To: Chief, Research Division

From: Aerospace Engineer, Vehicle and Systems Dynamics Branch
Subject: Preliminary Report of X-15 Flight 3-21-32

1. Flight 3-21-32 was flown by Joseph A. Walker on July 19, 1963 for the purposes of:

2. Smith's Ranch, Nevada was used for the first time as the launch site. The launch was made with roll attitude and heading hold modes "on" with a heading of 173°. With the exception of the launch transient, heading was held within 2° of the system's reference for the entire period in which the hold mode was operating. The hold mode was turned off at about 200,000 ft. on the entry.

This was the first flight using an engine with the LOX purge system. The engine was allowed to run until fuel exhaustion, and functioned satisfactorily; however, engine thrust was about 700 to 800 pounds higher than expected (based on test stand data) and ran about 0.8 sec. longer than anticipated. Both of these factors contributed in part, to the altitude overshoot. The average pitch attitude of 45.5° during the climbout was 1.5° higher than planned, and contributed to the altitude overshoot also. The pitch attitude was high because the pilot heeded ground control calls, indicating that the flight profile and pitch attitude were low.

The flight data also indicates that the engine was slightly misaligned so that the thrust vector would pass to the left of the airplane center of gravity. The misalignment was about 1/8 of an inch and resulted in a burnout transient of 0.1 "g" lateral acceleration.

3. Both manual and automatic reaction controls were used during the ballistic part of this flight. Manual reaction controls were used to trim the airplane as a pilot's preference to trimming the adaptive control pitch rate. This resulted in a very large peroxide usage by the reaction controls. The automatic system used approximately 38 pounds and the manual system used approximately 34 pounds. The peroxide low light came on late in the entry and peroxide transfer was used until after touchdown.

The automatic reaction controls began operating at about 75,000 feet on the exit and ceased to operate at 110,000 ft. on the entry when the dynamic pressure reached about 240 psf.

4. The entry was initiated by the pilot at about 240,000 ft. The 25° angle of attack was established at about 180,000 ft., when the entry acceleration began to build up. The angle of attack was maintained between 24° and 26° until normal acceleration reached 3 "g". The angle of attack was about 22° when the peak normal acceleration of about 5 "g" was reached. An average of 4.7 "g" was then maintained until the maximum dynamic pressure of about 1350 psf occurred. A pitch oscillation was induced by the pilot at about 145,000 feet and caused the horizontal stabilizer to bottom out momentarily. Aside from this oscillation, the stabilizer did not exceed about 26° during the entry. Lateral-directional stability and control during the entry was excellent. There were no oscillatory motions, only small random excursions in roll attitude and sideslip. The maximum excursion in sideslip was about -2° and was the result of a steady right rudder input by the pilot during the 5"g" pullout. The maximum lateral acceleration was about .46 "g". Roll attitude did not exceed +6° of bank angle.

The pilot reported that the airplane handled far better than the simulator during the entry and rated the entry: q 1 , f 1 , y 1 .The pilot felt hr could accomplish a satisfactory entry from 350,000 feet if all other limitations could be maintained.
 
 

Elmor J. Adkins

Aerospace Engineer