Apollo Experience Report Lunar Module Environmental Control Subsystem

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    N A S A T E C H N I C A L N O T E

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    APOLLO EXPERIENCE REPORT -LUNAR MODULE ENVIRONMENTALCONTROL SUBSYSTEMby Richard J . Gillen, Jumes C. Brady,and Frank Collier --,:-.,,i.I : ;.,*;cL;L,)-, , L! . ,: ... . ...,:-,* .,,a. I - . , -.: ' 7. :

    , I- - ., ' ? .j . 'unned Spacecrup Center : ^ ' ,Houston, Texas 77058

    N A T I O N A L A E R O N A U T I C S A N D S P AC E A D M I N I S T R A T I O N W A S H I N G T O N , D . C. M A R C H 1972

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    2. Sponsoring Agency Name and Address


    13. Type of Peport and Period CoveredTechnilal Note


    7. Key Words. (Suggested by Authods) 1* Oxygen Control Syste ms' W a t e r Management SystemsCabin Pres suriza tion and DepressurizationHeat Transport Systems * EnvironmentalAtmospher e Revitalization Control System

    - - -. Report No.NASA TN D-6724

    18. Distribution Statement

    2. Government Accession No.I

    19. Security Classif. (of this report)None None

    20 . Security Classif. (of this page)


    of Pages 22. Priced -. ~

    3. Reci?&nt's Catalog No, -. Repor1 DateMarch 19726. Performing Organization Code

    ~~ ~~

    8. Performing Organization Report No.MSC $29610. Work Urit No. ~914- 0- 80-10- 2i. Authods)Richard J . Gillen, Ja me s C. Brady, and Frank Collier, MSC9. Performing Organization Name and Address

    Manned Spa cecraft Cent erHouston, Texas 77058--- -11. Contractor Grant No.

    National Aeronautics and Space AdministrationWashington, D. C. 20546--L-14 . Sponsorib Agency Code

    iI c5 Supplementary Notes

    The MSC Director waived the use of the International System d un it s (SI) forthis Apollo Experience Report, because, in his judgment, us e of SI Units would impair the usefulnessof the report or result in excessive cost. -~

    6 AbstractA functional description of the Apollo lunar module environmental control subiystem is presented.Development, te st , checkout, and flight expe rienc es of the subs ystem are discussed; and the de-sign, fabricati on, and operation al difficulties asso ciat ed with the var iou s cohponents and subas-semb lies a r e recorded. Detailed information is relat ed concerning design & a g e s made to, andproblems encountered with, the various elements of the subsystem , such as he thermal controlwater sublimator, the carbon dioxide sensing and control units, the water sfct,on, and so forth.The problems a ssoc iated with water s teriliz ation, water/glycol formulation1 and mater ialscompatibility a r e discusse d. The correc tive actions taken a r e describe d wih tie expectation thatthis information may be of value fo r fut ure subsystems. Although the main xpwie nces descr ibeda r e problem oriented, the subsystem ha s generally performe d satisfactorilTin flight.

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    SectionSUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .DESCRIPTION OF THE LUNAR MODULE ENVIRONMENTAL CONTROLSUBSYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

    Atmosphere Revitalization Section . . . . . . . . . . . . . . . . . . . . . . .Oxygen Supply and Cabin Pressurization Section . . . . . . . . . . . . . . .Heat Transport Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . .W a t e r Management Section . . . . . . . . . . . . . . . . . . . . . . . . . . .

    TECHNICAL HISTORY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .H e a t Transp ort Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . .



    Atmosphere Revitalization Section . . . . . . . . . . . . . . . . . . . . . . . 17Oxygen Supply and Cabin Pressurization Section . . . . . . . . . . . . . . . 24W a t e r Management Section . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 8

    CERTIFICATION TESTING PROGRAM . . . . . . . . . . . . . . . . . . . . . . 34General Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34Feasibility Testing and Design Verification Testing . . . . . . . . . . . . . 35Qualification Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Integrated S ubsystems and Vehicle Testing . . . . . . . . . . . . . . . . . . 38

    VEHICLE AND ACCEPTANCE TESTING . . . . . . . . . . . . . . . . . . . . . 4 1FLIGHT EXPERIENCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2Lunar Module 1 (Apollo 5) . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2

    Lunar Module 3 (Apollo 9) . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2


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    Section Page43unar Module 4 (Apollo 10)

    Lunar Module 5 (Apollo 11) . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

    . . . . . . . . . . . . . . . . . . . . . . . . . .CONCLUDING REMARKS


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    Table PageI COMPONENT MAKEUP OF LM ECS ASSEMBLIES . . . . . . . . . . . 10


    Figure1 Atmosphere revitalization s ecti on simplified sche mati c . . . . . . . .2 Oxygen supply and cabin pres su riz ati on sectio n simplifiedschematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 H ea t transport section simplified schematic . . . . . . . . . . . . . .4 W a t e r management section simplified schemat ic . . . . . . . . . . . .5 Original design of inte rstag e disconnect . . . . . . . . . . . . . . . .6 Final design of inter stag e disconnect . . . . . . . . . . . . . . . . . .7 Cutaway view of w a t e r sublimator . . . . . . . . . . . . . . . . . . . .8 Expanded section of water sublimator . . . . . . . . . . . . . . . . .9 Coolant accumul ator (it em LSC-330-210) . . . . . . . . . . . . . . . .10 Simplified di ag ram of or ig inal des ign of redundant cooling loop/w a t e r system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11 Schematic diagr am of the LSC-330-192 package . . . . . . . . . . . .1 2 Centrifugal w a t e r se pa ra to r (ite m LSC-330- 109) . . . . . . . . . . . .13 Primary LiOH cart ridg e (item LSC-330- 1 2 2 ) . . . . . . . . . . . . .14 Suit-isolation valv e (it em LSC-330- 138) . . . . . . . . . . . . . . . .15 Simplified sys tem diag ram of a C02 sensor . . . . . . . . . . . . . .16 Lithium hydroxide cart ridg e performance curv es . . . . . . . . . . .17 Suit fan-motor assembly . . . . . . . . . . . . . . . . . . . . . . . .18 Cutaway view of suit fan motor . . . . . . . . . . . . . . . . . . . . .



    131 415

    16181919202 1222323


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    Figure19 Suit fan EM1 fi lt er configuration . . . . . . . . . . . . . . . . . . . . .2021

    Cabin repre ssur izati on and emergency oxygen valve . . . . . . . . . .Seat and seal details.abin repressurizatio n and emergencyoxygen valve(a) Configuration A . . . . . . . . . . . . . . . . . . . . . . . . . . .(b) Configuration B . . . . . . . . . . . . . . . . . . . . . . . . . . .(c) Configuration C . . . . . . . . . . . . . . . . . . . . . . . . . . .

    22 Cutaway view of oxygen demand reg ulator . . . . . . . . . . . . . . .23 Elevation sch ema tic of demand regu lato r/sui t cir cui t . . . . . . . . .24 Cabin dump and relief valve (i tem LSC-330-307) . . . . . . . . . . . .25 Burst-disk relief assembly

    (a) Normal s eale d position . . . . . . . . . . . . . . . . . . . . . . .(b) Open position . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 Descent wate r tank (item LSC-330-404) . . . . . . . . . . . . . . . .27 Water pr ess ure regulator.unctional sche mati c . . . . . . . . . . .28 Water bacteria filter locations . . . . . . . . . . . . . . . . . . . . .





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    APOLLO EXPERIENCE REPORTL U N A R M O D U L E E N V I R O N M E N TA L C O NT R OL S U B S Y S T E MB y R i c h a r d J. G i l l e n , J a m e s C. B r a d y , a n d F r a n k C o l l i e rM a n n e d S p a ce c ra f t C e n t e r

    S U M M A R YThe experien ces at the sub system level of th e lunar module environmental controlsubsystem are summarized to assist the operatio nal development of a future similar

    subsystem. The subsystem concepts used w e r e generally well established; however,the specific hardware designs were new.caused by so me relativel y common pro ced ure that had not been performed to the pro perquality level or to a requirement that, at that time , could not be defined in sufficientdetail.As a generalization, most proble ms wer e

    I N T R O D U C T I O NThe development of the lunar module (LM) environmental control subsystem ( E C S )required some improvements in the state of the art and w a s successfully accomplished.In the in te re st of prese rv ing hist ory and of perhaps benefiting desig ne rs of future sy s-

    tems, som e of the development pro ble ms a r e recounted. It should be noted that manyof the pro blems a r e of a subtle type that appear only after the hardware is used re-peatedly in many different ways. In many cases, th e pro ble ms were resolve d by chang-ing a pro ced ure of us e ra th er than by redesigning the item. This approach w a s usedwhen it w a s felt that the unit w a s ver y sound and that the benef it of experi ence with aless-tha n-perf ect unit would be bet ter than rebuilding to get a new, untried, "perfect"device with possibly new problem s. The experience gained fr om us e of the ECS is aver y significant and positive asset.D E S C R I P T l O N OF T HE L U N A R M O D U L E E N V IR O N M E N T A LC O NT R OL S U B S Y S T E M

    This section des crib es the lunar module ECS f rom a functio nal standpoint. TheECS configura tion s of the L M - 3 , L M - 4 , and L M - 5 were all substantially the sa me withthe following exceptions.1. The L M - 3 vehic le was equipped with developmental flight instrumentation, andthe ECS contained additional equipment-cooling prov isions f or thi s instrumentation.

