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North American X-15

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The X-15 in flight, early 1960s
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The X-15 in flight, early 1960s

The North American X-15 rocket plane was perhaps the most important of the USAF/USN X-series of experimental aircraft. Although not as famous as the Bell X-1, the X-15 set numerous speed and altitude records in the early 1960s, reaching the edge of space and bringing back valuable data that was used in the design of later aircraft and spacecraft.

During the X-15 programme, 13 flights met the US criterion for a spaceflight by passing an altitude of 50 miles (80 km) and the pilots were accordingly awarded astronaut status by the USAF. Out of these, 2 also qualified for the international FAI definition of a spaceflight by passing the 62.1 miles (100 km) mark.

Contents

History

X-15 touching down on its skids. Compare ventral fin with flight picture above.
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X-15 touching down on its skids. Compare ventral fin with flight picture above.

The original Request for Proposals was issued for the airframe December 30, 1954, and for the rocket engine on February 4, 1955. North American received the airframe contract in November 1955, and Reaction Motors contracted in 1956 to build the engines.

As with many of the X-aircraft, the X-15 was designed to be carried aloft under the wing of a B-52. The fuselage was long and cylindrical, with fairings towards the rear giving it a flattened look, and it had thick wedge-shaped dorsal and ventral fins. The retractable landing gear consisted of a nose wheel and two skids — to provide sufficient clearance part of the ventral fin had to be jettisoned before landing. The two XLR-11 rocket engines of the initial model X-15A delivered 36 kN (8,000 lbf) of thrust; the "real" engine that came later was a single XLR-99 that delivered 254 kN (57,000 lbf) at sea level, and 311 kN (70,000 lbf) at peak altitude.

The first flight was an unpowered test made by Scott Crossfield on June 8, 1959, who followed up with the first powered flight on September 17. The first flight with the XLR-99 was on 15 November 1960.

Three X-15s were built in all, and they made a total of 199 test flights, the last one on October 24, 1968. Plans were made for a 200th X-15 flight to be launched over Smith Ranch, Nevada. It was scheduled for November 21, 1968 with William J. Knight as the pilot. Various technical and weather delays caused the planned launch to slip at least six times until late December, 1968. Finally after a cancellation on December 20, 1968 due to weather, it was decided there would not be a 200th flight. The X-15 ground crew de-mated the aircraft from the NB-52A, and prepared it for indefinite storage. X-15 #1 was sent to the National Air and Space Museum in Washington, DC. X-15 #2 is on display at the National Museum of the United States Air Force at Wright-Patterson Air Force Base near Dayton, Ohio. X-15 #3, 56-6672, was destroyed in a crash on November 15, 1967.

Twelve test pilots flew the plane, including Neil Armstrong, later the first man on the Moon and Joe Engle who went on to command Space Shuttle missions.

In July and August, 1963, pilot Joe Walker crossed the 100 km altitude mark twice, becoming the first person to enter space twice.

Test pilot Michael J. Adams was killed on November 15, 1967 when his X-15-3 began to spin on descent and then disintegrated when the acceleration reached 15 g (147 m/s²). On June 8, 2004 a memorial monument was erected at the crash site (http://www.check-six.com/Crash_Sites/X-15A_crash_site.htm) near Randsburg, California at coordinates Template:Coor dms. Michael Adams was posthumously awarded astronaut wings for his last flight in the X-15-3, which had attained an altitude of 266,000 feet (81.1 Km). In 1991 Adams' name was added to the Astronaut Memorial at the Kennedy Space Center in Florida.

The second X-15A was rebuilt after a landing accident. It was lengthened by about 0.74 m (2.4 ft), received a pair of auxiliary fuel tanks slung under the fuselage, and was given a heat-resistant surface treatment, the result being called the X-15A-2. It first flew June 28, 1964, and eventually reached a speed of 7,274 km/h (4,520 mi/h or 2,021 m/s).

The altitudes attained by the X-15 remained unsurpassed by any piloted aircraft except the Space Shuttle until the 3rd spaceflight of SpaceShipOne in 2004. The speeds and altitudes have, also, frequently been exceeded by unpiloted air-launched rockets, such as the Pegasus rocket which has carried several satellites all the way into orbit. The widely reported record achieved by the diminutive X-43A scramjet testbed on November 16, 2004 of nearly Mach 10 (10,621 km/h or 2.95 km/s) at 95,000 ft (29 km) is only a record for an air-breathing jet engine.

