The X-15 Test Program

The X-15 Flight Test, January 1960

Forty years ago, in January 1960, the X-15-1, 56-6670 had returned to Edwards Air Force Base after the installation of its pair of Reaction Motors XLR-11 engines. It had been carried on four captive flights before it made a single glide flight on June 8, 1959.

The X-15-2, 56-6671 was at North American Aviation in El Segundo for repairs following the engine explosion and structural failure that it suffered on mission 2-3-9* on November 5, 1959. On its three flights, it had reached a maximum speed of Mach 2.15 and a maximum altitude of 61,781 feet. Scott Crossfield had been the sole X-15 pilot during the contractor demonstration phase.

The NB-52A takes off with the X-15-1 on one of the first three captive carry flights in March and April, 1959. The first flight on March 10 was an intentional captive flight. Subsequent flights on April first and tenth were aborted attempts at a glide flight. On flight 1-A-3, the unexpected high intensity noise produced by the turbulence in the notch in the trailing edge of the NB-52A's wing cracked the skin of the upper rudder of the X-15. The dayglo orange paint adorning the nose of the NB-52A can be seen to extend around the bottom of the fuselage. The badge of the Air Research and Development Command (ARDC) has been applied to the side of the fuselage, below the cockpit. Only the flaps on this side of the NB-52A are painted white. Photo courtesy: AFFTC/HO.

The North American X-15-2 made its first public appearance at the Edwards Air Force Base Open House and Airshow Display, held on May 19, 1959. It was posed with the NB-52A, 52-0003. The X-15-2 was delivered with only one VHF antenna on the lower fuselage. Later in the program a second VHF antenna would be added. Go to more photos of the 1959 Edwards AFB Airshow. Photo by Richard Lockett Sr.

The X-15-1 with Scott Crossfield at the controls was launched from the NB-52A on its first flight on June 8, 1959. Charles Bock and Major Jack Allavie were piloting the NB-52A. This was the only intentional glide flight of the X-15 program. Photo courtesy Air Force Flight Test Center History Office.

The X-15-2 being carried by the NB-52A in October or November 1959. Scott Crossfield is in the cockpit of the X-15. Jack Allavie and either Charles Bock or Fitzhugh Fulton are aboard the NB-52A. The X-15 mission mark visible next to the astrodome represents mission 2-A-4, an aborted launch attempt flown on October 10, 1959. Photo courtesy Air Force Flight Test Center History Office.

On November 5, 1959, the third flight of the X-15-2 was cut short by an explosion in one of the combustion chambers of the lower XLR-11 rocket engine 13.9 seconds after ignition of the first chamber. The X-15 is seen here jettisoning propellants with the town of Rosamond in the background. Scott Crossfield landed the X-15 on Rosamond Dry Lakebed on the west end of the Air Force Base. He was unable to jettison all of the propellants and landed heavy. Photo courtesy Air Force Flight Test Center History Office.

The X-15-2 on Rosamond Dry Lake following mission 2-3-9*. The fuselage failed when the nose gear impacted the ground. The shock absorbing ability of the front landing gear strut was impaired by foaming of the oil in the strut when it was extended. The back of the X-15 broke at a structural join behind the cockpit. It was trucked back to Los Angeles for repairs. Photo E-9543 courtesy NASA Dryden.

B-52B, 52-0008 had joined the X-15 program in November 1959 and carried the designation NB-52B. It carried the X-15-1 for the first time on December 16, 1959. The first attempt to make a powered flight in the X-15-1 was aborted five seconds before launch due to a radio malfunction.

The first powered flight of the X-15-1 was launched on January 23, 1960. Fitzhugh Fulton and Charles Kuyk launched Scott Crossfield from the NB-52B on mission 1-2-7*. Crossfield reached a speed of Mach 2.53 and an altitude of 66,844 feet during 4 minutes and 27 seconds of rocket-powered flight. The only pilots to have flown faster were Pete Everest, Ivan Kinchloe, and Mel Apt in the X-2 in 1956.

The X-15 Flight Test, January - April 1960

The first powered flight of the X-15-1 was conducted on January 23, 1960. Fitzhugh Fulton and Captain Charles Kuyk launched Scott Crossfield from the NB-52B on mission 1-2-7*. Crossfield reached a speed of Mach 2.53 and an altitude of 66,844 feet during 4 minutes and 27 seconds of rocket-powered flight. The only pilots to have flown faster were Pete Everest, Ivan Kinchloe, and Mel Apt in the X-2 in 1956.

The X-15-2 was mated to the NB-52B for a powered flight attempt on February 4, 1960. Numerous systems failures resulted in the scrubbing of the mission.

After a week of making repairs to the X-15-2, it was carried aloft by the NB-52B on February 11. Major Jack Allavie was at the controls of the mother plane, and Fitzhugh Fulton was the co-pilot. The flight plan incorporated a loiter at the launch altitude to simulate the length of time that it would take to carry the X-15 to the launch lakes used for future high performance flights. The X-15 systems cooperated, and mission 2-4-11 was conducted successfully. Crossfield triggered the launch from the X-15 cockpit, a procedure which would become the standard method. The power of the twin XLR-11 rocket engines propelled the X-15 to an altitude of 88,116 feet. Crossfield leveled out and accelerated to mach 2.22 (1,466 miles per hour) on a flight that was considered a complete success.

Six days later, Fulton and Allavie had switched positions in the NB-52B for mission 2-5-12. After launch, one of the thrust chambers of the upper XLR-11 engine of the X-15-2 shut down part way through the burn. The thrust available to the X-15-2 was reduced, but the time of the burn was correspondingly lengthened. The reduced thrust resulted in a modest speed of mach 1.57 (1,036 miles per hour), one of the slowest powered flights of the X-15 program. The X-15-2 climbed only a mile and a half above the launch altitude, reaching 52,640 feet.

High winds at Edwards AFB canceled the next two launch attempts scheduled on February 25 and 26. It was not until March 17 that Major Allavie and Captain Kuyk launched Crossfield in the X-15-2 from the NB-52B on mission 2-6-13. The systems of the X-15-2 performed flawlessly on a flight that reached mach 2.15 (1,419 miles per hour).

The ground crew turned the X-15-2 around overnight for another launch attempt the following day. Major Allavie and Captain Kuyk were assigned to fly the NB-52B. The X-15 systems were prepared for launch when Al White in the chase plane noticed alcohol leaking out of a drain from the X-15 engine bay. A fitting in the fuel plumbing had cracked and alcohol was pooling in the bay. There was great danger of an explosion of the vapors in the engine bay, so the launch was aborted just seconds before the drop.

North American delivered the X-15-1 to NASA in January 1960. For the first time, a pilot other than Scott Crossfield would fly the black missile. Joe Walker, a NASA pilot, had acquired plentiful rocket plane experience in the X-1E. Joe Walker was scheduled to make the first flight of an X-15 by a NASA pilot on March 23, but bad weather forced the flight to be postponed for two days. On March 25, Major Allavie and Fitzhugh Fulton piloted the NB-52B around a racetrack course as Walker familiarized himself with the systems of the rocket plane. After launch, Walker flew the X-15-1 to mach 2 (1320 miles per hour) and an altitude of 48,630, only slightly higher than the launch altitude. Walker's flight marked the beginning of NASA's expansion of the envelope of X-15 operations with the interim XLR-11 engine installation.

Four days after Joe Walker's first flight in the X-15-1, Fulton and Allavie launched Scott Crossfield from the NB-52B in the X-15-2. The flight was for the purpose of establishing the behavior of the black rocket at the high angle of attack that would be encountered on pullouts from high altitude. Crossfield performed a series of dives and pullouts, pulling up to six gees on the pullouts. The X-15-2 was turned around in two days and Crossfield made another flight on March 31.

Air Force Major Robert White was scheduled to become the third pilot to fly the X-15 on April 12, but high winds in the desert caused the flight to be rescheduled for the following day. On April 13, Major Allavie and Captain Kuyk were at the controls of the NB-52A as it flew with an X-15 on the pylon for the first time in five months. On Major White's familiarization flight, he kept the speed of the X-15-1 down to mach 1.9 (1,254 miles per hour) and only climbed three thousand feet above the altitude at which he had been launched.

On April 19, Joe Walker flew the X-15-1 to a new program speed record of mach 2.56 ( 1,689 miles per hour) after launch from the NB-52A on his second X-15 flight.

The X-15 Flight Test, April - May 1960

The reaction control thrusters were first installed in the X-15-2 in April 1960. Up to that time, the highest altitude attained by the X-15 was 88,116 feet on mission 2-4-11, flown on February 11.

Scott Crossfield first tested the reaction control thrusters in flight as the X-15-2 was carried by the NB-52A on May 5. On a typical X-15 flight, the reaction control thrusters would not be used until the X-15 had flown at high speed through the upper atmosphere. Air friction would have heated its airframe. At the launch altitude, the air temperature was well below freezing. The steam from the test of the nose reaction control thrusters froze immediately when it hit the windshield of the X-15. A thick layer of ice formed that obscured Crossfield's view out of the cockpit, forcing him to abort the intended launch.

