30 April 1962: The Chief Research Test Pilot at NASA’s High Speed Flight Station, Joseph Albert Walker, flew the first North American Aviation X-15 hypersonic research aircraft, 56-6670, on its twenty-seventh flight. This was Flight 52 of the NASA X-15 Hypersonic Research Program. The purpose of this test flight was to explore aerodynamic heating and stability at very high altitudes.
At an altitude of approximately 45,000 feet (13,716 meters) over Mud Lake, Nevada, the X-15 was released from Balls 8, the NB-52B drop ship, at 10:23:20.0 a.m., Pacific Daylight Savings Time.
This NASA image depicts three X-15 flight profiles. Mud Lake, Nevada, is near the right edge of the image. (NASA)
Walker started the Reaction Motors XLR99-RM-1 rocket engine. The planned burn time was 81.0 seconds, but the engine ran slightly longer: 81.6 seconds. Even with the longer burn, the X-15 undershot the planned speed of Mach 5.35 and peak altitude of 255,000 feet (77,724 meters). The actual maximum speed for this flight was Mach 4.94, and maximum altitude, 246,700 feet (75,194 meters). Walker landed on Rogers Dry Lake. The total duration of Flight 52 was 9 minutes, 46.2 seconds.
Even though the peak altitude reached by the X-15 was 8,300 feet (2,530 meters) lower than expected, Joe Walker established a new Fédération Aéronautique Internationale (FAI) World Record for Altitude Gain, Aeroplane Launched from a Carrier Aircraft, of 61,493 meters (201,749 feet).¹
Joe Walker with the Number 2 North American Aviation X-15, 56-6671, on Rogers Dry Lake. Walker is wearing a David Clark Co. MC-2 full-pressure suit (NASA)
20 April 1962: “Neil’s Cross-Country.” NASA Research Test Pilot Neil Alden Armstrong conducts a flight to test the Minneapolis-Honeywell MH-96 flight control system installed in the third North American Aviation X-15, serial number 56-6672. The new system combined both aerodynamic and reaction thruster flight controls in one hand controller rather than the two used in X-15s -670 and -671, simplifying the tasks for the pilot.
On its fourth flight, -672 was air-dropped from the Boeing NB-52B Stratofortress drop ship, Balls 8, over Mud Lake, Nevada. Armstrong fired the Reaction Motors XLR99-RM-1 engine and let it burn for 82.4 seconds. The X-15 accelerated to Mach 5.31 (3,789 miles per hour/6,098 kilometers per hour). After the engine was shut down, the rocketplane continued to its peak altitude on a ballistic trajectory, reaching 207,500 feet (63,246 meters) before going over the top and beginning its descent back toward the atmosphere. The test of the new flight control system went well.
Neil Armstrong began to pull out of the descent at about 100,000 feet (30,480 meters), but the X-15 “ricocheted” off the top of the atmosphere and climbed back to 115,000 feet (35,052 meters) where the aerodynamic control surfaces could not function. He used the reaction thrusters to turn toward the dry lake landing area at Edwards Air Force Base, but although the X-15 rolled into a left bank, it would not change direction and still in ballistic flight, went zooming by Edwards at Mach 3 and 100,000 feet in a 90° left bank.
As the X-15 dropped back into the atmosphere, Armstrong was finally able to get it slowed down, but he was far south of his planned landing site. By the time he got -672 turned around he was 45 miles (72.4 kilometers) to the south, over the Rose Bowl in Pasadena, and gliding through 45,000 feet (13,716 meters). There was real doubt that he would be able to make the X-15 stretch its glide to reach the dry lake.
In a masterful display of airmanship, Neil Armstrong was able to get the X-15 to reach the south end of the dry lake, 12 miles (19.3 kilometers) from the planned landing spot to the north. But it was a very close call. In debriefing, the pilots of the four F-104 chase planes were asked how much clearance Armstrong had as he crossed over the Joshua trees at the edge of the lake bed. One of them answered, “Oh, at least 100 feet—on either side.”
At 12 minutes, 28.7 seconds, this was the longest flight of the entire X-15 program. It is called “Neil’s cross-country flight.”
