https://en.wikipedia.org/wiki/North_American_X-15
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 manned, powered aircraft,
set in October 1967 when William J. Knight flew Mach 6.72 at 102,100 feet
(31,120 m), a speed of 4,520 miles per hour (7,274 km/h) (2020.278 meters per
second), has remained unchallenged as of October 2017.
During the X-15 program, 13 flights by eight pilots 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
astronaut wings immediately, while the civilian pilots were eventually awarded
NASA astronaut wings in 2005, 35 years after the last X-15 flight. The only Navy
pilot in the X-15 program never took the aircraft above the requisite 50 mile
altitude and so as a result, never earned astronaut wings.
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 NASA B-52 mother ship. Air Force NB-52A, "The
High and Mighty One" (serial 52-0003, a.k.a. Balls Three), 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 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.
Role
Experimental high-speed rocket-powered research aircraft
Manufacturer
North American Aviation
First flight
8 June 1959
Introduction
17 September 1959
Retired
December 1968
Primary users
United States Air Force
NASA
Number built
3
The initial 24 powered flights used two Reaction Motors XLR11 liquid-propellant
rocket engines, enhanced to provide a total of 16,000 pounds-force (71 kN) of
thrust as compared to the 6,000 pounds-force (27 kN) that a single XLR11
provided in 1947 to make the Bell X-1 the first aircraft to fly faster than the
speed of sound. The XLR11 used ethyl alcohol and liquid oxygen.
By November 1960, Reaction Motors was able to deliver the XLR99 rocket engine,
generating 57,000 pounds-force (250 kN) of thrust. The remaining 175 flights of
the X-15 used XLR99 engines, in a single engine configuration. The XLR99 used
anhydrous ammonia and liquid oxygen as propellant, and hydrogen peroxide to
drive the high-speed turbopump that delivered propellants to the engine. It
could burn 15,000 pounds (6,804 kg) of propellant in 80 seconds.
The first X-15 flight was a captive-carry unpowered test by Scott Crossfield, on
8 June 1959. Crossfield also piloted the first powered flight, on 17 September
1959, and his first flight with the XLR-99 rocket engine on 15 November 1960.
Twelve test pilots flew the X-15. Among these were Neil Armstrong, later a NASA
astronaut and first man to set foot on the Moon, and Joe Engle, later a
commander of NASA Space Shuttle test flights.
In a 1962 proposal, NASA considered using the B-52/X-15 as a launch platform for
a Blue Scout rocket to place satellites weighing up to 150 pounds (68 kg) into
orbit.
In July and August 1963, pilot Joseph A. Walker exceeded 100 km in altitude,
joining NASA astronauts and Soviet cosmonauts as the first human beings to cross
that line on their way to outer space. The USAF awarded astronaut wings to
anyone achieving an altitude of 50 miles (80 km), while the FAI set the limit of
space at 100 kilometers (62.1 mi).
On 15 November 1967, U.S. Air Force test pilot Major Michael J. Adams was killed
during X-15 Flight 191 when the X-15-3, AF Ser. No. 56-6672, entered a
hypersonic spin while descending, then oscillated violently as aerodynamic
forces increased after re-entry. As his aircraft's flight control system
operated the control surfaces to their limits, acceleration built to 15 g0 (150
m/s2) vertical and 8.0 g0 (78 m/s2) lateral. The airframe broke apart at 60,000
feet (18 km) altitude, scattering the X-15's wreckage for 50 square miles (130
km2). On 8 May 2004, a monument was erected at the cockpit's locale, near
Randsburg, California. Major Adams was posthumously awarded Air Force astronaut
wings for his final flight in X-15-3, which had reached an altitude of 50.4
miles (81.1 km). In 1991, his name was added to the Astronaut Memorial.
The second X-15, X-15-2, was rebuilt after a landing accident. It was lengthened
by 2.4 feet (73 cm), had a pair of auxiliary fuel tanks attached beneath its
fuselage and wings, and a complete heat-resistant ablative coating was added.
The plane was renamed the X-15A-2, and took flight for the first time on 28 June
1964. It reached its maximum speed of 4,520 miles per hour (7,274 km/h) in
October 1967 with pilot William "Pete" Knight of the U.S. Air Force in control.
Specifications
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)
70,400 lbf at 30 km (313 kN)
Performance
Maximum speed: 4,520 mph (7,274 km/h)
Range: 280 mi (450 km)
Service ceiling: 67 mi (108 km, 354,330 ft)
Rate of climb: 60,000 ft/min (18,288 m/min)
Wing loading: 170 lb/ft2 (829 kg/m2)
Thrust/weight: 2.07
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