I realized I was not the only one who experienced these feelings of isolation when I spent several months serving as a technical advisor to a motion picture crew that produced the movie, “The X-15 Story.” It was not the greatest movie in the world, but it did have some good flight footage in it. It also featured a couple of rising stars—Mary Tyler Moore and Charles Bronson. One of the actors was suited up for a scene in the X-15 cockpit. We put a g suit on him and then a pressure suit outer garment to simulate a pressure suit. The script called for him to walk out to the X-15 which was hanging on the B-52, get into the cockpit, and close the canopy.
The actor made it up the stairs and into the cockpit. He also tolerated being strapped into the seat and closing his faceplate. When the canopy was lowered into position and locked, however, he panicked. He began pounding on the canopy windows to get out. The director eliminated that scene from the movie. In retrospect, I can understand how he felt, but I guess my incentive to endure it was higher.
I remember the glorious feeling I would get when that canopy was raised after landing and I could open the faceplate and smell the beautiful fresh air. Conversely, at the same time, there was a feeling that someone was invading my privacy when they opened the canopy. In that cockpit, I was in my own little world. I was comfortable and secure and protected from harm. I had complete control over the environment in the cockpit. I could make it hot or cold, light or dark. I could tune in or tune out the world with my radio volume control. The cockpit should have been equipped with a “Do Not Disturb” sign.
The unique carry arrangement of the X-15 on the B-52 resulted in some harsh sounding mission rules. For example, if the B-52 developed a major problem, the crew was allowed to drop the X-15, at their discretion. This sounded a little hard-hearted to the X-15 pilot at first, but then after thinking about it he could accept the fact that it would be better to save the three B-52 crew members if they could do so by getting rid of the X-15. What seemed harder to accept was that if the X-15 pilot had aircraft problems that might endanger the B-52, they could again jettison him.
During most of the captive portion of the flight, the X-15 was not ready to drop. Most of the systems were inactive, including the vital control system. X-15 systems were not activated until 12 minutes before launch, due to the limited duration of the on-board power supply. Thus, if the X-15 were dropped in an emergency, the X-15 pilot really had a bucket of worms to untangle before he had a flyable aircraft.
It was even worse if he was at low altitude or not within gliding distance of a landing site, because then he had to try to start the rocket engine from scratch to get some altitude. If possible, the B-52 crew would delay jettisoning the X-15 until the X-15 pilot could start the APUs. In the worst possible situation, however, it was every man for himself and dump the X-15. This never happened during the X-15 program. We had several emergencies during captive flight but the B-52 crew always brought the X-15 home.
A premature launch due to an emergency only happened once to my knowledge during the many rocket airplane programs. As I indicated earlier, these rules may sound cold-hearted, but on the other hand, the X-15 pilot felt he was the lucky one since he had his own lifeboat, if the B-52 developed serious problems. He could drop himself and leave the B-52 crew to handle their own difficulties. In this total scenario, regardless of whether you are an optimist or a pessimist, you are right. As a last resort, there was the ejection seat in the X-15, which could be used before or after launch.
Once the X-15 canopy was closed, the pace picked up as the access stands were removed, the B-52 engines started and the B-52 hatches and access panels closed. The B-52 was ready to taxi within 10 minutes after canopy closure. This morning, Chase-1 was standing by on the taxiway to taxi out with us. The B-52 had to taxi either 2 or 5 miles depending on whether the duty runway was two-two or zero-four. We preferred using runway zero-four since this allowed use of the entire lakebed as an overrun if we had problems on takeoff. In fact, we occasionally used the lakebed for takeoff if we had strong crosswinds. This particular morning, we were going to use runway zero-four. Eight to ten ground vehicles usually accompanied the B-52 during the taxi out to the takeoff position.
The B-52 taxi was always a rough ride, as felt in the X-15. It felt like the B-52 had square wheels and, in fact, the B-52 tires usually were out of round due to sitting for an extended period with a heavy load. At the takeoff end of the runway, the B-52 stopped to do its pretakeoff checklist. During this period, Chase-1 made its takeoff to get in position for an airborne pickup of the B-52. The crash and rescue helicopter also took off to get into position to cover the B-52 takeoff. And finally, the X-15 crew pulled the safety pin on the X-15 release hooks. Over the radio, the control tower announced, “Zero zero three, cleared for takeoff.”