A U.S. Navy fighter pilot who flew 78 combat missions during the Korean War, Neil Armstrong became a civilian test pilot at NACA (National Advisory Committee on Aeronautics, the predecessor to NASA) in 1955. He made 7 flights in the X-15 before transferring to NASA’s Project Gemini in 1962.
Armstrong was command pilot for Gemini 8 and Gemini 11, commander of the backup flight crew of the Apollo 8 mission, and was commander of Apollo 11.
On 20 July 1969, Neil Alden Armstrong was the First Man To Stand on the Surface of The Moon.
Major Robert Michael White, United States Air Force, with a North American Aviation, Inc., X-15 hypersonic research rocketplane, at Edwards Air Force Base, California, 19 November 1959. (Arnold Newman)
Robert Michael White was born 6 July 1924, in Manhattan, New York City. He was the first of two sons of Michael White, a baker, and Helen (Karoline) Butz White, an immigrant from Austria. He attended a vocational high school in The Bronx where he studied to be an electrician. After school and on weekends, White worked as a telegram messenger for Western Union.
White enlisted in the United States Army Air Forces as an Aviation Cadet in November 1942. When he completed flight training in February 1944, White was commissioned as a second lieutenant. He had been trained as a fighter pilot and was sent to England to join the 354th Fighter Squadron, 355th Fighter Group, at RAF Steeple Morden in Hertfordshire. He first entered combat during July 1944 flying the North American Aviation P-51 Mustang.
In this photograph, Lieutenant Robert M. White is on the right, with Lieutenant F. Mark Johnson (left) and Major Lee G. Mendenhall (center), all of the 354th Fighter Squadron, 355th Fighter Group. Lieutenant Johnson’s fighter, “Sweet Dosey II,” is a North American Aviation P-51D-10-NA Mustang, 44-14089. (Little Friends)North American Aviation P-51B/C Mustangs of the 354th Fighter Squadron. Lieutenant White’s fighter was coded WR-V. (U.S. Air Force)
On his 52nd combat mission, 23 February 1945, White, call sign “Falcon Green One,” was strafing Neuberg Airfield in Germany, when his North American Aviation P-51C-10-NT Mustang 42-103795, WR-V, Dutchess of Manhattan, was hit by ground fire. Too low to bail out, he crash landed in a forest clearing near Boehnfeld. (MACR 12398)
MACR 12398, statement of Falcon Green Two.
White was captured and held as a prisoner of war. He was moved around to various POW camps in Germany before being taken to Stalag III-D in Berlin. A railroad train on which he was being moved was strafed by American P-51 fighters. Many passengers were wounded or killed, but White was unhurt. As the Allies advanced, this camp was evacuated and the prisoners were marched 110 miles (177 kilometers) to Stalag VII-A in southern Bavaria. Stalag VII-A was the largest POW camp in Germany, with more than 130,000 Allied prisoners.
“Aerial view of German prison of war camp Stalag 7A near Moosburg, Bavaria, Germany, where thousands of US AF prisoners of war were imprisoned along with thousands of allied prisoners of various nationalities. Most AF prisoners arrived here from Stalag Luft III, Sagen Germany about 4th Feb 45. This photo was taken 20 days before the camp was liberated by US ground forces. The German guard garrison was housed in the group of long barrack buildings in the right centre of the photo. Parked in the parade ground are 22 white GI trucks which delivered thousands of red cross food parcels to the hungry POW’s. 9th April 1945.” (American Air Museum in Britain UPL 36313)
Stalag VII-A was liberated by Combat Command A, 14th Armored Division, Seventh Army, on 29 April 1945. White was taken to a relocation center in France, then eventually returned to America aboard a Liberty ship. Lieutenant White was released from active duty at Fort Dix, New Jersey, but retained an officer’s commission in the USAAF Reserve.
While attending New York University (NYU), he made regular currency flights at Mitchel Field, flying a North American Aviation AT-6 Texan.
Identical to the Inglewood, California-built North American Aviation P-51B Mustang, this is a Dallas, Texas-built P-51C-1-NT, 42-103023. (North American Aviation, Inc.)
