| L | lumen |
| L&C | laboratory and checkout |
| L&D | landing and deceleration |
| L&L | launch and landing |
| L&LS | launch and landing site |
| L&M | Light and Medium Vehicles Office (MSFC) |
| L&S | land and sea |
| L&S | logistics and support |
| L&T | Laboratories and Test |
| L-L | line-to-line |
| L-RFE | L-band RF electronics |
| L/C | launch complex |
| L/C | letter contact |
| L/D | length-to-diameter |
| L/D | lift-to-drag ratio |
| L/E | left-hand engine |
| L/H | local horizontal |
| L/M | list of materials |
| L/O | lift-off |
| L/R | locus of radius |
| L/S | landing site |
| L/S | load system |
| L/T | load test |
| L/V | launch vehicle |
| L1 | primary navigation signal (1,572.42 MHz) |
| L2 | secondary navigation signal (1,227.6 MHz) |
| L3 | NDS payload signal (1,381.05 MHz) |
| LA | launch abort |
| LA | launch aft |
| LA | launch and ascent |
| LA | launch area |
| LA | launch azimuth |
| LA | lightning arrester |
| LA | low attitude |
| LAC | Lockheed Aircraft Corporation |
| LACB | Landing Aids Control Building |
| LACI | laser autostigmatic cube interferometer |
| LACIE | large-area crop inventory experiment |
| LACIP | large-area crop inventory program |
| LADS | logistic automated data system |
| LAET | limiting actual exposure time |
| LAGEOS | laser geodynamic satellite |
| LAGS | launch abort guide simulation |
| LAI | logistics artificial intelligence |
| LAIRT | large-aperture infrared telescope |
| LAIU | launch abort interface unit |
| LAM | low-altitude mission |
| LAMMR | large-antenna multichannel microwave radiometer |
| LAMOD | laser optical motion detector |
| LAMP | LODE advanced mirror program |
| LAMPS | light airborne multipurpose system |
| LAN | local area network |
| LANES | III LAN extensible simulator |
| LANL | Los Alamos National Laboratory |
| LAP | linear accelerometer package |
| LAPSS | large-area pulse solar simulator |
| LARS | laminar angular rate sensor |
| LARSSYAA | Laboratory for Application of Remote Sensing Aircraft Analysis |
| LAS | low-altitude sensor |
| LASERCOM | laser communications payload |
| LASS | large-amplitude space simulator |
| LASS | low-altitude surveillance system |
| LASV | low-altitude supersonic vehicle |
| LAT | large angle torque |
| LAT | logistic asset tracking |
| LAT | lot acceptance test |
| LATRS | laser acquisition and tracking system |
| LAW | low-altitude weapon |
| LB | launch boost |
| LB | load bank |
| LB | low bay |
| LB | lower brace |
| LBA | Latin Businessmen's Association |
| LBDT | low-bay dolly tug |
| LBET | large beam expander technology |
| LBL | left buttock line |
| LBM | liquid boost module |
| LBM | load buffer memory |
| LBNPD | lower body negative pressure device |
| LBR | low bit rate |
| LBS | L-band subsystem |
| LBSP | logistics business systems plan |
| LBTB | launch base test plan |
| LBTPP | launch base test plan/procedure |
| LC | lasercom |
| LC | launch complex |
| LC | launch cost |
| LC | launch countdown |
| LC | launch critical |
| LC | left center |
| LC | load carrier |
| LC&CO | launch control and checkout |
| LCA | launch control amplifier |
| LCA | load control assembly |
| LCA | load controller assembly |
| LCB | least common bit |
| LCC | Launch Control Center |
| LCC | launch commit criteria |
| LCC | launch control complex |
| LCC | leadless chip carrier |
| LCC | life cycle cost |
| LCCD | launch commit criteria document |
| LCD | launch countdown |
| LCE | launch complex engineer |
| LCE | launch complex equipment |
| LCF | low-cycle fatigue |
| LCG | liquid-cooled garment |
| LCH4 | liquid methane |
| LCHTF | low-cycle high-temperature fatigue |
| LCM | least common multiple |
| LCM | liquid crystal mete |
| LCMS | low-cost modular spacecraft |
