The U.S. Department of Energy (DOE), Lockheed Martin Corporation (LM), and NASA Glenn Research Center (GRC) have been developing the Advanced Stirling Radioisotope Generator (ASRG) for use as a power system for space science missions. As part of the extended operation testing of this power system, the Advanced Stirling Convertors (ASC) at NASA GRC undergo a vibration test sequence intended to simulate the vibration history that an ASC would experience when used in an ASRG for a space mission. This sequence includes testing at workmanship and flight acceptance levels interspersed with periods of extended operation to simulate prefueling and post fueling. The final step in the test sequence utilizes additional testing at flight acceptance levels to simulate launch. To better replicate the acceleration profile seen by an ASC incorporated into an ASRG, the input spectra used in testing the convertors was modified based on dynamic testing of the ASRG Engineering Unit (ASRG EU) at LM. This paper outlines the overall test approach, summarizes the test results from the ASRG EU, describes the incorporation of those results into the test approach, and presents the results of applying the test approach to the ASC-1 #3 and #4 convertors. The test results include data from several accelerometers mounted on the convertors as well as the piston position and output power variables

Hill, Dennis

Meer, David W.

Ursic, Joseph J.

NASA Technical Reports Server

Advanced Stirling Convertor Dynamic Test Approach and Results

The U.S. Department of Energy (DOE), Lockheed Martin (LM), and NASA Glenn Research Center (GRC) have been developing the Advanced Stirling Radioisotope Generator (ASRG) for use as a power system for space science missions. As part of the extended operation testing of this power system, the Advanced Stirling Converters (ASC) at NASA John H. Glenn Research Center undergo a vibration test sequence intended to simulate the vibration history of an ASC used in an ASRG for a space mission. This sequence includes testing at Workmanship and Flight Acceptance levels interspersed with periods of extended operation to simulate pre and post fueling. The final step in the test sequence utilizes additional testing at Flight Acceptance levels to simulate launch. To better replicate the acceleration profile seen by an ASC incorporated into an ASRG, the input spectra used in testing the convertors was modified based on dynamic testing of the ASRG Engineering Unit ( ASRG-EU) at Lockheed Martin. This paper presents the vibration test plan for current and future ASC units, including the modified input spectra, and the results of recent tests using these spectra. The test results include data from several accelerometers mounted on the convertors as well as the piston position and output power variables

