  (Abridged) Most massive protostars exhibit bipolar outflows. Nonetheless,
there is no consensus regarding the mechanism at the origin of these outflows,
nor on the cause of the less-frequently observed monopolar outflows. We aim to
identify the origin of early massive protostellar outflows, focusing on the
combined effects of radiative transfer and magnetic fields in a turbulent
medium. We use four state-of-the-art radiation-magnetohydrodynamical
simulations following the collapse of massive 100 Msun pre-stellar cores with
the Ramses code. Turbulence is taken into account via initial velocity
dispersion. We use a hybrid radiative transfer method and include ambipolar
diffusion. We find that turbulence delays the launching of outflows, which
appear to be mainly driven by magnetohydrodynamical processes. Magnetic tower
flow and the magneto-centrifugal acceleration contribute to the acceleration
and the former operates on larger volumes than the latter. Our finest
resolution, 5 AU, does not allow us to get converged results on
magneto-centrifugally accelerated outflows. Radiative acceleration takes place
as well, dominates in the star vicinity, enlarges the outflow extent, and has
no negative impact on the launching of magnetic outflows (up to M~17 Msun,
L~1e5 Lsun). The associated opening angles (20-30 deg when magnetic fields
dominate) suggest additional (de-)collimating effects to meet observational
constraints. Outflows are launched nearly perpendicular to the disk and are
misaligned with the initial core-scale magnetic fields, in agreement with
several observational studies. In the most turbulent run, the outflow is
monopolar. We conclude that magnetic processes dominate the acceleration of
massive protostellar outflows up to ~17 Msun, against radiative processes.
Turbulence perturbs the outflow launching and is a possible explanation for
monopolar outflows.
