"Resonance"is probably the best one-word explanation, but the interesting details are in how the version 2 downcomer design makes the ship more prone to pogo oscillations, what the most likely failure modes are, and how they could be addressed in the short term and long term.
Wish there was a tl;dr
Resonance. Old problem, new rocket.
"Resonance"is probably the best one-word explanation, but the interesting details are in how the version 2 downcomer design makes the ship more prone to pogo oscillations, what the most likely failure modes are, and how they could be addressed in the short term and long term.