Full report

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NASA/TM—2007–214957 Programmable Thermostat Module Upgrade for the Multipurpose Logistics Module D.W. Clark, S.D. Glasgow, S.E. Reagan, K.H. Presson, D.E. Howard, and D.A. Smith Marshall Space Flight Center, Marshall Space Flight Center, Alabama May 2007

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The NASA STI Program…in Profile Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program Office plays a key part in helping NASA maintain this important role. The NASA STI program operates under the auspices of the Agency Chief Information Officer. It collects, organizes, provides for archiving, and disseminates NASA’s STI. The NASA STI program provides access to the NASA Aeronautics and Space Database and its public interface, the NASA Technical Report Server, thus providing one of the largest collections of aeronautical and space science STI in the world. Results are published in both non- NASA channels and by NASA in the NASA STI Report Series, which includes the following report types: • TECHNICAL PUBLICATION. Reports of completed research or a major significant phase of research that present the results of NASA programs and include extensive data or theoretical analysis. Includes compilations of significant scientific and technical data and information deemed to be of continuing reference value. NASA’s counterpart of peerreviewed formal professional papers but has less stringent limitations on manuscript length and extent of graphic presentations. • TECHNICAL MEMORANDUM. Scientific and technical findings that are preliminary or of specialized interest, e.g., quick release reports, working papers, and bibliographies that contain minimal annotation. Does not contain extensive analysis. • CONTRACTOR REPORT. Scientific and technical findings by NASA-sponsored contractors and grantees. • CONFERENCE PUBLICATION. Collected papers from scientific and technical conferences, symposia, seminars, or other meetings sponsored or cosponsored by NASA. • SPECIAL PUBLICATION. Scientific, technical, or historical information from NASA programs, projects, and missions, often concerned with subjects having substantial public interest. • TECHNICAL TRANSLATION. Englishlanguage translations of foreign scientific and technical material pertinent to NASA’s mission. Specialized services also include creating custom thesauri, building customized databases, and organizing and publishing research results. For more information about the NASA STI program, see the following: • Access the NASA STI program home page at http://www.sti.nasa.gov • E-mail your question via the Internet to help@sti.nasa.gov • Fax your question to the NASA STI Help Desk at 301– 621–0134 • Phone the NASA STI Help Desk at 301– 621–0390 • Write to: NASA STI Help Desk NASA Center for AeroSpace Information 7115 Standard Drive Hanover, MD 21076–1320

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NASA/TM—2007–214957 Programmable Thermostat Module Upgrade for the Multipurpose Logistics Module D.W. Clark, S.D. Glasgow, S.E. Reagan, K.H. Presson, D.E. Howard, and D.A. Smith Marshall Space Flight Center, Marshall Space Flight Center, Alabama Natonal Aeronautcs and Space Admnstraton Marshall Space Flght Center • MSFC, Alabama 35812 May 2007 

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TRADEMARKS Trade names and trademarks are used in this report for identification only. This usage does not constitute an official endorsement, either expressed or implied, by the National Aeronautics and Space Administration. Avalable from: NASA Center for AeroSpace Informaton 7115 Standard Drve Hanover, MD 21076 –1320 301– 621– 0390 Ths report s also avalable n electronc form at <https://www2.st.nasa.gov> 

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TABLE OF CONTENTS 1. BACKGROUND ............................................................................................................................ 1 2. MULTIPURPOSE LOGISTICS MODULE PROGRAMMABLE THERMOSTAT SYSTEM ............................................................................................................ 3 3. HARDWARE DEVELOPMENT ................................................................................................... 7 3.1 Radiation Susceptibility Tests ................................................................................................. 7 3.2 Bond Strength Tests ................................................................................................................ 7 4. HARDWARE QUALIFICATION AND ACCEPTANCE ............................................................. 9 5. STS-121 MULTIPURPOSE LOGISTICS MODULE SHELL HEATER OPERATIONS ............ 13 6. STS-121 PROGRAMMABLE THERMAL MODULE DATA ANALYSIS ................................. 17 7. FUTURE APPLICATIONS ............................................................................................................ 22 REFERENCES .................................................................................................................................... 23 

