Apollo Experience Report Thermal Design of Apollo Lunar Surface Experiments Package

8/8/2019 Apollo Experience Report Thermal Design of Apollo Lunar Surface Experiments Package

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APOLLOEXPERIENCE REPORT -THERMAL DESIGN OF APOLLO LUNARSURFACE EXPERIMENTS PACKAGE

by Rober t S. Hurris , Jr.Munned SpacecrufiCenterHouston,exus 77058 . ,- . ,- . '. ,. .

-.,/'

N A T I O N A LE R O N A U T I C SN DP A C ED M I N I S T R A T I O N W A S H I N G T O N ,. C. M A R C H 1972


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- . ."~ .1. Rep ort No.. . I ---_2. Governm ent Accession No.~ ~~NASA TN D-6738-- . . ~~

APOLLOEXPERIENCEREPORTTHERMAL DESIGN O F APOLLO LUNARSURFACE EXPERIMENTS PACKAGE

-4. Titl e and. Subtit le ~ ~

~ ~- . .~7. Author(s)3. Recipient'sCatalog No.

5. Report DateMarch 19726. Performing Organization Code

8. Performing Organization Report No.Robert S. Harris, Jr., MSC I MSC 5-310

10. Work Uni t No.9. Performing O rganization Name and Address 514-40-73-90-72

Manned Spacecraft CenterHouston, Texas 7705811. Contract or Grant No.

- . ~ . 13. Typef Report an deriod Covered12. Sponsoring AgencyNameandAddress Technical NoteNationaleronautics and Spacedministration 14. Sponsoringgency CodeWashington, D. C. 20546

I1 ~ 5 ~ ~ S u ~ ~ l e m & 1 t a r yo tes ."The MS C Director waived the use of the International System of Units (SI)or

this Apollo Experience Report, because, in his judgment, use of SI Units would impair the usefulnessof the report or result in excessive cost.16. Abstract

The evolution of the thermal d esign of the Apollo luna r surfa ce experimen ts package cen tra lstation from the basic concept to the final flight hardware is discussed, including results ofdevelopment, prototype, and qualification t est s that were use d to ver ify tha t the light hard-ware would operate adequately on the lunar surf ace. In addition, brief discussions of thetherm al design of experiments included in the exper iment s packag e are presented. The flightthermal performance is compared with analytical result s and thermal-vacuum-test results,and design modifications for future lunar-surface experiment packages are presented.

17. Key Words Suggested by Author(s.1)~~ ~~~

Therm al DesignLunar Thermal Environment'Apollo Lunar Surface Experiments Package

~~ ~

19. Security Classif. (of this rep ort) 20 . Security Classif.None ~ None

18. Distr ibution Statement

"F o r sale by h e N a t i o n a l T e c h n i c a l I n f o r m a t i o n e r vi c e , S p ri n g fi e ld , V i r g in i a 22151


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" CONTENTSSection PageSUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .CONFIGURATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

112

THERMAL DESIGN O F CENTRAL STATION . . . . . . . . . . . . . . . . . . . 4THERMAL DESIGN O F EXPERIMENTS . . . . . . . . . . . . . . . . . . . . . 6

Passive Seismicxperiment . . . . . . . . . . . . . . . . . . . . . . . . . 6Lunar-Surfaceagnetometer . . . . . . . . . . . . . . . . . . . . . . . . . 7Solar-Windpectrometer . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Suprathermal-Ion-Detector ExperimentndCold-CathodeonGage . . . . . 8Activeeismicxperiment . . . . . . . . . . . . . . . . . . . . . . . . . . 9Heat- Flow Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Charged-Particleunar-Environmentxperiment . . . . . . . . . . . . . . 10Cold-Cathode-Gagexperiment . . . . . . . . . . . . . . . . . . . . . . . . 1 1

THERMAL TEST PROGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2MISSION PERFORMANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12CENTRAL-STATIONERFORMANCE . . . . . . . . . . . . . . . . . . . . . . 13EXPERIMENTERFORMANCE . . . . . . . . . . . . . . . . . . . . . . . . . 14COMPARISON O F FLIGHT.TEST. AND ANALYTICALRESULTS . . . . . . . 16DESIGN MODIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17CONCLUDING REMARKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17REFERENCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18APPENDIX- ARLYAPOLLOSCIENTIFICEXPERIMENTS PACKAGE . . . 19

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TABLE

TableI

PageEXPERIMENT ASSIGNMENTS FOR APOLLO LUNAR-LANDING

MISSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3FIGURES

Figure1 TheALSEPnhetowedonfiguration

Page

23

(a) Subpackage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . .(b) ubpackage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . .The final central-station thermal design . . . . . . . . . . . . . . . 4The central-station assembly . . . . . . . . . . . . . . . . . . . . . 4The radiator support mechanism in stowed configuration . . . . . . 5The PSE with the shroud in the deployed and stowed configurations(a) Shroudstowed . . . . . . . . . . . . . . . . . . . . . . . . . . .(b) Shrouddeployed . . . . . . . . . . . . . . . . . . . . . . . . . . 66

6 The LSM in the deployed and stowed configurations(a) Deployed . . . . . . . . . . . . . . . . . . . . . . . . . . . . .(b)Stowed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A side view of the LSM para boli c refl ecto r . . . . . . . . . . . . .

