There are many different phenomenological models describing the cosmological dark energy and accelerating Universe by choosing adjustable functions .
In this paper we consider a specific model of scalar tachyon field which is derived from the NSR string field theory and study its cosmological applications .
We find that in the effective field theory approximation the equation of state parameter w < -1 , i.e .
one has a phantom Universe .
It is shown that due to nonlocal effects there is no quantum instability that the usual phantom models suffer from .
Moreover due to a flip effect of the potential the Universe does not enter to a future singularity .