[Spaceships] Starfire to GURPS conversions? (revisited)

[DaltonS]

It's been over four years since the last post to that thread, so I thought I'd start fresh. Since then, a new version of the Starfire game called Solar Starfire has come out. Based on the Ultra Starfire rules, this game is set in a different universe from that of the Starfire books by David Weber and Steve White. Some things are the same:

1. Warp Points - which in GURPS terms are natural Jump Points connected in jumplines that can used by any vessel with a sufficiently strong Drive Field and are anomalies in space/time which allow starships to make instantaneous transits over interstellar distances. They usually form in the strong gravitational fields around stars and do not orbit the star, but move with it through space at a fixed distance and bearing relative to the local stellar neighborhood. Occasionally, a group of warp points will form in deep space, away from a star’s influence but still remain in the same relative positions in respect to each other. Oddly enough, a “Starless Nexus” (starless area with warp points) generally has a larger number of jump points than star systems do, and scientists speculate the reason is because the gravitational fields either distort, hide, or simply degenerate (destroy) warp points around the stars. They share certain common traits;
   1. Capacity - which is the maximum size of the vessel that can transit a WP in a single turn. Larger vessels can still transit the WP in Size/Capacity turns. Multiple smaller vessels may transit a WP simultaneously, but if the total size of the transit exceeds the WP’s capacity, some vessels may inter-penetrate on arrival and be destroyed. Warp points may be thought of as “gravity whirlpools” whose “gravity surge” will destroy units or objects without sufficient drive-field strength to protect them (such as missiles, fighters, etc.). Only WPs of the same capacity may be linked. Vessels may adjust their effective “transit size” by selecting specific types of drives and hull configurations.
   2. Visibility - which determines how difficult it is to find the WP in the first place. Finding any WPs at all is difficult task at best, requiring either a) a detailed gravimetric survey of the entire system or nexus (this is where “visibility” factors in), or b) observing another vessel’s “transit signature” as they use a WP. For option (a) to occur, a race must first know that WPs even exist, which doesn’t happen until they have mastered the physics behind “reactionless drive”; once they have however, predicting the existence ofWJPs is inevitable. Option (b) is much easier and needs less advanced tech, but requires that someone is looking in the right direction first. WPs of any visibility may be linked (except under optional rules).
2. Reactionless Drive - which in GURPS terms might be considered a “Stardrive (Reactionless)” with “Drive Field”, “Pseudo-Velocity” and “Boost Drives” design switches. While technically a Stardrive, its FTL capability cannot be discovered until the existence of Warp Points is, so it is treated as an STL drive most of the time. In fact, since its FTL function is an incidental side-effect of its Drive Field and is unleveled, it would be more accurately described as a “Reactionless (Star)Drive” with the above design switches. Since it allows travel at c-fractional speeds (1 speed level=1/120 c = 2,500 kps = 1,550 mps = 30 c-seconds/hour) in deep space it quickly replaces all other types of space drive for interplanetary (and later interstellar) travel. (The only reaction engine mentioned was essentially a bi-directional spinal charged particle beam used for propulsion that requires an “Inertia-Conversion Field” to transit a Warp Point.) Maximum speed is limited by the engine type, its tech level and the ship’s hull size (larger hulls are slower). After that point, additional systems are only useful a spares unless the ship’s effective tonnage is increased by towing or carrying (externally) other vessels.

My attempt at the GURPSification of Starfire has focused on how to insert these two elements into a GURPS Space campaign. The first sentence of the introduction to Solar Starfire by Marvin R. Lamb is

The STARFIRE gaming system is a “4X” (eXplore, eXpand, eXploit, eXterminate) game that has been designed to simulate tactical combat between starships and campaign-style empire building in space.

Not exactly the RPG style, is it? (Unless you're Igor Olman of “Dork Tower”. ;) ) The following posts will describe in detail what I've come up with. (BTW, from here on I'll be referring to "Warp Points" as "Jump Points" because this is GURPS. :) )

Dalton "whose ideas may be warped, but to the point" Spence

[DaltonS]

