Thoughts on a TU w/o captal starships

[AnotherDilbert]

Has anyone calculated the amount of trade available between systems in the Spinward Marches?

Gurps Far Trader has the rules for it. You might find some examples on CotI?

A quick estimate using the Gurps rules says that Regina trades about 9 MDt from the Spinward Marches, 0.5 MDt from Deneb, and even the Solomani Rim contributes about 0.007 MDt / year.

If we assume that each Imperial sector contributes roughly 0.01 MDt and some foreign trade we end up with roughly 10 MDt / year. That is in each direction, ~10 MDt export and ~10 MDt import.

Using the TEU as a conversion factor that is about 2 × 10 000 000 / 3 × 20 ≈ 130 million tonnes / year, somewhat smaller than a major shipping port today.

So the Port of Regina would handle ~55 000 Dt (~20 000 TEU, ~360 000 tonnes) cargo per day.

Major ports like Trin and Mora would handle ~32 times more, so ~1.7 MDt cargo per day.

For a comparison Shanghai handles about 35 000 000 TEU / year or 100 000 TEU / day.


Edit: Spreadsheet bug: I vastly overestimated trade from other sectors.

 

[AnotherDilbert]

If we assume that half the trade is inside the sector, with an average distance of 10 Pc and half the trade is to other sectors with an average distance of 100 Pc, we can estimate how many ships we would need.

Let's use the 5 kDt ship for simplicity.

Each local ship spends one week loading, three weeks jumping, another week loading, three weeks jumping back for a total of 8 weeks per trip or 6 trips per year, transporting 6 × 2500 ≈ 15 000 Dt per year in each direction, so 30 000 Dt total. Regina needs to transport ~9 MDt locally so needs 9 000 / 30 ≈ 300 local ships.

Each long-haul ship spends one week reloading, 35 weeks jumping, another week loading, 35 weeks jumping back for a total of 72 weeks or 0.7 trips per year, transporting 0.7 × 2500 Dt ≈ 1750 Dt per year in each direction, so 3 500 Dt total. Regina needs to transport ~1 MDt long-haul so needs 1 000 / 3.5 ≈ 285 long-haul ships.

So Regina needs ~600 such ships to carry freight. The ships would cost 600 × MCr 780 ≈ GCr 470. To replace them every 50 years would cost GCr 470 / 50 ≈ GCr 10.

Regina has a population of 700 million and hence a GWP of about TCr 7 (Travellerwiki says GCr 6 563). Building ships for GCr 10 is ~0.14% of the GWP, quite possible...


Edit: Spreadsheet bug: I vastly overestimated trade from other sectors.

 

[Nobby-W]

So, originally in CT, starships were limited in size to 5000 tons. So, I'm wondering how the TU would change if this was kept, and vessels like the Kinunir were top-line military starships, rather than relatively small support craft. Presumably, larger non-jump capable ships are possible, since I can't see any reason that they wouldn't be. However, what if there was a hard limit on jump-capable starships of 5000 tons, so that jump bubbles (or whatever) simply can't be made larger than this.
[ . . . ]

Commerce would be more expensive to a greater or lesser extent, as there would be less opportunity to get economies of scale. Scenes like the opening battle of Star Wars would remain in the realms of science fiction.

Having said that, 5,000 tons is still quite a large spaceship. Given that large wide-bodied airliner such as a Boeing 747 or an Airbus A380 is about equivalent in size to a 200-300 ton starship, a 5,000 ton ship is still a substantial piece of hardware. With double occupancy in the staterooms a 5,000 ton passenger liner could carry something like 1,000 passengers on a J3 route, more if it only supported J1 or J2. Freighters could still take a substantial amount of cargo. Commerce would have a preponderance of scheduled flights, more flights, more often.

Colonisation doesn't have to be done via a single, large colony ship. Fleets of ships could just as easily support a colonisation effort. Most of the new world was settled by folks travelling on ships that are a lot smaller than you might think. If you're in London, take a look at the Cutty Sark just down from the Borough Market - it's no bigger than a modern luxury yacht.

