SMAP Transportation Load Analysis
Transcript of SMAP Transportation Load Analysis
(c) 2015 California Institute of Technology. Government sponsorship acknowledged
SMAP Transportation Load Analysis
Peyman MohassebJet Propulsion Laboratory - Spacecraft Structures and Dynamics GroupCalifornia Institute of Technology
Gary WangJet Propulsion Laboratory - Dynamics and Structures GroupCalifornia Institute of Technology
June 2 – 4, 2015
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Acknowledgement
• Walter Tsuha• Ali Kolani• Michael Long• Will Krieger• Mike Van Dyke• Armen Derkevorkian• Ben Tsoi
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Outline
• SMAP Mission Overview• Transportation Overview• Transportation Load Analysis Approach
– Random Vibration Analysis based on Military Standard• Isolation study• Clearance study
– Transient Time History Analysis based on Road-Test data• Mass Mock-up road test configuration• Analysis approach and input justification
• Observatory response comparison to design loads• SMAP Observatory transportation measurement• Conclusion
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Mission Overview
• SMAP (Soil-Moisture-Active-Passive) provides global observations of soil moisture and freeze/thaw state (the hydrosphere state). SMAP hydrosphere state measurements will be used to enhance understanding of processes that link the water, energy and carbon cycles, and to extend the capabilities of weather and climate prediction models.
• SMAP Observatory was successfully Launched on January 31st , 2015
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SMAP Observatory Transportation
• SMAP Observatory was successfully transported from Jet Propulsion Laboratory (JPL) to Vandenberg Air Force Base (AFB) on October 15, 2014 using an air-ride truck
• The transportation configuration consisted of the SMAP Observatory cantilever mounted to a transportation fixture supported by six wire-rope isolators interfacing the truck-bed through a supporting frame. The transportation fixture was chained onto the truck-bed
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Isolator Frame & Aeroflex Isolators
P/N H W Load Mode Shock AverageK(lb/in)
Vibration AverageK(lb/in)
Max. Rated Dynamic
Travel (in)
CB1500-505/8” wire rope
5.30 7.0 CompressionShear/Roll
45° C/R
795410410
17005501275
3.203.204.40
CB1700-307/8” wire rope
7.50 8.25 CompressionShear/Roll
45° C/R
19259001140
47508153250
3.603.604.80
CB1500-506 places
CB1700-302 places
Isolation FrameAssembly
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Air-Ride Truck Suspension Information
SV424 Kentucky Hi Cube 40’ trailer suspension• 2 Axles with 2 Airbags per axle• Neway AR75-9-LK-5RD Suspension • Goodyear 1R12-498 Air Springs @ 670 lbf/in)
SV317 or SV318 Peterbuilt tractor suspension• 2 Drive axles with 2 Bags per drive axle• Goodyear 1R12-069 Air Springs @ 830
lbf/in)
SV424 trailer weight is 22,720 lbswith a full tank of fuel for air conditioner, including axels and wheels• Trailer container weight ~ 8500 lbs• Rough estimate of air springs
isolation mode ~ 2 Hz
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Transportation Load Analysis Approach
• Two approaches were considered to predict the transportation loads the Observatory can survive:– Random vibration analysis using Military Standard 810E (MIL-STD-810E) transportation
environment – Transient response analysis using the time history acceleration data collected during the
mockup road test
• While the MIL-STD random vibration approach is generally conservative and doesn’t require conducting road test to validate the results, the accuracy of such results depends on the accuracy of the overall system finite model representing the transportation configuration– The accuracy of the final results were questionable since the system level FEM was not
