Man's Reliability in the X-15 Aerospace System 640608
History of X-15 performance reveals that the pilot, by unscheduled or unplanned inputs, enabled completion of almost twice as many flights as would otherwise have been completed on a routine basis. The prelaunch team (including the pilot) supported 92 successful routine launchings and overcame malfunctions to enable 10 additional launchings; 13 missions were unsuccessful because of team error. The maintenance crew was responsible for 6 failures out of 164 mission attempts.
A reliability point estimate of 0.84 for the X-15 personnel subsystem is derived from these comparisons.