For more details and pictures of the planes, see ‘The X-Planes,’ by Jay Miller, in Code One, the Lockheed Martin Company Magazine.
X-# Builder Manned 1st Flt Purpose
X-1. Bell Y Jan. 1946 Rocket powered plane, developed to investigate
supersonic flight regime. It broke the sound
barrier in 1947 with Chuck Yeager piloting.
X-2. Bell Y Aug. 1955 Rocket powered plane, 1st Mach 3 flight,
this was a swept wing X-1.
X-3. Douglas Y Oct. 1952 Jet powered supersonic plane (couldn't fly
supersonic in level flight) Stiletto
X-4. Northrop Y Dec. 1948 Jet powered tailless transonic airplane
X-5. Bell Y June 1951 First successful variable sweep airplane
X-6. Convair Y - This aircraft was to have been nuclear powered
(never built) NB-36 did fly with a reactor
X-7. Lockheed N Apr. 1951 Supersonic/Hypersonic ramjet testbed missile.
X-8. Aerojet N Nov. 1947 Upper atmosphere research rocket
(became the "Aerobee")
X-9. Bell N May 1950 Missile test bed (Mach 2 aerodynamics), results
used for the development of the "Rascal"
X-10. North American N Oct. 1953 2nd phase of the R&D for the "Navaho" - later
became target drones.
X-11. Convair N July 1948 Rocket to test ICBM concepts (smaller than V-2's),
precursor to the Atlas missile program.
X-12. Convair N - A jet powered version of the X-11
(program canceled).
X-13. Ryan Y Dec. 1956 A pure jet "tailsitter" VTOL aircraft
X-14. Bell Y Feb. 1957 A deflected jet VTOL aircraft
X-15. North American Y June 1959 Rocket powered hypersonic research airplane
X-16. Bell Y - Proposed high altitude photo-recon plane
(X designation a coverup; lost competition
to Lockheed U-2).
X-17. Lockheed N Sept 1956 3 stage solid propellant rocket built for re-entry
testing of warhead configurations.
X-18. Hiller Y Nov. 1959 A tilt-wing VTOL aircraft (never made the
transition from hover to flight or vice versa)
X-19. Curtis-Wright Y Oct. 1963 A tilt-propeller VTOL aircraft (plane had seats
for 4 passengers)
X-20. Boeing Y - A manned-recoverable orbital vehicle concept;
the "Dyna-Soar" (program canceled)
X-21. Northrop Y Apr. 1963 Laminar flow control demonstration aircraft
X-22. Bell Y Mar. 1966 A tilt-ducted propeller V/STOL aircraft
(wing tips also rotated)
X-23. Martin N 1967 Unmanned lifting body concept demonstrator
(unpowered).
X-24. Martin Y Apr. 1969 Rocket powered manned lifting body
X-25. Bensen Y 1967 Government designation for the Bensen gyrocopter
X-26. Lockheed Y July 1967 Quiet-Recon; the Lockheed Q-Star
X-27. Lockheed Y - High performance fighter engine test bed
(Lockheed's "Lancer"), program canceled
X-28. Osprey Y Aug. 1970 Government designation of the homebuilt
"Osprey 1"; a small single engine flying boat.
X-29. Grumman Y 14 Dec. 1984 Forward swept wing demonstrator
X-30. Rockwell/etc. Y - NASP prototype (never built)
X-31. Rockwell/MBB Y 11 Oct. 1990 Post-Stall Maneuver demonstrator
X-32A/B Boeing Y 28 Sep. 2000 This is the Boeing JSF
(Joint Strike Fighter) concept vehicle
X-33 Lockheed N next generation reusable launch system
Martin awarded in 1996 - cancelled in 2001
X-34. Orbital Sci. N new small payload launch system
Phase 1, Mar. 1995 - cancelled in 2001
X-35A Lockheed Y 24 Oct. 2000 This is the Lockheed Martin JSF
Martin (Joint Strike Fighter) concept vehicle
There are A, B and C versions
This was the winner. The JSF will be the F-35.