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    2. The LM-5 (Apollo 11) lunar landing vehicle and later vehicles included suit-liquid- cooling pro vi sio ns to enhance the crewman - cooling capability. The se provisio nswe re substituted fo r the cabin heat-exchanger as semb ly.The complete sche mati c diagr am of the LM-5 ECS is shown on pri me contracto rdrawing LDW 330-55000, which can be obtained fr om the NASA Manned Spacecr aft

    Center (MSC), Houston, Texas. Thi s drawing shows pa rt num bers and detailed fluidand electrical schematics.In sum mary, the LM-5 ECS was divided into the following functional sections.1 . Atmosph ere revitalization section (ARS)2. Oxygen (02) upply and cabin pressur izati on se ction (OSCPS)3. Heat tran spor t sec tion (HTS)4. W a t e r ( H 2 0 ) management sect ion (WMS)

    A t m o s p h e r e R ev i t a i z a t on S e c t o nThe ARS (fig. 1) removes heat, moisture , odors, and carbon dioxide (COz) fro m

    the suit ci rc uit of the two astro nau ts and provides the re quir ed atmosphe re circulation.One of the two suit fans circu late s the warm, moist, suit-circuit gas es through thebackup heat exchanger to the pr imary heat exchanger. The backup unit is a suit gas-to-water sublima tor and is used only if the prim ary coolant cir cuit fails. The primaryheat exchanger is a gas-to-coolant fluid (water/glycol) unit. The gas, which has beencooled below the dewpoint, ent ers the selected water-gas centrifugal sep arator. (Anidentica l unit is provided for redundancy. ) These rotary devices are powered by thesuit-circuit gas strea m. The water is coalesced and thrown to the periphe ry where itenters a pitot tube, through which the water is delivered first to the WMS and then tothe HTS fo r us e in heat rejection.

    The suit ga s may next be reheated, if re qu ire d, by wa rm water/glycol in a re-generati ve heat exchanger a ctivated by a manual valve. The rege nera tive heat ex-changer is functional only on the pri ma ry cooling circ uit. Each crewman has asuit-isolation valve, which is normally open except during extravehicular operations.These fast-acting suit-isolation valves c lose automatically if the suit-circuit pr ess urebecome s dangerously low. This safety fea tur e functions if the spa ce suit of one crew -member is torn or otherwi se malfunctions while the cabin is depressu rized. The crew-member with the good suit c an then take cor rec tiv e action.Flexible ho ses d eliv er the conditioned gas to each astronaut and retur n the gas tothe ECS fo r proc essi ng again. The gas is normally diverted to the press uriz ed cabinfo r circulation and is returned to the A R S hrough the cabin-gas ret urn check valve.The gas next en ter s the prim ary replaceable filter car tri dge that contains lithium hy-droxide (LiOH) to remo ve carbo n dioxide and activate d charco al to remo ve odor. Asecondary filter cartridge, which is identical to the cart ridg e used in the backpack or


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    e x c h a n g e r

    I I


    IrA c c u m u l a t o r1 W ater- P u m p

    cI IRegenera t i ve-r h e a t e x c h a n g e rI T I 141 IL I o l a t i o n

    va l ve' t f

    I -I I Rel i e fvalvec0 2s e n s o r

    I I

    e x c h a n g e r

    s u b l i m a t o r

    I I

    Fa n

    I I

    Figure 1.- Atmosphere revitalization section simplified schematic.

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    portable life support syst em (PLSS), s normally used only when the primary cartridgeis being changed. This car tridge change is preplanned to occur at a convenient time inthe mission. A carbon dioxide sen sing device is included in the ARS to assess the con-dition of the car tri dge s. Other it em s of inst rumentat ion are provided to e ns ure optimumsubsyste m operation and safety.Supplemental cooling al so is provided to the astronaut s fo r periods of high meta-bolic heat rates by circ ulat ing cool wate r through pla sti c tubing, which is a part of theundergarments. The sa me undergarments provide cooling during extravehicu lar opera-tions. The liquid-cooling assembly uses a pump, an accumula tor, and a temperaturecontrol valve to bypass the cooling water around the liquid-to-liquid heat exchanger.

    O x yg e n S u p p ly a n d C a b i n P r e s s u r i z a t i o n S e c t i o nGaseous oxygen is stor ed in the L M descent stage fo r use during the descent andlunar stay phases, and a sm all amount of gase ous oxygen is stored in the LM ascentsta ge for u se during the lunar a scen t phase and during rendezvous and docking with the

    command module. A sim dif ied schematic of the OSCPS s shown in figure 2. The

    P L S S

    2800-psi descent oxygen ;upply is regulatedto 900 psi by redundant regulators. R e-dundant bypass relief valves protect thedescent oxygen tank against overpres-suri zation. Redundant low-rate over-board relief valves protect the sectiondownst ream of the re gul ato rs against ex-cessive pressure caused by a defectiveregulator o r by flow through the bypassrelief valves. A reseating burst diskprovides high-rate relief for failed-openregulators.

    The descent oxygen supply and theredundant asc en t oxygen supply are mani-folded through manual shutoff valves lo-cated in the cabin. The shutoff valves a r emechanically interlocked to prevent thepre mat ure us e of ascent oxygen. The900-psi descent oxygen is available fo rbackpack rech arge through appropriatevalves and fittings.Suit-circuit absolute pressure (and,therefore, cabin absolute pre ssu re) iscontrolled by two manually selected, re-dundant regulators, both of which a r enormally activated. These automaticaneroid valves have elec trica l interlocks

    To su i t loop

    repressu izat ion


    oxygen tankscent oxygen tankAscent stage lnters tageDescent stage ?disc onnec t

    relie f valve diaphragmHigh-pressure I 1assembly


    0escent oxygen tankR denotes redundant component.

    Figure 2. - Oxygen supply and cabinpressurizatio n section simplifiedschematic.with the cabin repr essu riza tion valve to perm it cabin depr essu rizat ion when desired.The cabin repres suri zatio n valve can be manually or automatically actuated to re st or e


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    cabin pre ssu re rapidly. A cabin relief and dump valve is provided on both LM hatchesfo r automatic ov erpre ssur e control and for controlled cabin depressurization.H e at T r a n s p o r t S e c t i o n

    Heat fr om various Sources is rej ect ed by the sublim ation of w ater ( ice ) to spac evacuum. Two closed loops ca rr y a circulat ing solution of 65-percent water and35-percent corrosion -inhibited ethylene glycol through heat exchangers and elect roni cscold plates and through the respective sublimators. Figure 3 is a simplified schematicof the HTS. The water /glycol is circu-lated at the nominal 250-lb/hr pr im ar yloop flow ra te by one of two pumps. Thesu it heat e x c h a n g e r and the low-temperature electronics cold plates arecooled in paral lel. Next , the flow pas sesto the liquid-cooled-garment h eat ex-changer and then to the high-temper atureelectronics cold rails. These cold platesand cold rails are carefully arran ged in aseries-parallel network with necessaryflow co ntrol orificing to provide the properunit.


    ther mal environment for each electronic recirculator assemblyThe primary sublimator rejects thecollected heat, and the coolant abso rbs the

    R denotes redundant component.aste heat from the batte ries before re-turning to the filte r and to the pump, atwhich point the cir cui t is complete. Thesecondary coolant loop is substantiallythe same , except that the primary guid-ance equipment is not cooled and only asingle pump is provided.sublimator and not by the s econdary coolant circuit .

    Figure 3. - Heat transport sectionsimplified schematic.As previously noted, the suit loop is cooled by a backup

    W a t e r M a n a g e m e n t S e c t i o nThe WMS s schematically illustrated in figure 4. The L M water is store d in onelarge descent tank (332-pound capacity) and two ascent tanks (42-pound capacity each).Each tank has a bladder pressurized with nitrogen ( N 2 ) to expel the water in z ero grav-

    ity and to for ce the water upward fro m the descent sta ge in one-sixth gravity during thelunar stay. Series-redundant water pre ss ur e regulators provide reduction of the pres -sure to a level compatible with sublimator requirements and permit suit-circuitcondensate to be effectively pumped by the water sep ara tor s. A backup set of series-redundant water pr ess ure regulators is provided fo r seco ndary coolant-loop operation.

    The water used for PLSS refill, fo r drinking, fo r food preparatio n, and for fireextinguishing is tapped off through a disp ense r located upst ream of the pr es su re


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    regu lato rs. Water and iodine are mixedat the ti me of LM wat er loading to give alow iodine concentration for bac teri acontrol.Reclaimedscent H@ tanks-

    T E C H N IC A L H I S TOR YThe technical history is presentedfirst fo r so me gene ral item s that apply tothe system as a whole or for i tem s whichcut ac ro ss seve ral subsystems. Next, thehist ory of subse ctio ns is given fo r the HTS

    R denotes redundant component. the ARS, the OSCPS, and finally , the WMSNo attempt was made to arra ng e these byescent Hf l tank severi ty of the problem. All proble mswere significant at the time they werereported.

    Figure 4. - W a t e r management sectio nsimplified schema tic.