| LCN | logic change notice |
| LCN | logistics control number |
| LCN | loosely coupled network |
| LCOM | logic control output module |
| LCR | low cross range |
| LCS | launch control system |
| LCS | list of command signals |
| LCU | line coupling unit |
| LCU | load control unit |
| LCUG | liquid cooling undergarment |
| LCV | logistics cargo vehicle |
| LCVG | liquid cooling and ventilation garment |
| LCVG | liquid cooling ventilation garment |
| LD | lateral direction |
| LD | loading dock |
| LDB | launch data bus |
| LDB | logistics data bank |
| LDC | lot date code |
| LDD | logical data base design |
| LDEC | lunar docking events controller |
| LDEF | long-duration exposure facility |
| LDIU | launch data interface unit |
| LDP | large deployable reflector |
| LDP | local data package |
| LDR | low data rate |
| LDRP | logistics depot repair procedure |
| LDS | landing, deservicing, and safing |
| LDS | landing/deceleration subsystem |
| LDS | laser docking sensor |
| LDS | launch detection satellite |
| LDS | layered defense system |
| LDT | level detector |
| LDT | linear displacement transducer |
| LDZ | lithium-depleted zone |
| LE | launch escape |
| LE | leading edge |
| LEA | logistics engineering analysis |
| LEA/MP | logistics engineering analysis and maintenance planning |
| LEADS | LWIR Exoatmospheric Discrimination Study |
| LEAP | lightweight exoatmospheric projectile |
| LEB | lower equipment bay |
| LEC | Lockheed Electronics Company |
| LECP | leading edge connective heat transfer program |
| LED | light-emitting diode |
| LEDC | low-energy detonating charge |
| LEDI | low endoatmospheric defense interceptor |
| LEFF | launch effectivity (flight required to support) |
| LEFM | linear elasticity fracture mechanics |
| LEH | launch and entry helmet |
| LEID | low-energy ion detector |
| LEM | laboratory environment model |
| LEM | launch escape monitor |
| LEO | librating equidistant observer |
| LEO | low Earth orbit (up to 3,000 km) |
| LEP | large external pressurized |
| LER | long eye relief (optics) |
| LER | lunar eyepiece receptacle |
| LES | Lincoln experimental satellite |
| LES | launch equipment shop |
| LES | launch escape subsystem |
| LES | launch-entry suit |
| LES | leading edge subsystem |
| LESS | leading edge structural subsystem |
| LESS | leading edge structure subsystem |
| LESS | leading edge subsystem |
| LET | linear energy transfer |
| LETF | Launch Equipment Test Facility (KSC) |
| LEU | large external unpressurized |
| LEV | lunar excursion vehicle |
| LF | launch facility |
| LF | launch forward |
| LF | load factor |
| LF | low frequency |
| LFA | logistics/functional analysis |
| LFAF | low-frequency accelerometer flutter |
| LFAM | low-frequency accelerometer modes |
| LFAP | low-frequency accelerometer pogo |
| LFF | lower forward fuselage |
| LFM | local focus mechanism |
| LFO | low-frequency oscillator |
| LFOP | Landing and Ferry Operations Panel |
| LFRR | low-frequency radio range |
| LFV | lunar flying vehicle |
| LG | landing gear |
| LGA | low-gain antenna |
| LGS | landing gear subsystem |
| LGTA | landing gear test article |
| LH | left-hand |
| LHA | local hour angle |
| LHC | left-hand circular |
| LHCP | left-hand circular polarization |
| LHCP | left-hand circularly polarized |
| LHCl | liquid hydrogen chloride |
| LHFEB | left-hand forward equipment bay |
| LHOP | laser-hardened optical payload |
| LHP | left-hand panel |
| LHRCS | left-hand reaction control system (subsystem) |
| LHS | left-hand side |
| LHSC | left-hand side console |
| LI | laser illuminator |
| LIB | left inboard |
| LIC | load interface circuit |
| LID | laser-induced damage |
| LID | leadless inverted device |
| LIDAR | laser-radar |
| LIE | left inboard elevon |
