REVISED: 2/25/03

MX and WS Numbers

Compiled by Steve Pace, Andreas Parsch, Dr Raymond L Puffer
and other personnel of the Air Force Flight Test Center History Office

In the 1940s, 1950s, and early 1960s the Army Air Forces (USAAF) Air Materiel Command (AMC) employed what were known as MX (Materiel, Experimental) numbers to identify its experiment projects. It also used MP (Materiel, Prototype) numbers to identify projects entered into their service test phase. This project numbering system carried over for a time after the Air Force (USAF) was established and its Air Research and Development Command (ARDC) replaced the USAAF's AMC. Follows are some known MX and MP project numbers and what they represented. After those are the Weapon System (WS) numbers.

After the USAF's ARDC was established the MX/MP numbering system fell by the wayside. In its place came the WS numbering system, whereby a project became a whole entity comprised of not only airframe but powerplant, radar system, armament and, indeed, every system on the air vehicle. For example, WS-100A represented every nut and bolt of the Boeing B-47 Stratojet.

Code and Project Names

Archangel Lockheed A-1 and A-2
Have Blue Lockheed Experimental
    Survivable Testbed (XST); also
    Northrop XST entry
Oxcart Lockheed A-12
Senior Ice
Senior Peg
Senior Trend Lockheed F-117A
Tacit Blue Northrop Battlefield
    Surveillance Aircraft, Experimental
Tacit Rainbow
Tagboard Lockheed D-21


A Attack
AAM Air-to-Air Missile
AD Air Defense
ADM Air-Launched Decoy Missile
AF Air Force
AGM Air-to-ground Missile
AICBM Advanced Intercontinental
    Ballistic Missile
AIM Air-Intercept Missile
ALBM Air-Launched Ballistic Missile
ALCM Air-Launched Cruise Missile
AMC Air Materiel Command
AP Army/Air Force Project (used by
    Republic Aviation Corp or RAC)
ARDC Air Research & Development
ASM Air-to-Surface Missile
ATB Advanced Technology Bomber
ATF Advanced Tactical Fighter
ATO Assisted Take-off
ATSC Air Technical Service Command
AUM Air-to-Underwater Missile
    (also Hydrobomb)
AV Attack VTOL
B Bomber
BDM Bomber Defense Missile
BOMARC Boeing/Michigan
    Aeronautical Research Center
BOMI Bomber Missile
C Cargo Transport
CIM Coffin-launched Interceptor
CPB Chemically-Powered Bomber
D Drone
F Fighter
F/A Fighter/Attack
FB Fighter Bomber
FFAR Folding-Fin Aircraft Rocket
FFR Folding-Fin Rocket
FV Fighter VTOL
GAM Guided Aircraft Missile
GAPA - GAR Guided Aircraft Rocket
GB Glide Bomb, Guided Bomb
H Helicopter
ICBM Intercontinental Ballistic Missile
IRBM Intermediate-Range Ballistic
JB Jet Bomb
JPL Jet Propulsion Laboratory
KC Tanker/Cargo Transport
L Liaison (cargo transport,
    observation, recon, troop
    support, etc)
M Missile
MP Materiel, Prototype
MX Materiel, Experimental
NORAD North American Air Defense
NPB Nuclear-Powered Bomber
OS Operational Support
O - Observation
P Pursuit
Q Drone
R Reconnaissance
RATO Rocket-Assisted Take-Off
RB Reconnaissance Bomber
RF Reconnaissance Fighter
RQ Reconnaissance Drone
RS Reconnaissance Strike/
    Reconnaissance System/
    Research Support
S - Strategic
SAM Surface-to-Air Missile
SM Strategic Missile
SR Strategic Reconnaissance
SS Supporting Systems
STOVL Short Take-Off and Vertical
T Trainer
TB Trainer Bomber
TF Trainer Fighter
TFX Tactical Fighter, Experimental
TM Tactical Missile
TW Tactical War
U Utility
UAV Unmanned Aerial Vehicle
UCAV Unmanned Combat Aerial
VTOL Vertical Take-Off and
W Weather
WB Weather Bomber
WS Weapon System
X Experimental Prototype/
    Dedicated Research
XA Experimental Attack
XB Experimental Bomber
XF Experimental Fighter
XP Experimental Pursuit
Y Service Test
YA Service Test Attack
YB Service Test Bomber
YF Service Test Fighter
YP Service Test Pursuit

MX Numbers

In the early 1940s the Army Air Corps' Air Materiel Command (USAAC/AMC) established a series of project numbers for various aircraft, powerplants, and related equipment. These numbers, actually project designations, began with either MP (Materiel, Prototype) or MX (Materiel, Experimental) prefixes.

