Alcubierre and Natario developed their warp drives spacetimes using the Arnowitt-Dresner-Misner ADM formalism considering the lapse function alpha always equal to 1. Recently Barak Shoshany and Ben Snodgrass considered the possibility of warp drive spacetimes in which the lapse function alpha is different than 1 in very special geometric cases and we arrive at very interesting results:In order to travel to a"nearby" star at 20 light-years at superluminal speeds in a reasonable amount of time in months not in years 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 1048 which is 1.000.000.000.000.000.000.000.000 times bigger in magnitude than the mass of the planet Earth which is "only" proportional to the factor1024!!.The lapse function allows more ffectively the negative energy density requirements when a ship travels with a speed of 200 times faster than light using the Shoshany-Snodgrass analysis. We reproduce here the Shoshany-Snodgrass analysis to the Natario warp drive spacetime with zero expansion.