  Within the framework of tachyon inflation, we consider different steep
potentials and check their viability in light of the Planck 2015 data. We see
that in this scenario, the inverse power-law potential
$V(\phi)=V_{0}(\phi/\phi_{0})^{-n}$ with $n=2$ leads to the power-law inflation
with the scale factor $a(t)\propto t^{q}$ where $q>1$, while with $n<2$, it
gives rise to the intermediate inflation with the scale factor
$a(t)\propto\exp\left(At^{f}\right)$ where $A>0$ and $0<f<1$. We find that,
although the inverse power-law potential with $n\leq 2$ is completely ruled out
by the Planck 2015 data, the result of this potential for $n>2$ can be
compatible with the 95\% CL region of Planck 2015 TT, TE, EE+lowP data. We
further conclude that the exponential potential
$V(\phi)=V_{0}e^{-\phi/\phi_{0}}$, the inverse $\cosh$ potential
$V(\phi)=V_{0}/\cosh(\phi/\phi_{0})$, and the mutated exponential potential
$V(\phi)=V_{0}\left[1+(n-1)^{-(n-1)}(\phi/\phi_{0})^{n}\right]e^{-\phi/\phi_{0}}$
with $n=4$, can be consistent with the 95\% CL region of Planck 2015 TT, TE,
EE+lowP data. Moreover, using the $r-n_s$ constraints on the model parameters,
we also estimate the running of the scalar spectral index $dn_{s}/d\ln k$ and
the local non-Gaussianity parameter $f_{{\rm NL}}^{{\rm local}}$. We find that
the lower and upper bounds evaluated for these observables are compatible with
the Planck 2015 results.
