T4 Only: Some people say no stealth in space, a discussion.

[mike wightman]

Every escort class ship and every small craft sensor picket is going to have the same sensor capability as the capital ships at a minimum, with capital ships having multiple onboard sensors available.

You are going to have so many ship scanning the sky that a complete survey is achieved in minutes. Thereafter you can focus the capital ship sensors on the threats while the escorts continue to sweep. It is probably the best thing you can do with heavy fighters

 

[warwizard]

Well as Traveller is not restricted to the third Imperium we can chose to play in different eras. Go back to the first scouts of the valani or the Syleans. No longer do we have the assumptions that "we have been doing this for 10,000 years", everything is new. I myself perfer to play the explore colonize and develop mini-game in Traveller. I get to design new ships, see what works and what is never heard from again. Develop the processes and procedures that scouts will engage on in first contact situations. Do you send out ships with single gender crews so that in the case of misjump there is no competing colonies being established outside your sphere of control?

 

[Grav_Moped]

Every escort class ship and every small craft sensor picket is going to have the same sensor capability as the capital ships.

You are going to have so many ship scanning the sky that a complete survey is achieved in minutes. Thereafter you can focus the capital ship sensors on the threats while the escorts continue to sweep. It is probably the best thing you can do with heavy fighters

And still, there's the "it's a game that's a simulation of science fiction, not a simulation of an actual future" issue. You can take all the sensor drone swarms as read and carry on regardless, or require them to have some kind of in-game representation (with construction rules and costs and so forth), or choose to disregard them entirely, as you see fit.

 

[Spinward Flow]

Every escort class ship and every small craft sensor picket is going to have the same sensor capability as the capital ships.

What you think you did with what you wrote:

What I saw you do with what you wrote:

Let's just say that "opinions differ" on your assertion and let's leave it at that.

 

[mike wightman]

I should have included "at a minimum, with capital ships having multiple onboard sensors available."

 

[Spinward Flow]

LBB2.81, p32 (lightly modified to eliminate wargaming measurements in favor of in-world distances instead):

DETECTION
Ordinary or commercial starships can detect other ships out to a range of about one-half light-second; about 150,000 km. Military and scout starships have detection ranges out to two light-seconds; 600,000 km.
Ships which are maintaining complete silence cannot be detected at distances of greater than half detection range; ships in orbit around a world and also maintaining complete silence cannot be detected at distances greater than one-eighth detection range. Planetary masses and stars will completely conceal a ship from detection.
Tracking: Once a vessel has been detected, it can be tracked by anyone up to three light-seconds (about 900,000 km).

Having had more time to think about this particular question/problem ... I'm finding this particular answer increasingly UNSATISFYING.

The reason that I say that is because it's "too flat" of an answer to the question. It makes everything "the same" in 2 categories, resulting in a gross oversimplification that KILLS variety in design specs. One of those "you can have any color you want so long as it's BLACK" kinds of deals.

That said, the excessively simplified rule DOES provide some parameters to work with for creating a more nuanced house rule that respects precedent without overstepping it. If people like what I'm about to propose, I can cross-post a copy of this notion into the House Rules Forum where it can be easily found and referenced, rather than needing to dig through this topic thread to find this exact post.

---

Detection
Craft in space can detect other craft or objects out to a detection radius of (own computer model+Target Size DM+1) * 0.2 light seconds (60,000 km), with a minimum of 0.2 light seconds (60,000 km) detection radius.

TARGET SIZE DM (To Hit) from LBB5.80, p45 and p47:

Hull Size Code​	DM​
0 (zero)​	-2​
1 to A​	-1​
B to K​	0​
L to P​	+1​
Q+​	+2​

Planetary masses and stars will completely conceal a craft from detection.

This eliminates the distinction between "civilian vs military/paramilitary/scout" ships and puts everything onto a basis of "how powerful is your computer?" installed in your craft. Low powered computers have short detection (and tracking) ranges.