89

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The SWS in the stowed configuration . . . . . . . . . . . . . . . . .The SIDE/CCIG in the deployed configuration . . . . . . . . . . . .The ASE system in the deployed con figurat ion(a) Mort ar box and grenade-launcher assembly . . . . . . . . . . .(b)Thumper ssembly . . . . . . . . . . . . . . . . . . . . . . . . 99

11 Elements of the HFE . . . . . . . . . . . . . . . . . . . . . . . . . 10

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Pageigure12

1314

1516

1718

19

20

2 122

2 3

24

25

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The CPLEE in the deployed configuration(a) Exterior view . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11(b) Cutawayiew . . . . . . . . . . . . . . . . . . . . . . . . . . . 11The CCIG inhedeployed onfiguration . . . . . . . . . . . . . . . . 11The Apollo 12 ALSEP central station deployed on the lunarsurface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Thedep loyed rran geme nt of theApollo 12 ALSEP . . . . . . . . . 13A comparison of the average thermal-plate temperature, recordedduring lunar-surface operations, with the analytically predictedtemperaturenvelope . . . . . . . . . . . . . . . . . . . . . . . . 13Sunshield temperatures recorded during the second andeighthunations . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Primary-struc ture tempe ratures r ecorded during th e second ndeighthunations . . . . . . . . . . . . . . . . . . . . . . . . . . . 14The PSE internal temperatures recorded during the firstthreeunations . . . . . . . . . . . . . . . . . . . . . . . . . . . 14The LSM internal tempera tures recor ded during the second and

eighthunations . . . . . . . . . . . . . . . . . . . . . . . . . . . 15The SIDE internal temperatures recorded during the second andeighthunations . . . . . . . . . . . . . . . . . . . . . . . . . . . 15The CCIG internal temperatures recorded during the second andeighthunations . . . . . . . . . . . . . . . . . . . . . . . . . . . 15The SWS internal temp eratures reco rded during th e second ndeighthunations . . . . . . . . . . . . . . . . . . . . . . . . . . . 15A comparison of a verage radia tor temperatu res, recorde d duringlunar-surface operations, with the analytically predictedtemperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16A comparison of internal primary-structure temperatures,recorded during lunar-surface operations, with analyticallypredictedemperatures . . . . . . . . . . . . . . . . . . . . . . . 16A comparison of sunshie ld temperatures, record ed during lunar-surface operations, with analytically predictedtemperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

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Figur e27 TheALSEPdesign orhigh-latitudedeployment . . . . . . . . . . .

A- 1 TheApollo 11PSEP onfiguration

(a) Subsystems . . . . . . . . . . . . . . . . . . . . . . . . . . . .(b )Subsystems omponents . . . . . . . . . . . . . . . . . . . . .A- 2 The LRRR configuration

(a) Stowed . . . . . . . . . . . . . . . . . . . . . . . . . . . . .(b)Deployed . . . . . . . . . . . . . . . . . . . . . . . . . . . . .A-3Adiagram of the nte rna lstruc ture of a PSEP sotopeheater . . .A-4 A comparison of PSEP adiator-plate emperatures, ecordedduring lunar-surface operations, with analytically predicted

temperatures . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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191920

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APOLLO EXPERIENCE REPORTTHERMAL DESIGN OF APOLLO LUNAR SURFACE

EXPERIMENTSPACKAGEBy Robert S . Harr is, Jr.Manned Spacecraft Center

SUMMARYThe design of the therm al-c ontr ol syste m of the Apollo lunar surface experimen tspackage is presented in this report. The evolution of the central-st ation thermal-control system, from the basic concept to the final flight design, is discussed in detail,including re sults of the test progr am used to verify that the fin al flight desig n wouldperform adequately on the lunar surface. The basic thermal-de sign features of the ex-periments also are presented.The flight performance of th e experimen ts package is assessed, and is comparedwith analytical and thermal-vacuum-test results. The central station provides thethermal control req uired to maintain the temp erature of the electronic componentswithin acceptable limits when the cen tral st atio n is exposed to the lunar-surface envi-ronment. Also, the thermal analytical models developed to predict central-station

temperatures accurately describe ce ntral-statio n thermal per formance on the lunarsurface. Finally, thermal anomalies that occurred on some of the experiments andmodifications to correct these anomalies are discussed.

I NTRODUCTI ONThe Apollo lunar surface experiments package (ALSEP) contains a gro up ofscientific instruments that are used to obtain long-term measuremen ts of some phys-ical and environmen tal properti es of the moon and to t rans mit t he s cien tifi c dat aob-tained to receiving stations on earth. The data are used to derive information about

the composit ion and structu re of the moon, the magnetic field and atmosphere of themoon, and the solar wind. The ALSEP is composed of scientif ic experimen t packages ,a central station that collects and transmits data and distributes power to he experi-ments, and a radioisotopic thermoelectric generator (RTG) that supplies continuouselectrical power to the central station. The entire package was designe d to be deployedby press ure- suit ed a stro naut s on the lunar surface and to operate for a year o r longer.


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The A L S E P is assembled into two subpackages that are carr ied to the moon inthe lunar module (LM). One subpackage contains the central station and the majorityof the experiments; the other subpackage contains the remainder of the ex peri ment s,the RTG, and the other equipment used by the crewm en during lunar -sur face opera tion s.Although eight separate experimentsare discussed in this report, no more than fiveexperiment packages are included in any single A L S E P .The thermal-con trol system maintai ns the temperature s of the A L S E P centralstation and the experiments within required limits for operation in the lunar environ-

ment. The thermal design of the A L S E P central station and results of thermal analysesand thermal-vacuum tests are discusse d. Finally, the thermal performanc e of the firstA L S E P deployed on the luna r surfa ce is presented, and the central-st ation temperaturevariations are compared with analytically predicted temperatures.

C O N F I G U R A T I O N

The A L S E P equipment is stowed in the LM as i l lustrated in figure 1. On themoon, the A L S E P is deployed by the crewmen at a dist ance of at least 500 feet fromthe LM .

Central stalion

Primary structureSlructu refthe rmdl subsystem components

(a) Subpackage 1.Figure 1 . - The A L S E P in the stowed configuration.