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LIST OF FIGURES 1. Illustration of MPLM stowed in the Space Shuttle payload bay ........................................ 1 2. Programmable thermostat hardware ................................................................................... 3 3. MPLM PTM electrcal block dagram ................................................................................ 5 4. MPLM PTM environmental test fixture ............................................................................. 9 5. PTM flight qualification test flowchart ............................................................................... 10 6. PTM flight acceptance flowchart ........................................................................................ 10 7. STS-121 MPLM/ISS closeout condtons (78 °F set pont, ± 0.4 °F control band) ........... 14 8. Predcted MPLM 28 V shell heater power (217 h to 230 h MET) ..................................... 15 9. Predcted MPLM 28 V shell heater power (230 h MET to EOM) ..................................... 15 10. MPLM heater energy profile .............................................................................................. 17 11. MPLM heater power profile ............................................................................................... 18 12. MPLM external configuration ............................................................................................ 19 13. Shuttle orbiter coordinate system ....................................................................................... 19 14. MPLM aft cylinder PTM temperatures .............................................................................. 20 15. MPLM CBM PTM temperatures ........................................................................................ 21 16. MPLM grapple fixture PTM temperatures ......................................................................... 21 v

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LIST OF TABLES 1. MPLM programmable thermostat component test matrx ................................................... 11 2. Qualification and acceptance vibration levels ...................................................................... 11 3. Thermal cycle ranges ........................................................................................................... 12 v

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LIST OF ACRONYMS ALTEC Advanced Logistics Technology Engineering Center APU auxiliary power unit CBM common berthng mechansm C&DH command and data handlng DDT&V design, development, testing, and verification DRM data recorder module EOM end of msson EEE electronc, electrcal, and electromagnetc EMI/EMC emissions induced/compatibility FD flight day FRGF flexible releasable grapple fixture GRAP grapple GSE ground support equipment GUI graphcal users nterface ISPR international standard payload rack ISS Internatonal Space Staton JOP Jont Operatons Panel JSC Johnson Space Center KSC Kennedy Space Center MET msson elapsed tme v

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LIST OF ACRONYMS (Continued) MIP msson ntegraton plan MLI multilayer insulation MOD Msson Operatons Drectorate MPLM multpurpose logstcs module MSFC Marshall Space Flght Center MTBF mean tme between falure NPRV negatve pressure relef valve PDA payload disconnect assembly PPRA positive pressure relief assembly PTM programmable thermostat module RTD resstve temperature devce SEE sngle event effects SINDA systems improved numerical differencing analyzer SRB sold rocket booster STS Space Transportation System TAU transaxal accelerometer unt TM Techncal Memorandum T/P temperature/pressure ULF utilization and logistics flight v

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NOMENCLATURE P1 ISS closeout ar pressure P2 NPRV/PPRV mnmum crack pressure T1 ISS closeout ar temperature T2 MPLM final air temperature v

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TECHNICAL MEMORANDUM PROGRAMMABLE THERMOSTAT MODULE UPGRADE FOR THE MULTIPURPOSE LOGISTICS MODULE 1. BACKGROUND The multipurpose logistics module (MPLM) is a pressurized module used for transporting international standard payload racks (ISPR), consumable supplies, and various other logistical items to and from the International Space Station (ISS) (fig. 1). The 21-ft-long by 15-ft-diameter aluminum canister can transport up to 20,000 lb of payload in a pressure and temperature controlled environment. The environment inside the MPLM is maintained by pressure relief valves (both positive and negative), external multilayer insulation (MLI) blankets, and a shell heater system located on the structural skin. The nternal temperature and pressure of the module are controlled va the heaters to ensure the followng: (1) preventon of condensaton nsde the MPLM (60 °F maxmum dewpont, (2) preventon of actuation of either the positive pressure relief assembly (PPRA) or the negative pressure relief valve (NPRV), (3) mantenance of the MPLM nternal cabn ar temperature between 50 to 113 °F, and (4) mantenance of the MPLM cabn ar pressure n the range of 13.9 to 15.2 psa. From an operatonal perspectve, an MPLM msson has three dstnct phases. Phase 1 occurs from launch through hatch openng on the ISS. Phase 2 occurs whle the hatch s open to the ISS, and phase 3 is the time period between hatch closure on ISS through landing. Phase 3 is typically the only period when the 28 V heaters are operated. During this portion of the mission, the MPLM cabin ar envronment must be mantaned between the postve and negatve pressure relef valve actuaton pressures (PPRA and NPRVs) and above the local dewpont temperature. Figure 1. Illustration of MPLM stowed in the Space Shuttle payload bay. 1