In the X-15, the takeoff roll was also a rough ride because the Edwards main runway is rough and uneven at both ends. The B-52 seemed to leap off the runway when it reached flying speed, rather than lift off gently like a normal aircraft. This was a characteristic peculiar to all B-52s. Once airborne, however, the ride smoothed out and the checklist procedures began.
Fitz Fulton was flying the B-52 today, so I settled back for a nice smooth ride out to the launch point. Fitz was an excellent pilot who had years of experience launching rocket aircraft. The B-52 with Chase-1 tucked in beside it, climbed around the Edwards lakebed until it reached at least 25,000 feet before heading out toward the launch point. This was done to ensure that the X-15 had sufficient altitude to make it to a landing site if it had to be dropped in an emergency during the flight out to the launch lake.
At the 12-minute-to-launch point in the checklist, we are beginning to activate the various systems in the X-15 in preparation for launch. The first action is to start the APUs, which provide both hydraulic and electrical power.
Following APU start, we began a checkout of the Minneapolis-Honeywell Flight Control system in the X-15. This was an advanced command augmentation type control system with adaptive gain scheduling. The system checkout was automatically accomplished from the B-52 through a computer that cycles the controls while checking overall system performances.
This control check was somewhat unnerving to the pilot because some electrons were now moving the control system without any inputs from the pilot. He then realized that he was not in direct control of the aircraft with a system such as this. He was only commanding a computer that then responded with its own idea of what is necessary in terms of a control output. As a pilot, you hope the guy who designed this electronic control system knew what he was doing. In fact, you would like him to be in the airplane with you to be exposed to any adverse results.
You finally rationalized that if the control stick and control surfaces ended up back where they started after the control check, the system was probably working correctly. You were therefore rudely shaken out of your false sense of security when the controls did not return to their original position, but instead the stick ended up over in the corner of the cockpit. I do not think any of the X-15 pilots really felt comfortable with that system during the early stage of its development, even though it offered many helpful features. This system was, however, a vital step toward fly-by-wire which finally evolved in the early 1970s.
At 8 minutes to launch, the B-52 began a turn back towards Edwards. The B-52 had been proceeding outbound for 21 minutes since leaving North Base at Edwards. At 4 minutes to launch, the B-52 rolled out of the turn on a heading back to Edwards and I began to activate the propulsion system. At 1 minute to launch, I began activating the engine and at the end of that minute, I launched myself in the X-15.
At this point, let me again say a few words about the launch. It was a surprise no matter how many times I went through it. It felt as if the X-15 exploded off the hooks. In addition, the X-15 always tended to roll off at launch. To minimize the rolloff at launch, we normally put in a little bit of countering aileron.
On this flight I almost forgot to put in some ail
eron because it was not on the checklist. When I did finally remember, my mind momentarily went blank on which direction to put the aileron in. I finally said, “Aha, it’s to the left.” I applied left aileron and then hit the launch switch. The airplane rolled violently to the left at launch and then I realized I had put too much aileron in. I ended up right under the B-52 fuselage. I felt stupid, but I had to smile because I knew the B-52 crew really got a jolt out of the rocket engine starting up right under their feet. It made a big boom on initial startup.
As an X-15 pilot, if you thought you were busy before launch, you were really impressed after launch. Joe Walker used to say that they intentionally kept us busy in the cockpit before launch so that we would not have time to think about the launch and chicken out. After launch, we could not chicken out because we had to really move to get the engine lit, the wings back to level, the nose started up, and the heading corrected. All of this had to be done within the first 5 seconds after launch.
The success of the entire flight depended on how well the pilot flew the airplane in the next 80 or 90 seconds. The engine normally burned approximately 82 seconds at 100 percent thrust. It would burn longer at reduced thrust, but it was much more efficient to use 100 percent thrust to get to the desired test condition and then, if there was any propellant left over, the pilot could throttle back to sustain that test condition.
This particular flight was a heating flight. On heating flights, we went to high velocities at relatively low altitudes, 80,000 to 90,000 feet, to intentionally heat the airplane up and then measure the temperatures and heating rates on various parts of the aircraft. On this particular flight, we were planning to fly as fast as we could but still get some stabilized flight time before the engine burned out.
