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Programmable Thermostats for MPLM ShellHeater Control ULF1.1 Thermal Performances

ABSTRACT

The Multi-Purpose Logistics Module (MPLM) is the primary carrier for "pressurized" logistics toand from the International Space Station (ISS). The MPLM is transported in the payload bay ofthe Space Shuttle and is docked to the ISS for unloading, and reloading, of contents within theISS shirt sleeve environment. Foil heaters, controlled originally with bi-metallic thermostats, aredistributed across the outside of the MPLM structure and are utilized to provide energy to thestructure to avoid exposure to cold temperatures and prevent condensation.

The existing bi-metallic, fixed temperature set point thermostats have been replaced withProgrammable Thermostats Modules (PTMs) in the Passive Thermal Control Subsystem (PTCS)28Vdc shell heater circuits. The goal of using the PTM thermostat is to improve operationalefficiency of the MPLM on-orbit shell heaters by providing better shell temperature control viafeedback control capability. Each heater circuit contains a programmable thermostat connected toan external temperature sensor, a Resistive Temperature Device (RTD),, which is used to providecontinuous temperature 'monitoring capability. Each thermostat has programmable temperatureset points and control spans. The data acquisition system uses a standard RS-485 serialinterface communications cable to provide digital control capability.

The PTM system was designed by MSFC, relying upon ALTEC support for their integration withinthe MPLM system design, while KSC performed the installation and ground checkout testing ofthe thermostat and RS-485 communication cable on the MPLM FM1 flight module. The PTMswere used for the first time during the STS-121/ULF1.1 mission.

This paper will describe the design, development and verification of the PTM system, as well asthe PTM flight performance and comparisons with SINDA thermal model predictions.

https://ntrs.nasa.gov/search.jsp?R=20090033636 2018-05-10T09:09:27+00:00Z

MS c L oo-- f^^ S-CA y +^

Programmable Thermostats forMPLM Shell Heater Control - ULFlol

Thermal Performances

Shaun Glasgow/ NASA MSFCDallas Clark/NASA MSFCMichele Trichilo/ALTEC

4,0

L T E CThe Italian Gateway to ISS

Outline

n Background

n Hardware Development

n STS-121 Mission Operations

n Flight Performance

(D 2007-01-3028

Background

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S102ES095 201.703.110085945

MPLM Description

• Size:• Dry Weight:• Cargo Capacity:• Flight History:

21' long X 15' diameter9800 Ibm20000 Ibm7 ISS missions

MULTI-PURPOSE LOGISTICS MODULE (MPLM) - The MPLM is apressurized module used to transport cargo to/from the InternationalSpace Station (ISS). The Italian Space Agency (ASI)-built MPLM servesas the ISS "moving van", carrying laboratory racks filled with equipment,experiments, and supplies. The MPLM is transported in the Space Shuttlecargo bay and then docked to the ISS for cargo transfer. It can transportup to 16 racks with a maximum payload weight of 20,000 lbs (9,072 kg)in a controlled (human-rated) operating environment.

ALTEC (the Italian Space Agency MPLM sustaining engineering partner)and the Marshall Space Flight Center are responsible for the sustainingengineering activities associated with the MPLM, including support to(D Cargo Element Integration for each flight and real-time mission support.

2007-01-3028

MPLM Shell Heater SystemFwC CONEF-HOT-4t0UGH5

----------------------- ------ -------- ---------- ---tJOT PC—T tt ^

AwG 20 ^^ 28 VOCO Or-^

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AA__ i i -_- I I Yy^!' I -W, I I ti 1

I MTRT I I MTRB i I HTA9 1' I HTRII t ^I T I I I 1 I I r

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MPLM Shell Heater System: •------------------ ---------- ------------------------------

n 2 separate circuits: 28V (STS mode) & 120V (ISS mode) Forward Cylinder Electrical Schematic

• 22 fused branches / 66 Kapton strip heater pads

Purpose:• Moisture/condensation prevention• Cargo temperature conditioning (50-90F)• Regulate internal pressure (13.9 -15.2 psi)

2007-01-3028

Issues w/ BimMetalfic Thermostatsn Setpoints were set too high (81 to 95°F) for nominal mission timeline

heater operationsPositive Pressure Relief Assembly (PPRAs) actuation would occur at these temperatures

PPRA actuation exposes a risk of a valve not resenting and resultant venting of theMPLM environment

