Warp Drives are solutions of the Einstein Field Equations that allows superluminal travel within the framework of General Relativity. There are at the present moment two known solutions: The Alcubierre warp drive discovered in $1994$ and the Natario warp drive discovered in $2001$. However the major drawback concerning warp drives is the huge amount of negative energy density able to sustain the warp bubble.In order to perform an interstellar space travel to a "nearby" star at $20$ light-years away in a reasonable amount of time a ship must attain a speed of about $200$ times faster than light.However the negative energy density at such a speed is directly proportional to the factor $10^{48}$ which is $1.000.000.000.000.000.000.000.000$ times bigger in magnitude than the mass of the planet Earth!!. With the correct form of the shape function the Natario warp drive can overcome this obstacle at least in theory.Other drawbacks that affects the warp drive geometry are the collisions with hazardous interstellar matter(asteroids,comets,interstellar dust etc)that will unavoidably occurs when a ship travels at superluminal speeds and the problem of the Horizons(causally disconnected portions of spacetime).The geometrical features of the Natario warp drive are the required ones to overcome these obstacles also at least in theory. \newline Some years ago the American physicist Harold Puthoff published a very interesting work in the Journal of the British Interplanetary Society.He theorized about the possibility of the modification of the spacetime geometry by arbitrary advanced civilizations able to generate the so-called metric engineering and such a modification would be supposed to "allow" the propulsion of spaceships at superluminal velocities.However Puthoff used only diagonalized metrics for his analysis and he even quotes the Schwarzschild metric.In this work we reproduce the Puthoff analysis for the Natario warp drive spacetime and due to the fact that the Natario warp drive is a non-diagonalized metric due to the presence of both the shift and Natario vectors our results are different than the ones obtained by Puthoff.However his idea of a spacetime metric engineering able to distort the spacetime geometry "allowing" superluminal interstellar spaceflight is perfectly possible.