X-15 rocketplane

Description:

• The North American X-15 was a hypersonic rocket-powered aircraft operated by the United States Air Force and the National Aeronautics and Space Administration as part of the X-plane series of experimental aircraft. The X-15 set speed and altitude records in the 1960s, reaching the edge of outer space and returning with valuable data used in aircraft and spacecraft design. The X-15′s official world record for the highest speed ever recorded by a crewed, powered aircraft, set in October 1967 when William J. Knight flew at Mach 6.70 at 102,100 feet (31,120 m), a speed of 4,520 miles per hour (7,274 km/h; 2,021 m/s), remains unbroken.
• During the X-15 program, 12 pilots flew a combined 199 flights. Of these, 8 pilots flew a combined 13 flights which met the Air Force spaceflight criterion by exceeding the altitude of 50 miles (80 km), thus qualifying these pilots as being astronauts. The Air Force pilots qualified for military astronaut wings immediately, while the civilian pilots were eventually awarded NASA astronaut wings in 2005, 35 years after the last X-15 flight.
  
• The X-15 was arguably the most successful high-speed flight research program ever undertaken. The X-15 was constructed specifically to explore the hypersonic (Mach 5+) flight regime, along with the necessary structures, propulsion systems, and control techniques. Although widely discounted at the time, a secondary purpose of the original X-15 program was to explore the possibilities of flight outside the sensible atmosphere.
• The aircraft proved remarkably flexible as a research tool. In fact, most of the later flights used the X-15 as a carrier vehicle for other experiments rather than as a research aircraft in its own right. An assortment of experiments were carried, including micrometeorite collection pods, missile detection systems, samples of insulation destined for the Saturn launch vehicle, and a wide variety of others. The aircraft itself demonstrated a large, man-rated throttle able rocket engine, Inconel X heat-sink construction, and an advanced adaptive control system.
• Of the three X-15s manufactured, one was rebuilt as the X-15A-2 after an accident, one crashed while returning from space, killing test pilot Major Michael J. Adams, and one survives in the National Air and Space Museum.
• The 199 flights made by the three research air­planes contributed not only to aeronautical science, but provided many answers the United States needed to get to the Moon during Project Apollo.

Design and development:

• The X-15 was based on a concept study from Walter Dornberger for the National Advisory Committee for Aeronautics (NACA) for a hypersonic research aircraft. The requests for proposal (RFPs) were published on 30 December 1954 for the airframe and on 4 February 1955 for the rocket engine. The X-15 was built by two manufacturers: North American Aviation was contracted for the airframe in November 1955, and Reaction Motors was contracted for building the engines in 1956.
• Like many X-series aircraft, the X-15 was designed to be carried aloft and drop launched from under the wing of a B-52 mother ship. Air Force NB-52A, "The High and Mighty One" (serial 52-0003), and NB-52B, "The Challenger" (serial 52-0008, a.k.a. Balls 8) served as carrier planes for all X-15 flights. Release took place at an altitude of about 8.5 miles (13.7 km) and a speed of about 500 miles per hour (805 km/h). The X-15 fuselage was long and cylindrical, with rear fairings that flattened its appearance, and thick, dorsal and ventral wedge-fin stabilizers. Parts of the fuselage (the outer skin) were heat-resistant nickel alloy (Inconel-X 750). The retractable landing gear comprised a nose-wheel carriage and two rear skids. The skids did not extend beyond the ventral fin, which required the pilot to jettison the lower fin just before landing. The lower fin was recovered by parachute.
• The X-15 was operated under several different scenarios, including attachment to a launch aircraft, drop, main engine start and acceleration, ballistic flight into thin air/space, re-entry into thicker air, unpowered glide to landing, and direct landing without a main-engine start. The main rocket engine operated only for a relatively short part of the flight, but boosted the X-15 to its high speeds and altitudes. Without main engine thrust, the X-15′s instruments and control surfaces remained functional, but the aircraft could not maintain altitude.
• As the X-15 also had to be controlled in an environment where there was too little air for aerodynamic flight control surfaces, it had a reaction control system (RCS) that used rocket thrusters. There were two different X-15 pilot control setups: one used three joysticks, the other, one joystick.
• The X-15 type with multiple control sticks for the pilot placed a traditional rudder and stick between a left joystick that sent commands to the Reaction Control System, and a third joystick on the right used during high-G maneuvers to augment the center stick. In addition to pilot input, the X-15 "Stability Augmentation System" (SAS) sent inputs to the aerodynamic controls to help the pilot maintain attitude control. The Reaction Control System (RCS) could be operated in two modes – manual and automatic. The automatic mode used a feature called "Reaction Augmentation System" (RAS) that helped stabilize the vehicle at high altitude. The RAS was typically used for approximately three minutes of an X-15 flight before automatic power off.
• The alternative control setup used the MH-96 flight control system, which allowed one joystick in place of three and simplified pilot input. The MH-96 could automatically blend aerodynamic and rocket controls, depending on how effective each system was at controlling the aircraft.
• Among the many controls were the rocket engine throttle and a control for jettisoning the ventral tail fin. Other features of the cockpit included heated windows to prevent icing and a forward headrest for periods of high deceleration.
• The X-15 had an ejection seat designed to operate at speeds up to Mach 4 (4,480 km/h; 2,784 mph) and/or 120,000 feet (37 km) altitude, although it was never used during the program. In the event of ejection, the seat was designed to deploy fins, which were used until it reached a safer speed/altitude at which to deploy its main parachute. Pilots wore pressure suits, which could be pressurized with nitrogen gas. Above 35,000 feet (11 km) altitude, the cockpit was pressurized to 3.5 psi (0.24 atm) with nitrogen gas, while oxygen for breathing was fed separately to the pilot