    GeneralIntersta ge disconnects. - Interstage disconnects (LSC- 330- 505 ) are used betweenthe ascent and descent-stag es o provide a flow path for high-p ressure oxygen fro m thedescen t-stage oxygen. tank to the environmental con trol su bsy stem in the ascen t st ag eand to provide coolant flow paths for the descen t-stage cold rails. Normally, servicefluid lines between space craf t stag es ar e routed through cut ter asse mbl ies if the space-craft s tages a re required to separ ate during mission life. A t the tim e of separati on ,

    the cutter assembly shea rs the lines (ensuring safe separa tion) and allows exter nalleakage to occur at the shea red interf ace s. Shearin g of the glycol lines would have re -qui red the installation of a shutoff valve (manual or elec tric al) in the supply to thedescent st age and a check valve in the ret urn line to prevent l oss of glycol after sepa ra-tion. Because of possib le impact ignition, it w a s als o considered unsafe to she ar theoxygen line that contained 900-psia oxygen. The glycol coolant loop is serviced at thebuilde r's plant; and, bec aus e nor mal ground checkout req uir ed sepa rati on of the asc entdescent stages, it w a s mor e feasible to use disconnects to eliminate deservicing andrese rvic ing of the coolant. Fur the rmor e, the disconnects provide an automatic sealto prevent l os s of fluid fr om e ithe r half of the disconnect aft er staging.The intersta ge disconnects were designed without retention mechanisms so they

    could be simply pulled a pa rt.descen t-stage sep ara tion . Coupling of the ascen t (st ru ct ur e mounted) disconnect halfto the descent (s tru ctu re mounted) disconnect half is mainta ined by squ ib bolts, whichconnect the two stages .This method ensured minimum resi stan ce to ascent/

    The original design used a single compression seal and was successfully certifiedwith flight bracke t asse mb lie s. Fr om the beginning of vehicl e asse mbl y and checkout atthe manufacturer's plant, it was noted that this p arti cula r design w a s susceptible todamage during vehicle installation unless extr eme care was taken. Subsequent installa -tion efforts at the NASA John F. Kennedy Space Cen ter (KSC) ver ifie d the damage


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    susceptibility; and it w a s necess ary to add a redundant seal (fig. 5 ) to the LM-3, LM-4,L M - 5 , and L M - 6 coolant-loop disconnects to ensu re no exte rna l leakage. The redun-dant seals w e r e not used on the oxygen disconnects because the higher pr es su re(900 psia) provided a much better seal than the lower pres su re (20 psia) glycol dis-connects. It w a s al so found that th e redun dant-s eal method used was ineffective atpres sure s above 5 0 psig. Starting with the L M - 7 vehicle, a redesigned disconnect(fig. 6), which had built-in redundancy and also provided better protec tion to the se alin gsurfaces, w a s used. This design was certified by test and installed in the remainingvehicles. To date, this design has shown a high r es is ta nc e to handling and installationdamage.

    LSC-330-505-5 redundant sealused on coolant loop disconnectsfo r LM-3, LM-4. LM-5. andLM-6 vehicles

    Figure 5. - Origin al design of inte rsta gedisconnect.

    Primary poppet seal

    Secondary poppet seal

    Primary exterleak path sealSecondary exteriorleak path seal

    Figure 6 . - Fin al design of int erst agedisconnect.Battery configuration change. - The earl y L M vehic le design depended on fu elce lls fo r el ectr ical power generation.oxygen) wer e to be s tore d in the su per crit ical state, and it w a s planned to us e th ecryogens as a heat sink.

    changed to bat teri es, the hydrogen w a s eliminated, and the oxygen sto ra ge method waschanged to high-pres sure gas. The ECS require ments and responsibilit ies wer echanged significantly at this tim e (approximately March 1965) . High-pressure gaseousoxygen pr ess ure regulat ors and relief valves wer e required, and the high-pressureoxygen storage tank in the descent stag e became a new ECS responsibility. Previously,the ECS oxygen requir eme nts had been supplied fro m the common cryogenic oxygen

    The reactan ts for the fuel cells (hydrogen and

    After approximately 2 y ea rs of design work and studie s, the power sour ce was


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    descent-stage tank. While th es e changes we re being considered and identified, a seriesof studie s was performe d to determin e the new requ ireme nts f or sizing water andoxygen consumables. Mission pa ra m et er s we re updated and varied to examine and tounderstand the vehicle and mission penalties ass ociate d with the changes. Implementa-tion of the changes produced a la rg e impact upon the ECS. New designs were requi redfor a la rg e descent-stage gaseous oxygen tank (approximately 48-pound capacity at3000 psi) and two ascen t-stage gaseo us oxygen tanks (approximately 2. $-pound capacityeach at 900 psi). New designs wer e required fo r the high-p ressur e gaseous oxygenpre ss ure regulator and for the relief valves in the descent stage. Changes to the watertank designs wer e not required. In response to the late start, all of these changes wer epursued vigorously to sh orte n the development cycle.

    In contrast to the large impact that the change to ba tte rie s had on the ECS, th erewas an early change to incorporate a redundant cooling loop. The redundant-loopchange affected many hardw are i te ms but was implemented short ly afte r the subcon-tr ac ts wer e initiated, and this change was easily accommodated.Reliability conside rations. - Reliability analy ses perform ed for each subsystem

    by the contractor r esu lted in F ai lu re Mode and Effect Analyses and Single Fail ure PointSummary documents. During the cou rse of the contract, the se we re periodically re-fined and improved in detail. The degree of detail was upgraded as more and mo reknowledge of the hardw are was gained. The se documents se rv ed the useful purpose ofidentifying fo r management those a re a s of subsy stem design in which operational ri sk swould be encountered and al so identified the seve rity of the risk. For example, mostequipment was adequately backed up by redundant components, and fa ilu re would re su ltin nuisance-type situations rat he r than in hazardous conditions. The se documents dealtwith design and operations and wer e not of the probability ass es sm en t type. The cause -and-effect type of re liabil ity approach was found by management to be more usefu l thandealing strictly with ab st rac t numbers of mean tim e to failure.The reliability pro gr am als o included shelf- life control. Prob lems wer e en-countered in implementing effective shelf-life control. The original plan by which thisprogram was established failed to se t up str ict controls, such as periodic checking ofthe st or ed equipment. Based upon observations of shelf-life control, i t is felt thatfuture programs should implement s tr ic t controls earl y in the pro gra m by providingfo r periodic testing or per iod ic opera tion of equipment, by applying a conscious con-sidera tion of shelf life when evaluating each engineering change (after configurationcontrol is established), and by requ iring that positive actions a r e established fo r allhardware when the shelf-life limitation is reached.The failure reporting portion of t he reliability pr og ram al so had some significantasp ects . Every out-of-specificaticn condition was form ally documented fr om the ti me

    manufacturing of a component was completed. Thus, development probl ems and in-pr oc es s checks and calibrations wer e not reported, but all acceptance t es t (and sub-sequent) problems w er e reported. A repo rt was accepted and closed only when acomprehensive analys is of the cau se was documented and corre cti ve action was ini-tiated . The preva iling philosophy of "every fa ilu re has a cause" required a compre-hensive investigation into the fa ilu re causes. Accurate repor ting proved helpful manytimes in r eferrin g back to a problem. All failure re po rt s we re reviewed by top man-agement at the Flight Readiness Review and requir ed c los ur e or a satisfactory explana-tion to remove constraints to flight release. A fa il ur e re po rt "explanation" meant that,

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    although the failu re was not completely closed, th er e was a satisfactory explanationfor a specific spacecraft as a re su lt of e xt ra testing, isolation of the problem to a spe-cific lot, and so forth.Flight instrumentation. - The operational instrumentation installed in the ECSprovided minimum information concerning perfo rmance. The vehicle penalties fo r

    instrumentation were significant, and only data that were consid ered to be vital wereprovided. The instrumentation requi reme nts w e r e established early and included anumber of valve position indicators.caused a closed or open circ uit to stimulate a tele met ry signal, depending upon theposition of a valve handle. In retr osp ect , the se data have not proven ver y useful; andthe weight, power, and volume penalties could have been bet ter allocated to instrume n-tation fo r subsystem performance. The valve position indicators are perhaps usefulwhere a n inadvertent elec tric al actuation is possible; but, f or manually selected valvepositions, they are redundant to a voice link fo r verification of p rop er subsystemconfiguration.

    These valve position indicators w e r e switches that

    Very sm all plunger travel w a s used to actuate the switches, and this made pre-cision alinement neces sary. The switch design w a s al so found to be suscep tible tochange in perfo rmance (actuation for ce) with a change in ambient pr es su re . Manyswitches we re found to have defective in terna l s prin gs, which changed theirperformance.These switches were a ls o difficult to install properly in som e valve designs. Inone application (suit-isolation valves), more than a half dozen indirect measurem ents(with cumulative to leranc es) were required for the switch installation because, as aresult Qf inaccessibility, there w a s no simple, direct way to measure the installationshimming required.Several switch applications were deleted from the s ystem where operational ex-perience indicated that the function provided could not justify r etention of the device.

    In other cases, a change w a s made to inc rea se the overtravel, giving more positiveswitch action.Modular concepts. - Modular packaging concepts we re used in s eve ral placeswhere cert ain groupings of equipment appeared desir abl e.drawbacks experienced are discussed. Some of the advantages andThe major package in the LM ECS w a s the suit-circuit assembly (LSC-330-190package), which contained the nec ess ary a tmosp here proces sing equipment- uch asvalves, heat exchangers, carbon dioxide removal elements, sui t fans, and instrumen-tation- or the suit circuit. Interfaces w i th the electrica l power system, with telem-etry signals, with the wate r sys tem , with the coolant sys tem , with the cabin gas, with

    the suit gas umbilical hoses, and with the oxygen supply were required. A summary ofcomponents and interfa ces fo r the ECS packages is given in table I.The suit-c ircuit assembly was densely packaged to accommodate the requiredhardw are in the allotted space. U s e of the modular concept was ne ces sary because ofthe weight and volume constr aints, but thi s led to a number of pro blem s throughout thepro gram. Whenever equipment was modified o r changed, the certifi cation testingprogram was modified accordingly. "Delta" qualification runs , which cause d the sa me


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    Heat exchangerWater separatorFan and motorValvePressure regulatorLiOH canisterLiOH cartridge


    Transducer and switchFluid interfaceconnectionPump and motorAccumulatorFlow control orificeVoltage regulato rFilterTotal pe r assembly

    Environmental control sub sys tem package, LSC-330-190




































    basic package to be subjected to a number of diffe rent qualif ication test runs, werereq uire d in many instan ces to qualify the rev ised equipment. The interdependence ofpackaging and functional effects was adequately demo nstrate d by te st s, but a gre at num-ber of tests and a considerable amount of t ime were required.It had been planned to repl ace the e nti re package in th e field if any componentrequ ired change fo r any rea son . Changing an enti re package w a s a fair ly lengthy proc-ess, and a large number of t est s were require d to verify that all the components withinthe replacement package were functioning proper ly aft er installation. For this reason,the prac tic e of changing individual components with the package install ed, whe reverpossible, was adopted. This pra ctic e, which w a s successfully performed on a numberof occasions, saved much time in the vehicle cabin and thus generally avoided schedule


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    sli ps. Because of the dens e packaging, however, remo val and rep lacement of compo-nents within an installed package was a difficult task. On each occasion, prac tice runswe re made on a bench package at the subcontractor 's plant to establish a suitable pro-ced ure (to ens ure tha t no damage would be done) and to tr ai n the per son who w a s tomake the change. The exact proc edur e to be followed in the flight vehicle wa s developedand, in a sense, "qualified" befo re authorization was given to proc eed with replac ingthe flight item. These proc edur es included the nec essa ry reverific ation tests.