The actual effects on play would be that ships of a size that adventurers might actually use are more relevant. There isn't such a dichotomy between capital ships and everything else (although this was more a function of the balance in the HG rules than anything else).

I've done a 'small ships+' universe on a number of occasions. IMTU a large transport ship might go up to about 20,000-30,000 tons and warships max out in the 5,000-8,000 ton range. I did have to tweak the starship design and combat systems to make the balance work for ships this size, though.

 

[phavoc]

A cap of 100,000 Dtons for ships still makes it possible to have a full set of warships (Dreadnoughts all the way down to escorts) without gutting the game at all. 1,000,000 Dton battlehips are awesome and everything, but 100,000 Dton freighters are a bit large and break the idea of LOTS of ships traveling to and from other planets.

Having smaller ships actually does more to justify so many starports all over the Imperium, as it points to a smaller-ship, more frequent usage universe.

 

[Rikki Tikki Traveller]

I have quite frequently used a "medium-sized" universe.

Jump ships are limited to 5000 dtons, but non-jump ships can be bigger (usually up to about 20Ktons).

YES, it makes systems harder to invade, but it just means that empires have to be more creative it how they take over.

 

[baithammer]

Need to think about the scale issue, on our own planet we have 7.5 Billion people and shipping to support this is around 100,000 -400,000t for freight/tankers.

If jump ships are limited to 5,000t or less, the ability to support colonies becomes rather limited. ( Also rather hard to start colonies with the same tonnage limit.)

Basically you'd end up relying on jump ships for communication / scouting and having to use generation ships in order to colonize a world after a very careful survey to help colony viability.

Similar effect will occur in the military side of things, where the critical mass required to directly attack an opponent ends up using generation ships to get the warships / troop transports in system.

Jumping also presents a an issue for the maximum supportable landing/launching area for jump ships as well. With the large amount of traffic required your going to want a larger space between jumping ships in order to offset the risks of that volume of traffic.

 

[h1ro]

If jump ships are limited to 5,000t or less, the ability to support colonies becomes rather limited.

Another way of looking at this is you become more choosy over what planets you actually settle, opting for planets that can support themselves.

 

[phavoc]

Invading another star system should be a rough effort. Defenders have always had the benefit of static defenses. Think of how easy it would be to tow some asteroids into orbit, mount some missile racks on them and you have some very cheap battlestations. The negative thing associated with that is when the nukes start breaking up the asteroids, the chunks do have a tendency to drift downwards onto the planet they are protecting.

 

[AnotherDilbert]

If jump ships are limited to 5,000t or less, the ability to support colonies becomes rather limited. ( Also rather hard to start colonies with the same tonnage limit.)

Why? Just use more ships. The natural corollary to small ships is many more ships.

 

[baithammer]

Why? Just use more ships. The natural corollary to small ships is many more ships.

That would be adding to an already heavy traffic flow with an even greater need to space out the fleet for jumping in/out of system.

Where having access to stasis technology and fast sustained m-drives you could instead use generation ships to deliver a larger volume of colonists with supplies.

Also plays out with war, as the defender has way too much firepower available versus a jump fleet, a invasion fleet consisting of generation warships could arrive with sufficient numbers and match the ships that would be faced.

 

[h1ro]

Given the potentially hostile environment that colonist could be heading to, smaller numbers would make more sense to me. I'm guessing that you're talking about your own setting rather than the Third Imperium as most of the colonization was done centuries ago. (Granted there is plenty of space for further colonization but it doesn't feature heavily in published material).

Going back to an earlier post, the USA was colonized small ship at a time. What was the largest number of people off loaded from one ship?

 

[baithammer]

Going back to an earlier post, the USA was colonized small ship at a time. What was the largest number of people off loaded from one ship?

Took about 200 years before the thirteen colonies managed to get up around 200,000 population and most of the early settlements were temporary in order to harvest resources.

The analogy would be generation ships as that only involved one form of transport, flight would be more like jump tech and that isn't used for serious population changes until the 70s/80s.

Third Imperium

Which had the long night where some technologies were lost.