| LIFO | last in, first out |
| LIMRC | LRU Identification and Maintenance Requirements Catalog |
| LIMS | logistics information management system |
| LIMS | logistics inventory management system |
| LINC | logic and information network compiler |
| LINJET | liquid injection electric thruster |
| LINS | laser inertial navigation system |
| LIP | land impact program |
| LIS | logistics information system |
| LISP | list processing language |
| LIU | line interface unit |
| LL | launch and landing |
| LL | launch left |
| LL | lever lock |
| LL | live load |
| LL | long lead |
| LL | long line |
| LL | low-level |
| LL | lower limit |
| LLC | logical link control |
| LLCF | launch and landing computational facility |
| LLCSC | low-level computer software component |
| LLCSC | lower level computer software component |
| LLI | limited-life item |
| LLL | limited-life list |
| LLNL | Lawrence Livermore National Laboratory |
| LLO | low lunar orbit |
| LLO2 | lunar liquid oxygen |
| LLOS | landmark line of sight |
| LLP | launch and landing project |
| LLPO | Launch and Landing Project Office |
| LLR | load-limiting resistor |
| LLS | launch and landing site |
| LLT | long lead time |
| LLTIL | long-lead-time items list |
| LM | laboratory module |
| LM | launch mode |
| LM | left mid |
| LM | logistics manager |
| LM | logistics manual |
| LM | long module |
| LM | lunar module |
| LMD | large mirror development |
| LMDE | lunar module descent engine |
| LMDS | logistics management data system |
| LME | launch monitor equipment |
| LMF | lower mid fuselage |
| LMG | left main gear |
| LMIF | lower mechanical integration frame |
| LMLG | left main landing gear |
| LMP | list measurement point |
| LMRT | logistics management responsibility transfer |
| LMS | load measurement system |
| LMS | logistics master schedule |
| LMSC | Lockheed Missiles and Space Corporation |
| LMSS | lunar mapping and survey system |
| LMT | logistics management transfer |
| LNA | low-noise amplifier |
| LNG | liquified natural gas |
| LO | launch operations |
| LO | lift-off |
| LO | local oscillator |
| LO | lock-on |
| LO | lubricating oil |
| LOA | landing operations area |
| LOA | launch operations area |
| LOAD | low-altitude defense |
| LOAP | list of applicable publications |
| LOB | launch operations building |
| LOB | left outboard |
| LOB | line of balance |
| LOC | launch operations center |
| LOC | launch operations complex |
| LOC | launch operations contractor |
| LOC | level of conflict |
| LOC | lines of code |
| LOC | loss of control |
| LOCB | Launch Operations Control Building |
| LOCS | local optical correction system |
| LOD | Launch Operations Directorate |
| LOD | Launch Operations Division |
| LOD | launch order document |
| LODE | large-optics demonstration equipment |
| LODE | large-optics demonstration experiment |
| LOE | left outboard elevon |
| LOE | level of effort |
| LOE | line of effort |
| LOFAR | low-frequency acquisition and ranging |
| LOFO | low-frequency oscillation |
| LOGCENT | Logistics Control Center |
| LOGMOD | logic model |
| LOGO | limit of government obligation |
| LOI | lunar orbit insertion |
| LOIS | Logistics Information Simulator |
| LOL | limit of liability |
| LOLI | limited-operational-life items |
| LON | launch on need |
| LONS | local on-line network system |
| LOO | launch operations orders |
| LOOMS | laser optics operations and maintenance support |
| LOP | Launch Operations Panel |
| LOR | lunar orbit rendezvous |
| LORA | level-of-repair analysis |
| LOS | lift-off simulator |
| LOS | line of sight |
| LOS | loss of signal |
| LOS | loss of sync |
| LOSHEA | line-of-sight hard Earth angle |
| LOSP | Landing Operations Support Panel |
| LOSR | line-of-sight range |
