Sod it, this draft has been rattling around my noggin long enough, you lot can suffer along with me.

Through force of circumstance, Parental Advisory has mashed up various bits from GURPS Traveller (GT), GURPS Traveller: Interstellar Wars (GTIW) and Mongoose Traveller 2nd ed (MGT2).  Rate I'm going, gubbins from TNE will end up in it as well.  That TNE first landed when I was in year 5 is neither here nor there.

However, this has been the first _deliberate_ mashup, seeing what sort of extreme low-bound facility will be orbiting the rogue gas dwarf Teapot - and seeing if there's any hope of reconciling the starport/station parts of GT and MGT2 before I put more time + effort into it.

Through previous misadventure, the PCs discovered a rogue gas dwarf in Kushuggi 2530 (promptly naming it “Teapot”) in late 2125, and have been making plans to set up the above station as a gateway to Amkarim.

For a first cut, I’ll use GTIW to generate the trade volume, GT: Starports to define the outside-the-hull bits (traffic flow, fuel demand, etc) given said trade volume, and MGT2 + MGT2 High Guard to define the inside-the-hull bits.

GTIW borrowed how it measured trade from GT: Far Trader – using the World Trade Number as an abstraction of a given economy’s size, and the Bilateral Trade Number to abstract how much trade flows along a given route (within an order of magnitude - BTN +1 means x10 trade). Broadly, a given route’s BTN is the sum of the endpoint WTNs, less a penalty for the route’s length.

To spinward-coreward of Teapot is the economic core of the Terran Confederation as at 2127, Terra itself (WTN 6.0). To rimward-trailing of Teapot is an unpopulated region with at least three garden worlds surveyed to some extent during the previous PC misadventure – thus, building Teacup will open a J-2 route through to that region and open it up for Terran colonisation.

Ordinarily, we’d start at step 1 of the GT: Starports build process (GT:SP p58), but that presumes there is something there to support the port – which doesn’t hold for Teacup. Thus steps 1, 2 and the first part of 3 (GT:SP pp58-59) aren’t much help to us.

The Branch Route Table on p133 of GTIW implies the smallest branch route (connecting a WTN 5.5 trade hub world with a WTN 3.0 colony, over at most 2 pc) is BTN 7.0. Ordinarily, Terra’s WTN 6.0 would inflate that to a BTN 7.5 route, but trade route BTNs are capped at double the smaller WTN + 1, so it stays at 7.0. Thus, I’ll design Teacup around that to start with to get a bare minimum station, and neglect the transient traffic for now.

A quick shufti at the “Interpret The Results” table on GT: Far Trader p 16 tells us that a BTN 7.0 route runs 1,000 to 5,000 dton/yr of freight, and from the passenger equivalent on p17, 50-100 passengers per year. In GT: Starports terms, (“Estimated Trade Volume”, GT:SP p59), that means a size 3 port.

I’ll take freight and passenger volumes as the top end of those figures, given Teacup’s location.

Converting those to weekly figures gives 100 dton freight and 2 passengers per week.

Step 4 (GT:SP p60) is easy – Teacup is a single highport, with no downports.

Step 5 (GT:SP p61) starts easy – all the traffic goes to/through the highport.

Tonnage served is likewise fairly simple – 1.5 tons of ship per ton of freight, and 5 tons of ship per passenger works out to 160 dton of shipping per week.

That seems a little low – MGT2 ships, in my experience, tend to have lower cargo fractions than their GT cousins. For a first cut, I’ll double the shipping needed to move a given amount of cargo, then round the result up to the next 200 dton. In Teacup’s case, that’s 400 dton of shipping per week.

“Private” capacity is zero – Teapot is a private port, long predating the rise of the Third Imperium’s Starport Authority.  (I still haven't figured out whether the 2I has been butterflied away, let alone the 3I),

Step 6 (GT:SP p65) is a little rubbery, but I'll do it for the lulz.

As all freight and passengers are transient ($140/dton freight, $460/passenger), annual income is 700 k$ from freight and 46 k$, totalling 746 k$ per annum. Labour force will be left to MGT2.

Shuttle and lighter requirements (GT:SP p63) are zero, as there’s nowhere to go unless by starship.

Step 7 (GT:SP p66) – Teacup will be built at TTL 11, and gains no benefit from exchange rates. As MGT2 charges hulls by volume, and GT charges hulls by surface area, I gave up trying to reconcile the GT-derived budget with the MGT2 kit prices. Basic MGT2 hulls cost 50 k$/dton, while unstreamlined GT hulls start at 10 k$/dton (streamlined hulls at 24 k$/dton) and get cheaper with the cube root of volume as they get bigger.

And we’re pretty much done with the outside-the-hull bits.

Onto the inside-the-hull bits, for which I’ll use MGT2: High Guard (MGT2: HG).

Teacup is forced to use a dispersed structure (penalising hull HP by 10%, and reducing hull cost by 50%), as there isn’t any planetoid big enough in the same parsec. That rules out planetoid and buffered planetoid hulls, and p52 stipulates “Space stations are therefore never streamlined.” - thus, the only remaining choice is dispersed structure.

As the final station volume is unknown, I have to work somewhat in reverse. First, I account for the systems that take up some percentage of total displacement, then use that to gross up the volume of systems that take up some fixed tonnage, to get the total station displacement. For example, if 23% of the station volume is occupied by percentage-volume systems, and 4,800 dton is occupied by fixed-volume systems, thus 77% of the station is 4,800 dton. Total station volume would then be 6,233 dton, rounded up to 6,300 dton.

First is Thrust 0, occupying 0.25% of volume (and 1M$ per ton of drive).

