HIWG DOC : 142.19 DATE : 12. MARCH 1997 TITLE : SENSOR RULES FOR TRAVELLER By : Roger Myhre PURPOSE ------- To simplify the sensor rules in Traveller. Not that I feel it is necessary, but due to the fact that many people have difficulties with dealing with how the rules are written. As an old sensor operator from the Royal Norwegian Navy, I can say that the rules presented in BL is a very simplified model of the real thing. I will try to make the things a bit more realistic, but not more difficult to use. Some may react to how easy there is to detect things in with these rules, but consider this. Where do you hide in space? As on a planet there are no clouds to hide the IR signature behind. Neither is there a horizon to duck under. Just a wast stretch of nothingness. CONVERSIONS ----------- DIFFICULTY MODIFIERS As the rules are meant to be used with several types incarnation to Traveller, I will use a generic system that should fit into MT task system and the TNE task system. As I haven't studied the T4 system too well I think you'll have to tweak the system a bit to make it fit. CT I have never used or owned so I don't know how the system will fare there. Generally when there is positive numbers it will make the task simpler and vice versa. In TNE add the modifier to the asset before the roll. In MT it is a straight DM with a max of eight in either positive or negative numbers. In T4 positive numbers are added to the skill before the roll, and negative numbers subtracted. DIFFICULTY LEVEL In all types of Traveller the difficulty is at Difficult level. In MT that is a target number of 11. In TNE it is asset times one. And in T4 it is 2.5D against asset. PROCEDURES ---------- DECLARATION PHASE All units declare if they will go active or passive this turn. They do also declare what kind of sensors they will be using if any. If there is several players combating each other this is done secretly. Before any units can be targeted they have to be detected. As BL assumes everyone is sort of detected, but not properly pin pointed and identified. That's why we use the green blobs at the start of the BL game. DM CALCULATION The scanning unit adds up his DMs. The defending unit add up his. The defending DMs are then subtracted from the attacking players (or added if the defender got positive DMs) ACTIVE SENSOR SCANS Determine the rangeband of the sensor the target are in. Find the signature DM from the defending craft and add them up (or subtract) Example: An active sensor tries to detect a bogey at medium range. This gives a DM of +5. The defending craft is a 200 ton SL needle crafts with EMM. This gives a defending DM of 0. (0+1+0-1). This gives the attacking scanning unit a DM of 5. ACTIVE SENSOR AGAINST JAMMING The procedure is the same as the procedure above, but subtract the Jammer DM. To improve the chances of jamming the jamming player may roll a difficult task. On a success the jammer may add an additional -2. Additional modification is the TL difference. This modification is added or subtracted from the jamming task roll. PASSIVE SCANNING AGAINST ACTIVE SENSOR Add the active sensor DM to the passive sensor DM and add 5. Example: An active sensor got a short range of 5 while a passive sensor got a short range of 3. The units are 15 hexes apart. This is at Extreme range for the passive sensor, which gives a -10. A range of 15 is medium range of the active sensor which is a strength of 0. Adding these two numbers together gives a DM of -10. Then the special DM of plus 5 is added giving a total of -5. Sensing against jamming sources uses the same procedure, just invert the jamming table. Short range is a signal strength of 15 and so on. PASSIVE SENSOR AGAINST IR SIGNATURE. Add the passive sensor DM to the crafts IR signature. Remember to modify the IR signature depending on Acceleration, direction and so on. PASSIVE EMS SCANNING If the passive sensor is an EMS sensor use the signature that gives the best detection chance. All other scans just gives supplemental information that can help identify the craft. DENSITOMETER SCANS Find the gravity signature of the scanned craft. This signature is the signature strength of the first hex (the hex the craft occupy). The DM is halved for every hex from the scanned unit to the scanning unit. Round to nearest whole number. When you reach 1 the next hex it will be 0. From there on double the numbers from -1. Detection is considered automatic far as the numbers are 2 or more in the gravity signature. Example. A 2430ton craft has a signature of 49 at the adjacent it is 25 and then 13 and then 7, 4, 2, 1, 0 at the eighth hex. TABLES ------ SENSORS Range\Type Active Passive Jammer Short 10 5 0 Medium 5 0 -5 Long 0 -5 -10 Extreme -5 -10 -15 RADAR CROSS SECTION The RCS can be found by using