Structure of the NASA Grumman Lunar Module

8/6/2019 Structure of the NASA Grumman Lunar Module

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STRUCTURE OF THE NASA/GRUMMAN LUNAR MODULE

The LM consists of a descent stage (with landing gear) and anascent stage. Provision is made for separating-the tages andthe interconnecting unibilicals at lunar launch. The weight ofthe LM at earth launch is approximately 32,000 pounds.ASCENT STAGE

The ascent stage is the manned portion of the LM spacecraft

and will carry two astronauts. Power and coasting descent, lunarlanding, lunar launch, power ascent, and rendezvous and docking withthe ~ommand/~erviceodules (cSM) are controlled from the crewcompartment. The crew compartment, a pressurized shell, is alsothe operations center for the astronauts during the lunar stay.The entire pressurized compartment of the ascent stage is calledthe cabin. In addition to the crew compartment, the ascent stageconsists of the mid section, the aft equipmentbay, tank sections,engine supports, windows, tunnels, and hatches. Pressure andtemperature within the crew compartment are controlled by theEnvironmental Control System (ECS)Crew Compartment (Cabin)

The ascent stage is constructed of aluminum alloy. A structuralskin surrounded by a composite layer of insulation and a thinaluminum skin provides thermal and micrometeoroid protection forthe astronauts. The outer skin is approximately three inches from

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the structural skin. The cabin (crew compartment) is a 92-inchdiameter cylinder stiffened by two-inch deep circumferentialframes. The frames are spaced approximately 10 inches apart and

are located between the structural skin and the thermal shield.The compartment has two triangular cabin windows in the front-facebulkhead, an overhead docking window on the left side, a forwardingress/egress hatch, an upper docking hatch, controls anddisplays, and items necessary for astronaut comfort and support.Midsection

The midsection is a smaller compartment directly behind thecabin. The ascent engine is aligned with the center of gravity inthe midsection. The ascent engine plumbing and valving isaccessible when the removable cover that extends above the deckin the midsection is removed. In addition, the midsection containsthe overhead docking hatch, Environmental Control System (ECS),and stowage for equipment that must be accessible to the astronauts.Tunnels

The upper docking tunnel, at the top centerline of the ascentstage, is used for docking when transposition is performed, fortransfer of two astronauts to the LM spacecraft after injection intolunar orbit, for docking after rendezvous in lunar orbit, and fortransfer of the LM crew and scientific payload to the Command Module.The ingress/egress hatch, at the lower portion of the forward cabinsection, is used on the lunar surface. Pressure-tight, plug-type

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h a t c h e s i n e ac h t u n n e l a r e m an ua lly c o n t r o l l e d , and a r e s e a l e d w i t hp r e l o ad e d s i l i c o n e e l a s t o m e r i c s e a l s . The i n g r e s s / e g r e s s h a t c hl e a d s t o a n e x t e r n a l p l a tf o rm upon which t h e a s t r o n a u t s s t e p a f t e rl e a v i n g and b e f o r e e n t e r i n g t h e LM.Af t Equipment Bay

The a f t equ ipment bay i s unpressur ized and i s a f t o f t h e mid-s e c t i o n p r e s s u r e - t i g h t b u lk h ea d. It co nta ins an equipment rac k wi thi n t e g r a l c o l d p l a t e s o n which e l e c t r o n i c r e p la c e a b le a s s e m b li es(ERA'S) a r e mounted. I t includes two gaseous oxygen (GOX) t a n k s f o ra s c e n t s t a g e m ain p r o p e l l a n t p r e s s u r i z a t i o n , i n v e r t e r s , and b a t t e r i e sf o r th e E l e c t r i c a l Power System (EDS).Tank Sec t ions