Generating Jump Points

                 Table 1: Jump Point Quantity                || Table 2: Jump  |
   For each system roll 3d    |   If 16+ rolled, reroll 2d   || Point Distance |
------------------------------+------------------------------||----------------|
# of |Starless|Without| With  |# of |Starless|Without| With  ||Roll  Distance  |
 WPs | Nexus  |Planets|Planets| WPs | Nexus  |Planets|Planets||(3d)  (lm) (AU) |
-----+--------+-------+-------+-----+--------+-------+-------||----------------|
  1  |  3-4   |  3–6  |  3–7  |  6  |  2-5   |  2-6  |  2-7  ||  3   1.0  0.12 |
  2  |  5-7   |  7-8  |  8–9  |  7  |  6-7   |  7-8  |   8   ||  4   1.5  0.18 |
  3  |  8–10  |  9–11 | 10-12 |  8  |   8    |   9   |   9   ||  5   2.5  0.3  |
  4  | 11–12  | 12–13 | 13–14 |  9  |  9-10  |  10   |  10   ||  6   3.5  0.42 |
  5  | 13–15  | 14–15 |  15   | 10  | 11-12  | 11-12 | 11-12 ||  7   5.0  0.6  |
-------------------------------------------------------------+|  8   7.5  0.9  |
       Table 3:     ||    Table 4: Jump Point Visibility     ||  9    10  1.2  |
  Jump Point Types  ||        Visibility  Survey  Sensor TL  || 10    15  1.8  |
Roll  --Jump Point--|| Roll    Level      Roll    Required   || 11    25   3   |
 2d   Type  Capacity|| (2d) --- Conventional Jump Points --- || 12    35  4.2  |
 2-3   A     SM+7   ||  2-7     Open       15-    Late TL9   || 13    50   6   |
 4-5   B     SM+8   ||  8-9   Concealed    14-   Early TL10  || 14    75   9   |
 6-7   C     SM+9   ||   10    Hidden      13-    Mid TL10   || 15   100   12  |
 8-9   D     SM+10  || 11-12   Secret      12-   Late TL10   || 16   150   18  |
  10   E     SM+11  || (1d) -- Unconventional Jump Points -- || 17   250   30  |
11-12  F     SM+12  ||  1-3   Top Secret   11-   Early TL11  || 18   350   42  |
                    ||  4-6   Undisclosed  10-    Mid TL11   ||(lm) = c-minutes|
-------------------------------------------------------------------------------|
Table 5: Optional modifiers to Type and Visibility Rolls by Distance from Star |
  Blue Giant (O,B)| Red Giant, A0-A9 |Main Sequence (F0-M4)| M5-M9, White Dwarf|
  Range  Modifier |  Range  Modifier |    Range  Modifier  |   Range  Modifier |
  (lm)   Type Vis.|  (lm)   Type Vis.|    (lm)   Type Vis. |   (lm)   Type Vis.|
   1–24   -3  +2  |   1–12   -2  +2  |     1–12   -2  +1   |   1–12    -1  +1  |
  25–48   -2  +2  |  13–36   -2  +1  |    13–36   -1  +1   |  13–36    -1   —  |
  49–96   -2  +1  |  37–60   -1  +1  |    37–60   -1   —   |  37–252    —   —  |
  97–132  -1  +1  |  61–96   -1   —  |    61–276   —   —   | 253–276   +1   —  |
 133–180  -1   —  |  97–312   —   —  |   277–300  +1   —   | 277–312   +1  -1  |
 181–348   —   —  | 313–336  +1   —  |   301–324  +1  -1   | 313–336   +2  -1  |
   349+   +1   —  |   337+   +1  -1  |     325+   +2  -1   |   337+    +2  -2  |

For each system or Starless Nexus:

1. Roll on Table 1 to determine the number of conventional JPs.
2. For each JP,
   1. roll 3d on Table 2 to determine the distance from the JP to the center of the system (an arbitrary point for a starless nexus or the primary of a star system). For a finer adjustment, multiply this value by (1d/10+0.7). Optionally, in a star system the following rolls may be modified by this distance using Table 5.
   2. roll 2d against Table 3 to determine type and capacity.
   3. roll 2d against the first part of Table 4 to determine visibility.
3. After regular JP generation, roll 3d for unconventional JPs. If 15+,
   1. roll for distance as per step 2.a above.
   2. roll 2d against Table 3 to determine the JP’s type and capacity.
   3. roll 1d against the second part of Table 4 to determine the JP’s visibility.
   4. roll 3d. If 15+, repeat from step 3.a.
4. For each JP generated so far, the bearing in degrees from the system center is ((1d×6+1d)×10-(2d+3)×2). If less than 0°, add 360°. This generates an even° bearing only; add 1 on a roll 1-3 of 1d.
5. Add these JPs to the lists of unlinked JPs (each Type has its own list) to be linked later.

