June 4, 1963

To: Chief, Research Division

From: Aerospace Engineer, Vehicle and Systems Dynamics Branch
Subject: Preliminary Report of X-15 Flight 3-18-29

Flight 3-18-29 was flown on May 29, 1963, by Joseph Walker for the purposes of:

Aerodynamic heating investigation at high Mach number and low angle of attack

Ventral off stability investigation

Infrared and ultraviolet experiment

A cursory review of the flight records indicates that the above objectives were accomplished as planned. All systems functioned normally and there were no failures or malfunctions that affected the flight. High heating rates and high temperatures at approximately burnout caused a fracture of the left inside windscreen and a crack in the forward left side fairing, approximately 14 inches long. Both failures will require repair and replacement prior to the next flight. The maximum altitude for this flight was approximately 91,000 feet; maximum velocity was approximately 5600 fps; maximum dynamic pressure was approximately 1350 psf. The maximum expected temperature of 1100°F was probably exceeded slightly.

Heat transfer data was obtained just prior to engine burnout at velocities between 5400 and 5600 fps. For this data, the angle of attack was less than 1° for approximately 9 seconds and the speed brakes were open. Right rudder was held in during the latter part of the boost phase and resulted in a steady left sideslip of 2.5° to 3° just prior to burnout. The maximum lateral acceleration was approximately 0.6 ~g~ and the bq may have reached 4OOO. (Limit bq » 6500).

Shortly after burnout, with the speed brakes open, the pilot performed a rudder pulse and a turn with the yaw damper disengaged. The pilot reported no problem in controlling the airplane and gave ratings of: q 1 , f 1 , y 3 .

The angle of attack for these maneuvers varied between 0° and 8°; velocity decreased from about 5000 fps to about 4300 fps. A slight directional oscillation (±0.5°b) at 0.38 cps was noted in the data following a rudder input. When the speed brakes were closed the period of the oscillation increased. While decelerating, from 4300 fps to 3700 fps, the pilot disengaged the roll damper also and after disturbing the aircraft he controlled the airplane using aileron proportional to both bank angle and rolling rate. Angle of attack varied between 4° and 12°. He reported little difference between the two but expressed a preference for controlling to bank angle. His ratings were:

q 1 , f 2.5-3 , y 2.5 .

During periods of high heating (and cooling) rates, the pilot reported many instances of bangs and jars in the airplane and control system. These phenomena were also reflected in the internal data traces as abrupt shifts followed by a short period of oscillation at 12 to 13 cps as the structural thermal deformation was relieved.

The internal recorders ran out of film approximately 75 seconds before landing. This was the longest flight in the X-15-3 since flight 3-4-8 and lasted almost 12 minutes.
 
 

Elmor J. Adkins

Aerospace Engineer