Shipyard Capacity

[Garnfellow]

In playing around with GURPS Traveller: Spaceports, I was looking at the shipyard rules on page 80: "Total shipyard capacity in displacement tons usually is equal to weekly trade tonnage divided by 12 at Class IV ports or 8 at Class V [A] ports, then rounded up to the next standard hull size where applicable. . . . The shipyard can produce one vessel at its capacity size per year, or any combination of smaller vessels totaling that tonnage in a year’s production."

The tonnage is related to port capacity (rated 0-9), which is unrelated to port class -- that is, what amenities are available. So you could have a very large volume of trade passing through a Class C starport on a major trade route, or a very small volume passing through a Class A starport that is very far off the beaten path.

In looking at Dark Nebula, Magyar, and Solomani Rim economic data on the wiki I was struck by the relatively small port sizes in those sectors. There are no size 8 or 9 ports and relatively few class 7 ports. Even Kusyu, center of the Aslan Hierate, has only a size 6 port.

What does this mean? Well, if I understand the GURPS rules here, shipbuilding capabilities seem pretty anemic.

A size 6 port, for example, has an annual trade volume of 1-10 million dtons, or 20,000 to 200,000 dtons per week. Divide this by 8 and you get a shipyard capacity of 2,500 to 25,000 dtons. A naval base doubles this capacity.

So Kusyu, revered homeworld of the Aslan, can churn out maybe 50,000 dtons of starship a year? Basically, one cruiser?

Or Terra -- a size 7 port -- limited to 500,000 dtons? Two, maybe three battleships a year?

Or have I got this wrong? I prefer smaller fleet sizes in MTU, but these numbers seem as bad as the TCS numbers, just at the other end of the spectrum.

 

[Timerover51]

Here are links to a couple of posts regarding ship production that I put up in another thread.

In the Real World, there are a few ways to determine production capacity in certain industries.

For a long time in nautical construction, it was assumed that in a shipyard, reasonably well equipped, the output per year per worker was 10 displacement tons of ship. That rule of thumb worked reasonably well for both wooden and metal commercial ship production. Mass produced ships like the WW2 Liberty class would be built at about twice that rate, although it was possible to rush them through very quickly for publicity purposes. Military ship building times could vary enormously, depending on material priority and how much electronics was being included in the design. Electronics tended to slow building times quite a bit.

In the aircraft industry, the assumption prior to WW2 was about one pound of airframe weight per worker per day, and for engines, about 1 horsepower of engine per hour of work. That was boosted quite a bit in mass-production in WW2, but you are thinking of thousands of aircraft being built. The aircraft airframe weight DID NOT include the engine weight, which is why I show a separate figure for the engines. Electronics changed those figures quite a bit, along with the more complex high-pressure axial jet engines.

Lastly, you can use value-added per worker as a basis, or displacement ton assembled per worker. Remember, a commercial Traveller ship is primary a combination of drives (jump and maneuver), power plant, accommodations, and electronics and controls contained in a hull. The drives and power plant may be produced elsewhere along with the electronics and controls, while the accommodations may be mass-produced and stockpiled until needed. A very large shipyard may be able to produce everything on site, while a smaller shipyard would bring some items in, such as drives and power plants, while all yards would be bringing in the electronics and controls.

As Traveller, at least as far as I know, has no provision for differing costs of living at different Tech Levels, a simple approach to how many workers would it take to produce a ship in a given period of time would be to decide on the likely average pay for a shipyard worker, then double that to determine the value the worker could produce in one year. Personally, I would double the building costs if done in orbit, along with doubling the building time. If you allow for shift work to speed things up, typically, the production rate of the second and third shift is about 80% of a day shift.

From that you work up the likely population of the starport and world and go from there. Again, my view is that the minimum population of a world to totally build a starship from scratch, to include all components, is 10 million and up, regardless of Tech Level. To assemble components shipped in into a finished ship, I assume a minimum population of a million, with the million pushing the limit pretty closely.

As for the difference between A and B class spaceports, I figure that A-class ports can build from scratch, B-class ports import some items, but can still build starships, C-class ports have some repair capability and can build the odd ship or two, while D-class and E-class are not in the running.