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Figure 1.- Concluded.A maximum of five expe riments is included in each ALSEP. Experiment assign-me nt s fo r ea ch Apollo flight a r e outlined in table I. The versi on of the ALSEP carriedon the Apollo mission, the first manned lunar landing, was simplifi ed to reduce thetime requ ired for the depl oyme nt of the expe rimen ts. That vers ion of the ALSEP, which

was called the early Apollo scientific experiments package (EASEP), included a passiveseismometer and a laser reflector (appendix).TABLE I . - EXPERIMENT ASSIGNMENTS FOR APOLLO LUNAR-LANDING MISSIONS"-Apollomission-~ ..

121 3141516

.. ..

PSEaXXXXX

..

-~

Experiments

I

a~~~ -passive seismic experiment. eCCGE- old-cathode-gagebSIDE/CCIG - uprathermal-ion- experiment.detector experiment/cold-cathode ion gage. f~~ - ctive seismic experiment.'SWS - oh r- wi d spectrometer. gHFE- eat-flow experiment.d~~~ - unar-surface magnetometer. h~~~~~ - harged-particlelunar-environment experiment.

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" . .

Sunshield v tructureRadiatorWasher

Housing

support post

Spring

f i g u r e 4 . - The radiator support mecha-nism in stowed configuration.

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internal power dissipat ion of the cen tra lstation varied from 1 8 . 5 to 2 3 . 5 watts.With this power dissipatio n, a sunshieldheight of 8 inches above the radiator platewas needed to meet the 0" o 1 2 5 " F base-plate emperature imits. The system,which was tested in a 2 0 - by 2'i"footthermal-vacuum chamber under simulatedlunar-day and lunar-night conditions, metthe temperature requirements.Later in the program, the power-conditioning unit (PCU), which previouslyhad been an independent unit with a sepa-rate thermal-control system, was incor-porated into the central station. Thischange increased the central-station powerdissipation o approximately 34 watts. Be-cau se of the increased power dissipation,the sunshield height had to be increased to26 inches to provide an increased radiatorexposure. This change also necesitated theaddition of mult ilay er side curt ains to pre-vent direct solar impingement on the radi-ator plate, and awnings were added to preventdirect impingeme nt of s ola r radi ati on inthe event of central- station misali nement.

The increased sunshield height allows excessive radiative coupling between the lunarsurf ace and the radiator plate, increasing the temperature of the radiator plate beyondacceptable limits. To solve this problem, a V-shaped aluminized-Mylar specular re -flector was incorpor ated between the radiator plate and the sunshield. A series ofthermal-vacuum tests was conducted on a scale model of the ce ntral statio n to establishthe optimum refle.ctor arrangement. Based on these tests , a reflector angle of 6 6 " waschosen. Also, a portion of the radi ator pla te had to be masked with multilayer insula-tion to reduce the effective radiator area. This insulation is used to maintain theradiator-plate temperature at an acceptable level during lunar night. Deployment train-ing was indicative that alinement was not a problem; therefore, awnings were notnecessary.

The primary components of the the rmal- cont rol syst em are the radiator platewith attached electronic components, an insulated sunshield and sid e cur tai ns to pr e-vent impingement of so lar ra di ati on on the radiato r plate, multilayer insulati on (fig. 3)and radiator-pla te isolators to isolate component s from lunar-surface temperat ureex-tremes, thermostatically controlled heaters to provide additional power dissipation onthe radiator plate when required , and a power-dissipation module (fig. 3 ) to dissipateexcess RTG power external to the central station during lunar day when the powersnot requ ired for thermal c ontrol of the experiments. The final design of the central-station thermal-control system was incorporated into a detailed analytical model forprediction of component temperatures during lunar-surface operation. A detailed dis-cuss ion of th e analytical methods used is contained in reference 1.

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THERMAL DES IGN OF EXPERIMENTSA description of the thermal-co ntrol-system des ign for each ALSEP experimentis given in the following sections. Each ALSEP experime nt is required to provide itsown thermal-control system with environmental requirements essentially identical to

.tho se of the central station. Any additional power necessary to meet the thermal-control requirements is to be supplied from the central station by the RTG. Analyticaltherm al mo dels of the experiments were used to establish the required th ermal-control-system design. The design temperature limitations were determined by reliability con-siderations and by sci entific requirements.

Passive Seismic ExperimentThe PSE (fig. 5) was designed to monitor lun ar seismic activity, to dete ct mete-oroid impacts, and to measure tidal deformations by the use of a set of triaxial, long-period seismometers and a short-period seismometer. The PSE sensor was designedto operate at a pre set mean tem per atu re of 126" f 1 " F. The desired temperature var-iation during a lunation was *O. 36" F of the prese t mean tempera ture, and the maxi-

mum allowable variation to obtain minimum-acceptab le seismic data was rt18" F of themean temperature. To meet the temperature-control requirements, the sensor had tobe isolated from the external environment. This isolation was accomplished by mean sof a therm al shrou d consis ting of 20 la ye rs of aluminized Mylar that cover the sensorand the lunar surface near the sensor. The shroud extension , which covers the lunarsurface, reduces the effects of the widely varyi ng lunar -surf ace tempe ratur es on thetem per atu res of the sens or. In addition to the shroud, controlled electrical heatersare used to maintain the sensor temperature during lunar night. The operating modeof the heater assembly is controlled by command through heater-control circuits. Theheater-control modes are automatic, thermostatic bypass (manual on), andoff. Thenormal operation mode is the automatic mode, which provides power to the heaterthrough a thermostatic-control circuit to ma intain the pres et temperature level of thesensor.

