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Information about X 15

X-15
TypeRocket plane
ManufacturerNorth American Aviation
Maiden flight8 June 1959
Introduced17 September 1959
RetiredDecember 1968
StatusMuseum piece
Primary usersU.S.Air Force
NASA
Number built3
“X-15” redirects here. For other uses, see X-15 (disambiguation).
The North American X-15 rocket plane was part of the USAF/NASA/USN X-series of experimental aircraft, including also 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. It could be considered the first manned suborbital spacecraft ever flown.

During the X-15 program, 13 flights (by eight pilots) met the USAF's criteria for a spaceflight by passing an altitude of 50 miles (80 km) and the pilots were accordingly awarded astronaut status by the USAF. Three X-15s pilots also qualified to receive NASA astronaut wings.[1][2]

Some respected aerospace researchers have placed the threshold of space at lower altitudes than the USAF and NASA, so many X-15 pilots could also be considered as astronauts. The "aeropause" region, where space-equivalent conditions are first encountered, starts at an altitude of 19 miles (30 km) above the Earth. Many X-15 pilots traveled through, and far above, the aeropause.

Out of all the X-15 missions, two flights (by the same pilot) also qualified for the international FAI definition of a spaceflight by passing the 62.1 mile (100 km) mark.

Design and development

Enlarge picture
X-15 just after release.
Enlarge picture
X-15 touching down on its skids. Compare jettisoned lower ventral fin with color picture, top.
The original Request for Proposals was issued for the airframe 30 December 1954, and for the rocket engine on 4 February 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. Parts of the fuselage were made of a heat-resistant nickel-based alloy (Inconel-X 750). 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.

Prior to 1958, USAF and NACA (later NASA) officials discussed an orbital X-15, called the "X-15B", to be launched into space atop a Navajo missile. The idea was scrapped after NASA was formed out of NACA and Project Mercury was approved for manned orbital spaceflight. By 1959, the X-20 Dyna-Soar space-glider program became the USAF's preferred means to launch a military manned spacecraft into orbit. The X-20 program was cancelled in the early 1960s.

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

Operational history

Three X-15s were built in all, and they made a total of 199 test flights, the last one on 24 October 1968. Plans were made for a 200th X-15 flight to be launched over Smith Ranch, Nevada. It was scheduled for 21 November 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 20 December 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 15 November 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.

Air Force Test pilot Major Michael J. Adams was killed on 15 November 1967 when his X-15-3 began to spin on descent and then disintegrated when the acceleration reached 15 g (147 m/s²), scattering wreckage over 50 square miles. On 8 June 2004 a memorial monument was erected at the location of cockpit crash sitenear Randsburg, California. Maj. 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 2.4 ft (0.74 m), 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 28 June 1964, and eventually reached a speed of 7,274 km/h (4,520 mph 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 16 November 2004 of nearly Mach 10 (6,600 mph or 10,620 km/h or 2.95 km/s) at 95,000 ft (29 km) is only a record for an air-breathing jet engine.

Five main aircraft were involved in the X-15 program: The three X-15s 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)

Specifications (X-15)

General characteristics

* Crew: one
  • Length: 50 ft 9 in (15.45 m)* Wingspan: 22 ft 4 in (6.8 m)
  • Height: 13 ft 6 in (4.12 m)* Wing area: 200 ft² (18.6 m²)* Empty weight: 14,600 lb (6,620 kg)* Loaded weight: 34,000 lb (15,420 kg)* Max takeoff weight: 34,000 lb (15,420 kg)* Powerplant: 1 Thiokol XLR99-RM-2 liquid-fuel rocket engine, 70,400 lbf at 30 km (313 kN)

Performance

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 an 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 60 miles.

