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Old April 19th, 2004, 07:51 PM
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I am trying to make up some useful, simplified sensor rules for space combat, and am in a quandry. Here are some of my ideas so far:

There are 3 basic kinds of detection levels: Bearing, Fix, and Lock.

Bearing: you know which direction a ship is in (roughly). The range is not known, though it could be inferred by signal strength or taking multiple bearings over time (as seen in WW2 submarine simulators). Bearing can be achieved only with passive sensors. Beam weapons cannot be fired on a bearing target, and missiles and craft probably should not be launched either, but they can be.

Fix: This means you have a bearing and a range, and probably a course and acceleration too, but it's not good enough to fire beams with. Firing missiles or sending craft out to it are possible. Guesses as to size of target can be inferred by signal strength and range. Generally, this can be gotten with an active sensor, or by triangulation with 2+ passive sensors. It can also be gotten with a single passive sensor if either target or sensor are moved at least 30 degrees relative to the other (synthetic aperture and inverse synthetic aperture, respectively).

Lock: This is a targeting solution that is good enough to fire a beam. In general, only a specialized high-resolution active sensor can acquire this, but if the target is not evading, it can probably be done passively given enough time.

I have decided that Bearings and Fixes will not require task rolls. Either you have them or you don't. There should be a Threshold value that must be achieved in order to make the detection. Ships will have a certain base signature that they start with, depending on their size. This signature will be modified by what the ship is doing (drifting, accelerating, running,...), if the ship uses active sensors or area jamming, and so on. The sensor ship will also have a couple mods to this, like if it's deployed its folding array or if it's got its maximum or minimum aspect facing the target (increase resolution).

Locks, however, must be rolled for. ECM, ECCM, and in the case of passive lock attempts, jamming will have modifiers to the die roll. Considering that Locks are usually generated by little Lidars and stuff like that, these don't really vary with the size of the sensor ship, and I don't think they will vary too much with the size of the target ship, but correct me if I'm wrong.

So I'm thinking that a ship has a Lock range for its sensors. This range is based on, typically, the TL of the sensor, though if you guys really think pumping a lot more power into it will do any good, then power level will have an effect too.

I am giving the Lock range an arbitrary value of 20 hexes at TL9, and it will probably go up 2 per TL, maybe 3 per TL.

I am thinking that with the signature rules, the passive sensor will get a threshold value. Then if the target's signature, + modifiers, equals or exceeds the threshold, the target is detected as a Bearing, and if it's detected by more than one ship or with active sensors, then it is a Fix. using Active sensors in the task will improve the threshold, as long as the target is within the active sensor's range, and out to double that, it will improve the target's chances of detecting. Likewise, having your passive folding array deployed will also give your target a better chance to see you.

Now please keep in mind while you are formulating your response that I am not using the exact BL rules here, I am trying to condense them into a much more manageable system, and am trying to at least keep the concepts the same, but such is not always directly translatable. I am fairly familiar with BL, and so you CAN express things in those terms if that helps you.

So anyway, what glaring holes do you see in this model so far? Anything critical seem to be missing or anything seem to be overcomplicated? What other thoughts do you have?

Thanks for your assistance!
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Old April 19th, 2004, 08:37 PM
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Erm, a slight clarification: regarding the threshold value, what I want is the result to be a number of hexes, and if the target is within that range of the sensor, it is detected, if not, it isn't.
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Old April 20th, 2004, 01:52 AM
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This article at Freelance Traveller has some CT sensor rules that could be adapted to get your bearing and fix ranges for sensors at different TLs.
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Old April 20th, 2004, 12:41 PM
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This is the link he meant to provide. That other one doesn't work.

That did help with a couple of concepts. Much of the things presented in the article are things I have already figured out for myself, but there are a couple things the article has helped with. Thanks for pointing it out!

He's got one glaring error in his procedure, though, and that is to assume that you can fire a beam on Bearing-only. Assuming your Bearing-only data was extremely accurate, he would be half-right, but it generally would require that the target is not evading and is within weapons range. I personally don't allow this kind of fire at all, since you don't know the range, and is why I have a 'Fixed' level of fire control. This functions like a BOL (bearing-only launch) for guided weapons like missiles and fighters. Ships do not have the infinite range to chase after every sensor ghost and missiles are usually too few to waste on a target so far away that it is likely to miss.

Anyway, like I said, this helps, and in the meantime, I've stumbled across a couple other ideas to help out what I'm after. Since this system is intended to handle dozens of ships at a time, I suspect that I may eliminate even the die-roll for getting Locks.

