Joseph Albert Walker in the cockpit of North American Aviation X-15A 56-6670, after a flight, 1960. (NASA)
24 March 1960: After North American Aviation’s Chief Engineering Test Pilot, Albert Scott Crossfield, had made the first flights in the new X-15 hypersonic research rocketplane (one gliding, eight powered), NASA Chief Test Pilot Joseph Albert Walker made his first familiarization flight.
The X-15, 56-6670, the first of three built by North American Aviation, Inc., was carried aloft under the right wing of a Boeing NB-52A Stratofortress, 52-003, flown by John E. Allavie and Fitzhugh L. Fulton.
Fitz Fulton and and Jack Allavie with a Boeing NB-52 drop ship. (Jet Pilot Overseas)
The rocketplane was dropped from the mothership over Rosamond Dry Lake at 15:43:23.0 local time, and Joe Walker ignited the Reaction Motors XLR-11 rocket engine. The engine burned for 272.0 seconds, accelerating Walker and the X-15 to Mach 2.0 (1,320 miles per hour/2,124.3 kilometers per hour) and a peak altitude of 48,630 feet (14,822.4 meters). Walker landed on Rogers Dry Lake at Edwards Air Force Base after a flight of 9 minutes, 8.0 seconds.
Joe Walker made 25 flights in the three X-15 rocket planes from 24 March 1960 to 22 August 1963. He achieved a maximum Mach number of 5.92, maximum speed of 4,104 miles per hour (6,605 kilometers per hour) and maximum altitude of 354,200 feet (107,960 meters).
Joe Walker with the Number 2 North American Aviation X-15, 56-6671, on Rogers Dry Lake. (NASA)
Joe Walker was killed in a mid-air collision between his Lockheed F-104N Starfighter and a North American Aviation XB-70A Valkyrie near Barstow, California, 1 June 1966.
The number one ship, 56-6670, made 81 of the 199 flights of the X-15 Program. It was the first to fly, and also the last, 24 October 1968. Today, it is in the collection of the Smithsonian Institution National Air and Space Museum.
North American Aviation, Inc. X-15A 56-6670 on Rogers Dry Lake, Edwards Air Force Base, California. (NASA)
6 November 1958: NASA Research Test Pilot John B. (Jack) McKay made the final flight of the X-1 rocketplane program, which had begun twelve years earlier.
Bell X-1E 46-063 made its 26th and final flight after being dropped from a Boeing B-29 Superfortress over Edwards Air Force Base on a flight to test a new rocket fuel.
John B. McKay, NACA/NASA Research Test Pilot. (NASA)
When the aircraft was inspected after the flight, a crack was found in a structural bulkhead. A decision was made to retire the X-1E and the flight test program was ended.
The X-1E had been modified from the third XS-1, 46-063. It used a thinner wing and had an improved fuel system. The most obvious visible difference is the cockpit, which was changed to provide for an ejection seat. Hundreds of sensors were built into the aircraft’s surfaces to measure air pressure and temperature.
The Bell X-1E was 31 feet (9.449 meters) long, with a wingspan of 22 feet, 10 inches (6.960 meters). The rocketplane’s empty weight was 6,850 pounds (3,107 kilograms) and fully loaded, it weighed 14,750 pounds (6,690 kilograms). The rocketplane was powered by a Reaction Motors XLR11-RM-5 rocket engine which produced 6,000 pounds of thrust (26.689 kilonewtons). The engine burned ethyl alcohol and liquid oxygen. The X-1E carried enough propellants for 4 minutes, 45 seconds burn.
The Bell X-1E rocketplane being loaded into NACA 800, a Boeing B-29-96-BW Superfortress mothership, 45-21800, for another test flight. (NASA)
The early aircraft, the XS-1 (later redesignated X-1), which U.S. Air Force test pilot Charles E. (“Chuck”) Yeager flew faster than sound on 14 October 1947, were intended to explore flight in the high subsonic and low supersonic range. There were three X-1 rocketplanes. Yeager’s Glamorous Glennis was 46-062. The X-1D (which was destroyed in an accidental explosion after a single glide flight) and the X-1E were built to investigate the effects of frictional aerodynamic heating in the higher supersonic ranges from Mach 1 to Mach 2.
Bell X-1E 46-063 loaded aboard NACA 800, a Boeing B-29-96-BW Superfortress, 45-21800, circa 1955. (NASA)
The X-1E reached its fastest speed with NASA test pilot Joseph Albert Walker, at Mach 2.24 (1,450 miles per hour/2,334 kilometers per hour), 8 October 1957. Walker also flew it to its peak altitude, 70,046 feet (21,350 meters) on 14 May 1958.