Ursic, Joseph

Summary of Oral Presentation/viewgraphs: 
The U.S. Department of Energy (DOE), Lockheed Martin (LM), and NASA Glenn 
Research Center (GRC) have been developing the Advanced Stirling Radioisotope 
Generator (ASRG) for use as a power system for space science missions. As part of the 
extended operation testing of this power system, the Advanced Stirling Converters (ASC) 
at NASA John H. Glenn Research Center undergo a vibration test sequence intended to 
simulate the vibration history of an ASC used in an ASRG for a space mission. This 
sequence includes testing at Workmanship and Flight Acceptance levels interspersed with 
periods of extended operation to simulate pre and post fueling. The fmal step in the test 
sequence utilizes additional testing at Flight Acceptance levels to simulate launch. To better 
replicate the acceleration profile seen by an ASC incorporated into an ASRG, the input 
spectra used in testing the convertors was modified based on dynamic testing of the ASRG 
Engineering Unit ( ASRG-EU) at Lockheed Martin. This paper presents the vibration test 
plan for current and future ASC units, including the modified input spectra, and the 
results of recent tests using these spectra. The test results include data from several 
accelerometers mounted on the convertors as well as the piston position and output power 
variables. 
https://ntrs.nasa.gov/search.jsp?R=20120016633 2019-08-30T23:15:28+00:00Z
" 
Advanced Stirling Convertor Dynamic Test Approach 
and Results 
David W. Meer 
Dennis Hill 
Joseph Ursic 
Sest, Inc. tOCIfH"D MAItTlN 1 
Sest, Inc. , Middleburg Heights, OH 
Lockheed Martin Space Systems Company, 
King of Prussia, PA 
Analex Corporation, Cleveland, OH 
Glenn Research Center at Lewis Field 
Outline 
• Objectives of Advanced Stirling Convertor (ASC) dynamic test program 
• Advanced Stirling Radioisotope Generator (ASRG) test results 
• T est Article 
• Test Plan 
- Fixture Characterization 
- Instrumentation 
• Vibration Test Results 
- Standard profile input 
- Shaped profile 
- Convertor performance 
• Summary 
• Conclusions 
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2 
Introduction - ASRG and Launch Interface 
Spacecraft 
Isolation 
Adapter 
Triaxial 
Accelerometers 
Inboard 
ASC-E Outboard 
ASC-E 
• Nominal 143 We Stirling radioisotope generator; 28 % efficiency @ 
20.2 kg 
• Spacecraft isolation adapter designed to achieve fundamental 
generator lateral and axial modes 
• Above spacecraft primary structure / below convertor operation 
Sest, Inc. tOC"",.lI MAlfTIN f Glenn Research Center at Lewis Field 
3 
Dynamic Test Program Objectives 
• Perform extended life testing of Stirling 
power systems to demonstrate long term 
reliability 
• Replicate vibration exposure experienced • 
by flight unit 
• Workmanship test 
• Fueling 
• Operational testing 
• Flight acceptance test 
• Storage for up to 3 years 
• Launch 
• Operation up to 14 years 
• Maximize extended operation testing / 
minimize down time 
Sest, Inc. LOCHHrED MARTIN ,~ QinetiQ I .v.;";l· .. x 
- "N'(i;'ii;"A",l'rit.i - ~
Extended operation vibration 
test schedule 
• Workmanship test 
• Extended operation test 
5000 - 10000 hours 
• Flight acceptance test 
• Launch simulation 
• Extended operation 
Glenn Research Center at Lewis Field 
4 
", 
ASRG Engineering Unit (ASRG EU) 
Dynamic Testing 
• Tested to flight qualification levels using 
JPL RPS standard profile in all three 
axes 
• Axial - in-axis with ASC-E piston motion 
• Lateral - 2 axes perpendicular to 
direction of piston motion 
