-pefsf//bb52--tbi cassini rtg program cdrl transmitial/67531/metadc...-pefsf//bb52--tbi cassini...

-p*EfsF//BB52--TBi

Cassini RTG Program CDRL Transmitial TO: U.S. Department of Energy Lawrence Livermore Nat'l Lab 7000 East Ave., Bldg. 31 1 L-293 Attention: Ken Quitoriano

DISTRIBUTION: Symbol Copies

A 5 B 1 C 1 H 2 J 24 K 1

Cassini RTG Program In Reply Refer to: CON#2029 Contract NO: DE-AC03-91 SF1 8852 Date: 24 September 1997

CDRL Number: Reporting Requirement 4.F (Document No. RR16)

~ ~~

Title: Monthly Technical Progress Report (28 duly through 24 August 1997)

Approval Requirements:

Approval 0 None

Contract Period: 11 January 1991 through 30 April 1998

INTRODUCTION The technical progress achieved during the period 28 July through 24 August 1997 on Contract DE-AC03-91 SF1 8852 Radioisotope Thermoelectric Generators and Ancillary Activities is described herein. This report is organized by program task structure.

1 .X Spacecraft Integration and Liaison 2.X Engineering Support 3.X Safety 4.X Qualified Unicouple Production 5.X ETG Fabrication, Assembly, and Test 6.X Ground Support Equipment (GSE) 7.X RIG Shipping and Launch Support 8.X Designs, Reviews, and Mission Applications 9.X Project Management, Quality Assurance, Reliability, Contract Changes,

CAGO Acquisition (Operating Funds), and CAGO Maintenance and Repair H.X CAGO Acquisition (Capital Funds)

Note: Task H.X scope is included in SOW 1 Task 9.5. Task H. was created to manage CAGO acquired with capital equipment funding.

. ._ x- .

Lockheed Martin Missiles & Sp Room 1 OB50 Building B 720 Vandenberg Road King of Prussia, PA 19406 Space Power Programs

Internal Distribution: Technical Report List

Martha L. DeMedio

DISCLAIMER

Portions of this document may be illegible electronic image products. Images are produced from the best available original document.

,

Progress by Major Task

Monthly Technical Progress Report Lockheed Martin Document No. RR16

28 July through 24 August 1997

TASK 1 SPACECRAFT INTEGRATION AND LIAISON 0 ST/ During the RTG-to-Spacecraft fit check a plastic protective cover for a power cable connecter partially melted when the cover came in contact with the F-6 RTG (JPL Inspection Report No. 65695). A small amount of the melted polyethylene cap adhered to the generator surface. The melted cap was sent to Lockheed Martin, Valley Forge, for analysis and laboratory tests. Based on this investigation, it was concluded that the deposits were not a threat to the F-6 RTG, nor were they judged to be a threat to the spacecraft. However, to limit extraneous material from the RTG, Lockheed Martin recommended that the melted plastic be removed. Lockheed Martin personnel at the Kennedy Space Center were successful in removing the largest deposit. No further work is considered warranted and the JPL Inspection Report has been closed out.

TASK 2 ENGINEERING SUPPORT RTG Fuel Form, Fueling, and Tesf SupporVLiaison During this report period revisions to RTG Transportation System procedures proposed by Mound were reviewed and approved to support the return to Mound of the spare RTG which is in storage at the Kennedy Space Center.

Specificafions and Drawings Work is continuing to establish the new Configuration and Inventory Control System (CICS) database for drawings and specifications. This system will replace PIOS, the drawing control and configuration management system currently in use in Missiles and Space, Valley Forge Operations, for all future programs.

I

Monthly Technical Progress Report b

Lockheed Martin Document No. RR16 28 July through 24 August 1997

TASK 3 SAFETY ANALYSIS TASK The safety analysis task is comprised of four major activities: 1) Launch Accident Analysis, 2) Reentry Analysis, 3) Consequence and Risk Analysis, and 4) the Safety Test Program. Significant activities performed within each task during this period are detailed in the following subsections.

* I

During this reporting period, presentation charts and informal briefings were prepared for DOE in support of subsequent briefings to NASA’s Cassini Program Management Council (PMC), NASA Administrator, Dan Goldin, and OSTP Director, John Gibbons, as part of the launch approval process.

INSRP Activities The Cassini SER was received on 19 August and reviewed in comparison with the GPHS- RTG FSAR. While discrete risk values were not cited in the SER, health effects CCDFs for the mission are provided. The SER indicated that the FSAR upper risk curve envelopes, the INSRP upper risk curve, supporting NASA PMC briefing comments by INSRP coordinators that the SER and FSAR are “comparable.”

Launch Analyses The unit development folder (UDF), a software configuration management requirement, has been completed for the full stack intact impact (FSII) accident simulation code used to perform FSll analyses documented in the FSAR Addendum.

A PIR documenting the LASEP-T code revisions is underway. This consists of version 3.1, corresponding to the code utilized for the FSAR analyses, and version 4.0 used for the FSAR Addendum. The UDF for each of these versions is also being developed.

