ADVANCED RESEARCH AND TECHNOLOGY

TABLE 4-1-X-15 Flight Program Highlights

Piloting.-A major goal of the program, and one which has been most successfully achieved, was to explore the capabilities and limitations of the human pilot in an aerospace vehicle. The space trajectory and reentry maneuvers to be performed by the X-15 pilot were guaranteed to provide a convincing test of the role of the pilot, a serious question in the early 1950's.

Because there were no two-seated versions of the X-15 in which pilots could be taught to fly, the pilots were required to learn on ground-based simulators. The 12 pilots were trained this way with outstanding success, and this experience paved the way for similar all-out use of simulators in the space program.

The X-15 program shows clearly that, given precise displays, the pilot can fly rocket-powered vehicles into space with great accuracy. Attitude control in space, a serious unknown in 1954, was shown to be a skill readily acquired by pilots.

The steep reentries of the X-15 with flight path angles up to minus 38 degrees, speeds approaching Mach 6, and steep angles of attack presented a more difficult piloting problem than the shallow entries characteristic of manned orbital flight. With the X-15's systems operative, the pilots could perform the reentry maneuver readily.

With a few exceptions, weightlessness and the high heart rates associated with this type of flying produced no difficulties. Both of these factors were large unknowns before the X-15 program.

An analysis of the first 44 flights showed that 13 of them would have failed in the absence of a human pilot together with the various redundant systems in the airplane. Against these figures in favor of the pilot, there were only a few examples where the pilot's error degraded the mission performance, and only one catastrophic accident out of the 199 flights.

A broad positive finding of the program is clear: the capability of the human pilot for sensing, judging, coping with the unexpected, and employing a fantastic variety of acquired skills remains essentially undiminished in all of the key problem areas of aerospace flight.

Hypersonic Aerodynamics.-Virtually all of the pressures and forces measured in flight were found to be in excellent agreement with the low-temperature wind-tunnel predictions. With this broad validation from the flight tests, the conventional low-temperature hypersonic wind tunnel has become the accepted tool for future configuration development.

Turbulent Heat Transfer.-Because of major limitations of theory and an almost complete lack of reliable hypersonic windtunnel data, there was initially great doubt about the predicted turbulent heating rates for vehicles of this speed range. The measured flight data showed a marked departure from the available predictions, averaging about 35 percent lower, and this significant difference stimulated the development of new prediction methods and new ground-based investigations. The high-lighting of important problem areas and the stimulating of new research exemplifies one of the greatest values of an exploratory research airplane.

Structures.-The thick-skin heat-sink type of metal structure adopted in the design of the X-15 made possible a wide range of flight missions, including steep reentry. No unexpected incidents occurred in flight for the primary structure. However, many unanticipated local heating problems were found in the secondary structures, and they were solved. These failures point out the fact that what are considered minor design details of a slower craft must be dealt with as prime design problems in hypersonic vehicles. This knowledge was put to use in the precise design of a host of important details on the manned space vehicles.

Operational Subsystems.-It was necessary to use many newly conceived, partially developed subsystems on the X-15. In spite of extensive environmental testing, new problems were encountered after the start of flight operations. In this area, the X-15 brought to light many "real" problems that could not have been foreseen by any other means than involvement with an actual flight vehicle.

ADVANCED RESEARCH AND TECHNOLOGY

Many specific new requirements for aerospace developmental testing were identified and were of great value in subsystems development for the space program.

Follow-On Experiments.-Early in the program, it became apparent that the X-15 could perform a valuable function, not foreseen in the original planning, as a reusable carrier for a wide variety of scientific experiments, most of them dealing with space programs. More than one experiment was carried on many flights, and the X-15 system, unlike space rocket testing, permitted full recovery of the equipment, recalibration, and repeated runs where needed. In nearly all cases, use of the X-15 was the least costly and quickest means of achieving the desired results.

Other Contributions.-Over 700 different technical documents were produced; 200 of the documents reported general research that would have not been undertaken had it not been for the stimulus of the X-15.

