T20 star system/world generation rules

[jgreely]

Okay, I've read Slink182's post on the troubles he ran into automating the system for Windows, but while I did have the same "too darn many asteroid-belt mainworlds" problem, I have enough other questions about the system as presented to justify a new topic.

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• In step 3, when a red dwarf is generated, it says "you may skip step 4". Setting aside the fact that this is a must not a may, should you also ignore step 4's temperature modifier for class M? I'm guessing yes, based on the white dwarf example above it.</font>
• In step 4, does the comment on "no K5-K9 sub-giant stars" mean "size IV" or "anything smaller than a giant"? I assumed "size IV", on the theory that they'd have written non-giant otherwise.</font>
• In step 7, why does the first row of the habitable zone table exist, when by step 3 all white dwarfs are class W with no habitable zone?</font>
• Is it correct that there is exactly one habitable orbit (0) for a red dwarf? Other discussion suggests yes.</font>
• Still in step 7, when placing companion stars, they are "occasionally" found in the main orbits. I decided this meant "roll 3 or less on 2d6" (~8%).</font>
• By the way, if you place companion stars in orbits this way, there's a one-in-several-million chance that the "forced empty" rule will eliminate all other orbits in a trinary system, leaving you no place for a mainworld. I liked this so much I blessed it with size code Z in the UWP. </font>

In the world generation rules, the only thing that really caught my eye was that the population multiplier in step 8 is called an "exponent" (when the actual exponent is the UWP Pop code). And there are a few places where the rules can produce out-of-range results, like Hydro and TL (I was really surprised to find a TL 19 world in my output; "woo-hoo, anagathic supply run!").

My way of dealing with the "way too many orbit 0 asteroid belts around red dwarfs" was to add an additional roll of 1d3. On a 1, the mainworld is placed in orbit 0, otherwise it ends up in a random outer-zone orbit. I've also added the suggested "ignore size mods for close orbits" option, which increases the variety and makes the output look more Traveller-y.

The other major problem I found was a number of low-tech asteroid-belt mainworlds with thousands of people and no starport. To fix that, I added code so that if a belt mainworld had a TL below 8, then it should be rerolled based on population. For Pop 0-2, roll 1d3 + 6 + Pop, else 1d3 + 9.

This leaves you with a small chance of a Pop 0, TL 7 belt, which I decided represented a colony ship that broke down several generations ago, stranding a small (and steadily decreasing) number of people here. The survey Scout ship either didn't have room to evacuate them, or couldn't convince them to leave (no common language, etc).

-j

 

[Malenfant]

Originally posted by J Greely:
[*]In step 3, when a red dwarf is generated, it says "you may skip step 4". Setting aside the fact that this is a must not a may, should you also ignore step 4's temperature modifier for class M? I'm guessing yes, based on the white dwarf example above it.

It means that if you make a red dwarf it is automatically an M V star. So change the 'may' to 'must'

. Also note that the lifespan should be up to trillions of years, not hundreds of millions.

The temperature modifier makes no sense as implemented in T20 anyway, but this part is even more nonsensical. Red Dwarfs in step 3 are supposed to have a temp modifier of +1, main sequence stars have a modifier of +0, but M stars have a +2 modifier in step 4. So an M V star (which is what a red dwarf is) should therefore have a total modifier of +2 (+2 for M, +0 for V), not +1.

Then again, M Giants have a total modifier of +1, which means that apparently they're more likely to have colder worlds for some odd reason.

[*]In step 4, does the comment on "no K5-K9 sub-giant stars" mean "size IV" or "anything smaller than a giant"? I assumed "size IV", on the theory that they'd have written non-giant otherwise.

"Subgiant" is a name specifically used for Size IV stars - it never means "anything less than a giant".

Note also that the text is wrong - it should say that there are no K5 to M9 IV stars.

(then again if you want a more realistic stellar generation, you should use the Revised Stellar Generation Tables that I came up with here and that can be found on my website ).

[*]In step 7, why does the first row of the habitable zone table exist, when by step 3 all white dwarfs are class W with no habitable zone?

It's an error. WDs don't have habitable zones.

[*]Is it correct that there is exactly one habitable orbit (0) for a red dwarf? Other discussion suggests yes.

Technically, Orbit 0 is the only habitable zone possible for red dwarfs, and even then only the ones around M0 V would have them, and even then any world in the habitable zone is automatically tidelocked.

[*]Still in step 7, when placing companion stars, they are "occasionally" found in the main orbits. I decided this meant "roll 3 or less on 2d6" (~8%).

Again, you can use the Revised Stellar Generation Tables here.

[*]By the way, if you place companion stars in orbits this way, there's a one-in-several-million chance that the "forced empty" rule will eliminate all other orbits in a trinary system, leaving you no place for a mainworld. I liked this so much I blessed it with size code Z in the UWP.

