We always planned our flights to have more than enough energy to get home. Thus, our primary energy management task was to dissipate the excess energy that we had before we arrived at Edwards, to ensure that we did not go whizzing on by, unable to get back home. Our primary means of dissipating energy was to use our speed brakes. This is the same technique used in gliders or sailplanes to make precise landings during gliding flight.
The pilot of the X-15 was unable to accomplish this energy management task at high speed and altitude on his own due to the high levels of energy involved. He could not simply look out the window and decide if he could glide another 100 or 200 miles. He had to rely on the control room to provide that information. The pilot could successfully judge energy at the lower energy levels. The unpowered landing approach is an exercise in energy management. In order to make a precise landing on a preselected runway, the pilot would look out the window while turning and using speed brakes as necessary.
In a normal flight operation, the X-15 would be carried out to the selected launch lake and then launched in the direction of Edwards. Normal launch conditions were 0.8 Mach at 45,000 feet altitude. The X-15 pilot would light the rocket engine and then climb and accelerate up to the desired test conditions. Depending on the specific flight plan, he would either shut the engine down or let it burn until the fuel was exhausted. After engine shutdown, the pilot would maneuver the airplane back to Edwards in gliding flight and then make an unpowered or deadstick landing. During the flight the pilot would perform various research maneuvers as called for in the flight plan or he would activate various experiments that were being carried on the airplane.
There were two basic types of flights made in the X-15, atmospheric flights and altitude flights. The atmospheric flights were made within the atmosphere generally below 100,000 feet altitude. In these flights, the X-15 was flying much like a normal airplane. The wings were developing lift and we could turn and maneuver like we could in a conventional airplane. On these flights, after launch, the pilot would establish a moderate climb angle and then begin a pushover at 60,000 to 70,000 feet altitude to come level below 100,000 feet altitude. The final portion of the flight, before engine burnout, would be in level flight either at a stabilized speed to gather data or in accelerating flight to achieve a high speed. The maximum speed flights were typical of these flights. After engine burnout, the pilot would glide back to Edwards in a shallow descent.
Altitude flights involved a steep climb out of the atmosphere, followed by a ballistic trajectory up to peak altitude, then a steep descent back into the atmosphere, a pullout to level flight after entering the atmosphere, and then a glide back to Edwards in a shallow descent. An altitude flight was a short duration space flight. We left the atmosphere and for 2 to 5 minutes, depending on peak altitude, we were weightless in a 0 g space environment. We could not turn or change our flight path outside the atmosphere. We could only control aircraft attitude through the use of reaction controls. We made an exit of the earth’s atmosphere and a reentry just like any other spacecraft.
The big difference between the X-15 and a spacecraft is that we did not have enough velocity to stay outside the atmosphere. That would have required speeds of 18,000 MPH. Our maximum speed was 4,500 MPH. Our space flights were up and down, much like Al Shepard’s first suborbital flight. Our space flights were also like the flight of a ballistic missile, except that we could make a pullout when we reentered the atmosphere and glide down to a landing.
Early in the development of the X-15, it became obvious that the X-15 would require a long test range to conduct its high-speed and high-altitude flights. A tracking and telemetry range was set up with three sites, one at Edwards, one at Beatty, Nevada, and one at Ely, Nevada. Each of these sites had an FPS-16 radar installation, telemetry receiving antennas and two way voice communications. These sites were initially autonomous, but subsequently linked via microwave to transmit radar and telemetry data in real time between sites. The three sites were spaced roughly 200 miles apart and spanned a total distance of almost 400 miles. From these three sites, we could track the X-15 anywhere in the state of Nevada and the lower portion of the state of California.
Figure 4. Typical X-15 altitude mission.
The radar data from these tracking stations was used to monitor the track, profile, and total energy of the X-15. The telemetry data was used to monitor various systems in the aircraft and safety of flight data. We were monitoring the same kinds and type of data on the X-15 that NASA is currently monitoring on the space shuttle. In fact, much of our research aircraft operational experience at NASA Dryden was passed on to the space program through key individuals who transferred to the original Space Task Group, planning for Project Mercury, the first American in space venture.
Walt Williams, the first chief of the NASA Dryden Center became the deputy for flight operations to Bob Gilruth who headed the Space Task Group. Williams, along with a number of other Dryden personnel who also transferred, established a space version of Dryden’s experimental aircraft test complex. Many of the flight test procedures developed at Dryden were applied directly to the Mercury spacecraft flight operation. The man who developed the X-15 tracking range, Gerry Truszynski, transferred to NASA headquarters and proceeded to develop the space tracking net and later the Deep Space Tracking Network. He subsequently became NASA’s Chief of Tracking and Data Acquisition.
The data received at the X-15 tracking sites was used to vector the X-15 to Edwards or to an alternate landing site, if a problem developed which prevented the X-15 from making it home to Edwards. Early in the program, we had a control room at each site because we were unable to transfer information in real time between sites. That, of course, meant that each control room had to be manned on each flight by a controller and a team of engineers to monitor safety of flight data in real time. This requirement further added to the complexity of the support operation for each flight. These control room teams had to fly up to the sites the night before to be able to check the control room out and be ready for the flight the next morning. These teams rarely got much sleep the night before a flight because the bars and gambling casinos in Beatty and Ely stayed open most of the night. The bordellos stayed open all night. Pilots were used as controllers at these uprange sites, so we all spent plenty of time in Beatty and Ely, Nevada.
