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THEMIS PER 1 UCB, May 02, 2005
Magnetometer BoomsPre Environmental Review
Prof. Hari Dharan
Berkeley Composites Laboratory
(Presenter: David Pankow)
Department of Mechanical Engineering
University of California at Berkeley
THEMIS PER 2 UCB, May 02, 2005
Mag Boom Requirements
REQUIREMENT VERIFICATION METHODIN.BOOM-1 Mag Boom deployment shall be repeatible to 1 degree A/T: ETU testing to verify reliability and repeatability in deployment including thermal
considerations. Flight Testing (Offloaded deployment, vibration, thermal vacuum with hot and cold first motion tests, offloaded deployment. All with mag mass dummies).
IN.BOOM-2 Mag Boom stability shall be better than 0.1 degree A/T: NASTRAN Thermal Analysis to be done, ETU testing to verify reliability and repeatability in deployment including thermal considerations.
IN.BOOM-3 Mag Boom deployed stiffness shall be greater than 0.75Hz
A/T: NASTRAN analysis; ETU tube vibration test
IN.BOOM-4 Mag Boom shall be designed to be deployed between 2 and 15 RPM about the Probe's positive Z axis.
A: NASTRAN Strength analysis
IN.BOOM-9 The SCM boom shall be approximately 1 meter long. I: Verified by inspection, measurement
IN.BOOM-10 The FGM boom shall be approximately 2 meters long. I: Verified by inspection, measurement
THEMIS PER 3 UCB, May 02, 2005
Qualification Test Sequence
Proof test of composite boom tubes Ambient, off-loaded deployment testing (e.g. 0 rpm) Qualification level vibration testing Ambient, off-loaded deployment testing (e.g. 0 rpm) Thermal vacuum testing (cycling + deployments)
• Weighted drop test (e.g. 15 rpm max)
• Ambient, off-loaded deployment testing (e.g. 0 rpm)
THEMIS PER 4 UCB, May 02, 2005
Vibration
Sine Vibration Levels (Ref. Swales SAI-TM-2430-Rev D )Qualification Sine Specification For Components
Axis Frequency (Hz) Level (g) Sweep Rate 5 - 17.7 0.5" DA
17.7 - 25 8.00 2 oct/min
25 - 35 8.00 0.75 oct/min X,Y
35 - 50 8.00 2 oct/min 5 - 5.4 0.5" DA
5.4 - 10 0.75 10 - 12 32.4 dB/oct 12 - 20 2.00 20 - 25 15.2 dB/oct
2 oct/min
25 - 35 3.50 0.75 oct/min 35 - 40 37.2 dB/oct
Z
40-50 8.00 2 oct/min
Acceptance Sine Specification For Components
Axis Frequency (Hz) Level (g) Sweep Rate 5 - 15.8 0.5" DA
15.8 - 25 6.40 4 oct/min
25 - 35 6.40 1.5 oct/min X,Y
35 - 50 6.40 4 oct/min 5 - 10 0.60
10 - 12 32.4 dB/oct 12 - 20 1.60 20 - 25 15.2 dB/oct
4 oct/min
25 - 35 2.80 1.5 oct/min 35 - 40 37.2 dB/oct
Z
40 - 50 6.40 4 oct/min
First Mode in Mag Booms is 100 Hz 8 G Rigid Body Motion
THEMIS PER 5 UCB, May 02, 2005
Vibration
Random Vibration Levels (Ref. Swales SAI-TM-2430-Rev D )
TEST RESPONSE X axis Y axis Z axis
@ FGM Sensor 30.4 Grms 36.4 Grms 27.8 Grms
@ SCM Sensor 27.3 Grms 20.6 Grms 21.5 Grms
THEMIS PER 6 UCB, May 02, 2005
Vibration Testing
Date Result Corrective Actions
2/28/05 Mounting bolts for SCB DAD tower not torqued properly. SCB DAD tower failed in Y axis.
Use torque-limiting screwdriver with extension driving bits.
3/02/05 Fatigue damage observed (between tests) in SCB base bracket’s near foot,
Add fillet to corner of near foot to reduce stress concentration.
3/07/05 Fatigue damage observed (between tests) in SCB base bracket’s near foot above fillet.