modally correlated
• Alternatively, JPL developed a time history base drive approach using the mass mockup road test data to define the acceleration input at the mockup/fixture interface. – More accurate observatory dynamic response results can be obtained since the observatory
FEM was correlated by modal testing
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Random Vibration Analysis using Military Standard Environment
• A full FEA of the SMAP Observatory, Transportation Fixture, and Isolator Pallet was developed– Isolators were modeled as CBUSH spring elements with
vendor’ specified stiffnesses
• Mil-STD-810E “Environmental Test Methods and Engineering Guidelines”, Section I-3.3 Transportation Vibration– Compared with OBS tested random vibration input OBS FEM + Fixture + Isolator
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Random Vibe Analysis - Isolation Study
• Random Vibe analysis study based on Mil-STD 810E inputa. Without Isolator (green)b. With Isolator (blue)
• Use of isolators was deemed necessary since the acceleration results without isolator exceeds design load
Observatory CG Acceleration
Excitation Direction
Design Limit Load *1.25
Random Vibe without Isolator
Random Vibe with Isolator
(g) (g, 3σ) (g, 3σ)X 3.75 5.9 3.0Y 3.75 0.8 0.2Z 12.0 5.6 1.2
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Random Vibe Analysis - Clearance Study
• Displacement at the XLGA and SLGA on the outrigger was estimated using the semi correlated system model FEM (including the Isolators, Fixture and Observatory)– Max. displacement in the Y direction is 0.3 inches which is within the
allowable of ~ 4 inches clearance from observatory to the truck wall
X-Input Y-Input Z-Input
X-Input Y-Input Z-Input(in, 3σ) (in, 3σ) (in, 3σ)
XLGA 29001 2.27 0.30 1.57SLGA 29002 2.27 0.28 1.54
NIDComponent
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Transient Time History Analysis
• To obtain more accurate results, JPL developed a time history base drive approach per mockup road test data:– Uses the mass mockup road test data to define
the acceleration input at the mockup/fixture interface
– Applies the interface acceleration time histories as the Mockup base excitation input to predict it’s dynamic responses
– Validates the accuracy of such an approach through comparison of the calculated dynamic responses of the mockup to the test accelerometer data
– Predicts the Observatory dynamic responses such as CG accelerations and interface forces per road test interface acceleration input
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Transportation Fixture(2866 lbs)
Isolation Frame(448 lbs)
Tie Down Plate6 pl.
SMAP Mass Mock-up(2368 lbs)
Total weight = 5682 lbs
Aeroflex Isolators
Aeroflex Isolators
Mockup Road Test -Transportation Configuration
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A3 (400 Hz)6:00 position
A1 (400 Hz)12:00 position
A2 (400 Hz)3:00 position
A4 (400 Hz)9:00 position X
Z out ofpage Y
XYZ out of
pageX
Y
Z out ofpage
X
YZ out ofpage
Axial
Vertical
Lateral
OBS X-Axis
OBS Y-Axis
OBS Z-Axis
Mass Mockup, DTM prop deck, DTM LVA, LVA Saver
Axial
Vertical
Lateral
A11-12 (1x 50 Hz & 1x 400 Hz)On the center tip of the mockup
X
ZY into page
Fixture Plate
Critical Data Logger Locations
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• Van’s Floor by Wooden Block (A5-A7)• On the Fixture frame and right above Isolators (A8-A10)
Accelerameter Locations
Padding
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2.06 g
A4 (Fixture-Mockup I/F) time historyAnalysis time history is 5-second slice centered on this event
LateralVertical
Axial
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A12 (Mockup tip) time historyAnalysis time history is 5-second slice centered on this event
VerticalLateral
Axial
2.09 g