    Dense packaging cau sed practi cal pro blems that re quir ed the expenditure of extratime and effort as the penalty fo r minimizing cabin volume usage. It is not reason ableto ass um e that complex packages can be installed and never req uir e a componentchange; therefore, it app ear s that the tra de between ti me and packaging conveniencemus t always be carefully weighed and understood. Packaging w a s le ss complex forother ar ea s. (Coolant pumps, filters, and valves were designated as the LSC-330-290package; the cabin oxygen control module, consisting of valve s and pr es su re regu lato rs,was ca lled the LSC-330-390 package; water sy stem valves and regulators were desig-nated the LSC- 330-490package; the high-pr essu re oxygen control module with pr es su reregulators and relief valves w a s designated the LSC-330-392package; and the liquid-cooling provisions fo r the crew men w e r e designated the LSC-330- 92 package. )Pump packaging w a s quite successful with no particular complications. The oxy-gen and water module packages used complex castings, into which the nec essa ry activeelements w e r e fitted. Int eg ral manifolding and the lack of numerous tubes and fitt ingsa r e the main features of the casting approach. This concept worked quite well fo r theoxygen modules . However, for the water system module, a number of design changesw e r e nece ssar y; and the inflexible configuration caused by the casting concept led toadd-on valves, capped boss es, and si mi la r modifications to achieve minimum-impactchanges. For the wate r sy ste m module, the us e of a casting proved to be an encum-bran ce because the casting design became fixed before the design requ irem ents beca mefi rm . However, this problem w a s not experienced with the oxygen modules , and thescrew-in components wer e very easily replaced and retested.

    H e at T r a n s p o r t S e c t o nWater/glycol formulation. - The coolant fluid caused s ev era l problems even thoughthe application-was-considered to be well within the st at e of the ar t. Initially, the fluid,which w a s formulated to give the following mixture, w a s specified to be the sa me asthat for the command and ser vi ce module.

    Parts by weight. ..MaterialEthylene glycol 62.5Distilled w a t e rTriethanolamine phosphate 1.6

    As necessary to make 100 par ts

    Sodium mercaptobenzothiazole (NaMBT) 0.9


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    the main problem see med to be whether the particl es would degrade s ys te m flow rates,clog the system f ilte r or system orifices, or abrad e the pump. Bench testing was con-ducted with two different pump-filter packages fo r endurance; and, although the filterplugged both t im es and the automatic relief valve bypassed the filter, the pumps per-formed normally.crystal s were observed to be ra ther fragile in cha ra cte r and apparently were readilypassed through the pumps. N o clogging of the flow-balancing ori fices oc cur red duringbench tests. Gr oss precipitate was forme d in the laboratory, and the fragile nature ofthe precipitate allowed it to pa ss through the finest orifice s used with only a minutepres sure head. Based on all these tests, the LM-5 vehicle was flown with the c ry st alspresen t, and no problems w er e encountered.

    The pumps w ere dismantled and showed no unusual wear. The

    Subsequent vehic les w er e drained, flushed thoroughly with water and with isopro-pyl alcohol, then refilled with water/glycol formu lated with the previously used com-mer cial grade inhibitor. This fluid has again proved mor e's tabl e and is a satisfactorycoolant. The inves tigations showed clearly that sub tle amounts of unknown "impurities"other than sodium sulfite in the co mme rcial product have a crystal-inhibiting andcrystal-dissolving action. A contract (NAS 9-9956) was let to continue the investigationinto determining the nature of these impu rities and als o to investigate what sy stem ef-fec ts (flow rat es , etc. ) may cause disulfide cr ysta ls to form.

    Sublimator developments. - The development of the sublimators for heat-loadreject ion caused probably-most significant design problems of the LM ECS.relativ e simplicity of sublim ator operation might give a misleading impr ess ion of thedifficulties involved in th e design and manufactu re of the device. Simplicity is apparentin the cutaway view (fig. 7 ) and in the expanded section shown in figure 8. The earlyproblems were difficulty in brazing the porous plates and in achieving a good bond with-The

    but plugging the p or es with b ra ze material.techniques. The ea rly units we re alsoshowing performance degradation rates(with usage ti me) tha t we re not encourag-ing; and, also, the initial perfo rmancewa s below expectations. Lo ss of porosi tyof the plates directly reduc es perform -ance, and this seem ed to be the problem.

    Porou s plates with higher permea-bility w e r e used; and severa l other im-provements in fabrication were tried,including welding of fins to the porousplates to eliminate brazing problems.Performance improvements we re made byincreasing the density of hea t-transferfin s in the coolant pas sag es. Additionally,to meet performance requirements, it wasrequired to control the installation of po-rou s plates s o that the finer p ore orienta-tion was always facing the st ea m ventpassage.

    Materials were changed-as were brazing


    passage)- ' Steampassage

    Figure 7 . - Cutaway view of watersublimator.


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    End sheetCoolantParting sheetEvaporantPorous plate

    Steam passageiorous plateEvaporant



    EvaporantPorous plateSteam passage

    Figure 8. - Expanded section of watersublimator .

    Chlorine was added to the sto redwater to act as a biocide. The chlorinatedwater produced unacceptable perform ancein the sublimators. Formation of achlorine-based residu e on the steam-pas sage sid e of the porous plate s caused adepression of the freezi ng point, and wate rbreakthrough occur red. Testing w a s per-formed by using iodine as the biocide, andthese tests showed that iodine w a sacceptable.Perfor manc e degradation history w a staken fr om measu red data on a Saturn sub-limato r used fo r instrument unit electroniccooling. Degradation w a s found to occur asa re su lt of the slow accum ulation of co rro-sion products during storag e. Degradationduring operation w a s found to be re lat ed tothe cumulative wate r quantity boiled pe rsqua re foot of su rfac e, and thi s w a s causedby corrosion and by the slow blockage ofpores with particulate matter.To guarantee specified performancea t the tim e of a mission, a higher perform-ance is required at the time of acceptancetesting. The magnitude of thi s performanc e marg in w a s established by tests and anal-yses. The most sensitive par am eter s were the duration of operat ion and the quantity ofwater used per s qua re foot of sublimation surface. The sublimator plates and ass em-blies were stored in a dry nitrogen environment to minimize degradation fo r as much ofthe manufacturing and checkout process as possible.

    Flight experience with the sublimat ors has been very satisfactory on L M flightsto date. Perfo rmanc e has been very stable and has followed preflight predictions.Quick disconnects. - Quick disconnects were used in the heat trans port section fo rconvenience in making and breaking seve ral connections. Seve ral probl ems that werecaused by lo ss of the lubricant within the connecto rs occu rred.Whenever a draining operation w a s required, isopropyl alcohol w a s used followingdraining to flush the residu al water/glycol f ro m the syste m. Removal of the lubricantby the alcohol prevented free action of the moving par ts and thereby caused incompletesealing. Leakage resulted when these units wer e subjected to gaseous leakage checks,although it w a s fel t that the liquid coolant would not leak because of the lubricity prop-erties of the liquid. However, in practi ce, any unit showing gaseous leakage w a s re-moved and replaced to guarantee a leak-free syste m. To prevent replacement time,the ground-support equipment interface quick disconnects wer e redesigned t o allowreapp lication of lubricant following alcohol exposure.


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    It w a s al so found that the plastic izer in Buna-N ela sto me rs used in the quick dis-connects w a s shrunk by the isopropyl alcohol aft er a ce rta in period of alcohol exposu reas dete rmin ed by testing.the cri tical exposure times.The alcohol flush times were controlled to values less thanAccumulator designs. - A water/g lycol accumul ator that would maintain accepta bleleakage at the flanges proved difficult to build. An accumu lator unit is i l lustrated in

    cutaway view in figure 9. The diaphragm for ms the sealing gasket, and slight irreg u-larities in the molded diaphragm resu lt inuneven and inadequate sealing forc es. Thesize of the flange groove was r educed toachieve the prop er bead squeeze. Themet al shou lder on the flange had to be re-phragm squeeze. The us e of highertorquing of the sc re ws on the retain ingring around the flange was a ls o imple-mented. The sc re ws had to be added be-ca us e high torquing of the ret aining rin g *itself cre ate d re lat ive displacement of thetop and bottom shells, which tended towrinkle the diaphragm. After the scr ew swe re added, leakage problem s seem ed tobe w e l l in hand.

    designed to contr ol the amount of d ia- el r i n g

    F lu idPO rt

    Approximately a year later, a la rgecrack w a s discovered at the angle section Note shownof a retainin g ring. Investigation into thisproblem reve aled that the mate rial (alu-stresses above those allowed fo r stress-corr osio n control. All accumu latorswere recalled, the ring mate rial w a s changed to aluminum alloy 7075T7351, and thecro ss sect ion w a s thickened in the affected area to reduce stress levels .