Reentry Analyses Role of the Surface Energy Balance; The surface energy balance (SEB) is the vital link between the flowfield environment and the thermal response of the GPHS aeroshell and the GIS cylinder. Temperature and ablation histories along a trajectory are computed using an in-depth, transient-heating code. Temperature and recession are driven by the heat flux reaching the surface. This heat flux, due to the chemically reacting, radiating, shock-layer gases, and the mass transfer of ablation products, is communicated to the

2



module through the SEB equation. The SEB equation expresses the conservation of energy at the surface boundary. The net heat flux to the solid surface results from summing gas-phase conduction, diffusion and radiation, and energy transfer due to mass removal, heterogeneous reactions, and re-radiation from the surface to the surrounding gas. The net heat flux and ablation rate are computed using a rigorous computational fluid dynamic (CFD) technique (the RACER code) coupled to a flowfield radiation code (LORAN-C).

Differences in SEB Formulations: As part of the development of a rigorous computational fluid dynamic (CFD) technique to compute the coupled flowfield/radiation about an ablating GPHS aeroshell, Lockheed Martin formulated a new form for the surface energy balance analyses (References 3-1 through 3-7). However, INSRP/RESP adheres to the conventional SEB so we have used both the conventional and the new Lockheed Martin SEB methods to compute ablation of the GPHS module and GIS cylinder for accidental reentry during the EGA maneuver. In general, the INSRP SEB results in more recession.

The SEB advocated by INSRP is the conventional model used for an ablating, chemically reacting surface and we believe this represents an upper bound for heating because of its treatment of the near-wall, gas-phase reactions. In the INSRP SEB approach, it is assumed that the heat released by these homogeneous reactions is totally transferred to the surface. Alternatively, in the Lockheed Martin SEB approach, it is assumed that this heat is transferred to the adjacent gas-phase and is indirectly passed to the surface by an increased convective and/or radiative heat flux. It is our view that, under high ablation conditions, the real scenario lies closer to the Lockheed Martin model.

Current analytical and computational techniques can not accurately predict the precise distribution of the heat released by these reactions. However, we believe that, with the high surface-ablation rates experienced by the GPHS and the GIs, the near-wall flameheaction zone will be pushed further and further into the surrounding gas phase and away from the ablating surface. Under such conditions, more of the enFrgy from the homogeneous reactions will be transferred to the surrounding gas phase. Thus, we conclude that use of the INSRP SEB results in an upper bound for recession, particularly for EGA reentry with high ablation rates.

3



Effect of SEB on GPHS and GIS Surwival/Failure Predictions: Because the mode of fqilure predicted for aeroshells during EGA reentry is structural (Le., high g-loads rising faster than material is ablating away), the effect of the INSRP SEB on aeroshell survivability predictions is slight; the aeroshell fails for all reentry angles steeper than --14" to -19" versus -16" to -21" with the Lockheed Martin SEB. From SPARRC consequence analyses, this would produce less than a 10% increase in mean health effects or EGA swingby risk and have no measurable effect on the probability of fuel release.

Recent analyses of the motion of the GIS (Reference 3-8), following aeroshell failure, show that the GIS will be oriented broad-side stable (the probability of a GIS end-on stable condition is only 0.2% if the GPHS is randomly tumbling and 0.1% if the GPHS is face-on stable) and spinning (the probability of spin rates below a thermal threshold of 0.2 rev/sec is only 2-3%). Rigorous CFD analyses of the GIs, oriented broad-side stable and non- winning, were performed using both SEB formulations. With the Lockheed Martin SEB neither burnthrough nor structural failures occur over the full range of potential reentry angles. Introduction of the INSRP SEB produces burnthrough for -20" (intermediate) reentries of the non-spinning, broad-side-stable GlSs, with survival predicted for the -90" trajectory. Using the INSRP SEB, burnthrough of non-spinning, broad-side stable GlSs is indicated over a range of -16 to -35" based on the ablation rates observed at the -20" and - 90". However, when the effects of spin are introduced (using rates from the motion studies) the broad-side stable GIS does not burn through over the complete range of reentry angles for both the Lockheed Martin and INSRP SEB formulations.

GIS Orientation during Heat Pulse Following Release from Failed Aeroshell: The probable orientation of the graphite impact shell (GIS) following release from a failed aeroshell has been assessed. This analysis is summarized in Cassini Memo No. 540 issued 10 September 1997. The analysis was performed using a full six degree-of-freedom (6DOF) Monte Carlo simulation with non-linear aerodynamics. Further, the initial dynamic conditions (angular rates and angles-of-attack) are based on the 6DOF module simulations performed by JHWAPL. It was found that the GIS stabilizes broadside well within the heat pulse for 99.8% to 99.9% of the all cases. The remaining 0.1% to 0.2% of cases stabilize end-on. Further the GIS is effectively spinning for 97% to 98% of the broadside cases.

These probabilities are summarized in the following table.

4



Orientation Probability (Release Probability (Release State from FOS Module) from Tumbling Module)

End-on 0.001 0.002

Broadside Non-Spinning 0.020 0.030

Broadside Spinning 0.978 0.968

GIs Reentry Thermal Analysis: Analyses for GIS release from a Non-FOS aeroshell were recently completed. The analyses used REKAP without CFD, and thus a surface energy balance (SEB) consistent with the INSRP RESP SEB. PIR U-Cassini-161 documents these results.

Analyses were performed for the steep (-90") and intermediate (-21") reentry angles with the GIS in the side-on stable and side-on spinning orientations. The later release time from a non-FOS aeroshell, as compared to release from a FOS aeroshell, led to the expected results of lower peak GIS temperatures and less recession. However, even for a spinning GIS with associated lower average heat fluxes, the iridium clad still reached the melt temperature. Thus, for all in-air GIS releases, regardless of aeroshell or subsequent GIS orientation, GIS survival is predicted, but portions of the clad will melt.