The NASA pilots also piloted the Gooney Bird that we used to haul the teams back and forth. I logged a lot of flight time in our R4D (the navy version of a C-47) flying up and down the X-15 tracking range. The NASA pilots also had to fly range checkout flights to exercise the radar and telemetry tracking systems. On these flights, we simply flew uprange and then flew back down the intended track of the upcoming X-15 flight to allow the individual sites to track the aircraft and exercise the total X-15 Hi Range System.
We used our support airplanes, T-33, F-100, or F-104 aircraft, to make these flights. We would simulate emergency approaches into each of the intermediate lakes to give the radar technicians some practice tracking a simulated X-15 flight. The radar people would lose us on radar a few thousand feet above the lakebed due to curvature of the earth or intervening mountains. I used to love to stay low after a simulated emergency approach to a lakebed and then sneak back up on the tracking site. I would stay below 50 feet and would be traveling at close to 600 knots as I approached the site. As I passed over the site, I would light the afterburner and do a roll. When I used that technique, they could not see or hear me coming. As I passed over, the noise was like a bomb going off. Even though the crews manning these sites knew I liked to do this and were expecting it, it still scared the hell out of them when I went over. They claimed that I shook the radar loose in its mount over a period of time because of those low passes. These stunts did relieve the boredom for the crews that were permanently stationed at these sites. These sites were located on some of the most desolate terrain in the inland desert. Even the lizards would avoid the Beatty site. One might see an occasional sidewinder, bu
t not much else.
There was a small lakebed just west of the Beatty tracking site that we used as an airstrip to haul people and supplies to the site. It was less than a mile in diameter, but it was adequate to get the Gooney Bird in and out. We occasionally used our Aero Commander to make this same trip, however, it was a little dicier to maneuver that airplane particularly with a full load of passengers on a hot day. The Beatty site was less than 20 miles from Death Valley, so it did get hot. My favorite trick to get airborne under those conditions was to start accelerating around the edge of the lake and then turn in toward the center for the final takeoff.
On one trip, prior to takeoff out of that lakebed, I could not get the left engine started on the Aero Commander. I asked Ron Waite, one of the X-15 operations engineers, to get out and pull the prop through backwards. That was an old trick that I had learned as a crop duster pilot. Ron Waite had worked previously as an engineer for Pratt & Whitney. He had never heard of such a procedure. He thought I was kidding. When he realized that I meant it, he insisted that I shut all the switches off for that engine and then hold my hands out the window so that he could see them while he was pulling the prop through. I guess he did not trust me.
Ron had never propped an engine in his entire career. While in college I flew crop dusters. We used to routinely prop the 450 HP engine on our duster aircraft. I did not necessarily like to do it, but it came with the job. Propellers could be scary. I will never forget moving around among the airplanes on an aircraft carrier deck in the late 1940s when the aircraft were all fired up and the propellers were turning prior to takeoff. That was scary.
But back to the desert, I used to enjoy the trips up to the Beatty and Ely sites. I made most of the trips at treetop level, even though there were not a lot of trees. I enjoyed buzzing the desert looking for coyotes and other animal life. There were no traffic rules or regulations up in that desert region. We did what we pleased while flying in that area. We felt that we owned that desert territory, even though much of it was outside the Edwards restricted area. We owned it by the right of eminent domain. We lived in that airspace. The only area that we avoided was the atomic energy test area and a restricted test site dubbed “The Ranch.” The remainder of the inland desert was our territory.
It was really fun to fly in that time period. Just before I quit flying, the FAA and the military began tightening the rules in the Edwards test area. The joy slowly went out of flying for me as they began to control all traffic, even though I refused to comply with their regulations on local proficiency flights. I just would not tell them where I was going or what I was going to do. I am glad I quit test flying when I did. I would hate to have someone monitoring my every move during a proficiency flight. Flying should be fun. I had always managed to enjoy my flying career before that time.
A minimum of three and a maximum of five chase planes were used on X-15 flights. Three chase were used on the early low-speed X-15 flights that were launched in the immediate Edwards area. Four chase were used for the major portion of the flights and five were used for the longer range flights out of Smith Ranch.
Chase-1 was the prelaunch chase. This chase took off with the B-52 and stayed with it throughout the entire prelaunch checkout procedure. An F-100 aircraft was used during the first few years of the program and later a T-38. Chase-1 was normally flown by a USAF pilot. This chase flew tight formation on the B-52/X-15 combination to monitor various checklist procedures which involved visible X-15 activities such as control surface movements, propellant jettison checks, ballistic control system checks, APU start, engine start cycle, and control surface trim checks. This chase also provided independent airspeed, altitude, and heading checks, and served as a lookout for conflicting traffic.