The prohibition on adding extra armour to a dispersed structure station (MGT2: HG p52) can trivially be worked around by building a dispersed-structure ship, adding the armour needed, and then gutting its drives once in place. Thus, 2 points of crystaliron armour occupy 5% of volume (and cost 10% of base hull cost).

I can’t see much point in hull options.

Power generation works out to another percentage-volume system. Basic power needs are 20% of hull tonnage, and M-drive needs are 2.5% of hull tonnage (as per a ship with Thrust 0), for a total of 22.5% of tonnage. Meeting this demand with TL8 fusion power thus takes up 2.25% of tonnage for the actual reactors (at 0.5 M$ per ton), and 0.23% of tonnage for reactor fuel tankage. I’ll add a half-power backup system, taking up 1.13% of tonnage for the reactors and 0.12% of tonnage for tankage.

A SWAG puts the resulting station volume somewhere in the 500-5,000 dton range, so the bridge takes up 20 tons (and 0.1 M$ per 100 tons (or part thereof) of final station).

Two hardened Computer/15 systems cost 6 M$ and take up effectively zero space.

Milspec sensors cost 4.1 M$, and take up 2 dtons.

Teacup’s raison d’etre is fuel supply, with passing traffic demanding 80 dton/wk.

A 1 dton TL10 fuel refinery (p 60) will supply 84 dton/wk and cost 1 M$. 100 dton of fuel tankage to store a little over 8 days’ production will cost 5 M$. For robustness, this all gets doubled, occupying 202 dton and costing 12 M$. 1 crewcritter supervises all this.

A single brig takes up 4 dton and costs 250 k$.

A doubled medical bay takes up 8 dton, 2 power and costs 4 M$. It also needs two medics.

12 dton of workshop space cost 1.8 M$.

Docking facilities sufficient to receive the entire expected weekly traffic (400 dton) take up 1,200 dton, cost 300 M$ and require 12 dedicated crew.

That gives us 1448 dton of fixed-volume systems so far, 8.98% of percentage volume systems so far, and 15 dedicated crew, neglecting luxuries such as general crew. As a result, grossed-up volume would be 1,591 dton, rounded up to 1,600 dton.

As for crew, and following p58, everyone will single bunk (4 dton and 0.5 M$ apiece), with as much again in common space (4 dton and 0.4 M$ apiece), giving a per-crewcritter total of 8 dton and 0.9 M$ so far.

Life support needs will be met by dedicated hydroponic biosphere volume, adding 0.5 dton, 0.1 M$ and 0.5 power per crewcritter. Thus, a crewcritter will require 8.5 dton, 1 M$ and 0.5 power to support them.

That raises the initial grossed-up volume by 127.5 dton to 1,718.5 dton, rounded up to 1,800 dton.

We can start with that minimal grossed-up volume and crew, see what that implies, and repeat until the result doesn’t change too much.

Per p57, initial crew needs work out to:

23 crewcritters’ worth of space boosts the initial grossed-up volume to 1,786.5 dton, which still gets rounded up to 1,800 dton.

Now, the summary:

One question dropped out of this, relating to crew sizes.

Where a crew division complement is specified as 1 per N crew on p57 of MGT2: HG (eg medics as 1 per 120 crew + visitors, officers as 1 per 20 / 10 crew for civil / military stations), to avoid iterating for larger vessels (such as the dammit-we-are-REALLY-bored roughout Eddles and I did of Star Control II's Vindicator - tugboat turned symbol of resistance), would grossing up the crew complement (like I did for station volume) not be too much effort?

For civil stations, out of every 120 crewcritters, 1 is a medic and 6 are officers - so 113 out of 120 crewcritters (94.1%) are neither medics nor officers.

For military stations, out of every 120 crewcritters, 1 is a medic and 12 are officers - so 107 out of 120 crewcritters (89.1%) are neither medics nor officers

Per that roughout, we worked out the top end of Vindicator size (by bounding box) as 111,200 dton, and hooked up J3 and M4 to see what fell out at TTL 12.  That worked out to 8,340 dton of jump drive, 4,448 dton of M-drive and 6,672 dton of fusion powerplant.  (Total power demand worked out at just over 100,000 power points - am I correct in counting a single power point as a megawatt?)

The engineering section had 558 engineers, 56 mechanics and 9 technicians driving the fuel refinery.  The admin section had 56 paper drivers, and I plonked in a 20-crewcritter bridge complement.  699 crewcritters before adding in medics and officers.

That grosses up to 743 crewcritters - 699 already detailed, 7 medics and 38 officers of various stripes and ranks.  Works out to 744 crewcritters total, so it almost gets there in a single pass.

Iterating, by comparison:

Round 0 - 699 other, 0 medics, 0 officers, 699 total

Round 1 - 699 other, 6 medics, 35 officers, 740 total

Round 2 - 699 other, 7 medics, 37 officers, 743 total

Round 3 - 699 other, 7 medics, 38 officers, 744 total.

Round 4 - 699 other, 7 medics, 38 officers, 744 total.

A milspec Vindicator doubles its complement of dedicated mechanics and paper drivers, and wants 1 officer per 10 crew.

Base crew complement becomes 811 crewcritters, and grossed-up complement becomes 910 crewcritters.  811 already detailed, 8 medics and 91 officers of various stripes and ranks - 910 crewcritters total.

Iterating, by comparison:

Round 0 - 811 other, 0 medics, 0 officers, 811 total

Round 1 - 811 other, 7 medics, 82 officers, 900 total

Round 2 - 811 other, 8 medics, 90 officers, 909 total

Round 3 - 811 other, 8 medics, 91 officers, 910 total.

Round 4 - 811 other, 8 medics, 91 officers, 910 total.

Time to laugh,

Alex