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Mockup Road Test: A1-A4 Response Accel PSD
2-Hz mode
16-Hz mode
42-Hz mode
11-Hz mode
A1-A4 vertical accel PSD
16-Hz mode
42-Hz mode11-Hz mode
16-Hz mode
35-Hz mode
11-Hz mode
A1-A4 Axial accel PSD
A1-A4 Lateral accel PSD
• The first 2 Hz Mode is due to the Air Ride Van suspension system (matched well with our prediction)
• Wire-rope Isolators in conjunction with the Mockup and fixture assembly show prominent modes at 11 Hz and 16 Hz
• All responses beyond 16 Hz are significantly reduced due to isolation system
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Transient Time-History Dynamic Analysis Approach
• Time history data recorded through A1 – A4 data logger is used as the forcing function to both the Mass Mockup and Observatory FEM– 5 second data capturing the peak g’s throughout the
entire road test– Modal Transient Analysis using NX Nastran is
performed– 12 (4x 3DOF) time history inputs are applied to the
model simultaneously at the 4 data logger locations• 1g vertical is applied manually
– Rotation motions are captured – Response at the Mass Mockup Tip (A12) is
compared with the test data
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0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
0.5
1
1.5
2
2.5
Time (s)
Res
pons
e (g
)
Input XCG XTip X
Tip, 2.28 g’s
Input, 2.09 g’s
Mass Mockup Response - Vertical
C.G, 2.14 g’s
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Mass Mockup’s Tip Acceleration Comparison
• The base drive time history analysis predicts the mockup tip dynamic response max lateral accel is 14% higher than actual road test data
• The results were promising in gaining confidence in the transient dynamic analysis
Mass Mockup Tip Response Comparison
Predicted Min
Predicted Max
Road TestMax. Prediction/ Road Test
TX (g) 0.17 2.28 2.09 1.09TY (g) -0.59 0.77 0.35 2.20
Lateral (g) 0.61 2.41 2.12 1.14TZ (g) -0.49 0.36 0.48 0.75
Bas
e D
rive
T-H
Exc
itatio
n
Mockup Tip
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Observatory vs. Mockup Mass and Frequency
Mass (lb)CG Z-offset from 1" Fixture
Plate Interface (In)1st Lateral Freq
(Hz)
Mockup 2368 43.1 37
Observatory 1881 54.1 17.6
• Since the first frequency of the Observatory at 17.6 Hz was close to the road test frequency of 16 Hz, there was a concern whether the base acceleration date (A1-A4) obtained from the Mockup road test would bound the Observatory base input during the actual transportation
• The next three slides provide justifications for this approach
Mass Mockup FEM
SMAP OBS FEM
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Input Justification (1/3)
• Does the road test based input at the Mockup/Fixture interface (A1-A4) bound the actual transportation for the Observatory? – Mass Mockup first bending mode = 37 Hz– Observatory first bending mode = 18 Hz– Fixture/Isolator/Mockup coupled frequency = 11 Hz & 16 Hz – Fixture/Isolator frequency = 24 Hz (No Mockup)
• Road Test data showed that the apparent roll-off frequency is at ~16 Hz• Two analysis approaches were taken both using a 0.01 g^2/Hz random
vibration white noise as base excitation:– Simplified 2-DOF Mass-Spring System– Full 3D FEA
• Studies showed that using Mass Mockup A1-A4 road test input was slightly conservative
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Input Justification (2/3)
• Analytical Approach – 2-DOF System– 2 DOF system consists of:• DOF1: Mockup or Observatory• DOF2: Fixture/Isolator
– Study has shown:• Switching from Mockup to Observatory
generates a notch at 18 Hz, also shifts the first Mockup mode frequency from 14 Hz to 12 Hz
• Reduces the Fixture response by 12% • Above phenomenon is a result of
Observatory mass and the Fixture mass being comparable
100
101
102
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
Frequency
g2 /Hz
Load Oscillator Uncoupled fn = 40 Hz