X-15 flights higher than 50 miles (80 km)
Flight Date Top speed Altitude Pilot
Flight 6217 July 19623,831 mph59.6 milesRobert M. White
Flight 7717 January 19633,677 mph51.4 milesJoe Walker
Flight 8727 June 19633,425 mph53.9 milesRobert Rushworth
Flight 9019 July 19633,710 mph65.8 milesJoe Walker
Flight 9122 August 19633,794 mph67.0 milesJoe Walker
Flight 13829 June 19653,431 mph53.1 milesJoseph H. Engle
Flight 14310 August 19653,549 mph51.3 milesJoseph H. Engle
Flight 15028 September 19653,731 mph55.9 milesJohn B. McKay
Flight 15314 October 19653,554 mph50.4 milesJoseph H. Engle
Flight 1741 November 19663,750 mph58.1 milesBill Dana
Flight 19017 October 19673,856 mph53.1 milesPete Knight
Flight 19115 November 19673,569 mph50.3 milesMichael J. Adams†
Flight 19721 August 19683,443 mph50.6 milesBill Dana
† fatal

Fastest flights

X-15 ten fastest flights
Flight Date Top Speed Altitude Pilot
Flight 459 November 19614,092 mph19.2 milesNeil Armstrong
Flight 5927 June 19624,104 mph23.4 milesJoe Walker
Flight 6426 July 19623,989 mph18.7 milesNeil Armstrong
Flight 8625 June 19633,910 mph21.7 milesJoe Walker
Flight 8918 July 19633,925 mph19.8 milesRobert Rushworth
Flight 975 December 19634,017 mph19.1 milesRobert Rushworth
Flight 10529 April 19643,905 mph19.2 milesRobert Rushworth
Flight 13722 June 19653,938 mph29.5 milesJohn B. McKay
Flight 17518 November 19664,250 mph18.7 milesPete Knight
Flight 1883 October 19674,519 mph36.3 milesPete Knight

X-15 Pilots

Pilot Organization Total
Flights		 USAF
space
flights		 FAI
space
flights		 Max
Mach		 Max
speed
(mph)		 Max
altitude
(miles)
Michael J. Adams†U.S. Air Force7105.593,82250.3
Neil Armstrong**NASA700*5.743,98939.2
Scott CrossfieldNorth American Aviation14002.971,95915.3
Bill DanaNASA16205.533,89758.1
Joseph H. Engle**U.S. Air Force1630*5.713,88753.1
Pete KnightU.S. Air Force16106.704,51953.1
John B. McKayNASA29105.653,86355.9
Forrest S. PetersenU.S. Navy5005.33,60019.2
Robert A. RushworthU.S. Air Force34106.064,01753.9
Milt ThompsonNASA14005.483,72340.5
Joe Walker*U.S. Air Force25325.924,10467
Robert M. White††U.S. Air Force16106.044,09259.6


† Killed on X-15 Flight 191.

†† Capt Iven Kincheloe had been selected in September 1957, as the Air Force's project test pilot for the X-15 Program (with Capt Bob White as his alternate) but was killed the following year in an F-104 crash before the X-15 ever flew.

* This pilot crossed the 60 mile mark during the X-15 program.

** These two pilots crossed the 60 mile mark after leaving the X-15 program, Armstrong in Gemini and Apollo and Engle in the Shuttle program.


References

1. ^ Jenkins, Dennis R. Space Shuttle: The History of the National Space Transportation System: The First 100 Missions, 3rd edition. Stillwater, Minnesota: Voyageur Press, 2001. ISBN 0-9633974-5-1.
2. ^ NASA Press Release, NASA astronaut wings award ceremony, August 23, 2005

External links

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United States government human spaceflight programs
ActiveSpace Shuttle • ISS (joint) • Project Constellation (future)
PastX-15 (suborbital) • Mercury • Gemini • Apollo • Apollo-Soyuz Test Project (joint, USSR) • Skylab • Shuttle-Mir (joint, Russia)
CancelledMISS • Orion • Dyna-Soar • Manned Orbiting Laboratory • Space Station Freedom (now ISS) • Orbital Space Plane
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Type rocket plane
Manufacturer Bell Aircraft Corporation
Maiden flight 19 January 1946
Status Retired
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