NASA FRC

June 26, 1968

MEMORANDUM for Assistant Chief, Research Projects

Subject: Preliminary report on X-15 flight 1-77-136 Summary

Flight 1-77-136 was flown on June 12, 1968, by William H. Dana for the purpose of:

1. WTR launch monitor experiment checkout and coordination.

2. MIT/Apollo Simultaneous Photographic Horizon Scanner.

3. Fixed Sphere Flow Direction Sensor.

 The maximum velocity attained was 5200 feet per second (a Mach number of 4.96) at 134,000 feet. A maximum altitude of 214,000 feet was attained.

Satisfactory data were obtained from the fixed-sphere flow direction sensor. Because of malfunctions within the experiments, data were not obtained from the WTR launch monitor and MIT horizon scanner experiments.

Flight Track and Profile

The radar track and profile for this flight are shown in figure 1.

The launch was at Smith Ranch #1 on a magnetic heading of 170° from 45,050 feet at a Mach number of 0.8. The launch transients were normal. Engine light occurred 1.0 second after launch and 100 percent thrust occurred 1.5 seconds later. The launch was coordinated with a target launch for the WTR experiment. The coordination of the simultaneous launches was well within time requirements for a successful operation; however, the target launch was aborted for technical reasons.

The average angle of attack during rotation was 10.5° compared to the planned 11°. The normal acceleration during rotation was 2.25 "g's." The planned pitch angle of 33° was attained at 27.5 seconds and maintained until burnout at 85.7 seconds. Burnout occurred approximately one second earlier than planned. The shorter burn time resulted in a peak altitude of 214,000 feet compared to the planned altitude of 222,000 feet and a maximum velocity of 5,200 feet per second compared to the planned 5,400 feet per second. To off set the altitude lost from the shorter burn time, an angle of attack of 5° was held to peak altitude.

The planned 20° of angle of attack was reached during reentry at 170,000 feet. Pitch RAS was disengaged at approximately 1 "g" and 130,000 feet as planned and the pilot pushed over to 16° angle of attack and held the normal acceleration to 4 "g's" during "g" buildup. The pilot held 1.6 "g's" in the pattern with no noticeable buffet.

Stability and Control

The time history of the significant stability and control parameters telemetered during the flight is shown in figure 2.

There was a slight thrust misalignment and a maximum sideslip of 1.5° during boost. The pilot corrected for the misalignment. Over the top the pilot began a "head up" tracking task and reported he could keep the aircraft on track by reference to visible landmarks.

Air Force Western Test Range Launch Monitoring

The target launch for this experiment was aborted due to technical difficulties. At 200,000 feet, the experiment was extended for a functional check. Data indicated that the pressure measured on top of the experiment reached 13 pounds per square foot as compared to a calculated value of 7 pounds per square foot. This pressure is well within the experimenter's suggested maximum pressure of 30 pounds per square foot. After peak altitude the pilot switched the normal retract switch to "down". Analysis of the data indicates a time delay of 7 to 9 seconds before the normal retract sequence began. The sequence was not completed in the allowed 20 seconds before returning to 200,000 feet so the pilot activated the emergency retract sequence. Within 1 second the pilot reported lights out and heard the doors close. Postflight investigations failed to explain the delay in the retract sequence. Investigation is still proceeding and an extension of the time pad is planned for the next flight.

Satisfactory data were not obtained. Postflight inspection revealed a transistor blown in the horizontal drive of the TV system and a shear pin failure in the mechanical filter wheel in the Radiometer. The experiment has been returned to the contractor for updating, repair, and calibration. The experiment will be returned for the next flight.

MIT/Apollo Simultaneous Photographic Horizon Scanner

No data were obtained from this experiment. Postflight inspection revealed a loose screw in the experiment tail box which could have prevented the experiment from opening and starting a search and track sequence. The experiment has been returned to MIT for investigation. It will be returned for the next flight.

Fixed-Sphere Flow Direction Sensor

Acceptable data were obtained. The experiment has been removed from the left wing tip nose cone for modifications to permit the Sky Brightness experiment to be flown on the next flight.

Operational Discrepancies

At burnout the engine timer failed to stop. The engine shutdown occurred earlier than planned due to fuel depletion. Postflight investigation revealed a leak in the main ammonia valve prime seal. This engine has been replaced by engine 104 for the next flight.

Data System Discrepancies

Discrepancies noted on the flight were:

a. The picture from the cockpit Millikan camera is fuzzy and out of focus. A new Fiber Optics bundle is required to correct this discrepancy. No action will be taken for the next flight. Data are usable.

b. The right-hand wing pod camera jammed approximately half-way through the film roll. Data are partially usable. Camera will not be flown on the next flight.

c. On oscillograph 0-42-36C the roll and pitch AV/AAT's malfunctioned and angular rates and accelerations were not obtained.

d. The WTR elevation and azimuth signals were larger than expected and were off-scale. These channels will be rescaled.

e. The timing lines on the acceleration recorder A-8-3M were indistinct. Data are usable. The transistor switch will be replaced by a Reed relay switch on the next flight to remove this discrepancy.

f. The time code generator reset at APU reset due to a low battery voltage. The data time on all recorders require correction.
 
 

 James R. Welsh, Head

X-15 Research Project Office