Sensor Ranges in CT

[robject]

I've forgotten them, or don't know them, or they're not there.

Ordinary ships can track bogeys up to six light-seconds away, after an initial lock. Is that correct?

Well, what's the maximum detection range?

How about for ship's boats?

How about for initial detection, rather than tracking?

 

[robject]

I've forgotten them, or don't know them, or they're not there.

Ordinary ships can track bogeys up to six light-seconds away, after an initial lock. Is that correct?

Well, what's the maximum detection range?

How about for ship's boats?

How about for initial detection, rather than tracking?

 

[Black Globe Generator]

LBB 2, page 32: sensor range for commercial and private starships is one-half light-second - sensor range for scout and military starships is two light-seconds. Starships maintaining "complete silence"* can only be detected at one-half range (e.g., one-quarter light-second for a merchant ship); ships in orbit and "silent" can only be detected at one-eighth range.

Once a ship has been detected, it can be tracked by any starship at ranges of up to three light-seconds.

Edit: I believe the same holds true for ship's boats as well - I didn't see anything to the contrary.

* Presumably "complete silence" in this case refers to running in a very low- or no-power mode, given that in space, no one can hear you scream...or anything else, for that matter.

 

[Black Globe Generator]

LBB 2, page 32: sensor range for commercial and private starships is one-half light-second - sensor range for scout and military starships is two light-seconds. Starships maintaining "complete silence"* can only be detected at one-half range (e.g., one-quarter light-second for a merchant ship); ships in orbit and "silent" can only be detected at one-eighth range.

Once a ship has been detected, it can be tracked by any starship at ranges of up to three light-seconds.

Edit: I believe the same holds true for ship's boats as well - I didn't see anything to the contrary.

* Presumably "complete silence" in this case refers to running in a very low- or no-power mode, given that in space, no one can hear you scream...or anything else, for that matter.

 

[mike wightman]

Note that these ranges are at odds with Mayday, and the Mayday/High Guard crossover rules in Mayday.

In Mayday each hex is a light second and ships can be detected at any range.

In M/HG rules ships are at short range if within 5 light seconds, within less than 15 light seconds is long range, beyond this is out of range but the ships can still see each other on the hex map.

 

[mike wightman]

Note that these ranges are at odds with Mayday, and the Mayday/High Guard crossover rules in Mayday.

In Mayday each hex is a light second and ships can be detected at any range.

In M/HG rules ships are at short range if within 5 light seconds, within less than 15 light seconds is long range, beyond this is out of range but the ships can still see each other on the hex map.

 

[robject]

Thank you.

 

[robject]

Thank you.

 

[Supplement Four]

Interesting you post this topic now, Robject. I've been (just over the last two days) looking at different sensor rules to use in my CT game.

Everything I've seen so far is so complicated. I want to put a sensor roll into the mix, but all I really want is the Navigator to roll a sensor scan, and then have a different roll for a sensor lock (a lock required before a bogey can be targeted).

I've looked at Mayday, High Guard, TNE, T4, MT, Bruce M's sensor rules...and a few other house rules.

Again, everything is so doggone complicated. I don't want half the starship combat encounter to be about figuring sensor DMs.

Anybody got some good rules for using sensors with CT?


(Also--
I've been looking at the various starship combat systems too: Mayday, High Guard, etc.

I like the standard CT method best--I think that's what I'm going to use in my game (although I may use the Starter Traveller version that uses range bands....or I might make the range bands hexes).

 

[Supplement Four]

Interesting you post this topic now, Robject. I've been (just over the last two days) looking at different sensor rules to use in my CT game.

Everything I've seen so far is so complicated. I want to put a sensor roll into the mix, but all I really want is the Navigator to roll a sensor scan, and then have a different roll for a sensor lock (a lock required before a bogey can be targeted).

I've looked at Mayday, High Guard, TNE, T4, MT, Bruce M's sensor rules...and a few other house rules.

Again, everything is so doggone complicated. I don't want half the starship combat encounter to be about figuring sensor DMs.

Anybody got some good rules for using sensors with CT?


(Also--
I've been looking at the various starship combat systems too: Mayday, High Guard, etc.

I like the standard CT method best--I think that's what I'm going to use in my game (although I may use the Starter Traveller version that uses range bands....or I might make the range bands hexes).

