2017-07-11 Traveller vs. Traveller

I’ve been comparing the subsector generation of Mongoose Traveller (MGT) and Classic Traveller (CT) in the incarnation of The Traveller Book.

Here’s what I noticed:

The distribution of starports is different. Note how Classic Traveller has only a bit less D and a lot more A starports.


Bases are different: Mongoose Traveller has Research, Traveller Association, Imperial Consulate and Pirate bases; Classic Traveller only has Naval and Scout bases.

Temperature is different: Classic Traveller does not have it. Then again, I was always confused by the fact that it doesn’t show up in the Mongoose Traveller Universal World Profile (UWP).

Hydro is different: Mongoose Traveller has a modifier for temperature; Classic Traveller does not. That explains why temperature doesn’t appear in the UWP: it wasn’t used by CT.

Population is the same and limited to a maximum of A when rolling, but the table in Mongoose Traveller also describes B and C. Perhaps this is a nod to Coruscant, the world city in Star Wars?

Government is the same and produces a range of -4 to 15 (F) when rolling. Both only describe governments 0 to 13 (D), however. How strange.

But reddit has the answer:

E Religious Autocracy. Government by a single religious leader having absolute power over the citizenry

F Totalitarian Oligarchy. Government by an all-powerful minority which maintains absolute control through widespread coercion and oppression

– MegaTraveller Referee’s Manual, apparently

Law is similar in that the dice throw produces a range of -5 to 15 when rolling, assuming we limit Government to 0 to 10 (A). Mongoose Traveller only describes Law 0 to 9; Classic Traveller describes Law 0 to 10 (A).

Tech is different. Mongoose Traveller has modifiers in the table for populations B and C, but you can’t get more than A so this is a bit strange. Mongoose Traveller increases Tech by +1 if you have Hydro 0. Mongoose Traveller increases Tech by +2 if you have Government 7 (Balkanisation), which is weird. Mongoose Traveller decreases Tech by -2 for Government 12 and 13 (charismatic oligarchy and religious dictatorship); Classic Traveller only does this for Government 12. No penalties for religious dictators, I guess.

Trade is also different, mainly in that some codes are missing in Classic Traveller: Barren (Ba), Fluid Oceans (Fl), Garden (Ga), High Population (Hi), High Technology (Ht), Low Population (Lo), Low Technology (Lt).

Travel Codes (Red, Amber) are not codified in Classic Traveller; Mongoose Traveller suggests when to use the Amber code.

Routes appear only in Mongoose Traveller.

The pirate bases, the travel codes, and the routes sure make the maps generated for Mongoose Traveller more interesting to look at.

Here is an example subsector generated. Notice the limited bases created.

Traveller Subsector UWP List Generator (1619343301)

