Realistic Sensor Rules

[CRMcNeill]

Maybe. We don't have a clear enough idea of how shields work to say what they may or may not give off. Personally, I like the idea of the characters having to choose between shields and stealth.
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"No set of rules can cover every situation. It's expected that you will make up new rules to suit the needs of your game." - The Star Wars Roleplaying Game, 2R&E, pg. 69, WEG, 1996.

The CRMcNeill Stat/Rule Index

[Fallon Kell]

Regardless of how we derive the sensor signature code, how should we use it?
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Or that excessively long "Noooooooooo" was the Whining Side of the Force leaving him. - Dustflier

Complete Starship Construction System

[atgxtg]

Since Ray shields are supposed to absorb radiation, it would seem likely that they would "soak up" sensors. Kinda like radar absorbing material.
But the particle shields are another story.

But SW ships might have massive energy signatures (or not, depending on how well shielded the frames are). Apparently, the hotrod airspeeder than Anakin commandeered in AOTC has a 30 MW power generator. Thats about 100-160 times the power of a modern hot rod, or about 15% more powerful than the reactor on a Los Angeles class submarine. The spacecraft produce huge amounts of power (an ISD-1 has an output of 7.73 yottawatts, that's 7730000000000000000 mega-watts!).

[Fallon Kell]

[vanir]

I did fairly roughly write up a sensors installation descript and pricing for another browser and upload it on pdf
Just a basic conversion of existing RPG sensor system to a more analoguous description of real world technical sensor systems.

It's here Sensors description and pricing PDF

Stealth features aren't discussed as these are again really more a case of nomenclature in SWU. Sensor baffling is essentially what you do to conceal the compressor blades in the F-22 by making indirect intake tunnels. Angular construction like the F-117 is another example, or the grilles over its intakes, or the heat baffling of the exhaust jet piping.

It essentially lowers the sensor signature of the class of vessel, so a fighter looks like a bird, a bomber looks like a fighter, etc. This reduces detection range which is in part governed by the strength of return signal.
In game, since dice are used as detection power, counter/difficulty dice are an effective representation of reduced radar signature. I use ratings of 1D, 2D or 3D depending how extensive the baffling, 3D representing a fully engineered design like the F-117 in a starship, 2D representing good modifications to an existing design like the X-Wing Stealth, and 1D representing some simple modifications a PC might do to a tramp freighter, like just good sensor baffling of the engines to make it look more like a small shuttle to an ISD bridge crew that isn't really looking that hard.
In addition all other bonuses and difficulty increases should be exercised when a pilot is purposely evading sensors. If an experienced pilot is just plain trying to avoid making a big sensor signature out of his ship by the way he flies it, I straight up raise the sensor difficulties one level in his favour as a base, before any equipment modifiers. IRL it actually does work that way, with notching, using signal noise, hiding among clutter, turning the ship to mess up his doppler effect, all sorts of little tricks.

Even if the ship is detected, the difficulty increase of baffling should still apply to identify the class and type of craft, so even if you see it, you might think it is a harmless little communications satellite instead of a big military corvette targeting you on a passive array.
Another point is that because targeting systems are sensor dependent, sensor baffling should also apply as a penalty to the fire control to target the craft. Not only do you have to see it to shoot at it, but even if you see it, you have to be much closer to get any kind of target lock on it, and this is the real value of stealth technology like the F-22 in modern air combat. It's not being hard to find (after all you can clearly see its radar emissions), it's needing to be so close to fire a missile at it, that it's definitely already had plenty of shots at you first.


Sensor masking sounds more like absorptive features like the radar absorptive paint/construction on the Blackbirds and B-2 Spirit, which is a little different to baffling. This is generally much harder to detect, but if you do there's no penalty to identify, nor is it any harder to lock it up on fire control if you've got a sensor reading. Obviously the main value of this system is not being seen.

Due to its nature I think this kind of sensor countermeasures works best with a flat rate of difficulty modifier, like say, an increase of one level of difficulty to detect for radar absorptive coating, like a Blackbird. For dedicated, radar absorptive construction materials and internal structure as well as exterior coating you could be looking at double all difficulties to detect, or a +20 difficulty or something like that.

