Tag Archives: Sector

The Nine Sectors

If you recall, local space in this setting looks roughly like this:

adj-02aThe highlighted area is the area covered by our map – 3×3 sectors – with the central one, marked with a small “X”, the main sector the setting is all about. Coreward is up, Outward is down, Spinward is left and Trailing is right.

In order to create this central sector, we do need to know what’s just outside them, so I have been creating those other eight sectors’ worth of planets. I will not really check them or fix them up, except for regions that are actually important to my effort. This means all systems that I need to create trade routes to (so I can add them to my map) and a small section in the right-hand sector into which Empire has extended.

These are the tentative names I’ve picked:


Some notes:

Core: This is the core of colonial space. The empire/republic are here, and most of the important colonies. The border of this sector is pretty much the “edge of civilization”.

Expanses: Imperial colonisation and expansion was mostly directed towards this sector. It is a fairly sparse sector.

Frontier: This is an attractive sector with a dense population of star systems. From the Imperial/Republic Core sector it is only reachable via two key routes, and it is almost entirely unexplored.

Nebula: Dense interstellar gas clouds dominate this region, and many systems in this sector are fairly young. There is little usable real estate in this sector, and astrogation is hazardous.

Void: As the name implies, systems are scarce in this sector, but it is essentially divided into two regions. The more coreward void region, and a more outward-laying cluster of star systems.

Sentinel: The original colonists approached from this direction; it is a sector comparable to Core in terms of system density. Several smaller interstellar nations exist close to Core sector, and Empire (and now Republic) does extend about one subsector into the Sentinel sector. Exploration does not extend far into this direction, however, and all of the logs and astrogational data from the original fleet has been lost.

Islands: Several small startclusters dominate this sector, separated by great distances which make travel complicated.

Marches: Another frontier region pegged for expansion by Imperial authorities. However, since it is slightly further away and several other nations are in between Empire and the Marches sector, exploration projects had emphasized the coreward directions. It is unknown what, if any, expansion the Republic will undertake. The sector itself is fairly sparse in star systems close to Core sectors, but the outer region of the Marches is dense in stars.

Tempest: This sector is remarkable for an unusually high number of asteroid belts, nova remnants, and dead worlds – that is, worlds where life had once existed, but which are now sterile. The cause is unknown.

People, People Everywhere (High Population Worlds, Part 1)

One thing you will remember from when we looked at the dice results for this sector was the insanely high total population – 2663 billion people – for what is supposed to be frontier-ish.

This is really due to four population code B worlds – that is, 100 billion or more inhabitants. I’ve already downgraded one of them. In addition, the sector contains 8 worlds inhabited by between 10 and 100 billion people:

(5)Temperate 1429 AA8ABB9-G Hi Ht Wa     HI5 834.000.000.000 (5)Temperate
(8)Temperate 0516 A763BD9-C Hi Ht       HI8 482.000.000.000 (8)Temperate
(3)Temperate 2614 BAA5BD9-7 Fl Hi       HI3 (3)Temperate
(8)Temperate 2917 B888AA9-7 Ga Hi       HI8 95.700.000.000 (8)Temperate
(3)Temperate 2611 A400A96-D Hi Ht In Na Va HI3 (3)Temperate
(8)Temperate 1418 C785A96-8 Ga Hi       HI8 61.700.000.000 (8)Temperate
(7)Temperate 2135 B784A89-7 Ga Hi       HI7 (7)Temperate
(5)Temperate 1113 A8A5A89-D Fl Hi Ht     HI5 30.500.000.000 (5)Temperate
(4)Hot 1935 B743A88-9 Hi In Po     HI4 15.700.000.000 (4)Hot
(3)Temperate 0305 B410AD9-B Hi In Na     HI3 (3)Temperate
Xoth 2219 A576A85-A Ga Hi In     HI7 (7)Temperate

Is this even possible?

From a pure math standpoint, absolutely. Earth’s population has increased dramatically over the past few centuries, as better agriculture and medicine reduced mortality – especially child mortality. When I was a kid, the world’s population hit 5 billion people. I remember the TV gala; for some weird reason people actually celebrated it. 2011, it was at 7 billion. Call it 25 years for 50% growth. Simply continue to feed all these people and you’ll have run-away, exponential growth.

Earth's Population over time, in Billion
Earth’s Population over time, in Billion

Of course, things aren’t as simple as that. First off, the Earth is a closed system and at some point – we are not sure where it would be – there simply won’t be enough food, energy and water. Population would hit a wall and things would turn ugly.

In reality, even if there was no limit to food, energy and water (say because of interstellar imports)  it won’t work out that way.

