CT Only: Converting kg to Traveller tons

[snrdg082102]

Morning all,

I've dug up references in T4, Free Lance Traveller, and a couple of other sources that 1 Traveler ton or 13.4 or14 m^3 of liquid hydrogen is equal to 1,000 kilograms. In Book 2 turret missiles and sand canisters are 50 kilograms.

Would one missile or one canister be equal to 50 kilograms be equal to .05 tons or 0.675 m^3 or 0.7 m^3?

 

[whulorigan]

Morning all,

I've dug up references in T4, Free Lance Traveller, and a couple of other sources that 1 Traveler ton or 13.4 or14 m^3 of liquid hydrogen is equal to 1,000 kilograms. In Book 2 turret missiles and sand canisters are 50 kilograms.

Would one missile or one canister be equal to 50 kilograms be equal to .05 tons or 0.675 m^3 or 0.7 m^3?

Only if said missile or canister were made of L-Hyd. The relationship between displacement tons and mass-tons is dependent upon the density of the material in question. For L-Hyd explicitly, 1.0 dton = 14.0 m³ = 1.0 mt = 1000.0 kg.

For Water, 1000.0 kg = 1.0 mt = 1.0 m³ = 1/14 dton. (Meaning that liquid water is roughly 14.0 times as dense as L-Hyd, and therefore the same mass of water takes up 1/14 of the volume of L-Hyd).

 

[snrdg082102]

Morning whulorigan,

Thanks for the reply and the indication I was probably too vague in my question.

Only if said missile or canister were made of L-Hyd. The relationship between displacement tons and mass-tons is dependent upon the density of the material in question. For L-Hyd explicitly, 1.0 dton = 14.0 m³ = 1.0 mt = 1000.0 kg.

For Water, 1000.0 kg = 1.0 mt = 1.0 m³ = 1/14 dton. (Meaning that liquid water is roughly 14.0 times as dense as L-Hyd, and therefore the same mass of water takes up 1/14 of the volume of L-Hyd).

The power plant, maneuver drive, and jump drive are just as physical as missiles and sand canisters, yet these three items are expressed as taking up a certain amount of space in tons of liquid hydrogen.

I am trying to figure out how much space a 50 kg missile, 50 kg sand canister, and come to think of it a unpowered 10 kg grav belt needs relative to the units used for every other physical component used in Traveller's design and construction rules set.

 

[McPerth]

In MT there are such equivalences (well, IIRC not for the sandcasters ammo), as it discriminates among mass and volume.

The relation weight:volume in MT (in mton:kl, so multiply by 14 to have it in mt:dton) is:

JD: 2 mt/kl (so 28 mt/dton)
MD: depending on type. 2:1 for gravitic, just under 3:1 for thrusters.
PP: depending PP type and TL. For fusión PP, it foes from 1:1 at TL 16 to 4:1 at TL 9.

Missiles in MT (ammo, not launchers) need 0.1 kl in volume (so you could have 140/dton, and HE ones also weight 50 kg.


NOTE: I made the dton numbers using the 14 m³ per ton as is in CT, not the 13.5 in MT.

 

[rancke]

The power plant, maneuver drive, and jump drive are just as physical as missiles and sand canisters, yet these three items are expressed as taking up a certain amount of space in tons of liquid hydrogen.

'dT' is a unit of volume (as opposed to 'ton', which is a unit of weight), so it denotes volume. 'Kg' is a unit of weight, so it denotes weight.


Hans

 

[whulorigan]

Morning whulorigan,

Thanks for the reply and the indication I was probably too vague in my question.

The power plant, maneuver drive, and jump drive are just as physical as missiles and sand canisters, yet these three items are expressed as taking up a certain amount of space in tons of liquid hydrogen.

I am trying to figure out how much space a 50 kg missile, 50 kg sand canister, and come to think of it a unpowered 10 kg grav belt needs relative to the units used for every other physical component used in Traveller's design and construction rules set.