• Instrumentation 
~ Internal 
- 2 triaxial accelerometers on ASC-E pressure 
vessels 
- 8 strain gages on ASC-E heater heads 
- 2 strain gages on ASC-E CSAFs 
~ External 
- 22 uniaxial accelerometers 
- 4 strain gages on housing 
========4=s=tra=in~ga~g~es~o~n~S~/C~is~ol~at~io~n~a~d~ap~te~r _____________________________ ~ 
'0 C ••••• II A • , I N j Glenn Research Center at Lewis Field • Sest, Inc. 
5 
ASRG EU Dynamic Test Results 
• Results from ASRG EU 
testing 
• 
• 
• 
Highest accelerations from 
both inboard and outboard 
ASC-E pressure vessel 
triaxial accelerometers 
Scaled down from 
qualification level to flight 
acceptance level (-3 dB) 
Target spectra for life 
testing for flight 
acceptance and launch 
simulation 
Sest, Inc. L O CKHEED MART I N . . ~ 
1 ASRG-EU Accelerations 
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- - - - - - - - - -- - - - - - - - -- - - - - - - - -- - - - - - - - - - - - --- - --- - - - - - - - ---
2 
10 Frequency (Hz) 
Glenn Research Center at Lewis Field 
6 
.. 
Test Article: ASC-O 
• Inconel heater head 
- 625 °C hot-end 
• Cold-end 60°C 
• > 70 We output 
• 4.40 mm piston 
amplitude 
Sest, Inc. iOCIlH'.D MART',. j 
Heater Head 
Pressure vessel 
Cold side 
adapter flange 
(CSAF) 
Glenn Research Center at Lewis Field 
7 
Test Fixture and Instrumentation 
Heater head accelerometer Control 
accelerometers 
Sest, Inc. LOCKHEED MARTIN -.j;,. QinetiQ I ..-Q·-x -N~ ft~ 
Pressure vessel 
accelerometer 
Glenn Research Center at Lewis Field 
8 
Test Plan 
• Fixture characterization 
• First convertor 
- Standard RPS profile 
- Sine sweep 
- Flight acceptance 
- Launch simulation 
- Sine sweep 
- X (lateral) , Y (axial), and Z (lateral) axes 
• Evaluate results 
• Second convertor 
- Modified profiles from ASRG EU data 
- Same sequence 
==-------------------~ 
to crN flO .... ". 1- Glenn Research Center at Lewis Field • 
9 
Sest, Illc. 
o X Axis Response - Lateral 
10 m~:~nmmmm:mml 
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- - 1-1 .. - - - - n 
.3 I I I , , : , I I . " J: 
10 ' " '" , " ' " 
10' 
Frequency (Hz) 
o Z Axis Response· Lateral 
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~ 10 ' ~~!~~y~~~ ~,: ,:h~~11 
t\lE,! ~~:::~:~' ::::::::~~~ ::4 
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'- _ ' _' .-1 ... _ _ _ 
-3 1 I ' , ' , I I 10 c-~~~~-~~~~~--' 
10' 10' 
Frequency (Hz) 
First Convertor Results 
• 
• 
Frequency (Hz) 
• 
Standard RPS 
profile input 
No significant 
fixtu re / test 
article dynamics 
< 1000 Hz 
Use target 
spectra as input 
for next test 
Sest, Inc. LOCKHEED M ARTIN Glenn Research Center at Lewis Field 
10 
'. 
Second Convertor Results 
• 
• 
• 
Lateral spectra 
required little 
modification to 
replicate ASRG 
EU dynamics 
Axial spectra 
did require a 
few iterations 
Both match 
ASRG EU data 
at pressure 
vessel 
Sest, Illc. 
Acceleration Comparison - Lateral Axes 
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{ 10 
o ·2 
en 10 
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~--~-4-~-~-,-r-------~-----,---·--r-T-T- -~--------
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~~~~!:~:p~~ii~i;;';;~~;!:;i:o:~ 
--ASC-E #4 Control 
ASC-E #4 Pressure Vessel ~ ~; i i ~i ii i ~i i i t i i~ i t i ~ i~ t ~i i i; iii 
10_4 t===~==JPL~=F=195h=t =A~cc=e~p=~~e}:::::::~:~:~:~~:::::::~:~~~':~:~:~;~::::~~~:~:~:~:~:~~:::~~~:~:~:~:~::::~:~-j 
10' 
N -1 
I 10 ~ 
~ 10.2 
., 
10 
102 10
3 
F",quency (Hz) 
Acceleration Comparison· Axial A>is 
~~~~~~~~~~~~~~~~~~:~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~§~~~~ 
