Forty-eight years ago this month, USAF Major Robert A. Rushworth flew the 100th flight test of the X-15 Program.  Piloting his 18th mission in the manned hypersonic aircraft, Rushworth achieved a maximum speed of 3,618 mph (Mach 5.34 ) in X-15 Ship No. 1 (S/N 56-6670).  The date was Tuesday, 28 January 1964.  Peak altitude attained during the 8 minute and 17 second flight was 107,402 feet.  Using a trio of aircraft, the X-15 Program would go on to register 199 official research missions between June of 1959 and October of 1968.  Bob Rushworth flew 34 of those missions; more than any of the twelve men who piloted the famed black rocket-plane.  Bob Rushworth had many notable experiences while at the controls of the X-15 including one episode where the nose gear deployed above Mach 4.2 and another where a main landing skid deployed above Mach 4.4!  Each time he was able to get the airplane back on the ground in one piece.  On a more positive note, Bob Rushworth flew the X-15 as fast as 4,018 mph (Mach 6.06) and as high as 285,000 feet.  For this latter achievement, Rushworth was awarded Astronaut Wings by the United States Air Force.