 

[Black Globe Generator]

Originally posted by WJP:
I've looked at Mayday, High Guard, TNE, T4, MT, Bruce M's sensor rules...and a few other house rules.

To further complicate the picture, there are also the sensor rules in Grand Survey - these can be as detailed or as simple as the referee wants them to be (single roll, or multiple checks using different settings, for example).

 

[Black Globe Generator]

Originally posted by WJP:
I've looked at Mayday, High Guard, TNE, T4, MT, Bruce M's sensor rules...and a few other house rules.

To further complicate the picture, there are also the sensor rules in Grand Survey - these can be as detailed or as simple as the referee wants them to be (single roll, or multiple checks using different settings, for example).

 

[mike wightman]

Here's a compilation of some stuff from a while ago:

Assume military sensors are TL15, model 9, while civilian sensors are TL8, model 1. Add the two numbers together.

8+1=9 which = range of 0.5 light seconds

15+9=24 which = range of 2.0 light seconds

Therefore add 0.1 light seconds range per TL above 8 or per model above 1.

Sensor model is equal to computer model.

The ranges above are for active scans. Passive scans have a quarter of the above range.

Ships have a passive (radiated) signature equal to half of the power plant number (round down) or the maneuver rating used during that turn.

Planetoid hulls reduce the radiated signature due to the power plant by 1; buffered planetoids reduce it by 2. This reduction is not applied to the signature due to maneuvering.

The ship's passive signature is multiplied by 0.25 light seconds and subtracted from its range to decide if it is within the sensor range of a scanning vessel.
e.g. a ship with a passive signature of +3 is detected if it moves to within 1.25 light seconds of a ship with military sensors (TL15, model 9).

Ships have a reflected signature based on hull size (and configuration USP):
less than 100t, -1
100t-999t, +0
1000t+, +1
5000t+, +2

USP
1-3, +0
4-6, +1
7-9, +2

The ship's reflected signature is multiplied by 0.25 light seconds and subtracted from its range to decide if it is within the active sensor range of a scanning vessel,

e.g. a ship with a reflected signature of +1 is detected if it moves to within 2.25 light seconds of a ship with military sensors (TL15, model 9).

Once a ship has been detected it can be tracked out to 3 light seconds, but once it moves beyond the sensor's auto spot range (modified by target signature) then a roll of 8 or more on 2d is required to maintain the target lock.

DMs:
+ signature for the sensor type
+ gunnery skill (or navigation -1)
- 1 per 0.25 light seconds outside auto spot range.

Notes:
these rules are based on the Traveller 2300 game Star Cruiser.
If you want to play cat and mouse then I would recommend changing the scale of LBB2 combat to 30cm = 1 light second, it fits better on a table top
1 G maneuver changes vector by 1cm.
laser to hit range modifiers become:
25cm+, -2
50cm+, -5
75cm+, -8

Active sensor jamming
A ship inside the active sensor range of an opponent may try to fool his active scans by running the ECM program. This actually consists of broadcasting false returns etc. using their own active sensor.

The attacking ship has to roll 12+ to obtain a sensor lock.
DMs:
+ 1 per level of gunnery skill (or navigation -1)
+ targets reflected signature
+/- 1 per relative TL
+/- 1 per relative computer model

If the attacking ship runs its own ECM program in ECCM mode then it gains a bonus of +4 to the roll to obtain a sensor lock.

Sensor Drones
A sensor drone is a specially modified missile with its warhead removed (or downgraded) and an active/passive sensor system installed. It maneuvers the same as a normal missile.
The drone’s sensors have half the range of the equivalent ship mounted sensors, and the drone can only go active a limited number of times depending on TL. The TL also determines the maximum model of sensor that can be installed. If the drone does not use its maneuver drive it may deploy a folding array to increase its sensor range to the same as that of an equivalent ship mounted system.

Number of active scans equals TL/3 round down.
Maximum sensor model equals TL/5 round down.

Sensor Decoy Drones
These are missiles that are modified to exactly mimic the passive and reflective signatures of the launching ship.
Their warhead is removed and replaced with extendable radiator panels and vanes that are designed to radiate the same heat signature and provide the same target profile as the reflected signature of the launching ship.

Once launched the drone(s) and the ship should be replaced with identical counters. Each then maneuvers separately and provides a problem for the attacking ship.

To identify a bogey as a drone or the ship roll 10+ on 2d.

