Extensible spin habitats in GURPS Spaceships

[Proteus]

I'm toying for the first time with the GURPS Spaceships rules, for a semi-hard TL 9 setting that lacks artificial gravity.

I see the rules on p. 30 for "Spin Gravity," based on the SM (and thus the radius) of the vessel. What I don't see are rules for the sort of designs where habitats can be extended or retracted (or, in extreme cases, reeled and unreeled) to produce effective radii far larger than the craft's normal one.

Perhaps, if a habitat occupies double space (and double cost, not including specialized rooms), it could be extended to provide spin gravity as if the ship were the next SM larger. So, for example, a SM+10 exploration ship which payed double (space and cost) for its crew quarters could extend them outward to produce 0.3G when spinning (as for SM+11) rather than 0.2G (as for its actual SM+10). I know hull spaces generally go up by threes, but this seems a much more limited use than one would get from the usual scaling process.

So, does that sound more or less fair?

Follow-up question: what if the naval architect wants an even further separation? Some real-world designs have included cables to achieve large separations for spin. Would it be appropriate to continue doubling (so our SM+10 ship needs the equivalent of four spaces for the habitats to spin for 0.5G, emulating SM+12)? Or might it be better merely to charge one additional hull space per extension (so that those four spaces would now let our SM+10 ship's single habitat emulate SM+14, or a full 1G)?

Which of those options sounds more reasonable to the assembled GURPS gurus?

Whichever the solution, I'm guessing that each extension would impose an additional -2 on Handling while in use, above and beyond the -2 assessed purely for having spin gravity in the first place.

Having not yet messed with the space-combat rules, I don't know how long the actual extension or retraction process should take -- but I'm pretty sure it should be decided ahead of time, since it's bound to come up. Help would be appreciated there, too, in coming up with a reasonable and balanced answer.

[Langy]

Originally Posted by Proteus

I see the rules on p. 30 for "Spin Gravity," based on the SM (and thus the radius) of the vessel. What I don't see are rules for the sort of designs where habitats can be extended or retracted (or, in extreme cases, reeled and unreeled) to produce effective radii far larger than the craft's normal one.

I believe those rules eventually wound up being in SS7. Not positive they're in that book, but I'm sure I saw them somewhere.

[vierasmarius]

Originally Posted by Langy

I believe those rules eventually wound up being in SS7. Not positive they're in that book, but I'm sure I saw them somewhere.

Yup, they're in SS7 (p.22). It's a bit more involved than the OP's idea though, with the spin capsules built as independent vessels connected by a tether.

[Humabout]

It's still a really nifty hard science way of achieving higher Gs with smaller vessels.

[Flyndaran]

Wouldn't be a massive hassle to go back and forth from the tethered capsule to the main ship?

[Humabout]

Depends on the setup. I could see a car that runs teh cable, if necessary, but otherwise, the ship could be designed so there's no need to cross from one to the other (frex, a cargo ship with the living quarters in one side and cargo holds in the other). With regard to the OP's post, I'm not sure why you'd bother making a settlement so small as to require a spin tether to achieve 1G at the ends. A giant wheel (or variation thereon) would probably be more cost efficient, once the space was all sold/rented off.

[Proteus]

Originally Posted by Flyndaran

Wouldn't be a massive hassle to go back and forth from the tethered capsule to the main ship?

You might build in a small elevator.

Or you might just teleoperate robots instead, using signals sent down the cable.

Or you might just not need to leave the habitat; with lower-tech drives and limited delta-V, you might be coasting for a very long time; let the rest of the ship run quiet and dark, while you reel out the habitats and kick back until arrival.

So the solution is to build the system as entire small ships for the habitats? That seems excessive for the gloriously simple Spaceships rules.

Do the separately-built habitats then get attached to the main vessel -- or is the proposed solution one specifically to model the design I saw (for a Mars cycler?) where you had two identical small ships which linked up together on a long cable so they could both enjoy a long spin radius?

Originally Posted by Humabout

With regard to the OP's post, I'm not sure why you'd bother making a settlement so small as to require a spin tether to achieve 1G at the ends.

I'm not looking for a settlement: I'm looking for a long-duration exploratory vessel using one of the setting's few super-science bits, a wormhole network for FTL travel. So the setting has FTL, and access to multiple solar systems, but no artificial gravity; folks are going to want a spin habitat, and may have long quiet spaces where they don't need to maneuver.

Thus my proposed rules. Any comments on those? How do they compare with the results of the vessel statted in Spaceships #7?

[Flyndaran]

Ignoring cosmic radiation? Or do you assume medical technology can fix that but not zero g problems?

[Humabout]

Originally Posted by Proteus

I'm looking for a long-duration exploratory vessel using one of the setting's few super-science bits, a wormhole network for FTL travel. So the setting has FTL, and access to multiple solar systems, but no artificial gravity; folks are going to want a spin habitat, and may have long quiet spaces where they don't need to maneuver.

Thus my proposed rules. Any comments on those? How do they compare with the results of the vessel statted in Spaceships #7?

For an exploratory vessel, yeah, a tether would help, so long as you don't intend to operate sort of continuous acceleration drive (ramscoop, reactionless drive, etc.)

With regard to how it meshed with SS7, um, it's really handled quite differently. As someone already stated, in SS, you'd make two separate craft and determine the mass/cost of the tether afteward. From there, you get other stats, including things like your penalty to handling.

Frankly, unless you intend such a vessel to contend with combat, I'd not particularly worry about the tether. And if they are going to enter combat, they'll probably be sitting ducks. Tethers and combat really don't look like they mix too well.