HOUSTON — A warp drive to achieve faster-than-light travel — a concept popularized in television's Star Trek — may not be as unrealistic as once thought, scientists say.
A warp drive would manipulate space-time itself to move a starship, taking advantage of a loophole in the laws of physics that prevent anything from moving faster than light. A concept for a real-life warp drive was suggested in 1994 by Mexican physicist Miguel Alcubierre; however, subsequent calculations found that such a device would require prohibitive amounts of energy.
Hmm, so the new and improved warp engine would only require the mass energy of Voyager 1 - 722 kilograms according to Wiki. Or less if the oscillation caveat is true.
IIRC fusion of hydrogen to helium liberates about 4% of the mass into energy, so that means a fusion engine is only 4% efficient, and would require 25 x 3/4 ton = 19 tons of hydrogen. A mini-black hole is over 50% efficient, so that is why the Romulans power their starships with singularities (micro-black holes). Matter-anti-matter is 100% efficient which is why Klingons and the Federation uses same (dunno where they get the anti-matter however - I don't recall any reference in ST-TNG, Voyager or DS9, and to 'fess up I only watched part of the first season of Enterprise - I should turn in my Trekkie credentials ).
Anyway, this explains why starships need to get up to some sizeable velocity using impulse engines first before entering warp drive - even by effectively shrinking the distance to the destination by warping spacetime, you still need to traverse a certain percentage remaining, and thus the faster you are going when you enter warp, the sooner you'll get there. Of course, certain battle maneuvers such as warping just a few kilometers on the other side of an enemy only require thruster velocities before entering warp.
However the absolute best way to traverse huge distances (and time as well) remains traversing a wormhole..
You would need more energy to perform the operations.
A violation of the laws of physics themselves.
If you're speaking of the 2nd law of thermodynamics, aka no free lunch, yes it is true that a fusion reactor requires a certain amount of energy to run. However the net output far exceeds that amount of energy.
Remember Einstein's E = MC^2, which means the potential energy contained in the rest mass of an object is that mass multiplied by the speed of light (3 x 10^8 m/s) squared, which is enormous. So one kilogram of matter converted completely into energy would produce 9 x 10^16 joules or watt-seconds of energy, which is 25 billion kilowatt-hours of electric energy or 0.085 quadrillion BTUs (Quads). The total US useful energy produced by all sources (natural gas, coal, nuclear, electric, etc) for all uses (residential, commercial, industrial, transportation) amounted to 35.2 Quads in 2002. So that means it would take just 412 kilograms of matter converted entirely to energy, to power the entire US energy needs for the year 2002. That's about half a ton of something, or one really fat woman ..