Prior to initiation of the flight program, a simulation was conducted on the human centrifuge at Johnsville to assess the pilot’s ability to control the X-15 while being subjected to the large acceleration forces involved in a typical flight. This was the first use of the human centrifuge in a closed loop simulation. After many simulated flights, and occasional wild rides due to electrical glitches, it was determined that the pilots could cope with the highly unusual acceleration environment.
One other unique simulator was used to evaluate a particularly vexing control problem, an in-flight simulator. The Cornell Aeronautical Laboratory had recently developed a variable stability aircraft which could be programmed to simulate the flight characteristics of almost any other aircraft. This in-flight simulator was used to simulate a marginally controllable atmospheric entry maneuver to determine whether the pilots could successfully complete a reentry. The results of this simulation indicated that it was unlikely that the pilot could make a successful reentry without stability augmentation. This in-flight simulator was considered to be a very good simulator since it provided much more realistic cues to the pilot. It was, in fact, so realistic that Neil got carried away in his struggle to salvage a deteriorating entry maneuver and broke the handle off the reaction controller.
The X-15 was the first research aircraft program to make extensive use of simulation for flight planning and pilot training. The simulation was particularly useful during envelope expansion. We were able to avoid many pitfalls because of the simulation. It really paid off. I personally do not believe we could have successfully flown the aircraft without a simulation, particularly in regard to managing energy. There was no way that a pilot could manage energy in the X-15 by simply looking out the window. For example, at speeds of Mach 5 and greater, there was no way that a pilot could land at a field or a lakebed that was directly under him. He had too much energy. He would continue along his flight path, regardless of how hard he was trying to turn. The landing site starting from Mach 5 or greater had to be at least 50 miles down range (preferably farther) to allow him to dissipate his speed in a reasonable manner. Simulation was essential for high-speed flight. The simulation was initially created using wind tunnel data, however the simulation was updated with flight data as the program progressed.
Regardless of how much practice we had on the simulator, we always seemed to be behind the airplane when flying the real flight. We could not easily keep up with the flight plan. One of our brighter flight planners, Jack Kolf, came up with the idea of a fast time simulation, wherein we compressed the time in the simulator to attempt to represent the actual flight. This technique seemed to make the simulation more realistic. Simulation is now used routinely and extensively in training for test flights for military missions, for airline operations, and for many other applications. Simulation technology was given a big boost by research and experimental aircraft test programs such as the X-15, for we had to develop good simulators to survive.
The team morale was excellent throughout the entire program. There was a lot of competition among the three aircraft crews to outdo the other crews in any endeavor imaginable. The crews competed in minimizing the time to turn the aircraft around after a flight and prepare it for the next flight. They competed in minimizing the time to mate the aircraft with the B-52. They compared actual flights versus attempted flights for the three aircraft. They competed for the next available B-52 launch opportunity. Many of the team members contributed numerous hours of unpaid overtime just to ensure that they were not responsible for a delayed or aborted flight.
Paul Bikle, the Dryden director, aided and abetted this competition by betting money against the various crews on any schedule, or other event that the crew was attempting to achieve. He stimulated competition among the different crews in numerous ways, in a continuous effort to maximize the morale and productivity of the project team. To keep morale high, he supported the postflight parties.
Parties were the final act of a flight operation. These parties were not organized or planned, but rather, were a spontaneous celebration following the massive team effort to accomplish a successful flight operation. Parties were an extremely successful mechanism for boosting team spirit. They characteristically began immediately after working hours at the biggest bar in Rosamond—Juanita’s. This was the favorite watering hole on the way home to Lancaster and Palmdale. The normal clientele at Juanita’s included local farmers, prospectors, gamblers, and house players for the neverending poker games. These people were engulfed by the X-15 team on the occasion of a flight party. What a strange mix of the past and the future among the patrons on those nights, prospectors looking for the end of the rainbow and rocket pilots looking for the top of the rainbow.