The only real modification here from precedent is to incorporate the Target Size DMs from LBB5.80, p45 into the mix.

---

Silent Running

• Craft in space that are maintaining complete silence with zero acceleration reduce the detection range radius to 1/2.
• Craft in space that are maintaining complete silence with zero acceleration while in orbit around a world reduce the detection range further from 1/2 (open space) down to 1/8 (due to being in orbit).

This makes it easier for small craft to "hide" by running silently and more difficult for LARGE craft to conceal themselves through silent running.

---

Tracking

• Civilian sensors: Once a craft has been detected, it can be tracked until exceeding 1.5x the detection radius.
• Scout/Military sensors: Once a craft has been detected, it can be tracked until exceeding 2x the detection radius.

This (home brew) ruling is a very different paradigm from that used in LBB2.81, p32. It means that Tracking radius is a variable (dependent upon computer) rather than a constant (3.0 light seconds for everyone, regardless of type), because the radius for Tracking can range from 0.3 light seconds (Civilian) all the way out to 4.0 light seconds (Model/9).

---

This House Rule yields a much more "textured" view of detection and tracking, to better enable "cat vs mouse" paradigms in game play when dealing with hunter vs hunted situations.

Silent Running makes it possible to "get closer" without being detected (the point and purpose of "stealth"), but size of craft becomes an important consideration for "how quiet" a craft can be to evade detection. If the purpose is to make a "sneak attack" then it's really a question of getting "close enough" to deploy whatever it is you've got in mind before you can be detected.

One casualty of such a house rule rewrite, however, is that Scout/Couriers (with their model/1bis computers) no longer have "awesome sensors" compared to civilians. However, an obvious solution to that problem is upgrade the computer installed in Scout/Couriers from model/1bis to a model/2 (for example).

 

[mike wightman]

I proposed something similar twenty years ago. It is so old the site can't find it so here it is from my archive, computer model and TL govern sensor capability, with LBB2 hull size mods ripped off from HG80 along with configuration.

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 the cubed root of [0.01x hull displacement x power plant number] or the maneuver rating used during that turn.

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:
< 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.

To update them I would look at where I could use a skill roll or two during combat to give players something to do.

 

[kilemall]

LBB2.81, p32 (lightly modified to eliminate wargaming measurements in favor of in-world distances instead):

Having had more time to think about this particular question/problem ... I'm finding this particular answer increasingly UNSATISFYING.

The reason that I say that is because it's "too flat" of an answer to the question. It makes everything "the same" in 2 categories, resulting in a gross oversimplification that KILLS variety in design specs. One of those "you can have any color you want so long as it's BLACK" kinds of deals.

That said, the excessively simplified rule DOES provide some parameters to work with for creating a more nuanced house rule that respects precedent without overstepping it. If people like what I'm about to propose, I can cross-post a copy of this notion into the House Rules Forum where it can be easily found and referenced, rather than needing to dig through this topic thread to find this exact post.

---

Detection
Craft in space can detect other craft or objects out to a detection radius of (own computer model+Target Size DM+1) * 0.2 light seconds (60,000 km), with a minimum of 0.2 light seconds (60,000 km) detection radius.

TARGET SIZE DM (To Hit) from LBB5.80, p45 and p47:

Hull Size Code​	DM​
0 (zero)​	-2​
1 to A​	-1​
B to K​	0​
L to P​	+1​
Q+​	+2​

Planetary masses and stars will completely conceal a craft from detection.

This eliminates the distinction between "civilian vs military/paramilitary/scout" ships and puts everything onto a basis of "how powerful is your computer?" installed in your craft. Low powered computers have short detection (and tracking) ranges.

The only real modification here from precedent is to incorporate the Target Size DMs from LBB5.80, p45 into the mix.

---

Silent Running

• Craft in space that are maintaining complete silence with zero acceleration reduce the detection range radius to 1/2.
• Craft in space that are maintaining complete silence with zero acceleration while in orbit around a world reduce the detection range further from 1/2 (open space) down to 1/8 (due to being in orbit).

