%ADias, Óscar%AHorowitz, Gary%ASantos, Jorge%BJournal Name: Journal of High Energy Physics; Journal Volume: 2021; Journal Issue: 12 %D2021%I %JJournal Name: Journal of High Energy Physics; Journal Volume: 2021; Journal Issue: 12 %K %MOSTI ID: 10322654 %PMedium: X %TInside an asymptotically flat hairy black hole %XA bstract We study the interior of a recently constructed family of asymptotically flat, charged black holes that develop (charged) scalar hair as one increases their charge at fixed mass. Inside the horizon, these black holes resemble the interior of a holographic superconductor. There are analogs of the Josephson oscillations of the scalar field, and the final Kasner singularity depends very sensitively on the black hole parameters near the onset of the instability. In an appendix, we give a general argument that Cauchy horizons cannot exist in a large class of stationary black holes with scalar hair. %0Journal Article