Re: Wow!
They have already run the pre-cooler at ground level (four years ago), so some testing has been done already. (Note that they heated the incoming air up to the temperatures they're expecting at Mach 5).
To my mind this shows that they have demonstrated a working model at working speeds and simulated altitudes, and given that ESA have signed off on the testing so far, they agree. And they, after all, are rocket scientists.
Biting the hand that feeds IT
