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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 62.5 miles (100 km) mark.

1 History

The original Request for Proposals was issued for the airframe December 30December 30 is the 364th day of the year (365th in leap years) in the Gregorian Calendar, with 1 day remaining. Events 1460 Wars of the Roses: The Duke of York is defeated at the Battle of Wakefield 1862 USS Monitor sinks off Cape Hatteras, North Carolina, 1954Events January events January 14 The Hudson Motor Car Company merges with Nash-Kelvinator forming the American Motors Corporation January 14 Marilyn Monroe weds Joe DiMaggio. January 15 Mau Mau leader Waruhiu Itote is captured in Kenya January 20 The Nati, and for the rocket engine on February 4February 4 is the 35th day of the year in the Gregorian Calendar. There are 330 days remaining, (331 in leap years). Events 1454 In the Thirteen Years' War, the Secret Council of the Prussian Confederacy sends a formal act of disobedience to the Grand Mas, 19551955 is a common year starting on Saturday. see link for calendar) Events January events January 2 Panama president Jose Antonio Remon is assassinated. January 19 The Scrabble board game debuts. February events February 8 Nikolai Bulganin ousts Georgi Mal. North American received the airframe contract in November 1955, and Reaction Motors contracted in 19561956 is a leap year starting on Sunday. see link for calendar) Events January January 1 End of Anglo- Egyptian Condominium in Sudan. January 16 President Gamal Abdal Nasser of Egypt vows to reconquer Palestine January 26 1956 Winter Olympic Games open in 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-52B-52 Stratofortress Description RoleHeavy bomber, missile platform Crew5aircraft commander, pilot, radar navigator, navigator and electronic warfare officer Dimensions Length159 ft 4 in48. 5 m Wingspan185 ft56. 4 m Height40 ft 8 in12. 4 m Wing area4,000 f. 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 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. 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 near Randsburg, California. The crash site coordinates are 35° 25' 09" N - 117° 36' 08" W. 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 2,034 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 at 95,000 ft (approx. 10,621km/h or 2.95 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 Dayton, Ohio.