Dalton "whose ideas may be warped, but to the point" Spence

[DaltonS]

Reactionless Drives (TL9^) [REAR!]
This would be more accurately described as a “Reactionless (Star)Drive” with “Drive Field”, “Pseudo-Velocity” and “Boost Drives” design switches. Since it allows travel at c-fractional speeds (1 speed level=1/120 c = 2,500 kps = 1,550 mps = 30 c-seconds/hour) in deep space it quickly replaces all other types of space drive for interplanetary (and later interstellar) travel. Maximum speed is limited by the engine type, its tech level and the ship’s hull size (larger hulls are slower). After that point, additional systems are only useful a spares unless the ship’s effective tonnage is increased by towing or carrying (externally) other vessels.

Reactionless Drive Types

• Inertialess (Late TL9^) - This is typically the first reactionless drive invented. It has a sensor blindspot 60° directly aft (120° on a speed optimized hull). This is a military system.
• Commercial (Late TL9^) - The commercial engine, also know as the commercial drive, is designed for high reliably and superior speeds for long haul trips. This is a direct spinoff of Inertialess drive and has the same sensor blindspot.
• Tactical (Early TL10^) - These operate much the same as Inertialess engines. For the advantage of faster tactical speed (and essentially controlling the fighting range), they sacrifice strategic speed, transit effectiveness, Long Range Weapons range, and have a larger blindspot (120°/180°). Each full size system can boost 1.5 speed levels, so smaller SM systems are often used.
• Gravimetric (Early TL11^) - Scientists figured out how to manipulate the drive-field to create an imbalance in the gravity field just outside the drive-field that will push or pull the drive-field. These new drives have higher power ratios, faster strategic speeds, no true blindspot, and quicker turning. But this comes at a cost: weapons fire is more difficult through the gravity imbalance (–1 for firing in the rear and forward 60° arc (120° for speed optimized hulls), the overall strength of the drive-field is reduced making the the maximum speed 3 levels slower compared to Inertialess drives at the TL period. Each full size system can boost 2 speed levels, so half-size systems are often used.
• Cosmic (Mid TL11^) - After extensive research, the Cosmic drive was developed, powered by Cosmic power points from a specially designed Vacuum Energy Power Plant (GURPS Spaceships 7, page 16). These drives are designed to push a drive field equipped hull at a rapid pace for very few hull spaces. The engine blindspot is 120° (180° for speed optimized hulls). Each full size system can boost 3 speed levels, so smaller SM systems are often used.

            Table 6: Reactionless Drive Types           ||
Reactionless    When      Speed Factors         Cost    ||    Movement Points Scale
Drive Name    Invented  Base  Max  Cruise TSA  Same As  ||    Turn      Hex Size in
Inertialess   Late TL9    1  11-SM   1/2   +0  Standard ||   Length  c-sec. miles   AU
Commercial    Late TL9   0.5  9-SM    1    +2   Rotary  || 20 seconds 1/6  31,000 0.0003
Tactical     Early TL10  1.5 13-SM   1/3   -1    Hot    ||  1 minute  0.5  93,000 0.001
Gravimetric  Early TL11   2  13-SM   3/4   +4    Super  ||  3 minutes 1.5 279,000 0.003
Cosmic        Mid TL11    3  19-SM   1/3   +5   Subwarp || 10 minutes  5  930,000 0.01

When Invented - GURPS tech level this drive was introduced at. These levels have been subdivided into Early, Mid and Late periods, with each period representing a generation of tech development. (Ex. Tactical drives at Early TL11 are 4th generation.)
Base - speed level per system installed. This doubles at the first full tech level after introduction (Ex. Late TL10 for Inertialess and Commercial).
Max - Maximum tactical speed at the time of introduction adjusted for the size of the ship. This increases 1 level per drive generation (1/2 a level for Commercial drives). (Example: a 4th generation Tactical drive has a maximum speed 3 levels higher than that of a 1st generation Gravimetric one of the same TL period.) This can increased slightly by DeTuning the engines. If the maximum speed is 0 or less, the drive may still be used in Standby Mode.
Cruise - Maximum Strategic (safe cruising) speed as a fraction of Tactical speed. Maximum LOD (low detection) speed is half that.
TSA (Transit Size Adjustment) - A drive’s TSA reduces the ship’s effective transit size by 1 SM for each level. An additional level is added to the TSA for each generation of drive and for speed optimized hulls.
Cost Same As - Reactionless Drive Type cost as per GURPS Spaceships page 24.

