North American X-15

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; 2,021 m/s), has
remained unchallenged as of June 2018.

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 thus never earned astronaut wings.

The X-15 was the product of developmental research and changes were made to
various systems over the course of the program and between the different models.
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.

Because 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 X-15 had a thick wedge tail to enable it to fly in a steady manner at
hypersonic speeds. This produced a significant amount of drag at lower speeds;
the blunt end at the rear of the X-15 could produce as much drag as an entire
F-104 Starfighter.

"A wedge shape was used because it is more effective than the conventional tail
as a stabilizing surface at hypersonic speeds. A vertical-tail area equal to 60
percent of the wing area was required to give the X-15 adequate directional
stability.

—?Wendell H. Stillwell, X-15 Research Results (SP-60)


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 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.

A 200th flight over Nevada was first scheduled for 21 November 1968, to be flown
by William "Pete" Knight. Numerous technical problems and outbreaks of bad
weather delayed this proposed flight six times, and it was permanently canceled
on 20 December 1968. This X-15 was detached from the B-52 and then put into
indefinite storage. The aircraft was later donated to the Air Force Museum at
Wright-Patterson Air Force Base for display.

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)
Powerplant: 1 × Reaction Motors XLR99-RM-2 liquid propellant rocket engine,
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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