I'm sorry to say that, but both of you are partially wrong.
Wolfpack is wrong in the part when he says about 100% clientside - thrusters are not 100% clientside, and NPCs handling is not, even if you are all alone. NPCs are processed by client, it's true, but information is still being sent to/from client. Even if you are fighting all alone. This isn't easy to notice if you have a fast network, cause processing this info won't require much serverside work. But if the network is not so fast, you might easily get connection lag.
DarkOddity is also right about thrusters influencing server speed when several players are in one place, one system. Yes, thrusting info is being sent to/from server, and yes, it does load server. Question is - how?
As you might know, the fastest servers are vanilla. Larger mod = more lags. It's inevitable truth: each new feature, each new item adds a little bit of lag, and each error, both reported and unreported, generates even more lag. Errors that flserver does not report are nearly impossible to track, cause I'll never know that they exist. Simple, eh? However, each of these errors would take up CPU power, and each will increase FLServer memory usage. CPU will complete its job, but memory will not free itself (this is why Win2003 might be preferable - better memory management). And this is why we are getting 100, 140, 180 Mb of memory eaten by FLServer after some hours of active play. Each new player logging in/out will add to memory usage -> cause of 16+ player lag should now be obvious. It is not thrusters, and not even related to actual gameplay.
Almost everything about the mod that could be done to reduce lag: was already done. Almost.
However, if someone will activate Discovery and then activate some other mods on top, this could easily cause server errors and increase lag.
As for normal NPC/pvp fighting, it's normal... will cause lag if it's massive, but it won't cause progressive memory-related lag like errors.