DMs:
+/- 1 per relative TL
+ 1 per level of gunnery skill (or navigation -1)

Alternatively, just shoot them all the decoy can only take one hit.

Area Jammer Drone
this is a missile modified to transmit as much white noise as possible to confuse active sensors. If the line of sight to a target passes within 0.1 light seconds of the drone then the active ship must roll to penetrate ECM as for active jamming, above.

If the target ship is also using ECM jamming then the active ship must make two roles to obtain a target lock.

 

[mike wightman]

Here's a compilation of some stuff from a while ago:

Assume military sensors are TL15, model 9, while civilian sensors are TL8, model 1. Add the two numbers together.

8+1=9 which = range of 0.5 light seconds

15+9=24 which = range of 2.0 light seconds

Therefore add 0.1 light seconds range per TL above 8 or per model above 1.

Sensor model is equal to computer model.

The ranges above are for active scans. Passive scans have a quarter of the above range.

Ships have a passive (radiated) signature equal to half of the power plant number (round down) or the maneuver rating used during that turn.

Planetoid hulls reduce the radiated signature due to the power plant by 1; buffered planetoids reduce it by 2. This reduction is not applied to the signature due to maneuvering.

The ship's passive signature is multiplied by 0.25 light seconds and subtracted from its range to decide if it is within the sensor range of a scanning vessel.
e.g. a ship with a passive signature of +3 is detected if it moves to within 1.25 light seconds of a ship with military sensors (TL15, model 9).

Ships have a reflected signature based on hull size (and configuration USP):
less than 100t, -1
100t-999t, +0
1000t+, +1
5000t+, +2

USP
1-3, +0
4-6, +1
7-9, +2

The ship's reflected signature is multiplied by 0.25 light seconds and subtracted from its range to decide if it is within the active sensor range of a scanning vessel,

e.g. a ship with a reflected signature of +1 is detected if it moves to within 2.25 light seconds of a ship with military sensors (TL15, model 9).

Once a ship has been detected it can be tracked out to 3 light seconds, but once it moves beyond the sensor's auto spot range (modified by target signature) then a roll of 8 or more on 2d is required to maintain the target lock.

DMs:
+ signature for the sensor type
+ gunnery skill (or navigation -1)
- 1 per 0.25 light seconds outside auto spot range.

Notes:
these rules are based on the Traveller 2300 game Star Cruiser.
If you want to play cat and mouse then I would recommend changing the scale of LBB2 combat to 30cm = 1 light second, it fits better on a table top
1 G maneuver changes vector by 1cm.
laser to hit range modifiers become:
25cm+, -2
50cm+, -5
75cm+, -8

Active sensor jamming
A ship inside the active sensor range of an opponent may try to fool his active scans by running the ECM program. This actually consists of broadcasting false returns etc. using their own active sensor.

The attacking ship has to roll 12+ to obtain a sensor lock.
DMs:
+ 1 per level of gunnery skill (or navigation -1)
+ targets reflected signature
+/- 1 per relative TL
+/- 1 per relative computer model

If the attacking ship runs its own ECM program in ECCM mode then it gains a bonus of +4 to the roll to obtain a sensor lock.

Sensor Drones
A sensor drone is a specially modified missile with its warhead removed (or downgraded) and an active/passive sensor system installed. It maneuvers the same as a normal missile.
The drone’s sensors have half the range of the equivalent ship mounted sensors, and the drone can only go active a limited number of times depending on TL. The TL also determines the maximum model of sensor that can be installed. If the drone does not use its maneuver drive it may deploy a folding array to increase its sensor range to the same as that of an equivalent ship mounted system.

Number of active scans equals TL/3 round down.
Maximum sensor model equals TL/5 round down.

Sensor Decoy Drones
These are missiles that are modified to exactly mimic the passive and reflective signatures of the launching ship.
Their warhead is removed and replaced with extendable radiator panels and vanes that are designed to radiate the same heat signature and provide the same target profile as the reflected signature of the launching ship.

Once launched the drone(s) and the ship should be replaced with identical counters. Each then maneuvers separately and provides a problem for the attacking ship.

To identify a bogey as a drone or the ship roll 10+ on 2d.

DMs:
+/- 1 per relative TL
+ 1 per level of gunnery skill (or navigation -1)

Alternatively, just shoot them all the decoy can only take one hit.