So what is the UWP actually describing there, if there's no planets?

In the world generation rules, the only thing that really caught my eye was that the population multiplier in step 8 is called an "exponent" (when the actual exponent is the UWP Pop code).

Yes, you're right. Any mention of "exponent" in the Population Exponent section should be replaced by "multiplier".

And there are a few places where the rules can produce out-of-range results, like Hydro and TL (I was really surprised to find a TL 19 world in my output; "woo-hoo, anagathic supply run!").

Yes. You can get some very silly results here. And there's no reason whatsoever that the highest technology will be found on tiny vacuum worlds with tens of billions of people on them and a feudal technocracy gov.

My way of dealing with the "way too many orbit 0 asteroid belts around red dwarfs" was to add an additional roll of 1d3. On a 1, the mainworld is placed in orbit 0, otherwise it ends up in a random outer-zone orbit. I've also added the suggested "ignore size mods for close orbits" option, which increases the variety and makes the output look more Traveller-y.

Considering that the size mods for close orbits were in CT Book 6, I'm not sure how removing them would make it "more Traveller-y" .

It does seem rather broken though, the size modifier for orbits 0 and 1 are rather extreme. Maybe replace them with -3 and -2 respectively (and have orbit 2 as -1)?

The other major problem I found was a number of low-tech asteroid-belt mainworlds with thousands of people and no starport.

How'd you end up with a bias toward that?


I must say, T20 doesn't really do anything to fix CT's worldgen system - in fact, it makes it worse in several regards... I think GT:First In is still by far the best system out there.

 

[Malenfant]

Oh yeah, and the year length table on page 374 is also wrong. The multipliers there are only true if the planet is orbiting a G2 V star (ie the sun or a star with the same mass).

You need to apply an extra multiplier on top of the one shown to account for the star's mass - if the star has 0.25 of the mass of the sun, the extra year multiplier is x2. If the star has 4 times the mass of the sun, the extra year multiplier is x0.5.

In other words, the extra "mass multipler" is:

x (1 / (square root of the ratio of the star's mass to the sun's mass))

Of course, T20 doesn't give you the stellar masses anyway, so this is all kinda redundant. But generally the orbital period (and rotational period, since it's tidelocked) of a planet in orbit 0 around a red dwarf (taking into account the mass and the orbital distance) is going to be 0.179 years.

 

[Flynn]

My personal resolution to this issue is to skip the solar generation at first, and not take that into account in generating world size.

After the base UWP is generated, I use Malenfant's stellar generation method, to create stars because it may as well see some use after all the effort required to code it.

Since Malenfant's method requires physical and population data on the world first, you have to use it out of T20 order. May as well just stick it in after the Tech Level is generated.

Enjoy,
Flynn

 

[Malenfant]

BTW, I was assuming you had the first printing of T20.

You can find the latest errata here, but the world design section on page 8/9 doesn't address many of the points raised here.

 

[jgreely]

Thanks for the clarifications (and yes, I have the second printing of the T20 book). I've bookmarked all the popular variant generation systems, but I was specifically trying to implement the T20 rules with minimal modifications, to seed my sector-to-PDF script. I plan to do visual comparisons between the different systems to see which one generates the most interesting and/or "similar to official printed maps" (what I meant by Traveller-y) results, and then mix and match until I get something I like for MTU.

Originally posted by Malenfant:
So what is the UWP actually describing there, if there's no planets?

I figured it was so unusual that the survey team just had to find a way to write it up. Maybe they found a large rock and wrote "Kilroy was here" on it.

</font><blockquote>quote:</font><hr />The other major problem I found was a number of low-tech asteroid-belt mainworlds with thousands of people and no starport.

How'd you end up with a bias toward that?</font>[/QUOTE]By the book, it's not unusual. In step 9, you roll 2d6, +3 for Pop 3, and on a 12 you have no starport. Then in step 12, roll 1d6, -4 for no starport, +2 for size 0, +1 for atmosphere 0, +1 for population 3, and you get a TL range of 1 - 6. A class E starport (10-11 on the roll) gives you a TL range of 5-10, still pretty fishy.

-j

 

[Malenfant]

I'm not entirely sure why having no starport means your TL is greatly reduced.

Then again it seems a bit goofy as it is - technically our modern Earth culture should grind to a halt soon in Traveller, since we don't have a starport (-4 TL) and we have a pop digit of 9 (+2 TL), the maximum TL we can have is TL 8.

So does that mean we can't improve our TL in Traveller unless we hit a population of 10 billion?!

Then again, if we clear a patch of ground for ships to land on, apparently our TL can improve to 12 because the -4 modifier is removed.

Sounds a bit wacky to me...