This makes it easier for small craft to "hide" by running silently and more difficult for LARGE craft to conceal themselves through silent running.

---

Tracking

• Civilian sensors: Once a craft has been detected, it can be tracked until exceeding 1.5x the detection radius.
• Scout/Military sensors: Once a craft has been detected, it can be tracked until exceeding 2x the detection radius.

This (home brew) ruling is a very different paradigm from that used in LBB2.81, p32. It means that Tracking radius is a variable (dependent upon computer) rather than a constant (3.0 light seconds for everyone, regardless of type), because the radius for Tracking can range from 0.3 light seconds (Civilian) all the way out to 4.0 light seconds (Model/9).

---

This House Rule yields a much more "textured" view of detection and tracking, to better enable "cat vs mouse" paradigms in game play when dealing with hunter vs hunted situations.

Silent Running makes it possible to "get closer" without being detected (the point and purpose of "stealth"), but size of craft becomes an important consideration for "how quiet" a craft can be to evade detection. If the purpose is to make a "sneak attack" then it's really a question of getting "close enough" to deploy whatever it is you've got in mind before you can be detected.

One casualty of such a house rule rewrite, however, is that Scout/Couriers (with their model/1bis computers) no longer have "awesome sensors" compared to civilians. However, an obvious solution to that problem is upgrade the computer installed in Scout/Couriers from model/1bis to a model/2 (for example).

I’ve been posting these principles quite a bit, especially the computer aspect. I’d like a nod please.

 

[mike wightman]

It's not exactly a new idea.

 

[Spinward Flow]

I’d like a nod please.

Why?
I neither referenced nor even knew anything about what you might have done previously.
Nothing you might have written in the past went into what I wrote in #206, since I made everything up as I was posting it.

I did cite CT and used LBB2.81 and LBB5.80 as reference points.

 

[kilemall]

To repost mine-

Computer model x 100000 km = detection range, bis is model plus .5

TL x 100000 km = tracking range

One long range detection system per computer model number for the following-

Visual * 7
IR * 9
UV * B
Xray * D
Gamma * F
Particle * exotic
Mass
Acoustic * 5
Radio
EMF
Radar * 6

The sensors with an * come with an active set at the following TL, usually some form of laser. Radio can inherently transmit more complicated rules involving range. Acoustic is situational depending on atmosphere, liquid and/or gaseous properties. Particle will be custom base particle type aka StarTrek sensor of the week.

Ship bridges come with all of the above at doggo range (1/8 of computer range), hence almost impossible to spoof at that range

Small craft bridges come with short range radio plus one short range detection system from above list, assume doggo at computer model/1. Computer model systems apply as normal.

68A basic roll.

Roll at detection range.

If detecting ship is using active sensors and target ship is accel/decel, firing weapons or otherwise emitting EM system can detect, roll 6+.

If only one ship is ‘active’, roll 8+.

If neither ship is active, roll A+.

Stealth DMs apply per EM category. Ships can be stealthed -1 DM per 10% of total ship cost per category spent at ship building. Radio is usually not stealthed against, so 100% per -1 DM for all category / sensor types.

Size to hit DMs are applied as well, for both the target and destination ships. So typically ACS ships apply -2 DM since the target is smaller and so is the detecting ship’s hull array surface. Fighters would be -4 against each other.

After detection, ships need to have a target solution/lock on/scan to gain intel and fire weapons effectively. The only intel initially gained is size range, rough velocity, accel/decel and course.

The lock on is the same as the detection roll but computer models are compared and apply an additional +/- DM.

Firing without a lock on incurs a -5 DM.

A lock on immediately gives ship tonnage, exact velocity/accel, and additional information appropriate to that EM band with more successful rolls.

An active sensor lock on, radio/laser comm or energy weapon fire gives the target ship a chance to roll detect the locking/firing ship at detection range. All ships can do this, small craft only if its bridge sensor/radio or computer sensor is in the right EM category.