A launch rehearsal was performed in place of the actual launch. During the procedure, one of the Auxiliary Power Units shut itself down. It was clear that considerable work would be necessary to get all of the X-15-2 systems operating at the same time. After landing at Edwards AFB, it was removed from the pylon of the NB-52A.

By the next morning, May 6, the X-15-1 had taken the place of the X-15-2 on the pylon of the NB-52A for Captain White's second familiarization flight.

Joe Walker was launched in the X-15-1 from the NB-52A on May 12, 1960 for the first mach-3 X-15 flight. (Link: NASA Dryden Biography) For the first time the X-15 was carried away from Edwards AFB for a launch over Silver Lake to allow it to make its speed run in a straight line. Photo courtesy Edwards AFB History Office.

This photo has been used to illustrate the launch of the first Mach-3 X-15 flight on May 12, but in fact it was taken on the first powered flight of the X-15-1 on January 23. The yellow NASA tailband was retouched into the photo. The lettering is not proportioned properly and the font isn't right. After Crossfield made its first powered flight it was transferred to NASA and acquired the yellow tailband. It appears that NASA slipped up getting a photo of the launch of the Mach-3 flight and doctored an existing photo for the press release.

Walker reached mach 3.11 (2111 miles per hour) and an altitude of 77,882 feet. The value for the mach number was measured precisely, but the uncertainty in the conversion to absolute airspeed meant that it wasn't clear whether Walker had broken Mel Apt's speed record of mach 3.196 (2094 miles per hour), set in the X-2 on September 27, 1956. The launch pilots of the NB-52A were Captain Charles Bock and Major Jack Allavie.

The "U. S. AIR FORCE" lettering on the fuselage of the NB-52B was initially 36 inches tall, compared to the 24 inch tall letters on the NB-52A. The scalloped dayglo on the engine nacelles lacks the white cheat line that was seen on the NB-52A in 1959. It can't be seen in this picture, but the flaps on the NB-52B were left unpainted while the starboard flaps on the NB-52A were painted white.

The orange dayglo paint on the tail can be seen to be peeling. By September 1960 it was removed, and a dayglo band was added to the rear fuselage. Later the dayglo on the engine intakes was also removed. Dayglo was used extensively on the aircraft operated from Edwards AFB in that era because orange wreckage is much easier to spot in the desert than aluminum, which tends to mirror the color of its surroundings.

Two days after the airshow, on May 19, the X-15-1 had been transferred to the wing of the NB-52A. Captain Robert White was launched by Major Allavie and Captain Bock on a flight that reached a speed of mach 2.31 (1590 miles per hour) and a new X-15 altitude record of 108,997 feet. It was the second highest flight in history. The altitude had been exceeded previously only by the 125,907 feet achieved by Ivan Kinchloe in the X-2 on September 7, 1956.

On May 26, Scott Crossfield was launched in the X-15-2 from the NB-52B for the first free flight test of the operation of the reaction control thrusters. The flight was only intended to demonstrate that the thrusters functioned properly. The maximum altitude attained on the flight was only 51,282 feet, so the thrusters actually had no effect on the attitude of the X-15. Once again Major Allavie piloted the NB-52B and Captain Bock served as co-pilot.

Joe Walker was carried aloft in the X-15-1 the following day, May 27, on what was to be the first of four attempts to make his fourth flight.

The X-15 Flight Test , June - August 1960

In May and June 1960, NASA was expanding the flight envelope of the X-15-1. Scott Crossfield was concluding the contractor demonstration of the X-15-2 with its pair of XLR-11 engines.

On three occasions, preparations were made to launch Joe Walker in the X-15-1 to make an assault on Mel Apt's speed record, mach 3.196 (2094 miles per hour), set in the X-2 on September 27, 1956. Launch attempts were aborted on May 27 and June 3. The third launch attempt was scheduled for June 8.

In the meantime, the X-15-3 had arrived at Edwards with its XLR-99 rocket engine, and ground tests of the big engine were initiated. For these tests, the X-15-3 was locked in a ground test frame. While the test team sought refuge in a concrete block house, Scott Crossfield would enter the cockpit of the X-15 to operate the rocket engine.

The XLR-99 produced four times the thrust of the XLR-11 twin packs that equipped the first two X-15s when they were delivered. These were the first rocket engines that could be controlled with a throttle, providing any desired level of thrust from 20,000 pounds to 60,000 pounds. The new engines burned a different fuel than the XLR-11 engines had used. The water alcohol fuel mixture of the XLR-11s was similar to martini. The XLR-99 burned extremely noxious anhydrous ammonia. It was much more hazardous to handle, but packed more energy into the same volume of fuel.

The second ground test of the XLR-99 was conducted on June 8. During the test, a regulator valve on the ammonia tank failed in the open position. The ground crew had placed the end of the hose leading from the ammonia tank pressure relief valve in a tank of water to absorb the ammonia fumes. The backpressure in the hose prevented the relief valve from properly venting the pressure in the tank. A faulty pressure gauge in the cockpit failed to reveal the overpressure in the ammonia tank to Crossfield. Eventually, the pressure in the ammonia tank exceeded the strength of the tank, and it failed. Parts of it struck the adjacent hydrogen peroxide tank, which detonated. That caused the ammonia tank contents to ignite and a major explosion shattered the tail of the X-15, scattering bits of Inconel-X in all directions. The remaining fuselage was hurled forward about twenty feet. Protected by the heat resistant cockpit of the X-15, Crossfield was not injured in the explosion and fire.

The June 8 attempt to launch the X-15-1 was immediately cancelled following the explosion of the X-15-3. The entire X-15 program had to be restructured. The X-15-3 would not fly for another 18 months. The X-15-2 took the place of the X-15-3 as the primary vahicle for the first flight tests of the XLR-99. It was shipped to El Segundo to be torn down and have its new engine installed. For the time being, the X-15-1 was the only vehicle available to the program. No X-15 flights were attempted for nearly two months.

On August 4, 1960 Major Jack Allavie and Major Fitzhugh Fulton launched Joe Walker from the NB-52A over Silver Lake on mission 1-9-17. Walker lit all eight chambers of the X-15-1 and pulled up to fly at the angle of attack calculated to produce the highest value of lift over drag. At 74,000 feet altitude, he pushed over to fly a parabolic arc. Flying at zero-g he accelerated to mach 3.31 (2,195 miles per hour). Joe Walker exceeded Mel Apt's speed of 2,094 miles per hour by a hundred miles per hour.

While Walker pushed the top speed of the X-15, Major Bob White was assigned to fly the high altitude flights. His first altitude record attempt was aborted before launch on August 11, 1960. The next day Major Fulton and Major Allavie launched Major White from the NB-52A over Silver Lake. He flew the maximum lift over drag profile to an altitude of 60,000 feet. He leveled off and accelerated to mach 1.9. He then pulled up at 1.5 g's until he had pulled the stick all the way to its limit of travel. The engine burned out at an altitude of 120,000 feet and the X-15 coasted on up to 136,500 feet. This was the first flight to exceed Ivan Kinchloe's record, 125,907 feet attained in the X-2 on September 7, 1956. The top speed attained by the X-15-1 on the flight was mach 2.52 (1,772 miles per hour).

The X-15 Flight Test August - October 1960

Following Robert White's speed record setting flight on August 12, 1960, Joe Walker made his third flight in the X-15-1 on August 19. Walker's first attempt to make the flight was aborted the previous day because of problems with the Auxiliary Power Unit. Jack Allavie and Frank Cole were at the controls of the NB-52A.

The flight was a near repeat of Walker's previous flight. Walker was launched over Silver Lake, just a few miles north of the town of Baker, California, that place with the big thermometer that you pass on the way to Vegas. His top speed was Mach 3.13 (1,986 miles per hour) and his maximum altitude was 75,982 feet.

The X-15-2 was trucked to North American Aviation in El Segundo for the installation of its XLR-99 rocket engine in early September 1960. It returned to Edwards AFB with the new powerplant later that month.

The X-15-1 made two flights in September 1960 and two flights in October 1960. Major Robert White was scheduled for launch on his fifth X-15 flight on September 2, but the flight was cancelled by bad weather before the NB-52B got off the ground. Problems with the Stability Augmentation System resulted in the cancellation of the next attempt scheduled for September 9.

On September 10, Jack Allavie and Charles Kuyk piloted the NB-52B to Silver Lake to launch White on his first Mach-3 flight. The flight profile was very similar to Joe Walker's last two flights. White reached Mach 3.23 (2,182 miles per hour) and 79,864 feet altitude.