Area Jammer Drone
this is a missile modified to transmit as much white noise as possible to confuse active sensors. If the line of sight to a target passes within 0.1 light seconds of the drone then the active ship must roll to penetrate ECM as for active jamming, above.

If the target ship is also using ECM jamming then the active ship must make two roles to obtain a target lock.

 

[Supplement Four]

Originally posted by Black Globe Generator:
To further complicate the picture, there are also the sensor rules in Grand Survey - these can be as detailed or as simple as the referee wants them to be (single roll, or multiple checks using different settings, for example).

Yeah, I looked at those earlier tonight. I don't have Grand Survey, but I do have The World Builder's Handbook.

I like that stuff. DGP always writes the best Traveller stuff...they're even better than GDW.

I think I'm going to use a simplified version of what appears in the WBH. That way, I can focus on roleplaying.

"Your passive sensors are pinging! It's an energy sig, about 40,000 klicks out. IR readings are strong. There's something there, and it's moving towards you. Do you want to use the LADAR?"

"Yes."

(Player playing the Navigator makes a sensor ops roll....)

"Two more bogeys! They're small. Alarm! They're two small! Your guess is that the unidentifed bogey just fired missiles!"

"Sesors go active! Let's get a firing solution!"


....stuff like that. That's how I want ship combat to go.


I think I'm going to distill some details from MT down about sensors, then use the method presented in the WBH. I think that will be fun--it'll be more of a role-play simulation than simple dicing game (dicing just for the sake of dicing is never fun).

But, I think I can make a simple set of two types of rolls (passive and active scans...or passive and active pinpoints) but make it seem more complicated to the players than it actually is.

There will be the two basic rolls, but description about types of sensor being used and feedback from what is sensed will make the two rolls more involving.

I notice that there is jamming in MT too, but I haven't seen anything about how jammers work mechanically.

I'm thinking of having the jamming ship roll a task, and whatever the total, that will be the target number for an opponent ship to break through the jamming.

I also thought that I'd require a pinpoint scan (a target lock) before an enemy can be attacked. But, a successful jam will break a lock (requiring the ship to attempt a lock again).

I think it was in Brilliant Lances that a sensor scan took the place of one turret firing (because scanning and intrepreting data takes time).

I kinda like that rule: If you take a scan, you'll have to give up one of the turrets on your ship firing during the round.

I'm going to use regular CT starship combat--that system is just "fun" (I've used it before), and you can play it on a hex board if you want to--or you can play it more like High Guard, keeping track of range bands in your GM's notebook and describing the action to the players.

I like that flexibility.

Plus, it gives all the major crew positions something to do.

The player playing the Pilot moves the counter around on the hex board, and his skill is used as a defensive DM if the correct computer program is running. That makes him important.

The Navigator will roll sensor scans and locks--decide which sensors to use. Without a lock, a target cannot be fired upon. He'll also roll jamming throws. And, that will make that character important.

I'm going to fudge the 1000 second combat round a bit, making it 15 minutes instead of 16.67 minutes. That will add some symmetry to the 15 second personal combat round and the 15 minute space combat round.

If the ship is hit and damaged, the player playing the engineer will have plenty to do...making damage repair rolls.

If a crew member is hurt when the ship takes damage, then the medic will have some rolls to make.

And the gunner will, of course, make the to-hit throws.


I think what I'm going to do is pull out my big cork board and thumb-tack on the large 15mm deckplans for the ship. This way, the focus of the game will be what goes on inside the ship. It will be there in front of the players. We can move counters around on the deck plans, when necessary, to see where everyone is (I'd do this more to focus the attention of the group inside the ship than anything else).

I can use my small Mayday counters and map as a the pilot's holotank--he'll be able to see spatial distances.

But, for the most part, I think I'll just describe what happens and role-play the space encounter.

These new sensor rules are going to help.

 

[Supplement Four]

Originally posted by Black Globe Generator:
To further complicate the picture, there are also the sensor rules in Grand Survey - these can be as detailed or as simple as the referee wants them to be (single roll, or multiple checks using different settings, for example).

Yeah, I looked at those earlier tonight. I don't have Grand Survey, but I do have The World Builder's Handbook.

I like that stuff. DGP always writes the best Traveller stuff...they're even better than GDW.

I think I'm going to use a simplified version of what appears in the WBH. That way, I can focus on roleplaying.

