  X-ray bursts are the thermonuclear runaway of a mixed H/He layer on the
surface of a neutron star. Observations suggest that the burning begins locally
and spreads across the surface of the star as a flame. Recent multidimensional
work has looked in detail at pure He flames spreading across a neutron star.
Here we report on progress in multidimensional modeling of mixed H/He flames
and discuss the challenges.
