One of the important general claims of the original prospectus for
the program was that it would stimulate aerospace research and development.
A measure of how well this claim was realized is seen in the following
tabulation of technical documents:
Principal Technical Documents Associated with the X-15 Program
Development of X-15 system and supporting R and D
Flight test results
General research inspired by X-15 program
The total production of over 700 technical documents is equivalent to the
output of a typical 4000-man federal research center for a period of some
2 years. Of special interest and significance are the 200 papers reporting
general research inspired by the X-15. These latter papers were identified
by personal knowledge of various members of the X-15 team and by contacts
with-the authors. They are reports of research that would not have been
undertaken had it not been for the inspiration provided in one way or
another by the X-15. Thus we see statistical confirmation of the massive
stimulus and the focus provided by the program.
It is most important to note that this displtty of new technology represents,
in addition to specific research results, the acquisition of
new manned aerospace flight "know how" by many teams in government and industry.
They had to learn to work together, face up to unprecedented problems,
develop solutions, and make this first manned aerospace project work.
These team were an important national asset in the ensuing space program.
At the start of the Mercury program there was, of course, a significant
foundation of missile technology that was heavily utilized for
launch propulsion, blunt-body aerodynamics, and heat protection. However,
the innumerable added constraints and requirements of a manned aerospace
system were present and in this area the X-15 team and the X-15 developments
were the principal technology sources. The later developments of the
USAF X-20 Dyna-Soar Program, particularly the large advances it provided
in radiation-cooled structures and materials, also became available for
If one takes a broad look at all of the contributions of the program
and considers relative values based on the actual applications that have
been made of the results, it is quite clear that the space-oriented results
have been of greater value than the hypersonic aeronautics contributions.
This is the reverse of what was expected in the beginning and is primarily
a consequence of the unanticipated early arrival of the space age. It is
interesting and important to note that any attempt at a cost-effectiveness
evaluation of research aircraft in 1954 would almost certainly have either
ignored or grossly undervalued the space flight aspects. At the same time,
the boost-glide missions which have since been displaced by unmanned space
systems, would have been exaggerated in value in any 1954 assessment. Who
could have foreseen in 1954 that within 5 years the top priority goal of
Western technology would be to put a man in orbit in space without delay?
Without the advantage of X-15 technology lead time, would Project Mercury
and the subsequent manned space projects have been delayed? What mis
fortunes might have occurred? What losses in national prestige might have
resulted? Haw much was it worth to have X-15 technology in these critical
times? No specific answers are possible, of course. But the existence of
intangible and initially unforeseeable values is undeniable.