I'm actually already dealing with this myself- my old setting that I used for my 3.0/3.5 long-running epic campaign featured advanced technology and some of its consequences; for example the world has six equatorial space elevators linked to an immense ring-shaped station at the geosynchronous orbital position. So in updating the setting to PF rules, I've been looking back through Dragonstar as one of the sources to figure out what to do.
Gunslinger I'm already planning to make at least one Archetype focused on using advanced-tech weapons such as laser pistols; it's obvious that such an Archetype should exist if Gunslingers exist at all. More than one Archetype may be possible to squeeze out here, though I haven't delved deeply enough yet to be sure.
An issue you didn't touch on is gravity- and more specifically, microgravity and how to handle freefall. I decided to do it by taking the old Freefall skill from Dragonstar and fold it into PF's Fly skill. EDIT: Also, I almost forgot, there needs to be a Freefall condition to take into account the penalties associated with going out of control in a microgravity situation. The fun part about doing it this way is, you can make spells which inflict the condition upon people- even old favorites like Reverse Gravity might be retrofitted to include it. Other rules regarding gravity can mostly be ported over unchanged, as far as I've been able to tell.
Vehicle rules introduced in Ultimate Combat may need serious updates to deal with starships, particularly technological drives. I haven't gotten to this myself, yet, so don't have any solutions of my own to list here.
I forgot about gravity--that's another good one. I can't recollect Dragonstar's rules for variant gravity but if I had to improvise some quick pre-game rules from scratch they would look like this.
[sblock]Note: These rules are not meant to serve as a scientific treatise but are only meant to simulate the effects of gravity well enough to allow suspension of disbelief for the layman player. If you want to try to calculate how much momentum shooting an arrow will give a creature in a zero-g environment, don't let me try to discourage you, but bear in mind all the factors that would have to go into a realistic version of such a calculation--you would have to calculate average values for the mass the arrow, the power efficiency of the bow, wind resistance effects, and the average mass of a player character (and if you wanted to have monsters and NPCs perform the same stunt, they come in an even greater range of masses, because a Huge creature would gain less from a bowshot than a Small one.[/sblock]
GRAVITY LEVELS--DEFINITIONS
Gravity environments range in strength from 0 to 10. A gravity level of 0 denotes the absence of gravity. Gravity in the range of 1 to 3 is considered "microgravity". Gravity of strength 4 to 6 is considered "normal" and imposes few penalties on creatures acclimated to life on a conventional planetary surface. Gravity of a strength from 7 to 9 is found on super-Earths, in the deep atmospheres of gas giants, and in high acceleration environments (such as experienced by fighter pilots) and represent the limits of survivability for mortal creatures. Gravity strength 10 represents any extreme light-bending gravity field generated by such objects as neutron stars, black holes, Spheres of Annihilation, and Implosion spells.
Gravity Strength Table
[sblock]0 Zero (0 g) a.k.a. freefall
1 Nil (1/10 g or less)
2 Faint (1/4 g)
3 Light (1/2 g)
4 Light Normal (4/5 g)
5 Normal (1 g)
6 Heavy Normal (1 1/5 g)
7 Heavy (1 1/2 g)
8 Severe (3 g)
9 Crushing (9 g or more)
10 Relativistic gravity
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Antigravity, where it exists, would be represented by a negative number of the same magnitude as a normal gravity field of equal strength.
MOVEMENT
Normal overland movement in a gravity environment of 3 or less requires making a Climb, Swim, Acrobatics, or Fly check* for those not acclimated to the variant gravity or untrained in moving around in it. If a creature is physically incapable of performing any of these (for example, being in free fall in vacuum with no solid surfaces in reach), they gain the free-floating condition (lose dodge bonuses and Dexterity to AC and Reflex saves, move actions are limited to worn/carried equipment)?
*Free-floating movement in a freefall environment
[sblock]In freefall, Fly checks can be made through the use of worn/carried equipment. For example, throwing a rock, shooting an arrow, or discharging a firearm in a certain direction will cause you to move very slightly in the opposite direction. Objects and rates of movement are as follows.
Throwing a minor object (anything with a weight of "—"): 5 ft per object thrown, per hour
Throwing an object of less than 10 lb.: 5 ft per minute
Throwing an object of 10 lb or more: 25 ft per minute (5 ft in 2 rounds)
Shooting a bow, crossbow, or similar hand-drawn weapon: 50 ft per shot, per minute (5 ft per round)
Discharging a personal firearm or firing a ballista: 500 ft per shot, per minute (50 ft per round)
Note that one can throw/shoot/fire multiple objects to increase one's speed in a given direction, or reduce it (by aiming in the direction of movement).
If a creature in freefall needs to propel himself toward a specific point (such as the door of an airlock or toward another creature or a weapon in freefall), he must make a Wisdom check to accurately propel himself in the appropriate direction; DC is equal to object's touch AC +2 per 10 feet of distance. If the creature fails the Wisdom check, he will miss the target's square by 5 feet per point missed.