Add fillets to corner of both feet to reduce stress concentration. Add larger steel washers and G10 isolators to completely support feet.
3/11/05 Deformation observed (between tests) in SCB base bracket’s far foot.
Retrofit base with wider feet.
3/23/05 Fatigue damage observed in SCB DAD tower’s feet. Replaced with redesigned DAD tower with wider feet.
3/29/05 Booms complete vibration qualification and are tested in TV to determine functionality at hot and cold extremes. SCB has increased friction. FGB has loss of preload in frangi-bolt ring from stripped threads in frangi-bolt ring (Build/Test Mistake)
Add deployment testing after vibration and before TV testing.
Tightened spool to holds the base spring subassembly.
4/08/05 5% Frequency shift with no visible damage. SS washers added to (non-load bearing) surfaces to eliminate observed fretting.
4/25/05 Similar frequency shift in SCB after first X random test.
Abnormal frequency response caused by G10 spacers.
Booms survived structurally but increased friction was noted during subsequent deployment.
Frequency response stable after second random vibration • G10 spacers were removed prior to continuing with vibration • Lubrication and improvement of rubbing surfaces • Offloading force incorrect during deploy. Booms deploys when offload corrected.
Next (and last ?) F1 MB qual. vibration test is scheduled for this Friday, May 6
THEMIS PER 7 UCB, May 02, 2005
Vibration Testing
Flexible Feet for CFRP Deck CTE mismatch
Axial Load Bearing Shaft Interface
NON - Load Bearing Interface
BASE HINGE VIBRATION PROBLEMS ILLUSTRATION
THEMIS PER 8 UCB, May 02, 2005
PFR
PFR Status Title
PFR-025 CLOSED Cracked feet in SCB frangibolt/DAD tower
PFR-027 CLOSED Cracked Base Bracket in SCB
PFR-035 CLOSED Spring spool in SCB base hinge loosened by vibration.
PFR-036 CLOSED Damaged threads in FGB frangibolt ring.
• F1 booms re-designated F6 flight spare because of the accumulated random vibration time
THEMIS PER 9 UCB, May 02, 2005
SCM/FGM Boom Thermal Testing Status
THEMIS PER 10 UCB, May 02, 2005
Thermal Vacuum Testing
-150
-100
-50
0
50
100
0 10 20 30 40 50 60 70 80
Tem
per
atu
re /C
-115C, 4h
75C, 4h 75C, 4h
-115C, 4h
75C, 4h75C, 12h
50C, Hot Deploy
-40C, Cold Deploy
Restow
THEMIS PER 11 UCB, May 02, 2005
Thermal Vacuum
Joint sample of representative joint and carbon tube tested to –135C to 65C.
Mag booms survived one cycle of temperature extremes (-115 to 75C) + subsequent re-vibration.
Frangibolt actuator survived temperature extremes.
• Both booms failed subsequent deployment• FGM due to the previously stripped thread
• SCM due to excessive drag from off loading GSE.
THEMIS PER 12 UCB, May 02, 2005
BACKUP SLIDES
Bob Coladonato (GSFC ret.) on the FEMCI Websitehttp://femci.gsfc.nasa.gov/random/randomtestspec.html
ONE MAN’S (controversial ?) OPINION
THEMIS PER 13 UCB, May 02, 2005
BACKUP SLIDES
ANOTHER MAN’S (controversial ?) OPINION
David,
I don't know where you are in the THEMIS I&T process, but let me suggest, in the interest of saving the time and money associated with unnecessary test failures, that you not test the components and instruments to the high random vibration levels that Swales was proposing when I did that vibro-acoustic study for you a year or so ago. Rather, vibration test the components and instruments for workmanship, and then do acoustic tests of the individual probes and bus, and then an acoustic test, and perhaps a random vibration test, of the assembled spacecraft.
If Frank Snow balks at this "deferred risk" approach, remind him of his ACE spacecraft project, where the flight data gathered by the GSFC onboard measurement system (SLAM) showed that the flight acoustic and random vibration levels were 20 dB below the test levels. (and, Ed Stone's, CHRIS instrument had a failure during its high level random vibration test, in spite of force limiting.)
Best Regards,
Terry Scharton (JPL ret. - “the invaluable maverick”) 30 Mar 2005