The problems for a manned reusable air asperated atmosphere flying aircraft from all I've found are huge even with todays tech. From what I've found amach 6 or 7 would look nothing like the artist concept Aurora I've seen, but heck the gov denies all.Lockheed skunkworks has confirmed deveopment begun on SR-72 mach 6 capable , but unmanned so not the same.Search X-43 and X-51 nasa test craft unmanned one use B-52 wing lauched mach 9 plus but don't really count,right? Blackbird still on top!(maybe, where's agent Scully?)