Probably one of the most important contributions, and an intangible one, is the acquisition of new "know how" by many teams in government and industry. Working together, they had to face up to unprecedented problems, develop solutions, and make this first manned aerospace project work. They remain an important national asset in the space program.

The result of the focusing and stimulating effects of the X-15 program was to generate aerospace vehicle technology at a highly accelerated rate and to provide a massive backlog of aerospace technology for the space program.

BIOTECHNOLOGY AND HUMAN RESEARCH

Human Research

Community Reactions to Airport Noise.-As part of a program recommended by the Office of Science and Technology, Executive Office of the President, an extensive acoustical and sociometric survey was being made around major airports to determine the various psychoacoustic responses to noise. On the basis of this research, quantitative noise evaluation techniques and standards can be developed for use by the FAA, airport operators, and aircraft/engine manufacturers. In Phase I of the study, 5400 interviews were conducted in three regions around the airports (0-3 miles, 3-6 miles, and 6-12 miles) in Chicago, Dallas, Denver, and Los Angeles. The data are being analyzed and will be used by the FAA in aircraft certification. Phase II includes 4000 interviews

around the jet airports of Miami, New York, and Boston. Miami was completed and New York is underway. The study has shown that many factors other than level of noise exposure are important in explaining the reactions of people to aircraft noise. Two such factors are day and night values of PNdB (perceived noise in decibels) and the number of flights. The scientific data now becoming available will be useful in assaying the contribution of social factors in predicting the effects of noise disturbance and will also be useful in noise abatement programs.

Sonic Boom: Public Reaction Studies

This study, which is part of the effort to assess noise pollution scientifically in order to provide a basis for rational public policy decisions, deals primarily with public reactions to modest sonic boom over-pressure levels generated by supersonic flights over Dallas/Fort Worth, Denver, Atlanta, and Chicago in late 1967. The study identified major social, economic, and psychological factors found to be associated with one or another type of public reaction in these metropolitan areas. About 2,670 pre-test interviews were obtained before the first overflights, and a post-test sample of about 1,000 interviews was obtained. The final report was in the review stage.

Bone Mineral Loss

The demineralization of bone, such as that discovered on the Gemini and Apollo flights, was studied to determine whether the loss of calcium is inexorable or can be prevented or reversed by exercise. Volunteers at the U.S. Public Health Service Hospital in San Francisco have spent over 5 months in bed simulating the weightlessness of space flight. (Fig. 4-21) During the first three months they engaged in 80 minutes of moderately vigorous physical exercise each day. The hope was that the loading of bones during exercise would substitute for the postural loading normally found in the 1 G environment of the earth's surface. Assessment of their calcium balance after the three months revealed a disappointingly slight beneficial effect and indicated that a prohibitively high exercise load would be necessary to approach complete reversal of loss. Although the result was discouraging, it did direct attention to dietary measures as a means of controlling calcium loss. Dietary supplements, such as phosphorus, may be beneficial; they may also eliminate the inordinate amount of crew time needed for the exercise program.

ADVANCED RESEARCH AND TECHNOLOGY

On two of the first three Apollo flights, the astronauts for the first time developed "queasiness" if not outright nausea and vomiting. The feeling was associated with movement around the cabin during the early phases of the flights.

Earlier, NASA's Human Research Program, recognizing the possibility of such a reaction, supported an exhaustive investigation at the Naval Aerospace Medical Institute of the efficacy of various combinations of antimotion sickness drugs. The study revealed that the combination of two widely used remedies, scopolamine and dexadrine, was significantly superior to other more glamorous and popular combinations. The tests for motion or Coriolis sickness were conducted in a Slow Rotating Room, a room which could rotate smoothly at up to 10 rpm, and furnished and stocked to permit subjects to live in it for over a month at a time. Another application of the Slow Rotating Room was the development of a controlled series of head movements, so graduated that frank Coriolis sickness would not occur, but which stimulated the vestibular apparatus of the subjects to a degree which effected adaptation to the rotating environment much sooner than would