History of the X-Plane Program

The U.S. X-Plane Program has evolved from being the first rocket-powered airplane to break the sound barrier (the X-1 on October 14, 1947) and included over 30 different major research designs, although not all were developed into flying prototypes. As the program progressed, other non-rocket-powered experimental aircraft were built and tested. These aircraft included: a range of vertical takeoff and horizontal landing vehicles; smaller, propeller-driven reconnaissance vehicles; and a series of unmanned missile testbeds of both single and multistage designs. Although the program grew to include conventional propeller-driven aircraft, all designs had in common the aspect of being highly valuable research tools for advancement of aerodynamics and astronautics.

Accomplishments of the X-Plane family have been many. The program included: (1) the first aircraft to break the sound barrier; (2) the first aircraft to use a variable-sweep-wing in flight; (3) the first to fly at altitudes in excess of 30,000, 60,000, and 90,000 m (100,000, 200,000 and 300,000 ft); (4) the first to use exotic alloy metals for primary structure; (5) the first to test gimbaled jet and rocket engines; (6) the first to use jet-thrust for launch and landing; (7) the first to fly three, four, five, and six times the speed of sound; (8) the first to test boundary-layer-airflow control theories over an entire wing at transonic speeds; (9) the first to successfully complete a 180 degree turn using a post-stall maneuver; and (10) the first missile to reach an intercontinental flight range.

The majority of testing for the X-Plane family has occurred at Edwards Air Force Base (formerly known as Muroc Army Airfield). Hosts within Edwards include the Air Force Flight Test Center and Dryden Flight Research Center. Other sites which have served as X-Plane testing sites include: Langley Research Center and Ames Research Center; various Government owned ships; White Sands Missile Range, New Mexico; Wright-Patterson Air Force Base, Ohio; Cape Canaveral Air Station, Florida; Pinecastle Air Force Base, Florida; Buffalo, New York; and the National Aviation Facilities Experimental Center in Atlantic City, New Jersey. Edwards has seen more X-Plane programs and test flights than any other similar facility in the U.S.

As with every research program testing prototype equipment, the X-Plane Program has not been without technical glitches and equipment failures. Since the beginning of the program's manned flight operations in 1946, approximately 15 major accidents and 4 fatalities (pilots) have been associated with manned vehicle tests. Three of these fatalities were from the X-2 Program, flown between 1952 and 1956, and the remaining fatality happened in 1967 during an X-15 research flight. Stringent range safety controls have resulted in no civilian property damage losses or fatalities being reported as a result of any X-Plane Program accident. Given the overwhelming number of test flights, the small number of accidents which resulted in loss of aircraft or life can be considered a remarkable program achievement. Table 1 provides key information about each plane tested in the X-Plane series of vehicles.

Another member of the X-Plane Program would be the X-33. As a reusable spaceplane, the X-33 continues the research line developed by various components of the X-Program, such as the X-10 which tested cruise missile components; the X-12, the Atlas B missile which tested one-and-one-half propulsion staging and obtained the first intercontinental flight distance for a U.S. missile; the X-15 which explored the problems of space and reentry at high speeds (Mach 6) and altitudes; the X-17 which explored high Mach effects on reentry vehicles; and the X-23A which was the first maneuvering lifting reentry vehicle. The X-17 was a multistage rocket design which transported various reentry vehicle configurations to very high altitudes to examine their reentry characteristics. The X-23A was launched by a modified intercontinental ballistic missile and utilized a lifting body design to glide back to earth. Information acquired from the X-23A was instrumental in later development of the Space Shuttle.

