Different technology to Concorde, the XB-70 was a “wave rider” using compression lift to reach the required range - hence the fold-down wingtips.
“As the competition evolved, North American exploited an aerodynamic advance that gave it the determining edge. A supersonic aircraft could have its lift-over-drag ratio increased by positioning its wing to take advantage of the pressure field that occurs behind the shock wave generated by the protruding fuselage. In North American’s design, this phenomenon—called compression lift—provided a 30 percent increase in lift with no drag penalty. Compression lift appeared to contravene the engineering rule that you never get something for nothing, but it worked.”….