On 7 February 1948, Bob White married Miss Doris M. Allen at the Holy Name Church in New York. They would have four children.
Bob White graduated from NYU in May 1951 with a Bachelor of Science degree in Electrical Engineering (BSEE).
During the Korean War, White was recalled to active duty, assigned as a pilot and engineering officer, 514th Troop Carrier Wing, Mitchel AFB, New York. In February 1952 he was sent to the 40th Fighter Interceptor Squadron, 35th Tactical Fighter Wing, at Johnson Air Base near Tokyo, Japan, flying F-51 Mustangs. As the unit transitioned to jet fighters, Lieutenant White received 50 hours of training in the Lockheed T-33, and was then assigned to fly F-80 Shooting Stars. He applied for a commission as a regular officer in the U.S. Air Force, which was approved, and he was promoted to the rank of captain. After 18 months overseas, he returned to the United States to attend the Squadron Officer’s School at Maxwell AFB, Alabama. He finished first in his class.
While at Maxwell, Captain White applied to the Test Pilot School at Edwards AFB in California. He was accepted and in June 1954 began 6 months of training at Edwards. On completion of the school, he was assigned to Edwards under Lieutenant Colonel Frank Kendall (“Pete”) Everest, chief of flight test operations. He flew “chase” in the F-86 and F-100, made test flights in the Convair F-102, North American F-86K Sabre, Northrop F-89H Scorpion, the Ryan X-13, and the Republic YF-105A and F-105B Thunderchief.
Republic F-105B-1-RE Thunderchief 54-102. Captain Bob White test flew the YF-105A and F-105B Thunderchief when he was at Edwards AFB. (U.S. Air Force)
When the Air Force’s selection to test the North American Aviation X-15, Captain Iven Kincheloe, was killed, White was assigned to the X-15 hypersonic research program.
The X-15 is dropped from the NB-52 at an altitude of 45,000–50,000 feet, at Mach 0.82. (NASA)
Major White flew 16 flights in the X-15 rocket plane over a 32 month period. He was the third pilot to fly the X-15, and he was the first pilot to exceed Mach 4, Mach 5 and Mach 6. His maximum speed during the program was Mach 6.04 (4,093 miles per hour/6,589 kilometers per hour), 9 November 1961. On 17 July 1962, he flew the X-15 to an altitude of 314,750 feet (95,936 meters). He set a Fédération Aéronautique Internationale world record for altitude gain (aircraft launched from a carrier aircraft), of 82,190 meters (269,652 feet),¹ and qualified as an Air Force astronaut.
A. Scott Crossfield, Major Bob White and NASA test pilot Neil Armstrong, at the X-15-2 delivery ceremony 7 February 1961, NASA Dryden Flight Research Center, Edwards AFB,California. (AFFTC/HO/Jet Pilot Overseas)
On 28 November 1961, President John F. Kennedy presented Major White with the Harmon Trophy.
President John F. Kennedy presents the 1961 Harmon International Trophy for Aviators to A. Scott Crossfield, Joseph A. Walker, and Major Robert M. White. (L-R) Harrison A. Storms; Thomas Scott Crossfield and Paul Scott Crossfield (sons of A. Scott Crossfield); Joseph V. Charyk, Under Secretary of the Air Force; President Kennedy; Joseph A. Walker; Major Alexander P. de Seversky; Major Robert M. White; Colonel Ansel E. Talbert; Colonel Bernt Balchen; William E. Schramek; unidentified man. Fish Room, White House, Washington, D.C.
In 1962, President Kennedy present him with the Collier Trophy.
Major Robert M. White, May 1962. (TPFLTE)FAI # 9604-1 (Fédération Aéronautique Internationale)Robert M. White and the X-15 (USAF 071203-F-9999J-130)FAI Record File Number 9604 (Fédération Aéronautique Internationale)
Major White was featured on the cover of LIFE Magazine, the most widely read magazine in America, 3 August 1962.
