Junghalli wrote:I can't do the math myself, but I'm pretty sure that orbital mechanics is highly deterministic, so as long as you had a good track on the ships you could plot out their courses fairly precisely. Somebody with more knowledge about the subject can probably address it better though.
That's the problem right there. Sure, anyone can see an intense IR signal from Pluto. But as most of the posts in this thread have been discussing, you might not be able to see what kind of source the signal is coming from, or what it's trajectory is, or how many ships are producing it: you'll see a few shining pixels. You need a certain level of resolution to figure out detailed information. Check out Mike's optical calculator.
But the enemy still sees a bunch of rockets headed toward a critical installation. He'd be an idiot to just brush that off. Maybe you could get him wondering about how to divide his forces since he doesn't know where the attack will come, but that gets into a second issue:
The problem with decoys in general is that you can deduce a ship's mass from how fast it's accelerating and how much energy is going into the drive plume. The decoys all have to be the same mass as your ships, and the same engines as your ships, in which case you probably almost might as well make them ships as they'll probably cost a good chunk of the cost of a ship. If you can send decoys off to "attack" twenty of the enemy's bases to confuse him, for that kind of money you could probably have built real ships and attacked 10 of his bases for real instead of just one.
You aren't understanding decoys. The idea is a small drone with a powerful IR emitter, not an actual spaceship. At a certain level of technology, you could even make an IR lamp strong enough to swamp the signal from the ship's engines, the same way you wouldn't be able to see a flashlight's signal if it was pointed at you from the direction of the sun.
Also, what if there are many independent and non-belligerent powers in this solar system? How would you know that the fleet being launched is even an attack fleet at all? Suppose Major Power A is attacking Minor Power B in retaliation for pirate raids or whatever, but an outpost for the neutral Major Power C sees one of the decoys pointing at nothing, and through computer or human error, thinks it's a fleet heading for them? There could be considerable uncertainty of this type.