Every image of this plane has a so-called "normal shock inlet," similar to the kind you see on an F-16, for example. These inlets are limited to the low superso

Every image of this plane has a so-called "normal shock inlet," similar to the kind you see on an F-16, for example. These inlets are limited to the low supersonic range. (Mach 1.4 is really pushing it.) So, it's very unlikely that this is a thermal issue, especially given that the F-16 cockpit seems mostly conventional. Far more likely is that abrupt area changes cause discrete shocks, each of which could merge into the "sonic boom" that the demonstrator is designed to alleviate. However, a simpler way to understand it is that, from a practical point of view, you basically want to be flying a needle to reduce the boom to its minimum possible volume.