I never could figure out how Impulse Engines worked on Star Trek - I only knew they didn’t hold a candle to Warp Drive.
But given where we are today, just having sub-light Impulse Engines isn’t all that bad, and I’d LOVE to see it put into use.
I want one for my Road King!
There was an article here the other day where someone hypothesized that a ship with warp capabilities could be built.
http://www.space.com/17628-warp-drive-possible-interstellar-spaceflight.html
A quick internet search turns up a rocket science term known as "specific impulse," which has dimensions of seconds; this somewhat enigmatic dimension expands into "pound per pound per second" or
Here the numerator represents "pounds of thrust" and the denominator represents "pounds per second of fuel consumption."
Specific impulse is a single catch-all parameter for measuring the value/quality of a rocket engine and its fuel supply. The higher the specific impulse, the longer the engine will generate a particular thrust level on the same quantity of fuel.
"Impulse" is also an engineering quantity. It's dimensions are force·time, or lb·sec in the units used above; these are also the units of momentum. Interestingly, these dimensions are identical to m·v, mass times velocity, which relates to the amount of mass ejected from a rocket engine times the velocity at which the mass leaves the engine.
Anyway, I've always assumed (as a long-ago avid viewer of ST-TOS) that "impulse power" or "impulse engines" were classical rocket engines, although probably using some energy source far in advance of the chemical reactions we have mostly used in earthly space programs over the years.
"Warp Drive" seems to be based on some sort of bending or twisting of the space-time continuum, and thus is not limited by the speed of light. I remember reading long ago that "warp factor W" meant the speed of light times two raised to the power of W:
Thus when Captain Kirk called out "Warp factor 7 Mr. Scott" he was telling Scotty to make turns for 128 times the speed of light.