Pulse Engine

Pulse Engine is a type of STL Engines that is used quite widely, however due to details of its construction and the way it works, it is usable only in a very specific situations, which makes it completely unusable for a wider audience. Thus limiting the technological progress it undergoes.
Pulse Engine uses a miniature fussion bombs detonated behind the ship to generate thrusts. It is used solely by the Terrain Federation long-range raid squadrons. It is highly inefficient in terms of rapid changes of course and acceleration, however it can become extremely useful when ships are supposed to quickly and efficiently achieve high speed and remain like that for a long time, without changing course.