Specifications (X-15)

Missing image
X-15_three_view_diagram_.png
X-15 Three View Diagram (NASA)

General characteristics

  • Crew: 1
  • Length: 50.7 ft (15.45 m)
  • Wingspan: 22.3 ft (6.8 m)
  • Height: 13.5 ft (4.12 m)
  • Wing area: 200 ft² (18.58 m²)
  • Empty: 14,600 lb (6,623 kg)
  • Loaded: 34,000 lb (15,422 kg)
  • Maximum takeoff: 34,000 lb (15,422 kg)
  • Powerplant: 1x Thiokol XLR99-RM-2 liquid-fuel rocket engine, 70,400 lbf (313 kN) thrust (at 30 km)

Performance

  • Maximum speed: 4,520 mph (7,274 km/h) Mach 6.72
  • Range: 280 miles (450 km)
  • Service ceiling: 67 miles (108 km)
  • Rate of climb: 60,000 ft/min (18,000 m/min)
  • Wing loading: kg/m² ( lb/ft²)
  • Thrust/weight:
  • Serial Numbers: (Five main aircraft were involved in the X-15 program. The three X-15's and two B-52 carrier aircraft.)
    • X-15A-1 - 56-6670, 82 powered flights
    • X-15A-2 - 56-6671, 53 powered flights
    • X-15A-3 - 56-6672, 64 powered flights
    • NB-52A - 52-003 (retired October 1969)
    • NB-52B - 52-008 (retired November 2004)

Record flights

Highest flights

In the United States there are two definitions of how high a person must go to be referred to as an astronaut. The USAF decided to award astronaut wings to anyone who achieved a altitude of 50 miles (80 km) or more. However the FAI set the limit of space at 100 km. Thirteen X-15 flights went higher than 50 miles (80 km) and two of these reached over 100 km.

X-15 flights higher than 50 miles (80 km)
Flight Date Top speed Altitude Pilot
Flight 62 July 17 1962 6,167 km/h 95,940 m Robert M. White
Flight 77 January 17 1963 5,918 km/h 82,810 m Joseph A. Walker
Flight 87 June 27, 1963 5,512 km/h 86,870 m Robert A. Rushworth
Flight 90 July 19, 1963 5,971 km/h 106,010 m Joseph A. Walker
Flight 91 August 22, 1963 6,106 km/h 107,960 m Joseph A. Walker
Flight 138 June 29, 1965 5,523 km/h 85,527 m Joseph H. Engle
Flight 143 August 10, 1965 5,713 km/h 82,601 m Joseph H. Engle
Flight 150 September 28, 1965 6,006 km/h 90,099 m John B. McKay
Flight 153 October 14, 1965 5,720 km/h 81,230 m Joseph H. Engle
Flight 174 November 1, 1966 6,035 km/h 93,543 m William H. Dana
Flight 190 October 17, 1967 6,206 km/h 85,500 m William J. Knight
Flight 191 November 15, 1967 5,745 km/h 81,080 m Michael J. Adams
Flight 197 August 21, 1968 5,541 km/h 81,530 m William H. Dana

Fastest flights

X-15 ten fastest flights
Flight Date Top Speed Altitude Pilot
Flight 45 November 9, 1961 6,587 km/h 30,968 m Neil A. Armstrong
Flight 59 June 27, 1962 6,605 km/h 37,704 m Joseph A. Walker
Flight 64 July 26, 1962 6,420 km/h 30,145 m Neil A. Armstrong
Flight 86 June 25, 1963 6,294 km/h 34,077 m Joseph A. Walker
Flight 89 July 18, 1963 6,317 km/h 31,943 m Robert A. Rushworth
Flight 97 December 5, 1963 6,466 km/h 30,785 m Robert A. Rushworth
Flight 105 April 29, 1964 6,286 km/h 30,968 m Robert A. Rushworth
Flight 137 June 22, 1965 6,338 km/h 47,518 m John B. McKay
Flight 175 November 18, 1966 6,840 km/h 30,145 m William J. Knight
Flight 188 October 3, 1967 7,274 km/h 58,552 m William J. Knight

X-15 Pilots

Pilot Organization Total
Flights
USAF
space
flights
FAI
space
flights
Max
Mach
Max
speed (km/h)
Max
altitude (m)
Michael J. Adams U.S. Air Force 7 1 0 5.59 6,151 81,077
Neil Armstrong NASA 7 0 0 5.74 6,420 63,246
Scott Crossfield North American Aviation 14 0 0 2.97 3,154 24,725
William H. Dana NASA 16 2 0 5.53 6,272 93,543
Joseph H. Engle U.S. Air Force 16 3 0 5.71 6,257 85,527
William J. Knight U.S. Air Force 16 1 0 6.7 7,274 85,496
John B. McKay NASA 29 1 0 5.65 6,217 90,099
Forrest S. Petersen U.S. Navy 5 0 0 5.3 5,794 31,029
Robert A. Rushworth U.S. Air Force 34 1 0 6.06 6,466 86,868
Milton O. Thompson NASA 14 0 0 5.48 5,993 65,258
Joseph A. Walker U.S. Air Force 25 3 2 5.92 6,605 107,960
Robert M. White U.S. Air Force 16 1 0 6.04 6,587 95,936



References

External links

Related content

Related development:

Comparable aircraft: SpaceShipOne

Designation series: X-12 - X-13 - X-14 - X-15 - X-16 - X-17 - X-18

See also:


Lists of Aircraft | Aircraft manufacturers | Aircraft engines | Aircraft engine manufacturers

Airports | Airlines | Air forces | Aircraft weapons | Missiles | Timeline of aviation

de:North American X-15

fi:X-15

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