Warp Drives
are what makes starships go faster than light and energy. Warp speed is fast. But how does the engine really work?
   The warp drive is perhaps the most complex part on a starship. Without it, getting across galaxies would be functionally impossible. Perhaps our biggest obstacles to inhabiting other solar systems as envisioned by Star Trek are the physical limitations of space and time.
    Warp travel is anon- "propulsive" technology. It moves the ship, hut it doesn't propel it in any particular direction. ,,Impulse power" operates in the same way as twentieth-century rocket technologies and is thus propulsive with inertial effects; that is, once you turn off the rockets you keep moving forward.
    Warp drive does not share propulsive effects or the additive advantages of inertia. Since it operates by creating a separate subspace field, you could instantly stop a ship under warp drive if you could kill the subspace field rapidly enough.
    The "stress-energy tensor" mathematically describes each point in four dimensional spacetime it is linked to the mass and energy distribution of normal space (nonsubspace). This distribution and flow of the stressenergy of matter is dependent on the surrounding stress-energy tensor, which defines the curvature of four-dimensional space-time. Matter-energy within the warp (or subspace) from the matter- energy outside of the field due to the violent change in the frame of reference produced by the plasma stream within the warp field coils in the nacelles.
    This violent change in the local stress-energy within the subspace coils would rip the fabric of space except that nature produces a subspace field around the event to gradually fix the tear. This in effect spreads the event over a general area in a subspace field that looks similar to a gravity field originating from a gravity well and protects the spacetime continuum. It can be manipulated into asymmetric propulsive fields.
    Matter within the  field is removed from normal space and anchored to the frame of reference of subspace. The effect of this is to allow matter within the field to almost completely bypass relativity's obstacles and allow phenomena such as FTL travel. The limiting factor is the energy required to disassociate the matter from normal space. This energy must be continuously applied or the subspace field gradually dissipates and brings the matter back into normal space.
    Subspace is a field that defines a particular frame of reference at all points in known space. It is composed of an infinite number of cells like a honeycomb. A ship entering warp uses subspace so as to keep its frame of reference regardless of speed. The asymmetrical peristaltic warp field propels a ship by pushing against each anchored reference frame of subspace. The first field coil anchors the ship to the occupied position in subspace, then passes the field along to the next coil along with its anchored position in subspace, and so on down the nacelle.
    It is not necessary to add extra nacelles to increase warp speed. Once a warp field is established, it takes pure engine power to push toward warp 10. The nacelles create the warp field and sustain it. The number of nacelles is determined by the size and mission of the starship, although three nacelles is a very unstable design (the U.S.S. Tritium Warp 4 Cruiser, designed with three nacelles, was canceled in 2155 due to severe instability during warp flight). Two extra nacelles made the Constellation-class starships very agile.
    Before the current environmentally friendly, movable warp coils on the Intrepidclass starships, ships that went faster than warp 5 polluted space with localized "rifts." The Voyager can safely reach a top speed of warp 9.975 for short periods. The new warp drive technology is top secret, but it has been publicly speculated that the drive could eliminate the risk of pollution because of the orientation of the warp fields (nacelle position), new materials, the configuration of the warp coils in the nacelles, or by computer manipulation of warp formula to synchronize and shape the warp fields.
    Dedicated warp coils may produce a subspace distortion field around the nacelles to facilitate moving them quickly. Gravimetric force fields may also be used to move the nacelles.

Info is from some books