Dalton "whose ideas may be warped, but to the point" Spence

[DaltonS]

Drive Field
The “Drive Field” (or DF) is the most important part of the drive system; not only does protect the ship against the hazards of traveling at c-fractional speeds (treat as a Light Force Screen), without one a ship cannot survive a JP transit. Vessels carried in “Transit Racks” are considered inside the DF while those towed by tractor beams are not. When a DF is active, the ship is not influenced by gravity. The ship’s speed is relative to the local gravitational environment; that is the nearest star in interplanetary space, the nearest planet if its gravitational influence is greater than the star, or the formation of JPs in a Starless Nexus. The drive operates in one of five modes:

Tactical Mode

Also termed full military power and the engine may burnout during extended use. Only available on military grade drives.

Strategic Mode

allows movement at or below safe cruising speed, which is without risk of burnout. This is also the top speed of commercial grade drives for obvious economic reasons.

Low Detection Speed (LOD)

sacrifices speed for stealth. If a ship is moving at 1/2 or less of its cruising speed with engines in LOD mode and with shields down, detection ranges for enemy units are reduced. Units switching from LOD to any other mode cause an LOD Flash, and can be detected for 5 seconds as if the unit’s engines were in tactical mode.

Standby Mode

The engines provide no movement points, but the drive remains active (including the blindspot). Standby mode on bases, Asteroid Forts, and Space Stations is also called Stationkeeping. A standby mode unit can move up to 0.5 c-sec/hour (0.03 AU/month or 25 5/6 mps); thus, holding orbital position.

Off

is where the engines are powered down, providing no movement points and no blindspot, but also providing no drive field protection. It resumes the velocity vector it had when the drive was last engaged, and is now subject to gravity. The drive field must be off for the ship to dock with, launch or bring aboard other vessels.

Inertia-Conversion Field (Late TL9^) [Any!]
In GURPS Spaceships terms this is a “Stardrive” with the “Drive Field” design switch. This system allows a vessel with reaction engines to transit a jump point. It takes one hour to activate, after which it functions as a Light Force Screen. The field must be off for the ship to dock with, launch or bring aboard other vessels. With the field on, the ship’s top speed factor relative to the local gravitational environment (see above) is 3×(sAccel)^0.5 due to gravitational drag (4×(sAccel)^0.5 for a speed optimized hull).

Speed Optimized Hull (Late TL9^) [Feature]
This feature reconfigures the hull to more efficiently conform to the drive field, making the ship's maximum speed one level higher, its transit size one SM smaller and its blindspot 60° bigger.

   SM     +4   +5    +6    +7   +8  +9   +10  +11   +12   +13  +14  +15
Cost($) 50K  150K  500K  1.5M  5M  15M  50M  150M  500M  1.5B  5B  15B

Atmospheric Capability (Late TL9^) [Feature]
This is a modification to the hull that adds “gravity wings”, gravity repulsors, and engine modifications that allow a ship with drive-field propulsion to drop the drive-field inside the para-gravity limit of a gravitational body (such as a planet). In GURPS Spaceships terms this is the “Force Wings” option applied to the drive field. Cost=Light Force Screen+50%.

   SM      +4    +5    +6    +7    +8    +9   +10   +11   +12   +13 or more
Cost($)  225k  750k  2.25M 7.5M  22.5M  75M  225M  750M 2.25B   —

DeTuning
In navies that have units with Short Range Weapons, the desire for the ability to move faster just to get into range before taking a lot of damage has encouraged experimentation. One of the solutions was “DeTuning” the engines, that is, temporarily altering the drive-field so that you move faster, but it can hurt your engines, partially blinds your sensors, hurts your targeting, and makes your blindspot 60° bigger. So there is a trade-off.

DeTuning is actually a slight mis-calibration of the drive field generators in the engines so that they produce an unstable drive field. If done properly, this can result in a slight speed increase (+2 for Inertialess drive, +1 for the others) at the expense of normal operations of sensory input and targeting. This isn’t always safe, as mis-calibrating too much can cause the engines to explode, even if successful they are at a higher risk of burnout, and not all drive types can perform this risky operation.

Dalton "whose ideas may be warped, but to the point" Spence

[apoc527]

How will you convert the "primaries?" The fluff is fluff, but for game mechanics, I'd probably look at a ghost particle beam.