MX/MP Numbers

MX-1 Bell 16 XP-52
MX-6 Lockheed XP-38A
MX-8 Norden bomb sight (site?)
MX-10 Development and test of special camouflage paint for aircraft
MX-12 Consolidated-Vultee XP-54 "Swoose" (also "Swoose Goose")
MP-13 Northrop N-9 YB-35
MX-14 Northrop N-2 XP-56 "Black Bullet"
MP-48 Northrop N-51 YB-35B
MX-51 Northrop 9 XB-49 (later YB-49)
MX-53 XBQ-1 radio-controlled, twin-engine, tv-equipped aircraft used as
    an unmanned bombardment drone
MX-53 XBQ-2A (same as previous)
MX-53 XBQ-5 (design only)
MX-53 XBQ-6 (design only)
MX-53A XBQ-3 (same as XBQ-1 and XBQ-2A)
MP-55 Northrop N-41 and N-52 YRB-49A Recon
MP-56 Northrop N-50 YB-49
MP-80 Northrop N-35 F-89A
MP-97 Northrop N-32 YC-125
MX-108 GB-4 controllable glide bomb (ATSC)
MX-117 Goodyear pressure suit
MX-121 Eurcope with RATO booster units
MX-127 McDonnell XP-67 "Moon Bat"
MP-131 Zero Length Launcher (ZELL); Northrop N-73
MX-133 YLR63-AF-1 ATO rocket unit
MX-140 Northrop N-9 XB-35 Flying Wing Bomber
MX-256 Sikorsky XR-5 helicopter
MX-264 XBQ-4 (same as MX-53/-53A; Navy equipment)
MX-272 Bell XP-77 lightweight fighter
MX-324 Northrop N-12: Flying mockup of proposed XP-79 rocket-
    powered flying wing interceptor; unofficially named "Rocket Wing"
MX-334 Northrop N-12 Glider, unpowered
MX-363 Air-to-underwater Hydrobomb (JPL)
MX-365 Northrop N-14 XP-79B "Flying Ram"
MX-392 Douglas XB-42 "Mixmaster"
MX-397 Bell 27 XP-59A
MX-409 Lockheed XP-80 Lulu-Belle
MX-409B XP-80 Flight-test
MX-469 Project Silverplate (AMC); special Martin-built B-29s to
    carry Fat Man and Little Boy type atomic bombs; 65 built
MX-472 McDonnell 27D XF-85 (Parasite Fighter)
MX-475 Douglas D- XB-43
MX-480 Consolidated-Vultee XP-81 "Silver Bullet" Flight Test
MX-485 North American XP-82
MX-494 GB-9 ground-skimming glide bomb (ATSC)
MX-524 Bell 44 XS-1 (later X-1)
MX-527 Ramjets for AMC Propulsion Laboratory (ATSC)
MX-536 Flight-testing of tactical aircraft via remote control (Bell
    contract using a Grumman F7F)
MX-541 "Abusive" use of war-weary aircraft as guided missiles
MX-543 Northrop N-16 JB-1
MX-543-1 Northrop N-16 JB-1B
MX-544 Northrop N-16 JB-10
MX-544 JB-2 Loon
MX-553 North American Charge Number NA-130 XB-45
MX-559 "Javaman" Use of A-2, A-3 and A-5 boats as radio-controlled
    anti-shipping missiles
MX-562 Northrop N-19 XT37-N-1 Turbodyne engine
MX-563 Northrop N-8 XP-61
MX-570 JB-3 Rocket-propelled two-stage, air-to-air pilotless aircraft
    with a 500# high-explosive warhead
MX-575 Hughes H- XF-11 high-speed photographic-recon
MX-578 Republic model AP- XP-84
MX-582 Curtiss CW-/XA-43 attack aircraft (later XP-/XF-87)
MX-584 Boeing B-450-3-3 XB-47
MX-585 Consolidated-Vultee XB-46
MX-589 Martin M-223 XB-48
MX-590 VB-2 (Azon), 2,000# bomb, radio-controlled in azimuth only
MX-591 VB-3 (Razon), 1,000# bomb, radio-controlled in range and azimuth
MX-592 VB-4 (Razon), 2,000# bomb, radio-controlled in range and azimuth
MX-595 JB-5, proposed air-to-surface, rocket-powered unguided and
    unmanned jet bomb aircraft
MX-600 JB-6, proposed air-to-surface, rocket-powered guided and unmanned
    jet bomb aircraft
MX-601 VB-10 (Roc), 1,000# radio-controlled, TV equipped, circular-wing,
    medium-angle bomb
MX-603 VB-12 (Roc), 1,000# light-seeking, circular wing, medium-angle bomb
