Thursday, February 7, 2019

Robots as Spaceships: Between SM's

Spaceships categorizes craft by their SM, which is a tool that appears in GURPS again and again because its so useful. However, when we get to human-scale objects, we find that each SM cover a huge range. This is just fine for calculating hit penalties and mana costs, but it falls short as the sole number determining something's size. We need a more fine grained system for determining spaceship sizes.

As it turns out, I already built one, when working with sea monster sizes. We want to go smaller than the monster table, and its nice to have the ST built into it (we're using a very different method for determining ST), so we have an adjusted version. We've also added a base cost to each of these size entries, so that we can use relative and base costs easily.

WeightSMStrengthBase CostWeightSMStrengthBase Cost
5 oz-5ST 2$.015100 lbs+0ST 17$5
8 oz-5ST 2$.025150 lbs+0ST 19$7.50
12 oz-5ST 3$.035200 lbs+0ST 20$10
1 lb-4ST 4$.05300 lbs+1ST 23$15
1.5 lbs-4ST 5$0.075500 lbs+1ST 27$20
2 lbs-4ST 5$0.10700 lbs+1ST 30$30
3 lbs-3ST 6$0.151000 lbs+2ST 36$50
5 lbs-3ST 7$0.251500 lbs+2ST 45$75
7 lbs-3ST 7$0.352000 lbs+2ST 50$100
10 lbs-2ST 8$0.501.5 tons+3ST 56$150
15 lbs-2ST 9$0.752.5 tons+3ST 65$250
20 lbs-2ST 10$1.003.5 tons+3ST 70$350
30 lbs-1ST 11$1.505 tons+4ST 79$500
50 lbs-1ST 14 $2.507.5 tons+4ST 92$750
70 lbs-1ST 15 $3.5010 tons+4ST 100$1,000

We'll refer to each of these vehicle sizes by their weight, and generally throw a motive type in the description as well. So our Gunbot is a 200 lb tracked robot.

This set of weights is still pretty rough-grained, but for any weight we choose, there will be a stat line within 20% of it. This happened because we used the size/range table for weights rather than lengths. This spread of numbers works well with Gurps, and has a lot of support.

We can now build a wide variety of robots at these sizes. Of particular interest is the 100 lb to 1000 lb range: there is a big difference between walker that weighs 300 lbs with the human onboard and one that weighs 500 or 700 lbs. Many fictional androids will be made at the 100 lb or smaller mark, and are correspondingly cheaper.

Lets get out there and build all of the robots we can think of! At least in our games. I take no responsibility for any actual robot legions of doom.

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