Doggo (no active emissions, weapons fire or access/decel/agility, passive sensors only, m drive on for em diffusion) x 1/8 range.

Side note- the complete suite of short range sensors standard to every ship size vessel means all ships are capable of planetary survey at short orbit or less ranges. They usually don’t have the personnel or software to process /analyze inputs, they are there mostly for space/planet danger safety, but can be so equipped.

My thought is something like the Nostromo from Alien, the Medic or the Navigator is usually acting science/survey officer for non scout ships. For Seekers the primary prospector will be using the suite for close rock assessment.

 

[kilemall]

Why?
I neither referenced nor even knew anything about what you might have done previously.
Nothing you might have written in the past went into what I wrote in #206, since I made everything up as I was posting it.

I did cite CT and used LBB2.81 and LBB5.80 as reference points.

I don’t expect everyone to have read and retain anything I wrote over the years, but I have been posting several times on this last three months.

As Mike said, a reinvention, so not worth quibbling on. Folks can pick and choose what they want to use, that’s the main thing.

 

[Carlobrand]

What you think you did with what you wrote:
...

I'd say you have that backwards but, as you say, opinions differ. After all, what ultimately happens in an imaginary far future game world designed for our entertainment is what we want to happen. If we want our very expensive capital ships adequately supported so they don't get needlessly ambushed, we will support them. On the other hand, if we're really, really hungry to throw the space equivalent of a submarine into that mix, then we'll find some excuse for making that happen.

We're covering a very broad topic. Commercial shipping as a rule would get away with minimal sensors because they spend most of their time in places where other ships want to be seen, to avoid collisions. No point in spending more than needed. Flashing active EM to detect each other while transponders squawk is the norm. Things get exciting when they take those ships out to more remote, less friendly places. Not a lot of need for complexity there: your free trader is not likely to have a light cruiser trying to sneak up on you, and the cruiser's going to be so well equipped to detect its own hostile opponents that spotting you before you spot him is pretty much a given. What we have is likely adequate to that task since a significant size disparity between the unlucky trader and his opponent is usually not worth playing out, though that's certainly an option.

Warships are a different story: well equipped to detect an opponent who would like very much to sneak up on you if they can, and with a strong interest in not being easy to detect - to the extent that's possible in open space. An escort is a tiny fraction of the cost of a capital ship, and a fighter's a tiny fraction of the cost of an escort, so fielding enough to give your capital ship adequate warning of a threat is quite cheap compared to the potential cost if you don't. On the other hand, there are those memorable encounters in which attrition and bad luck have left you in a vulnerable position, and then coming up with detection rules that let you play out that situation can be quite rewarding, whichever rules you choose.

 

[Black Vulmea]

It appears no one in this thread mentioned the sensor rules in DGP's Grand Survey;, or if they did, I missed it, which is entirely possible - I kinda glazed over at some of the repeated arguments. GS describes four types of sensors - passive/active EMS, densitometer, neutrino, and life - and includes "sensor arrays" the referee can mark with chits to reflect what information your sensors provide. Sensor results are determined by skill checks using the UTP.

Passive EMS in GS supports the notion there is (next to) no stealth in space, with a small subset of situations making tasks more difficult, but it also emphasizes that the information passive EMS gives you is limited: yes, a power plant is detectable by IR, but passive EMS won't tell you much more than its presence, its relative intensity, and its approximate range.



Active EMS, densitometers, and neutrino sensors can give you more detailed information, if your ship's equipped with them, allowing for identification as to size and whatnot; most commercial or private vessels aren't so equipped IMTU - their sensors are focused on not running into anything in high-traffic areas primarily. The full "sensor suite" is primarily provided for military, Scout (including most detached duty scout ships), and research/lab ships; type S starships converted to seekers have a 50% chance of retaining their Scout sensor array after the conversion, and of course these ships are highly sought-after.