People adapt to their environment – we’re really good at that. Better health, more wealth, and especially better education also limit fertility. Women simply give birth to fewer children. In the 1950s, it was 5 kids per woman. In the early 2000s, it was half that. The UN expect it to eventually drop to just above 2.05. In other words, a balance will set in, and the best guesses place this at ~9 billion people.

A regular Sunday shopping in Chennai. A good example of the sea of humanity. cc-by-sa, McKay Savage
A regular Sunday shopping in Chennai. A good example of the sea of humanity. cc-by-sa, McKay Savage

In other words, a super-densely populated world isn’t going to happen in any natural way. Population growth is a byproduct of technological progress. If that progress stops, or even reverses, the population becomes unsustainable and will either crash or find an equilibrium. If technological progress continues unabated, then attitudes will change with it and population will find an equilibrium eventually as well, just at a higher level. To put it bluntly, people simply have better things to do with their lives than to raise kids continuously.

Genre Considerations

I am obviously not worried as much about building a realistic population model as I am about creating a setting that fits its genre and is internally consistent and, well, hopefully interesting.

Massively populated worlds are definitely in-genre. Asimov’s Trantor is of course the grand-daddy of them all, and had anything between 40-500 billion inhabitants. Coruscant has a trillion inhabitants. Then there are the many city-worlds of the Warhammer 40k empire (and probably others). Massive, galactic-scale societies support these worlds and absorb their effect on the economy.

In Niven’s “Known Space”, Earth has a population of 18 billion and is described as a crowded hell. Heinlein assumes 11 billion in “The Moon is a Harsh Mistress” and it’s not exactly doing us any good. (Of course in “Starman Jones”, Heinlein assumes that 4 billion people are a lot). In both cases, space travel is fairly limited for various reasons – all those Terrans can’t just mass-emigrate, which limits the effect on other worlds.

The World-Builder’s Solution

My gut reaction was to simply downgrade these worlds – as I did with #2021. However, I reminded myself of the reasons for using a random generator in the first place: It is supposed to spur our imagination, right?

Here’s a map of where those >1 billion people planets are:


The 1.2 in Subsector K is our world #2021, which originally had 786 billion people. Okay, so the absolute numbers are quite too high. But do you notice what I am seeing?

Subsector H, birthplace of the rebellion, has two super-high population planets. Lots of cheap manpower for the war. And that subsectors H-J axis I mentioned? Another super-high population world in subsector J – and the world with the highest tech level in the entire sector! Now, the 834 billion (and 482 billion) are just ridiculously high numbers, but if we fix it like so:


We’ve effectively preserved the random generator results, improved them significantly, and used them to explain the campaign’s political situation.

This brings the population of the sector down to 508 billion people – a fifth of what it was initially.

Next up, we’ll take a look at these planets’ individual UWPs to figure out just how these people might be living.

Quo Vadis, 256?

So. We have a home. Sector 256. This means the work is just beginning – now I need to lay out local space.


The map of local space should be centered on the Imperial Core. That is, by producing this map we imply that “this is it”, similar to how a Terran national map will show, well, the subject of the map plus perhaps parts of some neighbors. Subsectors F and G as well as J and K should thus be the main focus. K is obviously quite sparse – a backwoods area people don’t go to, perhaps comparable to a stretch of desert.

H on the other hand has many worlds that must be quite important – look at all of these A and B class ports and the travel connections between them!

In theory, this could be a neighboring nation but the ideas I have do not allow for a secondary powerful nation. So it’s part of the Empire, and this means I’ll have to expand the map to the “east” a little bit eventually, just to give our protagonists some room to explore.


The Imperial capital world, Mithra, and the original colony worlds the colonists settled on should be close to the center of that region. They do not “have” to be important anymore – just consider the difference between Rome two thousand years ago and now – but they should probably be relatively heavily populated. They should also be fairly close to each other.

Looking at the map, I immediately notice a bunch of temperate worlds which are marked as fairly habitable. (I also notice that habitability index 9 didn’t get shaded, but no matter). These are 1917, 2017, 2118, 2119, 2021, and 2219:

(8)Temperate 1917 X863445-0 Lt NI HI8 25500
(9)Temperate 2017 B8658B9-A Ga Ri HI9 833000000
(7)Temperate 2021 A663BB8-C Hi Ht HI7 786000000000
(8)Temperate 2118 D864951-8 Ga Hi HI8 5770000000
(8)Temperate 2119 C875657-8 Ag Ga NI HI8 4610000
(7)Temperate 2219 A576A85-A Ga Hi In HI7 12200000000

Interesting. #1917 works well for Mithra, just increase the population a little: X863845-0, Pop 156000000. Makes them “Rich” by Traveller definitions and I appreciate the irony. But we’ll get back to that later.