    Figure 9. - Coolant accumulator (ite mminum alloy 2024T4)w a s subjected to LSC- 30- 210).

    It is important to note that the s tre ss- cor ro sio n problem was brought on by th esolution of a totally unrelated problem. Higher and higher st re ss e s w e r e imposed onthe unit by inc rementa lly incre asin g the s queeze on the diaphragm bead fo r seal ingpurposes. Prob lems with stress corrosio n were common in a number of subs yst em sin the LM. In this case, the material in all of the glycol accumu lator retainin g rin gsw a s greatly overstressed; however, only one unit failed. It appears that stress corro-sion may or may not occur even when the st re ss es are well above the "threshold"values. However, the uncertainty associat ed with s tr es s corr osio n is such that ad-herence to threshold s t re ss levels is the only safe approach.Sublimator breakthrough_ _ roblems. - The initial redundant cooling loop containedno water/glycol accumulator. An "accumulator effect" was designed into the sy stemby an interface with the water sy stem . This design requ ired that the secondary coolantloop be maintained at a subatmospheric pre ssu re to accommodate expected therma lexpansions and contractions and to provide a pr es su re compatible with the water sys-tem in case the secondary cooling s yst em were activated.


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    Figure 10 ill ust rat es the genera l arrangem ent of the redundant cooling sys temand the water syst em. The interface of these two syste ms is at the punctu re disk, andactivation of the sec ondary cooling loop included puncturing of thi s disk so that the wate rsyst em could ser ve as an accumulator. The us e of ganged valves ensure d that theselection of the proper w ater valv es drove a pointed plunger through the puncture disk.Because this was an irr eve rsi ble step that left the s ys tem s with so me intermixed fluidand required spec ial cleaning, the actuating mechanism w a s arranged to prevent in-adver ten t puncturing of the disk. Despite thi s desig n and the us e of warning flags dur-ing ground operations, ther e were seve ral instances early in the pro gra m when thedisk w a s punctured during factory operations.



    Watersupply48 psia lfu l l l12 psia l empty)

    6 psiaaterpressureregulation coolant-loop

    Secondarysuit -circuitWater sublimator

    Check +, cwlant-loopondensed water

    /Overboard/OverboardI OverboardI \ublimator

    Figure 10. - Simplified diag ram of or iginal des ign of redundant coolingloop/water system.This configuration was sens itiv e to the absolute pr es su re in the water/glycolloop. A high pr es su re ca used water/glycol to ent er the wat erli ne feeding the secondarysubl imat ors. Development testing indicated that the s ubli mato rs had an acceptabletole ranc e to the ethylene glycol (commonly use d as "permanent" antifreeze). Thepressure in the second ary water/glycol sys tem was established by filling it with hot,deaerated water/glycol and then sealing it off. When the sy st em cooled to ambienttemperatures, it w a s at a subatmospheric pr es su re (approximately 5 psia).Thermal-vacuum testing on a lunar module test article (LTA- 8 ) provided thefirst opportunity for testing with complete spac ecra ft syst ems . A very slight leakexisted, and the pr es su re that was locked off in the secondar y coolant loop slowly r os e.During the "hot case" secondary loop operation, the disk w a s punctured and the sec-ondary sublimato rs failed. The glycol had cau sed sufficient lowering of the freez ingpoint of the sublim ator feedwat er to prevent an ice laye r fro m forming, allowing thewate r to break through and to fre ez e in the s tea m duct. To eliminate this i nterface


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    between the water sy st em and the secondary water/glycol loop, the design was changedby adding an accumulator. The puncture disk and waterline were removed, and plugsand caps were installed to isolate the syste ms.Pump noise. - The coolant pumps, which are located in the cabin, have producedhigh noise levels. Surve ys have shown that the pumps are not noisy in themselves, butthe vanes produce pulses of fluid flow which excite the coolant l ines and (som eti mes) the

    cabin struc tur al panels to which the tubes are attached. The coolant is carefully deaer-ate d to prevent the formation of ga s bubbles, which could cau se cavitation or flow block-age. Thi s rem ova l of gas low ers the bulk modulus, which ag gra vat es the noiseproblem. Sever al methods of quieting the pumping noise wer e investigated and evalu-ated. A n expansion device that produced a significant reduction in noise was includeddow nst ream of the pump on later vehicles.The noise experi enced on missi ons was somewhat distr acting, both beca use of theintensity and because of an apparen t change in frequency on occasion. Thi s frequ encychanging ha s not been completely understood, but it is felt that reducing the overa llnoise level will make any such occur renc es less noticeable.The pulsing of flow can be detec ted by slight, periodic pr es su re changes of ap-proximately 10 psi. The mechanica l stresses caused by these pulses within the systemcomponents we re determ ined to be insignificant. Because these fluctuations a t400 he rt z produced "noisy" data, the pump discharge pr es su re transduc er w a s elec-trically damped. The pr es su re ripple at 400 hertz re sul ts fro m the 6000 rpm of thefour-vaned pump.

    A t m o s p h e r e R e v i t a l i z a t i o n S e c t i o nLiquid-cooled-garment provisions . - A cre w complain t in December 1968 indi-cated th Zt he M- 4 suit co ol -a zr gi na l during the altitude-chamber run at KSC.

    Design and checkout da ta review s showed that the LM-4 sui t cooling portion of the ECSw a s performing somewhat bet ter than specification, and the suits the mselves w erefound to be within specifica tion.improvements were inves tigat ed to s e e if the ga s cooling could be extended.cooling capacity is 520 Btu/man-hour fo r steady -stat e operation.only minor improvements could be rea liz ed with the gas cooling approach. A sy st emdesign change w a s made quickly to provide chilled water from th e LM for circulationthrough the liquid-cooled ga rmen ts . Th is method of cooling provides a large incrementof cooling capacity. Even with the wo rs t- ca se (warm water) situation, a 1200-Btu/man-hour metabolic load can be comfortably handled; and 2000-Btu/man-hour loads can beaccomm'odated f or at least sh or t perio ds, although heavier persp irati on is experienced.

    Sev era l methods of providing cooling per for manceThe designIt w a s concluded that

    The design that wa s adopted fo r liquid cooling was not optim ized; instead, maxi-mum usage was made of existing components to make the unit avai lable fo r L M - 5 , thefirst lunar landing vehicle (Apollo 11). The cabin heat exchanger w a s removed not onlyto provide a location fo r the new unit (designated the LSC-330-192 ackage) in the .cabin, but a ls o because the cabin tempe rat ure co ntrol range provided by the cabin heatexchanger was a ra the r sm al l value. This follows the trend of both Gemini spac ecra ftand the Apollo command module ECS experience, in which the cabin tem per atu re con-tr ol provisions have been quite sm al l compared to the capacity of suit-circuit heat17

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    exchangers. Typically, afte r the design has proceeded as far as vehicle thermal-vacuum testing and flight, th er e has been enough confidence to dele te o r to deactivatethe cabin heat exchangers. The design selec ted als o removed the cabin tem per atu recontrol valve and one cabin fan. The remaining cabin fan was retained fo r contingencypurpo ses to enable cabin atmo spher e mixing and purging necessitated by the lo ss ofcarbon dioxide rem ova l capability. The liquid-to- liquid heat exchanger that was as-sociated with the cabin heat exchanger was relocated and replumbed to chil l the waterwith cold water/glycol. As a sidelight to the deletion of the cabin heat exchanger, thecabin temperature senso r w a s no longer located in any gas s tr ea m and thus s ensed atemperature in a remote corner of the cabin. It had been observed that a waterlinetemp eratur e closely approximated the cabin tem per atu re (because the water is routedthrough the cabin, giving a considerable dwell time); therefore, the water temperaturewas used as cabin temp eratu re by flight contr ollers . This proce dure saved relocatingthe sensor to a location which would receive good airflow of representative cabin-gastemperature.

    The water pump used in the LSC-330-192 unit is a PLSS design and us es 16 voltsdc . A voltage regulator w a s designed to drop the LM 28-volt dc power to the co rr ec tvoltage. This voltage regu lator was the only new item designed fo r the LSC-330-192package. A glycol valve w a s modified to bypass the circulating water around theliquid-to-liquid heat exchanger fo r crew comfort. This design provides water at th esa me temp eratu re for both crewmen; and, if one is overchilled, he can disconnect thewater umbilical at the suit. A schematic diagram of this unit is shown in figu re 11.

    Cabin fanOrifice



    Key:L h I P - lun ar module pilotC D R - commander

    Coolant fromlow-temperatureelectronicsCoolant tohigh-temperaturecold rails

    II regulatorI

    Figure 11.- Schematic diagram of the LSC-330-192 package.18

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    W a t e r separators . - The water sep ara tor s underwent seve ral changes to achievespecified performance . Considerab le ear ly development testing w a s performed to re-duce the gas-side p res sur e dr op and still achieve water pumping capability. La te r, theasse mbly was redesigned to im prov e the pitot tube ( wate r pump) efficiency, the bearingsupp orts , and the assemb ly method. In later st ag es of development, se ve ra l of the ga sinlet vanes were blocked to give the gas st re am impinging on the turbine blades of therotating drum a higher velocity. In addition, the blade angle was changed, and thewater pitot probe was again modified. W i r e mesh w a s added to the drum to assist thecoalescing of the drop le ts . A cutaway view of the flight configuration is shown infigure 12:All the development changes we re

    Pitot (wa te r pump)aimed at improving th e pumping capabil-ity with low gas-flow rates. During qual-ification testing, the unit experi enced afailure to start following a shutdown. Inthis condition, the ullage wate r that isretained within the unit s ett les to thebottom and cr ea te s a high res ist anc e torotation when restart is attem pted with alow gas-flow rate at minimum systempressure. Clearances were revised,drain provisions wer e added, and addi-tional inlet guide vanes were blocked.This design w a s then qualified by test forflight.


