming that much cargo could fit within the internal volume of the cargo holds and deep tanks.

With respect to life support, I figure that it would be at the rate of one cubic meter per stateroom. The basic requirements are ensuring adequate oxygen supply, scrubbing carbon dioxide out of the ship's air supply, food, water, and waste processing. A cubic meter of water is equal to 264 gallons, so figure a cubic meter of water per 10 persons on board would be more than adequate with high-efficiency recycling, while one cubic meter of dry storage can hold sufficient preserved food for 5 men for 30 days (based on FM 101-10, Staff Officers' Field Manual-Organization, Technical, and Logistical Data, page 222, using the 5 person Small Detachment ration). A lot of how much room to allow would be based on how much water are you planning to carry per stateroom, and how much food. Army rations are based on 3600 to 4000 calories per day, which is a lot for sedentary personnel. The Army allows for 15 gallons per person per day for all uses including bathing, and that assumes no recycling. Twenty-six gallons per person per day with recycling should be more than adequate, but an additional cubic meter of water per 10 persons would not be that hard to supply. Extra oxygen could be carried in the form of water, to be generated as needed.

We already know how to do life support for space ships with the Shuttle and the International Space Station. Then there are the Fleet Ballistic Missile Submarines that operate underwater for 60 days at a time with a crew of over 100.

One of these days I need to formally put up how I supply the crew on one of my ships. I just need to put it all together.

 

[Timerover51]

Now about crew chairs, perhaps they are very large if one assumes no or strictly Limited gravitic and inertial compensation / manipulation. Then it would be more like flying inside some kind life support tank. You don't just sit down in the heavily cushioned chair and strap yourself in for the ride. No, you crawl inside the clamshell and auto-injectors push into your body ready to dispense drugs that help you fight the effects of extreme acceleration. Machines inside this tank help you to breathe help your heart to pump blood etc etc. Of course if this is the case then I would think that staterooms would probably be fitted with these as well. And that's going to take up more space in those rather large staterooms, so if you do want to retain a somewhat cramped feel it can still be done at 14 cubic meters per ton.

You do understand that 14 cubic meters is almost 500 cubic feet, 494.40533 to be more exact. That would be about an 8 foot by 8 foot by 7 foot 8 inch room.

As for your life support tank, that sounds a lot like a low berth to me. Once it, you stay there for the trip.

 

[Brandon C]

I don't like their power slice abstraction

I find it convenient.

I much prefer the GT:ISW design system.

I'm not sure if I've ever even seen that book. Since it was 4e, wasn't on my radar anyway.

Best of the lot remains FF&S

IIRC, in FF&S, the mass of a ship has no bearing on acceleration. Only volume matters. I have an issue with this

 

[Brandon C]

Then there is no mention of artificial gravity or inertial compensation...

Things would have been more interesting if they had never been mentioned

 

[Timerover51]

Yeah, I understand the math. :rofl:

What's your point?

You don't think a room that size containing a large life support apparatus could feel cramped?

That would feel cramped to you even if empty?

RE the life support tank-- you would not need to be in it when the star-ship was under 1 g constant acceleration. That would provide artificial gravity (the real kind). Yes, I am assuming a vertical/tail-sitter arrangement of decks.

The tank is for high accelerations and maneuvers. If the alarm goes off, climb in.

It probably is related to the low berth. Good call.

Just to be clear, because I was a bit slippy about calling Aramis' small craft seats ''crew chairs';:




He figures a stateroom at 56 cubic meters.

He has the small craft seat at 7 cubic meters.

I'm saying that you can justify at quite bulky small craft seat by saying it's more than just an acceleration couch.

I then went on to suggest that similar machinery could form part of the life support in the stateroom, if one wanted cramped staterooms at 14 cubic meter per d ton scale.
Some guys think that scale makes the staterooms too big.


I hope all that is clear.

Not really, but it is your Universe, not mine. I will drop out of the discussion.