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The initial MPLM shell heater system design utilized 3200 Series Elmwood thermostats to provide temperature control. Unfortunately, the thermostat set points were so high (81 to 95 °F set pont range) that the MPLM PPRAs would actuate durng a nomnal msson tmelne. The rsk of actuating PPRAs during on-orbit operations could jeopardize MPLM mission objectives if a valve falure were to occur. Ths scenaro would result n the loss of valuable make-up consumables from either the ISS or Space Shuttle. Furthermore, the higher set points required additional Shuttle cryogenic resources to operate the fuel cell power supply used to drive the MPLM shell heaters. To compensate for the high set points, the MPLM shell heaters were operated manually. Heater switches, located in the Shuttle’s aft flight deck, were cycled on/off by the flight crew. Preflight thermal analyses were used to define approximate heater duty cycles, while real-time telemetry was used to “fine-tune” the heater on/off times to meet mission objectives. This effort required real-time Mission Operatons Drectorate (MOD) support to coordnate crew actvtes n order to perform these tasks. Another drawback of manual heater operations lies in the fact that the MPLM shell heaters could only be operated while the crew was awake. Extended heater cycles during crew sleep periods could raise the nternal MPLM ar pressures above the PPRV pressure lmts. These constrants proved to be both cumbersome and inefficient for real-time flight operations. In October 2000 the MPLM Project Office presented a proposal to the ISS Program Office for developing solid state programmable thermostats that would replace the bimetallic disk-style devces. These sold state thermostats offered several advantages ncludng tghter temperature control, selectable set points, and closed-loop feedback control capability. These features, in turn, would result in greater operational flexibility during future ISS missions. Ths Techncal Memorandum (TM) dscusses the programmable thermostat module (PTM) project development cycle and first time use of these state-of-the-art thermostats. 2

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1. MULTIPURPOSE LOGISTICS MODULE PROGRAMMABLE THERMOSTAT SYSTEM The MPLM has two sets of heaters and thermostats, one operatng on 28 V power and one operating on 120 V power. The 28 V string is powered from the Space Shuttle’s fuel cell power supply and is used while the MPLM is in the Shuttle’s payload bay. The 120 V string is powered by the ISS and is used when the MPLM is attached to the ISS. The 28 V heater system consists of 22 thermostatically controlled heater crcuts and 66 ndvdual Kapton (a DuPont product) resstve element heater pads. Only the 28 V thermostats were replaced with the new PTMs. Fgure 2 llustrates the new PTM and ts coupled sensor, an external resstve temperature device (RTD). The PTM module design consists of a secured printed wiring board assembly mounted in an aluminum housing. The aluminum housing is affixed to a mounting bracket with four setscrews. The carrier bracket, in turn, is secured to the MPLM pressure shell with a high strength epoxy adhesive. This installation design allows for easy replacement of failed units. Real-time temperature monitoring s accomplshed wth the RTDs. 28 V Removed Wiring Fuse 28 V RTN Module-To-Carrier Mounting Screws Programmable Thermostat Module Thermal Pad Communications Connector Existing Thermostat Shell RTD Sensor Existing Shell Heaters Carrier Epoxy Fgure 2. Programmable thermostat hardware. 3

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In the upgraded 28 V heater network, 20 PTM/RTD assembles and a data recorder module (DRM) replaced the bimetallic disk-type thermostats. The DRM records various PTM flight parameters (temperature, on/off status, and other assocated health montorng parameters). Two crcuts were left unchanged in the new configuration as a result of design constraints. Each PTM/DRM module contans two nterfaces. One s an electrcal nterface, whle the other s the communcatons lnk for command and data handlng (C&DH). The electrcal nterfaces consst of the 28 V power supply/return and RTD wiring, while the C&DH interface is achieved through a RS-485 communications cable and 21-pin micro “D” metal shell connectors. The DRM interfaces are dentcal to the PTMs wth the excepton of the RTD pgtal leads. The PTM electrical installation was accomplished by clipping the leads at the bimetallic terminal interfaces and splicing into the main 28 V harness power supply/return lines. The RTDs were mounted no more than 36 n (and no closer than 6 n) from the PTMs near the exstng bmetallc thermostats. Mounting distances were optimized through thermal analysis utilizing the systems improved numerical differencing analyzer (SINDA). The maximum distance is driven by the controllability of the heater zones while the minimum distance is chosen to avoid thermal contamination of the sensor by the controller. Key design features of the PTM system include: • Size: 2.25 in × 1.75 in × 0.5 in • Weght: < 75 g (w/o carrer); < 100 g (w/carrer) • C&DH: RS-485 seral communcaton protocol • Software: graphcal users nterface (GUI) developed for programmng and montorng • Input Power: +9 to +28 Vdc • External RTD temperature sensor • External heater: up to 5 A at +28 Vdc • Programmable temperature set ponts and span. Set pont/span resoluton: 0.1 °C • DRM avalable n the same housng for recordng status and temperature data for up to 32 PTM unts connected on a sngle RS-485 bus. Fgure 3 s the electrcal block dagram of the new MPLM 28 V PTM heater network. The RS-485 communcaton cable provdes the C&DH lnk for the 20 PTMs and DRM. A ground support equipment (GSE) computer is used to upload PTM control parameters (set points, error span, and data acquisition rates) during pre-mission ground processing operations at Kennedy Space Center (KSC). Post-mission data retrieval is also performed with the GSE computer. No C&DH capability is available durng real-tme msson operatons. 4