Thermalshroud-Sensorassembly

Sensor assemblywlthin the rma lCentral-

(a) Shroudtowed.b)hroudeployed.Figure 5. - The PSE with the shroud in the deployed and stowed config urations.

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Lunar-Surface MagnetometerThe lunar-surface magnetometer (LSM) is designed to measure the magnitude andvari atio ns of the lunar-su rface magnetic field. The objectiv es of the LSM investigationare to derive the electr ical propert iesof th e int eri or of the moon and to defi ne moreconclusively the interplanetary magnetic field that is diffused through the moon. TheLSM con si sts of thr ee ma gn eti c se nso rs mounted in sensor heads and located at theends of three 3-fo ot-l ong fibe r-gl ass sup port arms (fig. 6 ) . Each magnetic sensor ishoused in a fiber-glass jacket and is wrapped with glass-fel t insulat ion. Each of thethree sensors is equipped with a thermostatically controlled 1-watt heater to maintaina 95" to 113" F temperature range. The upper flat surface of ea ch sens or is left un-cove red and painted with a white coating so that it serves as a thermal radiator. Thesupport arms are mounted on a base structure that contains the electronics packageand the mechanism for controlling the position of the magnetic sensors. The LSMelectronic components a r e designed to op-erate in the range of - 5 8 " to 149" F.

-Easth an d south sidesM i c r ef le ct or s o n

(a) Deployed.b)Figure 6 . - The LSM in the deployed and stowed configurations.

The temperature of the elec tronicspackage is controlle d by a radia tor a r raythat consists of vert ical low-emittan ceparabolic reflectors (fig. 7) and horizon-tal high-emittance radiating fins. The re-f lectors are designed to reflect energyfrom the lunar surface, and the fins aredesigned to dissipate internally generatedheat nto space. The electronics packageis insulated, and the radiators are bondedto the electronics package. All externalsur fac es of the insulation subassemblyare covered with thin fiber glass andcoated with white paint. The structure issupported above the lunar surfacebyfiber-glass legs.

High-reflectancel infrared and solar)soecular surfacelparabolicl-Parabolic-reflector opening

di ffuse surfaceHigh-emittance(radiator f ins)l f l a t l

Figure 7. - A side view of the LSMparabolic reflector.7


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Solar-Wind SpectrometerThe purpose of the solar-wind -spectrometer (SWS) experiment (fig. 8) is to meas-ure the energy, density, incidence angle, and tempo ral vari ation of the ele ctr on andproton components of the solar-wind pla sma striking the lun ar surface. Detection ofthe solar-wind electrons and protons is accomplish ed by m ean s of seve n Faraday cups

that measure the charged-particle f l u x entering the cups. The open ends of the cupsare pointed toward different, but overlappin g, parts of the luna r sky.

The SWS th ermal -cont rol syste mis designed to maintain the temperatureof the elec tron ic comp onen ts in a 14" to167" F range.The SWS electroniccomponents are mounted on a gold-platedfiber-glasshousing.The hermal-controlsystem uses three radiators on one ver -t ica l face, and multilayer insulationcovers the other f ivefaces of the elec-tronics package. The radiators are afinned type and have parabolic reflectorsmounted under each fin to reflect radia-tion from the lunar surface in a manneridentical with the magnetometer radiatorsdescribed in the preceding section. Theinsulation is alter nate layer s of alumi-nized Mylar and silk organza. Duringlunar night, an electrical heater maintainsinternal power dissipation at 6 watts andis activated by a tempe ratur e senso r whenthe te mpera ture d rops below 77" F.

Suprathermal- Ion-Detector Experimentand Cold-Cathode on GageThe suprathermal-ion-detector ex-per ime nt (SIDE) and the cold-cathode ion

gage (CCIG) are combined as one unit(fig. 9). Th e pu rp os e of the SIDE is tomeasure f l u x , number density, velocity,and ener gy per uni t charg e of positive ionsin the vicinity of the lun ar sur fac e. TheCCIG is included with the SIDE to deter-mine the density of any luna r atmo sphe re,including variations associated with solaractivity.Thedesign emperature imitsof the SIDE elect ronic comp onents are-4" o176" F. The SIDE thermal-controlsys tem c ons ist s of an inner housing as-sembly to which electronic componentsand detec tors are mounted. The nnerhousing has gold-plated covers for low-emittance surface properties and is8

Sensoratsemblv-

Carry ing-handle

East -\Radiators (31

Figure 8. - The SWS in the stowedconfiguration.Second-surface mirrorslthermal controll-

Ground-screen

\Connectorable

Figure 9. - The SIDE/CCIG in thedeployed configuration.


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suspended in an external housing that has gold-plated inner surfaces. The top of theexternal housing, the radiator and heat sink for the electronics package, is coveredwith mirrors to minimize solar-radiation input; the inner and outer housings are .sep arat ed by mean s of plas tic screws. A coating of white paint is applied to exteriorsurfaces, and further therma l control is obtained with electrical heaters , a 4-wattthermostatically controlled operational heater, and a 2-watt survival heater. The as-sembly is supported and isolated from the lunar surface by three fiber-gla ss l egs.The outer housing also contains theCCIG,which is removed during the deployment ofthe experiment. The CCIG is deployed on the lunar surface app roximatel y 4 feet fromthe SIDE, and its temperature fluctuates with the lunar-surface temperature.