The X-15 program entered a phase of pilot check-outs. Four new pilots were introduced to the X-15 in the closing months of 1960. Their familiarization flights were planned to stay in the vicinity of Edwards Air Force Base. The typical maximum speed planned for the familiarization flights was Mach-2 and the maximum altitude was approximately 50,000 feet.

Navy Commander Forrest Petersen became the fourth X-15 pilot in September 1960. Mission 1-A-24, the first attempt to launch Commander Petersen was aborted before launch on September 20.

Jack Allavie and Fitzhugh Fulton launched Commander Petersen from the NB-52B near Palmdale, southwest of Edwards Air Force Base on September 23. Petersen's pointed the X-15-1 toward the town of Boron. At Boron, his flight plan called for him to make a left turn toward the town of Mojave and then another left turn to return to Edwards Air Force Base.

The XLR-11 engines shut down when Petersen had reached only Mach 1.68 (1,108 miles per hour). He was turning left over Boron when he lost power. The flight path for his familiarization flight had been selected to keep him positioned for a return to the lakebed in the event of just such an emergency. He continued the turn to reach the high key position for runway 18 on Roger Dry Lake with Joe Walker in the chase plane tucked in close beside the X-15.

Petersen reached the high key position at 25,000 feet altitude, which was lower than the desired altitude. Walker urged him to tighten up his turn as they made a left 360-degree turn. Petersen actually arrived on final approach a little high on energy. He popped the speed brakes to set the X-15 down at the correct position on the runway. The Dryden Diary entry for this flight says, "Exciting but good".

Commander Petersen's next flight was scheduled for October 11, but a loss of Nitrogen source pressure caused the launch to be scrubbed.

The first flight of the X-15-2 with the XLR-99 engine was scheduled for October 12, 1960, but the first big engine mission was postponed by "structural difficulty." On October 13, Scott Crossfield suited up and climbed into the cockpit of the X-15-2 under the wing of the NB-52A, but the right hand auxiliary power unit developed a leak and the mission was scrubbed.

Fitzhugh Fulton and Charles Kuyk launched Commander Petersen on his second X-15 flight on October 20. The flight plan for this flight was a repeat of the plan for his first flight. After turning west toward Mojave, he accelerated the X-15-1 to Mach 1.94 (1,280 miles per hour), climbing to a maximum altitude of 53,800 feet.

Eight days later, on October 28, Fitzhugh Fulton and Frank Cole launched Jack McKay on his first X-15 flight from the NB-52B. He made the usual circuit from Palmdale to Boron, Mojave, and back to Edwards Air Force Base. He reached Mach 2.02 (1,333 miles per hour) and 50,700 feet. The Dryden Diary notation for this flight is "Pretty - Pretty".

The X-15 Flight Test. November 1960

Attempt to launch two X-15s in a single day, Captain Robert Rushworth's First X-15 Flight, November 4

Another attempt to launch the first flight of the X-15-2 with the XLR-99 engine was scheduled for November 2, 1960, but it was cancelled by weather.

On November 3, 1960, the X-15-1 was mated to the NB-52B and the X-15-2 was mated to the NB-52A in an attempt to launch both of them on the same day. Bad weather set in and cancelled the attempt for that day.

On November 4, Scott Crossfield entered the cockpit of the X-15-2 to make another attempt at the first flight of the XLR-99 rocket engine. Captain Bob Rushworth got into the X-15-1 to make his first X-15 familiarization flight. After the NB-52A had taken off, the X-15-2 developed a hydraulic leak and Crossfield's flight was aborted. Major Fulton and Major Cole successfully launched Captain Rushworth from the NB-52B on mission 1-16-29. On his first X-15 flight, Rushworth reached mach 1.95 (1,287 miles per hour) and an altitude of 48,900 feet. Photo E-6186 Courtesy NASA Dryden.

The first flight of the big engine was postponed again on November 5 because of weather and again on November 7 because the lakebed was wet from the recent rains.

First flight of the XLR-99 engine, November 15

Major Allavie and Captain Kuyk finally launched Crossfield in the X-15-2 from the NB-52A over Rosamond Dry Lake on November 15, 1960. Mission 2-10-21, the first XLR-99 powered flight, went faster and higher than planned. At 50% thrust, the big engine pushed the X-15-2 to Mach 2.97 (1,960 miles per hour) rather than the intended Mach 2.7 and 81,200 feet high, over 20,000 feet higher than the planned 60,000 feet.

Although Crossfield was restricted to speeds below Mach 3 during the contractor demonstration flights, a measurement error of only one part in one thousand would put his speed on this flight right at Mach 3. It cannot be stated with certainty that he did not exceed Mach 3 on that flight. Without doubt, he saw the Mach meter needle pointing directly at the three during the flight.

Captain Rushworth was launched on his second flight in the X-15-1 from the NB-52A by Major Fitzhugh Fulton and Major Jack Allavie over the town of Palmdale on November 17. The lower XLR-11 engine shut down prematurely, but Rushworth was able to restart the engine and complete the flight as programmed. He reached a top speed of Mach 1.9 (1,254 miles per hour) and a maximum altitude of 54,750 feet.

Crossfield made the second flight of the X-15-2 with the XLR-99 engine on November 22. He was launched from the NB-52A by Fulton and Allavie over Rosamond Dry Lake. The prime objective of the flight was to test the operation of the big engine. Crossfield throttled it down to 75% power and then down to 50% power. He shut down the engine and restarted it. Again he exceeded his programmed speed by two tenths of a Mach number.

Neil Armstrong's First X-15 Flight, November 30

Neil Armstrong made his first flight in the X-15-1 on November 30. Frank Cole piloted the NB-52B and Major Fulton occupied the right seat as they dropped Armstrong over Palmdale. One of the rocket chambers of the XLR-11 engines shut down. He completed the flight on seven cylinders. On his introductory flight his top speed was just Mach 1.75 (1,155 miles per hour) and the highest altitude was only 48,840 feet.

The X-15 Flight Test November 1960 - January 1961

Crossfield concludes the contractor demonstration flights. Armstrong and McKay evaluate the Q-ball nose.

Scott Crossfield concluded the North American contractor demonstration of the X-15-2 with the XLR-99 engine on December 6, 1960. He was launched from the NB-52A by Major Jack Allavie and Major Frank Cole over Rosamond Dry Lake on the southwest side of Edwards Air Force Base.

The mission plan called for the XLR-99 engine to burn for 121 seconds, pushing the X-15-2 to Mach 2.30. The rocket engine burned for 128.9 seconds, and Crossfield exceeded the planned speed by over a half of a Mach number, reaching Mach 2.85 (1,881 miles per hour).

Mission 2-12-23* was Scott Crossfield's last rocket powered flight. He had made his first rocket powered flight in the Bell X-1 nearly ten years earlier, on April 20, 1951.

Following Neil Armstrong's first flight in the X-15-1 on November 30, the "barber pole" air data boom on its nose was removed and replaced with the Q-ball (pronounced cue-ball). Q stands for dynamic pressure. The Q-ball nose was machined out of solid Inconel-X. It detected the direction from which the airstream was striking the nose of the X-15, and its construction would allow it to withstand the high temperatures that would be generated at speeds above Mach-6.

Mission 1-19-32, the first flight of the X-15-1 equipped with the Q-ball nose, was scheduled for December 8 with Neil Armstrong at the controls. The flight was postponed by weather until the following day. Armstrong was launched from the NB-52B by Major Allavie and Major Cole over Palmdale. The primary objective of the flight was to evaluate the function of the new air data sensor, so Armstrong's top speed was only Mach 1.80 (1,188 miles per hour) and his maximum altitude was only 50,095 feet.

Major Robert White was scheduled for a flight in the X-15-1 on December 15, but a hydraulic leak postponed his flight. The X-15-1 was taken out of service for ten days in December while wiring associated with its inertial navigation system was installed.

John McKay's second X-15 flight was initially scheduled for January 11, 1961, but it was postponed until January 31. Then it was postponed for another day by a hydraulic fluid heater failure. Major Fitzhugh Fulton and Major Ken Lewis launched McKay from the NB-52B over Palmdale on February 1. He reached a top speed of Mach 1.88 (1,212 miles per hour) and a maximum altitude of 49,780 feet.

The NB-52A was flown to the Boeing plant in Wichita, Kansas in January 1961 for periodic maintenance. Only the NB-52B was available to launch the X-15s until the NB-52A's return in April.

The X-15 Flight Test, February - March 1961

The NB-52A had been flown to the Boeing plant in Wichita on January 14 for maintenance. It was out of service during February and March 1961.

Major Bob White flew the last XLR-11 powered X-15 flight on February 7, 1961. Major Fitzhugh Fulton and Robert Mosley launched the X-15-1 from the NB-52B over Silver Lake, near Baker in eastern California. Stan Butchart manned the launch panel operator's station. Through a combination of optimal conditions, the XLR-11 engines burned twelve seconds longer than they had on any prior flight. White flew the X-15-1 to mach 3.49 (2,275 miles per hour), the highest speed that it attained with the XLR-11 engines. Following mission 1-20-35, the X-15-1 was shipped to North American in El Segundo to have its XLR-11 engines replaced with an XLR-99.