The original rendition also called for rolls to determine hits, and then rolls to determine how much of the hit was to be applied. (Even if you hit for full energy, there's still a good chance that your shot is smeared over the hull and does nothing.) I modified this into a single roll, such that the better you roll, the more of your shot's power does damage. If the ship battles are big enough, it may be necessary for smooth flow to simply remove the die-rolls altogether! But I do like for there to be SOME randomness in a game; it shouldn't always be calculable by an intuative mathematician.
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Old April 20th, 2004, 04:18 PM
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http://freelancetraveller.downport.c.../tech/ecm.html

http://www.freelancetraveller.com/fe.../tech/ecm.html

Both of thes work for me???

Don't you just love computers

Are you going to post your final rules?
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Old April 20th, 2004, 06:46 PM
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TheDS
Seems to me you're making hard work of work that's allready hard enough. As I understand BL's sensor rules, if an object is within extreem passive range you get that object as a bogey. ie you know somethings there you just don't know anything else about it. If you succeed at a sensor task based on range to target you get a lock. Now that seemed fairly simple in what many people complain is a complex and difficult ship combat system. Why do you want to add another type of sensor result, bearing, fix, and Lock, when Bogey and Lock do the job.

"I am trying to make up some useful, simplified sensor rules for space combat, and am in a quandry. Here are some of my ideas so far:"

Maybe I'm just playing semantics but it seems to me you're adding complexity not simplicity.
Don't get me wrong adding complexity is fine, it's why I play/ref TNE rather than CT. It just struck me as odd that you'd call it simplying the rules. I too would like to see what you finally settle on.
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Old April 21st, 2004, 01:56 AM
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You are describing what it was like using fuzzy radar images of the Vietnam era. Back in the '80s synthetic aperature radar could give 30m resolution at dozens of km, and passive FLIR was sufficient to launch air-to-air missiles on targets at any angle of approach. What the US mil has now blows that away. Any reasonable extrapolation to tech centuries more advanced is a handwave.

Beams should work on "bearing only" data, because it should include an order-of-magnitude range. If your beam is limited to 30K you'd know if the bogey is closer to 10K km or 100K or beyond. For a target closer than that, bearing-only wouldn't really apply unless it's a black globed ship.

Your gunner can take a guess at relative vector, and since it only takes 0.1 sec to cover 30K the estimated velocity need only be good to a factor of 2 at that range. The real challenge to the gunner's skill is guessing the angle of motion from a short series of indistinct blips.

A sensor fix is more than enough to fire beams at full accuracy, and is the best you can do with passive sensors. A lock means that active sensors has focused a narrow coded-pulse beam on which a passive missile can home, which would give your gunners a slight bonus to hit.

In the case of target ECM, then you get something less than a sensor fix where you know your incoming data is screwed. You may have spurious images that make a fix impossible and give multiple targets for your gunners to choose among.
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Old April 21st, 2004, 10:21 AM
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Sigg:
Well, now they're both working for me too. Go figure I'll post them, but not here, for two big reasons: 1, everything here is legally owned by these guys, and just in case in the future some letigious dufus takes over, I don't want them messing with my stuff, and second, they are part of a whole package of space combat, and the whole package deserves better presentation than your typical forum HTML can give it. I do my best work with Word and suck at HTML.

Badbru:
Very valid concern you have there. It has always been my feeling that sensors is a much more complicated thing than simply saying you detect everything within a stated range. I like the idea of being able to "game" the enemy sensors. A big ship is detectable out to a range far greater than a tiny missile. A big ship does NOT have the agility that a small ship does, even if it has a higher G rating. I consider agility to be the ability to change your heading rapidly, and I have discussed this in better detail elsewhere, but can't seem to find it, so I'll give a brief illustration.

Say you have a 400 ton ship, and its length is 50 meters. Say you also have a 400,000 ton ship and its length is 500 meters (proportional dimensions require cubing the volume). If you want these ships to be able to rotate 180 degrees, and do it in one second, the outer parts of the hulls are going to be put under a lot of rotational stress. The 50 meter ship's extremities will travel 25*pi= 80 meters; in one second, that's about 8 G's of force (approximation based upon 1G=10m/s; I haven't figured what it actually is, but I suspect it's higher, but this over-simplification works for our illustration.) Most ships are not designed to withstand more than 4Gs. Now rotate that big ship in 1 second, and we have about 80 Gs. This is WAY beyond what ships are designed to, never mind the engines to turn them that fast.