That meant that we had to shoot for a speed less than the maximum capability to save some fuel for the stabilized flight period. Getting to the desired flight conditions on these heating flights was like trying to thread a needle using vice-grips. The X-15 had so damn much thrust it was almost impossible to accurately hit a desired altitude.
But, back to my flight. I lit the engine while I was still in a 60- degree bank under the B-52 and then rolled wings level and pulled up to 10 degrees angle of attack. Five seconds had elapsed by the time I accomplished all this and I heard NASA-1 call, “Good light, Milt.” A quick check of the rocket engine instruments indicated that it was functioning properly and putting out full thrust. NASA-1 called and said, “Should be coming up on alpha.” Seven seconds, turned 3 degrees right to correct my heading. Nine seconds. Ten seconds. Checked angle of attack, angle of sideslip, roll attitude, rate of climb (it should have been positive by now). Twelve seconds, I lost the horizon now because the nose of the aircraft was 10 degrees above the horizon and the small windows cut off my downward view. Thirteen seconds, rolled the wings level to stop my turn and held my planned heading. Fifteen seconds, 16 seconds, cross-checked angle of sideslip, normal acceleration to make sure that I did not exceed 2 g and checked my pitch attitude vernier needle since it should be coming off the peg soon. Seventeen seconds, 18 seconds, the pitch attitude vernier needle is now moving toward the null position. Twenty seconds, 21 seconds, and the pitch attitude needle is now centered and I ease off on angle of attack to maintain the planned 25-degree climb angle.
NASA-1 called and said, “You should be on theta (pitch attitude) now.” I then had a little time to relax. NASA-1 reported, “Track looks real good.” All I had to do was lock on that pitch attitude, keep my heading constant, and cross-check altitude and velocity versus time. I should have been back above launch altitude after losing 3,000 to 4,000 feet during the roundout and my velocity should have been about 1,600 feet per second or roughly 1.6 Mach number.
The rate of climb was starting to build up rapidly. NASA-1 called, “Coming up on profile real nice.” Thirty-one seconds, cross-checked altitude, velocity, and rate of climb versus time. Rechecked engine instruments, hydraulic pressures, generators, APU bearing temperatures, stabilizer position, and a few other mundane items. Thirty-five seconds, 36 seconds. Tried to get a little more comfortable in the seat because the g forces pushing me back in the seat were over 2 and building up fast. NASA-1 called and said, “Standby for pushover.” Forty-one seconds, time to push over, but first checked altitude and velocity.
I should have had 62,000 feet altitude, 2,600 feet per second velocity and about 1,000 feet per second rate of climb (60,000 feet per minute). I was not quite at 62,000 so I delayed pushover a half a second and then pushed over to 0 g. I reset the trim to maintain 0 g and then, again went through a cross-check of my instrument panel. Everything still looked good. NASA-1 called, “Beautiful profile,” meaning that my altitude versus time was right on schedule. Fifty-two seconds, 53 seconds. NASA-1 reported, “Right on track and profile.” Fifty-seven seconds, NASA-1 called and said, “Standby for your left roll, Milt.” At 61 seconds, the flight plan called for a left roll to 90 degrees bank angle and a pullup to 10 degrees angle of attack. At 60 seconds, I checked altitude and velocity. I should have had 80,000 feet altitude and 3,900 feet per second velocity and I was almost there, so I rolled over as planned and pulled up in angle of attack.
I could now see the ground and horizon again through my left window and I recognized some landmarks down below. A quick cross-check of my instruments indicated that everything was normal. NASA-1 called and said, “Nice profile.” Sixty-four seconds. Sixty-five seconds and NASA-1 reported, “Standby for minimum thrust and speed brakes.” At 71 seconds I was scheduled to reduce throttle to minimum thrust and open the speed brakes partially to slow the rate of acceleration or speed buildup. At 71 seconds I was right on speed, 4,750 feet per second or 4.75 Mach number—and on altitude—88,500 feet. I lurched forward to reach the throttle since the g force pushing me back in the seat was over 3 g, and I slowly retarded it to minimum thrust. You always treated a rocket respectfully, particularly when it came to throttling it down. It was very temperamental.
