Sorry, I see a bit of confusion on my part: 

To me 'available' pads for the Starport meant 'present and available for immediate occupation'. What I think the fist full of dice tells you is pads that are *available* in the 'they exist' sense of available rather than saying they are free (or that other formula for how long you might have to wait would never be applied). 

If the fistful of dice is really 'existent' pads (many or all of which may be full as depending on the other roll for how long you have to wait to get one), then my comments are already effectively part of the mechanic for delays (which is to day, a Port A could take a while to get into despite having a fair number of pads). 

Thanks for the UWTN/WTN clarification. I had a feeling trom some work that Thomas Jones-Low had done that I looked at meant that Starport is part of the final WTN and thus if you tried to determine the Starport type using the WTN, you'd end up with a recursion. I suppose what I would really use is the UWTN and use that to help determine the starport and then go on to use the UWTN + the Starport mode to get the WTN. 

Tom

On Tue, Sep 29, 2020 at 7:57 PM Thomas RUX <xxxxxx@comcast.net> wrote:
Hello again kaladorn,
On 09/29/2020 12:54 PM xxxxxx@gmail.com wrote:

That's interesting (the rolling a handful of D6s for larger ports) in its own right.
The number of dice rolled is calculated for all sizes of ports. Class A ports have the most dice to roll while Class E/H have the least dice to throw. The Berthing DM increases the number of berths a Class A has by Number of Dice x 1, Class B/C/F do not get additional berths, and Class D/E/G/H decreases the number of berths by Number of dice x -1.
You'd think many A type ports, despite having larger berthing, may well have larger traffic patterns (and if there is a lot of shipping going on, even an A type might have you join a queue for some hours (that other product we discussed had that perspective).
Traffic was discussed in the original The Compleat Star Port thread because of an issue with the Starport Contents Table Traffic DM for the Class A port.
So, having 11D of 0-modified dice should average to about 38-39 available pads. But does that mean you can fly to them without a long traffic/customs delay? Maybe not.
The only way to get 11D is by having the Class A calculation be P +1 versus P -0 which would be 10D. A Class A Berthing DM is +1 per dice which with 11D would increase the number of berths by 11. For Class B/C/F ports the DM is 0, and Class D/E/G/H the DM is -1. I do not know if that changes the average number of available berths/pads.

"Traffic at a given starport is found by making a 2D6 roll applying the modifier given for the port type in question, and multiplying the result by 10. The result is the percentage of the berths at the port (from 0% to 150%) currently filled by available traffic. The actual number of ships in the port  at the time of rolling (check when first arriving in orbit, and once again each week) is taken as a percentage of available bays. It is up to the referee to determine the sizes and natures of the ships in port as and when the characters need to know. Thus the traffic figure can help establish not only whether there is room for an incoming ship to dock, but also how many ships are currently in port when the characters are seeking passage off-planet."

The Traffic DM for a Class A port is +4. Rolling the 2D6 the result is 11 + 4 = 15 x 10 = 150%. If the port has 38 berths/pads x 150% indicates that there are 57 ships in port and with 39 there are 58.5 or 59 ships in port. There 19 to 21 ships waiting for a berth/pad.

"Waiting time: Results over 100% represents ships already in orbit and on a waiting list to land at the port in question. If joining in a waiting list, roll 2D6-2 and multiply by the percentage. Divide by to rounding fractions up, to get the number of hours (from 0 to 150) before there is a berth available. The ship must either remaining in orbit or find an alternate starport until a landing bay opens up."

If I have this correct rolling a 12 on the 2D6-2 results in a 10 time 150, not a percentage, equals 1,500 divide 10 means the wait time is 150 hours.
Anyway, you can fix it however you prefer. Maybe one of the authors could be located and asked but the point is small enough that you can just decide and likely nobody will quibble.

The challenge, one supposes, in designing sectors, is that populations would gradually develop (or reduce) and trade would be tied to that (to service the masses and flee dying areas where populations are crashing) and starports would follow trade (the more trade, the more port upgrades you need). To do this sort of modelling is a big project.
MgT 1e The Third Imperium Starports I feel covers this since you can upgrade the ports by adding components/modules when the population and/or trade increase. When the population and/or trade decreases the port goes into decline with sections not in use or sections removed and sent to a new location.

But if one used Gurps WTNs (assuming they don't require a Starport as part of WTN calculation in which case you'd have a recursion) to determine overall sector trade flows, you could also let that process largely drive port quality and sizes throughout your sector.
I did start going through GT Far Trader but like other projects I was side tracked. However, checking the book pp. 13-14

WORLD TRADE NUMBER (WTN)
The world trade number rates both size of a world’s economy and its tendency to engage in interstellar trade. It is determined in three steps.

1: Determine Unmodified World Trade Number (UWTN)

UWTN measures the size of a world’s economy. It is dictated by the size of the world’s workforce (depends on the world’s population) and the productivity of that workforce (depends on the world’s TL), as follows: UWTN = TL Modifier + Population Modifier.

TL Modifier Table
Population Modifier Table

2: Determine Port Modifier

Port modifier measures a world’s propensity to trade, and is determined in part by the world’s starport class. A good starport increases trade by making the world a more attractive
stopover for merchant ships. More important, it reflects the world’s desire for off-world contact.

Port modifier also depends on the size of the planetary economy. Planets with large and prosperous economies can better afford to invest in starport facilities, which makes it all the more unusual when they do not. For example, Forine – at 1.6 billion people and TL9 – has the second-largest economy in District 268, but only a Class II starport. The fact that Forine’s starport cannot even perform minor repairs on starships, despite the world’s size and affluence, indicates its indifference or even hostility to off-world trade.

Port Modifier Table

3: Determine World Trade Number
World trade number (WTN) is given by:
WTN = UWTN + Port Modifier.

Tom Rux

-----
The Traveller Mailing List
Archives at http://archives.simplelists.com/tml
Report problems to xxxxxx@simplelists.com
To unsubscribe from this list please go to
http://www.simplelists.com/confirm.php?u=RDHE7iRpfwqlHvVvWBIhpJZsbTiD5NnL