Thompson: “Rog. Flaps coming down.”
Chase-4: “OK, flaps look good, gear looks good, let’s go down. Fifty feet, ten, five, a beauty, Milt. A beauty!”
Thompson: “Where’s the brake?” [I was just kidding, there is no brake.]:
NASA-1: “That little handle on the left.” [NASA-1 was kidding also.]:
Chase-4: “Pull back on the stick.” [Bob Rushworth in Chase 4 wasn’t kidding. Pulling back on the stick did increase the sliding friction.]
Thompson: “How about that!”
NASA-1: “Real nice show, Milt.”
My first X-15 flight lasted exactly 523 seconds. The engine burned for the first 2 minutes of the flight. In those 2 minutes, I climbed to 75,000 feet altitude and accelerated up to 4,100 feet per second or 2,712 miles per hour. That is almost twice as fast as a rifle bullet. After engine shutdown, the X-15 became a hypersonic glider, gliding over 100 miles in a matter of seconds. Five minutes after launch, I was in the landing pattern over the north lakebed at Edwards. The descent from high key to landing lasted just over three and a half minutes. In less than nine minutes after launch, I had learned to fly a new airplane well enough to make a “beautiful” deadstick landing. I guess I was now qualified to join the X-15 program.
When the airplane finally stopped, the recovery convoy converged on me like sharks on a piece of raw meat. The convoy was actually coming to help me, but I could not help but be intimidated by the intensity of their approach to the airplane. The first to arrive was the recovery helicopter. It came in over the airplane at 25 or 30 feet to check for any fire or propellant leak. Then they landed and dropped off an X-15 crew member and a personal equipment specialist. They came running over to the airplane to open the canopy and begin securing the ejection seat. Next came the fire chief in his hopped-up pickup and a series of ground crew vehicles, ground support equipment, crash and fire truck, and finally, the ground control van and the pressure suit van. In all, there were about fifteen or twenty vehicles in the recovery convoy.
It was a fantastic feeling when that canopy opened up. I had been cooped up in that cockpit for over 2 hours and had been exposed to some traumatic new experiences. You cannot believe how good the fresh air smelled. I had made a successful flight. I had climbed Mt. Everest and had made it back safely. I went through the post landing checklist, shut everything down, and then unbuckled with the assistance of the personal equipment specialists. They helped me out of the airplane and the congratulations began.
Paul Bikle, the Dryden director, was there on the lakebed, as was General “Twig” Branch. My wife and four kids were there and, as Ralph Jackson (our public affairs officer) reminded me later, so was my favorite bartender. Ralph had invited him out to watch the flight. It was a pleasant surprise to have my family waiting to greet me on the lakebed, but I could not help but think of what a traumatic experience it would have been if I had pranged the airplane on landing.
I believe I shook hands with 100 people out on the lakebed before the welcoming ceremony was over. It really was a tremendous welcome home. My flight was the ninety-third flight of the program, but the morale was so high among the project team members that it was almost treated like a first flight. In fact, every flight was treated as a significant event and was at least celebrated at Juanita’s in Rosamond after working hours.
I was impressed by a couple of things during the flight. The various g forces imposed on the pilot during powered flight were very conducive to severe vertigo. The eyeballs-in g forces due to the thrust of the engine were much greater than any experienced in conventional airplanes. When these g forces were combined with the eyeballs-down forces during the pullup to the planned climbout angle after launch, the pilot sensed that he had overrotated his climb angle. This was compounded by the visual loss of the horizon out the window.
Every X-15 pilot suffered this disorientation during the climbout and many felt that they were climbing straight up or even going over on their back. The g forces from the engine thrust continued to increase as the aircraft became lighter due to fuel usage and ultimately achieved a level of almost 4.0 g just prior to burnout. This level of g force was not excessive by any means, but it compromised the pilot’s ability to fly the airplane, it restricted his breathing and caused chest pain, and it was just plain annoying. I commented to engineers after the flight that this was the first aircraft that I had flown that I was happy to shut the engine off. The resulting deadstick landing was the lesser of two evils, in my opinion, after that long exposure to that high g environment. Bill Dana loved the comment about being happy to shut the engine off and quoted it in many talks for years after the program ended.