The p r o p e l l a n t t a n k s e c t i o n s a r e o n e i t h e r s i d e o f t h e mid-s e c t i o n , o u t s i d e t h e p r e s s u r i z e d a r e a . The t a n k s e c t i o n s c o n t a i na s c e n t e ng i ne f u e l an d o x i d i z e r ta n k s , an d f u e l , o x i d i z e r , an dhel ium tan ks f o r th e React ion Co ntro l System (RCS). Because t h er a t i o o f o x id iz e r t o f u e l i s 1 .6 t o 1 b y w e i gh t , t h e a s c e n t e n g in ep r o p e l l a n t t an k s a r e o f f s e t t o one s i d e t o m ai nta in t h e l a t e r a lce n t e r o f g ra v i t y on th e X-ax is . Two ECS wate r t anks a r e i n t h eoverhead of th e a sc en t s t ag e , and two gaseous oxygen s to rag e t anksa r e i n t h e a f t e quipm ent bay .Windows

Two t r i an g u la r cab in windows i n th e f ro n t - f ace bu lkhead of t h efo rwa rd c a b i n se c t i o n ( cr ew c om partm en t) p rov i de v i s i b i l i t y du r i ng

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de sce nt, lu na r land ing, and rendezvous phases of th e LM mission.The windows have a pprox imately two square f e e t of viewing are a anda r e can ted down t o t h e s id e t o permit adequate pe rip he ra l and downwardv i s i b i l i t y . Each window c o n si st s of two panes se pa rate d from eachot h e r and vented t o space environment. The ou te r pane i s thermaland rad iat io n-p rot ec t ive (Vycor) g l as s and th e inne r pane i s s t rong ,f l e x ib le (Chemcor) g l as s . A c lamp-type se a l con s i s t ing of a t e f l onj acke t su rround ing a m e ta l l i c sp r ing s ea l s t h e i nne r pane.

An overhead window, si m il a r i n con stru ctio n t o th e forwardwindows, i s on the l e f t s i de o f t he forward cabin s ec t i o n d i r ec t l yov er th e commander's head, and prov ides t h e commander with v i s i b i l i t ydurin g docking. The window con tains a s igh t in g r e t i c l e a s an a id i nl i n in g up th e CSM with th e LM spa ce cra f t . The f ie ld-of-view i s a tl e a s t p l u s o r minus l o0 each s id e .of t h e window c e n te rl in e , and minus

5O and p l u s 40 from t h e v e r t i c a l c e n t e r l i n e . V i s i b i l i t y i s obta inedby t h e commander le an in g backward and look ing up from h i s normaldu ty s ta t i o n . The approximate v i s i b l e opening of th e window i s5 inches wide and 1 2 inches long.Hatches

Two hatc hes i n th e asce nt s tag e permit i ng res s and egre ss t o andfrom the LM. The upper o r docking ha tch , used mainly f o r docking, i si n the midsec tion d i r e c t l y above the ascen t eng ine cover. Threerece sses i n the ha tch permit use of a l add er f o r observa tion whi le onth e lun ar sur fac e. The forward hatch i s beneath t h e cen ter ins t rument

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console (controls and displays) and is used for ingress and egresson the lunar surface. Each hatch contains a dump valve andmanually-operated single detent mechanism which preloads the hatch

against,its seal.Each hatch has a preloaded elastomeric silicone compound seal

mounted in the structure of the spacecraft. When the hatch isclosed, a lip near the outer circumference of the hatch enters theseal, ensuring a pressure-tight contact. Both hatches open inward,and normal cabin pressurization forces the hatch into the seal. Toopen either hatch, it is necessary to depressurize the cabinthrough the dump valve, and unfasten the latch.DESCENT ENGINE

The descent stage is the unmanned portion of the LM spacecraft.It consists of that equipment necessary for landing on the lunarsurface (e.g., landing gear) and serves as a platform for launchingthe ascent stage after completion of the lunar stay. In additionto the descent engine and its related components, the descent stagehouses scientific equipment to be used on the lunar surface, tanksfor water and oxygen used by the ECS, four batteries located in thebattery storage bay for the EPS, and six spare PLSS batteries.

The descent stage is constructed of aluminum alloy. Chem-millingis used extensively to reduce weight. The inner structural skin issurrounded by a composite layer of insulation and a thin aluminum-alloy.skin hat forms a modified octagonal shape around the descent.

