Arcing through the hazy air above California, this is the incredible sight of a scramjet as it flies at six times the speed of sound. The experimental aircraft set a record for hypersonic flight, blazing through the air for more than three minutes at Mach 6, or more than 4,500 mph. The X-51A Waverider scramjet was released from a B-52 bomber last week before its engine took it to Mach 6 and it flew...