The parties were almost exclusively stag and free of any animosity. They would continue on for four or five hours at Juanita’s and then gradually transition to various bars in Lancaster. Quite often, the transition would include a race down Sierra Highway to Lancaster (15 miles away) with no holds barred.
One memorable race involved about twenty different high-performance vehicles with multiple occupants. I had started out in the race, but dropped out to assist Ralph Jackson, our public relations officer. He was limping along at 70 MPH in his old MG roadster with Jack McKay as a passenger. I decided to help him out. I was driving a ’57 Jaguar roadster. As I came up behind him, I downshifted to third gear and then pulled up to begin pushing him. I managed to push them up to 90 MPH before I finally backed off due to some frantic waving by Ralph and Jack. I later learned that the steering on Ralph’s MG locked up at speeds over 80 MPH. We had a ready excuse if the California Highway Patrol had observed this operation. We planned to tell them we were trying to get Ralph’s car started.
Otherwise, the race was proceeding in an orderly fashion until the participants overtook a large semi truck just outside of Lancaster. The racers chose to pass the truck at extreme speeds in a random fashion on the left or right as the oncoming traffic might allow, while creating tremendous confusion and huge clouds of dust. As this stream of speeding cars entered the outskirts of Lancaster, a deputy sheriff observed the race and immediately pursued and stopped the leaders and subsequently the entire line of drunken race car drivers. He proceeded to write tickets from the first to the last car, including one team member’s car who was not racing but just happened to be overtaken as the deputy sheriff apprehended the racers.
The truck driver, who had been terrorized by the racers, pulled up as the deputy sheriff wrote out the speeding tickets. He was almost incoherent as he explained to the deputy sheriff what had transpired. He insisted that the deputy arrest every one of the drivers and passengers and offered to transport them to jail in his semi truck trailer. The deputy would not buy any part of the proposition. He realized he was pushing his luck by simply passing out speeding tickets to that supercharged group of revelers.
No drunk-driving tickets were issued. The sheriffs in those days were very tolerant of drunk drivers, in many cases giving them a ride home rather than a ticket or a ride to the drunk tank. If today’s laws had been in effect, we would have had a lot of people in jail after each flight.
Throughout most of the flight program, the rocket engine was tested in the aircraft on the ground prior to each launch. The engine was sequenced through its normal starting cycle in a step-by-step fashion to allow various checks and inspections to be made during each phase of the starting cycle. When all this was accomplished, the main chamber was lit off and the engine was throttled from minimum thrust up to maximum for a few seconds and then back to minimum thrust before being shut down. We then went through a restart sequence and again ran up to full thrust and back to minimum thrust up to maximum and then shut it down for a post-engine-run inspection.
When an X-15 engine was being tested, it was obvious to everyone on the base. The engine could be heard very distinctly anywhere on the sprawling test center complex, regardless of how many other aircraft were flying or taxiing or runn
ing up their own engines. The X-15 engine had a very distinct banshee-type sound that was instantly recognizable. The X-15 made 199 flights, resulting in hundreds of post-engine-runs preparing for these flights.
I am not sure that anyone knows exactly how many total engine runs were made, because we made extra engine runs if there were any anomalies. We also made extra engine runs if there was an excessive delay in getting a flight off after an initial qualifying engine run. I remember making at least four engine runs in preparation for just one flight, due to a series of malfunctions during each of the first three runs. We also had a separate engine test stand to test engines after engine repairs or overhauls. A conservative guess of the total number of X-15 engine runs would be roughly 400.
The X-15 engine runs were conducted in the same sequence each time and for about the same duration. As a result, everyone at Edwards became familiar with the sequence of events and the sound pattern. They subconsciously realized that there was a problem if the sequence or the timing was interrupted. It seemed that regardless of what we happened to be doing when we heard an X-15 engine start, we subconsciously listened to the sequence and timing of the run to ascertain whether the run would be successful.
One of the X-15 operations engineers, Ron Waite, could imitate the sound of the entire sequence of the rocket engine run from the rumbling of the ignition sequence, through the main chamber light off to the peculiar hog calling like noise of the shutdown. It was a real joy to hear him go through the sequence. He can still go through the routine almost 20 years after the last X-15 flight.
