  A GRMHD model of disk outflows with neutrino-driven mass ejection is
presented. The model is used to calculate the structure of the outflow in the
sub-slow magnetosonic region and the mass loading of the outflow, under
conditions anticipated in the central engines of gamma-ray bursts. It is
concluded that magnetic launching of ultra-relativistic polar outflows is in
principle possible along low inclination field lines (with respect to the
symmetry axis), provided the neutrino luminosity is sufficiently low,
$L_\nu\simlt10^{52}$ erg s$^{-1}$.