| LOSS | lunar orbital space station |
| LOT | lift-off time |
| LOV | limit of visibility |
| LOWG | Landing Operations Working Group |
| LP | launch pad |
| LP | launch processing |
| LP | line printer |
| LP | liquid propellant |
| LP | low-pass |
| LP | low-pressure |
| LP | lower panel |
| LPA | log periodic antenna |
| LPA | low-power amplifier |
| LPD | landing point designator |
| LPD | launch preparation document |
| LPD | launch procedure document |
| LPD | list of physical dimensions |
| LPE | liquid phase epitaxy |
| LPF | low-pass filter |
| LPFT | low-pressure fuel turbopump |
| LPFTP | low-pressure fuel turbopump |
| LPG | liquid-propellant gun |
| LPI | low probability of intercept |
| LPIF | Launch Package Integration Facility |
| LPLWS | launch pad lightning warning system |
| LPOP | low-pressure oxidizer pump |
| LPOT | low-pressure oxidizer turbopump |
| LPOTP | low-pressure oxidizer turbopump |
| LPOX | low-pressure oxygen |
| LPS | large pointing system |
| LPS | launch processing system |
| LPTTL | low-pressure transistor-transistor logic |
| LQR | linear quadratic regulator |
| LR | laboratory request |
| LR | landing radar |
| LR | launch right |
| LR | left rear |
| LR | left rudder |
| LR | lower right |
| LR/LD | line receiver/line driver |
| LRA | laser retroreflector array |
| LRB | liquid rocket booster |
| LRCA | long-range combat aircraft |
| LRD | Launch Recovery Division |
| LRD | launch requirements document |
| LRE | latest revised estimate |
| LRE | liquid rocket engine |
| LRES | Liquid Rocket Engine Stability Program |
| LRF | liquid rocket fuel |
| LRIP | low-rate initial production |
| LRO | large radio observatory |
| LROSS | Long-Range Optical System Study |
| LRP | long-range plan |
| LRR | launch readiness review |
| LRSI | low-temperature reusable surface insulation |
| LRU | line replaceable unit |
| LRU | lowest replaceable unit |
| LRV | launch readiness verification |
| LRV | long-range video |
| LRV | lunar roving vehicle |
| LRW | left rendezvous window |
| LS | landing site |
| LS | launch sequence |
| LS | launch site |
| LS | left side |
| LS | life science |
| LS | life systems |
| LS | limit switch |
| LS | local store |
| LS | long scarf (thruster nozzle) |
| LS/PPF | Launch Site Payload Processing Facility |
| LS/ST | light shield/star tracker |
| LSA | labor surplus area |
| LSA | launch services agreement |
| LSA | logistics support analysis |
| LSACN | logistics support analysis control number |
| LSAH | Launch Site Accommodations Handbook |
| LSAP | launch sequence applications program |
| LSAP | logistics support analysis plan |
| LSAR | logistics support analysis record |
| LSAS | logistics support analysis strategy |
| LSB | launch support building |
| LSB | least significant bit |
| LSB | lower side band |
| LSC | Launch Services Contract (contractor) |
| LSC | launch support contractor |
| LSC | launch support controller |
| LSC | linear-shaped charge |
| LSCA | logistics support cost analysis |
| LSD | launch systems data |
| LSD | low-speed data |
| LSE | launch support equipment |
| LSE | life support equipment |
| LSEAT | launch systems evaluation advisory team |
| LSF | laboratory simulation facility |
| LSF | launch support facility |
| LSFR | launch site flow review |
| LSG | linear sequence generator |
| LSI | Lear Siegler, Incorporated |
| LSI | large-scale integration |
| LSIC | large-scale integrated circuit |
| LSIC | launch support integration contractor |
| LSIC | launch system integration contractor |
| LSID | launch sequence and interlock document |
| LSM | life science module |
| LSM | logistics support manager |
| LSMDB | logistics simulation models and data bases |
| LSO | Launch Support Operations |
| LSO | landing support officer |