The one other thing that impressed me on this flight was the amount of physical effort required to fly the airplane. I was really exhausted after the flight. Some of that exhaustion was obviously due to the mental stress, but much of it was due to the muscular exertion required to manipulate all the controls and fly the aircraft while fighting the g forces and the resistance of the pressure suit. Following that flight, I immediately embarked on a physical fitness program to get back in shape. Flying the X-15 was definitely not a piece of cake. I felt like I had put in a 12-hour-day digging ditches.
Chapter 6
Trial by Fire and Water
(1964–1968)
My fifth flight was to be a low-speed flight in the number three aircraft to simulate the flight conditions of the proposed Supersonic Transport and to measure the heat transfer rate, the skin friction, and the boundary layer noise at this flight condition. The desired speed was about 2,800 feet per second, or just under Mach 3. In planning the flight, we were looking for the closest launch lake that would still provide some stabilized flight time at Mach 3. The only lake that seemed to fulfill the requirements was Silver Lake, which was approximately 100 miles east of Edwards. It appeared, however, that we could not keep the speed below Mach 3 coming out of Silver Lake without violating one of our basic flight safety ground rules. That rule dictated that a pilot could not retard the throttle until he had enough energy to get home to Edwards. This rule was established as a result of the unstable engine operation at low-thrust settings that was observed during ground runs. The concern was that the engine might shutdown prematurely when the throttle was retarded. This had happened during ground runs and during flight on at least one occasion.
Ed Saltzman, the research engineer who was conducting the experiment, was very adamant about the desired flight conditions. He did not want to exceed Mach 3 while recording his data. I sympathized with him. I had worked as a research engineer before I had become a pilot and I appreciated the importance of obtaining accurate flight conditions. I decided to go with him to argue for special dispensation to make the flight at the lower speed. We went to see Joe Vensel, who was the chief of flight operations. He listened to our argument and then said, “Not only no, but hell no!” He was not about to approve a flight that required a power reduction before the aircraft had enough energy to make it home to Edwards.
Saltzman did not like the decision, but he accepted defeat and went off mumbling about the lack of support for basic research. I was not as smart as Ed. I decided that I would not give up so easily. I had made four X-15 flights. I felt pretty confident in my ability to cope with any problems that might arise during a flight. In fact, I probably felt a little cocky. I kept bugging Joe Vensel to let me fly the flight at the lower speed in the interest of science and to uphold the honor of the pilot’s office. It took a couple of weeks, but I finally wore him down.
The flight was scheduled for May 21, 1964. The B-52 took off at 8:58 A.M. and climbed to 25,000 feet in the immediate vicinity of Edwards before heading outbound to Silver Lake. Everything proceeded smoothly up to launch, except that when I went to pump idle at 10 seconds to launch I did not get second-stage igniter. I had to recycle the pump two times to get second-stage igniter and, as a result, I was about 15 seconds late for launch. The radio conversation at launch included the follo
wing:
Thompson: “OK, pump idle again and we’re all set. Call that three, two, one, launch.”
Chase: “No light.”
NASA-1: “OK, you got a light. OK, you’re coming up on profile. Should have your theta, Milt. Standby for pushover. Get set for throttle back. We have you going just a little high, Milt. How do you read? Shutdown!”
Thompson: “Engine shutdown. Reset, prime, reset, and throttle off.”
NASA-1: “Rog. Malfunction, reset.”
Thompson: “Throttle back.”
NASA-1: “Bring your nose up. Bring your nose up, Milt.”
Thompson: “Throttle’s off.”
NASA-1: “Malfunction. Cuddeback!!”
That conversation tells it all. When I retarded the throttle at 42 seconds as called for in the revised flight plan, the engine quit just as Joe Vensel feared that it would. We did not have enough energy to get to Edwards, so the call came to go to Cuddeback Lake. I tried a couple of engine restart attempts with no luck. A small explosion had occurred in the engine when I throttled back and this precluded any engine restart.