 

Table 1. Summary of the X-Plane Program.
Model
Manufacturer
No. of Vehicles Built
Years of Operation
No. of Flights
Primary Testing Facility
Research Goals
Program Achievements
No. of Major Accidents
Causes of Accidents
No. of Fatalities
Civilian Involvement
X-1
Bell Aircraft
3
1946-51
157
Edwards AFB
Investigate flight characteristics at greater than sonic velocities. Structural, physiological phenomena within transonic speed envelope
First Mach 1+ flight; Maximum altitude of 71,902 ft
1
Defueling Explosion
0
None
X-1A
Bell Aircraft
1
1953-55
25
Edwards AFB
Continue X-1 goals at higher speeds and altitudes
Obtained speed of Mach 2.44; Maximum altitude of 90,440 ft
1
Explosion during captive flight; vehicle jettisoned
0
None
X-1B
Bell Aircraft
1
1954-58
27
Edwards AFB
Exploratory aerodynamic heating tests; experimental reaction control system
First reaction controlled flight
0
Not applicable
Not applicable
Not applicable
X-1D
Bell Aircraft
1
1951
1
Edwards AFB
Continue X-1 goals at higher speeds and altitudes
No major milestones
1
Explosion during captive flight; vehicle jettisoned
0
None
X-1E
Bell Aircraft, Stanley Aircraft (wings)
1
1955-58
26
Edwards AFB
High-speed wing performance
Mach 2.24, altitude 73,458 ft; first flight with ventral fins
0
Not applicable
Not applicable
Not applicable
X-2
Bell Aircraft
2
1952-56
20
Edwards AFB
Swept-wing performance; higher speeds and altitude than X-1
New altitude record of 126,200 ft; new speed record of Mach 2.87
2
Gasket explosion destroys first X-2; second aircraft lost to inertial coupling
3
None
X-3
Douglas Aircraft
1
1954-56
20
Edwards AFB
High speed aerodynamic phenomenon; titanium construction; take off, land under its own power
Led to understanding of inertia coupling
0
Not applicable
Not applicable
Not applicable
X-4
Northrop Aircraft
2
1950-53
82
Edwards AFB
Test tailless, semi-tailless configuration at transonic speeds
Showed tailless craft not suited for transonic flight
0
Not applicable
Not applicable
Not applicable
X-5
Bell Aircraft
2
1952-55
133
Edwards AFB
Investigate aerodynamics of variable-seep-wing design
Successful sweep-wing operation
0
Not applicable
Not applicable
Not applicable
X-6
Convair Division, General Dynamics
1 shield-test aircraft (modified B-36H)
1955-57
47
Convair Testing Facility
Test feasibility of nuclear propulsion
Program terminated before prototypes constructed
0
Not applicable
Not applicable
Not applicable
X-7A, X-7A-3, X-7B, X-Q5 (unmanned)
Lockheed Missiles
61
1951-60
130
New Mexico
Test viability of ramjet engines for anti-aircraft missiles; modified to testing of powerplants
Obtained Mach 4.31, first air-breathing full-scale research aircraft designed as Mach 3 testbed
0
Not applicable
Not applicable
Not applicable
X-8A, X-8B, X-8C, X-8D Aerobees (unmanned)
Aerojet Engineering
108 (X-8 designation) 800+ (Aerobees)
1947-56
Unknown
White Sands, Holloman AFB
Upper air research, parachute recovery system
Peak altitude of 121 miles
0
Not applicable
Not applicable
Not applicable
X-9 (unmanned)
Bell Aircraft
31
1949-53
28
Holloman AFB
Test air-to-surface missiles; guidance systems, etc.
First chemical warhead test vehicle to test supersonic clusterable dispersion
9 unsuccessful flights
Servo system failures
0
Not applicable
X-10 (unmanned)
North American Aviation
13
1955-59
15
Edwards AFB
Testbed for cruise missile components
Established technology base for remote control; first Mach 2-capable target drone
3 unsuccessful flights
Communications disruption; miswiring; autopilot malfunction
0
Not applicable
X-11 (unmanned)
Convair Astronautics Division
8
1956-58
8
Cape Canaveral
Provide flight data for Atlas missile
First ICBM prototypes
0
Not applicable
Not applicable
Not applicable
X-12 (unmanned)
Convair Astronautics Division
5
1958
5
Cape Canaveral
Test 1½-propulsion-staging guidance system, nose reentry configuration
First intercontinental range mission of 6,325 miles
0
Not applicable
Not applicable
Not applicable
X-13
Ryan Aeronautical Company
2
1955-57
Unknown
Edwards AFB
Test pure-jet vertical takeoff and landing
First successful VTOL flight on jet thrust alone
0
Not applicable
Not applicable
Not applicable
X-14, X-14A, X-14B
Bell Aircraft
1
1957-81
Unknown
Moffet Field
Test VTOL technology
First VTOL aircraft using jet thrust diverter system for vertical lift
0
Not applicable
Not applicable
Not applicable
X-15, X-15A-2
North American Aviation
3
1959-68
199\
X-15 High Range (Wendover, UT, to Edwards AFB)
Explore problems of space and atmospheric flight at very high speeds and altitudes
First manned hypersonic flight vehicle; altitude of 354,200 ft obtained; Mach 6.33 reached
4
Mid-flight explosions (2); loss of control (1); collapsed landing gear (1)
1
Not applicable
X-16
Bell Aircraft
Cancelled
None
None
None
High-altitude, long-range reconnaissance aircraft
Not applicable
Not applicable
Not applicable
Not applicable
Not applicable
X-17 (unmanned)
Lockheed Missiles
26
1955-57
26
Holloman AFB
Explore reentry characteristics
High Mach effects on reentry vehicles
0
Not applicable
Not applicable
Not applicable
X-18
Hiller Aircraft
1
1959-61
20
Edwards AFB
Explore large VTOL vehicles
First tilt-wing usage for VTOL
0
Not applicable
Not applicable
Not applicable
X-19
Curtiss-Wright
2
1964-65
50
Caldwell; NAFEC, NJ
Test VTOL technology using radial lift
Dual-tandem tilt propeller use
1
Equipment failure
0
Not applicable
X-20
Boeing
Cancelled
None
None
None
Piloted orbital flight
Provided heat materials testing
Not applicable
Not applicable
Not applicable
Not applicable
X-21A
Northrop Corporation
2
1963-64
Unknown
Edwards AFB
Test full-scale boundary control on large aircraft
Proved Laminar Flow Control viable
0
Not applicable
Not applicable
Not applicable
X-22A
Bell Aerospace
2
1966-84
501
Bell, Calspan Test Facilities
Research dual-tandem-ducted propeller configuration; research V/STOL handling using variable stability system design
Ducted fan viability, advancement of VTOL technology
1
hydraulic system failure
0
None
X-23A (unmanned)
Martin Marietta
4
1966-67
3
Vandenberg AFB/Pacific Ocean
Test configurations, control systems, and ablative materials for hypersonic reentry vehicles
First maneuverable reentry vehicle
0
Not applicable
Not applicable
Not applicable
X-24A, X-24B
Martin Marietta
1
1969-75
64
Edwards AFB
Research of aerodynamics, flight characteristics of manned vehicle with FDL-7 configuration
Verified theoretical advantages of lifting body configuration for hypersonic transatmospheric aircraft
0
Not applicable
Not applicable
Not applicable
X-25, X-25A, X-25B
Bensen Aircraft
3
1968
 
