North American X-15
X-15 in flight, early 1960s
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 100 km (62.5 miles) mark.
| Table of contents |
|
2 General characteristics 3 Highest flights 4 See also 5 References 6 External links |
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 engines of the initial model X-15A delivered 36 kN (8,000 lb) of thrust; the "real" engine that came later was a single XLR-99 that delivered 254 kN (57,000 lb) at sea level, and 311 kN (70,000 lb) 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. Twelve test pilots flew the plane, including Neil Armstrong, later the first man on the Moon. Test pilot Michael James Adams was killed on November 15, 1967 when his X-15 began to spin on descent and then disintegrated when the forces on it hit 15 g.
X-15 touching down on its skids. Compare ventral fin with flight picture above
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 an altitude of 107,960 m (354,200 ft or 67 mi), and a speed of 7,322 km/h (4,520 mi/h or 2,034 m/s).
The speeds and altitudes attained by the X-15 remain unsurpassed by any piloted aircraft. They have, however, 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 March 27, 2004 of Mach 7 at 95,000 ft (approx. 7,590 km/s or 2.1 km/s) is only a record for an air-breathing jet engine.
Of the two surviving X-15s, one is hanging at the National Air and Space Museum in Washington, DC, while the other is at the USAF Museum in Ohio.
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 or more. However the FAA set the limit of space at 100 km. Twelve X-15 flights went higher than 50 miles and two of these reached over 100 km.
History
General characteristics
Highest flights
See also
References
External links
| Related content | |
|---|---|
| Related Development | |
| Similar Aircraft | |
| Designation Series | X-12 - X-13 - X-14 - X-15 - X-16 - X-17 - X-18 |
| Related Lists | List of experimental aircraft - List of rocket planes |
| List of Aircraft - Aircraft Manufacturers - Aircraft Engines - Aircraft Engine Manufacturers |
| Airlines - Air Forces - Aircraft Weapons - Missiles - Years in Aviation |