Loss of MPLM environment prevents ingress/cargo transfer and loss of mission

n Operational workarounds required for heaters ops w/ bi-metallicthermostats

Heaters manually cycled by crew from aft flight deck switch panel

Mission-dependent profile required for shell heater ops

Preflight analyses define approx. heater cycle times and generate trend data

Real-time telemetry required to "fine-tune" and optimize heater operations

Real-time MOD support to coordinate crew activity

n Unnecessary usage of Orbiter cryogenic resources (for powergeneration)

(i) 2007-01-3028

Project Authorization

ISS Program Office formally approved CR3578 in October2000 for developing solid-state Programmable Thermostatsto replace the 28V bi-metallic units

Operational Goals:

• Provide temperature control w/ closed loop feedback• Reduce mission operational impacts &crew interaction• Improve Shuttle cryogenic fuel cell efficiency

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Hardware Development

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Project Deliverables

100 Programmable Thermostat Modules (PTMs)

n 6 Data Recorder Modules (DRMs)

GSE Laptop computer & Thermoview software

n RS-485 Serial Communications Cable

n PTM Installation & Cable Layout Drawings

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Roles &Responsibilitiesn PTM & DRM designed, manufactured, and certified by

MSFC

n GSE software designed and certified by MSFC

n RS-485 communications flight cable designed,manufactured, and certified by Boeing

n Hardware installation, cable routing layout, and MPLMelectrical power harness wiring drawings provided byALTEC

n Installation/

(Dand ALTECsystem checkout testing performed by Boeing

2007-01-3028

Programmable ThermostatDesign Features:

+28 V EXISTING EXISTING

• Size: 2.25" x 1.75" x 0.5 FUSE THERMOSTAT SHELL HEATER

• Weight: < 75 gm (w/o carrier); < 100 gm 412B V RTN

(w/carrier)MODULE TO CARRIERMOUNTING SCREWS

• C&DH: RS-485 serial communication protocolRTD SENSOR

• Software: Graphical Users Interface (GUI)developed for programming and monitoring

COMMUNICATIONS ^^ PROGRAMMABLE• Input Power: +9 to +28 VDC. CONNECT i THERMOSTAT

MODULEI I

I

• External RTD temperature sensorTHERMALPAD

• External Heater : Up to 5A at +28VDC ^il. CARRIER

• Programmable temperature set points and span. EPDXYSetpoint/ span resolution: 0.1 OC

• Data Recorder Module (DRM) available in the MPLM PROGRAMMABLE THERMOSTAT HARDWARE

same housing for recording status and temperaturedata for up to 32 PTM units connected on a singleRS-485 bus.

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Extensive prototype development testing performed (1 PTM & DRM)• Thermal Cycling/Random Vibration/EMI/EMC• Adhesive bond strength (RTV bonding process validation)• Radiation susceptibility (Radiation-hardened EEE parts waiver)

Lot qualification (10 PTMs & 1DRM) FAcceptance tests (90 PTMs & 5DRMs)

Is0

0

No test failures!

2007-01-3028(D Qualification Test Fixture

PTM18A on MPLM FM1

Flight Certification Process• Environmental Qualification/Acceptance testing conducted per SSP-41172 ISS test

guidelines• Thermostat hardware certified for 25 missions

Continuity/Functional

ThermalVacuum

Continuity/Functional

Qualification Test Flow

StructuralVibration

Continuity/ EMI/EMCFunctional

Continuity/Functional

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Acceptance Test Flow

Module Continuity/ Structuralburn-in Functional Vibration

Continuity/ Thermal Continuity/Functional Vacuum Functional

C) 2007-01-3028

Thermal Cycle Ranges

Low Temperature High Temperature # of Cycles

Qualification -240F +1560F 24

Acceptance -40F +1360F 8

Environmental Test LevelsRandom Vibration Levels

AcceptanceFrequency (Hz) Qualificatio Level

n Level

20 0.04 g 2 /Hz 0.01g2/Hz

20 to 65+7.6 +7.6

dB/Octave dB/Octave

65 to 180 0.8 g 2 /Hz 0.2g2/Hz

180 to 360 -7.0 dB/Octave7.0

dB/Octave

360 0.16 g 2 /Hz 0.04 g2/Hz

360 to 1400 -2.6 dB/Octave2.6

d B/Octave

1400 0.05 g 2 /Hz 0.0125 g2/Hz

1400 to 2000 - 4.9dB/Octave

-4.9dB/Octave

2000 0.028 g 2 /Hz 0.007 g2/Hz

Composite 16.8 g rms 8.4 firms

(DQualification Duration = 810s in each of 3 mutually perpendicular axesAcceptance Duration = 60s in each of 3 mutually perpendicular axes. 2007-01-3028