The trick with radar absorptive coating however is that it wears off, quickly and it's expensive. The B-2 isn't used very often for this reason, mission cost due to maintenance of its stealth qualities is extremely high, B-1B pulled out of reserve are preferred unless a high value target.
So whilst the benefits of dedicated Sensor Masking are high, increase Starport maintenance fees to keep the craft in tip top shape and of course you'll want permits for it. By default it's a military item.


Jamming equipment and ECM are another topic. These can be quite sophisticated, but can work into the game fairly simply.

[Fallon Kell]

[vanir]

The Fabritech Vanish2 Sensor Mask adds difficulty to detect and identify.
Meanwhile the Arakyd NightShadow Sensor Baffling adds difficulty to detect only.

I'm proposing a revision, so that sensor masks are stealth technology (detection but not identify or fire control once detected), and sensor baffling is high survivability technology (detect, identify and fire control difficulties). This would match real world nomenclature for how the technology proposal works better.

Of course the best starships would have both, and bonus dice should compound. So that 2D baffling and 2D masking (a purpose built stealth craft) gives you: -4D to detect, -2D to identify if detected and -2D to enemy fire control sets under all conditions (sensor jamming enemy fire control would be an either/or arrangement and not cumulative with this).
A player modified ship, with very expensive 2D sensor masking installation (coated hull, changed hull plating materials, effectively double coating of sensor absorptive 'stuff'), but the structure itself hasn't been completely re-engineered in shape and design (baffling/dispersion of signal returns) so his limit here is about 1D sensor baffling (say, just baffling the engines/power emissions as best you can), gets -3D to detect (pretty strong), -1D to identify (could combine with some con skill to misrepresent himself over the comms to customs craft), and -1D enemy fire control (pretty good for a garage modification).

House rules proposal.

Our house rule is also that you must establish a successful sensors action on an enemy craft to use fire control in the first place, or target him beyond short range (ie. at BVR). At short range or less you can fire over open sights, without fire control bonus but don't need a sensors lock (may need a Per/Search roll to find him though). At BVR, or medium and long range with a given weapon, you need computerised targeting and sensors data to fire on an enemy, to even know there's one out there.

So sensors countermeasures gets more important in our game. You might not see a TIE until he is within 3 spaces from you. If you don't use your sensors sweeps and organise your squadron to overlap fields of view, maintain combat protocols in enemy territory, that's exactly what does happen.
Of course I don't tell the players a TIE suddenly appears 2 spaces away before their free Per roll successfully saw it because they were too busy yacking about astronaut food, players love metagaming too much and you shouldn't tell them things in game mechanics. I tell them by description. So you're busy having a conversation, you haven't been doing your sensors sweeps, and suddenly you catch a glimpse of something very small and fast moving, just barely reflecting a bit of starlight, in the extreme distance out of the corner of your eye.

Given the speeds of starships, space units are actually tremendous distances, ostensibly thousands of sq. km. So only a few space units should be pretty much the limit of unaided vision.
Adds another dimension to starship combat, more like a simulator style rendition. But that's up to individual gaming style. We like this.

[CRMcNeill]

[Raven Redstar]

By adding codes to existing sensor bonuses and skill, you are opening up the possibility that you can put a nincompoop at the sensor station and they do a good job.

Or were you planning on getting rid of the existing bonuses from sensor suites?
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RR
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[CRMcNeill]

[CRMcNeill]

[vanir]

Given sensor signature will vary by the type of sensors being employed to detect, eg. a signal return cross section (using active sensors) will be hull dependent, an electroptical signature (using passive sensors) will be power dependent.

Then you could do modifiers based on the class of sensors used to be more conditional, rather than sweeping modifiers used in the RAW.

Passive sensors could have a base dependent on the class of power output. Passive sensors are tachyon interception, RWR antennae and electroptical windows, they respond to radiation and other emissions (including enemy active sensor emissions).

First thing they teach fighter pilots in military is your radar range of emissions is twice as far as the range to pick up a signal return (eg. a 100km detect range means an enemy RWR alarm goes off at 200km from you), so an enemy will always see you before you see him whenever you do a radar sweep. Bugging the enemy with your radar emissions is also used as a combat tactic, if you want to get an enemy to react just paint him with your radar especially in fire control mode (specific tracking frequency goes off to RWR as a missile launch), often they panic. Eagle pilots have used this technique during BFM to distract Iraq pilots enough to have them crash their bird into the ground (one combat record is this instance with an F1 Mirage buzzing an EF-111 Raven when an Eagle top cover came down and scared the pants off the Mirage by locking him up on track/fire control, it promptly crashed when the pilot panicked). So this is another point about your passive sensors.