Active Seismic ExperimentThe primary function of t he active seismic experiment (ASE) (fig. 10) s to mon-itor artif ically gen erated se ismic waves in the lunar surface. The ASE also can mon-i tor na tura l se ismic waves in its frequency range ( 3 to 250 hertz). Informa tion acquiredfrom this experiment wil lbe helpful in the determination of th e ph ysic al pr ope rtie s of

the lunar-surface and the near-subsurface materials.The ASE con sist s of a mortar package, a thumper device, geophones, and anelectronics package that is located in the central station. The ASE use s two seis mic-energy sources: the thumper (containing explosive initiators that are fired along thegeophone lines by an astronaut) and the mortar package (containing four grenades thatwill be launched by te leme try command from earth). The mortar box is designed tomaintain the internal components between - 94" and 185" F. The internal temperatureof the mortar box is maintained with aluminized-Mylar multilayer insulation on the

si de s and bottom, an aluminized-Mylarsunshi eld on top, a white thermal coating,Transmitterntenna and a 1.75-wattlectricaleater.rangeine

/-Ini t iator selector switch

Armlf i reswitch-

(a) Mort ar box and grenade-launcherassembly. (b) Thumperssembly.Figure 10. The ASE system in the deployed configuration.

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Heat-Flow ExperimentThe heat-flow experiment (HFE) (fig. 11) is designed to measure the temperaturegradient and thermal conductivity in the upper surface layers of the moon. The meas-urements obtained from this experiment can be used for calcu latio n of lunar heat flowand will provide information about the composition and physical state of th e i nt er io r of

the moon.

Gradient sensorswithin heater coils-

East

Figure 11. - Ele men ts of the HFE.

The major comp onen ts of the HFEare sensor probes and an electronicspackage.Theprobes are epoxy/fiber-glasstubular structures that support temperaturesenso rs, heate rs, and associated wiring.The electronics package contains theprinted circuit boards used for control ofthe experiment. The operational temper -at ur e li mi ts of the electronic componentsare 3 2 " to 140" F. Temperature controlis acco mpli shed by both passive and activ emeans.Thepassive-thermal-control sys-tem consi sts of a sunshield for solar-inputreflection and specular reflectors that aidin dissi patio n of internally generated heat.Also, the electronics package is supportedby fiber-glass legs and is contained in amultilayer-insulation bag enclosed in afiber-glass tructure.Thermal-controlcoatings are used on external surfaces.The thermal design is simi lar to that ofthe central station described n a preced-ing'section. Active hermal control isprovided by a thermostatically controlledheater (2.55 watts) mounted on the elec-tronics package.

Charged-Part ic le Lunar-Environment ExperimentThe charged-particle lunar-environ ment experiment (CPLEE) (fig. 12) was de-

sign ed to measu re the ener gy dist ribut ion, time varia tions , and directio n of proton andelectron fluxes at the lunar surface. The CPLEE consists of two detector packages(analyzers) oriented in different directions for minimum exposure to the ecliptic pathof the sun. Each detector package has six particle detectors; five provide informationabout particle en ergy distribution , and the sixth provides high sensitivity during lowf l u e s .

The CPLEE is designed to operate within the temperature range from -50" to150" F. When the instr ument is nonoperational, the survival temperature range is-60" to 160" F. The CPLE E ther mal-c ontr ol syst em cons ists of multilayer insulationon fou r si de s and on the bottom of the package and a radiator plate with second-surfacem i r r or s on the top. The insulation is composed of a lt er na te la ye rs of aluminized Mylar

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-and fiber glass. The experiment configuration is shown in figure 1 2 . In addition tothe insulation, the CPLEE has thermostatically controlled heaters ( 3 . 0 watts) mountedto the unders ide of the radia tor plate that ma intain the te mperature wit hin require dlimits during the lunar night. The auto-matic control can be bypassed by commandto turn the heaters on o r off.

Physical analyzers

Electronics

Insula tion and cover

(a) Exterioriew.b)utawayiew.Figure 12. - The CPLEE in the deployed configuration.

Cold-Cathode-Gage ExperimentThe cold-cathode-gage experiment (CCGE) (fig. 1 3 ) is composed of a cold-cathode

ion gage and the associated electronics. The purpose of the experiment is to measurethe density of the lunar atmosph ere, includi ng any temp ora l vari atio ns of a random na-ture or variations associated with lunar local t ime o r solar activity. The experimentcan be used to measure the loss ra te ofcontaminants left in the landing area by theastronauts o r the LM.Sunsh ield assembly Handling-tool socket The design tempe rature limits of the

Levelinggage CCGE electronics are -4" o 176" F duringnormal operation on the lunar surface.The electronic components are attached toa radiator plate and are shaded from directsunlight by a sunshield (fig. 1 3 ) . A reflec-deep-space field of view and to reduce heat4.5-watt electrical heater was used to main-tain the internal temperatur e dur ing onop-

Electmniassembly t o r is usedorovide the radiatorith a-East inputromheunarurface.lso, a

Figure 1 3 . - The CCIG in the deployed erating periods and to assist in thermalconfiguration.ontroluringormalunar-nightperations.11


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The CCGE electronic components are housed in a fiber-glass case and are wrappedwith aluminized-Mylar insulation to reduce heat leaks f rom the lunar surface. The as-sembly was enclosed in a fiber-glass structure, and a white thermal-control coatingwas applied to external surfaces toassist in maintaining the required temperatures.

THERMAL TEST PROGRAMThe ther mal desi gn of the A LSEP central station arid experiments was ve rifiedby me an s of a series of system-, experiment-, and component -level thermal-vacuumtests. The test series includeddevelopment,prototype,qualification, nd light-acceptance tests. System-level tests wereconductedundersimulated unar-

environment conditions in a thermal-vacuum chamber 2 0 feet in diam eter by 2 7 feet inlength. Additional tests on vario us ex perim ent packa ges and on scale models of thecentral station were conducted in several smaller chambers. For the system-leveltests, solar simulat ion was prov ided by infrared lamps located above the central sta-tion and experiment packages. The lamps were controlled so that the leve l of energyabsorbed by a surface was equivalent to that absorbed by the s ame s urfac e in t he lu narenvironmen t under nominal and wo rst-case surface conditions. Control was accom-plished by moni toring the energy absorbe d by a radiometer with the same radiativeproperties as the surface absorbing the radiation. A 1 4 - by 1 4 - f o o t lunar plane wasdesigned to simulate the lunar-surface temperature extremes of -300" o 250" F. Theheat sink of s pac e was s imu lat ed by liquid-nitrogen-cooled walls.