According to CT Special Supplement 3:Missiles (Revised), p.3:

Missile Parameters: Missiles can vary widely in their capabilities as well as in their physical descriptions. It is possible for missiles to be small enough to fit in the hand, or large enough to rival small craft. A standard has been established, however, which allows interchangeability of many different types of missiles and an ease of procurement as well. Standard missiles must be able to fit into a standardized shipping/launch container. The launch container is fitted directly to the launch rack and the missile is fired from it. The container contains integral test circuitry, provides protection from extremes of temperature and weather, and is isolated from the corrosive effects of atmosphere and moisture.

The standard container is a cylinder with interior dimensions of one meter long and 15 centimeters in diameter. Sealed for safety and security, the containers can be opened and the contents examined, removed or exchanged—an important feature when components are to be custom assembled for specific missile types.

Missile mass varies with the specific type of missile and is the sum of the masses of the missile’s components. For convenience, missile mass is used to determine space limitations on missiles. A standard container will hold any missile of 50 kilograms or less; missiles in excess of 50 kilograms are unable to fit in standard missile containers, and thus in standard missile launch racks.

Missile containers each mass 5 kilograms, and are disposed of when the missile is expended.

Missiles which exceed 50 kilograms must be handled in launch bays available under the High Guard construction system; they cannot be launched from ordinary turret missile launch racks.

Assuming the missile is cylindrical:

V_cyl = Π*r²*L
where r is the radius and L is the length.​

If:

r = 7.5cm = 0.075m
L = 1.0m,
​

then:

V_cyl = Π*(0.075)²*(1.0) = 0.018m³
​

Which means 56 missiles per m³ storage, or 777 missiles per dton_14.0m³ .

That seems like a lot. Did I make a calculation error somewhere?

 

[pendragonman]

Did you leave space for storage racks or are they just piled higglety piggelty on each other?

 

[whulorigan]

Did you leave space for storage racks or are they just piled higglety piggelty on each other?

No, I just calculated the straight volume of the missiles.

I agree storage racks would be necessary and take up volume, giving you fewer missiles per dton, but I don't believe there are dimensions given anywhere for the storage racks. I tried to stick specifically with the known numbers.

What do you think is a reasonable volume for the racks?

 

[McPerth]

No, I just calculated the straight volume of the missiles.

I agree storage racks would be necessary and take up volume, giving you fewer missiles per dton, but I don't believe there are dimensions given anywhere for the storage racks. I tried to stick specifically with the known numbers.

What do you think is a reasonable volume for the racks?

And this aside, the shape of missiles (mostly if they have fins for atmospheric use) is unlikely to match each other for full efficient use of volume.

I'd stick with the 0.1 Kl/missile shown in MT (that means 140/dton). According your numbers, that would mean about 18% of efficiency in volumen use, the rest being lost due to the racks, the missiles shape, storage, etc... I guess that's not far from real life storage, but I'm not an expert on that (to say the least).

 

[McPerth]

'dT' is a unit of volume (as opposed to 'ton', which is a unit of weight), so it denotes volume. 'Kg' is a unit of weight, so it denotes weight.


Hans

Well, from the puristical POV, kg are mass, not weight, but they are equivalent at 1G, and we, the Solomani, used to 1G gravity, use to confuse both terms.

Again from the puristical technical POV, the unit for weight, would be kp (of kilogram-force, equivalent to about 9.8 N).

In most efects, though, weight is irrelvenat for starships, mass being what means, and all of this don't deny your main point: dton is a volume unit.

 

[aramis]

Morning whulorigan,

Thanks for the reply and the indication I was probably too vague in my question.



The power plant, maneuver drive, and jump drive are just as physical as missiles and sand canisters, yet these three items are expressed as taking up a certain amount of space in tons of liquid hydrogen.

I am trying to figure out how much space a 50 kg missile, 50 kg sand canister, and come to think of it a unpowered 10 kg grav belt needs relative to the units used for every other physical component used in Traveller's design and construction rules set.

You can't get there from here.