STS-121 Mission Operations

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Mission Highlights

• STS-121/ULF1.1 mission launched July 4, 2006• 14 day mission duration• 7t" MPLM mission; 1 St flight of new PTM system• MPLM heater ops during downhill mission phase (FD10-13)• MPLM daily pressure checks performed for monitoring• 1St MPLM mission in which shell temperatures recorded during

flight operations

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Mission Phase Cabin Environment

Flight Phase Cabin P Lower Limit Action RequirementLimits Point

Prior to Transfer to Accounts for MPLM spec, lower limit

ISS (28V Heaters)10 °C (50°F) and PPRA

773.1 mmHg 14.95psiaTransfer to ISS -

Accounts for transfer cool down &

includes vestibule(a) > 18.3°C (65°F) protects against

outfitting (No Heaters)(b) > 12.8°C (55°F) (a) condensation

(b) MPLM spec. lower limit

Ingress (120V MPLM Activation complete w/MPLM ISS

Heaters) AN/A 15.6°C 60°F ) Shell heaters operational

Accounts for transfer cool down &Transfer to PLB (No (a) > 18.3°C (65F) protects againstHeaters) (b) > 12.8°C ( 55°F) (a) condensation

773.1 mmHg 14.95 (b) MPLM spec. lower limit

psia Accounts for transfer cool down &Return to Ground (28V (a) > 15.6°C (60°F) protects againstHeaters) (b) > 10°C (50°F) (a) condensation

(b) MPLM spec. lower limit

De-orbiting (a) >15.6 0C (60°F) To avoid atmosphere entering and

Landing Pground - DPNPRV (b) > 10°C (50°F) contaminating MPLM

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Mission Setpoint Analysis

• Mission setpoints are loaded during KSC ground processing

• PTM setpoint optimized to maintain MPLM cabin air environment withinpressure range to avoid:

PPRA actuation (on-orbit)NPRV actuation (re-entry)Condensation

. MPLM heater usage remain within allocated STS-121 Shuttle power budget

Relief Valve analysis constraints:95% KSC landing site max pressure variationsNPRV cracking pressure limitPPRV cracking pressure limit

. Final heater control parameters: SP= 25.6 C; Error span= +/- 0.2 C

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MPLM Pressure Relief Valve ChartSTS-121 MPLM/ ISS Closeout Conditions

78F Setpoint, +/- 0.4 F Control Band

90.00

85.00

NPRV crack limit

80.00camCL

Emw 75.00 —oISS Nominal [T,P] Range..,:*:,:072-74F @ 14.65-14.75psi PPRA crack limitU

MPLM Max. Dewpoint Limit

60.0014.5 14.55 14.6 14.65 14.7 14.75 14.8 14.85 14.9 14.95

P1, MPLM Closeout Pressure (psia)

MPLM/ISS Closeout Conditions 2007-01-3028

ALTEC Thermal Verification ResultsHeaters Dissipation

MPLM ULF1.1 Mission - Beta -2 -ZLV -XVV

30000

25000

c^20000

15000a^

= 10000w

5000

0235 245 255 265 275 285 295 305

Time [h]

(D MPLM Pre-mission Thermal Verification Analysis

2007-01-3028

0.0 (14 .51)

102.0(14.80)

102.5(14.87)

15/20:3

16/11:5

17/09:4

MPLM Cabin Air Pressures

Cabin Temp Cabin Press1 Act (GMT) °C kPa (psi)

> 15.6 °C < 103 kPa

(D

Notes

Environment Check (CFARunning)

Pressure Check (w/oCFA)

Pressure Check (w/oCFA)

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Flight Performance

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Shell Heater Summary0 Heater on-time: 60.83 hr

• DRM successfully captured all 20 PTM data channels

0 Data acquisition rate: 1/min; 3647 total samples

• Heater Duty Cycle: 0.387 (on/off cycle counts)

• Heater Power consumption: 23.35 kWH

C) 2007-01-3028

1000

900

800

700

600

m0 500a

0400

300

200

100

0

0.00 4.00 8.00 12.00 16.00 20.00 24.00 28.00 32.00 36.00 40.00 44.00 48.00 52.00 56.00 60.00

MET from PTM Powerup (Hrs)