The results from the recent analyses are shown in Table 3-1, which also includes a summary of previously documented results for GIS release from a FOS aeroshell. Cases 3 and 4 when compared to cases 1 and 2, respectively, show the effect of later release times. Since the GIS is released near the time of peak heating in either case, the shortened time period spent in the heating pulse results in a substantial decrease in recession for Non-FOS releases. However, the peak GIS temperatures are still very high for the later release time, and conduction through the GIS causes the clad to melt.

5

Case #

1

2

3

4

5

6

GIS Orientation

Side-On Stable from FOS N S

Side-On Stable from FOS N S

Side-On Stable from ' NON-FOS N S

~ Side-On Stable from

Side-On Spinning from

NON-FOS N S

NON-FOS N S

I Side-On

, NON-FOS N S Spinning from

Reentry Angle

Release Peak Time GIS (4908"R) (Sec) Temp Q Time Clad Melt Recession

from A/S (OR) (Sec) Time (Sec) (In)

1.90 8506 2.71 2.46 .152

5.85 7882 7.65 6.55 .164

2.23 8503 2.63 2.75 .113

7.65 7435 7.95 8.35 .0645

2.23 8281 2.53 2.93 .033

7.65 5946 8.95 8.95 -023

- 90"

- 20"

- 90"

1 -21"

- 90"

- 21"



Table 3-1. Summary of GIS Thermal Analysis Results

The side-on spinning results are shown in cases 5 and 6. The spin rate was assumed to be fast enough that each surface location would receive the average of the fluxes from leading edge to trailing edge. The average radiation flux was assumed to be 24% of the stagnation point value and the cold wall convective heat flux coefficient was assumed to be 34% of the stagnation value. The effect of spinning can be seen by comparing case 5 and 6 to cases 3 and 4, respectively. There is a dramatic drop in recession due to the lower fluxes. However, the GIS temperatures are still high enough that conduction through the GIS causes the clad to melt.

Consequence and Risk Analysis Risk comparison CCDF plots for natural and man-made events were prepared for both the United States and the world. The U.S. comparisons were made based on phase 0 and phase 1 risks and the worldwide comparisons were based on phase 3 to 5 and EGA risks. Comparisons with nuclear power plant risks were also included. The U.S. comparison included 100 reactors and the worldwide comparison included 400 reactors as scaled from

f

6



U.S. reactor risk estimates. The expected risk from Cassini out-of-orbit and EGA accidents which might affect large portions of the world are 3 orders of magnitude lower that those estimated to be associated with nuclear power plants on a worldwide basis. A similar ratio applies to U.S. nuclear power plant risks and the Cassini launch related risks from Phase 0 and Phase 1 accidents. Figure 3-1 shows a comparison of the Cassini risk distribution to the worldwide natural and man-made risk distributions.

I 0 L

\ > cn S a, > W

c

- - - - -

- nat&rnan(w/oSassuQ- - natural . . . . . . . . . . . . . . . Cassini Phase.Z-&.-.- L manmade - - - - - - -

I .-_____ Cassini EGA _____..._ - \. < .

.L- L., .. ---_

\ - ._ -. '. '. !

- -

-.> 1. --\. 8. ''?.

! ? ! '.+ -

- -. !

! ! - ! ! !

-

! .-\

t l I ? 1 1 1 1 ' 1

- I

10-5 1 oo 1 o5 1 O'O

I Health Effects I Figure 3-1. Comparison of Cassini to Worldwide Natural and Man-Made Events

The source of the man-made and natural risk data shown in Figure 3-1 is NUREG/ CR-1916 with the exception of the automobile data for accidents with less than ten fatalities which is from the U.S. Department of Transportation National Highway Traffic Safety Administration 1996 database. The U.S. reactor data in CR-1916, as taken from WASH 1400, were scaled from 100 to 400 reactors by assuming the U.S. data applied to the worldwide plants and that the accident rate was proportional to the number of plants. The U.S. automobile data were scaled to the world by assuming that the ten fatality accident frequency data in CR-1916 ratio of 1.8 between the world and the U.S. accident rates was constant over the 1 to 9 fatality event range.

7



References 3-1. Bhutta, B. A., Daywitt, J. E., and Brant, D. N., “Interpretation of Enthalpies in the Energy

Balance of an Ablating Graphite Surface,” AeroTechnologies, Inc., Report AT-TN-96- 02,30 May 1996.

3-2. Bhutta, B. A., Daywitt, J. E., and Brant, D. N., ‘‘Comments on ‘Comparison of Alternative Mass and Energy Balance Methods at an Ablating Carbon Surface’,” AeroTechnologies, Inc., Report AT-TN-96-05, 31 July 1 996.

3-3. Bhutta, B. A., Daywitt, J. E., and Brant, D. N., “Energy Balance at an Ablating Carbon Surface with Discontinuously Changing Species Mass Fraction,” AeroTechnologies, Inc., Report AT-TN-96-06, 6 September 1996.

3-4. Bhutta, B. A., Daywitt, J. E., and Brant, D. N., “Energy Balance at an Ablating Carbon Surface with Discontinuously Changing Species Mass Fraction: Supplement I,” AeroTechnologies, Inc., Report AT-TN-96-07, 17 September 1996.