There is a long standing disconnect between "Naval tonnage" and mass.

kg are purely mass

Not even getting into Traveller's space, a ton can be...
2000 pounds {weight} (short ton)
2240 pounds {weight} (long ton)
1000 kg {mass} aka tonne
2000 mass-pounds {mass} (short tons of mass)
2240 mass-pounds {mass} (long tons of mass)
100 cubic feet of cargo space {volume} (Registry ton)
35 cubic feet of water displacement {volume} (Displacement ton DT or dT)
40 cubic feet of cargo space or 1000kg {volume or mass} (Freight ton, FT)①
4.184 gigajoules {energy, specifically for large explosion events}
3.516853 kilowatts {refrigeration energy} - also noted as 12000 BTU/hour
£100 {UK currency} - slang term

The homonym Tun is a barrel... 252 U. S. gallons; this is equivalent to 33.6875 cubic feet or about 953.93 liters.

The Traveller Ton-Displacement is a unit of volume, not mass, and has ZERO convertability to/from mass tons as such. Depending upon edition, it's one of 14 cubic meters, 13.5 cubic meters, or 500 cubic feet.

The Traveller Cargo Ton, in CT is implied to be a combined mass & volume unit of 14 cubic meters or 1000kg ①
In TNE, it's implied to be 14 cubic meters or 10000kg(=10 tonnes)①

-=-=-=-=-
①Whichever measure produces the least available cargo space for the hold, or most tonnage taken for the cargo.

 

[Timerover51]

That seems like a lot. Did I make a calculation error somewhere?

First, your missile is way too dense. You are using a stretched 75mm round, not something resembling a missile, which is not mainly dense metal.

Second, you used Traveller without any input from the Real World.

The Real World. The 155mm Cannon-launched Guided Projectile, commonly referred to at the "Copperhead", has the following dimensions and weight, to include packaging. That is the closest I could find readily on my computer to a 50 kilogram Traveller missile.

Weight is 138 pounds, or 62.6 kilograms. (I know that is 12.6 kilograms heavier than the maximum allowed 50 kilogram launcher-fired missile in Traveller, and it does not even have a propulsion system.)

Dimensions of round: 54 inches/1.371 meters by 155mm.
Packaged: 61 X 11.375 X 11 inches, weight 205.5 pounds, cube 4.4 cu. ft.
Packaged for shipping and storage: 6 projectiles per pallet, 1358 pounds
61 X 27.5 X 33 inches, cube 32 cu. ft.

With a cube of 32 cu. ft. for the pallet, you can get approximately 15 pallets per Traveller dTon. So, 90 missiles per dTon.

Now, the Copperhead is intended for firing in an atmosphere. Traveller missiles I assume are being fired in a vacuum, so no need for streamlining or ballistic shaping. The most likely shape will be something approximating a scaled-down Apollo capsule with service module or a Lunar Lander. Why those? Because you need steering jets to alter your powered trajectory, so missiles are probably going to be short and wide, and take up lots of space in packaging. I still have not figured out how you get a really long-endurance propulsion system into a missile of 50 kilograms, which is about the same as the current Sidewinder round. Burn time there is about 2 to 3 seconds. There must be some incredibly energetic propellants available.

The old Sparrow III, weighed about 500 pounds, 227 kilograms, was intended for atmosphere firing so had fins, not steering jets, and a burn time depending on the model of up to 10 seconds or so. Including firing speed, it peaked out at maybe Mach 3.5. So much for real-world physics.

As for the sand caster, that would depend on what actually is meant by "sand". Does this mean actual sand, precisely formed glass crystal to break up laser beams, and incidentally play havoc with any missile that runs into the sand cloud, a blend of minute, highly reflective aluminum shapes mixed with glass prisms, or what? Sand and gravel are listed in my Transportation Reference Manual at 90-105 pounds per cubic foot, dry and packed. That would mean a 50 kilogram container of sand would be about 1 cubic foot, so depending on the container shape, you could, in theory, stow between 476 to 494 containers of sand per Traveller dTon. At 476 containers per dTon, that would weight 23, 600 kilograms, or 23.6 metric tons per dTon. I suspect that actual stowage would be a lot less.