Th e r es ul ts of the ALSEP test program were indicative of favora ble temperaturedistributions on all central-station components, and good tempera ture corre latio n wasobtained with the results of an alyt ical pred icti ons (ref. 1 ) . It was proven in the testprogram that the ALSEP thermal-control system would maintai n component tempera-tures within acceptable operating limits during operation on the lunar surface.

MISSION PERFORMANCEThe first flight-model ALSEP was deployed on the lunar surface during the

Apollo 1 2 mission during November 1 9 6 9 . This ALSEP array included the PSE, SWS,LSM, and SIDE. The Apollo 1 2 landing site was located at latitude 3'12' S and longi-tude 2 3 " 2 4 ' W. The Apollo 1 2 ALSEP was deployed on the lunar surface, as planned,approximately 6 0 0 feet west-northwest of th e LM (fig. 1 4 ) . The deployment arrange-ment is shown in figure 1 5 .

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Figure 1 4 . - The Apollo 1 2 ALSEPcentral station deployed on the Figure 1 5 . - The deployed arrangementlunar surf ce. of the Apollo 1 2 ALSEP.CENTRAL-STATION PERFORMANCE

The average central-station radiator-plate temperatures f o r the second andeighth lunations are plotted in figure 16 and include a comparison with the postflightanalytically determined temperature envelope for the actual deployment configuration.The predicted radiator-plate temperatures compare favorably with the actual tempera-tures encountered during the mission. The average radiator-plate temperature duringthe lunar day was lower than was pre-dicted.Themaximum adiator-platetemperaturewas 97" F during the first 250lunaray,omparedwithhexpected MO 0 Averagehermal-plateemperaturesecondunationlvalue of approx imately 125" F. Themin- ~ ,50imum radiator-plate temperature duringlunar night was 0" F because the central- 2 100station heater was urned on at that em- k 50perature.hestimatedinimum s otemperature hat wouldhavebeen eached -50without the heater was - 5 " F. Withhe -100central-station heater operating, the av-erage radiator-plate temperature stabi-lized at 21" F during unarnight.TheFigure 1 6 . - Acomparison of theaveragemostprobablecau se of the owe rcentral- hermal-plate emperature, ecordedstationperatingemperaturewasheuring lunar-surface operations,withfai lur e of the adiator dgemask ode- he nalyticallypredicted emperatureploy completely,herebyxposingorenvelope.radiator area.

0 Average hermal -p la te emperature e ighth unat ion lPredicted temperature envelope

0 20 40 60 80 100 120 140 160 180 200 220 24 0 260 280 300 3M 340 360Sun angle, deg

Central-station sunshield and primary-structure temperature variations duringtypical lunations are plotted in figures 17 and 1 8 , respectively. Primary-structuretemperatures compare favorably with preflight predicted values.13


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0 East-side primary-structure temperature sao nd lu nal bn l0 East-side primary-structure temperature (eighth unation)0 West-side primary-structure temperature lsaond lunation )

Y n West-side primary-struct ure temperature (eighth lunation1400 0 Sunshield temperature. toplsecand lunationlhF 0 Sunshield temperature. to pleighth lunation1

0 20 40 M) 801001201401601802w220240260280Mo320340360- ~ I I I I I I I I I I I I I I I I I I I0 20 4) 60 80 1001201401M18020022024)260280300320340360

Sun angle, deg Sun angle, d q

Figure 1 7 . - Sunshield emperaturesFigure 18 . - Primary-structur e emper-recorded during the second and atures recorded during the secondeighth lunations. and eighth lunations.

EXPER IMENT PERFORMANCEThe te mperature variations of the PSE s ensor during the irst three lunar-day/lunar-night cycles are plotted in figure 1 9 . The operational temperature-measurementl imits were from 1 0 7 " to 1 4 3 " F. The tempe ratu re of the PSE sensor reached a maxi-mum of 1 3 4 " F during the first lunar dayand increased to a maximum of approximately1 4 5 " F during the third lunar day. Since the third day of operation, the maximum tem-

perature has remained at approximatel y the same level. During the first two lunarnights, the sensor temperatur e dropped below the lower limit of 1 0 7 " F. The minimumsensor tempera ture cannot be es tablished bec ause of the instrumentation limit of 1 0 7 " F,although the estimated minimum was 7 5 " F. At the beginning of the third lunar night,the PSE sensor Z - a x i s leveling motor was commanded on, dissipating an additional3 . 0 5 watts inside the experiment, and the sensor temperature stabilized at 1 2 6 " F.This method of operation was continued through all subsequent lunar-night operations.The out-of-tolerance condition of the P SE cons iderably reduces the poss ibilityof ob-taining complete lunar-surface tidal data.

In additio n to the loss of tidal data, con-siderable noise was recorded at lunar sun-160-150

- toheSE.heos trobableause of th e40- 0 PSE temperaturethlrdunationl was caused by expansionndontraction

0 PSE temperat urellrrtunatlOnl riseand unar unset.Thenoiseprobably0 PSE temperalure (second lunation)

of the multilayer-i nsulation skirt atta chedL.