—TOT PWR

Shell Heater Power ProfileSTS-121 Heater Power Profile

0 Heater Duty Cycle = 38%2007-01-3028

20

15Y_

T

dcW

0 10

5

0

0.00 4.00 8.00 12.00 16.00 20.00 24.00 28.00 32.00 36.00 40.00 44.00 48.00 52.00 56.00 60.00

MET from PTM Powerup (Hrs)

25

— Energy (kWh)

STS-121 Shell Heater PowerSTS-121 Energy Profile

0 23 kwH (actual) vs 30kwH (planned) 2007-01-3028

1 154 307 460 613 766 919 10721225137815311684183719902143229624492602275529083061321433673520

(DNo of Samples

2007-01-3028

30

28

26

24

m 22m

d20M

dCL

E 18H

16

14

12

10

mperature

1

1

1

1

1

1

3tat On/OffStatus

Forward Endcone PTMsFCON PTMs

25

ULA

20

N!

RQ 15Em

Grapple Fixture PTMsGrapple Fixture (+Y/-Y) PTMs

35

30

10

5

0

-Y Port, Sun +Y Stbd, shade

OrbiterSidewall —I

I Sidewall

U

_UAttitude Timeline

ULUULILF ll ^U _JLJ LJI^LJ I1 UL- __

Temperature Control Range: 25.4 - 25.8 C

+Y Stbd

0.0 4.0 8.0 12.0 16.0 20.0 24.0 28.0 32.0 36.0 40.0 44.0 48.0 52.0 56.0 60.0 64.0

MET from PTM on (Hrs)

Illustration of Shuttle flight attitude heating influencf- 07-01-3028s0

Common Berthing Mechanism PTMsCBM PTMs

40

0

35

30

& 25rn

20

E15

10

5

0

0.0 4.0 8.0 12.0 16.0 20.0 24.0 28.0 32.0 36.0 40.0 44.0 48.0 52.0 56.0 60.0

MET from PTM Powerup (Hrs)

2007-01-3028

30

28

26

Lj 24

22

20+r

LCL 18Ea)

14

12

10

^„`^`a`d•^i 13.^'^-.^^ `. - .r—` r^ tr ,rs' +—^ f ^,..^^.°_a^— ^^ _"fit

On/Off Cycle status

^ IU U ... _.

U) OIT- coO M CD O N U) W = d" 1- O M O O N U) M = ;I 1` OCO C^ - f— N f— M M M O ;T O ;;r O U) O M = 0 N

CO I^ O O N M U7 O M O = N 1;T M I- O O N M LO^ T- T- ^ = = ^ N N N N N N co M M M

— PTM7A— PTM8A

PTM9A

PTM10A

— PTM7A

PTM8A

PTM9A

PTM10A

Aft Endcone PTMsACON PTMs

(D No. of Samples

2007-01-3028

On/Off Cycle status

30

28

26

—24

22a^L

20La 18EaD^— 16

- PTM 17A

- PTM 18A

- PTM17A

PTM18A

Stabilizer & Main Fitting PTMsStabilizer & Main Fitting PTMs

14

12

10^- q r- O CO (D O N LO 00 = Iq ti O M (D M N LO 00 ^ 143- rl- O

LO O (D = 0 = r` N r- M M CO O ;T M Iq O LO O (D - 0 NM IT M ti O O N M LO (D 00 O N d (O ti O O N M LO^- r- T- ^ = = N N N N N N CO CO CO CO

No. of samples 2007-01 -3028

35

33

31

29

U27

a^L25L

Q.

23

21

19

17

15

SINDA

—MIDFWD CYL9425

— PTM2-PTM1A rci

PTM

ALTEC Thermal Model ResultsFCYL1 _PTM 2(PTM 1 A)_CO425

230 240 250 260 270 280

290 300 310

Time [h]

IDPTM2 vs SINDA model

Forward Cylinder2007-01-3028

35

33

31

29

U27

aL̂

L 25CL

E 23

21

19

17

15

SIN

PTM22- FWD CONE 9218- PTM23-PTM22A K

ALTEC Thermal Model ResultsFCON4_PTM23(PTM22A)_CO218

230 240 250 260 270 280 290 300 310

Time [h]

PTM22 vs SINDA model2007-01-3028

Forward Endcone

Conclusions• Programmable Thermostats performed as designed

• Data acquisition functioned properly

• MPLM shell temperatures controlled within desiredcontrol range.

PTM temperatures will be used to refine ALTECSINDA thermal model for future missions

(D 2007-01-3028