Raleigh, NC
Test discretionary descent vehicle designs
Insight on pilot training
0
Not applicable
Not applicable
Not applicable
X-26A, X-26B
Schweizer Aircraft, Lockheed Missiles
6
1967-88
Unknown
Vietnam
Develop ultra-quiet surveillance aircraft
Use as training vehicle; contributions to stealth designs
3
Training exercises
0
Not applicable
X-27
Lockheed-California
Cancelled
None
None
None
Advanced, lightweight fighter
None
Not applicable
Not applicable
Not applicable
Not applicable
X-28A
George Pereira, Osprey Aircraft
1
1971
Unknown
Philadelphia Naval Base, PA
Explore usefulness of small, single-place seaplane for civil police patrol in Southeast Asia
Unique contribution as home-built aircraft in X-Plane program
0
Not applicable
Not applicable
Not applicable
X-29A
Grumman Aerospace
2
1984-90
Unknown
Edwards AFB
Test forward-swept wing design, advanced composites, other aerodynamic advances
First FSW aircraft to fly supersonically in level flight
0
Not applicable
Not applicable
Not applicable
X-30
None selected
None
(Cancelled)
None
None
None
Serve as testbed for sustained hypersonic speeds within atmosphere or as space vehicles for orbital payload delivery
Not applicable
Not applicable
Not applicable
Not applicable
Not applicable
X-31A
Rockwell International, Deutsche Aerospace
2
1990-95
523
Edwards AFB
Break "stall-barrier," examine angles of attack
180 degree turn post-stall maneuver
1
Failure of the pitot-static system: erroneous total pressure data
0
None
X-32
Boeing
 
