Jenkins Dennis R. - American X-Vehicles An Inventory-X-1 to X-50 (digital edition)

American X-Vehicles: An Inventory—X-1 to X-50

Dennis R. Jenkins, Tony Landis et Jay Miller

(NASA Monograph in Aerospace History No. 31, 2003) :

 
PDF download
This book provides a comprehensive and systematic catalogue of American experimental aircraft (designated by the ‘X’ nomenclature) from the X-1 to X-50 series, as well as related projects such as wing-body aircraft (e.g. HL-10, M2-F1) and variants of the Douglas D-558. The book forms part of the Centennial of Flight (2003) and aims to document the technological evolution, challenges and major contributions of these programmes to aeronautics and aerospace.
Authors:
-Dennis R. Jenkins: Aerospace historian, specialist in the X programmes (notably the X-15).
-Tony Landis: Archivist and photographer for NASA, contributor to historical documentation.
-Jay Miller: Expert on experimental aircraft, author of ‘The X-Planes: X-1 to X-45’.
The book is organised as a detailed catalogue, featuring:
- An introduction explaining the historical context:
The ‘X’ programmes began after the Second World War to explore unprecedented flight conditions (speed, altitude, aerodynamic configurations).
Contrary to popular belief, not all X-vehicles were designed for high speed (e.g. the Bensen X-25 did not exceed 137 km/h).
Some projects were prototypes (e.g. the X-11/X-12 for the Atlas missile), a practice that was criticised but is part of aviation history.
- Technical specifications for each aircraft (X-1 to X-50): Each entry includes:
Manufacturer (e.g. Bell, Lockheed, Northrop).
Key dates: First flight, last flight, number of flights.
Performance: Maximum speed (in Mach or mph), altitude, records.
Sponsors (USAF, NACA/NASA, US Navy, etc.).
Technological innovations and contributions to aeronautics.
Fate (e.g. on display in museums, destroyed, cancelled).
Photos and diagrams (from NASA archives, the authors’ collections, or the manufacturers).
Notable examples:
Aircraft Innovation / Record Impact 
Bell X-1 First supersonic flight (Mach 1.06, 1947, Chuck Yeager) Paved the way for supersonic fighter aircraft.
 
North American X-15 Hypersonic (Mach 6.72, 108 km altitude) Paved the way for space programmes (e.g. the Space Shuttle). 
Bell X-5 Variable-geometry wings (inspired by the Messerschmitt P.1101) Forerunner to aircraft such as the F-111 and the B-1 Lancer.
 
Lockheed X-7 Statorjet (Mach 4.31) Research into high-speed propulsion. 
Martin Marietta X-24B Lifting body (controlled landing without wings) Influenced the design of the space shuttle. 
Boeing X-37 Reusable space drone Forerunner of autonomous systems in orbit.
 
Supplementary chapters:
Lifting Bodies: Projects such as the HL-10 or M2-F1, tested for atmospheric re-entry.
Douglas D-558: Transonic and supersonic research aircraft (e.g. D-558-II Skyrocket).
Appendices: Bibliography, index, and further reading.
🔍 Key points and analysis
Diversity of missions:
Speed (from subsonic to Mach 6+ with the X-15).
Altitude (up to 108 km for the X-15, the edge of space).
Aerodynamic configurations (delta wings, variable geometry, tailless).
Propulsion (jet engines, ramjets, rockets, nuclear propulsion for the X-6).
Stability and control (e.g. study of inertial coupling following the X-2 accident).
The X-vehicles explored:
Historical context: 
Combat aircraft (F-15, F-16, SR-71).
Space shuttles (e.g. the wing design of the X-24B).
Modern drones (X-37, X-47).
Cold War: Many projects (e.g. X-15, X-20 Dyna-Soar) were linked to the space race or missiles.
Institutional collaboration: Central role played by the NACA (which became NASA in 1958), the USAF, and the US Navy.
Legacy: Data from the X-vehicles directly influenced:
Challenges and failures:
Technical problems: E.g. the X-3 Stiletto (speed limited by its engines), the X-6 (cancelled for nuclear safety reasons).
Fatal accidents: E.g.: X-2 (1956, Milburn Apt killed after setting a speed record), X-15 (1 accident in 1962).
Cancellations: Projects such as the X-20 Dyna-Soar (manned spaceplane) or the X-30 NASP (hypersonic shuttle) were not completed.
Evolution of the “X” designation:
Originally reserved for fundamental research, the designation has sometimes been used for operational prototypes (e.g. X-32/X-35 for the Joint Strike Fighter programme).
The authors point out that this practice, although criticised, has historical precedents (e.g. X-11/X-12 for the Atlas missile).
Field Key advances Iconic aircraft 
Supersonic Breaking the sound barrier, transonic aerodynamics. X-1, X-1E, X-2 
Hypersonic Flight at Mach 6+, heat-resistant materials. X-15, X-43
 
Control and stability Study of inertial coupling phenomena, fly-by-wire controls. X-2, X-15 
Propulsion Ramjets, liquid-propellant rockets, nuclear propulsion (X-6). X-7, X-8, X-15
 
Configurations Variable-geometry wings, flying wings, unmanned aerial vehicles. X-5, X-24B, X-37 
Space technologies Atmospheric re-entry, thermal protection. X-15, X-24B, X-38