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RS-485 Serial Interface GSE Computer GND GSE Computer J1-2 Computer Present Interface J1-10 Connector Data Black Recorder Notes: 1. Address lines for each thermostat are: Addr0 J1-7 float or ground to J1-6 Addr1 J1-18 float or ground to J1-8 Addr2 J1-17 float or ground to J1-5 Addr3 J1-20 float or ground to J1-10 Addr4 J1-12 float or ground to J1-3 2. J1 is a 21-pin connector. The other unlabeled pins are used for test purposes. 28Vdc J1-1 Input Power J1-13 J1-14 Red J1-15 Black Heater 1 Orange Thermostat Brown No. 1 RTD 1 Yellow Blue J1-1 J1-13 Red J1-14 J1-15 Black Heater 2 Thermostat Orange No. 2 Brown RTD 2 Yellow Blue J1-1 J1-13 Red J1-14 J1-15 Black Heater 3 Thermostat Orange No. 3 Brown RTD 3 Yellow Blue J1-1 J1-13 Red J1-14 J1-15 Black Heater 21 Thermostat Orange No. 21 Brown RTD 21 Yellow Blue Fgure 3. MPLM PTM electrcal block dagram. 5

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1. HARDWARE DEVELOPMENT The MPLM project office at NASA Marshall Space Flight Center (MSFC) was responsible for managing all of the design, development, testing, and verification (DDT&V) activities of the PTM project. DDT&V activities, including environmental flight qualification and acceptance testing, were performed using the available infrastructure and engineering support personnel at MSFC.1The PTM circuit boards were outsourced to a local electronics vendor for manufacturing. However, the final electronics box-level assembly operations, including potting and wire staking, were completed at MSFC. The Boeing/Huntsville division was responsible for providing the RS-485 communication cable design drawings, while the Boeing/KSC division completed the manufacture, test certification, and installation of the flight cable. MSFC relied upon the Advanced Logistics Technology Engineering Center (ALTEC) (the Italian Space Agency MPLM-sustaining engineering partner) to provide detailed installation drawings of the PTM mounting design and RS-485 cable routing layout to KSC. 3.1 Radiation Susceptibility Tests A key decision made early in the project design phase involved using industrial grade electronic, electrical, and electromagnetic (EEE) parts in the circuit board design in lieu of more expensive radiation hardened parts. The technical risk was judged to be acceptable, as the on-orbit thermal environment is consistent with industrial grade parts qualifications. Furthermore, the PTMs are located in a benign radiation environment underneath external MLI blankets and micrometeoroid shielding. To demonstrate the functional capability of these parts in a space environment, a series of radiation tests was performed on prototype units. Two thermostats and a data recorder were subjected to “proton” or “heavy ion” testing at the Indiana University Cyclotron Facility for single event effects (SEE). These units were subjected to an equivalent amount of radiation that would be expected in 10 years of continuous operation on the ISS. The test results demonstrated that the data recorder and thermostat units exceeded the onorbit mean time between failure (MTBF) design requirement of 365 days (equivalent to the MPLM 25 mission life design requirement) without error or incident.2 The MTBF design limit for the DRMs was determined to be 447.5 days. The PTMs exhibited no effects from the radiation testing. The DRM MTBF limit was due to data memory effects. However, the DRM design contains redundant memory banks to compensate for this. The ISS EEE Parts Board approved a design waiver upon the successful completion of these radiation tests. 3.2 Bond Strength Tests Two bonding tests were performed to assess the bonding material and installation procedure of the PTM/DRM carrier brackets to the MPLM pressure shell. The installation procedure was based 

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on a mcrotransaxal accelerometer unt (TAU) stran gauge bondng process developed at KSC. RTV-566 epoxy adhesive was the bonding agent used for the PTM carrier bracket mounting design. A single PTM was mounted on a Space Shuttle solid rocket booster (SRB) test fixture to perform er bracket mountng concept.3 The SRB test fixture was vbraton development testng of the PTM carr chosen for the development testing because its radius of curvature is approximately equal to that of the MPLM structural shell. Pror to performng the bond/vbraton tests, a statc load test was performed (n shear plane) on the bonded PTM. The PTM remained affixed to the SRB test fixture and successfully met the 70-lbf strength requirement called out in the MicroTAU procedure. A second bond test was performed to determne the ultmate tensle strength of the RTV-566 adhesive bond. The “pull to failure” ultimate strength of the RTV-566 adhesive was measured to be 1,116 lbf n the shear plane. The results obtaned from these development tests valdated the PTM RTV-566 mountng nstallaton concept. 8