The other three original colonies were Sassandra, Ascalon and Xoth. Let’s use the three garden worlds, #2017, #2118 and #2219, for them. Either the colonists picked worlds most suitable for them, or ones they could easily terraform.

As for #2021, I’m reducing the population code to 9, with 1.19 billion inhabitants.

The Republic

The Republic was founded on Avalon. But where is that? With Mithra in “G”, our logical choices are “H” and “J”. J is probably the better choice – More isolated – but without wanting to foreshadow anything, I really want to place it in H. Let’s assume all those interconnected worlds indicate a tightly-knit community in this province, perhaps they were never too happy about being annexed by Empire in the first place. And Willem II was just the sort of Emperor who would ignore serious problems staring him into the face.

Consulting the map again, I find this:

(2)Hot 2715 A6309C7-D De Hi Ht Na Po HI2 1580000000

A small-ish desert world with high tech, good infrastructure, a very thin atmosphere and a class C government which the Traveller rules book says could be a revolutionary council. Could it be any better?

I can totally imagine these poor bastards, working in the mines under adverse conditions, their living quarters packed due to the high population. Everybody’s poor, and ideas of a Better Future begin to spread.

With the locations of Mithra and Avalon fixed, I’m thinking that the Republic first captured worlds in J, before circling back and attacking the Imperial core worlds from multiple sides. This probably also means that the J-H axis, with travel through the empty space of K, is the main area of Republic control. G is an occupied mess, and F ends up as a region on the sidelines – the Contact Light equivalent of the Regina subsector.

This is what I love about rng’s – they can be so inspirational!


Creating Local Space (2)

Today I decided to put one and one together, so to speak: Apply the theory I build up in the world building posts to the creation of our little nook of local space. Let’s call this our third trial run, that is, I may or may not keep the results.

For subsectors that had a split system probability, I rolled two subsectors each and then “masked” them manually. This was by far easier than to attempt to teach the script which hexes had what probability… However, for the lower-right corner two subsectors I got tired of this and just rolled 4- for the entire subsector. It will do.

Without much fuss, here is the sector map:


Click on it for the full-sized image. I kept my sketch as a translucent overlay.

The sector ended up having 213 worlds, slightly short of the 236 I had estimated. Tech level distribution is heavily stacked towards the low end:


World types are fairly well spread, though I stupidly removed my Se/Sm classes again:

As 4
Ga 54
Fl 53
Wa 7
Va 23
Ht 12
Lt 102
Hi 15
Lo 74
De 11
Ba 10

I’ve made the sector data the sample data for the hacked svg sector map script, if you want to look at or play with the raw data.

As for the results themselves, there are good and bad things.


  • Decent mix of world types
  • Fewer worlds than my draft sector (smaller is better)
  • Highest “regular” tech level is 13 (C), on 9 worlds.


  • The ten high tech worlds are all fairly low population (2×8, 1×9). The 15 High Pop worlds are 9×9, 5xA and 1xB, or between 159 and 1231 billion people, give or take a few. This isn’t necessarily a contradiction; neither China nor India have the highest tech on Earth.


  • The sector almost seems TOO sparse considering it is supposed to host the main interstellar nation in the region – even IF it is a frontier region
  • Distinction between “sparse” and more “dense” star region absolutely not visible based on sheer system presence.

Open questions:

  1. Does the setting work with so few TL10-13 worlds?
  2. Is the sector as-is viable for the sort of setting I have in mind?
  3. Is it, and this may sound silly, aesthetically pleasing?
  4. Is it a “good sector” for adventure?

There are probably more… we’ll see…

Hacked Version of the Subsector Map Script

I don’t really speak Perl and I know nothing about the format of .svg files, but… I’ve created a version of that subsector map script that maps sectors. It doesn’t have a generator yet – sorry, this will have to wait until another day -but I did include some rough sample data.

Anyway, maybe someone finds it useful. And if you want to work on it, be my guest, it’s of course GPL like the original.

Creating Local Space (1)

While I am working on the framework to generate the low-level detail, I can’t help myself but to work on the larger picture – and some actual setting data. Keep in mind that I already created one sector last year; I consider it my “draft”, and it will certainly inform many of the decisions I will be making.

For the first sector, I simply created a small grid of 3×3 sectors with a rough drawing of what I thought local space should look like. (In reality, these should be rectangular.)