Chase-2 was the launch chase. It took over as the prime chase at 1 minute to launch. An F-104 aircraft was used and it was normally flown by a NASA pilot. This chase took off as the B-52 was departing the Edwards area on its outbound leg to the launch point. The chase served as the landing chase for any emergency landings that might be required either before or shortly after launch. This chase trailed the B-52 out to the launch point. After launch it chased the X-15 until the plane left the launch lake area or followed the X-15 down to a launch lake landing if the engine failed to light or shut down prematurely.
Chase-1 and -2 were somewhat redundant in coverage of the flight, however, we did not have one kind of aircraft that could do both missions well. Neither the F-100 or the T-38 could follow the X-15 down to a landing. They could not produce enough drag to reduce their lift-drag ratio to match that of the X-15. Only the F-104 could do that. The F-104, conversely, could not fly formation on the B-52 throughout the flight up to launch. The F-104 would not cruise at 45,000 feet due to its high-wing loading.
Chase-2 normally trailed the B-52 outbound at 35,000 feet. Then about 3 minutes to launch, the pilot would light the afterburner and begin a climb to arrive at 45,000 feet in formation with the B-52 at 1 minute to launch. To maintain formation, the F-104 pilot had to use minimum afterburner and partial speed brakes—an ungodly way to fly. If he timed it just right, he did not have to fly formation for more than a minute. If he did not, he used up a lot of gas.
Chase-2 was almost always low on fuel at launch and usually landed back at Edwards with the low-fuel light on. It was especially bad if some problem caused a ten minute hold. Then the pilot was lucky to get home on a straight-in approach to the North lakebed. Sometimes we resorted to riding the vortex off the B-52 wing tip as a fuel saving maneuver. This could save the chase a lot of gas. It was almost like surfing. The tip vortex was quite strong and when the chase pilot positioned the F-104 in the proper location relative to the wing tip, he could maintain position with about half the power normally required. Ducks and geese have utilized this vortex riding technique for millions of years but never with a B-52.
Chase-3 was the intermediate chase that covered any emergency landings at intermediate lakebeds. An F-104 was used and a NASA pilot usually flew this chase position. This chase took off about 30 minutes prior to launch and orbited over the intermediate lake or between the intermediate lakes if there were more than one. It would attempt to join up with the X-15 and escort it to a landing on the designated emergency lake.
Chase-4 was the chase that covered the Edwards landing. An F-104 was used and the pilot was usually a USAF pilot. This chase also took off about 30 minutes prior to launch. It orbited 30 to 40 miles up the X-15 track from Edwards. The pilot usually began accelerating and climbing along the X-15 track back toward Edwards to rendezvous with the X-15 at the maximum possible speed and altitude as the X-15 descended into the Edwards area. It was a tricky task. Chase-4 was vectored in for rendezvous by radar. Because the X-15 was hard to see due to its small size and dark color, quite often the chase relied on the contrail caused by the jettison of propellant to acquire the X-15. Once rendezvoused, Chase-4 would visually inspect the X-15 and advise the X-15 pilot of any abnormalities. Chase-4 would then provide airspeed, altitude, and position information during the approach as requested by the X-15 pilot. Chase-4 would verify flap and gear extension and call out height above the lakebed during the last few seconds prior to touchdown.
A second intermediate chase was required on the flights out of Smith Ranch to cover all of the intermediate lakes. The maximum distance between intermediate lakes was over 150 miles and the F-104 could not accelerate fast enough to cover a landing at both lakebeds.
We occasionally had sufficient aircraft to have the luxury of a roving chase. This chase served as a backup for Chase-2, -3, -4, or -5. It was usually orbiting about halfway between Edwards and the launch lake.
In all of my years as a research pilot for NASA, I always accepted the fact that a chase was essential for any risky test flight. This was the accepted way of doing business for ourselves and for the entire test community throughout the country. I was very surprised to have Deke Slayton challenge the practice when we became a part of the test team to s
upport the air launch tests of the space shuttle. I think he challenged the need for chase aircraft just to force everyone to reexamine and rejustify the requirement. Before becoming an astronaut, he apparently had a bad experience with a chase aircraft while flying as a test pilot at Edwards. We reviewed our chase experience to determine what benefits the chase actually provided.
Surprisingly, we could only remember one incident in a 20-year-period where the chase had definitely saved an aircraft. This was a real shock. Before we did the study, I would have guessed that there were 50 or 100 incidents wherein the chase saved an aircraft or at least provided crucial information. Not so. We may have forgotten one or two other incidents, but the occurrences of clear-cut saves by the chase were infinitely small. The chase provided helpful information on almost every test flight of every research aircraft, but surprisingly few critical bits of information.
The one major thing that a chase does provide is verification type information which can be psychologically important to the test aircraft pilot. It is damn nice to have a chase with you in an emergency, if for nothing else than to hold your hand. He also makes a good witness during an accident investigation. During the X-15 program, everyone accepted the need for chase aircraft and we did not fly without them. Thank God for that, although when I did have emergencies in the X-15, I personally did not get that much help from the chase.
At the Edge of Space Page 8