NASA took delivery of the X-15-2 from North American. It had been refitted with a round q-ball air data sensor machined from solid Inconel-X. Neil Armstrong had piloted the first flight of the ball nose on the nineteenth flight of the X-15-1 on December 9, 1960.

This flight marked the beginning of the envelope expansion phase of X-15 operations. Joe Walker and Bob White would take turns pushing the X-15 to higher speeds and altitudes than it had reached before.

The flight was postponed by difficulties with the stable table system. The stable table used data from the instruments of the B-52 to establish a fixed frame of reference for the inertial navigation system of the X-15. It was a challenging task to get all of the instrumentation working together to fix the frame of reference. The process was referred to as erecting the stable table. Once the stable table was erect, it fed position and velocity data into the inertial navigation system of the X-15 before launch.

On this mission, the operation of the stable table was interrupted by the APN-81 doppler radar system shortly before launch.

The APN-81 Doppler radar system measured the ground speed of the B-52 along its path and the speed of its drift across its heading as input to the stable table system. When the B-52 banked or pitched beyond certain limits the doppler radar system stopped measuring the ground speed and drift. After the B-52 stopped turning the doppler radar took some time to resume proper function. This was normal operation for doppler radar units on standard B-52 bombers.

The problem was that a typical X-15 launch mission began with a flight from Edwards AFB to the launch position followed by a 180 degree turn to the launch heading. The 180-degree turn took four minutes to complete. The doppler radar unit shut down during the turn, depriving the stable table system of necessary velocity information. Then it took too long to return to normal operation after the B-52 assumed the launch heading. Failure to maintain erection of the stable table in this critical period resulted in the abandonment of the attempt to launch the X-15.

The X-15-2 was removed from the wing of the NB-52B and replaced by an instrumented pod. The pod was constructed from a leftover North American F-107 external fuel tank equipped with instrumentation to simulate the electronic functions of the X-15. It also contained accelerometers to measure the forces imposed on the X-15 while it was being carried by the NB-52. Captain Kuyk and Major Lewis piloted a flight of the NB-52B with the instrumented pod on March 1.

The first NASA flight of the X-15-2 with the ball nose and XLR-99 engine was successfully launched over Silver Lake on March 7, 1961. Captain Kuyk and Major Frank Cole piloted the NB-52B. Jack Russell manned the launch panel operator's station. Major White ploted the X-15-2 to a new maximum speed of mach 4.43 (2,905 miles per hour) and an altitude of 77,450 feet. It was the first flight of any aircraft faster than mach 4.

Captain Vincent Baker and Captain Kuyk flew to Wichita to test fly the NB-52A on March 20 in preparation for its return to Edwards Air Force Base.

The NB-52B carried the X-15-1 aloft again on March 21 to launch Joe Walker's first X-15 flight with the big engine. Major Fulton and Captain Jack allavie were at the controls of the NB-52B. Trouble with the electrical systems of the NB-52B caused the launch attempt to be abandoned.

Captain Kuyk flew the other X-15 mothership back from Wichita to Edwards AFB on March 23. Lt. Colonel Richard Morgan acted as co-pilot on the cross-country flight. The NB-52A had received a complete facelift. All of the exposed metal surfaces were painted silver. The X-15 mission marks on the right side of the fuselage were replaced. The new mission marks were more closely spaced to make room for more mission marks to be added in the future.

Walker's first envelope expansion flight in the X-15 with the big engine was rescheduled for March 29, but high winds and trouble with the landing gear of the NB-52B caused the mission to be postponed for another day.

Major Fulton and Captain Kuyk launched Walker from the NB-52B on March 30. The engine failed to ignite on the first attempt, but it started after Walker reset the igniter. The X-15-2 reached an altitude of 169,000 feet, which was nearly 30,000 feet higher than any previous flight had gone.

Walker made the following comments about his observations of the earth from the extreme altitude:

This was to be the last altitude record set by the X-15. Yuri Gagarin was launched on the first Vostok mission on April 12, eclipsing all previous absolute height and speed records.

The X-15 Flight Test, April - June 1961

Captain Charles Kuyk and Lt. Colonel Richard Morgan flew the NB-52A, 52-0003 back to Edwards AFB from the Boeing plant in Wichita on March 23, 1961.

The X-15-1 was at North American in El Segundo for the installation of its XLR-99 engine.

Yuri Gagarin was launched on the first Vostok mission on April 12, eclipsing all previous absolute height and speed records. Alan Shepard was launched in Freedom 7 on the first suborbital Project Mercury flight in May. Subsequent X-15 records would have to be restricted to comparisons with other "winged vehicles".

The X-15-2 was programmed for a series of flights to expand its flight envelope. The flight envelope of an airplane is shown by a graph of its maximum and minimum speeds depending on altitude. Its next three flights were intended to explore progressively higher speeds.

Captain Jack Allavie and Captain Robert Mosley piloted the NB-52A for the launch of mission 2-15-29 on April 21. They carried the X-15 to Hidden Hills Lake in Nevada for the launch. Major Bob White set a new speed record of Mach 4.62 (3,074 miles per hour) in the X-15-2.

A production unit from Frank Sinatra's Essex Productions was at Edwards AFB in April and May to film scenes for the movie X-15 . The film featured David McLean and Charles Bronson as X-15 pilots. Mary Tyler Moore played the wife of an X-15 pilot. Dick Gregory portrayed an Air Force spokesman. The movie was directed by Richard Donner, who later directed Superman and Lethal Weapon. The studio manufactured a full size mock-up of the X-15 for filming. The film has never been released commercially on video. It is currently in the library of Turner Entertainment.

Joe Walker's next flight in the X-15-2 was scheduled for May 18, but it postponed for a day due to problems with the stable platform. Captain Allavie and Captain Kuyk flew the NB-52A with the X-15-2 and Walker aboard for a launch attempt on May 19, but it was aborted due to problems with radar and the auxiliary power units of the X-15.

The Air Force Flight Test Center hosted an open house on May 21. Captain Allavie and Captain Emil Sturmthal participated in the fly-by passes in the NB-52B. The X-15-2 was parked in front of the NB-52A on static display.

As the top speed of the X-15 increased, the length of its flight path also increased. It was necessary to launch the X-15 farther from Edwards Air Force Base. Joe Walker would be launched over Mud Lake, Nevada for the first time on the sixteenth flight of the X-15-2.

Captain Allavie and Major Fizthugh Fulton launched Joe Walker on mission 2-16-31 on May 25. Despite having to restart the XLR-99 engine after launch, he set another new speed record of Mach 4.95 (3,307 miles per hour).

Cloudy weather postponed Major Bob White's next launch attempt on June 20. Three days later, Captain Allavie and Major Fulton launched Major White on the seventeenth flight of the X-15-2. He made the first flight faster than Mach 5, setting yet another new speed record of Mach 5.27 (3,603 miles per hour) on mission 2-17-33.

The X-15-2 had set one new altitude record and four new speed records (for winged vehicles) on its five most recent flights. Major White had made the first Mach 4 flight and the first Mach 5 flight in the last three months.

The X-15 Flight Test, July - August 1961

Click on Picture to enlarge

Ground crew tends to X-15-1 on Rogers Dry Lake. Rescue helicopter HH-21B, 53-4389 sits on the lakebed in the background.

Because of the relatively low speed of the flight, the X-15-1 was launched over Silver Lake, just north of the town of Baker, California. Petersen actually reached Mach 4.11 on this flight

The NB-52B, 52-0008 had not launched an X-15 since March 30, 1961. It was engaged in a series of "functional" flights and tests with a pod that simulated the systems of the X-15. The pod was a modified fuel tank left over from the North American F-107 program. It was also equipped with accelerometers to determine the loads imposed on the X-15 while it was hanging from the pylon on the wing of the Stratofortress. The NB-52B flew seven pod flights between March and December.

The XLR-99 engine had been installed in the X-15-1 following its last flight with the XLR-11 engines on February 7. Commander Forrest Petersen was scheduled to make the first flight of the X-15-1 with the XLR-99 engine on July 14. It would be his third X-15 flight and the twenty-second flight of the X-15-1.

Contamination of the anhydrous ammonia fuel resulted in the postponement of the first attempt to launch the X-15 with the XLR-99 engine. The launch was rescheduled for August 1, but it was canceled. Bad weather forced a postponement of the next launch attempt on August 2. Bad weather and a faulty propellant tank regulator aborted the launch attempt on August 3, and continued bad weather prevented a launch on August 4.

The flight plan called for Petersen to keep the XLR-99 engine at 50% throttle to reach a maximum velocity of Mach 3.7, the slowest velocity for an X-15 flight since the last XLR-11 flight in February.

