Spaceship Tech in your Setting

[Greg 1]

The GURPS Spaceships design system offers various alternatives for what is technologically possible, even at a given tech level. Most obviously, decisions have to be made about how spaceships travel faster than light, and what weapons can exist.

What choices did you make (or would you make) regarding what technology is used for spaceships?

Have you tried converting ships other people have made that use different technology? How hard was it?

On a related note, does anyone know of any online GURPS Spaceships collections?

[Rupert]

I use Spaceships to design spaceships for my Traveller game (that use GURPS 4e). I have some house rules for the jump drives and a few other things, and use quite a few optional rules as well, especially when converting ships from Traveller that aren't easy fits into Spaceships.

Jump drives use the stats for 'Stardrive' engines, with the following changes:
Cost = base cost x [jump Number/2 + 0.5]
Power requirement: Jump number for two 10-minute turns, or 2 x jump number for one 10-minute turn
'Fuel' requirement: one system of liquid hydrogen per jump number.

The latter is much lower than is traditional in Traveller. However, Traveller uses volume, not mass and the conversion is closer to what I use than one might expect. More importantly, this amount gives about the right amount of mass left over for other systems, as Spaceships demands more mass for controls and armour than Traveller design systems usually do. TL9 allows jump 1 & 2, TL10 3 & 4, and TL11 5 & 6.

Contragravity is available from TL9. Reactionless thrusters are also available from TL9, but at TL9 only 'hot' thrusters are available and they have half normal acceleration (i.e. 0.5G per system). At TL10 and TL11 cold and hot thrusters are available.

Ghost Particle weapons a Traveller's 'Meson Guns', and are available at TL10, but do damage and have range as if they have 1/10th the power output. Heat Ray, Antiparticle, and Graviton weapons don't exist.

Force Screens are all automatically Reality-Stabilised, and only affect attacks that require that to affect them (which effectively means they only work vs Meson Guns, and are thus 'Meson Screens' unless Grandfather shows up with some exotic weapon and starts annihilating everyone). Nuclear Dampers are small and cheap enough that any combat vessel of 1000 tons mass or more can be assumed to have one 'for free'.

There's probably other stuff I've forgotten, and there are a bunch of campaign switches, etc. as well.

[khorboth]

I feel like this question is backwards.

Start with the feeling and themes of the setting and then decide what kinds of spaceships exist there.

In my supersoldiers game, I wanted both good FTL travel and a good reason for people to go into stasis during it. So, I created an FTL drive where objective (outside the ship) travel speed was measured in hundreds of times the speed of light. Then, I had subjective (inside the ship) travel speed stuck at speed-of-light. So, a 10-light-year trip might take hours of objective time, but would be four years of subjective time. I then just refused to explain how the physics worked. Nobody fully understood the physics in-universe. It wasn't important to the game. I also wanted a reason to have some in-system travel time, so ships had to jump in substantially far from stars due to radiation levels interfering with the drive. In-system, I made excessively efficient drives which used mass scooped from gas giants. The PCs had a very nice ship which could accelerate at 2g for as long as they needed to. I gave them travel times based on their characters' calculations. Again, further explanation was unnecessary. It wasn't the game's focus. I described the game as hard-science compatible. It mostly made sense, but wasn't excessively detailed.

Conversely, when we ran Star Wars, the ships had top-speed. They had a certain range before refueling. When they went close to other ships, they went "woosh" explosions in space go "boom!" And we translated entries from Wookiepedia as best we could. Sense and physics be damned. Because it wasn't that kind of game.

Edit:
My math is wrong/inconsistent. And as I remember more, I think I had days between systems rather than hours. Drives were between 500C and 3,000C

[David Johnston2]

The last time I took a run at it I postulated two different kinds of jump drive. The first is jump gates, where artificial gates have been built to allow civilian commerce without an internal FTL drive. Because circumference is limited the large commercial vessels are modular cylinders that link up so two engines, one front and one back can slowly move engineless modules like a train.

Meanwhile the other kind of jump drive is primarily for military and exploration vessel and requires a close flyby of a sun to jump, meaning it can only be used on armoured vessels.

[whswhs]

Originally Posted by khorboth

In my supersoldiers game, I wanted both good FTL travel and a good reason for people to go into stasis during it. So, I created an FTL drive where objective (outside the ship) travel speed was measured in hundreds of times the speed of light. Then, I had subjective (inside the ship) travel speed stuck at speed-of-light. So, a 10-light-year trip might take hours of objective time, but would be four years of subjective time. I then just refused to explain how the physics worked. Nobody fully understood the physics in-universe. It wasn't important to the game.

By "subjective time," do you mean physiological time (so you need to have enough oxygen for ten years, for example) or time as subjectively experienced in the privacy of your own mind (so that your mind is experiencing several hours of duration for each second of physiological time)? James Blish had an odd story, "Common Time," that used the latter assumption. . . .