| LSO | large solar observatory |
| LSO | life systems officer |
| LSOC | Lockheed Space Operations Company |
| LSOC | launch support operations contractor |
| LSP | least significant portion |
| LSPDF | Life Science Payload Development Facility |
| LSPPS | logistics support plan for preoperational support |
| LSR | land-sea rescue |
| LSR | laser scanning radar |
| LSR | launch site recovery |
| LSR | launch support request |
| LSR | logistics shop release |
| LSR | logistics success rate |
| LSRM | life science research module |
| LSS | landing and separation simulator |
| LSS | large space structure |
| LSS | launch site support |
| LSS | launch support services |
| LSS | life support system (subsystem) |
| LSS | load sensing system |
| LSSC | launch site support contractor |
| LSSD | level-sensitive scan design |
| LSSE | laser sensor support equipment |
| LSSL | Life Sciences Space Laboratory |
| LSSM | launch site support manager |
| LSSP | launch site support plan |
| LSSRC | life sciences Shuttle research centrifuge |
| LSST | launch site support team |
| LST | large space telescope |
| LST | large stellar telescope |
| LST | launch support team |
| LST | liquid storage tank |
| LST | local standard time |
| LSTD | laser system technology demonstration |
| LSTE | launch site transportation equipment |
| LSTS | launch site test set |
| LSU | life support umbilical |
| LSUR | launch site utilization report |
| LT | lead time |
| LT | lot traceability |
| LTA | lighter than air |
| LTA | lower torso assembly |
| LTD | lift-to-drag |
| LTD | long-term disability |
| LTDT | Langley transonic dynamics tunnel |
| LTG | linear tangent guidance |
| LTH | lethality and target hardening |
| LTHIS | laboratory test hardware inventory status |
| LTM | lead time matrix |
| LTM | load transformation matrix |
| LTR | laboratory test report |
| LTV | Ling Tempco Vaught |
| LTV | lunar transfer vehicle |
| LTVC | linear terminal velocity constraint |
| LTWG | Launch Test Working Group |
| LUD | layup die |
| LULAC | League of United Latin American Citizens |
| LUPI | laser unequal path interferometer |
| LUPWT | Langley unitary plan wind tunnel |
| LUS | liquid upper stage |
| LUT | launch umbilical tower |
| LV | launch vehicle |
| LV | lift vector |
| LV | limit value |
| LV | load vertical |
| LV | loading valve |
| LV | local vertical |
| LV | low-voltage |
| LVDC | launch vehicle digital computer |
| LVDT | linear variable differential transformer |
| LVDT | linear velocity displacement transducer |
| LVDT | linear voltage differential transformer |
| LVE | low-voltage electronics |
| LVFRR | launch vehicle flight readiness review |
| LVIP | launch vehicle integration plan |
| LVIS | logistics verification information system |
| LVLH | local vertical/local horizontal |
| LVO | launch vehicle operations |
| LVP | low-voltage pressure |
| LVPS | low-voltage power supply |
| LVR | low-voltage release |
| LVS | launch vehicle simulator |
| LVS | launch vehicle system |
| LVSG | Launch Vehicle Study Group |
| LVSSTS | launch vehicle safety system test set |
| LVTC | launch vehicle test conductor |
| LW | launch window |
| LW | lightweight |
| LWA | local wavefront analyzer |
| LWD | launch window display |
| LWD | left wing down |
| LWG | Logistics Working Group |
| LWHS | lightweight headset |
| LWIR | long-wavelength infrared |
| LWOP | leave without pay |
| LWS | lightning warning system |
| LaNi5 | lanthanum pentanickel |
| LaRC | Langley Research Center (Hampton, Virginia) |
| LeRC | Lewis Research Center (Cleveland, Ohio) |
| Leasat | leased satellite |
| LiOH | lithium hydroxide |
| loran | long-range navigation |
| lpW | lumens per watt |
| lpm | lines per minute |
| lps | liters per second |