MX-604 VB-11 (Roc), 1,000# heat-seeking, circular wing, medium-angle bomb
MX-605 JB-7, proposed long-range, turbojet-powered, surface-to-surface
    unmanned jet bomb aircraft
MX-606 Boeing "GAPA" rocket-powered, ground-to-air interceptor missile
    (GAPA Ground-to-Air Pilotless Aircraft)
MX-607 JB-4, 1,000# warhead, intermittent-jet, medium range surface-to-
    surface unmanned jet bomb aircraft
MX-611 Aeronca GB-5, GB-5A, 2,000# ship-seeking glide bomb
MX-612 Aeronca VB-6 (Felix), 1,000# heat-seeking bomb
MX-612-1 Aeronca GB-6, 2,000# heat-seeking glide bomb
MX-613 Aeronca GB-7, GB-7A, 2,000# radar-seeking (RHB) glide bomb
MX-614 Aeronca GB-11, 1,100# chemical spray glide bomb
MX-615 Aeronca GB-12, 2,000# light-seeking glide bomb
MX-616 Aeronca GB-14, 2,000# radar-seeking glide bomb
MX-618 Klassen GB-4, 2,000# radio-controlled, TV-equipped glide bomb
MX-619 Aeronca GB-13, 2,000# flare-seeking glide bomb
MX-623 Offner heat-seeker (infrared) for missile guidance
MX-630 Expendable XJ41 turbojet engine
MX-645 Aeronca GB-8, 2,000# radio-controlled, flare-carrying glide bomb
MX-653 Bell 44 X-1 (formerly MX-524, XS-1)
MX-656 Douglas D-XS-3 (later X-3) Stiletto
MX-671 A-1 fire control system
MX-673 North American Charge Number NA-140 XP-86t
MX-674 Bell VB-13 (later ASM-A-1) Tarzon, 12,000# bomb, radio-
    controlled in range and azimuth
MX-702A Design, etc. of XRF47-W-3
MX-716 Convair XB-53 (formerly XA-44)
MX-717 GB-15, 2,000# radar/television glide bomb
MX-721 Radioplane OQ-19 target drone
MX-743 Bell 52 XS-2 (later X-2); rocket-powered, sweptback flying surfaces,
    supersonic research
MX-754 K-1 and K-2 optical radar bombing and navigational systems
MX-758 Northrop N-20 XF-15A
MX-766 Fighter-bomber systems
MX-767 AMC-developed MB-29 Banshee surface-to-surface missile
MX-770 North American Charge Number NA-/XSSM-A-2 (later B-64, SM-64)
    Navajo surface-to-surface cruise missile
MX-771 Martin M-/XSSM-A-1 surface-to-surface cruise missile
MX-772 Curtiss-Wright SSM study
MX-773 Republic SSM study
MX-774 Convair RTV-A-2 HiRoc test vehicle (Atlas ICBM) terminated 1947
MX-775A Northrop N-69 XSSM-A-3 (later B-62, SM-62) Snark surface-to-
    surface cruise missile
MX-775B Northrop N-Boojum surface-to-surface missile
MX-776 Bell XASM-A-2 (later B-63, GAM-63) Rascal air-to-surface missile
MX-776A Development of XLR65-BA-1 for X-9 Shrike (test bed for Rascal)
MX-776B Development of XLR67-BA-1 for Rascal
MX-777 McDonnell ASM studies (100mi range, supersonic); changed to
    AUM Hydrobomb
MX-778 Goodyear ASM study (100mi range, subsonic)
MX-778A Guidance system, Atron, Type A-1
MX-779 Goodyear ASM study (100mi range, supersonic)
MX-791 Establishment of RAND Corporation think tank
MX-794 Wizard anti-ballistic missile study, University of Michigan
MX-795 Thumper anti-ballistic missile study, General Electric
MX-798 Hughes AAM study; replaced later by MX-904
MX-799 Ryan AAM-A-1 Firebird AAM
MX-800 M. W. Kellogg supersonic fighter-launched AAM
MX-801 Bendix supersonic fighter-launched AAM
MX-802 General Electric supersonic bomber-launched AAM study "Dragonfly"
MX-808 Northrop N-24 XP-89 (later XF-89)
MX-809 Republic AP-31 XP-91 (later XF-91)
MX-810 Northrop N-/XS-4 (later X-4) Bantam/Skylancer
MX-811 McDonnell 36C XP-88 (later XF-88 and XF-88A)
    Penetration Fighter