The X-15 Test Flight, September - November 1961

Captain Jack Allavie and RAF Squadron Leader Harry Archer had launched Commander Forrest Petersen in X-15-1 from the NB-52A on August 10. A month passed before the next X-15 flight, but then the pace of the program picked up considerably.

The choice of launch lake was determined by the distance that the X-15 would fly on a planned flight profile. Faster flights required the X-15 to be launched farther from Edwards Air Force Base.

On September 12, 1961 the recently promoted Major Jack Allavie and RAF Squadron Leader Harry Archer piloted the NB-52B with the X-15-2 mounted on the wing. Jack Russell manned the launch panel operator's station. Joe Walker was the X-15 pilot for the eighteenth flight of the X-15-2.

Walker triggered the X-15 launch mechanism over Mud Lake, Nevada. The X-15-2 dropped away from the NB-52B and accelerated to 3,618 miles per hour at engine burnout. It was the fastest velocity achieved by the X-15 so far, but due to atmospheric conditions, the maximum Mach number attained was 5.21, which was slightly less than that achieved by Major White on mission 2-17-33 on June 23. The maximum altitude of mission 2-18-34 was 114,300 feet.

On September 28, Major Allavie and RAF Squadron Leader Archer flew the NB-52B with the X-15-2 to Hidden Hills Lake. They launched Commander Forrest Petersen on mission 2-19-35. Petersen's highest speed was 3,600 miles per hour, slightly less than the speed that Joe Walker had achieved on the previous flight. Due to atmospheric conditions, Petersen reached a new record Mach number of 5.3. at a slightly lower maximum altitude of 101,800 feet.

The stability of the X-15 was marginal during the descent from high altitude. The problem became more acute as the X-15 achieved progressively higher altitudes. Engineers determined that the stability of the X-15 would be improved during that phase of the flight if the lower portion of the ventral fin were removed.

The next flight of the X-15-1 was flown without the lower portion of the ventral fin to investigate its stability characteristics in that configuration. In a departure from the envelope expansion program, the mission profile called for a lower top speed and altitude than previous flights, so the X-15 was to be launched over Silver Lake.

Major White occupied the co-pilot seat of the NB-52A on September 29 as Major Allavie piloted the first attempt to launch Major Rushworth on the twenty-third flight of the X-15-1. The launch attempt was aborted due to trouble with the X-15's hydraulic system.

Mission 1-23-39 was successfully launched on October 4. Major Allavie and Squadron Leader Archer piloted the NB-52A. Major Rushworth set the X-15's throttle to 50% and let it burn for 120 seconds. The X-15-1 reached a maximum speed of Mach 4.3 (2,830 miles per hour) and the relatively low altitude of 78,000 feet on the first X-15 flight flown without the lower ventral fin.

The twentieth flight of the X-15-2 was aimed at setting a new altitude record. Joe Walker had set the existing record of 169,600 feet during mission 2-14-28 on March 30, 1961. Major White's flight profile called for a maximum speed of Mach 5 and an altitude of 200,000 feet.

Major Jack Allavie and Major Fitzhugh Fulton flew the NB-52A to the launch point over Mud Lake on October 11. After launch, Major White pulled up into a climb of 32 degrees and let the engine burn for 79 seconds. The X-15-2 coasted in a ballistic arc to a new altitude record for the X-15 of 217,000 feet over the north end of Death Valley. It accelerated to a maximum Mach number of 5.21 as it descended over Racetrack Playa.

The original soda-lime glass panels of the X-15 cockpit canopy had been replaced with alumino-slicate glass earlier in the program when it was discovered that temperatures on the canopy had been underestimated. It had been anticipated that the windshield gass would be heated by air friction to a temperature of 740 degrees Fahrenheit. On early flights the temperature of the windshield was found to be closer to 1,000 degrees F. The difference in the temperature between the outside surface of the glass and the surface inside the cockpit was 750 degrees F.

After mission 2-20-36 it was determined that the broken windshield pane was a soda-lime glass pane that had inadvertently been re-installed in the canopy.

Joe Walker's objective during the twenty-fourth flight of the X-15-2 was to continue to expand its speed envelope. His flight plan called for him to reach a maximum Mach number of 5.70.

Squadron Leader Archer and Major Allavie launched Walker from the NB-52A over Mud Lake on October 17. Stan Butchart manned the launch panel operator's station. Walker set the X-15's throttle to 100% and pulled up into a climb of slightly more than the 30 degrees called for in the flight plan. Then he pushed the nose down so that he was flying at "zero-G". In other words, his wings were producing no lift, so the X-15 followed a ballistic trajectory. In the cockpit of the X-15, Walker felt nearly three Gs pushing him back into his seat from the acceleration imposed by the XLR-99 engine. The X-15-1 was going Mach 5.74 (3,900 miles per hour) when the engine burned out after 80 seconds. It reached a peak altitude of 108,600 feet during mission 1-24-40.

Major White was scheduled to make the twenty-fifth flight in X-15-1 on October 27. Major Allavie and RAF Squadron Leader Archer took the X-15-1 aloft on the wing of the NB-52A, but the launch attempt was cancelled because of bad weather. A second launch attempt was scheduled for October 31. That launch attempt was postponed to November 1 because the weather was bad.

A Lockheed C-130 was needed for the long range X-15 flights. It carried men and equipment to tend to the X-15 and its pilot in the event of an emergency landing on one of the dry lakebeds under the flight path. Emergency medical technicians would parachute to the locatioin where the pilot came down. On occasion, the C-130 was required for work on other programs, resulting in a postponement of a launch attempt. The November 1 launch attempt was postponed because the C-130 was not available and the weather was still bad.

Major Allavie and Squadron Leader Archer took Major White aloft in the X-15-1 again on November 2, but the X-15 lost cabin pressurization, causing another postponement.

November 3 was a sunny day, and another attempt was made to launch White in the X-15-1. The launch was scrubbed due to a failure of the igniter idle pressure.

Oddly, according to the Dryden Diary, a proposed speed envelope expansion attempt was scheduled for Major White in the X-15-2 for the same day, but it was "cancelled due to weather".

The X-15-1 was removed from the pylon of the NB-52A and efforts were switched to preparing the X-15-2 for an attempt to reach Mach 6. The X-15-1 would not be flown again until the following April.

The X-15-2 was mounted on the wing of the NB-52B for the next launch attempt. A failure to achieve igniter idle pressure resulted in the launch attempt being scrubbed before the NB-52B took off on November 4. An attempt to launch White in the X-15-2 the following day was aborted for the same reason. Another launch attempt was scheduled for November 8, but the X-15-2 suffered auxiliary power unit trouble.

In the meantime, the X-15-1 conducted a successful ground engine run on November 7.

Major John Allavie and Squadron Leader Archer took the X-15-2 aloft under the wing of the NB-52B on November 9.

A heat resistant paint was tested on the X-15 canopy on the first Mach-6 flight. The left side of the cockpit canopy was painted white. The right side of the canopy remained black.

At full throttle, Major White pulled up to a climb angle of twenty-five degrees and then pushed over for a zero-G acceleration run over the north end of Death Valley. The X-15-2 was going Mach 6.04 (4,093 miles per hour) when the engine burned out 83 seconds after launch. The maximum altitude on mission 2-21-37 was 101,600 feet.

The alumino-silicate glass fractured into much smaller pieces than the soda-lime glass window that had failed on mission 2-20-36. The view through that side of the canopy was comletely obliterated. If the window on the other side of the cockpit had broken, White would have had no visibility out of the cockpit. His only option would have been to fly on instruments until the approach to landing. Then he would have had to jettison the cockpit canopy and try to land the X-15 with an open cockpit.

Air friction heating of the Inconel-X window frame had caused the frame to buckle. The deformation of the frame caused it to pinch the glass panes. When the frame pressed in on the glass, conduction of heat from the frame caused that part of the window to expand more than the surrounding glass . Thermal stresses shattered the outer pane of the cockpit window. The glass stayed in place, but the view through the window on that side of the cockpit was obliterated. The problem of cockpit windows breaking in flight was solved by replacing the 0.05 inch thick Inconel X window retaining frame with a 0.10 inch thick titanium frame to eliminate the buckling of the frame.

This flight concluded the speed envelope expansion for the X-15 in its original configuration. It had achieved the Mach number set as the goal for the program nearly a decade earlier. The speed achieved on this flight would not be exceeded by an X-15 again for over two years.

In the course of the last five X-15 flights, the maximum Mach number had been increased three times and a new altitude record had been established. The only flight that did not set a record was flown to evaluate the stability of the X-15 with the lower ventral fin removed.

The movie X-15 premiered in Hollywood over the Veteran's Day weekend. Staff from the Flight Research Center attended a screening on Friday November 10.

The X-15-2 would not fly again for five months. Attention was centered on the preparation of the X-15-3 for its long delayed first flight in December.

