Size and Weight of Ships

[Carlobrand]

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

If the question here is the possible mass of cargo - in a Traveller universe with cargo ships traveling between stars to planets of varying tech levels, gravity levels, cultures, industrial bases, and sometimes species - then arguing for a standard does not give us an answer; it gives us a median.

I would argue that spacefaring ships that haul cargo under a wide variety of circumstances would be prepared to meet a wide variety of circumstances, or they would miss out on potential profits. The median is all well and good, and ships built to serve standard routes will likely be build to the median - or to serve the extreme if there's a buyer who needs a ship to do that regularly. However, ships engaged in more irregular trade will want to tap into that source of profit. Some world, somewhere, may have a large load of taconite pellets or engine blocks to ship to some location equipped to deal with such loads. They may not to want to pay extra because the freight service can't handle the load, so ships like the free trader and subsidized merchant are likely to be equipped to serve those needs so they can get an edge on the competition.

 

[AnotherDilbert]

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...

~21 tonnes in ~2.7 Dt (~38 m³) gives me ~7.8 tonnes / Dt or 0.55 tonnes / m³? (Excluding the mass of the container).

 

[atpollard]

If the question here is the possible mass of cargo - in a Traveller universe with cargo ships traveling between stars to planets of varying tech levels, gravity levels, cultures, industrial bases, and sometimes species - then arguing for a standard does not give us an answer; it gives us a median.

I would argue that spacefaring ships that haul cargo under a wide variety of circumstances would be prepared to meet a wide variety of circumstances, or they would miss out on potential profits. The median is all well and good, and ships built to serve standard routes will likely be build to the median - or to serve the extreme if there's a buyer who needs a ship to do that regularly. However, ships engaged in more irregular trade will want to tap into that source of profit. Some world, somewhere, may have a large load of taconite pellets or engine blocks to ship to some location equipped to deal with such loads. They may not to want to pay extra because the freight service can't handle the load, so ships like the free trader and subsidized merchant are likely to be equipped to serve those needs so they can get an edge on the competition.

What about all of the other components of the transportation infrastructure?

What happens when there are no cranes that can lift the load? Then you bring in an excra heavy duty crane and the bottom falls out of the shipping container because it can't handle the load. So you transfer the load to a custom built container and there are no trucks designed to transport it at the destination world.

I think that is why for things like Gold or Lead ingots they use partially filled standard containers and accept the weight limits of the infrastructure.

The benefit for the starship sounds minimal. They can transport very heavy MBTs or mining equipment that cannot be broken into smaller units and are able to drive off, or loose bulk ores (not generally very profitable).

 

[kilemall]

If the question here is the possible mass of cargo - in a Traveller universe with cargo ships traveling between stars to planets of varying tech levels, gravity levels, cultures, industrial bases, and sometimes species - then arguing for a standard does not give us an answer; it gives us a median.

I would argue that spacefaring ships that haul cargo under a wide variety of circumstances would be prepared to meet a wide variety of circumstances, or they would miss out on potential profits. The median is all well and good, and ships built to serve standard routes will likely be build to the median - or to serve the extreme if there's a buyer who needs a ship to do that regularly. However, ships engaged in more irregular trade will want to tap into that source of profit. Some world, somewhere, may have a large load of taconite pellets or engine blocks to ship to some location equipped to deal with such loads. They may not to want to pay extra because the freight service can't handle the load, so ships like the free trader and subsidized merchant are likely to be equipped to serve those needs so they can get an edge on the competition.

You can read my take in the container thread. Basically, it's a business choice with higher risk/higher overhead/higher rewards, and a 4 man Free Trader may not be up to it. The standardized GC container with hazard devolving on the shipper may suit many people just fine.

 

[aramis]

~21 tonnes in ~2.7 Dt (~38 m³) gives me ~7.8 tonnes / Dt or 0.55 tonnes / m³? (Excluding the mass of the container).

You're ignoring tare weight of the container.

 

[AnotherDilbert]

You're ignoring tare weight of the container.

OK, ~24 tonnes in ~2.7 Dt (~38 m³) gives me ~8.9 tonnes / Dt or 0.6 tonnes / m³ (including the mass of the container). Far from 23 tonnes / dT?