3-5. Bhutta, B. A., Daywitt, J. E., and Brant, D. N., untitled AeroTecnologies, Inc. Memo, 24 September 1996.

3-6. Bhutta, B. A., Daywitt, J. E., and Brant, D. N., “Supplement to Technical Note AT-TN-96- 05,” AeroTechnologies, Inc., Report AT-TN-96-05S, 13 December 1996.

3-7. Bhutta, B. A., “Energy Equation Applied to the Infinitesimal Homogeneous Reaction Zone at the Ablating Wall,” AeroTechnologies, Inc., Report AT-TN-97-02, 21 January 1997.

3-8. Letts, W. and Daywitt, J. E., “GIs Orientation During Heat Pulse Following Release from Failed Aeroshell, “ Lockheed Martin, Cassini Program Memo # 540, 15 August 1997.

8

Monthly Technical Progress Report Lockbeed Martin Document No. RR16


TASK 4 QUALIFIED UNICOUPLE FABRICATION The remaining efforts in Task 4 are associated with testing of 18 couple modules. Test temperatures and life test hours are shown in Table 4-1.

Table 4-1. Test Temperatures and Life Test Hours

Test Temperature Status as of Module I Unicouple Source 1 Hot Shoe I 24 August 1997

10,400 Hours Performance Normal I 1 135°C I Early Qualification Lot I I Test Terminated

October 1994 30,300 Hours I Performance Normal

1 135°C I Full Qualification Lot 18-11 I

26,389 Hours I Performance Normal I 1035"c Early Flight Production Lot

_____ ~ ~~

18 Couple Module Testing Two modules remain on life test. Testing of module 18-10 was terminated at the end of October 1994 after 10,400 hours.

Module 18-1 1 has accumulated an additional 676 life test hours during this reporting period and has reached 30,300 hours (3.46 years) of accelerated life testing. Its performance continues to provide added confidence that normal unicouple performance can be expected from the flight RTGs during the Cassini mission.

Module 18-12 has also accumulated an additional 676 life test hours and has reached 26,383 hours (3.01) years at design temperature levels and continues to show normal performance.

Module 18-1 1 (1 135°C) On 24 August 1997, the module reached 30,300 hours at the accelerated hot shoe temperature of 1135°C. Measured performance during this period continues to fall within the data base established by MHW and GPHS 18 couple modules.

9

Monthly Technical Progress Report Lockheed Martin Document No. R R l 6


The thermoelectric performance evaluation primarily studies the trends of the internal resistance and power factor. Figures 4-1 and 4-2 show these trends in comparison to module 18-8, the last module built during the GPHS program. Agreement is excellent and continues to provide a high degree of confidence that the GPHS unicouple manufacturing processes have been successfully replicated. The scatter in the data at the end of February (26,000 hours) was due to a faulty load transistor which has been replaced. Table 4-2 summarizes the initial and 30,300-hour performance data.

The isolation resistance trend between the thermoelectric circuit and the foil is shown in Figure 4-3 along with modules from the MHW and GPHS programs. The isolation resistance plateaued at about 1000 ohms between 6,000 and 7,000 hours. It then started a slow decrease and is presently at 324 ohms. A similar plateau and gradual decline were observed in MHW module SN-1. At the accelerated temperature of 1135°C the same amount of sublimation occurs in about 1,650 hours of testing as would occur in a 16-year Cassini mission.

Consequently, approximately 18.4 times as much sublimation has occurred during the test duration of module 18-11 as will occur during the Cassini mission. The module performance, therefore, confirms the adequacy of the silicon nitride coating on the qualification unicouples.

Individual Unicouple Performance: The performance of individual unicouples and rows of unicouples continues to be observed. Table 4-3 shows the room temperature resistance changes and the internal resistance changes observed during operation for each of the six rows and for individual unicouples in Rows 2 and 5. The unicouples continue to perform within a narrow band.

10



1.40

1.36

1.32

1.28

1.24

1.20

1.16

1.12

1.08

1.04

1 .oo

TIME, HOURS

Figure 4-1. Internal Resistance Ratio Versus Time (Modules 18-10, 18-1 1, GPHS Module 18-8) - 1 135°C Operation

1.02 9 , I S * - 1 , ~~1~ 8 8 7 a 1 8 , * , I * 9 8

1 .oo

0.98

0.96

0.94

0.92

0.90

0.88

0.86 GPHS MODULE 18-8 --o- CASSINI MODULE 18-10 n

0.84 __I d- CASSINI MODULE 18-11

0.82 ~ ' " ' ' ' ' ' ' ' ' ' 1 ' ' ' " ' ' ~ " ~ ' ' ' 1 ~ ~ "

0 5000 10000 15000 20000 25000 30000 35000

TIME, HOURS

Figure 4-2. Power Factor Ratio Versus Time (Modules 18-10, 18-1 1, GPHS Module 18-8) - 1135°C Operation

11



Table 4-2. Comparison of Initial and 30,300 Hour Performance of Module 18-1 1 at 11 35°C

~~

Heat Input, Watts

Hot Shoe, "C Average

Hot Shoe Range, "C

Cold Strap, "C Average (8 T/Cs)

Cold Strap Range (8T/Cs)

Cold Strap Average (1 2 T/Cs)

Cold Strap Range (12 T/Cs)

Load Voltage, Volts

Link Voltage, Volts

Current, Amps

Open Circuit Voltage, Volts

Normalized Open Circuits (8T/Cs)

Normalized Open Circuits (1 2 T/Cs)

Average Couple Seebeck Coefficient (1 2)

Internal Resistance, Ohms

Internal Resistance Per Couple (Avg.)