 

[hunter]

Moden Terra does have a starport. More than one in fact. I'd rate them a very-low quality class B installations at best, most more likely qualifying as class C.



Hunter

 

[Malenfant]

I dunno, it's not like Cape Canaveral can fix grav vehicles or jump capable ships... I'd call that a C if you're feeling really generous, and a D if you're more realistic .

But I guess you could call it a starport, of a sort.

 

[hunter]

Class B must be capable of repairs, providing refined fuel, and be capable of building non-starships.

Canaveral and other sites on modern Earth fit this bill, albeit very crudely at this point.

At any rate, there are starports on Earth so you can lose that -4 TL penalty!

Hunter

 

[Malenfant]

It's kinda hard to have "no starport" really, given that E is "a bare patch of ground to land on". Even an uninhabited planet has that!

I gather that X (no starport) is only ever used to denote that travel to that world is actually forbidden. Though I still can't see why that means the world has to have a -4 to its TL.

 

[BrennanHawkwood]

Originally posted by Malenfant:
It's kinda hard to have "no starport" really, given that E is "a bare patch of ground to land on". Even an uninhabited planet has that!

Yeah...IMTU I usually explain it away as the official code assigned by the appropriate governmental agency as opposed to an absolute rating of starport availability. Admittably, this approach has holes big enough to drive a semi through, but given that MTU is currently set completely within Imperium (i.e. one 'consistent' agency providing the ratings) and my players aren't particularly into analyzing the way the system works I'm able to avoid needing to come up with a better way of handling it.

Originally posted by Malenfant:

I gather that X (no starport) is only ever used to denote that travel to that world is actually forbidden. Though I still can't see why that means the world has to have a -4 to its TL.

The best explanation I've heard is that the starport level could also be seen as a loose indicator of the level of contact the world has with other worlds. In the case of an X class starport the tech level would be lower due to a lack of idea sharing and access to others experience. It's not a particularly good explanation, but it is the only one I can recall.

 

[jgreely]

Originally posted by Malenfant:
It's kinda hard to have "no starport" really, given that E is "a bare patch of ground to land on". Even an uninhabited planet has that!

Ah, but it's a surveyed bare patch of ground. Solar systems are extremely large, and if you don't have co-ordinates, you might spend months wandering around in a system looking for a flat place to land (years, if it's just an asteroid belt and a few gas giants). X would then mean that the survey team either didn't find one, or didn't bother to look because the place was so dull.

In the case of a well-populated belt system with no starport, it means that the population is constantly migrating around the system, and their navigation beacons are incompatible with Imperial sensors.

-j

 

[Malenfant]

Originally posted by J Greely:
Ah, but it's a surveyed bare patch of ground. Solar systems are extremely large, and if you don't have co-ordinates, you might spend months wandering around in a system looking for a flat place to land (years, if it's just an asteroid belt and a few gas giants). X would then mean that the survey team either didn't find one, or didn't bother to look because the place was so dull.

How hard can it be?!
You could find a flat enough place to land anywhere, you don't need to do a survey to find one.

 

[jgreely]

Originally posted by Malenfant:
How hard can it be?!
You could find a flat enough place to land anywhere, you don't need to do a survey to find one.

When an ordinary starship jumps into a system, it arrives about 100 diameters from the mainworld. If the mainworld is an asteroid belt, obviously that means "near the starport if there is one".

When a survey ship jumps to a previously unexplored system, on the other hand, where does it arrive, and how long does the team hang around looking for the details of the UWP and PBG? If there are natives, do they just ask them for the data and record it, or do they double-check, and if so, how thoroughly? If they can't communicate with natives, how much time do they put into gathering accurate data for the UWP and PBG?

And is there canon on this anywhere, by the way?

So with those questions in mind, I think X is the place that the initial survey ship appeared when it jumped into the system. If the team came across a nice flat place to land a ship that didn't have obvious hazards nearby, they recorded its location as a Class E starport. If they couldn't find one on the designated mainworld (due to earthquakes, nasty critters, dust clouds, radiation, electromagnetic interference, volcanos, hostile natives, etc, etc) before they were ready to move on, they kept the X.

So, yeah, you can probably find a safe place to land in a system with no starport, but you're going to have to cruise around looking for it (how good are your ship's sensors?), and space is big. It could take a while.

-j

 

[Malenfant]

Depends what you define as "canon" about surveying methods - there was the info in the DGP World Builders Handbook (which is now "forbidden canon", but that doesn't somehow magically render it unusable), and GURPS Traveller: First In went into great detail about surveying worlds and IISS' first contact protocol.

Space may be big, but planets aren't. You can arrive there in your Donosev, launch some orbital mapping and survey probes, and you can probably have the planet mapped down to the metre scale in all manner of wavelengths from orbit in anything from a couple of days to a week. It doesn't take that long to figure out the physical UWP either.