The CT Book 2 "ranges" I use as sensor lock range rather than detection thresholds.

So, as others have noted, hiding isn't really possible, but disguising one's ship by modifying its power plant output or configuration may be possible to some degree; spoofing active EMS sensors is also a thing.

Because I'm playing a Beltstrike game right now, a couple of things have added a little nuance to this. First, IMTU any non-military ship underway - using its maneuver drive - in Imperial space is required to have its transponder active; belters will skirt this by tucking their ships in tight to a rock they're investigating or mining and turinng their transponders off to make themselves harder to locate by claimjumpers or pirates.

Second, one of the conditions in GS that affects EMS sensors is stellar flares, making detection more difficult. Lugh, the Reaginworld Belt primary, is a mild flare star, so captains and skippers (small craft captains) may attempt to hop between rocks in the aftermath of a flare event to reduce their likelihood of being spotted; this is risky due to induction currents and other nastiness associated with the flare, of course.

 

[whartung]

So, as others have noted, hiding isn't really possible, but disguising one's ship by modifying its power plant output or configuration may be possible to some degree; spoofing active EMS sensors is also a thing.

I think it simply comes down to not so much about "stealth in space". With distance and clutter and such, very possible for things to hide in the MASSIVE volume.

But, at the same time, there's no "surprise" in space. By the time a ship gets close enough to be a threat, close enough to do ANYTHING, targets will know it's there. Maybe not reading the serial #'s of the Jump Drives, but they'll have a solid idea that there's definitely a thing there, and how big it may be, and how much energy its radiating, and enough to ponder "Gee, should they be way out here in the dark and, hey, why is it coming toward me? Drake? Wake up the gunners...."

 

[kilemall]

I think it simply comes down to not so much about "stealth in space". With distance and clutter and such, very possible for things to hide in the MASSIVE volume.

But, at the same time, there's no "surprise" in space. By the time a ship gets close enough to be a threat, close enough to do ANYTHING, targets will know it's there. Maybe not reading the serial #'s of the Jump Drives, but they'll have a solid idea that there's definitely a thing there, and how big it may be, and how much energy its radiating, and enough to ponder "Gee, should they be way out here in the dark and, hey, why is it coming toward me? Drake? Wake up the gunners...."

My assumption for starship encounters is that course and vee signals intent, to the point where most ships have an auto alarm for anything getting near to matching course or close passes.

 

[Badenov]

So part of the problem is the simplifications that have arisen in some flavors of the game. The big one is 'Thrust Rating = Speed'. Anything under thrust in space is iRL entirely obvious just by plotting position vs time. If they have shut down/masked all electronic emissions and are moving on a ballistic trajectory (moving possibly, but not using their drive), they should track like an asteroid or space debris. Of course they're easy to avoid like this, so...

The object of electronic countermeasures is to make opponents' sensor reports either unusable or misleading, and if that can be done, a ship under thrust may be able to mask itself by burying the tracker in noise or confusing the returns their ship is providing.

 

[whulorigan]

I think it simply comes down to not so much about "stealth in space". With distance and clutter and such, very possible for things to hide in the MASSIVE volume.

The problem is not the massive volume. The problem is the Hot 300+ K "Infrared-wavelength spotlight source" object beaming out against an utter frigid-cold pitch black 2.7 K Microwave background "massive volume". The analogy would be as if one were out on flat plains on a moonless midnight away from all artificial lighting when it is overcast, and someone a mile away started shining a flashlight in the pitch black, or someone way off in the distance turned on the lights on the upper floor of a multi-floor building. You could easily see it from far away, because it is a bright spot against the dark. It is fundamentally different than what we are familiar with on Earth because everything on Earth is relatively close to everything else in temperature (i.e. "light grey" vs. "medium-light grey"), and there are things to hide behind and/or "in". To make things "relatively close in temperature in space" is usually destructive to the ship and/or crew, one way or another.

