| Designation | Official, Popular Name(s) | Manufacturer | 1st Flight or Appearance | Role(s)/Notes |
X-1 Skyrocket Bell 1948 experimental 1st supersonic aircraft - redes.
S-1
X-2 Transonic Bell 1948 experimental supersonic rocket - 1st aircraft
to fly > Mach 3 - redes. S-2
X-3 Stiletto Douglas 1948 experimental supersonic research
aircraft- redes. S-3
X-4 Bantam Northrop 1948 experimental high-speed tailless research
aircraft- redes. S-4
X-5 Variable-Sweep Bell 1948 experimental - 1st American swing-wing jet -
redes. S-5
X-6 Crusader, Convair 1955 nuclear propulsion testbed - 1 modified [N]B-36H
Peacemaker, Aluminum Overcast, Magnesium Overcast
X-7 The Flying Stovepipe Lockheed 1951 super/hypersonic ramjet testbed - "pilotless
missile"
X-8 Aerobee Aerojet 1947 high-altitude research missile
X-9 Shrike Bell 1950? simplified version of the GAM-63 ASM
X-10 North Amer. 1955 testbed SM-64 Navaho missile
X-11 Atlas A Convair 1957 ballistic missile evaluation B-65
X-12 Atlas B/C/D Convair 1958 testbed B-65/SM-65 Atlas
X-13 Vertijet Ryan 1955 experimental jet VATOL
X-14 Bell 1956 experimental VTOL - 2 jets in nose
X-15 Hypersonic North Amer. 1959 manned rocket - flew > 4000 mph & higher than
500,000 feet
X-16 Bell 1955 experimental - competitor U-2 -cancelled
X-17 Lockheed 1956 experimental rocket
X-18 Tilt Wing Hiller 1959 experimental tilt-wing convertiplane -
modified C-122
X-19 Tilt Prop Cur.-Wr. 1963 experimental 4 tilt-prop VTOL
X-20 Dyna-Soar, Dinosaur Boeing 1965 experimental hypersonic lifting body
X-21 Laminar Flow Northrop 1963 experimental modified Douglas WB-66 -laminar flow
research with 3.2 million slots & 815,000
holes on wing
X-22 Tilt Duct Bell 1965 experimental 4-engined swiveling engined VTOL
X-23 Prime Martin 1966 experimental hypersonic lifting body
X-24A Flying Potato Martin 1969 experimental lifting body
X-24B Flying Flatiron Martin 1973 X-24B - modified, more angular X-24A
X-25 Gyro-glider, DDV Bensen 1978 experimental rescue mini-helicopter
X-26A Frigate Schweizer 1972? exper. USN sailplane civ. SGS 2-32
X-26B Q-Star Lockheed 1968 modified QT-2 - exper. trainer
X-27 Lancer Lockheed 1971 exper. - proposed modified F-104
X-28 AirSkimmer, Osprey I Pereira 1970 exper. light patrol flying boat
X-29 Polecat Grumman 1984 experimental FSW demonstrator
X-30 NASP Rockwell 1989 experimental hypersonic low-orbit transport
X-31 EFM Rock./MBB 1987 experimental highly maneuverable fighter
X-32 Boeing 1996 full-scale tech. demon. (FSTD) of JSF (Joint
Strike Fighter) - competitor of X-35
X-33 Lockheed 1996 demonstrator of SSTO (Single Stage To Orbit) RLV
Martin (Reuseable Launch Vehicle) - lifting body configuration
X-34 Orbital 1995? NASA test vehicle for unmanned reusable
Sciences space launcher
X-35 Lockheed 1996 FSTD of JSF - competitor of X-32
Martin
X-36 NASA/McDD 1996 stealthy, highly maneuverable 27% scale drone of
proposed manned fighter - tailless, cranked-arrow wing
X-37 Future-X Boeing 1998 proposed exper. flight vehicle - test
earth-to-orbit and orbit-to-orbit reusable
space trans. technologies
X-38 Lifeboat Scaled Comp.1996 experimental CRV (Crew Return Vehicle) - lifting body
X-39 2000? presently unassigned; reserved for USAF Research Lab.,
originally used for unmanned subscale demon. for
Future Aircraft Technology Enhancements (FATE) to fighters,
but funding transferred to DARPA
X-40 Boeing 1998 USAF SMV (Space Maneuver Vehicle) program - used
for drop tests evaluating "autonomous approach and
landing systems" from H-60; B-52 drops planned
X-41 USAF - classified, but supposedly "an exper. maneuverable
reentry vehicle carrying...payloads through a suborbital
trajectory, and reentering and dispersing the payload
in the atmosphere"
X-42 classified - "exper. expendable liquid rocket motor
upper stage designed to boost 2000-4000 lb. payloads
into orbit
X-43 Hyper-X several Mach 7-10 scramjet-powered test vehicles
boosted to test speed and altitude by Pegasus boosters
launched by B-52s - evalation of SSTO tech.
X-44 Manta 2000 designation reserved for possible NASA
full-scale manned tailless flight control demonstrator
X-44 Lockheed 200? Highly modified F-22A by removing tail, installing
delta wings, pitch/yaw low observable nozzles,
pneumatic vortex control, and mechanical
and fluidic thrust vectoring nozzles;
designation in conflict with X-44 Manta
X-45 Boeing 2000 UCAV demonstrator
X-46 Boeing 2001 "low-cost approach" to USN's planned naval unmanned
combat air vehicle (UCAV-N) technology demonstration - F/A-18 to be
used as "manned surrogate"
X-47 Pegasus Northrop 2001 demonstration UCAV (Unmanned Combat Aerial Vehicle)
Grumman Integrated under development for US Navy/DARPA
Systems Sector
X-48 Boeing/ 2001 blended-wing body slow-speed flying wing demonstrator
NASA
X-49? possibly skipped at Boeing's request for X-50?
X-50 Dragonfly DARPA/ 200? CRW (canard rotor/wing) exper. unmanned demonstration vehicle;
Boeing rotor converts to fixed wing
XS Cox-Klemin 1927 USN/USMC scout flying boat biplane
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