MX-812 Lockheed XP-90 (later XF-90 and XF-90A) "Super Star"
    penetration fighter
MX-813 Consolidated-Vultee XP-92
MX-815 AMC-developed Lockheed QF-80 target drone
MX-835 Development of the large XH-17 heavy-lift helicopter
MX-838 Martin M-234 XB-51 (formerly XA-45 attack bomber) "Panther"
MX-839 Boeing B-464-67 XB-52
MX-841 XH-15 helicopter
MX-842 Phase I and II development of XH-16 helicopter
MX-852 Development of all-weather (night/inclement weather) fighter
MX-864 High-speed aircraft canopy jettisoning and ejection seat test methods
MX-871 Convair supersonic bomber study
MX-872 Radioplane XQ-1, jet-powered, unmanned, remotely-controlled target
MX-873 Ryan XQ-2, target, aerial, unmanned and remotely-controlled target
MX-880 Douglas XB-42A, experimental mixed-power (composite piston and
    jet) bomber
MX-883 Lockheed Advanced Development Projects PTV-A-1 (later X-7) ramjet
    test vehicle
MX-894 60,000# thrust X90ALT turbojet/rocket engine
MX-896 Nitromethane-fueled rocket motor
MX-899 Nitric acid-hydrocarbon rocket motor 14,000# variable thrust
MX-903-A 15,000# thrust liquid oxygen-alcohol rocket motor
MX-904 Project "Dragonfly" Hughes XAAM-A-2 Falcon air-to-air guided
    missile (see MX-1179)
MX-908 Development and test of the General Electric J47 or J53 turbojet
MX-909 Republic XF-91 with Curtiss-Wright rocket motor
MX-939 High-speed ballistic bomb drop tests
MX-955 Beech T-34 Mentor, piston-powered primary trainer
MX-958 Shoran relay system
MX-965 Remote flight control system for guided missiles
MX-981 Northrop N-27 Low-Speed Track Unit (crash sled for 2,000' track)
    deceleration system
MX-984 Bell 58 X-1A, X-1B and X-1D aircraft fourth version, proposed
    rocket-powered X-1C interceptor aircraft, cancelled prior to construction
MX-993 Design study for a turbojet engine optimized for supersonic missiles
MX-996 XJ55-FF-1 expendable turbojet engine
MX-1001 Rigid boom-type in-flight refueling system (Boeing Flying Boom)
MX-1005-A Qualification and service testing of 15KS-100 JATO units
MX-1005-D Booster rocket for MX-904 XF-98 (later GAR-1, AIM-4)
    Hughes Falcon AAM
MX-1005-E Booster rocket for MX-771 Martin Matador
MX-1011 Aerojet General X-8 Aerobee research rocket
MX-1016 Wing-tip Coupling (towing) Project (fighter escort and range
    extension tests) for Conveyor Fighter program B-29A and F-84D
MX-1017 All-weather interceptor missile fire control system
MX-1018 Project Tom-Tom, wingtip-to-wingtip attachment of two EF-84
    Thunderjets to an EB-29
MX-1022 Boeing jet-powered bomber study
MX-1059 Lear flight control system for Lockheed X-7
MX-1063 Passive target seeker
MX-1079 Development and qualification of Aerojet General XLR45-AJ-1
    JATO unit
MX-1084 Aerial camera system for direct and remote printing
MX-1086 General physics of night aerial photography
MX-1095 Bell 60 XS-5 (later X-5) variable sweep research airplane
MX-1097 Shoran bombing system
MX-1119 Shoran II bombing system
MX-1116-A Development of P&W JT3 YJ57-P-3 turbojet engine
MX-1132 Parachute deployment tests; recovery systems for guided
    missiles and target drone aircraft (Deceleration Track)
MX-1132 [sic] Cook Supersonic Sled
MX-1179 Hughes fire control system for Falcon AAM, F-102 (MB-1)
MX-1200 Automatic ground-position indicator
