NASA funded a study of advanced physics propulsion, including the Alcubierre Warp Drive, under their Breakthrough Propulsion Physics program, from 1996 through 2002. Some of the results of that study were published in Frontiers of Propulsion Science. Marc Millis, who headed up the Breakthrough Propulsion Physics program, went on to found the Tau Zero Foundation, another organization studying interstellar flight.
As for your comment: "It is not a real scientific theory as AFAIK it has not been published in any reputable scientific journal:" Let's take a look at: The quantum inequalities do not forbid spacetime shortcuts in Physical Review, or Alcubierre's paper: The warp drive: hyper-fast travel within general relativity in Classical and Quantum Gravity.
I also recommend you see Dr. Harold White's paper: Warp Field Mechanics 101 published by the Johnson Space Center. Work by Dr. White and others indicates that the energy requirements for a 'warp drive' may be drastically reduced from Dr. Alcubierre's original estimates.
Edited to add: Yes, I am aware of Konstantin_Tsiolkovsky's rocket equation.
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