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TRW

Lunar Module Descent Engine (LMDE)

TRW's throttleable, pintle-injector hypergolic engine that landed the Apollo Lunar Module; sources name a titanium case with a silica/phenolic ablative liner, a thin columbium C-103 nozzle extension and a stainless-steel, then columbium, pintle tip.

Engines
Product IDgrumman-lunar-module-descent-engine
Visit TRW
Maximum thrust (vacuum, full throttle position)
10,500 lbf
First flight engine delivered
August 1966
Maximum nominal thrust (introduction)
9,850 lbf
Minimum throttle point
10 percent of rated thrust

In short

TRW's throttleable, pintle-injector hypergolic engine that landed the Apollo Lunar Module; sources name a titanium case with a silica/phenolic ablative liner, a thin columbium C-103 nozzle extension and a stainless-steel, then columbium, pintle tip.

Application

One LMDE sat in the central bay of each Lunar Module descent stage and slowed the vehicle from lunar orbit to a hover and landing, throttling down to about a tenth of its rated thrust. NASA Marshall says the pintle injector of SpaceX's Merlin 1D was first used in this Apollo-era engine.

How it is built

Thrust chamber

  • Chamber and exit-cone forgings
  • Ablative-lined case to 16:1
  • Ablative liner
  • Liner insulation layer
  • Structural shield

Nozzle extension

  • Nozzle extension skirt (16:1 to about 48:1)
  • Nozzle extension coating

Injector

  • Pintle tip, original
  • Pintle tip, copper-slug version
  • Pintle tip, qualification version
  • Variable-area sleeve
  • Injector face baffle

Propellant flow control

  • Cavitating venturi flow-control valves (2)
  • Flow-control valve elbow, original
  • Flow-control valve elbow, redesigned
  • Flow-control valve bellows
  • Propellant shutoff valves

Gimbal and heat shield

  • Gimbal frame
  • Gimbal trunnion bearings
  • Gimbal actuators
  • Radiation heat shield foil
  • Radiation heat shield spacer

Propellants

  • Fuel
  • Oxidizer
Where the parts areNumber of parts we have listed in each group
  • Thrust chamber8
  • Propellant flow control7
  • Injector5
  • Gimbal and heat shield5
  • Nozzle extension2
  • Propellants2

What it is made of

  • stainless steel (grade not stated)

    Used in Pintle tip, original and Flow-control valve bellows.

  • Titanium (commercially pure, grades 1 to 4)

    Used in Ablative-lined case to 16:1 and Structural shield.

  • Aluminium alloy 6061

    Used in Flow-control valve elbow, original and Flow-control valve elbow, redesigned.

  • 7075-T73 aluminium alloy

    Used in Gimbal frame.

  • A-286 steel

    Used in Head-end attachment bolts (36).

The materials by familyHow many of the parts that name a material use each one
  • Other7
  • Stainless steel5
  • Titanium4
  • Aluminium4
  • Copper1
  • Glass fibre1

How it connects to other things

Used in

Made or supplied by

  • TRW (Space Technology Laboratories)

    Designer and builder of the flight engine

  • Wah Chang Company

    Columbium nozzle extension and its coating

  • Bendix Commercial Vehicle Systems

    Electric throttle actuator

  • Airesearch Mfg. Company

    Gimbal actuators

Products that use the same materials

  • Apollo Command and Service Module

    North American Aviation

    stainless steelTitaniumcolumbium alloyfiberglass wool
    Where each one is used

    stainless steel. Here: Pintle tip, original; Flow-control valve bellows and more. There: Outer shell (heat shield structure); VHF scimitar antennas and more.

    Titanium. Here: Ablative-lined case to 16:1; Structural shield and more. There: Helium tanks (2); Fuel tanks (2) and more.

    columbium alloy. Here: Pintle tip, qualification version. There: SPS nozzle extension.

    fiberglass wool. Here: Radiation heat shield spacer. There: Thruster outer wrap.

  • Apollo Lunar Module (LM)

    Grumman / NASA

    Titanium7075-T73 aluminium alloytitanium alloy 6Al-4V
    Where each one is used

    Titanium. Here: Ablative-lined case to 16:1; Structural shield and more. There: Some brackets and fasteners (lunar module); Descent-stage hot-area structure and more.