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1. HARDWARE QUALIFICATION AND ACCEPTANCE All PTM qualification and acceptance testing was performed at MSFC’s environmental test facltes. Ths ncluded electrcal emssons nduced/conductance (EMI/EMC), random vbraton/ structural, and thermal cycle flight testing. Figure 4 shows the test fixture that was developed for the PTM flight qualification/acceptance testing.4 Figure 4. MPLM PTM environmental test fixture. Flight certification testing utilized a lot qualification/acceptance test approach. A special test fixture was designed to accommodate 25 PTM/DRM units during a single test flow sequence. All testing was performed in accordance with the standards and guidelines established by the ISS program in SSP 41172, “Qualification and Acceptance Environmental Test Requirements.”5EMI/EMC test standards are defined in NSTS-21000-IDD-ISS, “International Space Station Interface Definition Design Documents.”6 Each PTM and DRM was acceptance tested to ensure workmanship only at the electronic box assembly level; no component testing was performed at the circuit board assembly level. Instead, quality 9

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surveillance was maintained at the vendor’s facility through visual workmanship and inspection audits at all levels durng the prnted crcut board manufacturng process. These audts were performed pror to component testng of the potted electronc module assembles. A total of 100 PTM assembles and 6 DRM unts were manufactured n ths development effort. Figures 5 and 6 are flowcharts representing the environmental test flow paths performed during this hardware development campaign. Ten PTMs and a single DRM were tested during the flight qualification phase, while four separate hardware acceptance test flows were completed on the remaining PTM/DRM units. The first three acceptance test lots consisted of 23 PTMs and 1 DRM, while the final acceptance flow consisted of 24 PTM and 2 DRMs. Initial Burn-in Functional Final Thermal Functional Vacuum 2.6 2.4 EMI/EMC Intermediate 2.2 Functional Random Intermediate Vibration Functional 2.3 Figure 5. PTM flight qualification test flowchart. Module Initial Burn-in Functional 3.1 Final Thermal Functional Vacuum 3.5 3.3 Random Vibration 3.2 Intermediate Functional Figure 6. PTM flight acceptance test flowchart. 10

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Table 1 lsts the component test matrx for all of the PTM/DRM hardware tested. Ths matrx cross-references to which qualification or acceptance tests each PTM or DRM unit was subjected. Module-level electronc burn-n tests were performed on all of the unts pror to the envronmental testing. For the EMI/EMC qualification tests, only those PTM and DRM units that were manufactured first were subjected to EMI/EMC tests prior to the start of the flight qualification testing. Table 1. MPLM programmable thermostat component test matrx. Qualification Acceptance Component Burn-In EMI/EMC Vibration Thermal Vibration Thermal Thermostat 1 X X 2 – 10 X 11 – 100 X Data Recorder 1 X X 2 – 6 X X X X X X X X X X X The vibration levels and thermal cycles for the qualification tests were set in order for the hardware to qualify for 25 flights, which is the design mission life of each MPLM.7,8Table 2 lsts the qualification and acceptance vibration levels, while table 3 lists the qualification and acceptance thermal cycling temperature ranges. These levels are defined in the PTM and DRM end item specification documents. It should be noted that all testing performed during flight qualification and acceptance was successful wth no hardware falures noted. Table 2. Qualification and acceptance vibration levels. Qualification1Level Acceptance2Level Frequency (Hz) 2 2 20 0.04 g /Hz 0.01 g /Hz 20 to 65 +7.6 dB/Octave +7.6 dB/Octave 2 2 65 to 180 0.8 g /Hz 0.2 g /Hz 180 to 360 –7.0 dB/Octave –7.0 dB/Octave 360 0.16 g2/Hz 0.04 g2/Hz 360 to 1,400 –2.6 dB/Octave –2.6 dB/Octave 1,400 0.05 g2/Hz 0.0125 g /Hz 2 1,400 to 2,000 –4.9 dB/Octave –4.9 dB/Octave 2 2 2,000 0.028 g /Hz 0.007 g /Hz Composite 16.8 grm 8.4 grm 1 Qualification duration = 810 s in each of three mutually perpendicular axes. 2 Acceptance duration = 60 s in each of three mutually perpendicular axes. 11

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Table 3. Thermal cycle ranges. Low Temperature Qualification –24 °F Acceptance –4 °F 12 High Number Temperature of Cycles +156 °F 24 +136 °F 8