"Your passive sensors are pinging! It's an energy sig, about 40,000 klicks out. IR readings are strong. There's something there, and it's moving towards you. Do you want to use the LADAR?"

"Yes."

(Player playing the Navigator makes a sensor ops roll....)

"Two more bogeys! They're small. Alarm! They're two small! Your guess is that the unidentifed bogey just fired missiles!"

"Sesors go active! Let's get a firing solution!"


....stuff like that. That's how I want ship combat to go.


I think I'm going to distill some details from MT down about sensors, then use the method presented in the WBH. I think that will be fun--it'll be more of a role-play simulation than simple dicing game (dicing just for the sake of dicing is never fun).

But, I think I can make a simple set of two types of rolls (passive and active scans...or passive and active pinpoints) but make it seem more complicated to the players than it actually is.

There will be the two basic rolls, but description about types of sensor being used and feedback from what is sensed will make the two rolls more involving.

I notice that there is jamming in MT too, but I haven't seen anything about how jammers work mechanically.

I'm thinking of having the jamming ship roll a task, and whatever the total, that will be the target number for an opponent ship to break through the jamming.

I also thought that I'd require a pinpoint scan (a target lock) before an enemy can be attacked. But, a successful jam will break a lock (requiring the ship to attempt a lock again).

I think it was in Brilliant Lances that a sensor scan took the place of one turret firing (because scanning and intrepreting data takes time).

I kinda like that rule: If you take a scan, you'll have to give up one of the turrets on your ship firing during the round.

I'm going to use regular CT starship combat--that system is just "fun" (I've used it before), and you can play it on a hex board if you want to--or you can play it more like High Guard, keeping track of range bands in your GM's notebook and describing the action to the players.

I like that flexibility.

Plus, it gives all the major crew positions something to do.

The player playing the Pilot moves the counter around on the hex board, and his skill is used as a defensive DM if the correct computer program is running. That makes him important.

The Navigator will roll sensor scans and locks--decide which sensors to use. Without a lock, a target cannot be fired upon. He'll also roll jamming throws. And, that will make that character important.

I'm going to fudge the 1000 second combat round a bit, making it 15 minutes instead of 16.67 minutes. That will add some symmetry to the 15 second personal combat round and the 15 minute space combat round.

If the ship is hit and damaged, the player playing the engineer will have plenty to do...making damage repair rolls.

If a crew member is hurt when the ship takes damage, then the medic will have some rolls to make.

And the gunner will, of course, make the to-hit throws.


I think what I'm going to do is pull out my big cork board and thumb-tack on the large 15mm deckplans for the ship. This way, the focus of the game will be what goes on inside the ship. It will be there in front of the players. We can move counters around on the deck plans, when necessary, to see where everyone is (I'd do this more to focus the attention of the group inside the ship than anything else).

I can use my small Mayday counters and map as a the pilot's holotank--he'll be able to see spatial distances.

But, for the most part, I think I'll just describe what happens and role-play the space encounter.

These new sensor rules are going to help.

 

[Supplement Four]

Originally posted by Sigg Oddra:
Here's a compilation of some stuff from a while ago:

Great stuff. I'm going to print it out and take a closer look.

Thanks, Sig.

I found some other cool sensor rules in a HIWG doc from 1997, written by Roger Myhre. I haven't read them all yet, but it looks like this guy took a distilled version of Brilliant Lances and added in his own know-how from being a sensor operator in the navy, to come up with some cool CT sensor rolls.

I'm going to peruse those as well. From just scanning them, I like what he's doing: simple 2D rolls with modifiers. It's very Classic Traveller.

 

[Supplement Four]

Originally posted by Sigg Oddra:
Here's a compilation of some stuff from a while ago:

Great stuff. I'm going to print it out and take a closer look.

Thanks, Sig.

I found some other cool sensor rules in a HIWG doc from 1997, written by Roger Myhre. I haven't read them all yet, but it looks like this guy took a distilled version of Brilliant Lances and added in his own know-how from being a sensor operator in the navy, to come up with some cool CT sensor rolls.

I'm going to peruse those as well. From just scanning them, I like what he's doing: simple 2D rolls with modifiers. It's very Classic Traveller.