Tizita           0102  C41058A-11          NI A
Vibannare        0105  D7A38A6-3           A
Nafaxe           0204  E447301-4           NI A
Zititu           0207  B648663-7       S   Ag NI
Mavifainti       0208  X3016AB-3           Na NI Va IC A
Pavima           0210  D200103-6           NI Va A
Vinxena          0301  D88A644-8       S   NI Ri Wa
Zoziq            0302  B454842-8          
Tituteluzi       0305  A310420-12          NI A
Rabama           0306  B545412-8       N   NI
Totamavi         0310  B678563-7       N   Ag NI
Zon              0401  E88A522-7           NI Wa
Qnq              0410  C87997A-11          In A
Mavota           0504  A99A977-12          In Wa A
Razutife         0505  B754867-8       S  
Zomanzi          0507  D67A355-10      S   NI Wa
Vizoetuvo        0508  B120510-12          NI Po De A
Lurinan          0509  C4555A8-9           Ag NI A
Zotato           0510  A66A632-9           NI Wa
Lunainrina       0601  B747564-6       N   Ag NI
Rizo             0604  B77A7BF-8       S   Wa A
Lutomata         0605  C9769CF-6           In A
Patoin           0607  A436784-13         
Ineratu          0608  A978753-11      S   Ag
Zozota           0610  C220202-10          NI Po De A
Femavita         0701  A302666-10          Na NI Va IC
Titutemana       0703  BA9A796-12     NS   Wa
Titezofa         0705  C99A543-6       S   NI Wa
Favorivi         0709  C130383-11          NI Po De
Qtelu            0710  AAA9000-0           NI A
Nnafema          0802  C5376B9-5           NI A
Tuzinare         0803  A564304-12          NI A
Zupaezi          0804  B210964-12      N   Na In
Zoreluzu         0805  C78A589-6           NI Wa A
Tofevomaq        0806  A200756-10      N   Na Va
Texebain         0807  C4428AE-7           Po A
Favifabafa       0808  B99A88C-11      N   Wa A
Reinxenazi       0809  B401588-8           NI Va IC
Zufate           0810  B9C8644-8           NI A
                       ||||||| |
Ag Agricultural        ||||||| |            In Industrial
As Asteroid            ||||||| +- Tech      Lo Low Population
Ba Barren              ||||||+- Law         Lt Low Technology
De Desert              |||||+- Government   Na Non-Agricultural
Fl Fluid Oceans        ||||+- Population    NI Non-Industrial
Ga Garden              |||+- Hydro          Po Poor
Hi High Population     ||+- Atmosphere      Ri Rich
Ht High Technology     |+- Size             Wa Water World
IC Ice-Capped          +- Starport          Va Vacuum

Bases: Naval – Scout – Research – TAS – Consulate – Pirate

I’ve left the Mongoose Traveller suggestions for routes in place and this is what we get:

Classic Subsector

(If you click the image, you’re going to see the Traveller Subsector Generator with a secret parameter for creating Classic Traveller maps.)

On G+, I got linked to TRAVELLER: Out of the Box – Interlude: Two Points Where I Prefer the 1977 Edition Over the 1981 Edition talking about the old 1977 trade routes. When I tried it, not bad! (Also note this forum thread, Default CT 1977 and CT 1981, comparing the 1977 and 1981 editions.)

Classic Subsector

(Classic Traveller map, with minimal spanning tree)

I decided to drop the optimising I had been doing, to get a feel for the “raw” data. This also required some rewriting and this always messes with the random number generator. That’s why this map cannot be easily compared to the one above.

Classic Subsector

I did some rewriting and added the minimal spanning tree algorithm again. It looks less busy, the clusters are still clusters. But there are some drawbacks. Take a look at the top right corner: 0802 and 0703 are connected (distance 1, shorter connections go first), 0701 and 0703 are connected (distance 2), and thus 0701 and 0802 cannot be connected because that would introduce a loop.

Classic Subsector

(Classic Traveller map, with minimal spanning tree)

I think for the time being I’ll remove the minimal spanning tree optimisation again.



There should be a space lane between 0601 and 0701 by the 1977 rules (A-B J-1 is 1+ to have a space lane). Also 0504-0505 and 0508-0607, hmm and a bunch more...

– Frank Filz 2017-07-13 07:31 UTC

Indeed! A bug!

– Alex Schroeder 2017-07-13 09:25 UTC

New code produces:


– Alex Schroeder 2017-07-13 09:35 UTC

Highlighting jump-1 routes:


Not sure about the colour scheme. And the legend at the bottom needs fixing.

– Alex Schroeder 2017-07-13 10:59 UTC

Nice, I like the red to highlight the J-1. When I did my subsectors, I ended up not rolling for the J-3 and J-4 routes. I also didn’t bother with a J-2 route that was already connected by J-1 (for example 0604-0804 above, there’s already an implied J-2 route as 0604-0705-0804). Similarly you could remove the 0305-0604 J-3 route (unless there isn’t a J-2 between 0305-0505 and that blue line is actually JUST a J-4 route 0305-0705...).