MX-1201 Air-to-air rendezvous system
MX-1205 AN/ART-27(XA) crash locator beacon
MX-1209 AN/ARC-22 short-range radio equipment
MX-1210 Voice recorder and recorder-producer equipment
MX-1218 AN/APS-27 Airborne Radar Search Equipment Set
MX-1226 AN/APW-11 remote control system (20-175 mi range)
MX-1241 Radar tests
MX-1242 Television equipment for drone aircraft
MX-1257 Long-distance electronic communications techniques
MX-1259 New audio systems
MX-1420 Electronic anti-jamming techniques
MX-1425 Aeronautical ice research laboratory
MX-1441 High-speed bombing radar system
MX-1445 Non-radiating bombing system
MX-1450 Wright Field, high altitude balloon and rocket tests with
    animals on board
MX-1457 Boeing Project Brass Ring, interim carrier for high-yield
    hydrogen bombs, MB-47
MX-1473 Development of airborne electronic aids to identification (IFF)
MX-1489 Aircraft starter system non-electric
MX-1498 Project Moby Dick strategic reconnaissance balloons
MX-1500 Components for FM remote control system
MX-1501 Fuels for reciprocating engines
MX-1517 Propellants and components for 2.75 in FFAR (Folding-fin Aircraft Rocket)
MX-1518 Aircraft weapons
MX-1519 New family of [more aerodynamic] bombs and related equipment
MX-1520 Weapons and ammunition
MX-1521 Development and tests of rocket launching systems
MX-1521-A Combination Rocket and Fuel Tank (CRAFT)
MX-1525 Minimum temperature requirement study for operation of USAF
    aircraft and equipment
MX-1537 Special problems, USAF munitions
MX-1554 "1954 All Weather Interceptor," to complement the F-104; led to
    development of the F-102A (WS-210A); the proposed Republic XF-91B
    was one response
MX-1556 Surface contaminating biological warfare munitions
MX-1557 Systems for dispersion of biological warfare munitions
MX-1558 Air contaminating biological warfare munitions
MX-1559 Aerosol generator
MX-1560 One-half pound particulate bomb
MX-1561 Gas bomb for G agents
MX-1565 Prevention of deterioration center
MX-1573 Fighter identification system
MX-1574 External stores on fighter aircraft
MX-1578 Aircrew emergency pressure cell
MX-1579 Airborne command and control data link
MX-1587 Interconnection of AN/APN-66 with search radar sets
MX-1589 Convair X-6 (NB-36H) nuclear-powered aircraft test program
MX-1590-B Design, development, fabrication and flight-test of Marquardt
    XRJ43-MA-3 ramjet engine
MX-1590-D Construction of ramjet Research and Development (R&D)
    facilities at Marquardt Aircraft Company
MX-1590-E Design, development, fabrication and flight-test of Marquardt
    XRJ43-MA-1 ramjet engine
MX-1593 Convair (General Dynamics) X-11, X-12 rockets (Atlas); study phase
    for an ICBM. Follow-on to MX-774 surface-to-surface strategic rocket
MX-1594 Project Gopher
MX-1597 Fire control system for a low-altitude interceptor (E-4)
MX-1599 Boeing XF-99 (later IM-99) BoMarc liquid propellant booster thrust
    chamber and gas generator feed system
MX-1600-A Project Lazy Dog anti-personnel projectile
MX-1601 North American "Nasty," rearward-firing bomber-launched AAM
MX-1602 RB-36/RF-84 Reconnaissance Parasite Aircraft program
MX-1604 Development of convertiplane type aircraft, McDonnell XV-1
MX-1608 Boeing B-464 XRB-52
MX-1610 Rotary wing propulsion system study
