(Poisson & Israel 1990)

Ingoing and outgoing
fluids, if they drop through the inner horizon,
must drop into causally separated regions of spacetime.
To do this, they must exceed the speed of light relative to each other,
which is impossible.
Feedback loop:
Why does gravity accelerate ingoing and outgoing fluids in opposite directions?
Result: Mass inflation | |||||

RN Penrose diagram |

Mass inflation can lead to a null singularity along the Cauchy horizon