The X-15 Flight Test, November 1961 - March 1962

Following the achievement of the X-15's design maximum mach number on November 9, 1961, the emphasis of the program shifted from envelope expansion to flight research at high mach numbers and altitudes.

Repairs to the X-15-3 were completed by North American at El Segundo, and it returned to Edwards Air Force Base for its first flight a year and a half after it exploded in the rocket engine test stand. The X-15-3 was equipped with a unique Minneapolis-Honeywell MH-96 adaptive gain flight control system for high altitude flights out of the atmosphere. The MH-96 automatically blended the aerodynamic and reaction controls. The system compensated for the reduction in effectiveness of the aerodynamic controls as altitude increased.

In order to perform airborne system tests of the NB-52 without requiring an X-15 to be mated to the Stratofortress, technicians at the Air Force Flight Test Center created an instrumented pod that simulated the systems of the X-15. It was constructed from an external fuel tank left over from the North American F-107 program and fit the connections of the X-15 pylon. It also contained accelerometers to measure the accelerations imposed on the X-15 while it was being carried by the NB-52s. Captain Charles Kuyk and Stanley Butchart conducted a test flight of the NB-52B with the instrumented pod on December 13.

The first flight of the X-15-3 was scheduled for 9:00 A.M. on December 19. Neil Armstrong was to make his third X-15 flight over a year after his last previous flight. The primary purposes of the flight were to evaluate the new X-15's performance at partial power and its unique Minneapolis-Honeywell MH-96 flight control system in the adaptive damper mode. The flight plan called for Armstrong to climb at 50% thrust to level flight at an altitude of 75,000 feet, then perform control input pulses to evaluate the adaptive damper and descend to a landing on Rogers Dry Lake. The adaptive reaction control thrusters were not engaged, since they would not be effective at that altitude.

Major Jack Allavie and Major Russell Bement piloted the NB-52A. Stan Butchart manned the launch panel operator's station. The first launch attempt was aborted due to problems with the inertial navigation system.

The flight was rescheduled for the following morning. The X-15-3 was launched from the NB-52A over Silver Lake, 100 nautical miles from the landing site at Rogers Dry Lake. All three axes of the inertial navigation system tripped out as Armstrong launched the X-15. It rolled sharply to the right, wobbling about both the pitch and yaw axes. Without bothering to comment, Armstrong stabilized the flight of the X-15-3 and throttled its XLR-99 engine to 50% thrust. Although hampered by a poorly functioning radio, he evaluated the adaptive gain flight control system by making a series of pre-planned control input pulses. According to the flight plan, Armstrong shut down the rocket engine after a 106.3-second burn, before all of the propellants were expended, reaching a mach number of only 3.76 (2,502 miles per hour) and a maximum altitude of just 81,000 feet.

Armstrong noted that the adaptive gain flight control system changed the behavior of the X-15 during landing. In the other two X-15s, the pilot would pull the stick back with constantly increasing force to maintain the desired angle of attack as the rocket plane slowed down. In the X-15-3, the pilot held the control stick centered to maintain the desired angle of attack. The X-15-3 did not display the changes in trim associated with the extension of the flap and landing gear that the X-15 pilots had become accustomed to.

Major Allavie and Major Frank Cole conducted another test flight of the NB-52B with the instrumented pod on December 22.

Major Cole and Captain Emil Sturmthal flew the NB-52B to Boeing's factory at Wichita. for maintenance on January 2, 1962.

Navy Commander Forrest Petersen's fourth and last X-15 flight was scheduled for January 10, 1962. His flight plan called for him to use 100% throttle to climb to 92,000 feet altitude, then throttle back to 50% thrust and climb while accelerating to mach 5.7 at an altitude of 110,000 feet, at which time the X-15-1's fuel would be expended. After burn out he was to continue in a ballistic trajectory to a maximum altitude of 117,000 feet.

The launch was delayed for two hours due to difficulties achieving an erection of the stable table. Major Jack Allavie and Lieutenant Colonel Don Anderson launched Commaner Petersen on mission 1-25-44 over Mud Lake about 200 miles from Edwards Air Force Base.

The XLR-99 engine of the X-15-1 shut down immediately after starting. Commander Petersen cycled through the start sequence a second time. The process of restarting the engine took 10 to 15 seconds, all the while the X-15 was descending at over 10,000 feet per minute. The engine started momentarily a second time, but shut down again. Petersen lowered the nose of the X-15 and started jettisoning his propellants. He glided in a left hand, 180-degree turn to Mud Lake, where he made the first landing of the X-15 away from Edwards Air Force Base less than four minutes after launch. A general aviation pilot in a lightplane saw the emergency landing of the X-15 and proceeded to circle the dry lake to get a better view.

Commander Peterson left the X-15 program after this flight. There were no further X-15 flights made by Navy pilots.

The second flight of the X-15-3 was scheduled for January 16, 1962. The primary purpose of the flight was another evaluation of the MH-96 flight control systrem by Neil Armstrong. The flight plan called for launch over Mud Lake followed by a climb at 75% thrust to level flight at an altitude of 100,000 feet. Armstrong was to accelerate to mach 5 before shutting down the engine after a 100-second burn. He was to make a series of yaw, pitch, and roll inputs to evaluate the response of the adaptive gain flight control system.

Edwards Air Force Base was overcast on January 16, so the second flight of the X-15-3 was postponed until the following day. It was still overcast the next morning, but the clouds cleared after delaying the launch by an hour. Once again, Major Jack Allavie and Major Russell Bement piloted the NB-52A while Stan Butchart manned the launch panel operator's station. This time the MH-96 control system did not disengage during the launch of the X-15. Armstrong's trajectory was higher and faster than planned. He shut down the engine after 97 seconds. The X-15-3 was going mach 5.51 (3,765 miles per hour) at an altitude of 117,000 feet at engine shut down. Since his speed was 1/2-mach higher than planned, Armstrong kept the nose up to avoid overstressing the airframe. That resulted in a maximum altitude 33,000 feet higher than the 100,000 feet specified in the flight plan.

The winter rains made Rogers Lake and the emergency landing lakes too muddy to support X-15 landings until later in March. The NB-52A made three more flights in January 1962. It was flown twice in February and three times in March before the next X-15 flight. Two new pilots were introduced to the NB-52A during this period. A pilot named Phillips rode as co-pilot with Major Fitzhugh Fulton on January 25. Major Jack Allavie familiarized Earl Harper with the NB-52A on February 2.

The NB-52B returned from Wichita with Captain Scharon and Major Charles Kuyk at the controls on March 21. It had been painted silver overall. The last four digits of the Air Force serial number, 0008, had been added on each side of the nose below the nose radome. The original eagle nose art was painted over. A slightly different eagle on a blue circle was painted lower on the nose. The blue circle was no longer truncated on the top at the edge of the area painted Day-Glo orange.

The X-15-3 was scheduled to make its next flight in late March. The primary purpose of the flight was to evaluate the operation of the MH-96 adaptive gain control system above nearly all of the atmosphere, particularly the MH-96 system's control of the reaction control thrusters. After launching over Hidden Hills Dry Lake, the flight plan called for Neil Armstrong to set the throttle at 75% thrust and climb at an angle of 35 degrees. He was to shut down the engine after 70 seconds at an altitude of 95,000 feet, then continue in a ballistic trajectory to an altitude of 170,000 feet.

The flight had been postponed once already when the NB-52A hauled the X-15-3 aloft on March 29. Major Fitzhugh Fulton and Captain John Campbell were at the controls of the NB-52A. Stan Butchart manned the launch panel operator's station. The stable table inertial system froze up, literally. The heat exchanger iced up resulting in an abort of the launch attempt until the next day.

On March 30, the launch team was asked to postpone the launch until 10:30 A.M., while the Air Force conducted an ejection seat test using a tranquilized bear. The ejection test itself was postponed until a later date. A hydraulic leak delayed the launch time until 1:00 P.M. The same flight crew took the X-15-3 aloft for a second launch attempt that afternoon, but a malfunction of the XLR-99 engine igniter idle resulted in another launch abort just moments before the drop.

The whole operation was repeated again on March 31, but the launch was scrubbed when the MH-96 flight control system failed analyzer test #24. In the face of repeated launch aborts, the next attempt was postponed until April 5 to allow time to troubleshoot the systems of the X-15-3 and NB-52A.

The X-15 Flight Test, April 1962

No X-15 missions were launched between January 17 and the beginning of April 1962. The pace of the program picked up significantly in April. Sixteen X-15 missions were launched in the next four months. The X-15-3 was expanding its altitude envelope. The X-15-2 was slated to evaluate airframe heating, and the X-15-1 was expected to set another new altitude record.

After a series of aborted launch attempts, the X-15-3 was launched on its third flight on April 5. Major Fitzhugh Fulton and Captain John Campbell were at the controls of the NB-52A. Stan Butchart manned the launch panel operator's station.