 

[Carlobrand]

What about all of the other components of the transportation infrastructure?

What happens when there are no cranes that can lift the load? Then you bring in an excra heavy duty crane and the bottom falls out of the shipping container because it can't handle the load. So you transfer the load to a custom built container and there are no trucks designed to transport it at the destination world.

I think that is why for things like Gold or Lead ingots they use partially filled standard containers and accept the weight limits of the infrastructure.

The benefit for the starship sounds minimal. They can transport very heavy MBTs or mining equipment that cannot be broken into smaller units and are able to drive off, or loose bulk ores (not generally very profitable).

Depends on the receiver, I'd think. To assume all worlds are receiving the same things is a bit of a stretch. Some of these worlds have little more than a few hundred people and one major industry. Odds are their infrastructure will be suited to that industry. Again, the median is the median, not everything; there is profit in serving outliers. The Traveller universe is not a homogenous one.

 

[Terquem]

What's in our brain holders?

It has always been a bit of a curiosity, to me, that the "typical" Traveller fan is also an individual who is moderately (?) obsessed with the relationships, expressed through math, of space (volume), matter, and time

There were times when the "game" for me was just one long night of doing calculations on graph paper determining things I probably didn't need to know. :rofl:

 

[pigboy1537]

Wow

I didn't consider all the different variables that came with loading and unloading star ships. As of weight of cargo, it's going to vary with the item, what's it made of, the size of the world you picked it up and the world were you are dropping it off. Same goes for ships. The space shuttle on Earth weighs in at around 100 tons. What does it weigh when it docks to the space station? Weight changes as the mass changes in which it is docking to or rising from. It's great that there are some gamers that run the figures but for me I just use the Kiss analogy and Keep it Simple ........What ever floats your boat. I just glad to see us all out there that enjoy the game. Many thanks for all the replies.

 

[Xerxeskingofking]

I didn't consider all the different variables that came with loading and unloading star ships. As of weight of cargo, it's going to vary with the item, what's it made of, the size of the world you picked it up and the world were you are dropping it off.

yhea, well, we here have collectively been thinking about this for decades, so its not suprising that we are more aware of certain elements of physics.

Same goes for ships. The space shuttle on Earth weighs in at around 100 tons. What does it weigh when it docks to the space station? Weight changes as the mass changes in which it is docking to or rising from. It's great that there are some gamers that run the figures but for me I just use the Kiss analogy and Keep it Simple ........What ever floats your boat.

in short, it'd "weigh" nothing, but it'd mass the same. the lack of weight is just because it's in free-fall (the g in zero g is g-force, not gravity). and your right, KISS rules in a game environment like this one. no one here actually does the rocket fuel equasions and works out what a ship that can pull 2gs fully laden can do if it was 300 tons light on cargo.

I just glad to see us all out there that enjoy the game. Many thanks for all the replies.

your more than welcome/ anything you bring to the table is most welcome, even if we appear to rip it apart. we're just like that sometimes.

 

[esampson]

. . .no one here actually does the rocket fuel equasions and works out what a ship that can pull 2gs fully laden can do if it was 300 tons light on cargo . . .

Some of us do, but not for Traveller (because Traveller engines are fun magical mystery things). If I'm working out travel times for games like Eclipse Phase, however, I do actually use the Ideal Rocket Equation to figure out baselines for flight times (as well as programs like Celestia to figure out where various solar objects will be).

I still use fairly crude representations of the formula. I'm sure anyone with a ship who wanted to travel around the solar system would be appalled at my calculations, but they at least get me in the ballpark for time estimates that I then pad a little bit more to deal with traffic control, orbital alignment manuevers, minor course corrections, etc. to come up with a final figure that I am more than happy with.

Interestingly enough a lot of that has fed back into Traveller and given me a much better understanding of some things such as what landing procedures probably look like in Traveller (you shouldn't be dealing with fiery re-entries most people assume but should be coming much more straight down at relatively slow speeds).

