Recently there has been a great deal of confusion regarding which ship classes may accommodate these engines. These engines are balanced for the battlecruiser class only. This means that their use on a cruiser reduces thrust speed by 10 and increases impulse speed by 10.
The engine is also completely ineffectual on Battleships.
Therefore, at this time, the engine is only to be mounted on Battlecruiser class ships, in addition to the Bustard civilian carrier.