Major Robert M. White, U.S. Air Force, is greeted by his son after his record-setting flight into space. “Boy, what a ride.” (Lawrence Schiller/LIFE Magazine)
After almost nine years as a test pilot at Edwards, Major White returned to operational duties, first being assigned to Wright-Patterson Air Force Base, and then in October 1963, to the 22nd Tactical Fighter Squadron, 36th Tactical Fighter Wing, at Bitburg Air Base, Germany, as operations officer. The squadron was equipped with the F-105, which White had tested at Edwards.
After five months at Bitburg, he was given command of the 53rd Tactical Fighter Squadron, which also flew the F-105.
Lieutenant Colonel Robert M. White with a Republic F-105 Thunderchief, Bitburg AB, Germany.
After his tour in Germany, White returned to the United States, and from August 1965 to 1966, attended the Industrial College of the Armed Forces in Washington, D.C. He also attended George Washington University where he earned a master’s degree in business administration. He was then assigned to the Air Force Systems Command at White-Patterson AFB in Ohio as the chief tactical systems officer in the F-111 Systems Program Office.
In May 1967, Colonel White deployed to Southeast Asia as deputy commander of the 355th Tactical Fighter Wing at Takhli Royal Thai AFB. He flew 70 combat missions in the Republic F-105 Thunderchief.
Colonel Robert M. White, United States Air Force, Deputy Commander for Operations, 355th Tactical Fighter Wing, Takhli RTAFB, 1967, with other Republic F-105 Thunderchief pilots. Colonel White is the third from the left. (U.S. Air Force)
For his actions during an attack against the Paul Doumer Bridge near Hanoi, 11 August 1967, Colonel White was awarded the Air Force Cross.
Doumer Bridge, by Keith Ferris, oil on panel, depicts Col. Robert M. White leading the strike against the Paul Doumer Bridge, 11 August 1967. (United States Air Force art collection)Air Force Cross
The President of the United States of America, authorized by Title 10, Section 8742, United States Code, takes pleasure in presenting the Air Force Cross to Colonel Robert M. White (AFSN: 0-24589A), United States Air Force, for extraordinary heroism in military operations against an opposing armed force as an F-105 Mission Commander and Pilot of the 355th Tactical Fighter Wing, Takhli Royal Thai Air Base, Thailand, in action near Hanoi, North Vietnam, on 11 August 1967. On that date, Colonel White led the entire combat force against a key railroad and highway bridge in the vicinity of Hanoi. In spite of 14 surface-to-air missile launches, MiG interceptor attacks, and intense anti-aircraft artillery fire, he gallantly led the attack. By being the first aircraft to dive through the dark clouds of bursting flak, Colonel White set an example that inspired the remaining attacking force to destroy the bridge without a single aircraft being lost to the hostile gunners. Through his extraordinary heroism, superb airmanship, and aggressiveness in the face of hostile forces, Colonel White reflected the highest credit upon himself and the United States Air Force.
Action Date: 11-Aug-67
Service: Air Force
Rank: Colonel
Company: Deputy Commander for Operations
Regiment: 355th Tactical Fighter Wing
Division: Takhli Royal Thai Air Base, Thailand
The AFC was presented to Colonel White by President Lyndon B. Johnson at a ceremony held at Cam Ranh Bay, December 1967.
In October 1967, Colonel White was assigned as chief, attack division, Directorate of Combat Operations, Seventh Air Force, at Tan San Nhut Air Base.
In June 1968, Colonel White returned to White-Patterson Air Base AFSC, Aero Systems Division, as director of the F-15 systems program.
F-15 Eagles from the 44th Fighter Squadron, Kadena Air Base, Japan, fly over the Pacific Ocean Aug. 9 during Exercise Valiant Shield. During the exercise, Air Force aircraft and personnel will participate in integrated joint training with Navy and Coast Guard forces. (U.S. Air Force photo/Senior Airman Miranda Moorer)
In August 1970, Colonel White returned to Edwards Air Force Base where he took command of the Air Force Flight Test Center.
In October 1971, he attended the U.S. Navy parachute test pilot school. In November 1972, Brigadier General White took command of the Air Force Reserve Officers Training Corps (AFROTC) at Maxwell AFB.