I’ve refined this method somewhat. I created the following in The GIMP:


Black are “sparse” or “rift” regions, white are regions of greater star density,

The process to create such an image is fairly simple:

  1. Create a new image. I used landscape, A4 size. But this doesn’t matter.
  2. Filters -> Render -> Clouds -> Plasma.  I used the maximum Turbulence.
  3. Colors -> Desaturate
  4. Colors -> Threshold. Play with the sliders until it looks nice
  5. Filters -> Blur -> Gaussian Blur. I used Blur method “ILR” and radius 30×30, though you may have to change this depending on your image. You want to significantly soften the edges, while keeping the general shapes recognizable.
  6. Create a second layer.
  7. On the second layer: Filter -> Render -> Clouds -> Solid Noise. I used detail 15, x and y size of 16, and both Turbulent and Tilable disabled.
  8. Move this new layer underneath the original layer.
  9. Set the original layer’s mode to “multiply”.
  10. Merge the layer down.
  11. User Colors-> Threshold, play with the sliders again until you get nice distribution.
  12. If you dislike the results, try inverting colors or different random seeds for your plasma clouds.
  13. Don’t be afraid to manually edit the image after step 11 – I did!

Placing our Sector

Note that the image doesn’t have any sort of scale, which gives us some flexibility. I used Inkscape to place the same 3×3 sector grid, and I resized it a few times until I had the “right” fit. I decided on this location:


As is the tradition, X marks the spot – the sector of my setting. I picked this location because there is a lot of “interesting geography” adjacent to it.

Here’s the zoomed section, with subsectors stenciled in as well:


Looking at the map, I think that these are good probabilities:


I estimate a total of 236 systems for this, or just over half the number of systems in my draft sector. If this ends up feeling too sparse, I can obviously shift the probabilities up a bit.

We’ll do that next time.


When I first started working on the science fiction setting, I created several maps covering the Orion Spur and even the Milky Way galaxy. I quickly worked out that these settings were much too big for me to handle, even if I only worked on selected “important” systems.

I was in the process of working out the “correct” size out when Realmwright finally convinced me to watch Firefly – I had been hesitant because I knew that it had been cancelled. I was surprised how much Firefly “felt” like a Traveller game. More importantly, it made me think how important recurring characters and locations are, and I finally decided to bring the setting all the way down to the very small scale of a Traveller sector. (This was, incidentally, when I began using Traveller to model the setting.)

I ended up creating an entire sector, but I did not really think about the process first and found out, later, that it was flawed – one of the key lessons that led me to the creation of Contact Light.

How “big” is a sector really?

Obviously, a Traveller sector consists of 4×4 subsectors, each measuring 8×10 parsecs. But 36×40 parsecs doesn’t actually tell us much about the scale of a setting.

Travel times: Once I had decided on using a Traveller sector for my setting, I worked out that a constant-speed hyperdrive with a velocity of 0.5 parsecs would be ideal. A subsector is 14 hexes across (diagonally), so that means 28 days – four weeks. For comparison, it took Colonial Age settlers four to five weeks to cross the Atlantic ocean.

Number of systems: As it turns out, a Traveller sector is quite a crowded place. The Mongoose basic rules book recommends a 50% system density (and if memory serves me right this has always been more or less standard). Since a subsector has 80 hexes, this means forty worlds per subsector or 640 worlds per sector. That’s a lot. Incidentally, my current Sector contains 424 worlds – some subsectors are more sparse – and that feels overwhelming.

What’s “realistic”?

The stellar density near our solar system is 0.004 stars per cubic lightyear, or about 0.14 stars per cubic parsec. The nearest we can get with one or two dice is a 1-in-6, or  16.67%, chance. This would result in ~ 13 systems for a subsector, or 208 in a sector. (Anecdotal data: The Sol sector in Traveller contains 18 systems.)

What can we do with 2d6?

In reality, I can’t imagine why anybody would want to roll even 80 hexes manually, but let’s still stick to the dice conventions. So what can we actually do with 2d6? This quite easily calculated, too:




Per Subsector

Per Sector

2 or less





3 or less





4 or less


Near Earth



5 or less







6 or less








7 or less








In other words, my sector worked out spot on at the 33% mark, or twice the stellar density near our Earth.

And I frankly can’t imagine what a sector at 58% or higher will look like. Messy, for sure.

What’s “good”?

I don’t think there’s a single number you can cite and say “this is what you should use”, since it’s too intimately tied to other assumptions in your setting.

Looking at these numbers and at my first sector, I have a gut feeling that 27.78% is the sweet spot for what I have in mind. But as we noted, it’s not only the number of systems that matters, but how interesting they are; let’s keep the numbers in mind and revisit them when we’re further along in the world generation system.