Shields
Shields in Star Trek
Shields in star trek are somewhat flexible depending on the requirements of the plot. I take as one of the best canonical examples the final battle in the Undiscoverd Country. The Enterprise takes a pounding and the shields weaken and become leaky before finally collapsing. There are other examples in DS9 but the shields of the Reliant seem to be very weak or very strong depending on the plot. So other video games where there are good implementations of shields are Klingon Academy, Bridge Commander and Starfleet Command. Starfleet Command as it's based on Starfleet Battles tabletop probably gives a good feeling for how a tabletop game should play out. In the TV series there are shield reinforcements used in both TOS and TNG, but as Full Thrust does not have energy allocation it is probably best not to simulate this complexity.
Another option is to track shields strengths for a set of facings so that directional fire will wear down specific shields and not others. Again this is deemed to high a level of abstraction for fleet games and so shields are handled as an omni-directional system.
Shield reinforcement is also a tempting system to model but without energy allocation it doesn't work, there is a way to abstract this using armour discussed later.
A note on design philosophy we are tying to find rules that make sense in a Star Trek setting and not pit ships from other settings with Star Trek ships. If you plan to do that we suggest using Cross Dimensions (XD) as it is designed for this very purpose. This site will cherry pick the best rules for the right feel.
Screens in Full Thrust (FT)
Shields are called Defensive Screens.
These are Energy-field generators used to afford ships partial protection from some weapon attacks. They are not 'Force Fields', but systems of electromagnetic shielding than can disrupt the Particle Beams fired by ship's Beam Batteries; when a Beam shot hits a Screen,the charged particles in the Beam are partially dispersed and reduced in energy, thus reducing their potential to damage the target ship.
The actual degree of protection given depends on the 'level' of screens that the target ship is carrying. Each level is represented by a single Screen generator, so a ship with Level-1screens would be carrying a single Screen generator, while a ship with Level-3 screens would have three separate Screen systems.
Each Screen generator on a ship is considered a separate system when checking for system damage at Threshold Points, and may be knocked-out individually either by threshold damage or Needle Beam weapons: thus if a ship with Screen Level-3 has to make a Threshold damage check and loses two of its Screen systems, it drops to Level- 1 Screens.
If a ship that is protected by Screens is fired on by Beam weapons (whether 'A', 'B' or 'C' batteries), the Damage inflicted by each Die rolled is varied as follows:
For Level-1 Screens,rolls of 5 inflict one point of damage,and rolls of 6 do 2 points.(In other words, ignore any rolls of 4 that would have damaged an unscreened ship).
With Level-2 Screens,rolls of 5 and 6 each inflict only one point of damage.
For Level-3 Screens (the maximum available to any single ship), ignore all rolls except those that score 6, which do just one damage point.
Note that Screens can only protect against fire from Beam Batteries and Fighter weaponry (which are short-range Beams), and against the effects of Detonation Mines. Pulse Torpedoes and the highly-focused energy of Needle Beams are both able to penetrate Screens with no degradation of their damage effects.
In general, Escort classes of ships will NOT carry screens; the generators are very bulky, expensive and require large amounts of power - it is theoretically possible to fit one on, say, a Frigate hull, but there will be virtually no pay load or power capacity left for any weaponry!
Most Cruiser-size hulls will mount Level-1 Screens, and Capital classes often carry Level-2 or 3 depending on their overall mass.
When constructing your own ships using the Design rules, you may add Screens or not. as you wish, provided you are willing to use up the MASS they require and pay the Points cost.
Threshold points and specific systems damage
As a ship takes damage from incoming fire,there is a chance that some of the ship's specific systems (Drives, weapons etc.) will be damaged or destroyed.
To avoid having to roll for possible 'critical hits' every time damage is inflicted we instead use the idea of 'Threshold Points' at which the players will check to see if each system on the ship is still functioning. A Threshold Point occurs each time the accumulated damage points reach (or pass) the end of one row of boxes on the ship's Damage Track. At this point,the player must roll one die for each system on his ship (except any already destroyed); the system rolled for is 'lost' (and crossed out on his ship diagram) in the following circumstances:
At the FIRST Threshold Point (ie: the end of the first row of damage boxes), any system for which a 6 is rolled is knocked-out.
At the SECONDThreshold Point (the end of the second line of boxes), a system is lost on a roll of 5 or 6.
At the THIRD point, a roll of 4,5 and 6 destroys a system.
The key issues I have with these are that they don't block torpedos as they clearly do in Star Trek where they are forcefields.
Screens in Fleet Book (FB)
No real changes just some mass changes and limitations based on hull sizes.