- videheecessarynsulationoaintain10lunar surface and, therefore, did not pro-,insu lati on skir t had not been deployed prop--sensor temperature anomaly w a s that the

- Apollo 14 PSEncorporated a modified00

g 130 -DL

Y 20 - erl y. The ski rt would not lie flat on thec

thermal control of the sensor. Theskirt wi th the addition of weights and stitch-problems. Also, an ncrease n heater-

90o 2b 4b 610 80 loo ,b o d o 1 6 0 180 zoo 220 240 ing of the nsulation opreventdeployment..i1 1 . Iuun angle, degFigure 19 . - The PSE internal temper- power dissipation was incorporated tomaintain lunar-night temperature.atures recorded during the firstthree lunations.

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during lunar-day operation. The probableca use of the high-tempera ture conditionwas the contamination of ther mal- cont rolsurf aces by lunar dust deposited duringtheeploymentperation. romhoto- Ygraphs of the LSM, it was determinedthat apparently the dust was deposited 2-before the final stages of deployment,possibly during transport from the LMto the deployment site. Tne use of a dust

-aC I5b-

~

The temperature response of the LSM during lun ar-surfa ce operatio n is plottedin figure 20. The maxi mum temp erat ure limi t of approximately 150" F was exceeded

temperature (second lunationl.". ,- . temperature leighth lunationl250200150100500

- 50

0 LSM intern al temperature second l un ati on l'J LSM internal temperature leig hth una tionl

cover over the package to prevent dustdeposition during transport is planned f orfut ure Apollo mission s.Also, a sunshadewill be used over the electronics packageto mini mize sol ar illu mination of t hepackage during lunar noon.The resp onse s of the SIDE and CCIGduring lunar-surface operation are shownin figures 21and 22, respectively.Therequired tempera ture limits of -40" o176" F fo r SIDE electro nic componentswere maintained during exposure to lunar-nightand unar-dayconditions.However,because of err ati c ope rat io n of the exp er-iment during lunar day, the SIDE has notbeen operated continuously since the firstlunation.Therefore, he emperaturesduring succeeding lunations have been

considerably lower than during the firstlunar day. The temperatu re response s ofthe SWS during operation on the lu nar s ur-face are plotted n figure 23. The response

400 0 C C I G temperalure second luna tionl0 C C I G temperature leighth unationl3 0 0 1

Sun angle,deg

Figure 22. - The CCIG internal temper-atures recorded during the secondand eighth lunations.

- lOOLI_ I 1 I- L - I I I I I I 1 1 I I I I I0 20 40 60 80 100 120 140 160 180 200 220 240 260 280300320340 360Sun angle,degFigure 20. - The LSM internal temper-atures recorded during the secondand eighth lunations.

jo0

0 Average SIDE temperalure second l un ali on l0 Average SIDE temperature lelghth unationl

250

2!2ool50i- 5 0 L . 1 I 1 1 1 1 . 1 . 1 1 1 I I I I I I I I0 20 4060 80100 120 140 160 180 200 220 240 260280 300 32 0 340 360Sun angle, deg

Figure 21. - The SIDE internal temper-atures recorded during the secondand eighth lunations.400 0 S W S electronics-package emperature second lun ati on l0 S W S electronics-package temp erat ure teig hlh una lion l

0 S W S Faraday-cup emperature second lun ati onlA SW S Faraday-cup emperature leigh th unati on)20 0

- 2 o o L-3000 20 4b 6b 80 1 k i;o 1 I A lo zb o 210 2fio 2 io 2Ao 3Ao 310 3 k 3 LSun angle, degFigure 23. - The SWS internal temper-atures recorded during the secondand eighth lunations.

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of the SWS electronic components occurred within the required temperature limits of14" to 167" F, and the thermal-con trol system of the experiment performed as expectedon the lunar surface.

C O M P A R I S O N OF FLIGHT, TEST, A ND AN AL YT ICA L RESULTSThe average central-station radiator temperatures are compared with preflight

analytica l and test results in figure 24. The radi ator tempe ratur es were lower duri nglunar-surfa ce operati on than had been pre-dicted, although postflight analysis, basedon the actual configuration, provided goodcorrelation (fig.16).Preflightvalues ofprimary-structure temperatures are com-pared with actual lunar-surface tempera-ture vari atio ns in figu re 25. The flightresul ts for these measurements were in-dicative of a close correlation with pre-flight predictions and thermal-vacuum-testresults. Flight results for sunshield tem-per atu res (fig. 26) were considerab lyhigher than analytica l and test resul ts .Dust deposited on the sunshield during de-ployment was the probable cause of t hi sdiscrepancy.

0 East-side primary-structure temperature (eighth lunationl0 East-side primary-structure temperature lsecond lunatmnl0 West-side primary-structure temperature lsecond lunatio'nlA West-side primary-structure temperature leighth lunatio nl

Figure 2 5 . - A comp aris on of int erna lprimary-structure temperatures,recorded during lunar-surfaceoperations, with analytically pre-

0 Average adiator-plate emperature second unationlAverage adiator-plate emperature eighth unationl- - Predicted temperature envelope

." 150

Figure 24. - A compa riso n of ave rageradiator temperatures, recordedduring lunar-surface operations,with the analytically predictedtemperatures.

0 Sunshieldemperature.top lsecond lunationl0 Sunshield temperature.top leiqhth lunationl

Predicted temperature

Sun angle, d q

Figure 26. - A com par iso n of sunshieldtemperatures, recorded duringlunar-surface operations, withdictedemperatures.nalyticallyredictedemperatures.