So I aim to put these very real concerns back into the simulation. If you want to play it simple, well, have each ship roll a pair of dice and the highest one wins, but if you want to be able to do things that something like Harpoon allows, then you need a little bit more. The challenge is in getting Harpoon-like realism but keeping it simple and fast to allow a dozen ships to duke it out in a few minutes. I am also strongly influenced by the Challenge article which did much to explain TNE's combat system.

T4 has an updated sensor system that aims to make sensors more realistic, but unfortunately, the system is a bit heady. I made something similar before it came out that used powers of 2 insted of powers of 10 for greater resolution, and to make it a little harder to figure out in advance if there was a +1 difference between say a 9 ton and a 10 ton hull, but not between a 10 ton and a 99 ton hull (as in every edition of Traveller). Why make a 1000 ton ship when 999 is just as powerful, yet harder to hit and see? But unfortunately I never finished it; I just have a few tables and ideas.

This idea that I've struck upon just recently, though, is so simple, I wonder why I didn't see it before, and why no one else did. Simply figure out what a ship's Signature and Detection base ranges are, and that's part of their stats. Then add those together, plus any situational modifiers, and that's the max range at which the sensor can see the target. It can be adapted to role-playing by simply making sensor operator skill one of those situational modifiers; the player rolls and adds some form of his skill to the range, based on how well he rolled. It's so simple, and it's actually not too far from the real performances that you would get if you whipped out your calculator; the hard part is in choosing the specific values, and that takes some math and guestimation on MY part, not the player's.

Straybow:
Keep the ranges in mind that we're talking about. In order to get a Lock-level firing solution, the target must consist of several pixels on your radar display, like a couple dozen, maybe hundreds. For that, you need resolution, which can only be gotten by being close, or by having REALLY big passive sensors. Anything less than that, and though you may know where the target is, that knowledge is only good to within a dozen or a hundred meters, depending on the range and size of the target.

In order for your energy packet to arrive at the target and damage it, it must be focused onto as little of the hull as possible. TNE assumes you can focus it to a single square cm, and anything larger than that reduces the damage done; that's why damage decreases as a function of your range. in order for you to keep your beam focused that well, you've got to track the target while it's moving. We're talking about accuracy that is unheard of. I think Challenge 71 is the one that has the discussion of TNE space combat. I found a few inaccuracies in it, but the message is still clear, and that is, if you cannot tell where your target is to within a couple meters, or where he is going, you may get lucky and hit, but it won't do any good.

When the ranges are measured in tens or hundreds of thousands of km, the picture is going to be a little fuzzy. When the target uses stealthy materials and design, the picture is going to be fuzzy and faint. And when the target is small, you're probably not going to see it until it's in your face.

I have defined a Lock as being a beam-capable firing solution, a Fix as a missile-capable firing solution, and a Bearing as a minimal detection. Works a lot like Harpoon, which we all know has won high praise for its level of realism, but doesn't require half an hour just to determine if a detection has been made. Sure, you CAN fire your beams on a Fixed target, but your chances of doing anything useful are close enough to 0 that you may as well save the energy.

ECM, as you say, works to give the enemy ghosts to shoot at. ECCM works to undo this. This basically means that if I'm using ECM, I can reduce the range at which you can achieve a Lock, because if you're close enough, I can tell the difference. Your ECCM can figure out which target is the real one, and hence means that you negate some or all of the range penalty my ECM is imposing.

Stealthing/EMM works to reduce the range at which a target can be detected, and is part of the ship's Signature, which is a characteristic of the ship. It might reduce Lock range as well, but unless some one posts some compelling evidence to the contrary, I am going to say it doesn't affect Lock range.

Area jammers are good for making yourself seen, but they also block what's behind them. They are better at doing this to passives than to actives, because actives have a coded return signal that can be seen through the spotlight shining in your eyes. Decoys, if I decide to use them, will operate like ECM, since that's basically how they operate in BL. I may also put in drones, which can act as spies and decoys, but I'll figure that out later.

I want to give options, but not so many that your head is swimming in them.
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Old April 21st, 2004, 01:11 PM
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Have you seen the Traveller 2300 game Star Cruiser?
The Babylon 5 Wars ship combat game had some ineresting rules for EW IIRC.

