Pilot: Joseph A. Walker
Chase: Major White
B-52: Pilot, Major Fulton
Co-Pilot, Capt. Kuyk
Launch Panel Operator, J. Russel
The flight was undertaken for the primary objective of attaining an altitude of 150,000 ft. This altitude would enable us to obtain data and qualitative information at Zero G for a longer period of time than has been possible before. Also the initial use of the attitude control rockets could be made before committing the aircraft to an altitude where their use was essential for control. Further, a check of the programming and presentation intended to enable the pilot to accomplish the mission could be made at less than maximum performance. Several maneuvers were scheduled during the flight for purposes of stability and control.
As a whole the flight was a rousing success. There were, of course, problems along the way. There was a malfunction of the liquid nitrogen pressurization and vent supply. After launch the engine shut down after a partial start. During reentry and pullout there was a continuous high frequency, strong amplitude vibration (later ascertained to be caused by a limit cycle oscillation of the roll stability augmentation).
In order to achieve 150,000 ft. the flight was programmed for 79 seconds of burning at 3/4 throttle or nominal 45,000 lbs. thrust. In order to attain the proper trajectory, a pullup to 35° q was accomplished and then q was maintained at 35° until engine shutdown. Parameter variations and their effect upon the peak altitude are as follows:
q ± 1° Altitude ± 3500'
Burning time ± 1 sec Altitude ± 3500'
Thrust ± 1000# Altitude ± 3500'
The pitch attitude parameter q was held 35° +1°/-0°. Burning time correlation was established with ground timing and the engine was shut down at exactly 79 seconds. The chamber pressure (475 psi) designated for 75 percent thrust was set within +5 psi. However, an apparent excess of 3000# thrust occurred which inspection of the above will show is the equivalent of 15,000 ft. altitude. This plus the full allowance for 1° extra pitch angle accounts for an altitude of 168,500'. Actual radar altitude was fixed at 169,600 ft. So I feel confident that we have a good presentation, one that is adequate for the task. There are, however, some minor improvements which would reduce the overall workload somewhat. We should add azimuth graduations between the main meridian lines at ±30° pitch angle on the three axis ball. We should replace the backup attitude indicator with the C-6 heading and homing indicator. Also, since it has such large errors, the high range Mach meter should be removed and the inertial vertical velocity installed. Nevertheless, if the indicators upon which we depend read correctly, we can do a good job of establishing the desired performance.
There was no difficulty whatsoever in maintaining the desired control of the aircraft during the coast over the top and initial portions of reentry. Also, in spite of the severe vibration during reentry and pullout, control was precise enough that attempts at finding the cause and eliminating the trouble were accomplished. The portion of flight from engine shutdown until entering the landing pattern were flown with the side console aerodynamic stick. Reaction controls were used at low q, particularly in correcting roll attitude. Some pitch rocket use was accomplished for damping pitch oscillations. No intentional use was made of yaw rockets. Minimum use of reaction controls had been requested prior to launch because of extra APU running time.
It seems to me that some means of restricting the side console aerodynamic stick control application rate (such as viscous damping) should be incorporated in order to reduce possibility of overcontrol at critical conditions.
There did appear to be some angle of attack effect on amplitude of the vibration which occurred during reentry. As a result 12° angle of attack was maintained during the pullout. Also 30° left bank was held in order to correct course back to base. The speed brakes were extended at the top of the trajectory. They were retracted after the vibration started but this had no effect. Reduction of pitch gain from a setting of 6 to 4 resulted in an immediate apparent decrease of about 20% amplitude. Then the yaw gain was increased from 6 to 8. About this time the vibration ceased. Inspection of the records indicated that total continuous duration was 56 seconds. My estimate of frequency was 10 cycles per second.
Setting up the landing pattern was no problem. Also, I was able to dissipate excess altitude before high key so that no use of speed brakes was required in the pattern. Touchdown was at 190 knots, less than 1 ft/sec vertical velocity, and 1000 ft. past the marked touchdown point. The pattern was flown with the center stick with stability augmentation gains 4-6-8. Left rudder input was used prior to touchdown to keep aligned with the runway. After touchdown left rudder was used up to full deflection to maintain straight track.
I found no difficulty in controlling the aircraft. The only effect of the long period between flights (seven months) I noticed was that I appeared to have less time left for performing requested maneuvers because of more concentration on the flying .
I experienced no abnormal or unexpected physiological phenomena on this flight. During the powered portion of flight the longitudinal acceleration reached a peak of 2.66 g. For about the last 30 seconds it was found beneficial to rest the head against the seat headrest. I had checked this position prior to flight for ability to see the instrument panel and knew with the A/P 22S-2 suit helmet it could be seen. Visual coverage proved even better under acceleration. The familiar sensations experienced on the centrifuge began to make themselves felt on this flight during power on operation, such as heaviness in chest, pressure of "Adams Apple", and mild watering at the outside corners of the eyes. I found myself waiting for thrust cutoff. After that there was a very mild sensation similar to falling. This was recognized and forgotten in a very short period of time. I transferred from center to side aerodynamic stick, changed the trim selector switch, and turned on the reaction controls immediately after engine cutoff. Angle of attack was reduced to 4° and then to about 0°. Aerodynamic controls were the main control utilized with reaction controls used for some roll control and for damping pitch motions. After the attitude was stabilized there was plenty of time to look outside and view the sky, the wide sweeping horizon, and look down at the ground. No stars were visible, even away from the sun, in the deep, dark blue sky. The curvature of the earth was very pronounced. The depression of the horizon was very noticeable. Around the curved horizon there was a band of thinly diffused brightness, I think the result of looking through the atmosphere. The ground itself had receded to shades of gray and brown with a bright appearance. Geographical features were easily distinguishable. In fact, the ability to appreciate relative elevation was striking. One could see for hundreds of miles, although of course, clarity was reduced with distance. All the foregoing was accomplished at zero g and serves, I think, as a fit commentary as to whether the human can function under these conditions. In fact I was mildly disappointed that my stay wasn't longer.
The reentry configuration was set-up with no trouble. The vibration set in but I hung on and attempted to cure it as mentioned before. The buildup of acceleration was without any physiological problem.
I believe that this flight was very valuable in that it uncovered a poor stability augmentation functional characteristic in time to be corrected prior to more stringent flight conditions. Also that two minutes of weightlessness are no more of a problem than lesser periods. In fact one consciously appreciates the sensation of resting after the greater physical effort while power is on.
Joseph A. Walker
Aeronautical Research Pilot