  The conservation of the energy flux in turbulent jets that propagate in the
interstellar medium (ISM) allows us to deduce the law of motion when an inverse
power law decrease of density is considered. The back-reaction that is caused
by the radiative losses for the trajectory is evaluated. The velocity
dependence of the jet with time/space is applied to the jet of HH34, for which
the astronomical data of velocity versus time/space are available. The
introduction of precession and constant velocity for the central star allows us
to build a curved trajectory for the superjet connected with HH34. The bow
shock that is visible in the superjet is explained in the framework of the
theory of the image in the case of an optically thin layer.