Going back to the original question as to ship production, I have been re-reading a book for my summer history class called The Liberty Ships, by L. A. Sawyer and W. H. Mitchell, which is a history of the Liberty Ships built during World War 2, and includes a fair amount of construction information. Some of the very large yards which were turning out a dozen or so ships a month employed in excess of 20,000 workers, and relied heavily on pre-fabricated sections being shipped in, with the engine machinery being outsourced and then brought it. A Liberty would equate to a very simple 1420 Traveller dTon ship, basically a powered steel box. Typical ship assembly time was running about 60 days or so in the best yards. The first ship, the "Patrick Henry" took 242 days to build. Based on this, for the best yards, the construction rate was equivalent to about 10 Traveller dTons per worker per year. That is a rough but reasonable estimate, but for a very basic steel hull. It should be noted that over 2700 Liberty ships were built. I am not sure how many Traveller ships would be built in terms of 144 of the same ship by the same yard in one year.

The 1981 edition of book 2 of the LBB gives the construction time of a standard 1000 dTon hull of 27 months, and for a custom 1000 Traveller dTon hull of 30 months. That does not strike me as a reasonable difference in building speeds, but it is what we have to work with. I would expect a standard ship to be built considerably faster than only a 10% difference. Working from the 10 Traveller dTons per worker for a basic steel box in mass production, it probably would be safe to say that a very efficient yard assembling ships, where the basic hull is constructed from scratch at the yard, with drives and electronics being brought in from elsewhere, you could get an assembly rate of 2.5 Traveller dTons per worker per year for commercial vessels primarily carrying cargo. The limitations as to how many workers could be used on a vessel at one time would account for the minimum building times.

Therefor to build a custom 1000 dTon ship in 30 months would require a construction force of 160 persons. Not all of those would actually be working on the ship, as you would have administrative and support staff included as well. To produce say 5000 Traveller dTons of commercial ships per year would require a staff of 2000 persons. With that, you could produce 25 Free Traders a year, not a negligible quantity.

Based on the construction times of military ships in World War 2 that were in mass production, I would say that the average worker could assemble 1 (One) Traveller dTons of military ships per year. I understand that would play havoc with the idea of 100,000 to 500,000 Traveller dTon warships in terms of manpower to construct them, but that would be up to the Game Master.

If you then take the number of workers in the shipyard and multiply it by about 10, you can get an idea of the size of the community the shipyard is located in. This, in turn, would set the minimum planetary populations of Class A and Class B starports, as the Class B can build non-starships, which only lack the Jump Drive. As jump drives could be shipped in, I am not exactly in favor of that distinction. I would say that a better distinction between Class A and Class B starports would be that a Class A starport always has a High Port, while the Class B does not. Note, this would also increase the population of planets with Class A starports to support the High Port. I take the view that not all Class A and Class B starports have building yards, as some of the planets with A and B starports have very small populations of 4 or less. See the Spinward Marches supplement for examples.

 

[whartung]

I prefer smaller fleet sizes in MTU, but these numbers seem as bad as the TCS numbers, just at the other end of the spectrum.

Well, seems to me, they're trying to tie shipyard capacity to the necessity for it.

If you're not trading, you don't really need ships to trade.

A 25K dTon Book 5 freighter has about 17000 dTons free for cargo.

On earth, we deal with "TEUs", "twenty foot equivalent units" to represent containers. A TEU is ~42m3

17000 dTons, at 1400m3 per dTon, is 714000 TEUs.

Currently, we apparently have about 3M TEUs of cargo shipping waiting to be built over the next 5 years. That's 600K TEUs per year. So, 1 25K dTon ship easily covers that.

All told, we have 19M TEUs of active shipping on the world right now, 570K dTons worth.

I simply toss these rough figures out to give an idea of scope.

A shipyard that can produce a 25K dTon ship per year, is quite a bit of shipping potential.

A Free Trader: 75 tons cargo * 1400m3 / 42m3 = 2500 containers!! I mean, "zoiks". That's not nothing.

1 dTon is just over 30 containers. (and it should be noted that most cargo is moved in 2 TEU containers, those are the ones that fit well on a semi truck, so 15 semi trailers.)

2014 Global TEUs exported from top 20 exporters is 127M TEUs. 3.8MdTons, annually. ~75K per week.

 

[Timerover51]

Now, I should add that I have never seen GURPS Traveller, so I do not know anything about it, but I do know a few things about ship production, and also cargo handling. Ten million Traveller dTons of cargo a year is a lot of cargo to handle, regardless of what GURPS rules say. Converting that into mass tons at the rate of 5 mass tons per Traveller dTon, and you have basically the mass of the non-petroleum imports to the United Kingdom for a year immediately prior to World War 2. To handle that volume, the UK depended on several major ports. Admittedly that was before the days of container ships and a lot of the cargo was of the break-bulk variety, but a lot of the cargo such as wheat, other grains, fertilizer, and ore imports was done by bulk carriers, along with a lot of lumber imports that were close to being containerized, being carried in large pallets.

