All entities have a property called "scan class" which, wait for it.. ..bit longer... determines, inter alia, whether - and how - they appear on the scanner. The scan class of an entity determines how the AI of any other entity will react to it. So the method of hiding an NPC ship is it give it an unusual scan class. There ae two entities in the system that have unique scan classes, that is to say, there can be only one of them. One of those is the sun.
So, if you can't alter the scan class of the player ship, the way to hide it from NPCs is on the other side of the interaction: nobbling the AIs that should react to the presence of the player ship. (I believe you have some prior interest in this topic.) It's possible, but it's not as convenient/elegant as flipping one variable. Analogous to active jamming, rather than power-down or silent running.
OTOH, get behind the planet or sun, no-one else ever goes back there. But... what are you going to do back there? Just hit the pause button if you need to answer nature's call, no need to hide the player ship when you have the ability to stop time.
It raises a further question, though. There are two (non-OXP) ways of detecting/recognising things in Oolite.
1) Via the scanner.
I've no experience of how other games tackle this, but it seems to me that our lore insists that every ship is fitted with an ID transmitter which emits ID (picked up within the range of the scanner). And my ship's computers can also determine whether the object is targetting my ship.
So to render my ship invisible to scanners I presumably have to "pull the plug" which turns everything off (even life support!). Or have an illegal switch attached which just neuters the ID transmitter (but my "invisible" powered ship might then still be blocking the inexistent NPC Torus drives - and thus even show up on their scanners but without ID - as an alien/Thargoid or some such).
I'd have thought that there has to be more to this. How much power has to be flowing through my ship to disable Torus drives? Presumably it is not power but the operation of some piece of equipment which has this effect (compare Rock Hermits whose mass blocks hyperdrive but whose electrics don't block the Torus drive).
And I'm sure that there must be considerations which I've missed... (eg. relations to a certain unnameable device?)
2) Via eyeballs (either through windows or viewscreens).
When one gets close enough to an invisible ship and can see it, one presumably realises that it is not an asteroid or part-destroyed derelict.
This requires proximity and a clear line of sight.
Might this correlate to an ability to recognise that a short-range laser shot would actually hit rather than miss? And is there any recognition of this in our game code?
3) OXPs
Leaving aside the cheats, we have Telescope, GalCop Missions' Range Finder MFD and the various Beacon finders (Rock Hermit Locator, Mining Beacon Descrambler, Navigation Beacons MFD). No great thoughts about these yet...
There's some core equipment that provide some of this:
1. The Cloaking Device, which renders the player (almost) invisible on the view screen and scanner.
2. The "Military Anti-Scanner Countermeasures (MASC'M)", otherwise known as the Military Jammer (EQ_MILITARY_JAMMER). I think the GalTech Escort Fighter makes use of this - in my play sessions, I will occasionally be up against one that I can see through my viewscreen, but can't see on my scanner. I feel obliged to point out, though, that the Military Jammer is an old experimental item which may or may not break into thousands of tiny shards when actually put to use.
I've always thought that powering down in an asteroid field could be a valid tactic in some scenarios. I think I even asked a question about it a long time ago.