    7075-T73 aluminium alloy. Here: Gimbal frame. There: Outrigger truss members and landing-gear struts (redesigned); Gimbal ring and gimbal drive actuators.

    titanium alloy 6Al-4V. Here: Chamber and exit-cone forgings. There: Combustion chamber case (titanium alloy).

  • CubeSat 101

    NASA CubeSat Launch Initiative

    Aluminium alloy 6061Copper
    Where each one is used

    Aluminium alloy 6061. Here: Flow-control valve elbow, original; Flow-control valve elbow, redesigned. There: CubeSat structure; CubeSat structure (template row 2, body type Box).

    Copper. Here: Pintle tip, copper-slug version. There: Cabling, etc. (template row 14).

  • NASA small spacecraft structures review

    NASA Ames

    Aluminium alloy 6061Copper
    Where each one is used

    Aluminium alloy 6061. Here: Flow-control valve elbow, original; Flow-control valve elbow, redesigned. There: EnduroSat 3U structure; ISISPACE 3U structure and more.

    Copper. Here: Pintle tip, copper-slug version. There: Frangibolt actuator cylinder.

  • Rockwest solar array substrate

    Rockwest Composites

    Copperfiberglass wool
    Where each one is used

    Copper. Here: Pintle tip, copper-slug version. There: Copper traces in the skins.

    fiberglass wool. Here: Radiation heat shield spacer. There: G10 fiberglass skins with integrated copper traces.

  • OreSat

    PSAS / Oregon State

    Aluminium alloy 6061Copper
    Where each one is used

    Aluminium alloy 6061. Here: Flow-control valve elbow, original; Flow-control valve elbow, redesigned. There: 1U +X frame; Card wedge (card clamp) and more.

    Copper. Here: Pintle tip, copper-slug version. There: Helical antenna (+Z end card); Outer copper foil and more.

What we do not know

No standards; the metal felt alloy, ball-valve and venturi alloys are not stated.

The detailed data

What is written above is built from these numbers and quotes. Each row links to the page it was taken from. Get all of it as JSON, or ask our MCP server.

Features

  • Single-element injector with a sliding sleeve meters oxidizer (centre) and fuel (outer annulus) together
  • Sleeve is linked 1:1 to two cavitating venturi flow-control valves that fix flow independent of injector pressure
  • Ablatively lined chamber with a fuel barrier coolant, rated for 1,000 seconds
  • Chamber liner is oriented silica fabric
  • Nozzle extension is extremely thin so it crushes on surface impact
  • Pintle tip erosion ended when the tip was changed to columbium alloy
  • Y-baffle on the injector face damps combustion instability
  • NASA ran two throttling concepts in parallel for about 18 months before choosing the variable-area injector
  • Spring-loaded throttle drives the engine to full thrust if electric power is lost
  • NASA Marshall says the Merlin 1D pintle injector was first used in this Apollo engine

Specifications

WhatValue
Maximum thrust (vacuum, full throttle position)10,500 lbf
Maximum nominal thrust (introduction)9,850 lbf
Throttle range10:1 (minimum about 10 percent of rated thrust)
Minimum throttle point10 percent of rated thrust
PropellantsAerozine 50 fuel and nitrogen tetroxide oxidizer, hypergolic
Specific impulse305 s (end of duty cycle)
Chamber pressure (full throttle position)103.4 psia
Ablative chamber area ratio16:1
Nozzle extension area ratioAbout 48:1
Approximate weight394 lb
Ablative duty-cycle capability1,000 s
Engines per vehicle1 in the Lunar Module descent stage
Design selectionNASA selected the STL design as primary in December 1964
First flight engine deliveredAugust 1966
First flightApollo 5 (LM-1), Saturn IB, 22 January 1968; first descent burn cut short after 4 s
First flight date1968-01-22

Materials in detail

Each material named in the sources: where it is used here, which other products use it, and its key numbers when its material page exists.

