They are working on the magnetohydrodynamic (MHD) energy bypass engine.

Basically, it uses MHD to extract energy from the air stream, which can keep the inlet temperatures for a turbojet manageable well beyond the normal limit of about Mach 3. They are claiming Mach 7.

Still, I’d like to see the first A in NASA doing more non-space related work, as this is clearly intended to be used with a booster.