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RESILIENCE
Variant gravity can have an influence on how far a creature can run, swim, or perform other stressing manual labor before it becomes fatigued or exhausted.
Variant gravity modifies normal character speed and imposes a modifier on Constitution check DCs made to continue running (or climbing, swimming, acrobatics, etc.)
0: n/a
1: triple base speed, -8 to Con check DCs
2: double base speed, -6 to Con check DCs
3: double base speed, -4 to Con check DCs
4: base speed is normal, -2 to Con check DCs
5: no modifiers
6: base speed is normal, +2 to Con check DCs
7: base speed is halved, +4 to Con check DCs
8: base speed is 20% normal (min. 5 ft for most creatures), +6 to Con check DCs
9: base speed is 10% normal or less, +8 or more to Con check DCs
10: n/a
Walking, hustling, or forced marching in a high-gravity environment (strength 6 to 9) causes trouble for creatures acclimated to a lighter gravity.
6: May walk 4 hours without penalty, each hour of forced march imposes a Con check (DC 12, +2 per extra hour). May hustle for one half-hour without taking nonlethal damage, and then must make a Strength check (DC 12) every ten minutes to continue hustling.
7: May walk 1 hour without penalty, every half-hour of forced march imposes a Con check (DC 14, +2 per extra half-hour). May hustle for ten minutes without taking nonlethal damage, and then must make a Strength check (DC 14) each minute to continue hustling.
8: May walk ten minutes without penalty, every ten minutes of forced march imposes a Con check (DC 16, +2 per extra ten minutes). May hustle for one round without taking nonlethal damage. A Strength check (DC 18) is required each round to continue hustling.
9: May walk 1 round without penalty, each round of forced march imposes a Con check (DC 18 or more, +2 per round). Hustling for one round deals 1 point of nonlethal damage each round. A Strength check (DC 20) is required each round to continue hustling.
(Creatures acclimated to low-gravity or zero-gravity will suffer similar problems in a moderate-gravity environment.)
FALLING DAMAGE
Falling damage is attenuated by gravity level, which is represented by stepping falling damage dice up or down (for example, rolling d4's instead of d6's) and by increasing the falling increment of damage dice. The usual damage cap of 20 falling-damage dice applies only to falls in within an atmosphere, but in an airless environment this damage cap does not apply and falling damage is allowed to increase without limit. For all other falling-damage rules (as listed here:
Environment), make the following substitutions:
1d6 (or 2d6 or 5d6) == 1 die (or 2 dice or 5 dice) of falling damage
10 (or 20 or 50) feet == one (or two or five) falling increment/s
[falls from] greater than 500 feet == [falls from] greater than 50 falling increments
Also, objects that fall on a creature in a variant gravity environment deal damage according to the strength of the gravity field.
Small = 2 damage dice
Medium = 3 damage dice
Large = 4 damage dice
Huge = 6 damage dice
Gargantuan = 8 damage dice
Colossal = 10 damage dice
Gravity level, Falling Damage, and Damage From Falling Objects
0: no falling damage possible**
1: 1d4 per 100 ft. [object damage: 1 point, i.e. medium does 3 points]
2: 1d4 per 50 ft. [object damage die: d2]
3: 1d4 per 20 ft. [object damage die: d3]
4: 1d4 per 10 ft. [object damage die: d4]
5: 1d6 per 10 ft. [object damage die: d6]
6: 1d8 per 10 ft. [object damage die: d8]
7: 1d10 per 10 ft. [object damage die: d10]
8: 1d12 per 10 ft. [object damage die: d12]
9: 1d20 (or more) per 10 ft. [object damage: d20 or greater]
10: Objects that fall into a relativistic gravity well are utterly destroyed and cannot be retrieved except by a Wish or Miracle.
**Damage from pushed, thrown, and shot objects in a freefall environment
[sblock]These objects follow the same rules as for improvised weapons. Very large objects (such as large cargo containers) can be used as (very slow, 5 ft/round) improvised ranged weapons. A creature can push an object of a weight up to the push/drag value for their Strength score to deal damage as an improvised weapon of its size, but can only target an unaware or helpless creature who could be caught and crushed against another solid surface by the heavy object. (Anyone else will have plenty of time to get out of the way or will simply be pushed out of the way.)
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* * * * * * * * * * * * * * * * * * * *
Also, Salthorae's mention of Distant Worlds reminds me about teleportation and the 9th-level spell Interplanetary Teleport (which actually appears in Inner Sea World Guide and Ultimate Magic rather than DW). As written, the spell seems to allow even inter-stellar teleportation, something which had been expressly forbidden in the original Dragonstar setting. This issue can be resolved however by retroactively stating that
(a) the spell exists;
(b) the magic that goes into crafting starcaster drive systems actually uses this spell (or some variant);
(c) for economic, military, and/or political reasons, the knowledge that such a spell can be researched has historically been aggressively suppressed by the state;
(d) like any trade secret, those few corporations who know how to build starcrafter engines jealously guard such knowledge.