  • stainless steel (grade not stated)

    stainless-steel

    Used in 3 partsPintle tip, original · Flow-control valve bellows · Radiation heat shield foil

    Also in 10 other products
    Pumpkin CubeSat Kit structureRS-25 engineApollo Command and Service Module+7 more
    Material page coming soon

  • Titanium (commercially pure, grades 1 to 4)

    Used in 3 partsAblative-lined case to 16:1 · Structural shield · Exit-plane stiffening ring

    Density, CP grade 1
    4.51 g/cm³
    Density, CP grade 2 (bar and billet)
    4.51 g/cm³
    Density, CP grade 3
    4.51 g/cm³
    Also in 17 other products
    Proba-VProba-3 Coronagraph spacecraftCHEOPS+14 more
    Open material page

  • Aluminium alloy 6061

    Used in 2 partsFlow-control valve elbow, original · Flow-control valve elbow, redesigned

    Strength
    276 MPa yield
    Weight and stiffness
    2.7 g/cm3
    Heat conduction
    167 W/(m·K)
    Also in 9 other products
    SparrowKestrelOsprey+6 more
    Open material page

  • 7075-T73 aluminium alloy

    aluminium-7075-t73

    Used in 1 partGimbal frame

    Also in 1 other product
    Apollo Lunar Module (LM)
    Material page coming soon

  • A-286 steel

    a-286-steel

    Used in 1 partHead-end attachment bolts (36)

    Material page coming soon

  • Aerozine 50

    aerozine-50

    Used in 1 partFuel

    Material page coming soon

  • aluminide coating

    aluminide-coating

    Used in 1 partNozzle extension coating

    Material page coming soon

  • columbium alloy (grade not stated)

    columbium-niobium

    Used in 1 partPintle tip, qualification version

    Also in 4 other products
    Apollo Command and Service ModuleAtlas VRL10 engine+1 more
    Material page coming soon

  • Columbium alloy C-103

    niobium-c-103

    Used in 1 partNozzle extension skirt (16:1 to about 48:1)

    Also in 1 other product
    Parker Solar Probe
    Material page coming soon

  • Copper

    Used in 1 partPintle tip, copper-slug version

    Carry current
    58 MS/m (100 %IACS)
    Carry heat
    391 W/(m·K)
    Weight
    8.90 g/cm3
    Also in 7 other products
    CubeSat 101NASA small spacecraft structures reviewRockwest solar array substrate+4 more
    Open material page

  • Fabroid

    fabroid

    Used in 1 partGimbal trunnion bearings

    Also in 1 other product
    F-1 engine
    Material page coming soon

  • fiberglass wool

    fiberglass

    Used in 1 partRadiation heat shield spacer

    Also in 6 other products
    Rockwest solar array substrateApollo Lunar Roving VehicleApollo Command and Service Module+3 more
    Material page coming soon

  • metal felt (alloy not stated)

    metal-felt-insulation

    Used in 1 partLiner insulation layer

    Material page coming soon

  • nitrogen tetroxide

    dinitrogen-tetroxide

    Used in 1 partOxidizer

    Also in 2 other products
    James Webb Space TelescopeSuperDraco engine
    Material page coming soon

  • silica cloth / phenolic ablative

    silica-phenolic-ablator

    Used in 1 partAblative liner

    Material page coming soon

  • steel coated with molybdenum disulfide (inorganic binder)

    molybdenum-disulfide-coating

    Used in 1 partThrottle linkage pivot

    Material page coming soon

  • titanium alloy 6Al-4V (printed 6A1-4V in the source)

    titanium-6al-4v

    Used in 1 partChamber and exit-cone forgings

    Also in 1 other product
    Apollo Lunar Module (LM)
    Material page coming soon

Every part we have

Chamber, liner, nozzle extension, pintle tip, valve elbow, gimbal and heat-shield materials are stated in EngineHistory.org Part 9.42, NASA SP-2009-4545 and NASA TN D-7143. Venturi bodies, ball valves, injector sleeve and the helium and propellant plumbing are listed without a material.

