C. A Short Summary of the X-Series Aircraft

from the Virginia Tech Aircraft Design Information Sources pages

 
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-47B Northrop Grum. N   4 Feb. 2011 Highly modified version of the X-47A.

X-48A NASA/Boeing    N  20 July 2007 Low speed UAV of the Blended Wing Body concept

X-49A Piasecki       Y  29 June 2007 High Speed Compound helicopter

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.

X-56A                 N   July 2013  Lockheed Martin modular UAV. HALE mission. Intended
                                     to research active flutter suppression and gust-load
                                     alleviation technology. A flying wing with multiple
                                     sets of wings.
                                     
X-57 ESA Aero         Y   2019?      Electric Powered, based on the Tecnam P2006T

X-59 Lockheed         Y   2021       QueSST Low Boom Supersonic Demonstrator

X-60A GenerationOrbit N   2019?      Hypersonic Flight Research Vehicle
      Launch Services                Launched from Gulfstream III, Mach 5-8
         
X-#  Builder      Manned 1st Flt     Purpose

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