 
 
 
Joint Strike Fighter
 
 
 
 
 
X-33
Lockheed-Martin Skunk Works
1
(Cancelled)
1999-2000
15
Edwards AFB
Develop reusable single-stage-to-orbit transportation vehicle
Not applicable
Not applicable
Not applicable
Not applicable
Not applicable
X-34
 
(Cancelled)
 
 
 
Reusable, unmanned suborbital spacecraft
 
 
 
Not applicable
 
X-35
Lockheed-Martin
2
2000-2001
66
Palmdale, CA
Edwards AFB
Joint Strike Fighter
Developed into the
F-35 Joint Strike
Fighter
 
 
 
 
X-36
McDonnell
Douglas
2
1997
31
 
Tailless fighter
agility research
 
 
 
Not applicable
 
X-37
Boeing
3
2006-
 
 
Unmanned orbital
test vehicle
Underwent orbital
test from 22 April
to 3 December 2010
 
 
 
 
X-38
Scaled Composites
(Cancelled)
2 prototypes
1999-2002
 
 
Develop technology for a prototype Crew Return Vehicle for the ISS
 
 
 
Not applicable
 
X-39
(unassigned)
 
 
 
 
 
 
 
 
 
 
 
X-40A
Boeing Phantom Works
1
1998-2001
 
 
Space maneuver vehicle
 
 
 
Not applicable
 
X-41
Air Force / DARPA / Sandia National Labs / NASA
 
 
 
 
Common Aero Vehicle / Hypersonic Technology Vehicle
Classified
 
 
 
 
X-42
 
 
 
 
 
Pop-up upper stage
Classified
 
 
 
 
X-43A
 
 
2001-2004
 
Dryden, Edwards AFB
Hyper-X, program to demonstrate hypersonic air-breathing scramjets
 
 
 
Not applicable
 
X-44
 
 
 
 
 
 
 
 
 
 
 
X-45A
Boeing
2
2002-06
 
 
Scaled down proof of concept demonstrator of an unmanned combat air vehicle
 
 
 
 
 
X-45B/C
Boeing
Cancelled
(3 planned)
 
 
 
Concept demonstrator of an unmanned combat air vehicle
 
 
 
 
 
X-46
Boeing
 
 
 
 
Naval unmanned combat air vehicle
 
 
 
 
 
X-47
Northrop
 
2003-
 
 
Concept demonstrator of an unmanned combat air vehicle
 
 
 
 
 
X-48
Boeing
 
 
 
 
Blended wing body concept
 
 
 
 
 
X-49
(unassigned)
 
 
 
 
 
 
 
 
 
 
X-50
Boeing
 
 
 
 
Technology demonstrator for the Dragonfly Canard Rotor/Wing
 
 
 
 
 
Key to Acronyms:

AFB = Air Force Base

FDL-7 = Flight Dynamics Laboratory-7 (a prototype test craft of the Air Force's Flight Dynamics Laboratory, a predecessor to the X-24B).

FSW = forward swept wing

ICBM = intercontinental ballistic missile

V/STOL = vertical/short takeoff and landing

VTOL = vertical takeoff and landing

horizontal rule

Times accessed: 5200

An American X-Plane History, from NASA.

(NASA receives credit for the information contained on this page)