Summary

Flight 2-47-84 was flown on August 3, 1966, by Major William J. Knight for the purpose of pilot familiarization and to obtain data for a) ultraviolet Stellar photography (#1), b) stability and control, c) alternate pitot-static systems, d) base drag, e) ball nose lip temperature, f) thermal protection systems development, g) RAS operation.

The maximum velocity attained was 5050 fps (3443 mph and a Mach number of 4.68) at an altitude of 140,000 feet. The maximum altitude reached during the flight was 248,000 feet.

This altitude build-up flight was Major Knight's fifth flight in the X-15 and was accomplished essentially as planned with no significant malfunctions occurring. Acceptable data were obtained on all experiments.

The attention required of the pilot to compensate for a misaligned engine, with the associated lateral-directional control problem, resulted in his acceptance of a slightly higher than planned pitch attitude. The 18,000 foot overshoot in maximum altitude is attributed primarily to this excessive pitch attitude. The engine will be realigned prior to the next flight.

Flight Track and Profile

The radar ground track and altitude profile for this flight are shown in figure 1. The X-15 was launched at Delamar #1 (East) within 34 seconds of the planned launch time. This precise timing was dictated by the ultraviolet Stellar photography experiment. The ground track very closely paralleled the planned track even though the airplane was launched about 5° off heading. The pilot was able to correct the heading immediately after launch.

A maximum altitude of 248,000 feet was reached during this flight. The planned maximum altitude was 230,000 feet (fig. 1). The overshoot of 18,000 feet is attributed primarily to a high average pitch attitude during climbout. Also, there is a suspected discrepancy in the performance of X-15-2 between the simulation and flight data. Additional flight data are needed to resolve this discrepancy. The excessive pitch attitude maintained during the climbout is the result of the pilot having to divert his attention to compensate for a misaligned engine.

Stability and Control

A time history of the flight is shown in figure 2. The altitude and velocity shown in figure 2 are adjusted radar data, while the other parameters are uncorrected telemetered data.

After a normal launch, an average angle of attack of 10 degrees was maintained during the rotation. During the rotation the pilot reported that he ran out of trim. Internal data show the horizontal stabilizer was deflected 20 degrees at this time. This is somewhat less than what is expected for the maximum trim setting. Similar trim discrepancies have been noted on earlier flights of X-15-2 and the cause is still unknown.

During the early phase of the climbout, the planned pitch attitude of 37 degrees was exceeded by an average of 2 degrees. The pilot stated that the increased attention and effort required to compensate for the engine misalignment caused him to neglect pitch attitude. An altitude overshoot resulted. Throughout the boost, the pilot was attempting to null the sideslip which resulted from an engine thrust misalignment. This condition was known to exist from the previous flight and was accounted for during simulator practice. The pilot reported the thrust misalignment was more severe than anticipated and required almost "full rudder" near shutdown. Flight data show the rudder was deflected about 4.5 degrees and that the angle of sideslip remained at 2 degrees.

The reaction augmentation system was engaged during the ballistic region and functioned satisfactorily. Attitude control at high altitude was very precise, well within the desired limits.

During the entry an average angle of attack of 15 degrees was maintained with a maximum of 18 degrees at one point. The aircraft experienced the pitch down transient at the beginning of the entry when the pilot relaxed stick force. The amplitude of the change and the subsequent pitch oscillation was less than on flight 2-46. The stabilizer moved from -22 degrees to -19 degrees as the stick force was relaxed with no change in the full aft trim position. The pilot rated the entry at q 2.5, f 2.5, and y 3. The maximum dynamic pressure was reported by the pilot to be 1400 psf.

Ultraviolet Stellar Photography (#1)

The X-15 launch time and high altitude flight attitudes were dictated by the position of the prime target star, Eta Aurigea, during the morning of August 3. The desired launch time was 08:46 PDT and the desired pitch and roll attitudes were +5 degrees and +2 degrees, respectively. Actual launch time was 08:45:26 PDT, 34 seconds early. At the time the experiment was activated the aircraft pitch attitude was +4 degrees. This value was maintained within 1 degree of null during the 42 seconds of data acquisition. The maximum deviation in pitch was 2 degrees from the null position. The roll attitude was +l degree at activation and was held within 2 degrees while data were being obtained. The maximum deviation was 3 degrees.

Analysis of data obtained in the visible light region was inconclusive. Star data were not visible to the naked eye. These data will require analysis under microscope before the quality of data can be stated. The visible film appeared to be fogged and the cause is being investigated. Light scattering was again observed in one of the cameras using the Tri-X film. Analysis of the film in the ultraviolet region has not been completed.

Considering the accuracy to which the required attitudes were maintained (+5 degrees allowable), it is believed that the star Eta Aurigea should appear on the photographic film. The experimenter indicated the flight had been flown satisfactorily and data could be expected. The next flight for this experiment will be 2-48. An attempt to measure the day airglow will be conducted in conjunction with the star photographic task.

Alternate Pitot-Static System

The pilot indicated the pitot-static system was activated at a Mach number of 2.0. Data were obtained, and are being processed for analysis.

Base Drag Study

Data were obtained for the base drag study. These data are being processed for a continued analysis.

Ball Nose Lip Temperature

Temperature of the ball nose retainer ring lip are being monitored, however, only data from flights exceeding M = 6 are of interest.

Thermal Protection System Development

This was the third flight for the ablatives material and test window on the ventral stub. This flight, like the preceding flights, did not produce heating conditions that would affect the material, however, there was some light charring of the leading edge, but not sufficient to produce fogging of the test window. The condition of the material is still suitable for flight and this material will be retained for the next flight.

RAS Operation

The reaction augmentation system was used during this flight and operated satisfactorily. Attitude control precision at high altitude was excellent.

Instrumentation Discrepancies

The T/C traces on 0-9-36C sequences 181-240, 241-300, and 301-360 were fuzzy.

The T/C identifiers on 0-9-36C for channels 2 and 6 and channels 8 and 12 were also blurred.

The film drum for 0-18-36C was dirty following the launch. Emulsion was found in the drum slot.

The calibrates on 0-18-36C for strain gage 410, strain gage 611, and strain gage 201 were off scale.

The roll BCS channel on 0-19-36C for the #2 rocket did not function properly. Data were not obtained on this parameter.

The calibrate deflection on 0-26-36C for the Startracker free air temperature did not deflect properly.

The traces on P-1-4E became very light during the latter portion of the flight.

Dirt was reported in the drum of A-9-3M. The film also indicates scratching.

Operational Discrepancies

During the prelaunch operation, the pilot reported the rate of climb was varying ±100 fps. The inertial platform appeared to be working properly at launch, and it appears to have functioned normally during the flight.

An engine thrust misalignment was evidenced during the flight. The engine has been realigned.

Full nose-up trim setting continues to produce less than the specified horizontal stabilizer deflection during rotation and entry. Investigation of the condition is continuing.
 
 
 
 

Elmor J. Adkins, Head

X-15 Research Project Office