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s t a g e an d t h e rm a l l y p r o t e c t s and i s o l a t e s t h e s t r u c t u r e . The beamsa r e of c o n ve n ti o na l s k i n and s t r i n g e r c o n s t r u c t i o n . . A l l j o i n t s a r ef a s t e ne d w i t h s t a n da rd m e cha ni ca l f a s t e n e r s . The spa c e bet we en t h e '

in te r s e c t i o n s of th e beams forms th e cen te r compar tment, whichc o n t a i n s t h e d e s c e n t e ng in e.

O u t r i gg e r s t h a t e x t e nd from t h e end o f e a c h o f t h e two pa i r so f beam s p rov i de sup por t and a t t ac hm e n t f o r t h e l a nd i ng ge a r l e gs .F our m ain p ro pe l l a n t t a n ks su r round t h e e ng i ne; two ox i d i z e r t a nksand two f u e l t a n k s a r e mounted w i t h i n t h e c r uc i fo r m s t r u c t u r e .S c i e n t i f i c equi pm en t, he l ium oxyge n, and w a t e r t a nks , t h e . l u n a rs u r f a c e a n t e n n as , EPS b a t t e r i e s , and PLSS b a t t e r i e s a r e i n t h e ba y sa d j a c e n t t o t h e p r o p e l l a n t t an k s.Landinq Gear

The l a n d i ng ge a r i s o f t h e c a n t e l e v e r t y pe . It c o n s i s t s o ff o u r s e t s o f l e g s c o n n e c t e d . t o o u t r i g g e r s t h a t e xt en d from t h e e nd so f t h e de sc e n t s t a g e s t r u c t u r a l beam s. The l e g s e x t e nd from t h ef r o n t , r e a r , and s i d e s o f t h e LM . Each l a n d i n g g e a r l e g c o n s i s t sof a pr imary s t r u t and footpad, a dr iv e-o ut mechanism, two secondarys t r u t s , two downlock mechanism, and a t r u ss . I n ad d i t ion , a l lf oo t pa ds , b u t t h e one on t h e forw ard l a nd i ng ge a r l e g , have l un a rsu r f ac e sen s ing probes ex tending be low each foo tpad . A l l s t r u t shave c ru sha ble shock absorb ing honeycomb in s e r t s . The pr imary s t r u t sabsorb compres ion loads . The secondary s t r u t s absorb compress ionand t e ns io n loads . The forward l and in g ge ar ha s a b o a r d i n g l a d d e r

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on the primary strut, which is used to climb to and from theascent stage forward hatch.

The landing gear is in a retracted position until shortlyafter the astronauts enter the LM during lunar orbit. The landinggear uplocks are then explos,ively released and springs in eachdriveout mechanism extend the landing gear and lunar surfacesensing probes. Once extended, each landing gear is locked inplace by the two down-lock mechanisms.Interstaqe Attachments, Umbilicals, and Separations

At earth launch, the LM spacecraft is within the SpacecraftLM Adapter (SLA) between the Service Module and the S-IV booster.The outriggers to which the landing gear is attached provide forattachment of the LM to the lower section of the SLA at theirapex. Before transposition, the upper section of the SLA is

explosively separated into four segments. These segments arehinged to the lower section and jettisoned.. After transposition,the lower section is released, separating the SLA and the boosterfrom the LM spacecraft.

Four explosive nuts and bolts connect the ascent and descentstages. At lunar launch, or for an abort, the two stages areseparated by firing these explosive devices. Interstage wiringumbilicals are explosively disconnected and hardlines aremechanically severed at stage separation.


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Electroexplosive Devices (EED)Explosive devices are used to release the landing gear for

deployment; to enable helium pressurization of the AscentPropulsion, Descent, or Reaction Control systems; and for stageseparation. The electroexplosive devices are exploded by astandard Apollo initiator controlled by switches on the ExplosiveDevices Panel.

- GAEC -

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Structure of the NASA Grumman Lunar Module