    Figure 1 2 . - Centrifugal water sepa rator(i te m LSC- 330- 109).During th e flight of Apollo 11,waterdrops we re sprayed onto the crew-men on sev era l occasions.reasons, but the cause w a s finally determined to be water s epa rat or overspeed.gas-flow w a s cons iderably in exc es s of specification as a re su lt of bett er-th an-specification perfo rma nce of th e suit fan sand because of lower-than-nomina l sy ste m-pr es su re drops. At high speeds, the waterin the trough splashes; and some is car -ried downstream and into the suits. Asimple orifice plate w a s added to the pri-mar y lithium hydroxide car tri dge to re-turn the gas -pr ess ure drop to specificationvalue in ord er to provide neces sary waterrem ova l efficiency. Because the secondarylithium hydroxide cartr idg e is smallerthan the prima ry c art rid ge and producesa pr es su re dro p compatible with prop erw a t e r separ ator performance, this snap-in item, which is i l lustrated in figure 13,w a s not re quire d fo r the secondarycartridge.

    The subsequent investigations identified s ev er al possibleThe

    Figure 13. - Primary LiOH cartridge(i te m LSC-330-122).19

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    Suit-isolation valves. - During the safety r ea ss es sm en ts following the Apollospacecraft fire in 1967, a completely new valve wa s developed and provided fo r iso lationof the suit gas umbi lical hose s. The change provided electrically actuated, fast-actingvalves that automatically close d both supply and re tu rn ho ses of both crewmen if suit-circu it pre ss ure dropped below a safe level. Use of the valve guaranteed th at at leastone crewman would be protected (pr ess uri zed ) and enabled to reopen hi s ho ses manu-ally, to close the hatch (which was presumably open in orde r to get a low cabin pr ess ur ein the first place), and to re pr es su riz e the cabin. The previous design w a s manuallyactuated only and provided protection fo r one less fai lur e than the solenoid actuateddesign. This change was made rat he r late in the program and proceeded without majorproblems. Sluggish operation on se ve ra l units required a minor change of ma te ri al sto retai n clearan ces after repeated usage.

    A cutaway view of t h is valve is shownin figure 14 . The cabin repres suriza tionvalve could be automatically actuated bymea ns of the swi tch shown on the cutawayonly if the repress urizat ion valve was inthe automatic mode. This switch was laterremoved as an unnecessary function.

    Actuation of the sui t-i solation valveswas initially achieved by a suit-pressuretransducer, which activated relays throughsigna ls fro m the caution and warning sub-syste m. This design w a s changed to act i-vate the relays directly fro m a snap-actingpr es su re switch. This change improvedthe reliability and simplified the ove ralldesign. Originally, the transducer signalwas compared with a preset voltage levelin the caution and warning subsystem,which tri ggere d the relay that applied thevoltage to the isolation valves when thesuit-circuit p re ss ur e decreased below thepresen t level.for "disconnect" mode

    Figure 14.- Suit-isolation va lve(item LSC-330- 138).Carbon dioxide se nso r. - A number ofproble ms wer e encountered with the carbondixoide sensor used in the L M ECS, and the unit was frequently criticized. Despite thecritici sms, the flight performance w a s gener ally good and provided useful data. Thefunctional schemat ic diag ram of the carb on dioxide sen so r is shown in fig ure 15.This instrument was initially Government-furnished equipment and was laterturned over to the con tracto r to be supplied as contr actor -furn ished equipment. Whenthe unit w a s retested to prove compatibility with the L M vibration levels, vibrationproblems were encountered. Other sensitivities were detected in the course of furtherground testing, and design changes made are discu ssed in the following paragraphs.The unit was mounted on vibration isolators to help attenuate the vibration envi-ronment. In addition, a more rugged infrared (IR) sou rce (lamp) was used; and the unit


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    f- Electronicsystem

    tRead-out ~

    I IFigure 15. - Simplified sy ste m diag ram

    of a C 0 2 sensor .

    ca se was ruggedized. The unit w a s de-signed to have a dc ground; but, becausethis was incompatible with the LM cautionand warning syste m, an ac ground(resistance-capacitance network) w a sadded to delete electromagnetic interfer-ence (EMI) sensitivity.

    If water entered the unit, it couldbridge a narrow gap and set up a galvaniccor rosi on cell, which would then degradethe optical filter laye rs and seriously de-gr ad e the sensi tivity of the unit. An epoxy-type coating was added to cover t he me talsurface near the filter and thus eliminatethe galvanic cell action.Calibrat ion changes with t ime andtemperature were trac ed to outgassing ofthe conformal coating in the electron icssection. Because the outgas productsabsorbed IR energy at the sa me wavelength(4 .3 micron s) that carbon dioxide does, elimination of the res ulta nt disto rted sign alsrequired a change to the con formal coating m ate ria l.thermistor were added to the cir cuitry for temperatu re compensation.In addition, a t r im res is tor and a

    Flight performan ce indicated satisfact ory operation except fo r se ve ra l momentaryexcursio ns during engine firing s and s eve ral in stances when w a t e r is believed to havebeen introduced into the se ns or . Solids or liquids which inte rrup t the optical signa lappear as lar ge amounts of carbon dioxide and dis tor t the signal. The unit will returnto norma l operation after the w a t e r dries .Lithium hydroxide. - Ca rtr idg es containing lithium hydroxide a r e located in thesuit-circuit assembly to provide chemical control of carb on dioxide. During the pro-

    gram , sev era l significant design changes were made.The ea rly design allowed the gra nul ar lithium hydroxide to abr ade when the unitw a s subjec ted to vibration, and "dust" that w a s generat ed and evolved with the effluentgas w a s very caustic and irr ita tin g to eyes, nose, and throat tissu es. The design w a schanged in ea rly 1966 by comp ress ing the gran ule s tighter within the co ntainer so thatrela tive motion w a s inhibited. The packing pro cedu re was als o changed to load only afrac tion of the car tri dg e, then vib rat e lightly to pack the granu les, load some mor e,vibrate, and s o fort h until the unit was properly filled. Figu re 13 shows the flight con-

    figurat ion in cutaway view,Polyurethane foam was the m ate ria l that was used to c omp ress the granules.Thi s mate rial , which was s ele cte d to give uniformly high loading, was durab le evenunder re qu ire d sto rag e vacuum and tem per atu re conditions. Following the Apollospacecraft fire in Janu ary 1967, the us e of polyurethane foa m fo r co mpre ssin g lithiurn

    2 1

    .I . , , , , . . , I . , . , , , . I , ,, ...,.. , , , .. .. . . . . , , . , , ,, . .... .. .... ._... . ...... . . . . ....

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    hydroxide gra nu les was prohibited. Although fire testing of t his design was suc ces s-fully passed, the pres ence of the polyurethane foam repr esent ed an immeasurablehaza rd, which was judged to be undesirabl e.The ensuing rede sign considered othe r "foam rubber" ma te ri al s of the fireproofcl as s (Fl uore l foams) along with metallic spri ngs and wash ers to achieve the chemical

    bed compr essio n loading. Because the fireproof foa ms we re not too well developed atthat time, the metallic spring design w as adopted and qualified fo r use. The filtermater ial contained in the c artri dge w a s changed fr om Dacron to Teflon felt at the sam etime.During the Apollo 10 (LM-4) flight, an unusually high rate of carbon dioxide in-crease, followed by a decrease, w a s noted. (See the sec tio n entitled ??F lig htExperi-ence. ") The LM-4 LiOH cartridge, which w a s returned in the Apollo command modulefo r analysis by the manufacturer, became the first it em of LM equipment to be re-turne d fo r postflight an alys is. Following chem ical and X-ray diffraction analy ses, itwas finally concluded that vari ation s in thechemical conversion rates combined with

    carb on dioxide se nso r tol eran ces accountedfo r the flight perfo rman ce variations. N o 4.4 -evidence of channeling o r breakthrough 4.03.6


    deemed necessary. Figure 16 shows the -w a s found, and no design changes wereflight data combined with test data fromground-test cartridges. It can be se enthat performance variations that reflectwidely varying ra te s of in cr ea se had beenexperienced. Subsequent flight per for m-ance predictions were made for optimisticand pessimistic var iations to account forthe dispersions seen in test. The peaks 6seen at 6 and 7 . 7 hours were typica l ofclos ed suit-loop operation and were causedby a combination of reduced suit-loop ma ssflow and an in cr ea se in carb on dioxideparti al press ure. Future designs should

    :.0 -E 1.6

    Predicted fo r A p l l o 101520 Btu iman-hour11 1 1 1


    attempt to maintain system pre ss ur e and 0 2 4 6 8 10 12 14 16 18 20 22flow during suited and unsuited operations. Relative time, hr

    Suit-circuit fans. - The suit fan Figure 16 . - Lithium hydroxide car tri dgeperformance curves.otors were initially manufactured by avendor to the main subcontra ctor. Prob-lem s were experienced both in failu resof the power tra ns is to rs and in consistently getting the c orr dct rotational di rection asa re su lt of im prop er phasing of the integ ral in ve rt er s. This development w a s eventuallytaken over by the main subcontractor, and design changes wer e established to co rr ec tthe problems.Bearing problems w e r e caused by ( 1 ) contamination, which re qu ired improvedcleaning; (2 ) inadequate lubrication, which nec ess ita ted changing fr om G- 308 toAndok-C grease; and ( 3 ) bearing ra ce brinelling, which requi red an improved fixture


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    to pull bearings .cor rec ted by re vis ed techniques and by design changes. The fan wheel rubbed duringear ly testing, and cle ara nc es we re changed slightly. Shimming w a s used to prevent theinducing of load s into the fan sc ro ll fr om the ductwork.

