`  == Possible cons? ==  *) What are the failure scenarios for the pre-cooler?  How gracefully/gracelessly will the engine fail?  *) Is there a critical point in the mode switch where the rocket mode (and the various cycles that are meant to sustain propellant transport within the system) might not ``bite``? Again, what is the failure scenario?  I would be happy to see an aeronautical engineer comment on this, even though public sources on how this engine would go arse-up are probably non-existent... (don't get me wrong, I wish this engine to succeed.)  `