[DaltonS]

Originally Posted by apoc527

How will you convert the "primaries?" The fluff is fluff, but for game mechanics, I'd probably look at a ghost particle beam.

I'd check out the original thread first, particularly post #6. There are lots of ideas for weapon conversions there. One of the reasons I chose the “fluff” to describe is the roleplaying factor; adventures depend a lot on timing which is often determined by how fast a character can get from point A to point B. Battles are important of course, but it's not much fun roleplaying a gun (unless it's a very smart one ;) ).

Dalton “who may reinvent the wheel, but not the sword” Spence

[DaltonS]

System Mapping

From GURPS Spaceships 5, page 31;

Starships that don’t travel through normal space but use jump drives or hyperdrives can appear in a system they haven’t studied at all. If so, it’s still possible to use any of these out-system procedures from within the star system itself.

Two elements should be added to the data collected by standard system mapping, whether it's done in game or before by the GM:

1. the game date of the system survey.
2. the position of each world in its orbit as of that date. This should be done as per Step 4 of Generating Jump Points above.

This data is needed to calculate future planetary positions and thus travel times between worlds and jump points.

Gravimetric Survey
When entering a system for the first time, a survey is required using a Science or Multipurpose Sensor Array’s gravimetric sensors to find any existing Jump Points. This is a long task that takes eight hours per attempt, during which the ship will rotate 45°/hour for full sensor coverage. Careful explorers can take full advantage of extra time and spend as long as 240 hours per attempt (at +5 to skill). (Note: This is separate from System Mapping.)
For best results, each attempt should be made with the drive field Off or on Standby Mode and its location (distance and bearing from system center) noted; subtract 1 from each Survey Roll if the drive is on Standby (due to the drive’s sensor “blindspot”). At the end of each attempt, the GM must do a Survey Roll for each JP using its Visibility, adding the Array’s scan rating (TL+SM-9) and subtracting the Distance Roll on the Table 2 inGenerating Jump Points above for the range from the ship to the JP. A normal success locates the JP within one light-minute of its actual position, while a critical one locates it within one light-second. On an ordinary failure the JP is missed by the survey, but a critical failure creates a false positive at a random location (use Table 2 and step 4 in Generate Jump Points above).

Example: A SM+9 survey ship with an Early TL10^ array and its drive Off can detect an Open JP at 3AU (25 light minutes) away on a roll of 15+10-11=14 or less. The same ship could detect a Concealed JP at the same range on a roll of 13 or less, but could not find a Hidden, Secret, Top Secret or Undisclosed JP at any range without a more advanced gravimetric sensor. At 12AU (100 light minutes), an Open JP would be found on 10 or less (a 50% chance) while a Concealed one would be found on 9 or less (a 37.5% chance).

As you can see, a comprehensive Gravimetric Survey of the system would require multiple tasks from different locations. Rather than rolling for each JP at every survey point, do one roll at the end of the comprehensive survey for each JP using a decided on bonus/penalty. To determine the number of survey points required to completely cover the system;

1. Determine the scan bonus/penalty you are willing to accept. (This should include the -1 penalty for scanning with the drive in Standby Mode if applicable.) Subtract this from the scan rating of the sensor array (TL+SM-9) to get its effective scan.
2. Look up the effective scan in the “Roll” column of Distance Table and use the corresponding distance in light-minutes as the mean separation of survey points s.
3. The number of survey points is N = (350/s)^2 rounded up.

Given that v is the speed of the ship (use Strategic Mode if the survey is overt or LOD Mode if it’s covert), (2×s/v+8)×N hours is the absolute minimum time for the complete survey by a single ship. This time can be reduced by using multiple survey ships and consolidating their data. A normal success locates the JP within one light-second of its actual position, while a critical one means a “transit signature” was observed for that JP which was used to calculate (takes 1 day) an exact position (within a 20-second hex or 31,000 miles) and transit information.

Example: Without any bonuses or penalties, the above ship would require (350/15)^2 = 545 survey points to cover the system. If the ship has a 2nd generation Inertialess Drive with a Strategic Mode speed of 1.5, it would take (2×15/1.5+8)×545 = 15260 hours (1.74 years) to complete the survey. By accepting a 1 point penalty, we can reduce the number of survey points to 196 and the survey time to 8101? hours (337.6 days or about 11 months), a reduction of 46.9%. This will still find an Open JP on 14 or less (90.7%) and a Concealed one on 13 or less (83.8%).

Dalton “getting there may be half the fun, but knowing where to go is the other half” Spence