Major General Robert M. White, U.S. Air Force
On 12 February 1975, White was promoted to the rank of major general, with his date of rank retroactive to 1 July 1972. The following month, he took command of the Fourth Allied Tactical Air Force, based at Ramstein Air Base, Germany.
In 1980, Major General White and his wife, Doris, divorced. She returned to the United States.
In December 1980, White married his second wife, Ms. Christa Katherina Kasper (née ScChrista Katherina Shmenger) (b. 3 Dec. ’42, Pirmasens, Germany. Daughter: Judith Kasper)
In 1981, Major General White retired from the U.S. Air Force after 39 years of service. During his military career, he had been awarded the Air Force Cross, the Distinguished Service medal with oak leaf cluster (two awards); the Silver Star with three oak leaf clusters (four awards); the Legion of Merit with four oak leaf clusters (five awards); the Bronze Star; and the Air Medal with sixteen oak leaf clusters (seventeen awards). He wore the wings of a command pilot astronaut.
He had also been awarded the Harmon and Collier Trophies, and the NASA Distinguished Service Medal.
At Edwards Air Force Base, a street is named Bob White Drive in his honor.
In 2006, White was inducted into the National Aviation Hall of Fame.
Mrs. Christa White died 9 January 2007.
Major Robert M. White, U.S. Air Force, with a North American Aviation X-15 on Rogers Dry Lake, 7 Feb 1961. (NASA) Flight 33. Mach 3.50, 78,150′, last XLR-11 flight. major White is wearing a David Clark Company MC-2 full-pressure suit with an MA-3 helmet.28 Nov 1961 JFKWHP-KN-C1957018 July 1962 JFKWHP-AR7365-D18 July 1962 JFKWHP-AR7365-DNASM-SI-92-13598
Major General Robert Michael White, United States Air Force (Retired), died at 11:55p.m., 17 March 2010 at an assisted living facility in Orlando, Florida. His remains were interred at the Arlington National Cemetery.
Tom Wolfe, author of The Right Stuff, described General White as “the eternally correct and reserved Air Force blue suiter.” In The Right Stuff he wrote:
“He didn’t drink. He exercised like a college athlete in training. He was an usher in the Roman Catholic chapel of the base and never, but never, missed Mass. He was slender, black-haired, handsome, intelligent—even cultivated, if the truth were known. And he was terribly serious.”
“White had not unbent as much as one inch for the occasion. You could see them straining to manufacture on of those ‘personality profiles’ about White, and all he would give them was the Blue Suit and a straight arrow. That was Bob White.”
RMW Arlington (Anne Cady)
Recommended: Higher and Faster: Memoir of a Pioneering Air Force Test Pilot, by Robert M. White and Jack L. Summers. McFarland & Company, Inc., Jefferson, North Carolina, 2010
North American Aviation X-15A 56-6670 carried aloft by Boeing NB-52A Stratofortress 52-003. The absence of frost on the fuselage of the X-15 shows that no cryogenic propellants are aboard for this captive flight. The chase plane is a Lockheed F-104A-15-LO Starfighter, 56-0768. This Starfighter suffered an engine failure on take off at Edwards AFB, crashed and was destroyed, 30 June 1959. (NASA)
10 March 1959: With North American Aviation’s Chief Engineering Test Pilot Albert Scott Crossfield in its cockpit, the X-15 hypersonic research rocket plane was airborne for the first time. X-15A 56-6670 was carried aloft under the wing of the Boeing NB-52A Stratofortress drop ship, 52-003, for a series of captive flights. The purpose was to verify that all the systems on both the X-15 and the B-52 were properly functioning up to the point that the drop would occur.
The NB-52A Stratofortress flight crew, left to right: Harry W. (“Bill”) Berkowitz, NAA, Launch Panel Operator; Captain John E. (“Jack”) Allavie, USAF, Pilot; Captain Charles C. Bock, Jr., USAF, Aircraft Commander, at Edwards AFB, 7 February 1959. (U.S. Air Force via Jet Pilot Overseas)North American Aviation X-15A 56-6670 carried aloft by Boeing NB-52A Stratofortress 52-003. The absence of frost on the fuselage of the X-15 shows that no cryogenic propellants are aboard for this captive flight. (NASA)
Fully settled in my tiny flight office, I could speak by radio to the B-52 pilot, Charlie Bock, who was about thirty feet away in the nose of the mother plane, out of sight. . .
