  We consider the translocation dynamics of a polymer chain forced through a
nanopore by an external force on its head monomer on the trans side. For a
proper theoretical treatment we generalize the iso-flux tension propagation
(IFTP) theory to include friction arising from the trans side subchain. The
theory reveals a complicated scenario of multiple scaling regimes depending on
the configurations of the cis and the trans side subchains. In the limit of
high driving forces $f$ such that the trans subchain is strongly stretched, the
theory is in excellent agreement with molecular dynamics simulations and allows
an exact analytic solution for the scaling of the translocation time ${\tau}$
as a function of the chain length $N_0$ and $f$. In this regime the asymptotic
scaling exponents for ${\tau} \sim N_0^{\alpha} f^{\beta}$ are $\alpha=2$, and
$\beta =-1$. The theory reveals significant correction-to-scaling terms arising
from the cis side subchain and pore friction, which lead to a very slow
approach to $\alpha =2$ from below as a function of increasing $N_0$.
