Have you ever wondered about the powerplant behind Federation Starships ? Most recently that the author has heard, the typical starship uses something called a nuclear vortex engine. Nuclear vortex engines (NVE's) are extremely powerful. A nuclear vortex engine is just like a regular vortex engine except that it's nuclear in nature. A vortex engine works with vortex forces. Gas is burned in a vortex outside of the engine itself. Vortex forces feedback through the hot gas to the engine exhaust point in order to propel the engine. The efficiency is gained by shaping the gas output for maximum burn efficiency. The engine exhaust barrel can be rifled to spin the gas into a vortex. Many star-craft use some form of vortex engine.
Some older spacecraft use nuclear pulse-jet engines.
A pulse-jet engine makes use of an acoustic wave within the engine in order to compress gas.
The author managed to make a starfleet aquaintance by developing his own vortex engine. Apparently developing a starship engine is a hallmark to having the technical expertise to be considered for inclusion in the federation. A vortex engine is a stepping stone to a starship engine. Apparently the author's engine, primitive as it was, caught the attention of someone at star fleet. The author was treated to a day onboard a real starship.