The LockheedX-17 was a three stage solid-fuel research rocket to test the effects of high mach atmospheric reentry. The first stage of the X-17 carried the rocket to a height of before burning out. The rocket would then coast on momentum to about before nosing down for reentry. The second stage engine would then fire before jettisoning and igniting the third and final stage. On April 24, 1957, an X-17 reached a speed of at Patrick AFB.E. Emme, ed., Aeronautics and Astronautics, 1915-1960, p. 85. Ultimately the X-17 would be travelling towards earth at up to Mach 14.5.