 

[OIT]

Robject,

A variation of the rules quoted by Sigg Oddra is below:

Ships in space have four methods of detecting each other:

RF Passive – All military and scout* starships, non-starships, and small craft with computers. Range = tech + computer – 0.4 in light seconds. For example, a Type S Scout would have a passive detection range of 0.5 light seconds (150,000km or roughly 12 Terran planetary diameters) whereas a Kinunir Class cruiser would have a passive detection range of 2.0 light seconds (600,000km or about 50 Terran planetary diameters).
RF Active – All, civillian and military, starships, non-starships, and small craft with computers. Range is one-half passive range for an equivalent vessel.
Visual (actually includes Visual, IR, and MMW, but we’ll call it visual for simplicity sake) Passive – All starships, non-starships, and small craft. Range is one-eighth the passive range for an equivalent vessel. For example, a tech eight cutter with no computer would have a visual detection range of .05 light seconds (15,000km or a little over one Terran planetary diameter).
Transponder – All starships, non-starships, and small craft. Transponder range equals passive detection range.

* I define military and scout as ships with fib computers (allowing a grandfather clause for the Type S, M, T and Corsair type designs using Book 2 rules)

Detection Probabilities:

Passive – a ship using passive sensors automatically detects any target entering range if the target is broadcasting comms, using active sensors, or squawking transponders. If the target is not doing any of those things, then no detection.
Active – a ship using active sensors automatically detects any target entering range if the target is maneuvering (accelerating, decelerating, or changing course). If the target is non-maneuvering, detection roll is 8+, using Navigation and Pilot/2 (round fractions down) skills as modifiers. Some campaigns may also wish to allow the use of Commo skill as a DM, if for no other reason than to make that skill more useful. Additional modifiers such as speed of contact, debris level in a given system, location within the system, and course must be applied by the ref on a case-by-case basis.
Visual – detection automatic within range.
Transponder – detection automatic if both vessels are interrogating/squawking.

ECM: The ECM program listed in LBB 2 seems to indicate a low-power, Anti-Missile type capability (RGPO or some similar such technique). Unless the campaign is military oriented, or the referee wants additional complexity, other forms of EW can be ignored.

Tactical Implications:

TACSIT ONE
A Far Trader leaving the moon of a large gas giant suspects she may be interdicted enroute to jump point by a Corsair. She can either go straight out with sensors and transponders active (like she would normally), knowing she may be detected by the Corsair’s passive systems or she can go out quiet, knowing she be mostly blind (visual sensors only) and that, depending on the system, she may face fines at some point (failure to squawk transponder signal is a violation of Imperial safety of navigation regulations). As an alternative plan, she could select a less optimal course away from the moon, knowing that it will take longer to get away from the gravitational influence of the gas giant, but (depending on where the Corsair has chosen for an ambush point) maybe never entering sensor detection range of the Corsair. Tough calls for the players to make, each having advantages and disadvantages.

TACSIT TWO
A Corsair attempts to ambush a Far Trader leaving the inhabited moon of a gas giant. Depending on the system, the Corsair may be able to be bold or may have to be sneaky. If there are no local defense forces, the Corsair can stay close to the planet, use active sensors, and engage the Trader early. If there are System Defense Forces, the Corsair will have to try to avoid detection. If so, the Corsair faces the same dilemma as the Trader. Either stay closer to the planet using only passive sensors, knowing the Trader may slip past if she also goes quiet, or take position farther from the planet, use active sensors, and risk not finding the Trader if she departs by a round-about course. The Corsair may guess the Trader may take a different direction away from the planet, but which one?

TACSIT THREE
A tech level fifteen fleet tries to detect an invading force. Assuming the main body remains near the planet and scans actively, and assuming a Terra sized planet, achieving continuous passive sensor coverage of all approach angles out to one hundred and twenty five planetary diameters requires approximately twelve picket vessels. Using active sensors, the same twelve pickets could only cover out to seventy five planetary diameters. Either way, a large portion of the pickets may be out of position to intercept the invading force, reducing the number of ships the defending admiral can bring to bear. Also, assuming a high-G approach by the invaders, the fleet would have to be in a continuous state of readiness, difficult to sustain for prolonged periods in wartime and impossible during periods of peace.

When all is said and done, the sensor rules you employ IYTU will depend on the flavor of game you’re trying to achieve. Hopefully, though, the above ideas are useful in helping you craft a set of House Rules to fit your game.

Hope it helps.