Note:
A general House rule we tossed in without really thinking about it was to increase the sensor range per round, so that sensor range is the range of sensor return within a combat round, after two rounds sensor emissions have travelled twice as far and so on, so that spending an hour could allow you to sweep an entire system from the orbit of a planet, due to such physics-bending technology as tachyon collectors and so forth.
If an X-Wing pilot spends 10 combat rounds performing a dedicated sensor search in a single direction, he gets a sensor return from 750 space units away.

Some House rules for passive sensors could be...

Double passive sensor range if the enemy craft is using active sensors in the round.
Base difficulty to detect moderate, to identify very difficult (unchanged)
+10 to detect and identify if the enemy craft is a capital scale vessel
+5 to detect if the craft is capital scale and moves more than 6 space units in a round (due to power output).
+5 to detect if the craft is starfighter scale and moves more than 10 space units in a round (due to power output).
+30 to detect if the enemy declares a shot at you (irrespective of round sequence or initiative for the round)
+10 to detect and identify if enemy deflector shields are in use

Active sensors combine passive arrays with active sensor emissions and computer analyzed signal return processing, mode dependent but includes functions of the fire control computer. Some House rules could be...

You cannot perform a focus heavy scan and fire your weapons in the same round due to functionality of the fire control system. You can use the scan and search functions (or passive) but not focus if you fire weapons in the round.
Scan uses a digitally phased array, which uses the hull of your craft as part of the signal antennae (some modern aircraft do this). This limits range but looks all around the craft for a total view of the combat environment, it is tied into the fire control computer. You cannot perform system sweeps or dedicated sensor searches using this mode. In game terms the maximum limit of effectively processing signal returns is a two-round emission, or double the listed scan range over two combat rounds. This means you can scan the listed scan range in one combat round, double the listed range if you spend two rounds and this is the maximum before signal clutter and data handling overwhelms conceivable processing ability.

Base scan difficulty to detect easy, to identify moderate (unchanged)
+5 to detect and identify if the enemy craft is a capital scale vessel (due to power output/signature).
+5 to detect if enemy craft is larger than 100m in size.
+10 to detect if enemy craft is larger than 500m in size.
+15 to detect if enemy craft is larger than 1km in size.
+5 to detect and identify if enemy deflector shields are in use.
+10 to detect if enemy craft moves more than 7 space units in a round (if threat analysis grid is equipped, which most combat craft like starfighters feature, notable exceptions are scouting vessels and stock transports).

[vanir]

[CRMcNeill]

Ideally, I'd like to see the sensor ranges in existing stats given range brackets, like weapons. Since sensors are relatively uniform, converting existing ranges could use a simple formula, like x.1 - x.25 / x.5 / x1, so that an Imperial Star Destroyer's Sensor stats would read:

Passive: 5-12/25/50 @ 1D
Scan: 10-25/50/100 @ 3D
Search: 20-50/100/200 @ 4D

The basic Difficulty for the Sensors skill would increase with the range bracket, but the sensor signature rating of the target would also be subtracted from the Difficulty. Alternately, if this seems to cap ranges and detection rates too close, a larger conversion formula could be used, such as x.2 - x.5 / x1 / x2

In such a system, I'm also debating whether to keeping Focus as is, or to change the number before Focus to mean the total number of individual objects that the ship can Focus on simultaneously...
_________________
"No set of rules can cover every situation. It's expected that you will make up new rules to suit the needs of your game." - The Star Wars Roleplaying Game, 2R&E, pg. 69, WEG, 1996.

The CRMcNeill Stat/Rule Index

[vanir]

Hey I like that idea, rolled into all the other additions in our game of course and analoguous to the listed base difficulties to detect, so that...

the ISD categories should go..

passive 0-25/50/100 (as moderate is the 1:1 ratio by default to detect)
scan 1-100/150/200 (as easy is the 1:1 ratio to detect)
search 10-200/300/400 (as easy is the 1:1 ratio for listed range)

and minimum range is the range below which sensors are ineffective, so that hovering point blank over the hull of a vessel leaves you registering only to its passive sensors (can be handled by running silent, like the Falcon in ESB).