Traveller spacecraft are also much easier to land on planets than aircraft, since the former don't need a runway. Considering that any large patch of grassland or desert would suffice as a landing field, it would be ridiculously easy to find a landing spot even with a cursory survey. Heck, you could easily find one just by flying over the planet for a few hours.

 

[jgreely]

I gather GT doesn't use UWP or A-X starports, so while it may be useful for describing survey missions, it likely won't solve UWP-specific problems. I might pick up a copy of First In at some point, though, since it seems to be a well-recommended book.

And your answer indirectly reinforces my argument for what X means. Yes, the survey team could have spent a few weeks selecting the best mainworld/belt and surveying it with a bunch of probes, and in most cases this would be sufficient to establish at least a Class E. So an X means there's some reason they wouldn't or couldn't designate a safe landing place.

What was their reason? Make one up if you're running an adventure there, otherwise it's not important. Maybe the natives ate their dog.

-j

 

[Malenfant]

Originally posted by J Greely:
[QB] I gather GT doesn't use UWP or A-X starports, so while it may be useful for describing survey missions, it likely won't solve UWP-specific problems. I might pick up a copy of First In at some point, though, since it seems to be a well-recommended book.

It can easily be tweaked to make UWPs or A-X starports. It's just a case of interpreting the results of the worldgen system (also in First In) appropriately.

And your answer indirectly reinforces my argument for what X means. Yes, the survey team could have spent a few weeks selecting the best mainworld/belt and surveying it with a bunch of probes, and in most cases this would be sufficient to establish at least a Class E.

Thing is, there isn't as single reason to assume that a planet doesn't have a flat piece of land on its surface somewhere (unless of course it's a 100% waterworld, but even then, many ships can land on water). So to say that there isn't even that there is going to be somewhat misleading.

So an X means there's some reason they wouldn't or couldn't designate a safe landing place.

Well, that's why I think it means "travel to this world is forbidden", because you will always find a flat bit of land on a planetary surface. So there must be something else there that means that you can't land.

 

[jgreely]

Originally posted by Malenfant:
Thing is, there isn't as single reason to assume that a planet doesn't have a flat piece of land on its surface somewhere (unless of course it's a 100% waterworld, but even then, many ships can land on water). So to say that there isn't even that there is going to be somewhat misleading.

Fortunately I didn't suggest any such thing. There's a difference between "no such place exists" and "the survey team didn't designate a single standard/required place for visitors to land". Actually, I'll modify my earlier statement and say that X could also mean "just park it anywhere, aliens; it's not like we're going to care" as well as "we're a billion rabid xenophobes who'll try our best to kill you".

that's why I think it means "travel to this world is forbidden"

In my mind, forbidden to the point of being part of the survey data is a Red Zone, so how would you feel about "unwise" or "strongly discouraged"?

-j

 

[Malenfant]

Originally posted by J Greely:
</font><blockquote>quote:</font><hr />Originally posted by Malenfant:
[qb]So to say that there isn't even that there is going to be somewhat misleading.

Fortunately I didn't suggest any such thing. </font>[/QUOTE]I didn't mean to say that you said that - I meant that IISS would say that to travellers.

Actually, I'll modify my earlier statement and say that X could also mean "just park it anywhere, aliens; it's not like we're going to care" as well as "we're a billion rabid xenophobes who'll try our best to kill you".

That makes the "X" classification fairly useless then. There would be no functional difference between "E" (bare patch of rock to land on) and "X" (no starport). Though that is basically the case now - hence the confusion. Gotta love Traveller and all it's ambiguities!

Still, I'm fairly sure that MWM has actually said that X starports meant specifically "don't go here", and that E starports meant "it's OK to land here, but you're gonna just have to find a big enough patch of ground to park on". I'm sure it was in relation to one of the online Core Route projects but I can't find the link right now .

Aha! I found it!:

Marc Miller: All worlds are generated normally, but Pop is automatically set at 0 (and so on). The "Zone of Barren Worlds" does not refer to only zho, it means there is no intelligent life on most of them, thus ENNN000-0. I use E (hard bedrock and little else for a spaceport) rather than X which doesn't mean "no spaceport" but instead "no one allowed in (by some interdicting authority)."

Clifford Linehan: So all planets in the barren zone have starport E unless there is something special about it that the authorities don't want you there.

So if you consider anything MWM says anywhere to be canon, there you go.

In my mind, forbidden to the point of being part of the survey data is a Red Zone, so how would you feel about "unwise" or "strongly discouraged"?

Yes, it's funny how many Red Zones have starport X isn't it . "Strongly Discouraged" would be an Amber Zone.