As we sat, waiting at the end of the long runway while chase planes took off and circled, the clock on the instrument panel of the X-15 showed 0955. . . On signal, B-52 pilot Charlie Bock cobbed the eight engines, standing hard on the brake pedal. As the engines wound up to full military power, the X-15 trembled and the noise was tremendous. Through my radio earphones I heard Bock call a countdown for the benefit of the official movie cameramen who would record every inch of the takeoff:
“Five . . . four . . . three . . . two . . . one. BRAKE RELEASE.”
One hundred thirty tons of aluminum, fuel, Inconel X, five men and the hope of a nation began rolling down the long runway. . .
As we rolled, the huge runway distance markers flashed by, clocking our path: 14,000 . . . 13,000 . . . 12,000 . . . 8,000. When the X-15 air-speed indicator reached 170 knots, I noted only a minor vibration. We would continue the takeoff. 6,000 . . . 5,000 . . . 4,000, and we broke ground. It was smooth and gentle, like the take-off of an airliner. The air-speed indicator crept up to 260 knots. The parched brown desert fell away. . . .
—Always Another Dawn: The Story of a Rocket Test Pilot, by A. Scott Crossfield and Clay Blair, Jr., The World Publishing Company, Cleveland and New York, 1960, Chapters 34 and 35 at Pages 316–321.
X-15A 56-6670 under the wing of NB-52A 52-003 at high altitude. Scott Crossfield is in the cockpit of the rocketplane. (Air Force Flight Test Center History Office, U.S. Air Force)
The gross weight of the combined aircraft was 258,000 pounds (117,000 kilograms). After a takeoff roll of 6,200 feet (1,890 meters) the B-52/X-15 lifted of at 168 knots (193 miles per hour/311 kilometers per hour). During the 1 hour, 8 minute flight the the B-52 climbed to 45,000 feet (13,716 meters) and reached a speed of 0.83 Mach (548 miles per hour/881 kilometers per hour).
The X-15A rocketplane was designed and built for the U.S. Air Force and the National Advisory Committee for Aeronautics (NACA, the predecessor of NASA) by North American Aviation, Inc., to investigate the effects of hypersonic flight (Mach 5+). Design work started in 1955 and a mock-up had been completed after just 12 months. The three X-15s were built at North American’s Los Angeles Division, at the southeast corner of Los Angeles International Airport (LAX), on the shoreline of southern California.
Test pilot Albert Scott Crossfield with X-15 56-6670 attached to the right wing pylon of NB-52A 52-003 at Edwards Air Force Base. (North American Aviation Inc.)
The first flight took place 8 June 1959, again, with Scott Crossfield in the cockpit of the Number 1 ship, 56-6670.
While earlier rocketplanes, the Bell X-1 series, the the Douglas D-558-II, and the Bell X-2, were airplanes powered by rocket engines, the X-15 was a quantum leap in technology. It was a spacecraft.
Like the other rocketplanes, the X-15 was designed to be carried aloft by a “mothership,” rather than to takeoff and climb to the test altitude under its own power. The carrier aircraft was originally planned to be a Convair B-36 intercontinental bomber but this was soon changed to a Boeing B-52 Stratofortress. Two B-52s were modified to carry the X-15: NB-52A 52-003, The High and Mighty One, and NB-52B 52-008, Balls 8.
From 8 June 1959 to 24 October 1968, the three X-15s were flown by twelve test pilots, three of whom would qualify as astronauts in the X-15. Two would go on to the Apollo Program, and one, Neil Alden Armstrong, would be the first human to set foot on the surface of the Moon, 20 July 1969. Joe Engle would fly the space shuttle. Four of the test pilots, Petersen, White, Rushworth, and Knight, flew in combat during the Vietnam War, with Bob White being awarded the Air Force Cross. Petersen, Rushworth and White reached flag rank.
