things to look for
1 waste heat from a fusion/fission/antimatter powerplant(thermal)
2 trail of Helium left behind as reaction mass(spectral)
3 radiation from fission/antimater powerplants(EM)
4 gravity warping of light as the ship passes between you and the background of stars for contra grav drives(motion detection)
5 using radar and ladar(active systems)
granted the stealth option gives a -4DM to cloak these
things to ponder
1 how long can a ship stay cold with no fusion plant running to add to stealth and still start up and attack(lying in wait)
2 how long does it take to start up the powerplant
3 how long could fuel be extended if the power plant was turned down to just run life support and sensors(life boat situation)
I'm figuring that you could extend fuel usage by running the powerplant at a lower level(power plant Z for a 1200 ton ship needing 48 tons for 2 weeks as a powerplant F for a 1200 ton ship which only needs 12 tons per 2 weeks)
there by extending the ships endurance by a factor of 4
all systems are still able to be used since a powerplant F is the smallest that can be used by a 1200 ton ship
Rikki Tikki Traveller said:
It also depends on how you think the thermal signature for the M-Drive looks.
Being a gravitic drive, it may not have much of a signature at all, so looking behind the ship would be no different than looking in any other direction.
Gravitic sensors would be another nice high tech thing to have. It might detect all those M-Drives (or artificial gravity if close enough) and help find those hiding ships.