In VB6 Aurora, a ship always has its max same thermal signature even when not moving. The fleet can be set to a lower speed if desired, which reduces the signature, but that isn't directly related to movement. Part of the rationale was that a ship would need to have engines warmed up to dodge incoming fire.
However, it doesn't seem realistic that a stationary ship and one moving at full speed should have the same thermal signature so I am going to change that for C# Aurora. The 'dodge argument' doesn't really hold given the instant acceleration rates of TN ships. I'm just debating between two options:
1) If the ship has no movement orders, it has zero thermal signature. Otherwise, the signature is (current speed / max speed) * max thermal signature. This is the simplest to implement and easiest to understand. The current movement orders condition would apply regardless of whether the order at that point involved movement, so a freighter in transit and one loading cargo are both 'moving'.
2) A ship without orders has some baseline thermal output, probably based on 1% to 5% of size in hull space, so using 5% a 10,000 ton ship would have a thermal signature of 10 (200 HS x 5%). I could make a distinction for commercial but probably easier to leave as is on the basis that some commercial functions (mining, terraforming, harvesters) would generate heat and even freighters would have less thermal shielding than similar size warships. This removes the idea of being invisible to thermal sensors when motionless, but it is still a low signature compared to VB6.
This has some implications for scouting, as there could be large stationary alien warships that you will only detect if they move or activate sensors, or if you activate sensors.