MX-1611 System bombing, long-range, ground controlled, tactical
MX-1616 Parasite aircraft system study
MX-1624 T-55 Trizon guided bomb; 3,000# standard ordnance warhead
MX-1626 Convair supersonic bomber study; replaced later by MX-1964
MX-1630 Stabilization and automatic flight control system for aircraft
MX-1632 Project Red Dog
MX-1640 Turbopropjet engine for L-19A aircraft
MX-1647 Shoran bombing system accuracy tests
MX-1658 Republic AP-31-N1 XF-91A (proposed)
MX-1660 American Helicopter pulsejet-powered main rotor system
MX-1664 New family of chemical bombs
MX-1672 Supersonic parachute recovery system for guided missiles and
    target aircraft
MX-1674 Additional Tarzon bomb development study
MX-1678-A Chaff dispensers and systems
MX-1685-3 Aircraft fuel conditioning
MX-1688-A Self-contained automatic navigation system for fighter aircraft
MX-1688-B Automatic celestial navigation system (controlled heading)
MX-1690 Airborne gamma radiation intensity meter
MX-1692 Pneumatic and electric power unit for ground operation of B-52 aircraft
MX-1701 Single-place XH-26 helicopter
MX-1703 Douglas X-3 panoramic camera installation study
MX-1712 Boeing B-701-1-1 XB-59 double-sonic bomber; replaced later by MX-1965
MX-1719 Free-fall target, XQ-3
MX-1726 Drag-less antennas for high-speed aircraft
MX-1733 Design and development of components for Aerojet XL13-AJ-9 rocket motor
MX-1737 Night photography illumination
MX-1738 Low-altitude night photography pyrotechnics
MX-1745 Split-wing ramjet engine
MX-1747-A Development and test of LR47 ATO rocket motor
MX-1787 Dual turbojet/ramjet powerplant system for Republic AP-57 XF-103
    "Thunderwarrior"; Rolls-Royce (Bristol) Olympus YJ67-W-3 turbojet and
    Wright XRJ55-W-1 ramjet WS-204A
MX-1850 Handling, loading, dropping and recovery of T-12 bombs in conjunction
    with parachute drogue tests
MX-1867 Development and Operation of the Experimental Rocket Engine Test
    Station (new facilities)
MX-1868 Oerlikon experimental SAM study
MX-1894 North American supersonic day fighter (F-100)
MX-1895 Sikorsky H-19B utility helicopter
MX-1911 Type P-2 and P-3 strike cameras
MX-1932 Allison J71 turbojet
MX-1934 Douglas B-66
MX-1954 Automatic air interception system for Convair F-102r
MX-1960 Northrop N-124 RSM-62 Snark Unmanned photo-recon missile
MX-1961 Aerojet General 150 Aerobee-Hi
MX-1964 Convair XB-58
MX-1965 Boeing B-701 XB-59
MX-2013 Radioplane GAM-67 Crossbow cruise-type ASM
MX-2041 Trizon guided bomb
MX-2091 Douglas cruise missile-carrying bomber study
MX-2092 Martin cruise missile-carrying bomber study
MX-2118 General Electric J79 turbojet
MX-2143 Teledyne-Ryan Q-2 Firebee high altitude jet-powered drone
MX-2145 Chemically-powered Bomber (CPB) led to XB-70
MX-2145A Boeing/Bell Bomber Missile (BOMI) weapon system
MX-2147 Bell 67 X-16 "Bald Eagle"
MX-2223 Fairchild SM-73 Bull Goose long range bomber decoy missile
MX-2224 Convair XGAM-71 Buck Duck bomber-launched decoy missile
MX-2226 Lockheed reconnaissance satellite system (became WS-117L)
MX-2273 General Electric J85 turbojet
MX-2276 Bell Bomber-Missile (BOMI) manned multi-stage boost-glide
    rocket-powered vehicle (became SS-118P)
MX-2347 Republic XF-84H "Thundersceech" (formerly XF-106) supersonic
    propeller test-bed aircraft (could be MX-3347)

