themis per 1 ucb, may 02, 2005 magnetometer booms pre environmental review prof. hari dharan...

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


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


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)


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


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


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


Vibration Testing

Flexible Feet for CFRP Deck CTE mismatch

Axial Load Bearing Shaft Interface

NON - Load Bearing Interface

BASE HINGE VIBRATION PROBLEMS ILLUSTRATION


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


SCM/FGM Boom Thermal Testing Status


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


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.


BACKUP SLIDES

Bob Coladonato (GSFC ret.) on the FEMCI Websitehttp://femci.gsfc.nasa.gov/random/randomtestspec.html

ONE MAN’S (controversial ?) OPINION


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

themis per 1 ucb, may 02, 2005 magnetometer booms pre environmental review prof. hari dharan...

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