Material IDs

titanium-6al-4vtitaniumsilica-phenolic-ablatormetal-felt-insulationa-286-steelniobium-c-103aluminide-coatingstainless-steelcoppercolumbium-niobiumaluminium-6061molybdenum-disulfide-coatingaluminium-7075-t73fabroidfiberglassaerozine-50dinitrogen-tetroxide
Thrust chamber8
PartMaterialFinish and standardMade by
Chamber and exit-cone forgings“machined from 6A1-4V titanium alloy forgings” titanium alloy 6Al-4V (printed 6A1-4V in the source)titanium-6al-4v — Source says the engine chamber and exit cone portions
Ablative-lined case to 16:1“an ablative-lined titanium alloy case to the 16:1 area ratio” titanium alloy (grade stated for the forgings only)titanium — —
Ablative liner“a high density, erosion-resistant silica cloth/phenolic material” silica cloth / phenolic ablativesilica-phenolic-ablator — —
Liner insulation layer“we had a lightweight metal felt material as an insulator outside of that in the chamber” metal felt (alloy not stated)metal-felt-insulation — —
Structural shield“that had a titanium structural shield around it” titaniumtitanium — —
Head-end attachment bolts (36)“36 A-286 steel” A-286 steela-286-steel — —
Exit-plane stiffening ring“an I-shaped titanium ring provided stiffness during handling, launch and boost” titaniumtitanium — —
Fuel barrier cooling“We used a barrier coolant in the engine because it was ablatively lined.” Not said — —
Nozzle extension2
PartMaterialFinish and standardMade by
Nozzle extension skirt (16:1 to about 48:1)“Columbium alloy C-103 was selected as the nozzle extension material” Columbium alloy C-103niobium-c-103 — NASA TN D-7143 calls it a sheet-metal columbium-alloy skirt; The Wah Chang Company supplied it
Nozzle extension coating“An aluminide coating provided oxidation resistance and high emissivity.” aluminide coatingaluminide-coating — —
Injector5
PartMaterialFinish and standardMade by
Pintle tip, original“The original injector pintle tip was made of stainless steel” stainless steel (grade not stated)stainless-steel — Eroded because of inadequate cooling
Pintle tip, copper-slug version“copper slugs were incorporated in the pintle tip” coppercopper — Phase A qualification design
Pintle tip, qualification version“used a columbium-alloy pintle tip” columbium alloy (grade not stated)columbium-niobium — Phase B qualification; no erosion occurred
Variable-area sleeve“The injector has a sliding sleeve that controls both the oxidizer in the middle and the fuel coming down the outside.” Not said — —
Injector face baffle“A Y-baffle arrangement was incorporated on the injector face to damp” Not said — —
Propellant flow control7
PartMaterialFinish and standardMade by
Cavitating venturi flow-control valves (2)“The flow control valves were non-redundant cavitating venturis with movable pintle sleeves.” Not said — —
Flow-control valve elbow, original“The original flow control valve (FCV) elbow was made of stamped 6061 aluminum sheet” 6061 aluminiumaluminium-6061 — —
Flow-control valve elbow, redesigned“The new elbow consisted of two pieces machined from solid 6061 aluminum” 6061 aluminiumaluminium-6061 — —
Flow-control valve bellows“stainless steel welded bellows” stainless steel (grade not stated)stainless-steel — —
Propellant shutoff valves“The propellant shutoff valves were ball valves.” Not said — NASA SP-2009-4545: quad ball valves on the fuel and oxidizer sides
Throttle actuator“built by Bendix Commercial Vehicle Systems” Not said — Bendix Commercial Vehicle Systems
Throttle linkage pivot“a steel bushing and a steel pin, both coated with molybdenum disulfide with an inorganic binder” steel coated with molybdenum disulfide (inorganic binder)molybdenum-disulfide-coating — —
Gimbal and heat shield5
PartMaterialFinish and standardMade by
Gimbal frame“machined from 7075-T73 aluminum alloy” 7075-T73 aluminium alloyaluminium-7075-t73 — —
Gimbal trunnion bearings“a spherical Fabroid bearing” Fabroidfabroid — —
Gimbal actuators“built by Airesearch Mfg. Company of Los Angeles” Not said — Airesearch Mfg. Company of Los Angeles
Radiation heat shield foil“stainless steel foil separated by fiberglass wool” stainless steel foil (grade not stated)stainless-steel — —
Radiation heat shield spacer“stainless steel foil separated by fiberglass wool” fiberglass woolfiberglass — —
Propellants2
PartMaterialFinish and standardMade by
Fuel“storable hypergolic Aerozine 50 fuel and nitrogen tetroxide oxidizer” Aerozine 50aerozine-50 — —
Oxidizer“storable hypergolic Aerozine 50 fuel and nitrogen tetroxide oxidizer” nitrogen tetroxidedinitrogen-tetroxide — —

What the sources leave out

No standards; the metal felt alloy, ball-valve and venturi alloys are not stated.

Where this comes from

5 pages from 4 websites

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Maker credit: TRW (Space Technology Laboratories) for Grumman and NASA. Collected from public pages and documents, checked 4 Nov 2026.

Published · Updated