I was always impressed by an X-15 engine run, whether I was in the cockpit making the run or just observing it. I loved to watch a run and see and hear the raw power of that engine. In those days, we could get as close to the aircraft during a run as we dared. No one really kept us away from the aircraft, however, everyone was aware of the potential danger. Most of the rational people took cover during the run in the blockhouse or in one of the pillboxes around the test stand or at least got behind something solid in case of an explosion. I was different than most. I was fascinated by the sound and fury of the engine. I would get as close as possible and watch the whole sequence. Kind of like intentionally standing out in the fury of a tremendous storm.
I have always loved to hear the sound of a powerful engine, whether it was a rocket, a jet, or an automobile engine. After the X-15 program ended, we acquired two YF-12 (SR-71 prototype) aircraft to do flight research. I thoroughly loved to listen to those aircraft starting up because there was a double treat. Those aircraft used Buick automobile engines as starter engines for the jet engines. So I was first treated to the sound of the powerful automobile engines revving up to 7,000 or 8,000 RPM and then the sound of the jet engines winding up and lighting off and creating their own overpowering symphony of sound. I really wish now that I had a recording of both the X-15 and the YF-12 engines runs so that I could play them when I needed a psychological boost. Maybe I will ask the X-15 operations engineer to make a recording of his imitation of the X-15 engine run. I wonder if he can do Buick engines?
This love of engine noise is undoubtedly a result of my engineering background. I believe engineers would rather listen to an engine or a machine running than listen to a symphony orchestra. They particularly appreciate a smooth running engine. I drive an old Mercedes that has a lot of miles on it. It is getting a little tired, but it is so incredibly smooth that it is pure pleasure driving it. I also like smooth running airplanes. The smoothest airplane I ever flew was the F-106. To me, it was the Mercedes of airplanes. The X-15 also ran smoothly because the engine had no rotating parts.
My fascination with X-15 engine runs was somewhat diminished when I was scheduled to make the run. Part of this was due to the fact that I could not really see or hear the run as well from the cockpit, and part of it was due to the realization that I would now be sitting in the midst of all that sound and fury, while everyone else was safely tucked away behind the reinforced concrete walls and steel doors of the blockhouse and the pillboxes.
Surprisingly, I really did not think about the danger associated with the rocket engine operation during a flight, but I was very aware of it during a ground run. Part of this may have been due to the fact that during a flight I had many things to think about and do. I was busy and did not have the time to dwell on unpleasant thoughts. During an engine run, I was not that busy. The test sequence was slower than real time and I had time to think about what might happen if something went wrong or a leak developed or a component malfunctioned. I was very aware of sitting in front of an extremely volatile mixture of exotic liquids and gases.
Immediately behind the pilot there was a big 1,000 gallon liquid oxygen tank, almost 5 tons of liquid oxygen. Behind that, there was another huge tank filled with 1,400 gallons of liquid anhydrous ammonia. The ammonia was similar to that used for household cleaning purposes, but it was much more highly concentrated. One whiff of that ammonia would clean your sinuses out for at least 3 months. In addition to those propellants, there were other tanks filled with hydrogen peroxide. Again, this substance was similar to the hydrogen peroxide that you might find in any medicine cabinet, however the concentration of our peroxide was 50 times that of the peroxide for household use. That stuff was really volatile. It was comparable to nitroglycerine in terms of instability.
The older mechanics used to impress the new mechanics by throwing a cup full of that peroxide on a sagebush. The bush would explode in flames. One good quality of hydrogen peroxide is that it gives a warning before it explodes. It gets hot and gives off a very pungent odor. When we smelled hot peroxide, we got the hell out of there.
