(Spaceships) Implictions of the sensor rules.

[Fred Brackin]

Questions concerning how far away you should set your FTL boundary and general defense of an inhabited system came up recently in other threads and I've been reviewing the Spaceships rules and have finally organized my thoughts.

Let's begin by walking through a simple detection scenario. We'll have thesM+15 space station that orbit above a major world (and which costs hundreds of billions if not trillions of $) trying to find an SM+6 scout ship that is doing inteligence-gathering. The TL is 10, the maneuver drive is standard of "cold" Reactionless and the most common power plant is fusion.

Technically, we begin calculations with the Systems Operation (Sensors) Skill of the person performing that function for the station. Hoever, almost by defintion we know that if the orgaization running the station is "professional" their sensors guy is at least Skill-12 but how much higher is reasonable is a matter of opinion. so we'll defer that question.

So we have Skill+ SM of target (SM+6) + time spent (one half hour +5) and Telescopic Vision level of the Enhanced Sensor array (+16). So far ll those plusses look good but then we figure in possible range penalties and 75 AU (the number Spaceships uses sometimes for the FTL boundary) and we get a -75.

So we were +27 but are now -48. There's more plusses though. We get a +10 for "in plain sight" that applies most of the time (but not if you have an opperating cloaking system). Then there's a +24 for "sillhoetted against deep space" that also applies most of the time.

Finally, there is IR signature and counter measures. That's a +7 for the Fusion power plant and what could b a -10 for a Cloaking system and a -8 for Stealth. We'll assume no Cloak and the Stealth is negated for any IR signatures of _5 or above.

That leaves us at Sensor Ops -7 to spot this scout ship at 75 AU. How close does the scout need to be for you to rollv. base skill. That appears to me to be c. 2 AU using numbers from Spaceships.

This is for a relatively rosy scenario for the defense too. If the scout jumps in with the local star between himself and the station the stations 3 billion $ sensor suite can't see him at all. Then if the scout comes around the star so closely he's never seen with deep space as a background that changes a +24 to a +2 for coming at you with the star as a backdrop.

Taht -22 takes you from rolling Skill at 200 milion miles to rolling v. base skill at 4000 miles. (-43)

Things could be worse than that too. If the scout is desgned with an ausiliary power plant such as fuel cell or solar the IR signature modifier drops from +7 to +4. More importantly it sllows for Stealth measures that could give another -8. A total of -32 which makes your distance for base Skill 250 miles.

If he has a Cloak that take soff another -20 (-10 for the Cloak and you lose that +19 for In plain sight). That puts you at 200 yards. At least the scout probably can't land infiltrators on the station. Keepign him off your planet might be a lsot cause.

So you need not only this trillion $ space station to detect at c. 2 AU you need soemthing like a ring of other (perhaps cheaper) stations in a closer solar orbit to protect against that "coming at you from out of the Sun" trick. Extending your detection range out into the outer solar system is probably prohibitive.

I recommend placing your FTL boundary at no more than 10 AU. You should get good detection of real warships that far out. Putting it at 10 AU still makes it a 9 day run at 1G continuous.

Also, please will someone else check the math? I was juggling Speed/Range table numbers in my head mostly.