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1. STS-121 MULTIPURPOSE LOGISTICS MODULE SHELL HEATER OPERATIONS The STS-121/ULF1.1 ISS mission was launched on July 4, 2006. This was the first flight of the fully automated MPLM 28 V shell heater system. During the six previous MPLM missions, the shell heaters were manually cycled to maintain temperature/pressure (T/P) control within power requirements defined in the ISS mission integration plan (MIP). Beginning with this mission, however, the automated PTM system posed new challenges for conducting the MPLM heater operations due to the fact that the PTMs cannot be reprogrammed from the ground during flight operations. In order to meet operational requirements with the PTM heater system, a new flight rule had to be developed for the STS-121 mission. This rule defined the range of acceptable cabin air T/P conditions prior to the MPLM hatch closure. The desired ISS cabin air properties are functions of the final MPLM cabn ar temperature and the NPRV/PPRA crack pressures. The ISS closeout condtons were derved n the followng manner:  T2  T1 = P1   (1)  P2  where: T1= ISS closeout ar temperature T2 = MPLM final air temperature P1= ISS closeout ar pressure P2= NPRV/PPRV mnmum crack pressure T1values represent ISS closeout ar temperatures that are calculated over a range of P1closeout pressure condtons. T2 is the MPLM cabin air temperature at deorbit and is represented by the steadystate MPLM shell temperature (PTM heater set pont). P2pressures are the mnmum as-tested crack pressures of the NPRV and PPRA valves flown during this mission. Adjustng T2 values upward or downward by the temperature control span simulated the PTM temperature control errors. A temperature control span of 0.4 °F was selected for ths msson to ensure that a tght control range about the desred set pont would be mantaned at all tmes. For the NPRV lmt lne calculatons, T2values were adjusted downward. For the PPRA lmts, these values were adjusted upward. T1temperatures were plotted aganst P1 closeout pressures. The resultant T/P curves define the NPRV and PPRA crack pressure limits at MPLM hatch closure. Any ISS cabin air T/P combination that lies between these limit lines and above the ISS local dewpoint will satisfy pressure and condensation requirements for the MPLM hardware. 13

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ISS closeout conditions for six discreet PTM set point cases were analyzed for this mission. The optimum mission set point was selected from the corresponding closeout chart which completely bounded ISS cabn ar T/P condtons between the NPRV/PPRA crack pressure envelope. Figure 7 is the MPLM/ISS closeout flight rule that was developed for the STS-121 mission. This flight rule is based on a 78 °F PTM heater set point. The corresponding heater control range is 77.6 to 78.4 °F (25.2 to 25.6 °C). 90 85 NPRV Crack Limit 80 Desired Closeout Region 75 ISS Nominal [T,P] Range 72–74 °F @ 14.65–14.75 psi PPRA Crack Limit 70 Acceptable Closeout , MPLM Closeout Temperature (°F) 1 T 65 MPLM Maximum Dewpoint Limit 60 14.5 14.55 14.6 14.65 14.7 14.75 14.8 14.85 14.9 14.95 P1, MPLM Closeout Pressure (psia) Fgure 7. STS-121 MPLM/ISS closeout condtons (78 °F set pont, ± 0.4 °F control band). Finally, a thermal analysis was performed to determine whether the PTM mission set point would meet the STS-121 MIP power budget requirements.9The MPLM heater power assessment was completed by ALTEC using the SINDA thermal analysis software program. The SINDA model assumed nominal Shuttle bay-to-Earth orbital heating rates and an ISS closeout air temperature of 72 °F for the initial conditions in the analysis. The ALTEC analysis predicted 28 kWh of heater power used during nominal time lined end of mission (EOM) heater operations with an additional 8 kWh used during mission extension days. The STS-121 MIP allocated 30.5 kWh of heater power for nomnal operatons (at 278 h msson elapsed time (MET)) and 16 kWh power for the additional contingency orbit days. The ALTEC model results met the STS-121 MIP requirements and were presented to Johnson Space Center (JSC) STS-121 Joint Operations Panel (JOP) for formal flight approval.10Fgures 8 and 9 are the heater power levels predicted by the ALTEC SINDA model. 14

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16,000 14,000 12,000 10,000 8,000 6,000 Energy (Wh) 4,000 2,000 0 –2,000 210 215 220 225 230 235 Time (h) Fgure 8. Predcted MPLM 28 V shell heater power (217 h to 230 h MET). 40,000 35,000 30,000 25,000 Energy (Wh) 20,000 15,000 10,000 230 240 250 260 270 280 290 300 310 Time (h) Fgure 9. Predcted MPLM 28 V shell heater power (230 h MET to EOM). 15

