As the SR-71 Blackbird neared retirement, rumors spread of a faster successor: a classified hypersonic reconnaissance aircraft called the SR-91 Aurora, said to exceed Mach 5 or even Mach 6. The name traces to a 1985 defense budget document, though former Lockheed Skunk Works director Ben Rich later indicated Aurora was a budget code name tied to the B-2 stealth bomber. Sonic booms over Southern California and a 1989 North Sea sighting fed the st…