Thruster blocks increase your ship's thrusting capabilities, allowing it to accelerate and decelerate in a smaller amount of time. The more total mass your ship has (including the thrusters!!), the larger the amount of thrusters you will need to get the same results.
They do not increase your maximum speed though, that value can be configured in your server.cfg, found in the StarMade root folder, it is 50 km/h (13.89 block/s) by default.
Thrusters benefit from grouping the way most blocks do, their performance is based on the cubic size of a whole section of thrusters, so the most block-efficient section would be one that goes along three edges of a cubic shape. (screenshot pending)
|Defence||SD Shield Disperser • 0C Cloaker • 10x RadarJammer|
|CPU's||Weapons Computer • SD KB Missile CPU • SD-BB Missile Computer • D1000 Missile CPU|
|Weapons||AntiMatter Cannon • 16px SD KB Missile Array • 16px SD-BB Missile Array • D1000 Missile Array|
|Power||SD pc1.3 Power Tank • 16px SD Hct xm3.4 Power •|
|Construction Materials||16px Hull • 16px Hardened Hull •|
|Ship Building||Gravity Unit • Hyperflux Coil Thruster •|
|Misc||16px SD Docking Unit • 16px ID List • Faction Module • 16px Death Star Core •|