Technical Data:

Types X-15 and dropping plane: Type: Serial Number Nbr Free Flights X-15-1 56-6670 81 free flights X-15-2 56-6671 31 free flights X-15A-2 - 22 free flights X-15-3 56-6672 65 free flights including the Fl.191 disaster NB-52A 52-003 retired in October 1969 NB-52B 52-008 retired in November 2004 Six of the X-15 pilots: Rushworth, McKay, Petersen, Walker, Armstrong & White.

Twelve Pilots: Name (order 1e flight): Agency Periode of flights Flights Crossfield Scott North American 08 Jun 1959 - 06 Dec 1960 14 Walker Joe USAF 25 Mar 1960 - 22 Aug 1963 25 White Robert USAF 13 Apr 1960 - 14 Dec 1962 16 Petersen Forrest USN 23 Sep 1960 - 10 Jan 1962 5 McKay John NASA 28 Oct 1960 - 08 Sep 1966 29 Rushworth Robert USAF 04 Nov 1960 - 01 Jul 1966 34 Armstrong Neil NASA 30 Nov 1960 - 26 Jul 1962 7 Engle Joe USAF 07 Oct 1963 - 14 Oct 1965 16 Thompson Milton NASA 29 Oct 1963 - 25 Aug 1965 14 Knight William (Pete?) USAF 30 Sep 1965 - 13 Sep 1968 16 Dana William (Bill?) NASA 04 Nov 1965 - 24 Oct 1968 16 Adams Michael USAF 06 Oct 1966 - 15 Nov 1967 7 White replaced selected pilot Iven Kincheloe, who died before the first X-15 flight.

The X-15 pulling away from its drop launch plane

X-15-2 after igniting rocket engine

Cockpit of an X-15.

X-15-3, with sealed ablative coating, external fuel tanks, and ramjet dummy test

Boeing NB-52A Stratofortress 52-003, The High and Mighty One, with North American Aviation X-15A-2 56-6671 mounted to the pylon under its right wing. (US. Air Force)

North American Aviation X-15A-2 56-6671 on Rogers Dry Lake. In addition to the lengthened fuselage and external tanks, the nose wheel strut is longer and the windshields have been changed to an oval shape. A wheeled dolly supports the aft end of the rocketplane. (NASA)

X-15 flight as an adventure:

• Every X-15 flight was an adventure, a high-speed dash that often pushed into unexplored realms of flight. Flights frequently set new records in speed and altitude, as well as records in less-known measurements such as airframe heating and dynamic pressure. With the XLR-99 rocket engine operating at full throttle pilots experienced a minimum of 2 g′s acceleration, building to over 4 g′s as fuel burned off. Pilot Milt Thompson commented that this was the only aircraft he′d flown that made him glad when the engine quit. Even then, with power off, the X-15 dropped about 9,000 feet per minute in a glide.
• Some X-15 flights proved to be high adventure. The X-15 itself was a very novel and complex system that operated in space as well as in the air. It pushed beyond known territory in hypersonic stability and control, and it explored reentry into the atmosphere from space. It was an experimental exercise in new technology, and risks were always present. Components could fail, systems could fail, and parts of the design could reveal what wasn′t previously known. Most flights ended safely, but the program did claim the life of one test pilot, Mike Adams, and seriously injured another, John McKay. The adventures decribed here involve everything from mishaps to historic milestones achieved on flawless flights.
• This section is intended to present many of the X-15 program′s adventures stories, not only because they tend to be great stories but also to give a sense of the scope and the reality of X-15 flight research. Some stories will include material from NASA′s flight logs, such as postflight reports and radio communication transcripts. These provide insight into the discipline of test flying, indications of the extensive preflight planning and postflight analysis that were part of the research program, and the scope of support needed for the program. Test pilots receive most of the attention because they were the ones directly involved in the X-15 cockpit, but their success and that of the research program as a whole belonged to a large group of people.

Major higts of the X-15 flights:

Notes:

• The X-15 program used a 3-digit ID code (x-x-x) to record flight information.
  
• The first digit represents the specific X-15 flown. 1 = X-15-1, 2 = X-15-2 or X-15-2A, 3 = X-15-3.
• The second digit represents the flight number of the specific X-15. This is for free flights only. Captive flights used a "C" in the second position. If a free flight resulted in an aborted launch, the second digit was represented by an "A".
• The third digit represents the total number of times that specific X-15 had been carried aloft by either NB-52. This number incremented for each captive-carry, abort, and actual release.

X-15 Fl.74 wreck.

X-15 Fl.74 crash.

External links:

• History.nasa.gov: (PDF) Hypersonics Before the Shuttle: A Concise History of the X-15 Research Airplane Flight log pages 118 - 122 (NASA SP-2000-4518, 2000)
• Drewexmachina.com: The First Reusable Spacecraft: The X-15 Flights Above the Karman Line
• Mach25media.com: The X-15 Rocket Plane
• Sierrafoot.org: Description
• Wikipedia: Description
• Military factory: Description
• Vintage space: Description
• This day in aviation: Cuddeback lake