I agree that a ship's data sheet should include its sensor profile for detection purposes, the question is:
how do you calculate them easily (the factors as I see them are power plant output less masking for radiated signature, hull size/shape/stealth for reflected signature)?
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Old April 21st, 2004, 03:11 PM
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What I have for now is this:

Ship size + Ship Config + Reactor output + Stealth (well, MINUS stealth). I have 2 orientations: broadsides (maximum profile) and foreward (minimum profile). Basically this gives you 2 numbers, one for minimum profile and one for maximum profile. There is a third digit for engine output, which implies you will either go full thrust or drift, however, this engine value gets multiplied, depending on what you are doing. Closing on a target is x1, crossing is x2, and with engines facing it, x4 (maybe more).

So a large, long ship may have a Signature thus: 13/19+5. 13 is the minimal profile, 19 is the maximal profile, and 5 is the extra added if you are using your thrusters. For instance, if this ship were retreating, I would start with 13 (minimal profile) and add 20 (5x4), because the engines add 5, but this is multiplied by the ship running away, which is 4. So the total signature in this case is 33.

A passive sensor's performance is directly related to its size and configuration also, so we add Ship size + Ship config + something else (I don't have all the details yet). Again, performance depends on the orientation of the ship, so head-on detections will have a different range than crossing detections. A passive sensor for that same large, long ship might be 12/16. If you have a deployed folding array, then it is going to be a large, fixed value, independent of the ship's size or orientation, but it will increase your signature.

Ships that are in the frontal/rear arc will be detected with the foreward value (12, in this case) and those in the side arc will be detected with the broadsides value (16 in this case).

So if your ship is crossing a target, it adds 16 to whatever the target is doing. If that ship is also crossing, and we use the above ship's signature as our example, then that ship can be detected out to a range of 16+19 (assuming it is drifting), which is 35. If the target is within 35 hexes, you have a Bearing on it. If you have 2 ships seperated by at least 30 degrees from the target, and the target is in range of both of them, then you have a Fix instead. (30 degrees is partial encouragement for players to spread their ships out some instead of bunching them up for the defensive bonuses.)

Things like Ship size and config and reactor output all have certain values assigned to represent them. For instance, a Size of 5 might represent a ship 500,000 tons displacement. A spherical ship will not have significant modifier to the fore/side arcs, so it gets a -0/+0 modifier. A long ship like a Needle will have about a 5:1 or so length to width ratio, which means it can see about twice as far, but since it is not necessarily going to have more antenna AREA, the sensor will not get the 2x modifier you'd expect; instead it gets a modifier of like -2/+2. it is harder to see and see from the narrower fore-arc, but easier to see and see from the wider side-arc. A folding array simply has a specific size and therefore has a specific value; it doesn't matter what angle it's looking at.

Reactor output is likewise reduced, such that a 10Gw reactor might be worth +6 on your signature. I am experimenting with the idea of allowing a ship to minimize its output, to allow it to get even closer to a target ship, and thus I'd have to list what the modifier for the reactor is, so that it can be added or subtracted. For now, I don't think it's worth the effort, but the possibility remains if it winds up being called for.

Active sensors are going to depend on your passive sensor and on how much power you are emitting, but you will always give away yourself out to double your range. I am thinking of giving them a specific value, dependent on the power output, and adding that to the passive sensor.

Modern day active/passive sensors are seperate devices, because the ranges are so low and the time it takes to get to target are almost null in relation to the speed of the waves. But in space, when your ranges are measured in fractions of light-seconds, the algorithms used in modern radar will not work, and instead, you have a transmitter and use your passive sensor as your reciever. I am unfortunately not legally allowed to go further into this, and indeed, I don't know the full story, but part of my stint in the navy dealt with the operation of radar. I guess you could say I know enough to break something, but not to fix it.

The sensor range is further modified by situational modifiers. Is the target using ECM? Do I have ECCM to undo their ECM? Is there space debris in the way? Is the target evading? Other questions arise, and these are treated as simple numbers which add to or subtract from the above-computed range if they apply.

Important side note: a ship that is NOT evading is not as easy to detect, but IS easy to shoot, but an evading ship is easy to detect but HARD to hit.

But I am still trying to figure out exactly what goes into a ship's ability to detect another ship. It seems to me there should be something in addition to the 2 items listed, things which ALWAYS matter, like your dish size and area matter. Oh, TL will play an important part as well in EW. EW is more effective at higher tech, but higer tech sensors don't really do much for you except reduce their volume a little, and most sensors are small enough that it doesn't matter. Folding sensors matter, of course, so their size will be noted.

Hopefully this has helped you guys see what I'm saying a little better, and allow you to be more specific with your ideas.

Er... and no, I haven't seen Star Cruiser or the B5 game, but I will take a look right quick and see if I can borrow a copy from someone who has just about everything.
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