Power Measured, Watts (Load + Link)

Power Normalized, Watts (8 T/Cs)

Power Normalized, Watts (1 2 T/Cs)

Power Factor

Isolation

Circuit to Foil, Volts

Circuit to Foil, Ohms

initial 2/2/94

190

11 37.8

5.4

31 1.9

2.6

306.5

20.1

3.895

0.108

2.842

7.140

6.31 9

6.276

498 X

1.104

0.061 3

11.375

8.909

8.789

40.452 X l o 5

-1.68

6.29K

t = 52 Hours V L = 3.5v

2/4/94

192.9

11 37.5

5.2

31 4.3

2.5

308.9

20.3

3.499

0.121

3.174

7.160

6.359

6.31 6

501 X

1.115

0.0620

11.492

9.065

8.942

40.557 X

-1 -36

5.95K

t = 30,300 Hours

8/24/97

193.0

1 105.0

10.8

303.9

2.4

298.9

18.0

3.49

0.092

2.676

7.592

6.933

6.889

545.4 x 10-6

1.527

0.0848

9.41

7.85

7.75

35.2 x 10-5

-1.71

0.323K

12



100000

0)

0 E

10000

1000

d 0 2

100 100

A 18-10 Cassini v 18-11 Cassini 0 MHW SN-1

MHW SN-4 0 GPHS 18-5 . GPHS 18-6

GPHSl8-8 * GPHS18-W

I

1000

TIME, HOURS

10000 40000

Position

1 .o 2.0 3.0

4.0 5.0 6.0

7.0 8.0 9.0

10.0 11.0 12.0

13.0 14.0 15.0

16.0 17.0 18.0

Figure 4-3. Isolation Resistance - Module Circuit to Foil (Modules 18-1 0,18-11, GPHS Module 18-8) - 11 35°C Operation

Table 4-3. Module 18-1 1 Internal Resistance Changes

Serial # I =Bond I Preassy I 'Delta ri I T = 0 I T=1,509 Milliohm Milliohm Milliohm Milliohm Hours

WOO6 22.50 H0507 22.40 H0512 22.7

H0439 23.20 H0587 22.50 H0657 22.70

H0585 22.90 HO459 22.50 H0562 22.70

HM48 22.70 H0163 22.90 H0282 22.70

H0428 23.10 H0326 22.60 H0232 22.60

H0590 22.60 H0393 22.60 H0496 22.50

I

22.1 0 21.90 22.20

22.70 22.40 22.50

22.50 22.10 22.30

22.30 22.40 22.40

22.70 22.00 22.00

22.40 22.10 22.30

-0.40 -0.50 -0.50

-0.50 -0.1 0 -0.20

-0.40 -0.40 -0.40

-0.40 -0.50 -0.30

-0.40 -0.60 -0.60

-0.20 -0.50 -0.20

182.30 62.30 61 .OO 61.40 184.10

185.70

184.90 62.10 62.20 60.90 184.70

199.70 67.90 66.50 67.30 201.10

203.20

201.70 67.90 68.30 66.60 202.30

184.20 201.40

Delta ri Percent T=30,300 Milliohm increase Hours

17.40 9.54 251.60 5.60 8.99 85.90 5.50 9.02 82.00 5.90 9.61 83.40 17.00 9.23 250.50

17.50 9.42 264.00

16.80 9.09 252.60 5.80 9.34 84.60 6.10 9.81 86.90 5.70 9.36 89.1 0 17.60 9.53 260.10

17.20 9.34 250.10

Delta ri Percent Milliohm Increase

69.30 38.01 23.60 37.88 21.00 34.43 22.00 35.83 66.40 36.07

78.30 42.16

67.70 36.61 22.50 36.23 24.70 39.71 28.20 46.31 75.40 40.82

65.90 35.78

13



Module 18-1 2 (1 035°C Operation) The module reached 26,389 hours at the normal operating temperature of 1035°C on 24 August 1997. Thermoelectric performance, as measured by internal resistance and power factor trends, continues to be normal as shown as Figures 4-4 and 4-5, respectively. Table 4-4 shows initial performance and the performance on 24 August 1997.

Isolation Resis tance The isolation resistance between the circuit and foil continues to show the normal trend as shown in Figure 4-6.

Individual Unicouple Performance A review of the unicouple internal resistances and open circuit voltages indicates that all unicouples are exhibiting very similar behavior with time (See Table 4-5). The data for the six individually instrumented unicouples in Rows 2 and 5 are shown in Figure 4-7.

TIME, HOURS

I

Figure 4-4. Internal Resistance Ratio Versus Time (Modules 18-12, and 18-7) - 1035°C Operation

14



0.90 A

0.89-""""""""'""'"" 0 3000 6000 9000 12000 15000 18000 21000 24000 27000

TIME, HOURS

Figure 4-5. Power Factor Ratio Versus Time at Temperature (18-7 and 18-12) - 1035°C Operation

15



Table 4-4. Comparison of Initial and 26,389 Hour Performance of Module 18-12 at 1035°C

Heat Input, Watts

Hot Shoe, "C Average

Hot Shoe Range, OC

Cold Strap, "C Average (8 TICS)

Cold Strap Range (8T/Cs)

Cold Strap Average (1 2 T/Cs)

Cold Strap Range (1 2 T/Cs)

Load Voltage, Volts

Link Voltage, Volts

Current, Amps

Open Circuit Voltage, Volts

Normalized Open Circuit (8T/Cs)

Normalized Open Circuit (12 T/Cs)

Average Couple Seebeck Coefficient (1 2)

Internal Resistance, Ohms

Internal Resistance Per Couple (Avg.)