On a previous flight the engine had quit when I throttled back. I did not get home on that flight. On yet another flight, the engine shut down as I retarded the throttle too far and unported the fuel lines. On that flight I got home, but I did not get the planned test maneuvers at high speed.
I started the speed brakes out to reduce my longitudinal acceleration to near 0 and then concentrated on maintaining 10 degrees angle of attack and 90 degrees bank angle. At these flight conditions, my dynamic pressure should read about 600 pounds per square foot. Dynamic pressure is the pressure of the air impacting against the aircraft. If you could hold your hand out the window palm first, at 600 pounds per square foot, you would have roughly 100 pounds pushing on your hand.
Dynamic pressure was the key parameter that we wanted to control on this flight. We wanted to maintain a constant 600 pounds per square foot while we measured the rate of heating of the aircraft structure. We had made measurements of the heating rate at these conditions in a wind tunnel and we wanted to determine if the actual heating rate in flight was the same as that predicted in the wind tunnel. Verifying wind tunnel predictions is one of the primary objectives in flying research aircraft. We want to ensure that the wind tunnels accurately predict the real flight conditions when we begin to design the operational aircraft that will follow along after the research aircraft. We cannot afford to put a lot of design margin, excess structural strength, in an operational aircraft. We had a lot of design margin in the X-15, since we were not exactly sure what the real flight environment was like at hypersonic speeds, when the X-15 was designed.
In the X-15, we were probing the so called thermal barrier for the first time in a manned aircraft. Research aircraft generally were designed with a lot of structural margin. The X-1s, for example, were designed to withstand 18 g in case they went out of control and swapped ends. One X-1 did tumble on one of Chuck Yeager’s flights.
Now, back to my flight again. From 71 seconds to 80 seconds, I held dynamic pressure constant while the speed
gradually built up to about 5,000 feet per second. To keep dynamic pressure constant, I had to gradually increase altitude as the speed built up. At 80 seconds, my altitude was about 93,000 feet and I was scheduled to increase my angle of attack to 17 degrees and bring the speed brakes back in to maintain a slow speed buildup. This would put me in a stabilized 4 g turn.
NASA-1 called at 80 seconds and said “17 degrees, speed brakes in and check H dot.” From 80 seconds to 90 seconds, I was to continue holding a constant dynamic pressure while speed and altitude slowly built up. At 83 seconds, NASA-1 called and said, “Beautiful profile.” At 90 seconds, the engine should have burned all the fuel and shut down. By that time I should have reached 92,000 feet altitude and 5,100 feet per second velocity. At 87 seconds, NASA-1 said, “Standby for your burnout.” Ninety seconds came and went and the engine kept burning. Ninety-one seconds, 92 seconds, 93 seconds, 94 seconds, and still no engine shutdown.
At this time I had mixed emotions. I was in a 4 g turn, turning away from Edwards. I did not want to turn too far away from Edwards, because I might have trouble getting back. On the other hand, I was getting some beautiful data. I was in a very smooth 4 g turn at exactly 600 pounds dynamic pressure—an ideal condition to get good heating rate data. So I decided to sit tight and wait for burnout. I assumed it had to burn out within another second. Ninety-five seconds, 96 seconds, 97 seconds, 98 seconds, and still no burnout. That was just too much time. I decided I had better reverse the turn to get the airplane headed back toward Edwards, and pick up the next test maneuver which was a 60-degree right bank at about 2.4 g to gather more heating data while the aircraft decelerated after burnout.
As I reversed the turn, NASA-1 called and said, “OK, shut it off, Milt.” They, too, were concerned about the extra burn time. To the average person, 8 seconds of extra burn time may not seem like much, but to a rocket expert, 8 seconds of extra burn time is extremely unlikely. Burn rate does not vary that much at the same thrust level. In all our previous X-15 flights (over one hundred flights), we had never seen more than 2 or 3 seconds of variation in burn time at the most. True, I was at a reduced throttle setting and that 8 seconds was probably equivalent to 5 seconds of burn time at 100 percent throttle, but still that was an unbelievably long burn time.
At the Edge of Space Page 25