this chart. Size RCS -1 -2 -10 -1 -100 0 -1000 1 -10000 2 -100000 3 -1000000 4 1000001+ 5 HULL FORM MODIFIER Hull form DM Needle 1 Wedge 1 Cylinder 1 Box 2 Sphere 0 Dome/Disc 1 Close Structure 2 Slab 3 Streamlining affects the signature as following: USL +3, AF and SL +0 EMM gives -1 IR SIGNATURE IR signature is from the crafts powerplant and maneuver drive. The signature of the powerplant is calculated like this: square root of MW output divided on 10. Round to nearest whole number. It is then adjusted according to drive. Heplar and Fusion rocket =2 per G of acceleration when the plume is facing the scanning unit. 1 per two G when away. From the side there is 1 per G. Thrusters gives +1 if facing scanning unit. EMM gives -2. Running at minimum power gives additional -5 DENSITOMETER SENSING This will only give general direction (+/-5 degrees) and approximate movement direction. Range for fire resolution must be acquired with other sensors. The signature is calculated like this: Square root of weight of craft + 2 if using G compensators + 2 per G if using Thrusters. Round to nearest whole number. Detection is considered to be automatic if the gravity signature is 2 or more. A task roll is necessary if the signature drops below 2 or if there is a planet in the same direction or close to the craft. UCP LISTING ----------- WHY? So that there are no need to calculate all the data for each time a starship encounter is taking place. FORMAT It should be placed in a box at the top of the sheet/page where the UCP is listed. Example: RCS IR Gravitic Target size DM +3 3(2-1-1/2) 32 See below This example is a ship with Heplar drive. The IR section list the Powerplant IR signature outside the parenthesis, and the drive signature inside the parenthesis. The format is as following: Aft, Side and then Front per acceleration gee. So if the craft is scanned from behind while it accelerates 2gee the scanning unit gets a modification of 7 (3+4). Target size DM is handled as the rules states in the different Traveller version. ADVANCED RULES -------------- 2 TYPES OF JAMMIING There is basically ways to jam a sensor. Sensor degration and deception. The first is rather simple. Basically there is only to send out enough noice to blanket out the screen of the opponent. The draw back with this is that the enemy knows that he's being jammed and can change frequencies or elect to home in on the noise. Deception jamming is far more difficult. It requires the jamming unit to know what kind of a sensor the opponent is using , frequencies, procedures and so on. The main goal with deception jamming is to make the opponent believe that the enemy comes from another direction. Or diverts interceptor, missiles or laser fire against fictive target. A unit that is targeted by a director beam can feed the beem false information making the targetting sensor believing that the target is following a certain course. PROCEDURE Use the rules mentioned above for noise jamming. For deception jamming the jamming player states which unit will do the jamming. If the unit has several jammers each jammer may jam a seperate target. The jamming player then states which target he wish to jam and what kind of effect he wants to have. And where he wants the false echos to appear on the map. However this should be within the same hex arc as the jamming unit of the target. The Jamming player then rolls a difficult opposed task according to the respective Traveller rules. A success allows the player to place 4 false targets on the map. To keep up with the jamming for the next turn a new task must be rolled. This time the difficulty is routine/average. On a failure 2 false targets are removed from play. On a spectacular failure all false targets by that unit is removed. The clue is that the opposing player must not know what is the real targets or false targets. False targets may be moved on the board for each movement phase. There are no limits to how they move or maneuver, but if the movements are too obvious (ie accelerating incredebly fast or turns on a dime) the opponent may guess that the targets are false. The best way to defend against this type of jamming is to "detect" the false tracks with a passive sensor. they will not be tricked by deception jamming, as the false tracks are not visible in the visual spectrum or the IR spectrum. However the defending player may only try to detect one false target a turn per passive sensor. MASKING MISSILES Deception jamming may be used to mask missile attacks. Four false missiles may follow a few in to a target to increase their survivability when attacking a starship. The target that must defend against these missiles before they hit, must prior to firing any anti missiles weapons, state which targets he fires at. (C)1997 Roger Myhre