  We investigate obstacles of superluminal "warp drive" travels from
interactions with interstellar matter and from curvature effects. The effect of
collision of interstellar dust particles and photons with the spacecraft will
all lead to a pressure proportional to the apparent velocity of the spaceship
$v_s$. The force exerted on the spacecraft from the curvature effect has two
non-trivial components. The radial and longitudinal components scales as
$v_s^2$ and $v_s^4$ respectively. The above obstacles become increasingly
important when the spaceship travels at high superluminal speeds.