The MH-96 flight control system passed the pre-flight analyzer tests with no problems. When Armstrong triggered the ignition of the XLR-99 engine over Hidden Hills Dry Lake, the igniter pressure fell to zero and the engine remained mute. He ran through the engine restart sequence, which seemed to him to take a long time. The X-15-3 had fallen 10,000 feet before he got it going uphill. As a result of the late engine start, Armstrong let the rocket burn for 9.2 seconds longer than the flight plan called for. The X-15-3 reached a peak altitude 10,000 feet higher than the planned 170,000 feet. Armstrong's evaluation of the MH-96 was largely positive, but his comments indicated that he felt that the operation of the reaction control thrusters needed some fine tuning.

Joe Walker was scheduled to make the 26th flight of the X-15-1 on April 17. The primary purpose of the mission was to evaluate the Alternate Stability Augmentation System (ASAS) of the X-15-1 at high angle of attack. The ASAS acted as the primary backup to the Stability Augmentation System (SAS). Walker would be launched over Mud Lake and use full throttle to climb at 30 degrees to an altitude of 58,000 feet. At that altitude he was to push over until the wings of the X-15 were generating no lift, resulting in a period of "zero-g" flight and minimizing drag. Although Walker would experience no upward or downward acceleration, he would be pressed into the pilot's seat with a force approaching 3 times the force of gravity from the thrust of the rocket engine. At 75,000 feet, he was to pull up until the X-15 pulled 1.5 gs. The propellants would be expended after about 83 seconds, when the X-15 was at an altitude of 100,000 feet.

After burn out, Walker was to pull the nose of the X-15-1 up to an angle of attack of 20 degrees and shut down the channels of the SAS, one at a time, to evaluate the response of the ASAS. The X-15-1 would reach its peak altitude of 153,000 feet after 76 seconds of coasting. Walker would pull the nose up to 20 degrees angle of attack twice again during the descent, landing on Rogers Dry Lake after a flight of about 11 minutes.

The reaction control system of the X-15-1 suffered from a hydrogen peroxide leak on the morning of April 17, so the flight was rescheduled for the next morning. Major Jack Allavie and RAF Squadron Leader Harry Archer took the NB-52A aloft with Walker in the cockpit of the X-15-1 under its right wing on April 18, but cloudy skies over Mud Lake prevented the launch that morning.

Jack Russel manned the launch panel operator's station as the twenty-sixth flight of the X-15-1 was launched over Mud Lake on the morning of April 19. The XLR-99 rocket engine fired up on the first try, and the X-15 was already popping and banging like a hot wood burning stove from thermal stresses as it climbed through 70,000 feet at full throttle. The rocket engine ran out of propellants after 83.4 seconds, as the X-15 was going mach 5.69. Walker noted some yaw instability as he increased the angle of attack to 20 degrees after engine burn out. The instrument that indicated the yaw angle was wired backward, so initially Walker's inputs to the reaction control thrusters increased the yaw angle. He reversed his responses to the sideslip needle, which produced the desired results. He was very pleased with the transition to the Alternate Stability Augmentation System when he shut down the roll channel of the Stability Augmentation System during the coast to 154,000 feet. The behavior of the X-15 hardly changed at all when the ASAS took over.

Another evaluation of the MH-96 adaptive flight control system of the X-15-3 by Neil Armstrong was next on the schedule. A stabilizer position indicator had been added to the instrument panel in the cockpit since the last flight. The flight plan called for a launch over Mud Lake, followed by a 30 degree climb at full throttle to an altitude of 60,000 feet. Armstrong was to pitch over to zero-g flight and then pull up to a 32 degree climb at 81,000 feet. He would shut down the engine at 120,000 feet after an 81-second burn. The X-15 should coast to a maximum altitude of 205,000 feet. During the descent, he was to evaluate the ability of the MH-96 to damp out oscillations about the pitch and roll axes while flying at an angle of attack of 20 degrees. He was expected to level out at 90,000 feet and decelerate before descending to land on Rogers Dry Lake eleven minutes after launch.

The fourth flight of the X-15-3 was postponed once. Armstrong's launch was rescheduled to April 20, just one day after Walker's flight in the X-15-1.

Major Jack Allavie and Major Russell Bement were at the controls of the NB-52B on the morning of April 20. Stanley Butchart manned the launch panel operator's station. There was severe turbulence at the launch altitude. The pitching and rolling of the NB-52B interfered with attempts to get a solid fix from the Doppler radar input for the stable table, so the launch proceeded under the assumption that the inertial velocity supplied to the MH-96 aboard the X-15-3 would be slightly in error.

Armstrong got a good light of the XLR-99 engine on the first try. The flight followed the flight plan closely during the ascent. Armstrong made a series of pullups, evaluating the SAS at angles of attack up to 20 degrees. The X-15 was going mach 5.31 when he shut down the rocket engine eighty-one seconds into the flight. It reached a peak altitude of 207,500 feet.

Armstrong felt that the aircraft control and damping during re-entry were better than expected. The MH-96 system was using reaction control thrusters more than had been expected. That was depleting the hydrogen peroxide that fueled both the thrusters and the Auxiliary Power Units (APUs). The peroxide-low warning lamp came on as the X-15 descended through 160,000 feet. Armstrong swiched on the pump that transferred unused hydrogen peroxide from the engine turbopump to the tank that supplied the thrusters and APUs.

Although the flight plan had called for Armstrong to level out at 90,000 feet, he inadvertantly brought the nose up too high. The X-15-3 skipped back up to an altitude where its wings produced almost no lift or drag. Rather than decelerating, the X-15 continued at nearly unabated speed toward Edwards Air Force Base. Jack Allavie in the NB-52B could see that Armstrong was passing Rogers Dry Lake and called out, "Hard left turn, Neil", over the radio. Armstrong rolled the X-15 onto its left side and pulled back on the stick until the stabilizers were deflected as far as they could go, but the X-15 continued in a nearly straight line. He watched his landing site pass by as he was still traveling mach 3 and heading for Los Angeles.

Armstrong was many miles south of the base, flying over the southern San Gabriel Mountains, far from his planned flight course, when he got the X-15-3 turned around. The sonic boom from the X-15 swept across La Canada and the northern L. A. basin.

Armstrong had the impression that he was "in pretty bad shape for the south lakebed". For a moment he considered putting the X-15 down on the concrete runway at the Palmdale Airport. He pitched the X-15 to the angle of attack that generated the most lift for the least drag to stretch his glide as far as he could. He didn't bother with the usual spiraling descent, just brought it straight in to runway 35 on the south lakebed.

The X-15 pilots had not considered the prospect of landing on Rogers Dry Lake from the south. There were no pre-selected checkpoints to help guide Armstrong to his landing point. Late in the approach, he realized that he would be short of his initial aim point by about two miles. He was flying below the tops of the Joshua Trees before he reached the lakebed, and the X-15 landed on the hard, clay surface just a short distance from the sagebrush. The X-15 touched down 12 minutes and 28 seconds after launch, nearly a minute and a half longer than the original flight plan. This was the longest flight of the X-15 program.

Armstrong had missed his planned landing site by twelve miles. The convoy of recovery vehicles was at the far end of Rogers Dry Lake and would not arrive for a quarter hour.

The primary objective of the next planned X-15 flight was an evaluation of airframe heating and the ASAS of X-15-2 by Al White. The flight plan called for White to make a 20 degree climb at full throttle to an altitude of 54,000 feet, followed by a pushover to zero-g flight. White was to level off at 73,000 feet and throttle back to 30% thrust, adjusting the speed brakes to keep the speed of the X-15 at about 3,400 miles per hour. The engine would burn out after about 103 seconds. After burnout White would turn off the channels of the SAS, one at a time, to evaluate the response of the ASAS.

The sky was overcast on April 24, so the launch was postponed for a day. Major Allavie piloted the NB-52A with the X-15-2 under its wing on April 25. Colonel Charles "Chuck" Yeager made his only flight in the NB-52 mothership that day, serving as co-pilot. His one opportunity to observe an X-15 launch first hand was spoiled by another day of overcast skies.

Lieutenant Colonel Don Anderson replaced Chuck Yeager in the right seat of the NB-52A on April 26. Al White could not get the X-15 engine igniter lit, so the launch was aborted again. White's next X-15 flight was postponed until later in May. Major Robert Rushworth would make the heating test flight in the X-15-2 in early May.

Joe Walker was set to make an altitude build up flight in the X-15-1. Walker's flight plan called for him to make a 38 degree climb at full throttle, shutting down the engine after 81 seconds. Paradoxically, Walker was instructed to extend the speed brakes during the engine burn above 70,000 feet. This improved the directional stability of the X-15 in the rarified upper atmosphere. The X-15 would be going about mach 5.35 at engine burn out. It would coast to a peak altitude of 255,000 feet. Walker would begin his pullout at 180,000 feet and level out at 70,000 feet, landing at Rogers Dry Lake about 11 minutes after launching over Mud Lake.