Also, remember that when you use sand, it will have about the same velocity and course vector as the ship when dispensed, and keep that velocity and course vector regardless of ship maneuvering, basically until either the gravitational force of a nearby planet, the solar gravitational pull, or some other gravitational force acts to change its direction. In theory, if the ship that dispenses it is going fast enough and outbound from the local sun, it could travel into interstellar space, still chugging along, but gradually dispersing into a larger and larger cloud of material. Note, this would not be good to encounter while traveling in the opposite direction.

 

[aramis]

The standard traveller missile of CT is defined in Special Supplement 3...
it's a 15cm diameter, 1m long missile in a standardized packaging (which isn't listed) if we assume a 20x20x105cm box for the package, that gives a reasonable allowance.

That puts it at 0.042 cubic meters, or just shy of 24 per cubic meter. (23.81 is pretty close.) (It also puts the assmebled SG at 1.19.)
A cargo ton being either 10,000kg or 14kl... limits us to 200 per cargo ton (due to the 10k kg limit), probably less, due to the container probably massing 2kg+... a 2kg container mass would make it 192 per cargo ton. If we go with the implied-by-examples cargo ton of 1000kg, its 19 per cargo ton, sitting in 789 l of the 14000 l

 

[Timerover51]

Where does the 10,000 kilogram per Traveller dTon appear in Classic Traveller?

 

[McPerth]

For what's worth:

In MgT (whose CB ship design is quite compatible with CT:LBB2), you can have in storage 12 missiles or 20 sandcaster barrels per dton dedicated to magazine.

 

[mike wightman]

In CT 77 trade rules 1 ton is 1000kg when considering cargo.

 

[snrdg082102]

Afternoon all,

That you all for the replies to my question, unfortunately I am now even more confused. In fact some of the material presented is what I found and prompted my question.

These are the three items in CT LBB editions that are rated as taking up a any part of 13.5 m^3 or by rounding 14 m^3 space used by the bridge, staterooms, computers, fire control, vehicles, or small craft.

1. The turret missile per CT Book 2 1977, 1981 Second edition 6th printing p. 17: The typical missile is a homing type which constantly seeks the target ship, ultimately being destroyed by the target's defenses or exploding and doing damage and weighs about 50 kg at a cost of MCr0.005.

I do not have a copy of Special Supplement 3 Revised, which leaves me looking at the original in JTAS and the Consolidated CT Errata.

In the original SS3 has the standard turret missile price as either Cr15,960 at TL9, 16,200 at TL?, or 31,100 at TL7.

Consolidated CT Errata version 0.8 has missile as a continuous burn type which cannot alter course. The cost and mass of are close enough to the CT Book 2 details.

2. The sand canister per CT Book 2 Second edition 1977, 1981 6th printing p. 17 weighs about 50 kg at a cost of MCr0.0004.

3. The grav belt per CT Book 3 1981 Second edition 1977, 1981 3rd printing weighs 10 kg when turned off at a cost of MCr1.

What is the simplest way to figure out how much space objects that weigh f 50 kg or 10 kg take up in cubic meters based on the 1.5 meter squares used in Snapshot and Azhanti High Lightning which is a grid of 1.5 m x 3 m x 3 m = 13.5 m^3 or through rounding add .5 m^3 to make a nice even 14 m^3 equaling one ton of space?

For that matter what is the weight in kilograms of the ATV that takes up 10 tons of volume within the hull?

I appreciate the MgT tidbit and I'll check out GURPS Traveller and Traveller 20.

Unfortunately, CT LBB1 through 3 1977 have been replaced by the CT LBB1 through 3 second editions in 1981, otherwise I would being using that little tidbit and thank you for finding it.

 

[aramis]

Where does the 10,000 kilogram per Traveller dTon appear in Classic Traveller?