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DES GN MOD I FI CAT1ONS

."Modifications to the central-station thermal design have been necessitated by arequirement to deploy the ALSEP at higher lati tudes on the moon. The basic ALSEPdesign was intended to provide thermal controlwhen deployed at latitudes *5" from the

lun&equator.However,selecteddeploy-ment sites now include latitudes consider-ably more than 5" from the equator . Forthese deployment sites, it is necessary toclose t he side of the c entral station thatwould face the equator after deployment.This change was made so that no solarradiati on would impinge directly on theradiator surface. The side was closed byuse of a multilayer-insulation curtain(fig. 27) . Additionalmodifications o heinsulation mask on the radiator were re-quired to obtain the radiating area neces-sary for maintaining adequate thermalcontrol. ,With these design change s, theALSEP central-station thermal-controlsys tem is capable of maintaining adequatethermal control at lati tud es of as muchas 45" rom the lunar equator .

Figure 2 7 . - The ALSEP design forhigh-latitude deployment.

CONCLUDING REMARKSThe f irs t f l ight modelof the Apoll o lunar surface expe riments pac kage was de-ployed on the lunar surface during the Apollo 12 mission during November 1969. Forapproximately 2 y e ar s on the moon, the experiments package has transmitted scientificand engineering data to receiving stations on earth. The passive-thermal-control sys-tem that is used to maintain central-station temperatures has functioned satisfactorilyduring this operat ing period. The tempera ture of the central-station radiator plate,although lower than indicated in preflight predictions, has been maintained within theoperat ing l imits necessary to provide the required rel iabi l i tyf the central -stationelectronic components. However, several problems were encountered with thermalcontro l of exp erim ent s on the first flight package, particularly the passive seismic andmagnetometer experiments. Modifications have been made to these experiments toimprove the thermal control for future f l ights .The thermal-control system has provided the passive thermal control requiredto withstand the environments encountered during storage, translunar flight on boardthe lunar module , and deployment on the lun ar sur face . The basic thermal design hasmaintained central-station temperatures adequately during thermal-vacuum testing andduring operation on the lunar surface. The analytical models that were developed topredict the thermal performance have described the central-station temperature

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. . . . . . , . .

distribution accurately under lunar-surface conditions. With the described modifica-tions, the central-station thermal design will provide the necessary thermal protectionfor the Apollo lunar surface experiments packages to be deployed on future lunar-landing missions.

Manned Spacecraft CenterNational Aeronautics and Space AdministrationHouston, Texas, December 8 , 1971514-40 -73 -90 -72

REFERENCE

1 . Collicott, H. E. ; andMcNaughton, J. L . : Thermal Control in a Lunar Environ-ment.BendixTech. J . , vol. 3, no. 1 ,1 9 7 0 , pp. 1 - 1 5 .

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APPENDIXEARLY APOLLO SCIENTIFIC EXPERIMENTS PACKAGE

During preparation for the first lunar-landing mission, Apollo 11, the decisionw a s made to reduce the amount of time required to deploy scientific experiments.Therefore, the EASEP, a simplified version of the ALSEP, was developed for.deploy-ment during the first lunar-landing mission. The EASEP consisted of a passive-seismi c-expe riment packa ge (PSEP ) (fig. A- 1), which was a combination of the PSEand the centra l statio n, and of the las er ran gin g ret ror efl ect or (LRRR) (fig. A-2).Secondsurface

(a ) Subsy stems. (b) Subsystemsomponents.Figure A-1. - The Apollo 11 PSEP configuration.

(a) Stowed. (b) Deployed.Figure A - 2 . - The LRRR configuration.

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The PSEP thermal design was basedon allowable average radiator-plate tem-peratures from -65' to 140" F. Power forthe P SEP was s upplied by a solar-cel l ar-ray,and, herefore, heexperimentdid not r

perateduringhe unar night.Hence, it 3 . 2 i n .was necessary to use isotopic heaters tomaintain lunar-night temperatures greaterthan -65" F to ensure the required rel iabi l-ity. Two 15-wat t sotopic heater s (fig. A-3).were attached to the radiator plate as shownin figure A-1. To reduce thesolar-heat in-put.during the lunar-day operation, theradiator plate was covered with second-surface mirrors that had a solar absorp-tance of approximately 0.08 and, at thesame time, maintained a high emittance ofapproximately 0.8. The total area coveredby the mirrors was 2.60 square feet .

The LRRR was a passive experimentdesigned to reflect laser radiation fromearth-basedstations.Thesupport-structure pallet provided a s t ruc tura l baseand a therma l decoup ling of the refl ect orarray from the lunar surface. A white,thermal-control coating (zinc-oxide/potassium silicate) w a s used on the palletto provide a low temperature gradient be-tween the reflector array and the pallet.

The predicted PSEP radiator-platetemperature is compared with the actualtemperatu re recor ded on the lunar surfacein figure A-4. The actual radiator-platetemperature was approximately 50" Fhigher than was expected. The most prob-able cau se of th e overhe ating was opticaldegradation of th e PSEP radia tor/sec ond-surface mirrors , resul t ing from contami-nants deposited during the LM ascent. Thedepositions could have consisted of l una rdust , descent-stage debris , or combustionproducts.Analyticallypredicted empera-

-3.0 in. dam- /-6 grams ofplulonium-238microspheres

L A l u m i n u mbase plate

Figure A-3. - A diagram of the internalstru ctur e of a PSEP isotope heater.

Predicted (degraded mirrors1Predicted undegraded mirmrslcI"--"_

u s Solar absorptivity o f90 - second-surface mirrors80 -

July 1969 I August 1969Figure A-4. - A compar ison of PS EPradiator-plate temperatures, re-corded during lunar-surface opera-

tions, with analytically predictedtemperatures.

tures for degraded second-surface mir rors a l s o a r e given in figure A-4. The pre-dicted temperatures for the degraded condition compare favorably with the actual tem-peratures recorded during lunar-surface operat ion.

Documents

Apollo Experience Report Thermal Design of Apollo Lunar Surface Experiments Package