North American X-15

The North American X-15 is a experimental Avion rocket American, built within the framework of a research program on the flights with very high-speed and very high-altitude. From 1960 to 1968, the 3 built specimens accomplished approximately 200 trial flights on behalf of NASA, pulverizing all the speed records and of altitude held by a Aéronef controlled with fixed wing.

X-15 established final records of 7 272,68 km/h for speed (the October 3rd 1967) and of 107.960 meters for altitude (August 23rd 1963). It made it possible American to collect very many data on the behavior of flows of airs, aerodynamic friction, the control and the stability of an aircraft at high speed and out of the atmosphere, as well as the techniques of re-entry in the atmosphere.

Design

X-15

In February 1954, the National Advisory Committee for Aeronautics (ancestor of NASA) established the need for a new experimental plane to very explore the flights with high-speed and very high-altitude. A research team was charged to find solutions with the many problems arising (heating cynetic, control of the apparatus in a rarefied atmosphere, optimal aerodynamic configuration, etc) and returned a report/ratio in the month of April 1954, indicating that there was no major hurdle within sight of the techniques of the time.

The launching of the project was validated in October 1954, with a financing of 95% by US Air Force and 5% by the US Navy, and an invitation to tender was launched in the tread. The proposal of North American was adopted and an order for the signed construction of 3 specimens in December 1955. In February 1956, the development of the rocket motor was entrusted to Reaction Motors, which had proposed an engine derived from that of the rockets Viking.

A model was presented by North American in December 1956. The construction of the planes started semi-1957 and first X-15 left factory on October 15th, 1958. Engine XLR99 was however very late, since the first was delivered only in April 1959 and that it was still necessary to wait a year more almost so that it is finally qualified. During this time, two Boeing B-52 Stratofortress were modified to be able to carry X-15 in altitude, the future pilots were selected and a simulator built to involve them.

The first trial flights proceeded in the following way:

March 10th, 1959, first flight " captif" of X-15 number 1, which remained hung under the wing of the B-52 of carrying
June 8th, 1959, first flight without use of the engines of X-15 number 1
September 17th, 1959, first flight of X-15 number 2 propelled by two provisional engines XLR 11
November 15th, 1960, first flight of X-15 number 2 propelled by final engine XLR99

These first tests were strewn with many engineering problems involving either the carryforward of flights envisaged or the interruption of a flight in progress. The tests continued despite everything and, at the end of 1960, X-15 had exceeded Mach 3 and 30.000 m of altitude. The plane was then transferred to NASA for the flights from research.

The X-15A-2

After the accident of November 1962 (see below), it was decided to rebuild X-15 number 2 by modifying it on the one hand to make it able to reach a speed of Mach 8 and, on the other hand, so that it can be used as testing ground flying for a Statoréacteur. The plane accepted the designation of X-15A-2 then.

High speed was to be obtained by increasing the operation life of the rocket motor, which required simply a priori to increase the capacity while carburizing/combustive. For that, the fuselage was lengthened and two external additional tanks were installed (one on each side of the fuselage): these tanks were emptied in first then released in flight and recovered.

So that X-15 tolerates the higher temperatures envisaged, there it was decided to cover it with an additional layer of insulator which disaggregated progressively in vol. On its side, the ventral drift was modified to be able to install a ramjet 91 cm in diameter. As it was not any more question of ejecting in flight the lower part, the ground clearance had to be increased.

Lastly, of new compartments were installed to embark the equipment of measurement. The X-15A-2 weighed with final the 10 tons more than X-15, which also forced to reinforce the landing gear seriously.

The new plane undergoes a cycle of tests then:

June 15th, 1964, first flight " captif" while remaining hung under the wing of the B-52 of carrying
June 25th, 1964, first real flight without the tanks nor the ramjet
February 17th, 1965, first flight with the new equipment of measurement
November 3rd, 1965, first flight with the empty external reservoirs
July 1966, first flight with the external reservoirs filled
August 21st, 1967, first flight with the additional layer of insulator

The first flights were marked by several incidents on the level of the landing gear, which tended to be spread in full vol.

In fact the X-15A-2 establishes the speed records by reaching 7 272,68 km/h (the October 3rd 1967). However, during this flight, the temperature on the surface exceeded the 1 300°C envisaged and caused major damage on part of the cell. Although North American gave the plane in state, it finally never took again the air.