 

[Timerover51]

Actually, the rocket equation is why I use a reactionless drive in My Traveller Universe. As it is, I am not a fan of boosting at more than 1G for any length of time. I have looked at the issue of whether the acceleration of a ship is in "Light" or "Loaded" condition, and assume that it would have to refer to the "Loaded" condition for planet departure. Then the question is what is the typical cargo weight per Traveller Displacement Ton to handle acceleration after a jump, when a lot of mass is gone from the ship.

For a Jump-6 warship, when you come out of Jump, your ship only masses 40 percent of what it did prior to jump, so the acceleration of your ship should increase by a factor of 2.5. So 2G would become 5G. That would not work for a merchant ship as the mass of the cargo would have to be taken into account.

 

[whartung]

Of course some might argue that a goal of a game design when it comes to things like this is to simplify them in order to make them "realistic", yet playable for the masses.

 

[AnotherDilbert]

For a Jump-6 warship, when you come out of Jump, your ship only masses 40 percent of what it did prior to jump, so the acceleration of your ship should increase by a factor of 2.5. So 2G would become 5G. That would not work for a merchant ship as the mass of the cargo would have to be taken into account.

Not even remotely. Liquid hydrogen is very light, only 1 tonne per Dt, less than 1/10 of water or ~1/100 of steel.

E.g. the 10 kDt ED-15 J-4 destroyer has an unloaded mass of 166674 tonnes and a fuel tank of ~5800 Dt = ~5800 tonnes.

If it does 4.0 G loaded, it would do 4 × (166674 + 5800) / 166674 ≈ 4.13 G without fuel.

 

[Timerover51]

Not even remotely. Liquid hydrogen is very light, only 1 tonne per Dt, less than 1/10 of water or ~1/100 of steel.

E.g. the 10 kDt ED-15 J-4 destroyer has an unloaded mass of 166674 tonnes and a fuel tank of ~5800 Dt = ~5800 tonnes.

If it does 4.0 G loaded, it would do 4 × (166674 + 5800) / 166674 ≈ 4.13 G without fuel.

Out of sheer curiosity, where are you getting your numbers for ship mass?

Now, an approximately 1400 Traveller Displacement Ton Liberty ship, built in World War 2, masses about 3500 tons light, ready for sailing but without cargo, fuel, reserve feed water, or supplies. Ten thousand Traveller displacement tons would equal about 50,000 Gross Register Tons in volume. Your destroyer would mass about 3.3 times its weight in steel than its volume in Gross Register Tons. In terms of water displacement, your destroyer has a volume of just under 143,000 displacement tons. Your ship is slightly heavier than the amount of water that it would displace, but not by much. Based on that, it is quite lightly built, and cannot have any significant armor.

 

[AnotherDilbert]

Out of sheer curiosity, where are you getting your numbers for ship mass?

MT Fighting Ships. It's not a very good example, but it is a canonical warship with the mass calculated.

It has medium armour (60G) that masses about 80 000 tonnes. Max armour (75G) would be ~300 000 tonnes.

Most equipment, even on warships is fairly light. Bays, for example, are very light. Drives are about 2 tonnes per m³.

 

[Carlobrand]

MT Fighting Ships is lousy canon. Lou. Sy. The thing is mostly errata. But, the ship mass is at least in the ball park. I'm actually showing it a bit heavier than what they get.

76,800 metric tons of just armor. Armor really weighs down the warships.

 

[aramis]

The armor of warships is 5 to 50cm of SG15 subperdense...

 

[infojunky]

MT Fighting Ships is lousy canon.

That book is commonly known as Shattered Ships of the Fighting Imperium.

 

[AnotherDilbert]

MT Fighting Ships is lousy canon. Lou. Sy. The thing is mostly errata. But, the ship mass is at least in the ball park.

I agree. It is also published in a known source, so fairly easy to access.

76,800 metric tons of just armor. Armor really weighs down the warships.

I get 79 600 tonnes: 3000 [base] × 190 [armour 60 thickness] × 0.14 [armour type mod].

That book is commonly known as Shattered Ships of the Fighting Imperium.

I agree the books is generally not very good, but the ED-15 destroyer is not a broken design, but roughly where a MT warship ends up, for mass at least.