Weapon System Numbers

According to the U.S. Air Force Dictionary, a Weapon System is a total entity consisting of an instrument of combat (a single unit of striking power), such as a bomber, fighter, or guided missile, together with all related equipment, supporting facilities and services required to bring the instrument upon its target or to the place where it carries out the function for which built.

The Weapon System (WS), Supporting System (SS), Operational Support (OS) and Research Support (RS) numbers discovered thus far:

WS/SS/OS/RS Numbers

WS-100A High-altitude SAC Bomber System, Boeing B-450 B-47
WS-100L High-altitude SAC Recon System, Boeing B-450 RB-47
WS-101A High-altitude SAC Bomber System, Boeing B-462 B-52
WS-101L High-altitude SAC Recon System, Boeing B-462 RB-52
WS-102A High-altitude SAC Bomber System, Convair B-58
WS-102L High-altitude SAC Recon System, Convair RB-58
WS-103A SAC Missile System, Northrop N-/SM-62 Snark
WS-104A North American SM-64 Navaho
WS-105A McDonnell 36W F-101A/C
WS-105L McDonnell 36X RF-101A/C
WS-107A-1 ICBM System, includes Convair SM-65 Atlas
WS-107A-2 ICBM System, includes Martin SM-68 Titan
WS-110A Chemically-powered Strategic Bomber, North American NA-/XB-70
WS-110L Chemically-powered Reconnaissance Bomber, North American
    XRB-70 (proposed; not proceeded with)
WS-112A Bell GAM-63 Rascal
WS-117L Advanced Recon Satellite System, Lockheed Reconnaissance
    Satellite System
WS-117M Samos
WS-119L Jet Tanker/Cargo System, Boeing B-717 C/KC-135
WS-120A Large ICBM with MIRV warhead; successor to Minuteman not
    proceeded with
WS-121A Radioplane GAM-67 Crossbow
WS-121B Radioplane Longbow Anti-radiation Missile
WS-122A McDonnell ADM-20 (ex GAM-72) Quail
WS-123A Fairchild GAM-73 Bull Goose
WS-124A Weather Reconnaissance Balloon
WS-125A Nuclear-powered Strategic Bomber System
WS-129A General Dynamics FB-111A
WS-131B ASM for B-52, North American AGM-28 (ex GAM-77) Hound Dog
WS-132A Bomber Defense Missile for WS-110A (B-70)
WS-132B Decoy Missile
WS-133A Boeing LGM-30 (ex-SM-80) Minuteman ICBM
WS-138A Douglas AGM-48 (ex-GAM-87) Skybolt
WS-139A North American Rockwell (NAR) B-1A
WS-140A Boeing AGM-69 SRAM
WS-199A SAC System Studies
WS-199Y High-energy Fuel Studies
WS-200A Missile Interceptor System, Boeing CIM-10 (ex IM-99) BOMARC
WS-201A Convair 8-10 F-102A
WS-201B All-weather Interceptor System, Convair 8-24 F-106A/8-27 F-106B
WS-201L Convair 8-12 TF-102A
WS-202A Hughes ASG-18 Fire Control and GAR-9 Falcon, North American
    Charge Number NA-/F-108 Rapier
WS-204A Republic AP-57, XF-103
WS-205A Northrop N- F-89J Scorpion
WS-206A North American Charge Number NA-/F-86D
WS-208A GAR System, Hughes AIM-26 (ex GAR-11) Nuclear Falcon AAM
WS-216L SAGE (Semi-automatic Ground Environment) Air Defense System
WS-217A Long-range Interceptor System, McDonnell 36AT F-101B
WS-218A Bendix IM-70 Talos
WS-220A Hughes AIM-4A/-B/-C/-D Falcon AAM Series (ex GAR-1/-2/-3/-4)
WS-221A GAR-8 System, Philco/Ford AIM-9 (ex GAR-8) Sidewinder AAM
WS-239A Missile Defense Alarm System, MIDAS
WS-299A Air Defense System Studies
WS-300 Tactical Air Warfare System
WS-302A Martin SM-68 (ex B-68)
WS-303A Lockheed 183-93-02 XF-104
WS-303G Mutual Security/Case, Lockheed F-104Gr
WS-303L Lockheed RF-104A
WS-306A Tactical Fighter-Bomber System, Republic AP-63-31 YF-105A
WS-306B North American F-107A
WS-307A Martin M-272 B-57B/C (Night Intruder)
WS-307L Martin M-272A RB-57A and -57D
WS-308A/L Douglas B/RB-66B
WS-309A Low-altitude Tactical Missile System, TM-76A/-76B Mace
WS-316Z North American F-86
WS-317 Anti-tank Guided Air Rocket (ATGAR)
WS-319Z Hughes AGM-65 Maverick
WS-321A Tactical ASM System, GAM-83B Bullpup
WS-323A Tactical Strike-Recon System
WS-324A General Dynamics 12 F-111A "Aardvark"
WS-324G F-111G
WS-324L EF-111A Raven
WS-326A McDonnell 98DF RF-4C; formerly RF-110A
WS-327A McDonnell 98DE F-4C; formerly F-110A
WS-327B McDonnell 98EN F-4D
WS-327C McDonnell 98GV-1 F-4E
WS-328A McDonnell F-15A
WS-328D F-15D
WS-328E F-15E
WS-329A Republic A-10A
WS-398B Theatre Missile, ballistic (TM)
WS-399A Tactical System Studies
WS-399B ZEro-Length Launch (ZELL) study
WS-649C Tactical Mach 2 VTOL All-weather Fighter