NACA test pilot Joseph Albert Walker made 21 of the X-1E’s 26 flights. In this photograph, Joe Walker is wearing a David Clark Co. T-1 capstan-type partial-pressure suit with a K-1 helmet for protection at high altitudes. (NASA)
There were a total of 236 flights made by the X-1, X-1A, X-1B, X-1D and X-1E. The X-1 program was sponsored by the National Advisory Committee on Aeronautics, NACA, which became the National Aeronautics and Space Administration, NASA, on 29 June 1958.
NACA’s chief project test pilot for the Douglas X-3, Joe Walker, in the cockpit of the research aircraft, circa 1954-1956. (LIFE Magazine via Jet Pilot Overseas)
October 27, 1954: Between August 1954 and May 1956, Joseph A. Walker, the National Advisory Committee for Aeronautics’ chief project test pilot for the Douglas X-3 supersonic research aircraft, made twenty research flights in the “Stiletto.”
On the tenth flight, 27 October, Walker took the X-3 to an altitude of 30,000 feet (9,144 meters). With the rudder centered, he put the X-3 into abrupt left aileron rolls, first at 0.92 Mach and then at Mach 1.05. Both times, the aircraft violently yawed to the right and then pitched down. Walker was able to recover before the X-3 was completely out of control.
The Douglas X-3 during NACA flight testing, 1954-1956. (LIFE Magazine via Jet Pilot Overseas)
This was a new and little understood condition called inertial roll coupling. It was a result of the aircraft’s mass being concentrated within its fuselage, the gyroscopic effect of the turbojet engines and the inability of the wings and control surfaces to stabilize the airplane and overcome its rolling tendency. (Just two weeks earlier, North American Aviation’s Chief Test Pilot George S. Welch had been killed when the F-100A Super Sabre that he was testing also encountered inertial roll coupling and disintegrated.)
A post-flight inspection found that the X-3 had reached its maximum design load. The airplane was grounded for the next 11 months.
Unlike its predecessors, the Bell Aircraft Corporation’s X1 and and X-2 rocketplanes, the turbojet-powered Douglas X-3 took off under its own power. Here, its two Westinghouse J37 engines are stirring up the sand on Runway 35 at Rogers Dry Lake. (LIFE Magazine via jet Pilot Overseas)
The Douglas X-3, serial number 49-2892, was built for the Air Force and NACA to explore flight in the Mach 1 to Mach 2 range. It was radically shaped, with a needle-sharp nose, very long thin fuselage and small straight wings. Two X-3 aircraft had been ordered from Douglas, but only one completed.
The X-3 was 66 feet, 9 inches (20.345 meters) long, with a wing span of just 22 feet, 8.25 inches (6.915 meters). The overall height was 12 feet, 6.3 inches (3.818 meters). The X-3 had an empty weight of 16,120 pounds (7,312 kilograms) and maximum takeoff weight of 23,840 pounds (10,814 kilograms).
It was to have been powered by two Westinghouse J46 engines, but when those were unsatisfactory, two Westinghouse XJ34-WE-17 engines were substituted. This was an axial flow turbojet with an 11-stage compressor and 2-stage turbine. It was rated at 3,370 pounds (14.99 kilonewtons) of thrust, and 4,900 pounds (21.80 kilonewtons) with afterburner. The XJ34-WE-17 was 14 feet, 9.0 inches (4.496 meters) long, 2 feet, 1.0 inch (0.635 meters) in diameter and weighed 1,698 pounds (770 kilograms).
The X-3 had a maximum speed of 706 miles per hour (1,136 kilometers per hour) and a service ceiling of 38,000 feet (11,582 meters).
The X-3 was very underpowered with the J37 engines, and could just reach Mach 1 in a shallow dive. The X-3′s highest speed, Mach 1.208, required a 30° dive. It was therefore never able to be used in flight testing the supersonic speed range for which it was designed. Because of its design characteristics, though, it was very useful in exploring stability and control in the transonic range.
At one point, replacing the X-3’s turbojet engines with two Reaction Motors XLR-11 rocket engines was considered. Predictions were that a rocket-powered X-3 could reach Mach 4.2. However, with Mach 2 Lockheed F-104 becoming operational and North American Aviation’s X-15 hypersonic research rocketplane under construction, the idea was dropped. Technology had passed the X-3 by.
In addition to Douglas Aircraft test pilot Bill Bridgeman, the Douglas X-3 was flown by Air Force test pilots Lieutenant Colonel Frank Everest and Major Chuck Yeager and NACA pilot Joe Walker.
Joe Walker resumed flight testing the X-3 in 1955. Its final flight was 23 May 1956. After the flight test program came to an end, the X-3 was turned over to the National Museum of the United States Air Force, Wright-Patterson Air Force Base, Ohio.
