X-15

North American X-15 rocket plane was an experimental aircraft project. It was the first aircraft to attain velocities of Mach 4, 5 and 6. The X-15 completed 199 missions between 1959 and 1968.

The X-15 was rocket-powered research aircraft. It was air launched from a B-52 aircraft. It had no landing gear, but landed on skis. It had reaction controls for attitude control in space. X-15 is composed of an internal structure of titanium and a skin surface of a chrome-nickel alloy known as Inconel X.

Development of the X-15 began in 1954, in a joint research program sponsored by the NACA (National Advisory Committee for Aeronautics – now NASA), the U.S. Air Force, the U.S. Navy and private industry. North American was selected as prime contractor on the project following a competition in which Bell, Douglas and Republic competed.

Specs:

Wingspan: 6.82 m
Length: 15.47 m
Height: 3.96 m
Weight: 5,670 kg empty
Powerplant: Reaction Motors XLR-99 rocket engine. Manufactured by Thiokol Chemical Corporation.

The X-15 had its first unpowered glide flight on 8 June, 1959. The first powered flight took place on 17 September, 1959. The final flight of the X-15 was performed on 24 October, 1968. The rocket plane set many first speed records in the Mach 4-6 range.

These included:

Mach 4.43 on 7 March, 1961
Mach 5.27 on 23 June, 1961
Mach 6.04 on 9 November, 1961
Mach 6.7 on 3 October, 1967.

It also set an altitude record of 354,200 feet (67 miles) on 22 August, 1963. Data was used to study hypersonic air flow, aerodynamic heating, control and stability at hypersonic speeds.

Three X-15 research aircraft were built and flown:

1. X-15-1 (serial number 56-6670) is located at the National Air and Space Museum, Washington DC.

2. X-15A-2 (serial number 56-6671) is at the United States Air Force Museum, Wright-Patterson AFB, Ohio. It was the fastest X-15 flown.

3. X-15-3 (serial number 56-6672) crashed on 15 November 1967 during atmospheric re-entry, resulting in the death of Michael J. Adams. Parts of the X-15-3 are on display at the Air Force Flight Test Center Museum at Edwards AFB and the San Diego Aerospace Museum, San Diego, California. The experimental rocket plane featured an advanced cockpit display panel and a special adaptive control system.

A total of 199 research flights were completed. The twelve X-15 Pilots were: 

1.  Michael J. Adams – U.S. Air Force, 7 flights.
2.  Neil Armstrong – NASA, 7 flights. He reached an altitude of 207,500 feet in the X-15-3 and a speed of Mach 5.74 (3,989 mph) in the X-15-1.
3.  A. Scott Crossfield – North American Aviation, 14 flights.
4.  William H. Dana – NASA, 16 flights.
5.  Joe H. Engle – U.S. Air Force, 16 flights.
6.  William J. Knight – U.S. Air Force, 16 flights.
7.  John B. McKay – NASA, 29 flights.
8.  Forrest S. Petersen – U.S. Air Force, 5 flights.
9.  Robert A. Rushworth – U.S. Air Force, 34 flights.
10. Milton O. Thompson – NASA, 14 flights.
11. Joseph A. Walker – NASA, 25 flights.
12. Robert M. White – U.S. Air Force, 16 flights.

There were plans to use the X-15 as a spaceplane to be launched at the top of a rocket, however it was not fulfilled. Much of what was learned on the X-15 was applied to the Space Shuttle.

Books

Hypersonic: The Story of the North American X-15
by Dennis Jenkins, Tony Landis, William H. Dana
from Amazon.com, Amazon.co.uk, Amazon.ca

At the Edge of Space: The X-15 Flight Program
by Milton O. Thompson, Neil A. Armstrong
from Amazon.com, Amazon.co.uk, Amazon.ca

X-15 Links:

NASA Armstrong Fact Sheet: X-15 Hypersonic Research Program

Genesis of the X-15 Rocket Plane | Popular Science

NASA Dryden X-15 Photo Collection – Armstrong Flight Research Center

X-15 – Hypersonic Research at the Edge of Space – NASA History

X-15A: astronautix