U.S. DEPARTMENT OF

ENERGY Nuclear Energy

National Aeronautics and Space Administration

ADVANCED STIRLING RADIOISOTOPE GENERATOR INTEGRATED FEDERAL PROJECT

Advanced Stirling Radioisotope Generator: Teamwork and System Reliability

Chris Steffen, Jr.

1-May-2013

Government & Contractor Partnership

Advanced Stirling Radioisotope Generator (ASRG)

AC Power DC Power from ASCs Connector ~--~t.~~ 7li::;;.,~,..,......_~

to SV

ASC Controller

Unit (ACU)

Fins Advanced Stirling

Convertor (ASC) (2)

3

Cold-Side Adapter Flange

(CSAF) (2)

Shunt Dissipater

Unit (SOU)

GPHS (2)

ASRG Project Key Deliverables

Qualification Test Unit

Fueled & Tested 2016

Flight #1 Unit

shipped for Fueling

& Testing 2016

Flight #2 Unit

shipped for Fueling

& Testing 2017

ASRG Mass Metric- March 2013

45

40 RPS PO Reserve

--;:o 35 .::t:. -

--,. - I

Jan-08 Jan-09 Jan-10 Jan-11 Ja n-12 Jan-13 Jan-14 Jan-15

5

150 -

145

-! 140

\.,.

<1> ~ 0

Q,.

E 135 Q) ... ~

> V'l

G) ... ~ 130 a. E 0 u

~ 125 V) <{

120

115

ASRG Power Metric- March 2013

CBE Power

••••••••••• Output Power Req (Original) = 140 W • •••• ••••••••••••• •

•••••• •

New Monte Carlo Estimate: Cumulative Probab ility of Achieving 130.0 W = 99%

CBE Power = 140.8 W

Cont ingency

Predrcted Power (Worst Case) .... ••••••••

Worst Case Power loss I ~'Total Power Margin = 3.99%

Predicted Power(RSS) = 10.00~ ..~~T~T~T~~~~=~l735~.~47\~~~~-~J' ..

LM Margin = 4.15% •••••• Output Power Req (Updated) = 130 W : ... ..,.*-

,,.

RPS PO Reserve = 1. 56% t '~ RPS PO Power Commitment = 128 W

Jan-os Jan-09 Jan -10 Jan-11 Jan-13 Jan -14 Jan-15

6

ASRG Reliability Metric- March 2013

Heate r Head

Spring

Transit ion & Feedt hru

ASC Common

Cause

Gas Bearings

ASRG System

Probability of

Failure (POF)

3.1%

Other POF

0.06%

ACU Common

Cards#l & #2

ASRG System Probability of Success

(Delivered power for 17 years) 96.9%

Card #1 (Primary)

PDF

5.4%

Output current sense & voltage

.monitor

control monitor

card lt3 (Alternate) PDF

5.4%

Questions about this graphic, Chr is Steffen (stelfen@nasa gav)

Travel is good for project communication

J

*

8

• Reliability challenge: heater head casting

• Thin-walled metallic Heater Head component (outlined in yellow)

• Ni-based super alloy Heater Head machined from casting

• Casting is known for potential oxide inclusions (ceramic flakes)

• Micro-focused Computed Tomography (CT) key to "seeing" these flaws

• Component yield was developing as an issue; parts could meet criteria

• NASA Engineering Safety Center: "criteria needs test-verified basis"

Potential orientations for oxide inclusion

Hot End (850° C)

Stirling Engine

Cold End (90° C)

Linear Alternator

ArJV;:)fJl~ArJ Stirlinn ConvArtor

(/')

u 0.. c.o rl

(/')

u 0.. 0 N

Plan: Heater Head development 1st znd

Pair Pair

ASC-Engineering Units _____ _ Need: 50% yield

Jrd

Pair

• Qual Pair MIP

• • znd Jrd

Pair Pair MIP MIP

4th

Pair

• 4th

Pair MIP

Apr-11 May-11 Jun-11 Jul-1 1 Aug-11 Sep-1 1 Oct-11 Nov-11 Dec-11 Jan-12 Feb-12 Mar-12 Apr-1 2 Moy-12 Jun-12 Jul-12 Aug-12 Sep-12 Oct-12 Nov-12 Dec-1:

Mar-11 ASC-E3 Deliveries

10 ASC-Q S-F Deliveries

• Reality: Heater Head development

ASC- Engineerin 44% yield

1st 2nd

Pair Pair Jrd

Pair

Mitigation: 5 more @ 6 months

... Qual Pair MIP

ASC-E3s: Need 4 more

Spares: Have 6 more

ASC-Fs: Need 7 more

. I

... ... 2nd 3rd

Pair Pair MIP MIP

4fh

Pair

... 4th

Pair MIP

Apr-11 May-11 Jun-11 Jul-11 Aug-11 Sep-11 Oct-11 Nov-1 1 Dec-11 Jan-12 Feb-12 Mar-12 Apr-12 May-12 Jun-12 Jul-12 Aug-12 Sep-12 Ocl-12 Nov-12 Dec-1:

Mar- 11

. 11 ASC-E3 Deliveries

ASC- Q 6- F Deliveries

Reliability challenge: heater head casting

Technical Risk: Oxide Inclusions present a risk to meeting fatigue life requirement (68 years)

Schedule Consequence: Insufficient component yield threatens critical path schedule with 3 months

Approach: Assemble investigation team and resolve in 3 months

1. Verification: Material coupon testing -+ batch specific matl props

2. Verification: Fracture mechanics & selection criteria -+ test-verified properties

3. Validation: Component stress testing -+ design specific reliability data

Goal: Resulting in test verified, design specific acceptance criteria for 4x design life on fatigue, validated with component testing

12

Skills and Assets Required

FEM Analysis

Rapid design & manufacturing

ally

Micro-focused CT scanning

Material Properties testing & Fracture Mechanics analysis

•

Structural Dynamics Testing & cumulative damage analysis

SEM Imagery

Investigation Team, core members

14

• Key Results

1. .Comprehensive approach: Sixteen* separate fatigue crack growth specimen tests Design trade study on "critical-flaw-size vs wall thickness" Refined (tighter!) acceptance criteria, supported by test-verified material.s properties

Eight qualification level vibe stress tests on five different components

2. NESC concurrence: results conclusions

residual risk for the ASRG project

3. · Timely closure: preserved system reliability and margin for fatigue life Preserved project schedule despite tighter acceptance criteria

Only possible with a badge-less team working pulling together

15

Thanks to the investigation team

• Greg McNelis- LM (co-lead)

• Dennis Petrakis- LM

• Glen Davis- Sun power

• Kyle Wilson - Sun power

• Lou Qual Is- ORNL

• Louis Ghosn - NASA GRC

• Wayne Wong - NASA GRC

• Kate McGinnis- NASA GRC

• Jeff Schreiber- Consultant, formerly GRC

• Brad Kirkwood, INL

• Jack Chan - LM

• Scott Benson, GRC -- Project Management Rep.

16

• Randy Bowman - GRC

• Ramesh Kalluri - GRC

• Dave Krause - GRC

• Jack Telesman -GRC

• Chuang Ha - LM

• Ron McNally - LM

• Gary Wood - Sun power

• Aaron Thomas- Sun power

• Kim Otten - GRC

• Sal Oriti - GRC

• Zach Williams - GRC

Consultants (NESC):

Dawn Emerson, Bob Piascik, Bill Prosser, Raju lvatury, Dave Dawicke