I now had a real emergency on my hands. I was not going to make it home and I might not even make it to Cuddeback Lake. I might have to land on one of the Three Sisters Lakes and they were awfully small compared to Edwards or even Cuddeback, only 2 miles in diameter. The slideout in the X-15 was close to 2 miles long, so if I did not land accurately at the edge of the lake at Three Sisters, I was going to slide off the lake and into the boondocks. Or conversely, if I landed short at over 200 MPH in the sagebrush, I probably would not survive. It was not a nice prospect. I really did not want to land at Three Sisters.
As soon as I realized that I did not get an engine relight, I started the airplane uphill. I was traveling at about Mach 2.9 at shutdown at 55,000 feet altitude, so I had some speed that I could convert to altitude, but I had a long way to go to get to Cuddeback, over 70 miles. As I slowly climbed on up, I started jettisoning propellants to prepare for landing. I did not need that volatile stuff if I had a landing accident. NASA-1 confirmed that I had a good heading to reach Cuddeback and asked that I give them an altitude check as I approached Three Sisters. They informed me that I had to have at least 45,000 feet at Three Sisters to make it in to Cuddeback.
I decided right then that I would lie if necessary about my altitude at Three Sisters. I did not want to land there. I was going to try to make it to Cuddeback. As it turned out, I had plenty of altitude when I reached Three Sisters. I had 60,000 feet. I had to rely on NASA-1 to tell me when I arrived at Three Sisters because I could not see the lakes or Cuddeback. They were under my nose.
As I descended into Cuddeback from Three Sisters, the chase aircraft began to join up. Soon, I had all four chase aircraft on my wing. They had all caught up to me in my slow cross-country flight from Silver Lake. Bob Rushworth finally suggested that a couple of them get out of the way. As I passed over the runway at Cuddeback, I asked for an altitude check and Bob indicated that he had 32,000 feet. He was on my right wing. I was crossing the north-south runway on a westerly heading, so I had plenty of altitude for a 270-degree overhead pattern to the north-south runway. As I proceeded on past the runway to set up my pattern, NASA-1 called and said, “Bring your turn around, Milty, tighten your turn.” That call was somewhat perplexing because from what I could see I had plenty of altitude to make a wide pattern. But since it was an emergency, I thought maybe they knew something that I did not know. I tightened my turn up a bit.
As I continued around the turn, I got another call from NASA-1 to “tighten my turn.” Again, it looked like I was already a little too close in, but the call raised some doubt in my mind. I had never landed at Cuddeback, although I had made many practice approaches there. I really did not want to do it, but I went ahead and tightened my turn a little more. I did not get any advice from my chase to the contrary. As I came around on final, I realized I was way too high. I opened the speed brakes and dumped the nose over to kill off energy. I came down the final approach doing over 350 knots and “S-turning” to kill off more energy. I pulled the speed brakes in while I made the flare, but then put them right back out to slow down to get it on the ground.
Full speed brakes in the landing configuration significantly decreased directional stability. In fact, the airplane became directionally unstable. The nose of the aircraft started to diverge as I leveled out for the landing, but I managed to stop the divergence and finally plunk it on the ground. I was misaligned with the runway as a result of this control problem, but I managed to turn the X-15 after touchdown by applying roll control to load up one skid. This worked very well at high speeds. After the turn, the aircraft slid out right down the center of the runway.
I landed long, about a mile and a half down the runway. The runway was about 3 miles long with a road going across the north end. The road was just a graded track across the north end of the lakebed with dirt piled up on either side. Beyond the road was another half mile of usable lakebed. I had slowed to about 60 knots when I hit the dirt piled up alongside that road. The pile was about a foot and a half high, but I plowed through it like a tank. It was a good jolt, but everything stayed together and I stopped about 300 feet beyond the road. I did not see it, but the fire truck that was standing by on the lakebed for an emergency landing had pulled in behind me during my slideout. The fire truck hit the same dirt pile traveling at my same speed. According to some other observers on the lake, that entire truck flew up in the air 5 feet before coming back down. I had landed safely without any significant damage to the airplane, but now I had to go back home and face Joe Vensel. I almost wished that I had not made it.