The other issue in space is determining/triangulating the distance to the source and establishing that it is indeed a close-by object and not something at an interstellar distance (if not otherwise obvious), and if necessary, resolving a target lock.

That is why Mike Wightman's assertion to use gravitic heat sinks is such a good one, if you want to do the "stealth" and/or realistic heat-dissipation thing in a campaign. It is a way to move heat-signature off of the ship non-thermally using already established Traveller-tech in a reasonably disbelief-suspensible manner within the context of the tech paradigm, and still be able to mostly "blend in" both thermally and potentially gravitically to the background.

 

[mike wightman]

Note, my proposal of a gravitic heat sink is not a cloaking device, the ship is still detectable, just much less so.

Gravitic sensors may well pick up stealth craft so you know they are there, but to get a firing solution...

 

[Spinward Flow]

The problem is the Hot 300+ K "Infrared-wavelength spotlight source" object beaming out against an utter frigid-cold pitch black 2.7 K Microwave background "massive volume".

Taken to its (il)logical conclusion, it is therefore IMPOSSIBLE to miss ANY object (natural or artificial) within the entire Milky Way Galaxy when using a simple, ordinary, bog standard sensor scan.

Even a brown dwarf rogue planet (with "surface" temperatures well in excess of 300+ degrees Kelvin) wandering between star systems would be ... trivial ... to detect at a distance of light years away. You don't even need to roll anything ... it's just, automaticgic.

Why?
See quote above.

The analogy would be as if one were out on flat plains on a moonless midnight away from all artificial lighting when it is overcast, and someone a mile away started shining a flashlight in the pitch black, or someone way off in the distance turned on the lights on the upper floor of a multi-floor building. You could easily see it from far away, because it is a bright spot against the dark.

Your scale is wrong by multiple orders of magnitude.

A better analogy would be if someone standing on planet Terra switched on a flashlight and deliberately pointed it up at satellite Luna (~385,000 km away, or about ~1.3 light seconds distant).

Would a sensor on Luna be able to easily/trivially/automatically detect (and correctly identify) the light of that flashlight pointed up at Luna without error or difficulty of any kind? Basically, would the sensor suite be "so good" that you could flick the flashlight on/off and send a morse code message with the light of a handheld flashlight (from Terra to Luna) and have it be clearly/plainly visible and trivial to read by the sensor suite?

You could easily see it from far away, because it is a bright spot against the dark.

If you know EXACTLY where to look.

The challenge gets VERY different when you DON'T know exactly where to look ... and therefore, have to search (or better yet, are continuously searching).

For example:

In this image of beach sand ... find the 1 sand grain that is a uniquely specific color because it is a speck of precious material (pick your gemstone of choice) rather than a variety of common silica. Take your time searching EACH GRAIN OF SAND in order to find "the right one" that you have been challenged to locate and extract from the background.

Take ALL THE TIME you need to sift through the sand to find whatever it is that you're looking for using your hands eyes sensors.

Then do the same thing again for the NEXT patch of beach sand.
And the NEXT patch ...
And the NEXT ...
(ad infinitum)

To make things "relatively close in temperature in space" is usually destructive to the ship and/or crew, one way or another.

LBB4 p41:

Hmmmm ...

So @ TL=12 it's possible to create a "man sized/shaped space craft" (which is what a vacc suit actually is) and actually "harden" it against hostile environments (see: Combat Environment Suit ) or even ARMOR it for use in vacuum (see: Combat Armor ) and engineer it with a chameleon function that ... and I quote ... "selectively bleeds heat to match the background IR level, effectively rendering a soldier invisible to IR sensors."

But it's NOT POSSIBLE to do anything similar for something larger than man sized (such as a small craft/big craft/starship).

Um ... ... that's akin to asserting that my air/raft can use gravitic thrust (no problem! ), but no spacecraft/starship can (don't be absurd! ).

It's an argument ... I guess ...
Not a very compelling one ... but it's an argument ...