It doesn't; it's a TNE definition that's backported, because it fits with the Striker densities. It's about what a G-Carrier masses per ton, too.

Generally, the vehicles, when done with Striker (or MT), mass 5-10 tonnes per Td. Since their cargo Td is specified already, that forces a conversion other than the exemplar 1000kg per Td.

For comparison, the displacements and masses per MT for the standard vehicles (range is unloaded-loaded; * indicates not in CT):
Ground Car 2Td 3-5 tonnes
Wheeled ATV 10Td 28-55 Tonnes
Tracked ATV 10Td 47-74 Tonnes
Air/Raft 2Td* 1.6-7.2 Tonnes
Enclosed Air/Raft 4Td 4.6-18.7 Tonnes
G-Carrier 8Td 20-48.1 Tonnes
Speeder 6Td 19.2-25.4 Tonnes
The striker stats are going to be VERY close, with slightly different cargo allotments (as Striker has armor take volume, but uses the CT 14kl Td, and MT has armor not take volume, but uses a 13.5kL Td).

 

[Timerover51]

Looking at the US Army TM9-2800, Standard Military Vehicles, for 1943 and 1953, the specifications for Ground Car come nowhere near what you are generating through Striker. Again, I am looking at Real World Data.

For the 5-passenger, 4-Door Sedans of the period, the weights come out at somewhere between 3,200 and 4,000 pounds, except for Cadillacs, which run about 4,500 pounds. So, even with those heavy vehicles, you are looking at less than 2 metric tons, with the top at about 2 metric tons. However, for cube volume, that comes in at about 4 Traveller dTons, as the widths are greater than 1.5 meters, and the lengths are greater than 4.5 meters. The Jeep comes closest to your 2 dTon, but weights in LOADED at 3,200 pounds, with an empty weight of about 2,400 pounds.

The weights for the Wheeled and Tracked ATV look quite heavy, compared to the Real World, and are more what you would expect for an Armored Vehicle, and even then, still heavy. Remember, an ATV is supposed to float. My favorite vehicle, the DUKW, has dimensions of 372 X 106 X 98.875 inches and had a net weight of a bit under 15,000 pounds with a loaded weight of just under 21,000 pounds, so less than 10 metric tons loaded, and would fit in 7 dTons of space. Again, that is Real World, but I do much prefer to use Real World equipment if at all possible.

 

[aramis]

Looking at the US Army TM9-2800, Standard Military Vehicles, for 1943 and 1953, the specifications for Ground Car come nowhere near what you are generating through Striker. Again, I am looking at Real World Data.

For the 5-passenger, 4-Door Sedans of the period, the weights come out at somewhere between 3,200 and 4,000 pounds, except for Cadillacs, which run about 4,500 pounds. So, even with those heavy vehicles, you are looking at less than 2 metric tons, with the top at about 2 metric tons. However, for cube volume, that comes in at about 4 Traveller dTons, as the widths are greater than 1.5 meters, and the lengths are greater than 4.5 meters. The Jeep comes closest to your 2 dTon, but weights in LOADED at 3,200 pounds, with an empty weight of about 2,400 pounds.

The weights for the Wheeled and Tracked ATV look quite heavy, compared to the Real World, and are more what you would expect for an Armored Vehicle, and even then, still heavy. Remember, an ATV is supposed to float. My favorite vehicle, the DUKW, has dimensions of 372 X 106 X 98.875 inches and had a net weight of a bit under 15,000 pounds with a loaded weight of just under 21,000 pounds, so less than 10 metric tons loaded, and would fit in 7 dTons of space. Again, that is Real World, but I do much prefer to use Real World equipment if at all possible.

The armor thickness is that of a real world WWII APC on those ATVs. The G-Carrier has better than that...

I agree, Striker isn't a good model, but it's the best model most of us had at the time. And, for games of the era, it was pretty darned good. It's also the baseline for MT, and MT the baseline for FF&S... which covers most of the first 20 years of the game line.

Almost all Striker masses are over by about 1.5x to 2x... almost as if they used pounds as kilos...