Fusion overburn
A fusion overburn was a procedure, considered quite dangerous, in which an impulse engine's power output was pushed past the normal maximum safety level in an attempt to generate a great amount of thrust.

In 2153, Sim, a clone of Commander Tucker, came up with the idea of using a fusion overburn on two s, connected to  via grappler cables, to tow Enterprise out of a polaric field in which it had become trapped. Although the idea was met with a certain amount of skepticism, the plan eventually worked, and Enterprise escaped. ()

Propulsion technology