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1. STS-121 PROGRAMMABLE THERMAL MODULE DATA ANALYSIS The STS-121 flight was the first time that MPLM shell temperatures were recorded during ISS flight operations. The data obtained from the DRM indicated that the PTM system performed exceptionally well. The MPLM shell heaters operated for 61 hours, beginning shortly after the MPLM was returned to the Shuttle payload bay and ending ≈1 h prior to deorbit operations. Post-mission data analysis indicated that all 20 PTMs functioned as designed and maintained the MPLM shell temperatures within the expected temperature control band. The flight day 12 (FD12) telemetry data obtained during the MPLM environment check indicated that some of the individual heater circuits had begun to cycle off. This was verified by current readings recorded on the heater circuit screen displays. Figures 10 and 11 are plots of the shell heater energy and power profiles, respectively. Figure 10 shows the total heater energy calculated from the recorded heater on/off duty cycles. A total of 23 kWh of energy was used during the STS-121 mission, slightly less than ALTEC’s predicted model value. Energy (kWh) 25 20 15 Orbiter APU Port APU Port Attitude Timeline: Sidewall Sidewall 10 Attiude Attiude Total Energy (kWh) 5 0 0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 MET from PTM Powerup (h) Figure 10. MPLM heater energy profile. 17

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Total Power 1,000 900 800 700 600 500 Total Power (W)400 300 Orbiter APU Port APU Port Attitude Timeline: Sidewall Sidewall 200 100 0 0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 MET from PTM Powerup (h) Figure 11. MPLM heater power profile. Figure 11 shows the heater power profile. The shell heaters were running at 100 percent duty cycle during the first six hours of heater operations. The lower than expected energy usage is attributed to off-nominal flight attitudes flown during the last two mission days, as the Shuttle was oriented a in portside, sun-facing trajectory (–Y direction) during portions of FDs 12 and 13. These unplanned flight trajectories were driven by problems associated with the Shuttle’s auxiliary power unit (APU) fuel system. Figure 12 is an isometric view of the MPLM external configuration, while figure 13 references the coordinate system of the MPLM in the Shuttle’s payload bay. The Shuttle’s –Y axis points to the portside of the MPLM. This direction points outward from the flexible releasable grapple fixture (FRGF) located below the support bracket for the fluid payload disconnect assembly (PDA) shown in figure 12. The Shuttle’s –X axis points outward from the forward end cone. 18

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CBM Ring MOPS Panel Support Bracket for Fluid PDA Stablizer Trunnion FRGF Main Trunnion Support Bracket for Electrical PDA Stablizer Trunnion FRGF Main Trunnion Figure 12. MPLM external configuration. Zo 400 in 236 in Yo (Starboard) (Xo, Yo, Ao) = (0, 0, 0) –Xo –Yo (Port) –Zo C Payload BayL Xo Figure 13. Shuttle orbiter coordinate system. 19

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The thermal effects arsng from the Shuttle –Y port atttudes are llustrated n some of the individual PTM temperature profile plots below. These influences are especially dramatic in figures 14 and 15. Figure 14 shows the MPLM grapple fixture temperatures (FRGFs in fig.12). These fixtures are almost 180° apart, wth the grapple (GRAP) –Y PTM facng the sun. Ths PTM crcut remans off during the port maneuvers, while the GRAP +Y PTM cycles continuously, because this location is shaded. These effects are also illustrated in the aft cylinder and common berthing mechanism (CBM) temperature profiles as well (figs. 14 and 15). PTM4A PTM5A PTM6A 30 28 26 24 22 20 18 Temperature (°C) Orbiter APU Port APU Port Attitude Timeline: Sidewall Sidewall 16 Attiude Attiude 14 12 10 0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 MET from PTM Powerup (h) Figure 14. MPLM aft cylinder PTM temperatures. 20

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40 35 30 25 20 PTM13A PTM14A Orbiter APU Port APU Port Attitude Timeline: Sidewall Sidewall Attiude Attiude Temperature (°C)15 10 5 0 0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 MET from PTM Powerup (h) Fgure 15. MPLM CBM PTM temperatures. Finally, figure 16 illustrates the tight control response of the PTM system. The grapple fixture on/ off status is overlaid with the temperature data. These PTMs cycle within the desired temperature control range of 25.2 to 25.6 °C. GRAP( Y) GRAP(–Y) GRAP( Y) GRAP(–Y) 35 30 25 APU Port APU Port Orbiter Sidewall Sidewall Attitude Timeline: Attiude Attiude 20 15 Temperature (°C) 10 5 0 0 4 8 12 16 20 24 28 Temp On/Off Cycles 32 36 40 44 48 52 56 60 64 68 MET from PTM Powerup (h) Figure 16. MPLM grapple fixture PTM temperatures. 21