The rescue C-130 landed immediately after I did and they flew me back to Edwards after I secured the X-15. One of my cousins and his son came up to watch that flight. They were thoroughly impressed by that flight. As I have said previously, when an emergency occurred, everyone at Edwards held their breath until the airplane was safely on the ground. The silence was deafening on the radio. My cousin witnessed that and was impressed. He never came back to watch another flight.
When I saw Joe at the postflight debriefing, he raised hell like a father would if his kid had narrowly escaped death due to some stupid action. He was mad but mainly because he had been so worried. He swore again that he would never allow the engine to be throttled before the X-15 could make it home. This time he meant it.
I found out at the postflight debriefing that NASA-1 had been misinterpreting their radar map when they were vectoring me around the pattern at Cuddeback. They were misreading the scale on the map when they were telling me to tighten up my turn. We made a decision after that flight to stop vectoring the X-15 once it got into the landing pattern. We felt the pilot could better judge the landing pattern without help from the ground. We only provided help after that if the pilot requested it. In describing the runway on Cuddeback Lake, I had to borrow a line from Jack McKay, “It was 3 miles long with a 300-foot overrun.”
FIRE WARNING
My eighth flight was a flight to measure acoustic noise in the boundary layer. Acoustic noise is of interest to aircraft designers because it can cause aircraft skin panels to vibrate and ultimately to fail due to fatigue. The boundary layer is a term to describe the layer of air between the skin of the aircraft and the free stream air. A boundary layer is a natural occurring phenomenon on any object moving through the air. In a boundary layer, the velocity of the air varies from zero on the surface of the object to the speed with which that object is traveling through the air.
Thus, in a car traveling 80 MPH, the velocity of the air next to the surface of the car is zero, while the velocity of the air outside of the boundary layer is 80 MPH. The boundary layer varies in thickness from a few thousandths of an inch on the front of the car to several inches at the rear of the car. The air in a boundary layer can do strange things. It can flow in different directions and it can even move forward.
The aircraft designer is very intere
sted in the characteristics of this boundary layer since it can impact the design of the aircraft in many ways. For example, if the boundary layer is predicted to be thick on a particular aircraft configuration at the desired operating speed, then the engine inlets may have to be moved out away from the skin of the fuselage to capture the high-speed air rather than the stagnant air next to the fuselage. If the boundary layer air is turbulent, the aerodynamic heating rate is higher and the airplane will get hotter. The designer will then have to build in some extra heat protection for the aircraft structure.
It offered the first opportunity to measure the characteristics of the airflow at hypersonic speeds. These characteristics were important to the designers of future hypersonic aircraft. The wind tunnels provided some clues as to these characteristics, but some actual flight data were needed to confirm the wind tunnel data. The X-15 provided much of the aerodynamic data needed to validate the hypersonic wind tunnels.
My eighth flight was one small step in this process. It was a rather benign flight plan calling for a climb and acceleration up to 80,000 feet at Mach 4.5. After engine shutdown, I was to make a mild 2 g left turn and then later a 2.5 g right turn while maintaining a constant dynamic pressure. After recording data in these maneuvers, I was to vector to high key at Edwards while doing some handling quality evaluations using the center stick with the roll and yaw stability augmentation system turned off. At high key, I was to terminate the research maneuvers and commence the approach to landing. This flight promised to be an easy one. I could sit back and enjoy this one.
Things went well up until 4 minutes to launch at which time NASA-1 lost telemetry data. Telemetry data was essential for flight. I asked Jack McKay, who was the controller in NASA-1, what we were going to do. He informed me that we would proceed with the checklist for the time being. I continued on down the checklist to the one minute point and got another call from NASA-1 to continue on even though they were still not receiving telemetry data.
At the Edge of Space Page 23