One pilot, John B. (“Jack”) McKay, was seriously injured during an emergency landing at Mud Lake, Nevada, 9 November 1962. Michael James Adams, was killed when the Number 3 ship, 56-6672, went into a hypersonic spin and broke up on the program’s 191st flight, 15 November 1967.
Scott Crossfield prepares for a flight in the North American Aviation X-15A. Crossfield is wearing a David Clark Co. MC-2 full-pressure suit and MA-3 helmet, which he helped to develop. (NASA)
Flown by a single pilot/astronaut, the X-15 is a mid-wing monoplane with dorsal and ventral fin/rudders and stabilators. The wing had no dihedral, while the stabilators had a pronounced 15° anhedral. The short wings have an area of 200 square feet (18.58 square meters) and a maximum thickness of just 5%. The leading edges are swept to 25.64°. There are two small flaps but no ailerons. The entire vertical fin/rudder pivots for yaw control.
Above 100,000 feet (30,840 meters) altitude, conventional aircraft flight control surfaces are ineffective. The X-15 is equipped with a system of reaction control jets for pitch, roll and yaw control. Hydrogen peroxide was passed through a catalyst to produce steam, which supplied the control thrusters.
The forward landing gear consists of a retractable oleo strut with steerable dual wheels and there are two strut/skids at the rear of the fuselage. The gear is retracted after the X-15 is mounted on the NB-52 and is extended for landing by its own weight.
X-15A cockpit with original Lear Siegler instrument panel. (NASA)
The rocketplane’s cockpit featured both a conventional control stick as well as side-controllers. It was pressurized with nitrogen gas to prevent fires. The pilot wore an MC-2 full-pressure suit manufactured by the David Clark Company of Worcester, Massachusetts, with an MA-3 helmet. The suit was pressurized below the neck seal with nitrogen, while the helmet was supplied with 100% oxygen. This pressure suit was later changed to the Air Force-standardized A/P22S.
The X-15 is 50.75 feet (15.469 meters) long with a wing span of 22.36 feet (6.815 meters). The height—the distance between the tips of the dorsal and ventral fins—is 13.5 feet (4.115 meters). The stabilator span is 18.08 feet (5.511 meters). The fuselage is 4.67 feet (1.423 meters) deep and has a maximum width of 7.33 feet (2.234 meters).
North American Aviation, Inc. X-15A 56-6670 on Rogers Dry Lake, Edwards Air Force Base, California. (NASA)
The X-15s were built primarily of a nickel/chromium/iron alloy named Inconel X, along with corrosion-resistant steel, titanium and aluminum. Inconel X is both very hard and also able to maintain its strength at the very high temperatures the X-15s were subjected to by aerodynamic heating. It was extremely difficult to machine and special fabrication techniques had to be developed.
Since the X-15 was built of steel rather than light-weight aluminum, as are most aircraft, it is a heavy machine, weighing approximately 14,600 pounds (6,623 kilograms) empty and 34,000 pounds (15,422 kilograms) when loaded with a pilot and propellants. The X-15s carried as much as 1,300 pounds (590 kilograms) of research instrumentation, and the equipment varied from flight to flight. The minimum flight weight (for high-speed missions): was 31,292 pounds (14,194 kilograms) The maximum weight was 52,117 pounds (23,640 kilograms) at drop (modified X-15A-2 with external propellant tanks).
Initial flights were flown with a 5 foot, 11 inch (1.803 meters)-long air data boom at the nose, but this would later be replaced by the “ball nose” air sensor system. The data boom contained a standard pitot-static system along with angle-of-attack and sideslip vanes. The boom and ball nose were interchangeable.
Two Reaction Motors Division XLR11-RM-5 four-chamber rocket engines installed on an X-15. (NASA)
Delays in the production of the planned Reaction Motors XLR99 rocket engine forced engineers to adapt two vertically-stacked Reaction Motors XLR11-RM-5 four-chamber rocket engines to the X-15 for early flights. This was a well-known engine which was used on the previous rocketplanes. The XLR11 burned a mixture of ethyl alcohol and water with liquid oxygen. Each of the engines’ four chambers could be ignited individually. Each engine was rated at 11,800 pounds of thrust (58.49 kilonewtons) at Sea Level.
