GURPS Spaceships for THS conversions?

[thtraveller]

Originally Posted by thrakkemarn

Thanks for the link, I never realized it was updated!

I hadn't realized it needed updating until you mentioned it.

Hmm, I like this idea a lot. Just so I'm clear, you take a 1-point power system and it provides .5 power so can power .5 of a weapons battery, OR you use a 2-point power system and use 1/3 of it (to get 2/3 power point) and it powers 2/3 of a weapon battery?

Yes

The price doesn't seem to make sense the way you did it though ... a 15 weapon battery using a fuel cell should be cheaper than a 20 weapon battery using an MHD. I would simply multiply the cost for each system by the % of it you are using (I rounded any fractions up to represent the cost of integration):

Self powered Tertiary Battery (Fuel Cell) [Hull]
15 weapons per battery
Cost SM7+ $: 0.85M 3.5M 8.5M 35M etc
Uninstalled: 1 3 10 30 etc

Self powered Tertiary Battery (MHD) [Hull]
20 weapons per battery
Cost SM7+ $: 1.1M 4.5M 11M 45M etc
Uninstalled: 0.75 2.5 7.5 25 etc

Yup, those numbers look right. However, Spaceships module prices are typically only shown to one significant figure, and occasionally two when the second sig fig is a 5. And even then only every other SM has two sig figs. Also the battery prices were chosen so that the price for each weapon in the battery was a nice number of one or two sig figs.

So when calculating new numbers off original module prices that are severely rounded you don't need to be too precise; and you need to consider divisibility; and you need to try and maintain roughly a 1:3 ratio between SMs. However I agree that 20 weapons should be dearer than 15.

My original prices don't pass all those tests either, so I suggest
- fuel cell 750K 3M 7.5 30
- MHD 1 4 10 40

[thtraveller]

Re the alternative Sunlance drive performances

TL9
-one fusion pulse drive plus fifteen tanks = 35 days to Mars (HT = 59 days)
-six advanced fusion pulse drives plus ten tanks = 23 days to Mars (HT = 42 days)
-six fusion rocket (Hydrogen) drives plus ten tanks = 29 days to Mars (HT = 48 days)

TL10
-one fusion pulse drive plus fifteen tanks = 20 days to Mars (HT = 30 days)
-six advanced fusion pulse drives plus four tanks (it hasn't got time to burn any more) = 22 days to Mars
-six high thrust advanced fusion pulse drives plus eight tanks (it hasn't got time to burn any more) = 16 days to Mars
-six fusion rocket (Hydrogen) drives plus five tanks = 22 days to Mars
-six fusion rocket (Water) drives plus ten tanks = 17 days to Mars
-six HT fusion rocket (Hydrogen) drives plus ten tanks = 16 days to Mars

HT drives are slower unless you can do a continuous burn all the way.
Advanced fusion pulse is the most economical of the fusion pulse drives
Fusion rockets, particularly water, are by far the cheapest to run using default Spaceships costs.

[thrakkemarn]

Just out of curiousity has anyone tried to make an economically viable tramp freighter for TS using Spaceships 2 rules? It seems to work if you use TS fuel costs, use the TL9 price scheme for freight and passengers, and allow TL10 fusion pulse drives.

[thtraveller]

Originally Posted by thrakkemarn

Just out of curiousity has anyone tried to make an economically viable tramp freighter for TS using Spaceships 2 rules?

I tried back when it came out and it only came close to realistic with the suggested costs from S2 with optimally designed Fusion Rocket craft. Though it was a poor fit to the designs in S2.

It seems to work if you use TS fuel costs, use the TL9 price scheme for freight and passengers, and allow TL10 fusion pulse drives.

TS has NP fuel 100 times cheaper than Spaceships at $500 per ton.

Plugging in your drive and numbers into an efficient spacecraft and working out "realistic" economics gives $20K per cabin (first class passenger) and $2K per ton of cargo for a median Earth-Mars trip (1.8 AU). So about $11K per cabin per AU, $1.1K per ton cargo per AU. Which, as you say, is very close to the S2 suggested costs for TL9.

Design:TL10, SM10, spin gravity, Armor, Control, 5 Habitat (300 cabins), 3 cargo (1500 tons), 9 tanks, 1 Fusion Pulse Drive (0.05G, 126 mps), $203M, Earth-Mars 34 days, 10 trips per year.

Economics include fuel cost, ship payments, depreciation, insurance, salaries and a 5% RoI

[thrakkemarn]

I did it as 6k/cabin, 12k/ luxury cabin. A cabin can take 2 economy or 1 first class passenger, a luxury cabin can take 2 first class or 1 luxury passenger (I'm using the S2 terms). And 1k/freight, like you said. (This also correlates with the costs in the TS 3e book and changing times).