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Old 08-04-2021, 11:02 PM   #1
Greg 1
 
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Default Spaceship Tech in your Setting

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?
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Old 08-05-2021, 04:07 AM   #2
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Default Re: Spaceship Tech in your Setting

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.
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Old 08-05-2021, 07:31 AM   #3
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Default Re: Spaceship Tech in your Setting

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

Last edited by khorboth; 08-05-2021 at 12:03 PM.
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Old 08-05-2021, 08:58 AM   #4
David Johnston2
 
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Default Re: Spaceship Tech in your Setting

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.
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Old 08-05-2021, 09:04 AM   #5
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Default Re: Spaceship Tech in your Setting

Quote:
Originally Posted by khorboth View Post
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. . . .
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Old 08-05-2021, 09:11 AM   #6
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Default Re: Spaceship Tech in your Setting

Quote:
Originally Posted by khorboth View Post
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.
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Old 08-05-2021, 09:31 AM   #7
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Default Re: Spaceship Tech in your Setting

Quote:
Originally Posted by Greg 1 View Post
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?
So I'm working on a fantasy campaign but I've thought a lot about a future space campaign in terms of traveling faster than light. yeah I am a geek so I sit around thinking about these things.


So in my universe you travel between the starts using on the fly wormholes. They take an immense amount of power to generate and the cost rises however long the wormhole is around. I have g-drives which allow propulsion using reactor style power plants. I assume the universal theory has panned out at some point. So most ships get up to an incredibly high speed, fill every battery on board the ship using their reactors, and then open a wormhole.

The end result is a universe something like travellers. The cost in power is related to the distance, size, and duration of the wormhole. I haven't figured those details out but if I run a space game I will. At some point the power cost becomes so prohibitive that jump beyond that distance is practically impossible.

As a note. Ships can be equipped with wormhole drives but you can go through a wormhole generated by something else. So some solar systems have space stations, incredibly huge massive space stations, that generate gates for ships traveling through. Typically you pay a fee to use these gates.

I also go with the idea that reactor power is plentiful but not limitless.
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Old 08-05-2021, 10:15 AM   #8
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Default Re: Spaceship Tech in your Setting

Quote:
Originally Posted by whswhs View Post
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.
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Old 08-05-2021, 10:20 AM   #9
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Default Re: Spaceship Tech in your Setting

Quote:
Originally Posted by Fred Brackin View Post
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.
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Old 08-05-2021, 10:35 AM   #10
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Default Re: Spaceship Tech in your Setting

I intend to use Spaceships for my Harpyias setting, but I've got a lot of custom systems (and departures) involved there. The drives are generally pseudovelocity boost reactionless drives (but change to provide real velocity - albeit not much of it - for combat, which is meant to have fighters performing roughly like WWII fighter planes, capital ships performing roughly like WWII naval vessels... which also means the combat systems from Spaceship won't really work). Reactor systems are by-and-large nonexistent, replaced by supercapacitors that largely outperform chemical energy reactors while nuclear reactors are untrusted and incredibly illegal. The preferred weapons of the setting, blasters, scale differently from Spaceships weapons (a 10 MJ blaster takes 10x the power and does twice the damage of a 1 MJ blaster, just as in default Spaceships, but is only about 5x as heavy rather than 10x; at least, that's the current intent). I haven't entirely worked out exactly how I want the shields to work, other than their ablation being slow but steady (essentially, high shield HP, low regeneration), the vessel's armor actually having an influence (the shields serve more to just weaken the attack enough armor can deal with it than absorb it outright; this may just work out as the shield benefitting from the vessel's DR), and the attacker having the option to take a penalty to lessen or even outright ignore the effect of the shield (which is often a faster route to victory than pounding the shield until it collapses).

For FTL, all the stars of note that humans can travel between (which doesn't include Sol) are extremely similar and arranged in a suspiciously-regular formation, making regular tetrahedrons where each such star is 50 light years away from 4 other such stars. Travel involves getting around 60 AU from a star (which takes around a week to reach from said star's habitable zone), transitioning to hyperspace (which doesn't require any additional hardware - the typical reactionless drives can manage this, and serve to propel the vessel forward in hyperspace), traveling for around two weeks within hyperspace, then dropping back out around 60 AU from the destination star, after which point you're looking at another week's travel to reach the habitable zone, for a total of around a month. Staying in hyperspace for longer isn't advisable - hyperspace is itself corrosive, and sticking around for longer than a couple weeks risks having your armor slough off, and once that's gone the ship and crew will be consumed in rather short order. Indeed, the damage to the vessel's armor from just two weeks is enough to make it less protective (putting invading forces at a bit of a disadvantage) until it receives proper maintenance (which typically consists of removal and replacement, with the old armor being recycled). There are workarounds, such as armoring one's vessel more heavily to give some ablative layers that can safely be sloughed off during travel, that can allow more rapid travel between non-adjacent stars, but this is rarely considered to be worth the risk.

I intend to have spacecraft be markedly more affordable, to encourage PC's owning their own (the setting is heavily inspired by Star Wars) but haven't decided exactly how I'm going to do this (although having the supercapacitors, drives, and shielding systems be rather inexpensive is going to play a big role).
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