    Par tic ula te contamination during the manufacturing operation was

    In late 1968, an EM1 suppr ess ion fi lt er within a suit fan electronic s package w a sfound to have an intermi tten t open cir cui t during KSC checkout.tra ced to overheating of the EM1 filterswhen heavy el ect ric l eads w e r e solderedon. The overheating caus ed fai lur e of achange to heavy-gage wi re was made asthe spacecraft 204 accident at KSC n 1967.The configuration of the r ad ia l flow fan-motor assembly is shown in fig ure 1 7 anda motor cutaway view in fig ure 18. De-tails of the EM1 fi lt er configuration andwiring arrangement are shown in figu re 19.

    The problem w a s

    sol de r joint within a capacitor. The Fan d i s c h a r g e d u c ta re su lt of wir ing safety rev iew s following b r u s h l e s s m o t o r

    Gas flowc

    It w a s desired to test the units inplac e within the vehicle to s av e time. Abench test program w a s set up in an effortto determin e whether the ca pacitor leadwould be intermittently open, but the testswer e unsuccessful. The tests used X-ray,r f energy, and an "rf sniffer." TheX-ray approach w a s unsuccessful becausethe p roblem joint w a s too inacc essible inthe installation. Imposing r f energy onthe power le ads proved to be only partiallyently ge nera te enough rapi d local heatingto cause a capacitor open circuit. Thesebench tes ts we re tr ied on unit s which hadbeen intentionally failed as well as onso me good units.would detect ra diated elec tromagneticnoise, could not consistently detect a prob-lem in intentionally failed units beca use ofpoor acce ssib ility of t he probe.

    Figure 17. - Suit fan-motor assembly.

    succ essf ul because it would not con sist- M I filter location

    The rf sniffer, which

    The design solution for th e filterproblem w a s to move the heavy-wire con-nection point fa rt he r from the capacitorlead and to install a wiring lug that w a sbett er suited to the heavy w i r e . A methodw a s developed to'remove the suit fans(two pe r vehicle) fro m the vehicle instal-lation and to re pla ce them with redesig ned

    Figure 18. - Cutaway view of su it fa nmotor.23

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    units. This procedu re proved to be suc-cess fu l when done by one specif ic, metic-ulous asse mbl y technician. The potentiallyfaulty fans w ere replace d on the LM-3(Apollo 9) vehicle at KSC, hus savingmany days of r epla cem ent and checkouttim e that would have been req uire d forreplacement of a complete ARS package.The highly s killed technician w a s presenteda "Snoopy" awa rd fo r his effort. Theexact method and the technique required toperform these replacements were practicedand perfected at the subcontractor's plantbefore they w e r e perform ed on the flightvehicle.

    O x y g e n Supply a n d C ab in P r e s s u r i z a t i o nFi l ter housingCapacitor S e c t i o n

    used to rep res su riz e the cabin and can beactuat ed manually or automatically by asolenoid in response to low cabin pres sure .During design feasibil ity testing, themanual-close seat w a s found to be sus-ceptible to perma nent setting, and the seatmate rial was changed fro m Viton B toTerminal lug


    No 22-gage wire

    Ferrit e beadsViton VB90. The configuration is illus-trat ed in figure 20 and is designated con-figuration A (fig. 21(a)).Figure 19. - Suit fan EM1 filterconfiguration.

    During production acceptance testingpr io r to the endurance phase of qualifica-clo se mode. Inspection reveale d that theseat had cracked as a re su lt of com pres-siv e loads. The seat was redesigned to awave-type shape (configuration B, fig. 21(b))to allow required compression with lateralma ter ial expansion. This configurationw a s subjected to verification tes ts followedby fo rma l certification tests. During thevibrati on-tem peratu re testing of the ce rti -fication pro gra m, the valve again leakedin the manual-close mode. It w a s deter-mined that to lera nce buildup was allowingthe valve poppet to load unevenly and toemergency oxygen valve. move late rall y during vibration. A design

    ally c l 0 S ~ tion, leakage again occ urr ed in the manual-

    pressureswitchNote Valve shown in "auto" position.

    Figure 20. - Cabin repress urizatio n and24

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    change w a s made to the seat length to provide better centering and to resist lateralmovement. Certification testi ng was co mpleted with no additional leakage proble ms.Configuration C (fig. 21(c)) is the final seat and seal design.

    SeatSeal W o n VBWI

    Sh im4r.-"i3c


    (a) Configuration A.

    (c) Configuration C .Figure 21. - Seat and seal details -cabin repressu rizati on andemer genc y oxygen valve.

    Seal IViton V B 9 0 )



    (b) Configuration B.

    The cabin repres suriz ation andemer genc y oxygen valve, a high flow-ratedevice, is located in the cabin immediatelybehind the lunar module pilot. When thevalve position is changed fr om "close" to"auto** or fr om "auto" to "close, * 'asha rp, loud re po rt occu rs. This ',bang'*is caused by hi gh-pr essur e gas expandingto produce a shock wave. Tes tin g of thevalve d emonstrated adequately that noequipment damage is incurred; but thenoise has been startling to the crew, par-ticularly when their helmets are off.Sever al design modifications wer e consid-ered, but no changes w e r e directed. Theve ry sat isf act ory functioning of the existingdesign w a s felt to be a distinct ass et andthe flight cre w recommended retainingthe design and providing pro per alerti ngof the crews. This has become an emec tednoi se dur ing activation/deactivation of the LM subsy stems and during extravehicularactivity (EVA) preparations.

    Demand regulators. - The oxygen demand regulator (LSC-330-306)s one of twoparallel-redundant units that are used to provide suit-loop and cabin pr es su re control.The reg ula tor (fig. 22) is basically a balanced rocker/poppet design with calibratedsprin gs working against an aneroid bellows for absolute pre ss ur e control. A failed-open regulat or is overridden by t he clo sur e of a redundant manual seat. The aneroidchamber is isolated fro m the regulated pr es su re chamber, and each chamber is con-nected to the suit loop by a sep ara te line.25

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    Se le c t o rV a l v e p o s i t i o nand'e

    F u n c t i o n s w i tc hB a l a n c e d l e v e rC a b i n s p r i n g

    A n e r o i d b e l lo w s

    g e n s u t c i c u tPoppet

    su p p l y a sse m b lyFigure 22. - Cutaway view of oxygen demand reg ulator .

    The original design w a s highly sensitive to vibration while the demand regulatorwas operating within it s pressure-control regions. Various aneroids and mass-balancing techniques were employed before the design w a s acceptable. The final de-sig n did not complet'ely eliminate the inc rea sed le akage during vibration, but thesuit-loop oxygen volumes a r e such that negligible pre ss ur e rise would occ ur du ringthe vibration periods .On se ve ra l occasions, the oxygen demand reg ula tor s wer e contaminated by water,which produced c orr osi on following syst em checkout probl ems at the factory. Theseprobl ems, which we re always assoc iated with testi ng the suit ci rc ui t "wet" by usingthe metabolic simulator (which introduces steam into the ECS), were identified onlyaf te r som e length of tim e following the incide nts. In some cases, excessive water hasbeen introduced as a res ult of metabolic simulator probl ems or by test er ro rs withother relat ed ground-test equipment that blocked the water disch arge from the separ a-tor s. The result w a s that water co llects at the low point in the s ys te m where the oxygenregulator discharge tube attaches to the suit circuit. Testing is performed at 5 psia;and, at the completion of testing, wat er is driven upward into the demand regulato rswhen the pre ssu re is returned to sea level. Subsequent drying oper ation s (evacuation

    and purge) were ineffective in removing the w a t e r fr om the regulators; and corrosionresul ted, particularly on the aneroid bellows. The relationship between the wate rsep ara tor a re a of the suit circ uit and the oxygen demand regula tors is shown in fig-u r e 23 .all factory operations to avoid mois ture problems.The us e of st ea m in the metabolic simulator w a s finally discontinued during

    2 6

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    High-pressureu i t - c i r c u i t duct6t-3o * supply l f rom s u i t s )

    1 Reference pressur eI sense l ineI

    A and B

    From sui t heatexchanger

    Area where watercol lect ion has occurrema l l dra in tank

    Figure 23. - Elevation schema tic ofdemand regulator/suit circui t.Externalhandle

    Figure 24. - Cabin dump and relief valve(it em LSC-330- 307).

    Cabin dump and relief valve. - Two(redundant) cabin dump and relief valves(LSC-330-307) are use d in each LM vehicleEach valve provides cabin pre ss ur e reliefat 5. 6 -f 0.2 psid and is sized t o preventoverp ressu rizatio n of the cabin fr om anysingl e fai lure of high-p ress ure oxygenlines or components. Manual actua tionsa re provided to allow depressu rization ofthe cabin when de sire d and also to closeoff t he main poppet i f the serv o controlfails open. A sectio n view of the valveis shown in figu re 24 . The cabin dumpand relief valve ha s three modes of opera-tion, as follows.1. The ''dump" mode mechanicallylifts the main poppet, allowing manuallycontrolled cabin depressurization.2. The "auto" mode allows these rv o valve (which is refere nced to cabinand extern al environments) to controlpr es su re by equalizing the serv o chamberpr ess ur e with external pre ssu re, allowingcabin pre ssu re to force the main poppetopen.s u r e is reached, the ser vo valve closes;and the ser vo chamber is returned tocabin pr es su re by pre ss ure inbleed throughthe cabin reference orifice that causes the

    main poppet to clos e.