NACA test pilot Joe Walker with the Douglas X-3. (LIFE Magazine via Jet Pilot Overseas)
Joe Walker and the X-15 on Rogers Dry Lake at the end of a flight. Walker is wearing a David Clark Co. MC-2 full-pressure suit. (U.S. Air Force)
22 August 1963: On his twenty-fifth and last flight with the X-15 program, NASA Chief Research Test Pilot Joseph Albert Walker would attempt a flight to Maximum Altitude. Engineers had predicted that the X-15 was capable of reaching 400,000 feet (121,920 meters) but simulations had shown that a safe reentry from that altitude was risky. For this flight, Flight 91, the flight plan called for 360,000 feet (109,728 meters) to give Walker a safety margin. Experience had shown that slight variations in engine thrust and climb angle could cause large overshoots in peak altitude, so this was not considered an excessive safety margin.
For this flight, Joe Walker flew the Number 3 X-15, 56-6672. It was the only one of the three North American Aviation X-15s equipped with the Honeywell MH-96 flight control system, which had been developed to improve control of the rocketplane outside Earth’s atmosphere. This flight was the twenty-second for Number 3.
North American Aviation X-15A 56-6672 immediately after being dropped by the Boeing NB-52 Stratofortress. (NASA)
Walker and the X-15 were airdropped from the Boeing NB-52A Stratofortress 52-003, The High and Mighty One, at 45,000 feet (13,716 meters) above Smith Ranch Dry Lake, Nevada, about half-way between the city of Reno and the NASA High Range Tracking Station at Ely. Launch time was 10:05:57.0 a.m., PDT. Walker ignited the Reaction Motors XLR99-RM-1 rocket engine. This engine was rated at 57,000 pounds of thrust. Experience had shown that different engines varied from flight to flight and that atmospheric conditions were a factor. Thrust beyond 60,000 pounds was often seen, but this could not be predicted in advance. The flight plan called for the duration of burn to be 84.5 seconds on this flight. The X-15 climbed at a 45° angle.
As Walker was about to shut down the engine according to plan, it ran out of fuel. The total burn time was 85.8 seconds, just slightly longer than planned.
“At burnout, Joe was passing 176,000 feet [53,645 meters] and traveling at 5,600 feet per second[1,707 meters per second]. He then began the long coast to peak altitude. It would take almost 2 minutes to reach peak altitude after burn out. Two minutes does not seem like a lot of time, but try timing it. Just sit back in your easy chair and count off the seconds. It is almost impossible to believe that you can continue to coast up in altitude for that length of time after the engine burns out. It gives you some feel for how much energy is involved at those speeds. For comparison, when you throw a ball up in the air as hard as you can, it only coasts upward a maximum of 4 or 5 seconds. The X-15 coasted up for 120 seconds.
“The airplane would coast up another 178,000 feet [54,254 meters] during that time to peak out at 354,200 feet. . . .”[107,960 meters]
—At The Edge of Space: The X-15 Flight Program, by Milton O. Thompson, Smithsonian Institution Press, Washington, 1992, Chapter 5 at Page 125.
Joe Walker and the X-15 reached the peak of their ballistic trajectory at 354,200 feet (67.083 miles, 107,960 meters). Walker pitched the nose down to be in the proper attitude for atmospheric reentry. The X-15 decelerated as it hit the atmosphere and Walker experienced as much as 7 Gs. The rocketplane’s aerodynamic control surfaces again became operational as it descended through 95,000 feet (28,956 meters) and Walker leveled at 70,000 feet (21,336 meters). He then glided to a landing on Rogers Dry Lake at Edwards Air Force Base, California, after 11 minutes, 8.6 seconds of flight.
Flight 91 was the highest flight achieved by any of the X-15s. It was Joe Walker’s second flight into space. His record would stand for the next 41 years.
8 August 1955: While being carried aloft by a Boeing B-29 Superfortress, the Bell X-1A was being readied for it’s next high-altitude supersonic flight by NACA test pilot Joe Walker. During the countdown, an internal explosion occurred. Walker was not injured and was able to get out. The X-1A was jettisoned. It crashed onto the desert floor and was destroyed.
A number of similar explosions had occurred in the X-1D, X-1-3 and the X-2. Several aircraft had been damaged or destroyed, and Bell Aircraft test pilot Skip Ziegler was killed when an X-2 exploded during a captive flight. A flight engineer aboard the B-29 mothership was also killed. The B-29 was able to land but was so heavily damaged that it never flew again.
Debris from the X-1A crash site was brought back to Edwards AFB for examination. It was discovered that a gasket material used in the rocket engine fuel systems was reacting with the fuel, resulting in the explosions. The problem was corrected and the mysterious explosions stopped.
Test pilot Joe Walker “horsing around” with the Bell X-1A, 1955. (NASA)
24 March 1960: After North American Aviation’s Chief Engineering Test Pilot, Albert Scott Crossfield, had made the first flights in the new X-15 hypersonic research rocketplane (one gliding, eight powered), NASA Chief Test Pilot Joseph Albert Walker made his first familiarization flight.
