True stealth is impossible. What about subterfuge?

toughsf.blogspot.com/2016/03/stealth-in-space-is-possible-ii.html Has some interesting approaches to deal with lack of true stealth...

"Stealth" in modern combat is always subterfuge. Arguments against "stealth in space" tend to focus on complete invisibility, which is not really possible on Earth, either. Unless you hide behind something, of course, but space is rather short on things to hide behind (not that you can't do it, if an opportunity arises). Stealth in modern warfare is always about subterfuge. You can't make your warship disappear, but with the right tricks you can make it appear like something it isn't. At least one F-117 found out the hard way that a goose zipping around at subsonic speed and making repeated passes over a radar site is a little conspicuous.  

For instance, let's say we've got a heavy ship with a small heat signature (about what you can find out by observing it). Is it a freighter, a drone/missile carrier, or a dreadnought running on a secondary reactor? Sometimes, you can figure this out by keeping track of the ship's point of origin and destination. However, this requires information which may not be as easily obtained as the ship's thermal signature. This kind of subterfuge is a strategic move, so outside COADE's gameplay scope, but is a very possible thing.

Tactical stealth isn't really possible in space, but keeping up a strategic guessing game very much is.

Yes, but if you send your whole dreadnought fleet after a merchant with an old reactor in the cargobay and spare radiators bolted on, which promptly surrenders just short of engagement range, then you may find out they're out of dV to catch an actual dreadnought, which in the meantime snuck in running cold and received only some patrol craft as a welcome committee. Indeed, I would expect a delta-V gambit to work really well if you can fool the enemy into thinking you're a craft with much less endurance than you actually have (freighters loaded with spare propellant in the cargobay may be especially good here). 

It could also be done on an interplanetary scale, where you send a decoy force onto one planet, and once the response is under way, send your real force somewhere else, so there's no way in hell the response force could catch them in time, nevermind the fact they're not likely to have dV for such a drastic trajectory change, anyway. 

This is exactly the point of subterfuge. A hunter ship closes in on the supposed merchant... upon which it deploys its main radiators and opens up with GW-class railguns. Whether you can commit your main fleet after that is a matter of the orbital situation, but it probably won't get as good an intercept as the hunter did. Enough tonnage to take down a merchant is, typically, not enough tonnage to take down a dreadnought. Even if you treat every ship as a threat, you need to assess how much a threat it is. Especially if, as seems to be the case in COADE, you don't have all that many ships to work with in first place.

It is a gamble, and of course your bluff might be called, but the payoff can make it worth the effort. It all depends on the strategic situation. For instance, if your end goal is the capture of an entire planet's Hill sphere, surrendering (nobody sane would actually attempt to fight with the decoy fleet) a few freighters as decoys wouldn't matter, since if it works out, you'll have them back soon enough, together with anything they decoyed. That's assuming the enemy doesn't try to scuttle everything, which they may, but scuttling a spaceship without killing its crew is a rather though job to do on a short notice. Of course, if it doesn't work out, you lose everything, but that's the case with any interplanetary fleet operation.

The goal of a decoy operation is to get the enemy to waste delta-V. If you then proceed to knock out their refuelling capability (a perfectly viable target for this kind of thing), then you have an enemy battle fleet and their prizes dead in space, with not enough prop between them to make a retreat (high velocity intercepts are expensive, so is getting back from one). Assuming your own dV management is up to snuff, and the enemy doesn't pull any surprises out of their hat, you end up at a huge advantage and may even be able to force a surrender with minimal combat. Of course, this is just a single scenario. 

Of course, that brings us to another kind of "stealth" in space: landing on a planet/moon. A landed vessel can be made effectively invisible from space, so if you can get it there unnoticed (or build it planet/moonside in first place), then you have a perfect way to surprise any would-be interplanetary invaders.

Actually, many modern warships use "stealth" designs, which tend to reduce their radar returns quite a bit. So you can very much pretend that you're sailing in a much smaller boat than you actually are, though in surface ship warfare the reduction in detection range would probably be more important. Of course, in real world, air recon is the big problem. Nobody goes in without checking things from the air first, if they can help it. In space you have no such luxury.