Power Measured, Watts (Load + Link)

Power Normalized, Watts (8 TICS)

Power Normalized, Watts (1 2 T/Cs)

Power Factor

Isolation

Circuit to Foil, Volts

Circuit to Foil, Ohms

Initial 611 6/94

169.15

1035.9

5.7

287.1

5.0

282.7

19.8

3.578

0.1 55

2.548

6.431

6.307

6.268

497 x 10-6

1.053

0.0588 ~

9.510

9.146

9.01 1

42.06 X

-1.71

21.3K

t = 26,389 Hours 8/24/97

169.1

1023

4.1

279.5

4.7

275.2

19.2

3.498

0.1 52

2.41 5

6.929

6.846

6.805

540.1 X

1.358

0.0754

8.82

8.61

8.48

38.67 X

-0.86

187K

16



1000000

03 E I 0

a 0 E

10000 100 1000 10000

TIME, HOURS

: 30000

Position Serial #

1.0 H2594 2.0 H2634 3.0 H2606

4.0 H2168 5.0 H2151 6.0 H2256

7.0 H2597 8.0 H2680 9.0 H2658

10.0 H1506 11.0 H1392 12.0 HI606

13.0 H1344 14.0 H1618 15.0 HI262

16.0 H1580 17.0 H2127 18.0 H2113

Figure 4-6. Isolation Resistance - Module Circuit to Foil (18-12, GPHS and MHW Modules) - (1035°C Operation)

Table 4-5. Module 18-12 Internal Resistance Changes

2nd Bond Milliohm

23.80 22.70 23.50

22.20 22.40 22.20

24.40 22.60 22.70

23.50 23.80 23.60

23.60 23.30 23.70

23.00 22.80 22.90

Preassy Milliohm

22.90 22.60 22.40

21.70 21.90 21.70

23.20 23.00 23.00

23.20 23.00 22.60

23.50 24.00 23.30

23.70 22.10 22.20

Delta ri Milliohrn

-0.90 -0.1 0 -1.10

-0.50 -0.50 -0.50

-1.20 0.40 0.30

-0.30 -0.80 -1 .oo

-0.1 0 0.70 -0.40

0.70 -0.70 -0.70

T=O T=1,505 Milliohm Hours

176.80 192.10 57.50 63.30 57.40 62.90 57.00 63.10 171.20 188.60

178.00 193.60

176.20 193.40 59.20 64.80 58.60 64.50 59.40 65.00 176.60 193.70

174.50 191.30

Delta ri Percent Milliohm Increase

15.30 8.65 5.80 10.09 5.50 9.58 6.10 10.70 17.40 10.16

15.60 8.76

17.20 9.76 5.60 9.46 5.90 10.07 5.60 9.43 17.10 9.68

16.80 9.63

T=26,389 Hours

224.20 74.80 73.80 74.80 222.60

225.70

226.70 75.80 75.90 76.10 227.20

224.60

47.40 26.81 17.30 30.09 16.40 28.57 17.80 31.23 51.40 30.02

47.70 26.80

50.50 28.66 16.60 28.04 17.30 29.52 16.70 28.11 50.60 28.65

50.10 28.71

17



80

78

- I I I I I I I I I 1 I I I

couple - -

i 56 58! i - 5 4 [ , ' 1 " " " 1 1 ' " 1 ' " 1 " " " " ~ ~ ' ' 1 ' ' ' 1 ' " 1 ~ ~ ~

0 2000 4000 6000 8000 10000120001400016000180002000022000240002600028000 TIME - HOURS

Figure 4-7. Individual Unicouple Internal Resistance Trends (Module 18-12)

18



TASK 5 ETG FABRICATION, ASSEMBLY, AND TEST Converter and Spare Hardware All effort has been completed on this task.

TASK 6 GROUND SUPPORT EQUIPMENT (GSE) GSE Hardware All effort has been completed on this task.

TASK 7 RTG SHIPPING AND LAUNCH SUPPORT Launch Support Aciiviiies During this reporting period the RTGs remained in storage in the RTGF. The PTU electrical performance testing and pressure measurements of the RTGs were performed. All electrical data were consistent with previous measurements. The pressure checks showed that the pressure on all four RTGs had increased during the latest storage period. During 26 days of storage F-2 increased .30 psi, F-5 increased 50 psi, F-6 increased .13 psi and F-7 increased .16 psi. Based on this data no additional pressure measurements are planned until the xenon gas exchange cycles scheduled for the week of 29 September.

The electrical connector cap material was removed on F-6. The major deposit was determined to be a "bubble" and very little material remained. The removed material was collected and returned to Valley Forge. A small amount of paint was removed at the edge of the land near the sealing screw. Some of the smaller deposits were not removed. A JPL Quality Engineer witnessed the removal operation and concurred with this disposition. Photos were taken of this reworked area.