Energy screens, which protect against beam weapons fire and some other kinds of damage, require 5% of the ship’s MASS for a level-1 Screen system, and 10% for a level-2 Screen, but with MINIMUM requirements of 3 MASS for level-1 and 6 MASS for level-2 screens; thus any ship up to MASS 60 requires 3 MASS spare to install a level-1 screen system, while larger ships require 5% of their total MASS. Apart from any limitations described in the rules for specific weapon systems, screens work exactly as their counterparts in the original FT rules. IMPORTANT NOTE: THERE ARE NO LEVEL-3 SCREENS UNDER THE NEW DESIGN SYSTEM - additional screen generators above two may be purchased and installed if desired (at 5% of ship MASS each), but will NOT be of use except as back-ups to bring online if one of the main screens is lost through damage.
So the fundamental problems from the last version still exists for Star Trek shields.
Screens in Warlords (FTW) pp 22
Similar issues although they do block plasma weapons and explosions as well as beams they do not pass the Undiscovered Country test.
Screens (1 technology slot) Screens are thick webs of electromagnetic energy that surround the ship and divert incoming beam attacks. Screens have a mass of 5% of the ship's total mass per level. A ship can have 1 or 2 levels of screens. Unless otherwise specified, screens affect all beam attacks. Beam attacks use BD* to deliver damage. Screens also reduce the damage from plasma weapons (both plasma cannon and plasma bolts), reducing the damage per plasma die rolled by the level of shield, and they reduce the damage from nearby antimatter explosions. Shields have no effect on projectile-type weapons.
Screens in Remixed (RX) pp 13
Similar issues although they do block plasma weapons and explosions as well as beams they do not pass the Undiscovered Country test.
Screens in Cross Dimensions (XD) pp 19
Finally in Cross Dimensions we have advanced screens, these are much more like it.
Advanced screens not only protect against beam weapons, but also against torpedoes, missiles, and other weapons that normally ignore screens. Beams, grasers, fighters, and other weapons that are affected by standard screens are affected in the same way when attacking a ship with advanced screens.
SMPs and similar weapons that ignore standard screens and roll a combined hit and damage D6 are affected by advanced screens as if they were beams. Against level-1 advanced screens a roll of 5 inflicts 1 damage point, 6 inflicts 2. Against level-2 advanced screens a roll of 5 or 6 inflicts 1 damage point.
Torpedoes, missiles, and other weapons that are unaffected by standard screens and roll one or more D6 for damage subtract 1 from each damage die against level-1 advanced screens. Against level-2 advanced screens, subtract 2 from each die. (Negative damage is treated as zero: the target ship cannot regain damage points!)
A ship cannot be fitted with both advanced and standard screens, as they are assumed to represent different types of technology.
As with standard screens, a ship cannot have an advanced screen level greater than 2, even if it has additional generators.
As SMPs aren't a trek weapon we can ignore that. The rules for beams (phasers) and missiles (photons, plasma) look reasonable. A ship being pelted with torpedoes will start to get leaky screens on a roll of 6. Most medium and up StarTrek ships will have level 2 advanced screens as standard.
Shields in Project Continuum (PC) pp 56
These are advanced screens from XD with a high costs, probably too high for a Star Trek background. a level 2 screens would be 15% of mass, we will need to see if these costs work out for the baseline Star Trek Ships.
Advanced Screens mass 7.5% of the total ship mass per level with no minimum mass requirement.
Other systems considered
The other obvious defensive system to use for shields is armour. For this to behave like Star Trek then it would have to not follow the penetrating weapon rule till say it was at 50% rounded down. This would well simulate leaky shields as they drop to 50% and behave as they did in Undiscovered Country or DS9. Armours costs 1 mass per point.
Continuum also has regenerative armour pp 57 which is regnerated at the end of each turn
During the End Phase roll a d6 for each point of Regenerative Armor that has been damaged. On a 5 or 6 the armor box is repaired. On a 1 the armor has sustained too much damage and it cannot regenerate further this battle.
This does seem shield like but means a lot of extra rolling so probably not worth the complexity.
The other use of armour would be to call it shield reinforcement, this could be available for ships that have it and allow the normal advanced shields to be even more resilient.
So we could create a shields system, that costs 1 mass per point of defence, when you get to 50% it starts to leak to penetrating fire and there could be a percentage of reinforcement boxes that have a lower cost (50% rounded down) and are a percentage of the total shields the ship has (50% round up) . For example a cruiser mass X could have 10 shields and 5 reinforcements for a total of 15 and a costs of 10 X 1 + 2.
This could take two maximum yield hits from a photon/pulse torpedo and still be up, just.