X-36 McDonnell N 17 May 1997 Tailless (vertical) Aircraft Research UAV
(now Boeing)
X-37 Boeing/ N 7 Apr. 2006 Orbital Vehicle, originally to be launched
NASA/USAF inside the shuttle cargo bay, with autonomous
landing after space maneuvering and advanced
technology demonstrations (Av Wk, Aug. 9. 1999)
Became a DAROA project in 2004. First flight was
a drop from the Scaled Composites White Knight.
X-37B Boeing/ N Apr. 22 2010 Announced as a development of the X-37. This is
DARPA/USAF known as an Orbital Test Vehicle (OTV). It was
launched on an Atlas V from Cape Canaveral.
It made an autonomous landing Dec. 3, 2010 at
Vandenberg Air Force Base, CA.
X-38 Scaled N 12 Mar. 1998 Experimental demonstrator for a
Composites Crew Return Vehicle, it is droppped
from a B-52 (X-24A derivative)
X-39 - reserved for USAF Research Lab,
Future Aircraft Technology Enhancements
(FATE) Program
X-40 Boeing N August 1998 actually the X-40A, the USAF's Space
Maneuver Vehicle, was dropped to validate
autonomous landing
X-41/42 Classified programs:
X-41: common aero vehicle,
experimental maneuverable re-entry vehicle
X-42: pop-up upper stage experimental rocket/motor
X-43 Microcraft/ N 2004 formerly the Hyper-X program, a
GASL a scramjet demonstrator vehicle
- 1st flt. failed on June 2, 2001 because the
Pegasus booster went off course and had to
be destroyed
- 2nd flt. Mar. 27, 2004 - Mach 7
- 3rd and final flight, Nov. 16, 2004
a Mach 10 flight (actually M was 9.6)
X-44 Lockheed Martin proposed vehicle controlled entirely
by thrust vectoring
X-45A Boeing N 22 May 2002 UCAV, rolled out Sept 27, 2000
at St. Louis. 1st flt: May 22, 2002
X-46A Boeing N Built by Boeing for the Navy. Includes
surveillance and operations from aircraft
carriers. (Aerospace America, Nov. 2001)
X-47A Northrop Grum. N 23 Feb. 2003 Autonomous UAV, a pure stealth wing concept
for the navy
X-48A NASA/Boeing N 20 July 2007 Low speed UAV of the Blended Wing Body concept
X-50A Boeing N 4 Dec 2003 The canard/rotor wing unmanned aircraft,
the Dragonfly. 1st flt was a hover
X-51A N 26 May 2010 A Scramjet-Waverider built by Boeing and
Pratt & Whitney. Got from Mach 4.73 to 5
after a 200 (planned 300) second engine run.
X-53 Y Nov. 2002 Active Aeroelastic Wing (AAW), An F-18
redesignated X-53 on Aug. 16, 2006
X-54 ? X-54A Assigned by DOD to Gulfstream Aerospace on
May 5, 2008. Described as a NASA supersonic
experimental aircraft to conduct flight research.
To be capable of generating relevant ground sonic
boom signatures to gather data in support of NASA
and a regulatory change process.
X-55A Y June 2009 Lockheed Martin Advanced Composite Cargo Aircraft,
a Fairchild-Dornier Do 328JET with a composite fuselage.
For further reading:
Dennis R. Jenkins, Tony Landis, and Jay Miller, American X-Vehicles, An Inventory-X-1 to X-50, Monographs in Aerospace History No. 31, NASA SP-2003-4531, June 2003, available from the NASA History Site.
Jay Miller, The X-Planes, Specialty Press, 1983 (more recent editions available).
Ben Guenther, Jay Miller, and Terri Panopalis, North American X-15/X-15A-2, Aerofax Datagraph 2.
-, Proceedings of the X-15 First Flight 30th Anniversary Celebration, NASA CP 3105, June 8, 1989, published: 1991.
Source for X-39 through X-43: Flight International, 6-12 Jan., 1999, and Code One, Vol. 16, No. 2, Second Quarter 2001
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direct comments and suggestions to W.H. Mason, whmason@vt.edu