The procedure for RTG transfer and staging for SLC-40 installation and contingency removal was reviewed. All issues were resolved and the procedure is ready for release.

19



A test was performed to determine the heat-up rate of the outboard handling fixture when placed on the heater plates. The heating of the outboard handling fixtures is required if the RTGs need to be removed from the spacecraft at SLC-40. Three heater plates will be used and a heat-up time-temperature profile has been established.

The hurricane plan for KSC/CCAS was reviewed and signed off. If the RTGs are in the RTGF, they will be placed on a flatbed trailer. If the RTGs are on the spacecraft and a hurricane warning is issued, the RTGs will be removed and placed in their BPCAs on level 6 of SLC-40.

A summary of the RTG electrical data and the pressure history at KSC and Mound are shown in Tables 7-1 through 7-4.

20



Table 7-1. RTG F-2 Data

Y

RTG RTG RTG Case Case RTD RTD RTD RTD RTD RTG RTG Case RTG shorted shorted Open Cir Open Cir CloseCir # I # 2 # 3 # 4 Avg RTG internal load res

pressure voltage current voltage voltage voltage temp temp temp temp temp power res res 2 min. Date PSlA VDC Amps VDC VDC VDC Deg.C Deg.C Deg.C Deg.C Deg.C Watts Ohms Ohms KOhms

4/2/97 1.281 15.10 35.21 0.343 0.017 161.7 162.7 164.4 161.1 162.5 19.3 2.247 0.085 191.2 4/2/97 1.269 15.29 35.88 0.666 0.046 164.4 165.3 166.2 163.8 164.9 19.4 2.264 0.083 134.8

4/14/97 24.60 1.271 14.91 34.99 0.348 0.019 166.2 167.1 165.3 166.5 166.3 19.0 2.262 0.085 177.8 AI14197 23.65 1.271 14.91 34.99 0.348 0.019 166.2 167.1 165.3 166.5 166.3 19.0 2.262 0.085 177.8 KSC 4/24/97 23.60 1.261 14.92 34.83 0.307 0.017 165.7 165.8 165.9 165.8 165.8 18.8 2.250. 0.085 170.0 4/24/97 24.50 5/13/97 24.67 5/23/97 note 1. 1.137 16.04 38.59 0.406 0.037 NA 169.7 167.7 166.6 168.0 18.24 2.335 0.071 99.7 6/2/97 note 2. 1.066 14.72 34.59 0.377 0.018 NA 163.7 160.8 162.4 162.3 15.69 2.277 0.072 199.4 6/3/97 24.79

~- MOUND

RTG in NORMAL LOAD mode 6/20/971 24.901 30.06) 5.211 42.141 20.351 5.6Ol NA I 159.31 157.11 158.21 158.21 156.611 2.3191 5.7701 263.4

Notes: 1 2

Data taken after extended period in OPEN mode, during adapter installation. Conditions were unstable. Stable data taken after JPL adapter was installed.




RTG F6 DATA

RTG RTG RTG Case Case RTD RTD RTD RTD RTD RTG RTG Case RTG shorted shorted OpenCir OpenCir CloseCir # I # 2 # 3 # 4 Avg RTG internal load res

res 2 min. Date PSlA VDC Amps VDC VDC VDC Deg.C Deg.C Deg.C Deg.C Deg.C Watts Ohms Ohms KOhms

MOUND 4/16/97 24.50 1.287 15.72 35.63 0.328 0.011 167.7 170.0 169.2 168.4 168.8 20.23 2.185 0.082 288.2~ 4/16/97 25.20 1.287 15.72 35.63 0.328 0.011 167.7 170.0 169.2 168.4 168.8 20.23 2.185 0.082 288.2 4/28/97 22.10 1.297 15.71 I 35.67 0.343 0.011 161.5 158.5 160.3 161.3 160.4 20.38 2.188 0.083 301.8 4/28/97 23.60 1,297 15.71 35.67 0.343 0.011 161.5 158.5 165.3 161.3 160.4 20.38 2.188 0.083 301.8 KSC

pressure voltage current voltage voltage voltage temp temp temp temp temp power res

5/29/97 note 1. g.12 17.35 40.33 0.493 0.043 NA 178.8 177.7 178.3 178.3 19.43 2.260 0.065 104.7 6/2/97 note 2. 1.049 15.53 35.00 0.412 0.014 NA 168.3 167 168.7 168.0 16.29 2.186 0.068 284.3 6/4/97 24.32 6/4/97 24.97

RTG in NORMAL LOAD mode 6/18/97( 25.041 30.00(- 5.001 41.241 27.851 12.441 NA I 162.7) 162.51 162.61 162.61 150.031 2.2481 5.9991 123.9

I

7/25/97 25.12 1.036 15.48 35.5 0.5302 0.0244 NA 165.9 165.9 165.9 165.9 16.04 2.226 0.067 207.3 811 197 NA 167.0 166.0 167.0 166.7 8/4/97 NA 167.0 167.0 168.0 167.3

811 1/97 NA 166.0 166.0 167.0 166.3 811 9/97 1.023 15.26 35.5 0.5417 0.02431 NA 163.1 163.5 165 163.9 15.61 2.259 0.067 212.8 8/20/97 25 25 8/20/97 24.94

