  Current rocket technology can not send the spaceship very far, because the
amount of the chemical fuel it can take is limited. We try to use dark matter
(DM) as fuel to solve this problem. In this work, we give an example of DM
engine using dark matter annihilation products as propulsion. The acceleration
is proportional to the velocity, which makes the velocity increase
exponentially with time in non-relativistic region. The important points for
the acceleration are how dense is the DM density and how large is the
saturation region. The parameters of the spaceship may also have great
influence on the results. We show that the (sub)halos can accelerate the
spaceship to velocity $ 10^{- 5} c \sim 10^{- 3} c$. Moreover, in case there is
a central black hole in the halo, like the galactic center, the radius of the
dense spike can be large enough to accelerate the spaceship close to the speed
of light.
