Boeing NB-52A launching an X-15.  The oldest B-52 in existence, this is the third “A” model built.  This is one of two B-52s modified to carry the X-15 rocket plane.

X-15 #1 is carried aloft under the right wing of NASA's NB-52A on 17 September 1959 for its first powered flight.  Scott Crossfield is at the controls; in a few of minutes, he will fly the X-15 to a speed of Mach 2.11 and an altitude of over 52,000 feet.

Although a fire broke out in the engine compartment, Crossfield safely landed on the lakebed at Edwards Airforce Base.

Over the next nine years, the three X-15s made 199 flights.  They set speed and altitude records nearly every time they flew, expanding NASA’s understanding of flight in the hypersonic range.