    Once the s ervo valve re seat pres-

    3. The "close" mode is provided toallow manual clo su re of the main poppet ifthe servo fails open.fo r this fa i lure is limited to 1 lb/hr bythe cabin reference orifice.Overboard leakage

    During initia l certification testing ofthe cabin dump and relief valve, the leak-age ra t es were out of specification following vibrat ion-temperature exposure.down indica ted that a material used as a volume filler in the se rvo chamber wasventing ful l closur e of the se rv o valve.ing development tests to achieve the proper dynamic resp onses of the valve, w a schanged fr om an expanded molded foam (like Styrofoam) to gaske ts form ed fr om asilicone rub ber compound.changes.


    cracking and generating par ticl e contamination that lodged in the ser vo valve sea t, pre -The filler material, which was necessar y dur-

    Certification w as completed with no additional design


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    High-pressure regulation and relief. - The high-pressu re oxygen contro l module(designated LSC--330-39'2) in the descent stage used a combination of t hre e modes ofp re ss u re relief. Redundant bypass relief valves provided low-rate relief to the sectiondownstream of the pre ss ur e regulator s.provided pr es su re relief, if necessary, during translun ar coast.board relief valves wer e s et to operate at a pr ess ure higher than the pres su re at whichthe bypass relief valves operate.the highest relief pressure.quired to function during a mission.

    Redundant low-rate overboard relief valvesThe low-rate over-

    A reseating b urs t disk provided high-rate relief atBy design, none of these relief valves should ev er be re-

    One of the most signi ficant fea tu res of th is module was the incorpora tion of thereseatin g bur st disk, which was an early design change that allowed retentio n of enoughoxygen to provide one cabin repr essu riza tion following a burst-disk rupture.seating bur st disk provided a significant degree of sa fety for the crew i f a bur st diskruptured during a lunar EVA period.mode (fig. 25(a)) and in a flow mode with the disk rup ture d (fig. 25(b)).wa sh ers would r es ea t the disk-support poppet when the upstrea m p re ss ur e was reduced.

    The re-This assembly is shown in the normal sealedThe Belleville


    - urst d i s kt ; - J r wI n l e t

    (a) Normal sealed position.Figure 25. - Burst-disk relief assembly.

    Water Management Sec t ion

    Bel lev i l l e

    I n l e t

    (b) Open position.

    Iodine compatibility. - All the water u sed in the LM is loaded before launch, andmedical req uiremen ts exist fo r maintaining the water f re e of viable orga nisms fo rhealth reasons.the potable (drinking and food preparation) water and the re claimed (from resp irationand perspiration) metabolic water.likely that a biocide would be requ ire d even if t he re wer e no interconnection because ofuncert ainties in long- te rm wate r s tora ge and the necess ity of maintaining an acceptablemicrobiological condition. )

    This requirement evolved because the re is an interconnection between(Notwithstanding the foregoing, it is considered

    Tes ts at the main subco ntracto r facility showed that the sub lima tors could notperform using chlorine (introduced as sodium hypochlorite). In a ha rd vacuum, a


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    green ish resid ue (identified as chlorine hydrate) slowly forme d on the ice layer. Aftera period of time, the incr eased concentration of the chlorine hydrate lowered the melt-ing point of th e ice below 32" F.through the porous plates and to freeze in the vacuum space.This melted the ice and caused water to run freelyIodine was next tri ed as a biocide and found to be compatible with the sublimationproces s. Development testing of othe r portions of the wa ter sy ste m and with metallic

    and nonmetallic materials showed generally good stability and only slight corrosionfrom the use of iodine. Co rro sio n which re su lt s with iodine concentrations of about15 ppm is essentially the s am e as that which occ ur s with wate r alone.Tests w ere performed to show that a proper iodine concentration could be main-tained fo r approximately 30 days. The medical requir emen t was that at least a 0. 5-ppmiodine residua l had to be pr ese nt when the last water wa s consumed, which could be ap-proximately 30 days afte r tank servicing. N o onboard tes t devices we re planned be-cau se of the rat he r cumbe rsom e checking techniques required of the crew. Fur the rground-test re su lt s began to show wide variations in iodine depletion ra te s. The vari-abl es involved see me d to be inseparable, and the data were reviewed carefully severaltim es before a pattern apparently emerged. The final conclusion was that the initial

    exposure of the water tanks to iodine result ed in an acceptably slow depletion ra te , butthat repeated exposures caused progres-sively faster depletion rates.rective me asu re was to avoid loadingflight load. The descent wat er tank con-figuration is illustr ated in fig ure 26. The Di f f us e r ub eascen t tank is sim ilar but is more spher-ica l in shape.

    The cor-water containing iodine except fo r the N2 1111 part

    N2 cavity

    The mechan ism of iodine depletionwa s found to be the diffusion of iodine va-por fro m the water, through the siliconerubbe r bladder, and into the surroundingnitrogen gas space. Water vapor alsopermeates th e bladder, as does the nitro-gen pre ssu ran t gas. The humid iodinevapor a ttac ks the anodized aluminum tankwall; and, as the anodized coating iscorroded, mo re 6061-T6 aluminum is ex-posed. The exposed aluminum readi lyrea ct s with the iodine. As the iodine isdepleted, the vapor pr es sur e is reducedand more iodine vapor perm eates thebladder to maintain an equilibrium vaporpr es su re, thus depleting the iodine in thewater . The anodized aluminum standpipethat is imm ers ed in the liquid sid e is con-sistently uncorroded, but the tank wallsshow definite co rrosion with the amountdependent upon exposure t ime .


    Mounting plateWater f i l l and out le t port

    (i tem LSC- 330-404).Figure 26. - Descent water tank


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    Exposure history was not readily apparent as the cause of iodine depletion, be-ca us e of the many var iab les of testing. Tank sh el ls and tank bladders were often shiftedf r o m test to test (because not many test item s wer e available f or u se) and reexposed.Exposure tim es and concentrations of iodine var ied considerably. It was felt fo r a timethat the bladder ma te ri al reacted with the iodine, and "seasoning" of bladders was tr ie dat se ve ra l hundred ppm. Bladd ers which had been exposed to ethyl alcohol appea red fora t ime to cause fast iodine depletion. Until that time, the iodine was introduced in tinc-tu re fo rm (iodine in ethyl alcohol) because the ea se of dissolving iodine in alcohol madethe testing m or e convenient. Testing was changed to use wat er solutions of iodine only.Only after the tank s hell exposure histor ies were carefully arra nge d in or der did thedepletion test results appear consistent.

    The water tanks on the LM-3 (Apollo 9 ) vehicle had been exposed to iodine in thealtitude-chamber testing a t KSC; thus, ear ly depletion of the iodine was predicted. Abacte ria fi lte r was affixed to the water dispenser f or that flight. The fil ter was not usedon the LM-4 vehicle because the wat er tanks we re not exposed to iodine before the flightwater was loaded.Tank bladder adhesions. - Silicone rubber bla dders w er e used in the water tanks

    fo r zero-gravity expulsion. It was found that a bladder, when maintained in a collapsedstate for a consid erable period, would adh ere to itself (adjacent folds, fo r example);and, when subsequently expanded, i t would be weakened or damaged. This adhesion wasof the nature of a fusion of the rubber.sequently maintained in an expanded st at e by the application of se ve ra l ps i of dry nitro-gen pr es su re on the water side. Whenever the bladder configuration w a s changed(inflations or deflations), a reco rd was entered in a "Limited Life Log" in accordancewith established progr am requi remen ts. Pr es su re cycles on the tank itself were like-wise recorded for a comparison to allowable life cycles. The life limitations we rebased upon previous te st experience and engineering judgments.

    To prevent adhesions, the bladders wer e sub-

    During checkout operations at KSC, a bladder tear was discovered on the LM-7vehicle. The subsequent investigation failed to identify the specific cause of the failure,which could not be traced to a mat eria l defect or to improp er p re ss ur e application orother handling problems. To en su re that flight tanks did not have tea rs , an X-ray ex-amination w a s implemented after the water w as loaded fo r flight. Gas leakage checkshad routinely been used to show that no tear existed just prior to waterloading.

    This is an example of the "explained" category of fai lure reports . N o fault couldSpecial test se found with the bladder design or with the manner in which it w a s used.wer e implemented, however, to verify that the flight units we re fr ee of defects aftercompletion of prelaunch preparati ons .Redundant water regulator and particulate contamination. - Partic ulate contamina-

    tion and corrosio n were experienced a number of t im es during development and check-out. In general, the corrective mea sur es were to progressively reduce the exposuresto water and to dry the sys te m more thoroughly following use. Even minor cor ros ionre su lt s in the generation of large amounts of part iculate contamination.water system corrosion w a s found in the first se ve ra l LM vehic les, including the LTA-8.The corrosion occur red in the tubing inte rio r, where the alodine coating had been de-stro yed when the gamah fittings (tube connectors) were swaged in place.flushes to re place the coating followed by water flushes t o clean the sys tem wererequired.


    Chromic acid


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    During checkout of t he LM-4 vehicle a t KSC, a water press ure regulator mal-functioned; and cor ros ion of s ome of the internal pa rt s was apparent. During the in-vestiga tion of the problem, the sensitivity of the reg ulato r design t o particulates wasa. majo r finding.contaminated.and by running fo r long durations.showed that the design was sensitiv e to malfunctions caused by parti culates, the unitsfunctioned satisfactorily in t est.redundancy that additional protectio n (wa terline fi lt er s) could not be justified.ma ry water sy stem already contained two regulators i n se ri es , but the backup syst emhad only a si