Walker's flight had already been postponed once when Major Allavie and Squadron Leader Archer took the NB-52B aloft with the X-15-1 on April 27. Cloudy skies over the launch lake forced another scrub of the launch that morning. The launch was rescheduled to April 30. Major Russell Bement was in the co-pilot's seat of the NB-52B for the next launch attempt. Jack Russel sat behind the pilots of the NB-52B, monitoring the systems of the X-15.

The XLR-99 engine lit up right away and Walker established his climb. The flight progressed just as planned. Walker found that he had to strain to reach the throttle to shut off the engine under the force of nearly 3 gs of acceleration. The X-15 was traveling mach 4.73 (3,489 miles per hour) at engine shut down and continued to climb another 20 miles, reaching a peak altitude of 247,000 feet about 80 seconds later. As Walker pushed over at the peak altitude, he got a strong feeling that he was going to overshoot Edwards Air Force Base. The maximum mach number, mach 4.94, was achieved during the descent.

The staff of the NASA Flight Research Center headed over to the Elks club for a party that night to celebrate the new altitude record that Walker had set.

The X-15 Flight Tests, May 1962

At the beginning of May 1962, Major Robert Rushworth was preparing to fly an airframe heating investigation with the X-15-2, but first it would be carried across the country by the NB-52A to appear at the Eglin Air Force Base airshow. Major Bob White was planning to evaluate the performance of the Alternate Stability Augmentation System (ASAS) of the X-15-1 at high angle of attack.

The X-15-2 was displayed at an airshow at Eglin Air Force Base in Florida over the first weekend of May 1962. Major Jack Allavie piloted the NB-52A across the country with the X-15-2 on the pylon on May 2. Major Bob White went along as co-pilot. That was the only occasion on which an NB-52 landed with an X-15 away from Edwards. They returned the X-15-2 to Edwards Air Force Base on May 5.

One of the main parameters that aerospace engineers are concerned with is called dynamic pressure. The dynamic pressure that an airplane encounters is directly related to the speed of the airplane and the density of the atmosphere through which it is flying. The effectiveness of aerodynamic control surfaces and the rate of airframe heating from aerodynamic friction are both related to the value of the dynamic pressure. Engineers use the letter q to represent dynamic pressure. The value of q at typical X-15 launch conditions (45,000 feet altitude and an airspeed of 450 miles per hour) is about 145.

After Major White endured two aborts of the X-15-1 airframe heating flight in April, Major Robert Rushworth was assigned to fly the twenty-second flight of the X-15-1.

The flight plan called for Major Rushworth to make a 20 degree climb at full throttle to an altitude of 54,000 feet, followed by a pushover to zero-g flight. Rushworth was to level off at 73,000 feet and throttle back to 30% thrust, adjusting the speed brakes to keep the speed of the X-15-1 at about 3,400 miles per hour. During this period, the value of dynamic pressure (q) would exceed 2,000 for the first time during an X-15 flight. The engine would burn out after about 103 seconds. After burnout Rushworth would make a 5-g turn to the right. As the X-15 decelerated, he was to turn off the channels of the SAS, one at a time, to evaluate the response of the ASAS.

Major Rushworth was scheduled to fly the X-15-2 on May 7, but overcast skies postponed the launch for a day. The NB-52B took off on May 8 with Major Allavie and Major Russell Bement at the controls. Jack Russel occupied the launch panel operator's station behind the pilots. The number four J57 jet engine malfunctioned and was shut down. The flight progressed on the power of the Stratofortress' other seven engines.

Rushworth triggered the drop of the X-15-2 over Hidden Hills Lake and started climbing at full throttle. He leveled off at 70,000 feet and throttled the XLR-99 engine to 30% thrust. This was the first time that the XLR-99 had flown at less than 50% thrust. Rushworth extended the speed brakes 16 degrees to maintain a speed of mach 5 for 33 seconds. The edges of the speed brake panels were heated to a tempertature of 1,250 degrees Fahrenheit by aerodynamic friction. The pressure in the cockpit of the X-15 dropped, and Rushworth's pressure suit inflated just as the rocket engine consumed the last of its fuel. The X-15 was traveling mach 5.34 (3,524 miles per hour) at engine burn out. Rushworth rolled the X-15 ninety degrees to the right and pulled back on the stick until he was subjected to 4.5 gs. Rushworth was impressed by the "snap, crackle, and pop" sounds emanating from the X-15 as it glided back to Edwards Air Force Base.

The 1962 Edwards Air Force Base Open House was held on May 20. Major Allavie and RAF Squadron Leader Harry Archer piloted the NB-52B as it participated in the rehearsal for the aerial display on May 19. The X-15-3 was mounted on the wing of the NB-52A and they were placed on static display on the flightline during the airshow. Major Miles Burganheim occupied the co-pilot's seat of the NB-52B as Major Allavie flew it past the crowd on May 20.

Rushworth was assigned to fly the twenty-eighth flight of the X-15-1 two days after the open house. The X-15-3 was removed from the pylon of the NB-52A and the X-15-1 took its place. The primary purpose of the flight was an investigation of boundary layer flow around the airframe of the X-15. The flight plan called for Rushworth to pull up to a climb of 30 degrees at full throttle, then push over to zero-g flight until leveling out at an altitude of 90,000 feet. He was to shut down the engine after 77 seconds . After shutting down the engine, he was to pitch the nose up and down in steps of 5 degrees between 10 degrees nose up and ten degrees nose down three times.

Major Allavie and Captain John Campbell were at the controls of the NB-52A on the morning of May 22. Jack Russel managed the systems of the X-15 using the launch panel controls, observing the rocket plane on the twin television monitors that occupied the space between his station and the pilot's seats.

After Rushworth launched the X-15-2 over Hidden Hills Lake, he was immediately aware that its roll stability was not as good as expected. He had to constantly counteract its tendency to roll to the left through the entire flight. At an altitude of 96,000 feet, an overspeed of the turbopump of the XLR-99 triggered an early shut down of the engine after a burn of 75.3 seconds, when the X-15-1 was going mach 5.03 (3,450 miles per hour). It was still climbing and reached a peak altitude of 100,400 feet, over 10,000 feet higher than planned. Rushworth dropped the nose slightly to get it back on profile, then pitched the nose up and down in controlled increments to collect the desired boundary layer flow data.

Major BobWhite was scheduled to make the twenty-third flight of the X-15-2 on May 24. The primary purpose of the flight was to evaluate the performance of the ASAS at an angle of attack of 23 degrees. The flight plan called for White to pull up to a climb angle of 30 degrees at full throttle to an altitude of 56,000 feet, then push over to zero-g flight for forty seconds. Seventy-five seconds into the flight he was to pull up so that the X-15 was pulling 2 gs for the last eighteen seconds of powered flight. After the XLR-99 engine consumed the last of its propellants, White was to pull up to an angle of attack of 23 degrees, disengage the roll channel of the primary Stability Augentation System (SAS) and observe the behavior of the X-15 as the ASAS kicked in. Then he would re-engage the SAS and roll the X-15 thirty degrees to the right while holding the angle of attack at 20 degrees for twenty seconds during the ascent. The X-15 should reach a peak altitude of 162,000 feet three minutes after launch.

Bad weather on the morning of May 24 resulted in a postponement of the flight until the next day. Major Fitzhugh Fulton and Major Russell Bement took the NB-52B aloft with White in the cockpit of the X-15-2 on May 25. As Jack Russel was setting up the inertial navigation system, the stable table overheat light came on, causing the mission to be rescheduled for May 28. It was postponed again to May 29, but the stable table malfunctioned again that day. This was the fourth consecutive launch abort for Major White.

Major Rushworth scheduled to fly the fifth flight of the X-15-3 on May 29. The primary purpose of the flight was to familiarize Rushworth with the operation of the MH-96 adaptive gain flight control system that equipped X-15-3 and to evaluate its control of the reaction control system (RCS) while the X-15 was above the atmosphere. The flight plan called for him to ignite the XLR-99 engine at 75% thrust, then throttle up to 100% thrust and pull up to a climb angle of 32 degrees. He would shut down the rocket engine 77 seconds into the flight, at an altitude of 117,000 feet while the X-15 was going mach 5.15. During the ascent to the peak altitude of 206,000 feet he would roll the X-15 from side to side and then pitch the nose up in 5 degree increments to an angle of attack of 20 degrees. During the descent, he would keep the nose up to pull 4 gs as he reentered the atmosphere.

Major Rushworth was grounded by the flight surgeon on May 29 and again on May 30. The X-15-3 flight was reassigned to Major White, but he was still occupied with the twenty-third flight of the X-15-2. He was scheduled to fly the X-15-2 on June 1 and Joe Walker was on the roster to fly the twenty-ninth flight of the X-15-1 on June 7. The fifth flight of the X-15-3 would wait until later in June.