---- r- -~--~-4-~-t-!-r-------~----4------r-T-t-~t~--------
~~~~~~~~~~~~~~~~t~~~~~i!i~~~~~~~~~~~~~~~~t~~~~~~~~~~-i~~ 
====c==~==~=~=~:r:l-c-- __ = _-:=~==:I=:c=r:I=CI~=== --
----r -- 4- - '--- - ------,- --~---T--r-T-T-~T'--~ ~ --
= = =~ ~ ~ ~:J~ ~ ~ ~ ~:~ ~~ rr:~~ ~ ~ ~ ~ ~~ ~~~ ~~: ~~~~ ~ ~ ~~-~~ ~ ~ ~~ ~ ~~. ~' ~ ~.~ ~ ~ 
----r--4--T--I-~-T4-r-------'-----I- --r- - ,-- -
-- ASRG-EU Pressure Vessel ;;;;;;;~;~;;;:;:t = = _ =!; ~ ;:; i ~=:;; ; =-
-- ASC-E #4 Control ::::~::: :~::: :: :: :~:!:::; :~::::: =:::::: 
Frequency (Hz) 
Glenn Research Center at Lewis Field • 
" 
Piston Position Excursions During Vibration 
::: 
.... 
o 
.... 
.... 
V:. 
o 
~ 
ASC-O #4 Piston Position Change During Vibration Test 
20 r--- -
I 
15 J 
Max Piston Position - Lateral Test ': j 
O ~~----~----------~ 
'I 
-10 " 
Min Piston Position - Lateral Test 
Min Piston position~- Ax::ia~lT;::.e;st---J I -15 1 
-20 +, ---,---- - -,-----,.-- - ,-------1 
o 0.2 0.4 0.6 0.8 1 
Fraction of Accel)tance Leyel 
Sest, Inc. LO C KHEE D MART i~ QinetiQ I ~·-x 
- NortiiA;rn:;;(-, 
• Convertors 
more sensitive 
to axial 
vibration 
• Piston position 
stayed within 
20 % of 
nominal up to 
flight 
acceptance 
levels 
• Used < 50% of 
safety margin 
Glenn Research Center at Lewis Field 
12 
.. 
Convertor Performance During Axial 
Vibration 
Axial Launch Simulation Test 
6 50~ 
: J ~ + ... I f ~ -500 50 100 150 200 250 
- 4 
I 2 .. 0 -2 " . • -4 
-6 ~ 0 50 100 150 200 250 
~ 80 : ~ ! 60 •• 
0 50 100 150 200 250 
~ 
': ! 
: ~ . ~ . : ~"W " : 'I == 1 ~ d 
-10 
0 50 100 150 200 250 
~ 50 
~ 0 
~ - 50 
0 50 100 150 200 250 
tirre (5) 
• Step up in acceleration (-12 dB, -6 dB, flight acceptance, none) 
• Piston position, alternator voltage, and alternator current affected by 
amplitude of axial vibration 
• Convertor performance quickly returns to normal after vibration 
Sest, Illc. QinetiQ I "~LEX 
- N' .. lhA ..... "r~ ~ 
Glenn Research Center at Lewis Field 
13 
Conclusions 
• ASC Extended Life Dynamic Test Plan 
- Plan developed to replicate the vibration exposure experienced by a 
typical flight unit while maximizing extended operation time 
• Data collected from dynamic test of ASRG EU 
- Largest amplitude acceleration seen by inboard or outboard 
pressure vessel accelerometer combined to form spectra 
Scaled from qualification to flight acceptance levels 
• Fixture characterization and testing with standard input profile showed 
no significant fixture dynamics 
• Shaped spectra produced good agreement between pressure vessel 
and ASRG EU data 
• Convertors demonstrated robustness to vibration when operating at 
launch conditions and exposed to shaped spectra 
Sest, Inc. L 0 C K H E E D MAR TIN ,} Glenn Research Center at Lewis Field 
14 
. " 
. . . . 
. . 
• 
,. 
Acknowledgements 
This work was enabled through the Department of Energy (DOE) Stirling 
Radioisotope Generator (SRG110) program and through NASA Science Mission 
Directorate Funding. Any opinions, findings, and conclusions or recommendations 
expressed in this presentation are those of the presenter and do not necessarily 
reflect the views of the National Aeronautics and Space Administration. 
Contributions from: 
• Scott Cutlip and Jim Szelagowski - NASA GRC 
• Jack Chan - Lockheed Martin 
• Rebecca Richardson - DOE 
• Jeffery Schreiber and Richard Shaltens - NASA GRC 
Questions? 
==--- ............... ---• . 
,. c •• f f ..... TIN j Glenn Research Center at Lewis Field Sest, Inc. 
15 


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