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Published by Samuel Penn.

Also, see my profile for things that interest me.

Glendale Website - My main web site.

Yags - Main site for yet another game system, a generic GPL'd tabletop RPG.

Yagsbook - Documentation on the Yagsbook RPG documentation format, a Sourceforge project.

Mapcraft - Documentation on world mapping tools, another Sourceforge project.

Midnight Saga - An Ars Magica campaign.

Active Topics

The current topics are currently under active development (relatively speaking).

Yags is Another Game System - Game design notes for Yags, a Free roleplaying game system I use as the core system for most of my campaigns.

Yagsbook - Notes on an XML based documentation system I use for documenting Yags and related campaigns.

Full Thrust - Notes on Full Thrust

Stargrunt - Notes on Stargrunt.

yags:starships:sensors

Starship Sensors

See also: Stealth.

A vehicle has a Perception stat which is a general measure of how extensive its sensor systems are. Vehicles only have a Perception rating if they actually have something like radar, rather than relying on Mk I eyeball to spot things.

See Example Starships for some starship sizes, which will give an idea of how easy some things are to spot.

Sensor Quality

Based on the Perception, which is a factor of the design, and the skill, which is a factor of the computer systems doing the processing. Standard software is determined as follows:

TL Software skill
6 2
7 3
8 4
9-10 5
11-12 6

Quality software is +1, expensive +2, cutting edge +3. May be modified by a good operator.

Detection Ranges

How easy it is to spot things depends on the type of sensors you have, and how exhaustive they are. Sensor types are as follows

Sensor system PER Range Cost Notes
Basic sensors 2 3” 1KCr Takes up no space, fitted as standard
Fixed sensor 2 10” 10KCr Front arcs only
Light sensor turret 3 10” 10KCr Full coverage
Heavy sensor turret 4 20” 25KCr Full coverage
Barbette sensor 4 30” 60KCr Full coverage
50t sensor suite 5 100” 1MCr Half coverage
100t sensor suite 6 100” 3MCr Half coverage
50t deployed array 6 1,000” 10MCr Must be deployed to use (1 hour). Two fit in a 100t bay
Sparse orbital array 5 10,000” 100MCr Fixed installation
Standard orbital array 6 100,000” 500MCr Fixed installation
Dense orbital array 7 1,000,000” 2.5GCr Fixed installation

Multiple turret sensors on the same craft can be combined. Increase range by the square root of the number of turrets - if mixing sizes, a heavy turret counts as 2 light, a barbette as 3 light. Bay sensor suites can't easily combine.

Deployed arrays can be combined, multiply range by number of arrays.

Modify PER according to the following options:

PER Option
-1 Sensor is TL 7
+1 Sensor is TL 9-10
+2 Sensor is TL 11-12
+3 Sensor is TL 13+
+1 Sensor is advanced construction, x5 cost
-1 Damaged

A basic sensor effectively takes up no volume in a spacecraft, and are fitted as standard in most designs. They are robust, reliable and lightweight, however they are really designed as backup in systems which already have extensive sensor coverage from fixed systems.

A Dedicated Sensor takes up 1t of dedicated space, and is normally turret mounted.

Detecting Things

To detect something, the basic difficulty is 0. Add +5 for each range band of distance, and -5 for each point of signature (normally just Size) of the object being detected. No roll is made, if the Perception x Skill of the sensor beats the difficulty, then it is automatically detected.

For example, a typical TL10 Traveller ship may have a Perception of 3, and a software rating of 6 (it's software has been upgraded recently). This gives a total of 18, with a range band of 3”. It could detect a small fighter (Size 14) at a range of 51”. If it had a light sensor turret, with a rating of 24, range 10”, then the same fighter would be detected at 180”.

A Broadsword class mercenary cruiser (800t, Size 25) can be detected out to 290” in the latter case.

A Class A starport will often have a dense orbital array, rating (9×8) 72, range 1,000,000”. It would detect the fighter out to 28,000,000km. If it was using thrusters, then this increases to 280,000,000km (almost 2 AU), or 20 AU to know that something fighter-like was there.

A small private base on a moon probably has a deployed array, rating 48 range 1,000km. It's extreme edge is 240,000km, or 2.4MKm for anything using thrusters.

The detection range is actually the range at which the target will be identified. Out to double the range, it is possible to get a fix on the target (not good enough for shooting with anything other than missiles) and an estimate of its mass (to 2 significant figures). Out to ten times the range, a very rough order of magnitude estimate can be gleaned, with its rough location and mass (nearest order of magnitude).

Note that anything broadcasting IFF, will be picked up and identified at this extreme range. A ship that is running silent (shutdown drives and as many other systems as possible) can halve the detection range.

Other modifiers:

Drive type Range modifier
Chemical x10
Plasma/Fusion x100
Thruster x10
Active sensors x10
Active sensors (turret) x100
Active sensors (deployed) x1000
Active sensors (orbital) x10000

A sensor system can switch to passive only, in which case divide detection range by 10.

Planetary Sensors

Planet based sensor system are similar to Orbital, but may be limited by atmosphere. Divide range according to the atmosphere type:

Atmosphere Range
Thin /2
Standard /3
Dense /10
Very Dense /100

Looking Carefully

The above all assumes real time indications of something being there. A clever person (or computer system) can pull back data for a larger time window and detect things a lot further out. An analysis of the last hour's data can extend the range by x10, the last 100 hours by x100, the last 10,000 hours (416 days) by x1000.

Military installations will probably do this, Class A starports or those on high alert may as well, but it is rare for anyone else to bother since it requires computer resources and man power.

yags/starships/sensors.txt · Last modified: 2015/02/04 22:40 (external edit)