Simulating Lateral H/He Flame Propagation in Type I X-ray Bursts

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.