– Frank Filz 2017-07-13 16:28 UTC

Hm... Isn’t that a bit like the minimum spanning tree optimisation? As Ian Borchardt said on G+:

One problem with your optimised paths is that you are assuming that space == time, which isn’t the case with Traveller jumps, because any jump takes two weeks, regardless of distance. [IIRC]

Which means it’s not cheaper (time wise) for a starship to call in at an intermediate port. So given a choice between A-B-A and A-A most people will still choose A-A by preference because it gets there in half the time. It has a greater efficiency.

I responded with the following:

As for trade route optimisation: one might say that the trade routes indicate the most popular trade routes and thus two jump-2 segments will be more popular than a single jump-4 segment because there will be more ships that can handle it, even if that makes the route take twice the time. Well, that was my argument when I realised that too many routes just made for an ugly map.

So basically the jump-2 route 0604-0804 says that ships can and will make this jump directly – unlike the jump 0604-0703, which is also a jump-2 but somehow the dice have decided that it’s not profitable enough to do. It’s up to the referee to explain the difference. At least, that’s Ian’s argument.

For myself, I’m still undecided. All I can say is that it looks busy and messy and I don’t like it too much.

As for distance, I guess from a player perspective, at the beginning of a typical campaign all we care about are jump-1 and jump-2 routes. Perhaps I should just use a third colour for jump-2 routes.

– Alex 2017-07-13 16:52 UTC

Support for sectors, click to zoom. Note how I used a third color for jump-2 routes.

Click to zoom!

– Alex 2017-07-13 18:03 UTC

D’oh. I just noticed that my generator never generated any gas giants. Fixed!

This also means that all the random seeds will now generate different maps. Nooooo!

– Alex 2017-07-13 18:33 UTC

As for picking a subsector capital, Ian Borchardt says:

Definitely an A class spaceport (and it will have an attached Imperial naval and scout base). It probably should be a Rich world (Atmosphere 6-8, Population 6-8), and I’d assign it a Government Type of 8. The TL should be amongst the highest in the subsector (and a minimum of 12).

And regarding trade routes, he says:

This is the approach I would take.

First generate the main routes.

(1) Connect all Starport A within Jump 2 of each other.
(2a) Connect all Starport B within Jump 2 of a Starport A.
(2b) Connect all Starport B within Jump 1 or each other.
(2c) Connect an unconnected Starport B to another Starport B within Jump 2.

If a connection in step 2 connects Starport A to the sector capital then upgrade it to a main route.

Next comes the feeder routes.

(3a) Connect Starport C to a single Starport A within 1 jump.
(3b) If not connected, connect Starport C to a single Starport B within Jump 1.
(3c) If not connected, connect Starport C to a single Starport A within Jump 2.
(3d) If not connected, connect Starport C to a single Starport A within Jump 2.
(4a) Connect Starport D to a single Starport A within 1 Jump. (optional)
(5) Class E starports are never connected by a trade route.

If in need of direction, assume the shortest path to the subsector capital.

This defines the regular services (for various definitions of regular). Everything else relies on tramp freighters.

[In your example map the small disconnected group of systems to coreward might have better trade connections to coreward than it does with the subsector it is technically a part of. Or it may be a different polity. And yes, I cheated with the rosette of class A and C starports to rimward, because of a fondness for benzene rings...]

– Alex Schroeder 2017-07-13 22:31 UTC

One thing I did to simplify my route maps is that if you have three worlds, One, Two, and Three, and there is a J-1 route from One to Two, and a J-1 route from Two to Three, I also assume the J-2 route from One to Three is also regularly travelled. I also in a few places, having rolled just the J-2 route, assumed that the J-1 routes were thus also regularly travelled (this makes a world that might otherwise have had less access have more, I’m not that bothered by that, and would rather have a simpler map).

– Frank Filz 2017-07-31 16:02 UTC

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