Check out the CIA World Factbook for the volume of imports of some Real World countries here on Earth to get some idea as to how big some of those ports in GURPS Traveller are actually going to have to be, and adjust your ship-building capabilities accordingly.

 

[Timerover51]

Well, seems to me, they're trying to tie shipyard capacity to the necessity for it.

If you're not trading, you don't really need ships to trade.

A 25K dTon Book 5 freighter has about 17000 dTons free for cargo.

On earth, we deal with "TEUs", "twenty foot equivalent units" to represent containers. A TEU is ~42m3

17000 dTons, at 1400m3 per dTon, is 714000 TEUs.

Currently, we apparently have about 3M TEUs of cargo shipping waiting to be built over the next 5 years. That's 600K TEUs per year. So, 1 25K dTon ship easily covers that.

All told, we have 19M TEUs of active shipping on the world right now, 570K dTons worth.

I simply toss these rough figures out to give an idea of scope.

A shipyard that can produce a 25K dTon ship per year, is quite a bit of shipping potential.

A Free Trader: 75 tons cargo * 1400m3 / 42m3 = 2500 containers!! I mean, "zoiks". That's not nothing.

1 dTon is just over 30 containers. (and it should be noted that most cargo is moved in 2 TEU containers, those are the ones that fit well on a semi truck, so 15 semi trailers.)

2014 Global TEUs exported from top 20 exporters is 127M TEUs. 3.8MdTons, annually. ~75K per week.

You need to check your math. A Traveller dTon is defined as either the volume of a metric ton of Liquid Hydrogen, which is just about 14 cubic meters, or a volume equal to 13.5 cubic meters.

75 tons cargo * 1400m3 / 42m3 = 2500 containers!!

1400 cubic meters divided by 42 cubic meters comes out on my calculator as 33.3 containers. Seventy-five dTons of cargo volume equals 1050 cubic meters on my calculator, at 75 X 14 cubic meters per dTon.

 

[Garnfellow]

Well, I was looking into this specifically with regards to capital ships. So most Imperial sectors have at least a handful of size 7 ports, though not all of these have class A facilities and even fewer are TL15. A size 7 port with a naval base can build up to 200,000dt ships in one year -- a single Plankwell.

But a quick spin through the wiki showed only THREE size 8 ports in the Imperium, all in Old Expanses. Not even Core sector has a single size 8 port.

These three systems, fortunately, have Class A starports and TL15, making them the only places in the entire Imperium that could build 500,000dt Tigress-class dreadnoughts based on GT: Starports.

 

[kilemall]

I was going to suggest Timerover's method of 1 dton per worker.

So then the question is how do you determine how many workers?

Without knowing GT's nuances, may I suggest the following-

During wartime- 1% of population.

Peacetime- . 25% of population.

IND or GT equivalent- x2.

Non-IND or GT equivalent- /4.

 

[Ex_Pendable]

You need to check your math. A Traveller dTon is defined as either the volume of a metric ton of Liquid Hydrogen, which is just about 14 cubic meters, or a volume equal to 13.5 cubic meters.

To help put some of these numbers in perspective:

20 Ft. Shipping container has 25 cubic meters capacity.
40 Ft. Shipping container has 55 cubic meters capacity.

 

[Adam Dray]

What are the dimensions of a 40-foot container? 40x40x40? So 8 times the volume of a 20-foot container?

If a 20-footer is 25 cu m, I'd think a 40-footer is either 50 cu m (40x20x20) or 200 cu m (40x40x40). Where do you get 55?

 

[aramis]

What are the dimensions of a 40-foot container? 40x40x40? So 8 times the volume of a 20-foot container?

If a 20-footer is 25 cu m, I'd think a 40-footer is either 50 cu m (40x20x20) or 200 cu m (40x40x40). Where do you get 55?

Look up TEU (Twenty Foot Equivalent Unit)

A "standard" shipping container is 8'6" x 8' x Length.
A "high cube" is 9' 6" x 8' x length.
1 TEU is a maximum of 20' high cube, for 9.5 x 8 x 20 feet = 1520 cu ft, with a 53000 lb limit, for which 5050 is the tare weight.