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1. FUTURE APPLICATIONS The results obtained from the first flight of the PTM shell heater system are very encouraging. Although the PTMs were developed specifically for the MPLM 28 V shell heater control system, the design is flexible and can be tailored to meet future customer needs. Below are just some of the customer-defined parameters that these designs can accommodate: • Mounting configurations • External temperature sensor RTD, thermal couple, thermstor, other temperature sensng devces • Heater current • Supply voltage • Range of temperature measurement and control. Following is a list of three disclosures of inventions (patents) that have been filed for these technologes: • MFS-32000-1 “Mnature Housng wth Standard Addressable Interface for Smart Sensors and Drive Electronics.” • MFS-32209-1 “Programmable Data Logger/Master Controller wth Multple Sensor/Devce Interface.” • MFS-31815 “Distributed Solid State Programmable Thermostat/Power Controller.” 22

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REFERENCES 1. Clark, D.W.; Seser, W.R.; and Reagan, S.E.: “MPLM Programmable Thermostat Development Plan,” ISS-MPLM-PLAN-017, Marshall Space Flight Center, AL, May 5, 2003. 2. Beverly, D.: “Radiation Test Report for the MPLM,” JSC-49624 Report, Johnson Space Center, Houston, TX, January 2003. 3. Brewster, S.: “Development Vibration Testing of the MPLM Programmable Thermostat,” Marshall Space Flight Center, AL, January 1, 2003. 4. Clark, D.W.; Seiser, W.R.; and Reagan, S.E.: “Programmable Thermostat Test Plan,” ISS-MPLM- PLAN-018, Marshall Space Flight Center, AL, May 2003. 5. Thomas, D.: “Qualification and Acceptance Environmental Test Requirements, International Space Station Program,” SSP-41172, Johnson Space Flight Center, Houston, TX, June 26, 2002. 6. Boeing North American, Inc.–Reusable Space Systems Division; “Space Shuttle Program-to-Space Station Program IDD,” NSTS-21000-IDD-ISS, Houston, TX, February 18, 1998. 7. Clark, D.W.; Seiser, W.R.; and Reagan, S.E.: “Programmable Thermostat End Item Specification,” MSFC-SPEC-3274, Marshall Space Flght Center, AL, Aprl 2004. 8. Clark, D.W.; Seiser, W.R.; and Reagan, S.E.: “Data Recorder End Item Specification,” MSFC- SPEC-3322, Marshall Space Flght Center, AL, Aprl 2004. 9. Trichilo, M.: “MPLM Thermal Analysis for STS-121 Mission, AL-TN-ALTEC-0016 Issue 2,” Turin, Italy, June 20, 2006. 10. Clark, D.W.; and Glasgow, S.: “STS-121 JOP PTM Setpoint Analysis Presentation,” MSFC Oral Presentation/Briefing, Marshall Space Flight Center, AL, May 13, 2005. 23

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Form Approved REPORT DOCUMENTATION PAGE OMB No. 0704-0188 Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operation and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503 1. AGENCY USE ONLY (Leave Blank) 2. REPORT DATE May 2007 4. TITLE AND SUBTITLE 3. REPORT TYPE AND DATES COVERED Techncal Memorandum 5. FUNDING NUMBERS Programmable Thermostat Module Upgrade for the Multpurpose Logstcs Module 6. AUTHORS D.W. Clark, S.D. Glasgow, S.E. Reagan, K.H. Presson, D.E. Howard, and D.A. Smth 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) George C. Marshall Space Flght Center Marshall Space Flght Center, AL 35812 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) Natonal Aeronautcs and Space Admnstraton Washngton, DC 20546–0001 11. SUPPLEMENTARY NOTES 8. PERFORMING ORGANIZATION REPORT NUMBER M–1186 10. SPONSORING/MONITORING AGENCY REPORT NUMBER NASA/TM—2007–214957 Prepared by the Project Engineering Branch, Engineering Directorate 12a. DISTRIBUTION/AVAILABILITY STATEMENT Unclassified-Unlimited Subject Category 18 Availability: NASA CASI 301–621–0390 13. ABSTRACT (Maximum 200 words) 12b. DISTRIBUTION CODE The STS-121/ULF 1.1 mission was the maiden flight of the programmable thermostat module (PTM) system used to control the 28 V shell heaters on the multi-purpose logistics module (MPLM). These PTMs, n conjuncton wth a data recorder module (DRM), provde contnuous closed loop temperature control and data recordng of MPLM on-orbt heater operatons. Ths Technical Memorandum discusses the hardware design, development, test, and verification (DDT&V) actvtes performed at the Marshall Space Flght Center as well as the operatonal mplementaton and msson performance. 14. SUBJECT TERMS programmable, thermostat, data, recorder, module 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION OF REPORT OF THIS PAGE Unclassified Unclassified NSN 7540-01-280-5500 24 15. NUMBER OF PAGES 32 16. PRICE CODE 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT OF ABSTRACT Unclassified Unlmted Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std. 239-18 298-102

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National Aeronautics and Space Administration IS20 George C. Marshall Space Flight Center Marshall Space Flight Center, Alabama 35812