The Reaction Motors XLR99-RM-1 rocket engine was throttleable by the pilot from 28,500 to 60,000 pounds of thrust. The engine was rated at 50,000 pounds of thrust (222.41 kilonewtons) at Sea Level; 57,000 pounds (253.55 kilonewtons) at 45,000 feet (13,716 meters), the typical drop altitude; and 57,850 pounds (257.33 kilonewtons) of thrust at 100,000 feet (30,480 meters). Individual engines varied slightly. A few produced as much as 61,000 pounds of thrust (271.34 kilonewtons).
The XLR99 burned anhydrous ammonia and liquid oxygen. The flame temperature was approximately 5,000 °F. (2,760 °C.) The engine was cooled with circulating liquid oxygen. To protect the exhaust nozzle, it was flame-sprayed with ceramic coating of zirconium dioxide. The engine is 6 feet, 10 inches (2.083 meters) long and 3 feet, 3.3 inches (0.998 meters) in diameter. It weighs 910 pounds (413 kilograms). The Time Between Overhauls (TBO) is 1 hour of operation, or 100 starts.
Thiokol Reaction Motors Division XLR99-RM-1 rocket engine. (U.S. Air Force)
The XLR99 proved to be very reliable. 169 X-15 flights were made using the XLR99. 165 of these had successful engine operation. It started on the first attempt 159 times.
The highest speed achieved during the program was with the modified number two ship, X-15A-2 56-6671, flown by Pete Knight to Mach 6.70 (6,620 feet per second/4,520 miles per hour/ kilometers per hour) at 102,700 feet (31,303 meters). On this flight, the rocketplane exceeded its maximum design speed of 6,600 feet per second (2,012 meters per second).
The maximum altitude was reached by Joe Walker, 22 August 1963, when he flew 56-6672 to 354,200 feet (107,960 meters).
The longest flight was flown by Neil Armstrong, 20 April 1962, with a duration of 12 minutes, 28.7 seconds.
North American Aviation X-15A-1 56-6670 is on display at the Smithsonian Institution National Air and Space Museum. X-15A-2 56-6671 is at the National Museum of the United States Air Force.
North American Aviation Inc./U.S. Air Force/NASA X-15A 56-6670 hypersonic research rocketplane on display at the National Air and Space Museum. (NASM)
Major Robert M. White, U.S. Air Force, climbs out of the cockpit of an X-15 after landing on Rogers Dry Lake at Edwards Air Force Base. (U.S. Air Force)
7 March 1961: Launched over Silver Lake, a dry lake bed near the California/Nevada border, at 10:28:33.0 a.m., Pacific Standard Time, test pilot Major Robert M. White, U.S. Air Force, flew the number two North American Aviation X-15 hypersonic research rocketplane, 56-6671, to Mach 4.43 (2,905 miles per hour/4,675 kilometers per hour) and 77,450 feet (23,607 meters), becoming the first pilot to exceed Mach 4.
This was the first flight for the number two X-15 with the Reaction Motors XLR99-RM-1 engine, which was rated at 57,000 pounds of thrust (253.55 kilonewtons).
The flight plan called for a burn time of 116 seconds, an altitude of 84,000 feet (25,603 meters) and a predicted maximum speed of Mach 4.00. The actual duration of the engine burn was 127.0 seconds. Peak altitude was lower than planned, at 77,450 feet (23,607 meters). The longer burn and lower altitude translated into the higher speed.
The total duration of the flight, from the air drop from the Boeing NB-52B Stratofortress carrier, 52-008, to touchdown at Edwards Air Force Base, was 8 minutes, 34.1 seconds.
Major Robert M. White, U.S. Air Force, with a North American Aviation, Inc., X-15 rocketplane on Rogers Dry Lake, 1961. White is wearing a David Clark Co. MC-2 full-pressure suit with an MA-3 helmet. (NASA)