 

[Reynard]

Check out Tools for Frontier Living for 2300AD to understand colonizing worlds whether 2300AD or Traveller. A lot of colonies failed on Earth because of low populations and not having proper resources for the task. Remember very few worlds in Traveller are garden world so a lot more effort on every level need to be planned. You need ships able to carry enough manpower, supplies and equipment to do the job right. Dumping huge fleets of small liners and freighters could be a logistics nightmare especially if those ships need to be self sufficient without any port facilities at the colony site.

 

[heron61]

If jump ships are limited to 5,000t or less, the ability to support colonies becomes rather limited.

Another way of looking at this is you become more choosy over what planets you actually settle, opting for planets that can support themselves.

Indeed, settling barren airless rockballs is inherently difficult and wouldn't happen much. Also, you can easily fit 2,500 passengers (in low berths) in a colony ship, with plenty of room for supplies and equipment. A fleet of 40 colony ships gets you 100,000 initial colonists Pop 5), and the ships are reusable. I don't see any reason to need to resort of STL ships, since 40 5,000 tons ships isn't all that much more expensive than 1 200,000 ton ship (no more than 20% more) and gives you more flexibility, since after creating 20 colonies, you can send 1 ship out to each regularly to deliver more colonists and supplies in a gradual fashion (and the low berths can also be used to deliver domestic animals).

 

[AnotherDilbert]

Why? Just use more ships. The natural corollary to small ships is many more ships.

That would be adding to an already heavy traffic flow with an even greater need to space out the fleet for jumping in/out of system.

Where having access to stasis technology and fast sustained m-drives you could instead use generation ships to deliver a larger volume of colonists with supplies.

Space is big, we suffer no risk of running out of empty space...

A 5 kDt jump ship can obviously deliver more cargo/colonists per year than much more expensive 50 kDt sublight ship.

At, say 5 Pc and J-3, a jump ship can do ~6 trips per year vs. less than one trip per decade for the sublight ship. When the sublight ship first arrives the jump ship will already have made perhaps 40 trips delivering in the region of 100 kDt payload.

 

[baithammer]

Considering commercial vessels are built to tl12 standards and don't used high-tech options, the 5dt with 2,500 colonists ends up around .24 t per colonist which will end up needing more ships to cover the cargo.

Space is big, we suffer no risk of running out of empty space...

A lot of space within a system is inaccessible to jump traffic due to planetary bodies and ship sized objects, also due to the 5kdt limit you have a lot more convoy traffic that require far more spacing then larger jump freighter traffic. On top of that you have to consider security denial to sections of space as well.

 

[h1ro]

A lot of space within a system is inaccessible to jump traffic due to planetary bodies and ship sized objects

I'm not sure where you're getting the numbers from to back this up.

Respectfully, I think you're underestimating the size of space.

 

[baithammer]

Could said that you might be over estimating the usable space for jump traffic as you want to be as close to the limit as possible without running the risk of jumping in on another vessel already present in the target area.

Further, in order to secure the most vulnerable points the security/military would take steps to make areas inaccessible to jump traffic.

With a 5kdt limit and considering a scale equal to the 3rd Imperium that would push landing points further out than a smaller amount of larger vessels.

If you adjust settled space to take into account the jump limit the population size and density would be far more contracted in order to make supply/trade viable. ( Also less worlds would be considered for colonization as there would be an increased requirement towards reducing in bound supplies.)

 

[h1ro]

Could said that you might be over estimating the usable space for jump traffic as you want to be as close to the limit as possible without running the risk of jumping in on another vessel already present in the target area.

OK, educate me, how big is that space?

 

[baithammer]

A little food for thought.

If a 5kdt is both thrust 1 and Jump 1 to maximize cargo, the safe zone required is thrust 1 travel @ 148 + 6D hours so 184 hrs to get radius with 1,096,934,400,000 m.

As we're dealing with 3d space we need the volume, which is 5,525,993,291,587,398,590,791,680,000,000,000,000 m^3 for one 5kdt ship to land safely on jump. ( Especially since the craft can't communicate with real space)

Earth type planet minimum jump limit is 318,500,000 m radius and takes up 101,451,379,802,500,000,000,000,000 m^3.