In addition to these volatile substances, the aircraft was filled with numerous tanks of high pressure helium. These gases pressurized the liquid oxygen and ammonia tanks and the hydrogen peroxide tanks to force the liquids out of the tanks into the feed lines to the engine. These gases also operated various pneumatic valves in the propellant system to initiate the pressurizing of the tank, to open the feed valves to the engine, to open the jettison valves in case we had to jettison fuel in an emergency, and so on. These high-pressure tanks of gaseous helium were latent bombs in and of themselves. If one of those tanks failed, the whole airplane would disintegrate.
I do not know why it seems more dangerous sitting on top of thousands of gallons of highly explosive propellants when only a few gallons will blow a person to bits. Maybe it’s because all the extra gallons will spread the pieces over a wider area and make them harder to find. Maybe that is what worries us psychologically. We kind of hate to end up scattered all over the landscape.
Getting back to my personal thoughts during an engine run, I may have been apprehensive because one of the X-15s had blown up during an engine run with Scott Crossfield in the cockpit. The explosion destroyed the entire rear half of the aircraft and blew the front part of the aircraft out of the test stand. Scott was not injured, thanks to the rugged steel structure of the aircraft, but the explosion really got his attention.
In his book, The Right Stuff, Tom Wolfe discusses the psychological impact of “our rockets blowing up” on the astronauts. The fact that there were numerous rocket booster explosions had to cause some concern among the astronauts even though no one had been riding them when it happened. At that time no one had been killed as a result of those rocket booster explosions. Everyone was safely hunkered down in the blockhouses when they blew.
Tom Wolfe failed to mention that rocket airplanes also frequently exploded. The difference was that there were pilots in the rocket airplanes when they blew up. The X-1D exploded and caught fire in the bomb bay of the B-29 mothership as it was returning to Edwards following an aborted flight. The aircraft had to be jettisoned to save the B-29 and its crew. Luckily, no one was injured since the X-1D pilot had climbed out of the airplane into the mothership after the abort. The number three X-1 blew up in the bomb bay of its B-50 mothership on the ground following a captive flight. The pilot wa
s seriously injured. The number two X-2 exploded in flight in the bomb bay of its B-50 mothership killing the pilot and a crewman and severely damaging the B-50. The X-2 disappeared in the explosion. The X-1A exploded in the bomb bay of the B-29 mothership during flight with Joe Walker in the cockpit. Joe was pulled from the cockpit and the aircraft was jettisoned. These prior rocket aircraft explosions were food for thought as the crew helped us into the cockpit for an engine run.
The crew was always very helpful, making sure that we were securely strapped in so that we could successfully ride out an explosion. The crew hooked up to the radio, the intercom, cooling air, oxygen, and then they shut the canopy and gave a final thumbs up and a wave through the window. Then, they all retreated to the blockhouse and the pillboxes to await the beginning of the engine run sequence. It was very comforting to the pilot in the aircraft to know that the crew was all comfy and cozy in their blastproof shelters. It really eased the pilot’s mind. Personally, I felt that the crew should stay out there with me, so that we could participate in the engine run as a close knit team. Unfortunately, I was not able to convince the crew of that. They preferred the remote teamwork concept.
Occasionally the pilots got a chance to scare the hell out of the crew during an engine run. Normally, the crew came out of their pillboxes to inspect the aircraft and the engine only during stabilized periods of the engine start sequence. They came out the first time to check for leaks after the pilot had pressurized the main propellant tanks. Once that inspection was complete, they would go back into their holes and wait for the next sequence. The next sequence was a jettison check of first, the liquid oxygen and then, the liquid ammonia. When that was completed, they would come out again and check for leaks or any other anomaly. This procedure was followed for each step of the engine start sequence. The crew would only come out after everything was stabilized because the chances of an explosion were much less after things had stabilized. The crew was very cautious about getting under cover before the next event was initiated. Knowing this, the pilot would occasionally pretend that he heard a call to begin the next sequence while the crew was still climbing around the aircraft. The pilot might say, over the radio and intercom net, “Did you say go to prime?” or “Go to pump idle?” This would create an absolute panic with crew members jumping off the aircraft and running for their pillbox.
At the Edge of Space Page 10