Supporting Systems Numbers

SS-400L Medium Cargo System, Lockheed C-130
SS-400N Transport Carrier/Assault Fixed-wing Aircraft
SS-402L Logistic Carrier System, Douglas C-133A
SS-412L Air Weapons Control System
SS-414M GB Electronic Countermeasure System
SS-416L Continental AC&W Support System
SS-420A MAP Fighter Weapons System, Northrop N-156F (became F-5A/B)
SS-420L Jet Basic Trainer, Northrop N-156T T-38A
SS-424L Intermediate Jet Trainer System
SS-425L NORAD Combat Operations Center
SS-426L Low Supersonic Drone, Q-4
SS-429L Target Drone System, Ryan Q-2 Firebee
SS-431L Traffic Control and Landing System
SS-433L Weather Observation and Forecast System
SS-438L Intelligence Data-handling System
SS-443L Army Helicopter System, XH-40
SS-452L Utility/Trainer Aircraft, North American T-39
SS-460L Weather Recon Support System
SS-462L Powered Target Support
SS-463L Material Handling Support System
SS-464L Lockheed C-141A
SS-465L Strategic Air Command Control System
SS-466L Electronic Intelligence Communication Operations
SS-467L Advanced Navigational Training Support System
SS-471L Army Helicopter, Chinook
SS-472L Test Bed Aircraft for Support Systems
SS-473L Headquarters USAF Operations Control
SS-480L AF Communication System
SS-495L MARK XII Identify, Friend or Foe (IFF) System
SS-496L Space Track System
SS-497A Miscellaneous NASA System Work
SS-498A Advanced Research Projects Agency (ARPA) Work Orders
SS-498C SC-130B
SS-498D Strategic Communications System
SS-498E MATS Modernization
SS-499A Supporting System Planning
SS-499C Advanced System and Space Vehicle Studies
SS-499D Intelligence and Recon System Study

Operational Support Numbers

OS-520B Support Equipment
OS-530A Guidance and Weapons
OS-550A Aeronautical Equipment
OS-550E Propulsion
OS-560A Electronics and Communication
OS-570A Aerospace Environment
OS-580A Human Factors
OS-580E Targets and Drones

Research Support Numbers

RS-600 Advanced Development
RS-600A Advanced Systems
RS-601A Supersonic Pilotless Test Vehicle, Lockheed X-7
RS-602A Convertiplane Vehicle, XV-3
RS-603A Ryan X-13 Vertijet VTOL Research Vehicle
RS-604A VTOL Aircraft Problem Investigation
RS-605A North American X-15A Research Vehicle
RS-606A AVRO VTOL Aircraft
RS-607A Hiller X-18 Tilt Wing VTOL Aircraft
RS-609A Hypersonic Environment Test
RS-614A Advanced AICBM
RS-618A Dispersed Site VTOL
RS-620A Boeing X-20 Dyna-Soar
RS-625A Aircraft Nuclear Propulsion Manned
RS-638A Douglas AGM-48 (ex GAM-87) Skybolt
RS-649A SAC Experimental Vehicle Studies
RS-649C STOL Fighter System
RS-649D Advanced AICBM
RS-649E Space Counterweapons System
RS-650A Test Instrumentation
RS-655 Advanced Subsystems and Components
RS-655A Propulsion
RS-665A Electronics
RS-675A Guidance and Weapons
RS-685A Human Factors
RS-695 Advanced Development Support
RS-695A RAND Corporation
RS-695B Analytical Service Inc (ANSER)
RS-695C Itek Corporation
RS-695L Lincoln Laboratories
RS-695N Space Technology Laboratory (STL), Atlas
RS-695P STL, Martin Titan
RS-695Q STL, Douglas Thor
RS-695R STL, Boeing Minuteman
RS-695S STL, Samos/Midas