So, in metric: 43.04 cubic meters, 24 tonnes mass, 2.29 tonnes tare.

Its a mass/volume combined value.

1TEU is right about 3 Td by volume, and using the TNE mass limit of 10 tonnes per Td, it's less dense than the Td.

A 40' is 6 td.

 

[Ex_Pendable]

You're forgetting about the end fittings. As there is no break in the center of a 40 ft. shipping container, it will hold more than two 20 ft. shipping containers laid end to end.

 

[whartung]

Yea, sorry about the math. What's a couple orders of magnitude between friends.

Reminds me of my Geometry final in high school. Now, mind, I was GOOD at geometry. Took to it like a dog to water.

But on the final, I just could not figure out this one problem. Spent a solid 10 minutes on it.

I gave up and turned it in, but I asked the teacher about it.

He says, "Well, first off a triangle has 180 degrees"

"Stop! That's it, that was my problem."

For whatever crazed fever dream reason, I was convinced, at least for that problem, that a triangle has 190 degrees. No wonder it never worked.

 

[Adam Dray]

Wikipedia's "Twenty-foot equivalent unit" page gives 33.2 cu m for a 20 ft TEU and 67 cu m for a 40 ft TEU, which jives with none of the math above:

Length	Width	Height	Volume	TEU
20 ft (6.1 m)	8 ft (2.44 m)	8 ft 6 in (2.59 m)	1,172 cu ft (33.2 m3)	1
40 ft (12.2 m)	8 ft (2.44 m)	8 ft 6 in (2.59 m)	2,377 cu ft (67 m3)	2

 

[kilemall]

Look up TEU (Twenty Foot Equivalent Unit)

A "standard" shipping container is 8'6" x 8' x Length.
A "high cube" is 9' 6" x 8' x length.
1 TEU is a maximum of 20' high cube, for 9.5 x 8 x 20 feet = 1520 cu ft, with a 53000 lb limit, for which 5050 is the tare weight.

So, in metric: 43.04 cubic meters, 24 tonnes mass, 2.29 tonnes tare.

Its a mass/volume combined value.

1TEU is right about 3 Td by volume, and using the TNE mass limit of 10 tonnes per Td, it's less dense than the Td.

A 40' is 6 td.

I'd done the math years ago when I did my IMTU container rules. IMTU containers are bigger then their terrestrial equivalents and are sized for 5 and 10 tons.

Among other things, I'm figuring most commercial transport is not limited to current Terran roads, and follow-on colonies will size their space bays, railroads, water ships and roads to the larger container standard.

 

[Ex_Pendable]

I'd done the math years ago when I did my IMTU container rules. IMTU containers are bigger then their terrestrial equivalents and are sized for 5 and 10 tons.

Among other things, I'm figuring most commercial transport is not limited to current Terran roads, and follow-on colonies will size their space bays, railroads, water ships and roads to the larger container standard.

It's usually best to go with the standard, fewer problems that way.

 

[kilemall]

I was going to suggest Timerover's method of 1 dton per worker.

So then the question is how do you determine how many workers?

Without knowing GT's nuances, may I suggest the following-

During wartime- 1% of population.

Peacetime- . 25% of population.

IND or GT equivalent- x2.

Non-IND or GT equivalent- /4.

This is too stupid much for those 90 billion pop IND planets- 1.8 billion tons per year wartime/ 225 million peacetime strains even the most incredulous numbers for big ship/big fleet universes.

TL should be an efficiency multiplier too.

Scales down nicely for smaller A and B starports, and nicely explains those 12-month plus build times out on the frontier for small ships.

Would also be interesting to determine repair capacity and rates by population, that limits the amount of new builds that can be done.

Need a formula for the bigger pop planets that doesn't create a monster.

 

[aramis]

I'd done the math years ago when I did my IMTU container rules. IMTU containers are bigger then their terrestrial equivalents and are sized for 5 and 10 tons.

Among other things, I'm figuring most commercial transport is not limited to current Terran roads, and follow-on colonies will size their space bays, railroads, water ships and roads to the larger container standard.

OTU uses 4 Td - see TTA p 133. Reference is made to similar in text in other locations.

 

[kilemall]

Hmmm, more useful for me, stuck in CT, to use 5-ton and 10-ton for the shipping lots. The OTU can do what it wants.