0.0 0.00 #DIV/OI #DIV/OI #DIV/OI

Notes: 1 2


Monthly Technical Progress Report Lockheed Martin Document No. RRI6



h) P

5120197 note 1. 1.259 16.83 39.88 0.599 0.042 NA 171.9 171.8 173.2 172.3 21.19 2.295 0.075 132.6 5130197 note 1. 1.251 17.12 40.53 0.584 0.048 NA 173.3 174.4 173.8 173.8 21.42 2.294 0.073 111.7 6/2/97 note 2. 1.122 15.29 34.96 0.473 0.012 NA 164.7 165.7 164.5 165.0 17.16 2.213 0.073 384.2 6/4/97 24.40 6/4/97 24.99 I

. . RTG in NORMAL LOAD mode 6/20/971 I 24.801 30.031 5.241 41.971 27.641 11.051 NA I 161.71 160.41 1591 160.31 157.361 2.2791 5.7311 150.1

~ ~ ~

7/25/97 24.80 7/25/97 25.00 1.151 15.7 36.14 0.522 0.0223 NA 157.0 159.2 154.0 156.7 18.07 2.229 0.073 224.1 7/25/97 NA 157.0 161.0 157.0 158.3 8/1/97 NA 163.0 163.0 161.0 162.3 8/4/97 NA 163.0 163.5 161.0 162.5

811 1/97 NA 163.0 163.0 161.0 162.3 811 9/97 1.220 15.33 36.08 0.5138 0.02127 NA 159.3 161.9 161.2 160.8 18.70 2.274 0.080 231.6 8/20/97 25.16

-

Notes: 1 2


TASK 8 DESIG

Monthly Technical Progress Report Lockheed Martin Document No. RRI 6


4S, REVIEWS, AND MISSION APPLICATIONS 8.1 Galileo/Ulysses Flight Performance Analysis No significant activity this reporting period.

8.2 This task has been successfully completed.

Individual and Module Multicouple Testing

8.3 Structural Characterization of Candidate Improved N- and P-Type SiGe Thermoelectric Materials

This task has been successfully completed.

8.4 Technical Conference Support The technical paper titled “Cassini RIG Acceptance Test Results and RTG Performance on Galileo and Ulysses” was presented at the IECEC.

8.5 Evaluation of an Improved Performance Unicouple

Module 18-2 This task has been successfully completed.

8.6 Solid Rivet Feasibility Study This task has been successfully completed.

8.7 Computational Fluid Dynamics (CFD) This task has been successfully completed.

8.8 Technical International Conference Support This task has been successfully completed.

8.9 Additional Safety Tasks This task has been successfully completed.

8.1 0 Small RTG Design Study This task has been successfully completed.

25

. Monthly Technical Progress Repopt

Lockheed Martin Document No. RR16 28 July through 24 August 1997 b

8.1 1 FSAR Support Studies of the adequacy of sampling were completed for consequence calculations for out- of-orbit reentry and reentry from Earth Gravity Assist. Recommendations were made on improvements to the sampling procedures for future risk analyses.

8.12 Scale Model GPHS-RTG This task has been successfully completed.

8.13 AMTEC RPS Program Plan Working in conjunction with DOE Germantown, DOE Oakland, and NASA staff, Lockheed Martin and AMPS restructured the AMTEC Radioisotope Power System (RPS) Program Plan, adjusting scope and schedule to meet stringent annual and total funding constraints. DOE authorization was received to proceed with the detailed cost estimate and technical documentation.

26



TASK 9 PROJECT MANAGEMENT, QUALITY ASSURANCE, AND

9.1 Project Management All weekly and monthly contractual reports were delivered on schedule.

R ELI AB I LlTY

Launch support operations are continuing. RTG transfer procedures are being reviewed and finalized. RTG performance continues to be nominal.

A draft of the Safety Evaluation Report (SER) was received from INSRP. The SER indicates that INSRP results are “enveloped” by the FSAR.

Lockheed Martin attended the Cassini Program Management Council Meeting at NASA Headquarters, Washington, DC, on 5 August. A technical paper on Cassini RTG performance was presented at the IECEC Conference during the week of 28 July.

The performance of 18 couple modules 18-1 1 and 18-12 continue to closely track the reference performance as represented by modules from the Galileo/Ulysses program. Module testing will be terminated next month, in preparation for the move of Space Power from Building B to Building 100.

Attached is the Cassini RTG calendar showing 3Q97 program meetings and important related events.

No significant environmental, health, or safety incidents occurred during this period.

9.2 Quality Assurance Quality Plans and Documents No plans were initiated or modified during this period.

Process Readiness and Production Readiness Reviews No readiness reviews were conducted this month.

Quality Control in Support of Fabrication There was no significant activity in the Quality Control area during this period.

Material Re view Board There were no Class I (major) nonconformances generated this reporting period.

27



Qualify Assurance Audits There was no activity in this area during this reporting period.

Qualify Assurance Stafus Meefing There were no meetings held during this period.

TASK H CONTRACTOR ACQUIRED GOVERNMENT OWNED (CAGO)

H.l CAGO Unicouple Equipment No significant activity during this reporting period.

PROPERTY ACQUISITION

H.2 CAGO - ETG Equipment No significant activity during this reporting period.

H.3 CAGO - MIS No significant activity during this reporting period.

DISCLAIMER

This report was prepared as an amount of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsi- bility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Refer- ence herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, rccom- mendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

28

? Cassini RTG Program Calendar As of 23 September ., 997

29

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