Just to bring the inevitable pedantry, you'd want to consider the cross-sectional surface area rather than the volume, and hitting the gravity well of a planet

Just to bring the inevitable pedantry, you'd want to consider the cross-sectional surface area rather than the volume, and hitting the gravity well of a planet may turn out to be indirectly fatal too. So while I agree it's still probably very small numbers I think you may be overcooking it.