The Fourth Industry Conference
NASA held the fourth and last conference on the progress of the X-15 program at the FRC on 7
October 1965. This conference was considerably smaller than the previous ones, with only 13 papers written by 25 authors. The FRC employed 18 of the authors, while four came from other NASA centers, one from the AFFTC, and the remaining two from other Air Force organizations. Approximately 500 persons attended the event. At this point, the program had conducted approximately 150 flights over 6 years.
By the time of the conference, the X-15 had essentially met or exceeded all of its revised performance specifications. The future would bring no additional altitude marks, and additional speed of less than a Mach number. For the most part, the government was using the X-15 as an experiment carrier, although X-15A-2 continued some additional aero-thermo-dynamic research. Jim Love noted that 10 pilots had used the three X-15s to accumulate almost 1 hour of flight above 200,000 feet and almost 4 hours at speeds in excess of Mach 4.
The follow-on experiments were taking on unanticipated importance. Love observed, "The use of the airplane as an experimental test bed is one of the most significant extensions in the research capability of the X-15 airplanes. They have been utilized to carry various experimental packages to required environments, obtaining measurements with these packages, and then returning the experiment and results to the experimenters… several experiments were installed on each aircraft for better flight utilization. For this reason, on the X-15-1 airplane, specially constructed [wing] tip pods and tail-cone box have been installed… to accommodate the experiments… Three experiments have been completed, five are in progress, and three more are planned for next year."
Love noted that "the X-15 program has never settled down to a routine operation because of the continued increase in complexity and the nature of experiments and research performed by each aircraft. This attribute is probably characteristic of research programs." The lack of routine, however, undoubtedly increased the cost of the program and placed a heavy burden on personnel to maintain safety.*230