Flights of research

The flights of research carried out by NASA initially consisted in gradually increasing speed and altitude:

First flight at more Mach 4 on March 7th, 1961
First flight at more Mach 5 on June 23rd, 1961
First flight with the top of 200.000 feet (60 960 meters) on October 11th, 1961
First flight at more Mach 6 on November 9th, 1961
First flight with the top of 300.000 feet (91 440 meters) on July 17th, 1962

In April 1962, NASA engaged X-15 in a research program including a certain number of scientific experiments, in addition to the experiments and measurements carried out on the plane him even. In 1963/1964, X-15 also took part in the development of the systems of recognition intended for the Lockheed A-12 Oxcart. According to the needs, various additional sensors were added to obtain desired measurements: spectrum of solar light, Ultraviolet radiation, density of the microphone Meteorite S, etc From February 1965, the new equipment of measurement of the X-15A-2 were used for the various scientific experiments envisaged.

The program stop was decided in 1968, mainly following the loss of X-15 number 3 and with a reorientation of the budgets of NASA. The last flight of X-15 took place on October 24th, 1968.

Accidents

November 5th, 1959, X-15 number two yielded suddenly into two at the time of the landing, following one touched a little brutal with a mass more important than envisaged. The pilot left himself there healthy and except. The flight had been stopped because of a fire on one of two engines XLR11.

June 8th, 1960, a ground test of final engine XLR99 finished the destruction of all the back of X-15 number 3 following an explosion. The pilot left himself there healthy and except.

November 9th, 1962, X-15 number 2 was very seriously damaged and its pilot John B. McKay seriously wounded at the time of a landing: following a failure of the control surfaces, the plane much quickly touched the ground too (to 500 km/h) and the left shoe folded under the shock. X-15 then made a barrel before falling down on the back.

November 15th, 1967, X-15 number 3 become unverifiable was subjected to too strong load factors at the time of the descent and disintegrated in vol. the pilot Michael J. Adams was killed.

Pilots

The pilots of X-15 accepted many medals and distinctions for their work and the results obtained. Eights of them exceeded the altitude of 50 miles (80 km) and thus gained the title of astronauts:

Robert Michael White (flight 62)
Robert A. Rushworth (flight 87)
Joseph Albert Walker (flights 90 and 91)
Joseph H. Engle (flights 138,145 and 153)
John B. McKay (flight 150)
Neil Armstrong (7 accomplished flights)
William Joseph Knight (flight 190)
Michael James Adams (flight 191)
William H. Dana (flight 174 and 197)

The international official limit of space being fixed at the altitude of 100 km, this title of astronaut is in recognized fact only by the US Air Force, except for Joseph Albert Walker which exceeded it twice.

Other characteristics

Incompetent to take off by his own means, X-15 was hung under the wing a Boeing B-52 Stratofortress then released with more than 10.000 meters of altitude. The rocket motor was then ignited to propel the plane towards the upper atmosphere, then X-15 followed a trajectory Balistique before going down again in coasting flight like a Planeur (but at speed much obviously higher).

The plane landed on two retractable shoes with the back and a caster with the front one. Au préalable, the lower part of the ventral drift was to be ejected because it was too large compared to the ground clearance of X-15.

X-15 was built with various Alliage S special, of which the Inconel able to tolerate temperatures of 800°C.

The major part of the fuselage contained a tank for 3914 liters of oxygen liquid (Comburant) and another for 5470 liters of ethanol or Ammoniaque (Carburant).

With very high-altitude, directional control was not ensured any more by traditional Gouverne S but by 12 small rockets the Hydrogen peroxide placed in the nose and in end of wings.

X-15 was truffle of measuring instruments intended to collect data during the flights: temperature, pressure, load factors, parameters of flight, physiological parameters of the pilot, etc

The Ejector seat could be used until the speed of Mach 4 and the altitude of 36600 meters.

Anecdote

After having witnessed a flight of Neil Armstrong on board X-15, Jean-Michel Charlier, the inventor of the Cartoon Buck Danny, was impressed so much that it decided to make take part his hero in the trial flights of X-15. This adventure was published in the newspaper of Spirou of 1963 with 1964.

It is mentioned there accident of John B. McKay: Bob Light, one of old the test pilot, broke the leg following the destruction with the aterrissage of the one of the skis of X-15.

See too

External bonds

a very complete article on X-15 on the site xplanes.free.fr
X-15 on the site of NASA
Research result carried out using X-15 on the site of NASA

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