Summary

Flight 2-46-83 was flown on July 21, 1966, by Major W. J. Knight for the purpose of: a) pilot familiarization, b) Star Tracker checkout, c) alternate pitot-static system evaluation, d) Martin ablative test, e) base drag studies, f) window fog test, and g) ball nose lip temperature measurement.

The mission was flown essentially as planned and all objectives were accomplished to the extent anticipated.

Profile

The aircraft launch was normal. The angle of attack was 11 degrees during rotation except for an initial period during which angle of attack was approximately 8 degrees. The planned pitch attitude was achieved about 3 seconds early. The pilot indicated engine shutdown at a velocity of 5,100 feet per second. The initial radar data indicated a maximum velocity of 5,300 feet per second. The cockpit film displayed a possible maximum of 5150 feet per second. At engine shutdown an angle of sideslip of about 3 degrees resulted from thrust misalignment.

After engine shutdown, a pronounced right roll occurred, during which the aircraft rolled to 27 degrees. The pilot reacted with almost full left aerodynamic control. When this did not correct the roll he corrected with the ballistic control system. This was reported to be different from the simulator, from which the pilot had expected enough aerodynamic control to correct for this type of deviation.

At about 170,000 feet, ascending, the pilot actuated the Star Tracker experiment. For this flight the Star Tracker coordinates were set for zero degrees in pitch and roll attitudes. It has been planned that the pilot would fly zero degrees angle of attack to peak altitude and the pitch attitude would be zero degrees at apogee. Activation of the Star Tracker system prior to attaining the preset coordinates results in a realigning of the Star Tracker coordinates. The Star Tracker attitude thus displayed was the angular displacement between the aircraft axis and the Star Tracker platform.

At peak altitude of 192,000 feet (180,000 feet was the planned peak altitude as shown on figure 1) the pilot attempted to fly the Star Tracker task. During this time the pitch attitude varied between -2 degrees and +7 degrees, while the roll attitude was varying between +5 degrees to +10 degrees. Airplane attitude angles must be within 8 degrees of the preset value in order to obtain data. Using manual BCS, the pilot rated the task as 3.5 in pitch and 3.5 in roll, while no attempts were made to control yaw.

The entry was accomplished at the planned angle of attack of 16 degrees with the speed brakes open to 20 degrees. The angle of attack increased to 19 degrees as the maximum Mach number was reached. A pitching oscillation occurred at this point similar to those observed during the initial portion of other X-15 entries. The ballistic control system firing was in the roll and yaw axis. Internal recordings indicate the pilot was maintaining the observed -24 degrees pitch stabilizer with a slight back force on the aerodynamic controller. The initial pitch down of the oscillation resulted from the pilot relaxing the force, with the stabilizer moving to a -19 degrees. There were no trim changes during this interval and the pitch horizontal stabilizer would have been expected to remain at the -24 degree position. An analysis of this problem is being conducted. The entry was completed with a maximum dynamic pressure of 1000 PSF and a maximum normal acceleration of about 3.6 "g." The remainder of the flight was normal.

Star Tracker

The Star Tracker experiments functioned satisfactorily during the flight. The experiment was flown to perform a functional checkout of the electrical system, platform, clam shell door operation, and provide pilot familiarization of Star Tracker task. There were no stars in the region being photographed during this flight. The flight provided a checkout of Star Tracker operation following modification of the camera shrouds. The data obtained from flight 2-42-74 had indicated light scattering resulting from light reflecting on the camera lens would be a problem. The light scattering resulted in intermittent diamond patterns on the developed film. Analysis of the film following flight 2-46-83 indicated the light scattering problem had been eliminated, however, the shroud itself was evident on the film. The film recording of ultraviolet radiation has not been analyzed, however, it has been forwarded to the experimenter.

Alternate Pitot-Static System

The alternate pitot-static system was actuated during the pattern. Data were obtained and are being analyzed. Good correlation between the "dog leg" system and the alternate pitot-static system has been reported. A comparison between data obtained from the ball nose and the alternate system on previous flights indicated identical values between M » 0.3 and M » 0.6. Between M » 0.6 and M » 0.9, the angle of attack appears to effect the data and further flights have been requested to obtain analytical data in the region. The alternate pitot-static system would be required in the region below M » 0.6 and will be satisfactory for use on the M » 8 flights.

Martin Ablative Test

Martin ablatives were applied to the fixed portion of the lower vertical stabilizer, nose panels, nose gear door, fixed points, and patches located on the side fairings. Inspections of these areas following flight showed no charring or ablation. This was the second flight with the same material application. Spray layer delamination had been experienced on earlier flights, but has not detected in ablatives applied for this and the previous flight.

Window Fog Test

The results of the window fog test were inconclusive. No window fog was detected. The flight was not sufficient to result in sufficient charring to produce the expected glaze over the windows. The window will remain installed in the fixed portion of the lower vertical stabilizer for the next flight.
 
 

Base Drag Study

Data obtained on the flight are being analyzed. Data obtained on previous flights have been satisfactory.

Instrumentation Discrepancies

0-18-36C

The horizontal stabilizer strain gage #610 was intermittently hashy.

The #201 strain gage trace shifts position during the flight. Calibrate malfunctions occurred on strain gage #410 and horizontal strain gage #611.

The film drum changes speed at 0.05 seconds after launch

0-9-36C

Identifiers traces below zero are light.

Only two pulses were recorded on T/C sequences 421-480 during the flight.

0-26-36C

An improper calibration deflection occurred on the Star Tracker free air temperature.

The 0-26-36C film drum stalled about each 3.5 seconds.

Operation Discrepancies

A slight roll to the right seemed to persist throughout much of the flight. The cable tension regulator of the rudder control system will be replaced prior to flight 2-47. The rudder system maintains zero trim under ambient temperature, however, a rudder offset was noted during the flight. A change in the "zero force" trim position without trim actuation occurred during the initial entry and is being investigated.
 
 
 
 
 
 

Elmor J. Adkins, Head

X-15 Research Project Office