 

[OIT]

Robject,

A variation of the rules quoted by Sigg Oddra is below:

Ships in space have four methods of detecting each other:

RF Passive – All military and scout* starships, non-starships, and small craft with computers. Range = tech + computer – 0.4 in light seconds. For example, a Type S Scout would have a passive detection range of 0.5 light seconds (150,000km or roughly 12 Terran planetary diameters) whereas a Kinunir Class cruiser would have a passive detection range of 2.0 light seconds (600,000km or about 50 Terran planetary diameters).
RF Active – All, civillian and military, starships, non-starships, and small craft with computers. Range is one-half passive range for an equivalent vessel.
Visual (actually includes Visual, IR, and MMW, but we’ll call it visual for simplicity sake) Passive – All starships, non-starships, and small craft. Range is one-eighth the passive range for an equivalent vessel. For example, a tech eight cutter with no computer would have a visual detection range of .05 light seconds (15,000km or a little over one Terran planetary diameter).
Transponder – All starships, non-starships, and small craft. Transponder range equals passive detection range.

* I define military and scout as ships with fib computers (allowing a grandfather clause for the Type S, M, T and Corsair type designs using Book 2 rules)

Detection Probabilities:

Passive – a ship using passive sensors automatically detects any target entering range if the target is broadcasting comms, using active sensors, or squawking transponders. If the target is not doing any of those things, then no detection.
Active – a ship using active sensors automatically detects any target entering range if the target is maneuvering (accelerating, decelerating, or changing course). If the target is non-maneuvering, detection roll is 8+, using Navigation and Pilot/2 (round fractions down) skills as modifiers. Some campaigns may also wish to allow the use of Commo skill as a DM, if for no other reason than to make that skill more useful. Additional modifiers such as speed of contact, debris level in a given system, location within the system, and course must be applied by the ref on a case-by-case basis.
Visual – detection automatic within range.
Transponder – detection automatic if both vessels are interrogating/squawking.

ECM: The ECM program listed in LBB 2 seems to indicate a low-power, Anti-Missile type capability (RGPO or some similar such technique). Unless the campaign is military oriented, or the referee wants additional complexity, other forms of EW can be ignored.

Tactical Implications:

TACSIT ONE
A Far Trader leaving the moon of a large gas giant suspects she may be interdicted enroute to jump point by a Corsair. She can either go straight out with sensors and transponders active (like she would normally), knowing she may be detected by the Corsair’s passive systems or she can go out quiet, knowing she be mostly blind (visual sensors only) and that, depending on the system, she may face fines at some point (failure to squawk transponder signal is a violation of Imperial safety of navigation regulations). As an alternative plan, she could select a less optimal course away from the moon, knowing that it will take longer to get away from the gravitational influence of the gas giant, but (depending on where the Corsair has chosen for an ambush point) maybe never entering sensor detection range of the Corsair. Tough calls for the players to make, each having advantages and disadvantages.

TACSIT TWO
A Corsair attempts to ambush a Far Trader leaving the inhabited moon of a gas giant. Depending on the system, the Corsair may be able to be bold or may have to be sneaky. If there are no local defense forces, the Corsair can stay close to the planet, use active sensors, and engage the Trader early. If there are System Defense Forces, the Corsair will have to try to avoid detection. If so, the Corsair faces the same dilemma as the Trader. Either stay closer to the planet using only passive sensors, knowing the Trader may slip past if she also goes quiet, or take position farther from the planet, use active sensors, and risk not finding the Trader if she departs by a round-about course. The Corsair may guess the Trader may take a different direction away from the planet, but which one?

TACSIT THREE
A tech level fifteen fleet tries to detect an invading force. Assuming the main body remains near the planet and scans actively, and assuming a Terra sized planet, achieving continuous passive sensor coverage of all approach angles out to one hundred and twenty five planetary diameters requires approximately twelve picket vessels. Using active sensors, the same twelve pickets could only cover out to seventy five planetary diameters. Either way, a large portion of the pickets may be out of position to intercept the invading force, reducing the number of ships the defending admiral can bring to bear. Also, assuming a high-G approach by the invaders, the fleet would have to be in a continuous state of readiness, difficult to sustain for prolonged periods in wartime and impossible during periods of peace.

When all is said and done, the sensor rules you employ IYTU will depend on the flavor of game you’re trying to achieve. Hopefully, though, the above ideas are useful in helping you craft a set of House Rules to fit your game.

Hope it helps.