[khorboth]

Originally Posted by whswhs

By "subjective time," do you mean physiological time (so you need to have enough oxygen for ten years, for example) or time as subjectively experienced in the privacy of your own mind (so that your mind is experiencing several hours of duration for each second of physiological time)? James Blish had an odd story, "Common Time," that used the latter assumption. . . .

Yes, subjective time is physiological time. Yes, you'd need years of supplies. With TL10 recycling tech, this is not a huge obstacle, but it really indicated medicsl stasis for sanity. Also, extremely reliable ships which could operate independently for years or decades.

[Fred Brackin]

Originally Posted by khorboth

I
In my supersoldiers game, I wanted both good FTL travel and a good reason for people to go into stasis during it. So, I created an FTL drive where objective (outside the ship) travel speed was measured in hundreds of times the speed of light. Then, I had subjective (inside the ship) travel speed stuck at speed-of-light. So, a 10-light-year trip might take hours of objective time, but would be four years of subjective time. .

Your math isn't adding up. 10 light years at the speed of light is 10 years.

Then 10 light-years in a "few" hours (4 hours, 20 minutes and change) is something like 20,000x the speed of light. 365.25x the speed of light would be 1 light-year per day.

I don't really care about what numbers you used. I just didn't want incorrect math propagating itself farther down this thread. Matching FTL speeds and distances is apparently not natural for many people.

[khorboth]

Originally Posted by Fred Brackin

Your math isn't adding up. 10 light years at the speed of light is 10 years.

Then 10 light-years in a "few" hours (4 hours, 20 minutes and change) is something like 20,000x the speed of light. 365.25x the speed of light would be 1 light-year per day.

I don't really care about what numbers you used. I just didn't want incorrect math propagating itself farther down this thread. Matching FTL speeds and distances is apparently not natural for many people.

Thanks for catching my math. I changed my example partway through and didn't fix everything.

I had a spreadsheet when the game was active. Yes, trips were hours or days. I recall measuring drive speed in "CC" or hundreds of times the speed of light. So your example would be a 200CC engine.

For verisimilitude, I had colloquial ways of referring to such things in-universe. Because of exactly what you said. It's hard for people to conceptualize the bigness.

[ericthered]

Originally Posted by khorboth

Start with the feeling and themes of the setting and then decide what kinds of spaceships exist there.

I completely agree, and this is how I design my star drives.

Lawmen of Borlo needed a setting where world about a resource rush could reach population centers quickly and then take a decently long time for people to get there, but it still made sense to have the galaxy sparsely seeded with settlements. I used a jump-drive system that could make extremely long jumps, but with a low degree of accuracy (a 20,000 ly jump had a 25% margin of error). Smaller jumps had better accuracy. I think each jump took about a week. Jumping to around exceptionally large stars/black holes let you get better accuracy, and the solar system had built a hideously expensive artificial anomaly that gave a similar performance boost. We never actually went to space, but the basics of the system came up a bunch, because they determined what resources where and weren't available.

I've got a setting I played a couple of games in about exploring the stars with a stardrive for the first time. I used warp drives with speeds from around 5c to 100c, depending on circumstance. I had "roads" of space that were "easier to warp", and an alien civilization built around those. Every new world was a big deal, and each voyage was a big deal... which was the point, because it was an exploration game.


I've got an expansive space empire setting I hope to play with soon, where I'm trying to do a kitchen sink treatment. Its FTL connects different pockets of time and space via a jump drive with jump points that are sensitive to time, and they may be open hourly or maybe only every six months. This lets me present isolated networks of "territory" that have a given culture. And cut off areas if they prove to be problematic, or tell the PC's they only have to stall the invaders for two months instead of defeating them.


Dreadstormers uses Jump drives with a 5 day lapse and take two jumps to get between close systems. I needed time for the players to take over the ship, and the travel time is their clock. I also am using jump drive like traveller because the ship was designed for a "everything is on fire" scenario, and I wanted an excuse to fill the ship with flamable hydrogen bricks. And to make the machinery involved as troublesome as possible, so we have a spinning jump core, capacitors to dump energy into it, and plasma emmiters to flood hyperspace with hydrogen to inflate the bubble of reality.


Space Boarders I never answered those questions for. The players didn't drive ships, they boarded them violently.

So, I created an FTL drive where objective (outside the ship) travel speed was measured in hundreds of times the speed of light. Then, I had subjective (inside the ship) travel speed stuck at speed-of-light.

Ok, that's cool and unique. Well done.

[Donny Brook]

In my space setting, the C limit is a function of the curvature of space. FTL drives work by transiting 'subspace', thereby going 'straight' rather than around the curve. Accordingly, travel time is still distance related, but much faster than C.

Internal subspace drives appear at TL10, but rudimentary subspace gates are possible at TL9.