Fixture 1.58 grmsLoad 1.83 grms
14.1 Hz
100
101
102
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
Frequency
g2 /Hz
Load Oscillator Uncoupled fn = 18 Hz
Fixture 1.39 grmsLoad 2.68 grms
12.8 Hz
Mockup
OBS
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Input Justification (3/3)
• 3D FEA Approach – Random Vibration Analysis – Based on semi-correlated system model – including the Isolators, Fixture and
Mockup– White-noise random input – 0.01 g^2/Hz from 1 Hz to 20 Hz in the vertical direction
(X)– Recover the response at the Fixture interface (A1 – A4) • With Mass Mockup 0.63 g_rms• With Observatory 0.61 g_rms• 3% reduction
Isolator+Fixture+Mockup FEM Isolator+Fixture+OBS FEM
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0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 50
0.5
1
1.5
2
2.5
3
Time (s)
Res
pons
e (g
)
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-1
-0.5
0
0.5
1
Time (s)
Res
pons
e (g
)
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-0.6
-0.4
-0.2
0
0.2
0.4
Time (s)
Res
pons
e (g
)
Input TXCG TX
Input TYCG TY
Input TZCG TZ
Observatory Responses - Translation
OBS CG_TX, 2.52 g’s Input TX 2.06 g’s
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Observatory vs. Mockup Response Comparison
OBS C.G Mockup C.G
Mass (lbs) = 1881 2368
Z-offset (in) = 54.1 43.1
Max Min Max Min
TX (g) 2.52 0.17 2.14 0.57
TY (g) 0.84 -0.73 0.5 -0.64
TZ (g) 0.36 -0.5 0.35 -0.44
OBS Base Force Mockup Base Force
Mass (lbs) = 1881 2368
Z-offset (in) = 54.1 43.1
Max Min Max Min
TX (lbf) 4733 315 5068 698
TY (lbf) 1570 -1377 1191 -888
TZ (lbf) 682 -932 826 -1133
MX (in-lbf) 116296 -135453 51012 -68115
MY (in-lbf) 291072 -21452 226788 24721
• Dynamic response predicted Observatory CG acceleration and base forces are generally higher than Mockup’s as shown above – This is to be expected since the first mode for Observatory at 17.6 Hz
(versus 37 Hz for Mockup) is closer to the road test 16 Hz input data
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Observatory Response Vs Design Load Comparison
• The observatory CG acceleration based on DLx1.25 is 22% higher than the max transportation Predicted+ Uncertainty
• Static test base forces are at least 31% higher than the transportation Predictions + Uncertainty
Observatory Accel Summary
Dynamic Response Predictions
Dynamic Response + 25% Uncertainty on dynamic portion of
the load VLCDesign Load (MMAc6a) DLLX1.25
DLLx 1.25 / (Prediction+Un
certainty)Max CG Tx (g) 2.52 2.9Max CG Ty (g) 0.84 1.05
Max Lateral CG (g) 2.66 3.08 2.4 3 3.75 1.22
Observatory Load Summary
Dynamic Response Predictions
Dynamic Response + 25% Uncertatinty on dynamic
portion of the load VLC (LVA Base)
Design Load (MMAC6a -LVA Base)
SC Static Test
(LVA base)
SC Static Test / Prediction+
UncrtaintyVx 4733 5445Vy 1570 1963
V_Rss 4987 5788 5311 8203 7600 1.31Mx 135453 169316My 291072 326000
M_Rss 321046 367347 314112 502254 628960 1.71
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SC and SA Top Level Assessment
Transportation Prediction Design Load (MMAC6a)
Grid ID Description Mass (kg) Ax (g) Ay (g) Az (g) Ax (g) Ay (g) Az (g)9007 SAR HPA (-Y) 19 2.4 0.8 0.5 3.5 7.8 2.59026 CDHA (-X) 10.8 2.5 0.7 0.4 10.4 5.6 2.6
9029 PDA+PCA (-X) 16.2 2.3 0.4 0.4 7.3 3.4 2.99033 Main Battery 22.8 2.2 0.5 0.5 9.1 14.8 8.09042 RW1 (Top) 19.3 2.4 0.6 0.4 6.5 6.0 8.69043 RW2 (Top) 19.3 2.4 0.7 0.6 6.0 6.8 9.19044 RW3 (Bot) 19.3 2.3 0.5 0.6 8.8 8.5 10.4
Element ID DescriptionTransportation Prediction (lbs)
Design Load (lbs) VLC (lbs)
31524 SA Strut 61 1186 51431526 SA Strut 69 1154 54531528 SA Strut 173 2458 106031530 SA Strut 95 1371 53431532 SA Strut 101 1407 58131534 SA Strut 200 2372 1064
• All OBS major component accelerations and strut forces are much lower the design loads
Transportation FLL(g's) (g's)
T1 2.6 23.0T2 1.0 23.0T3 0.6 19.7T1 3.2 8.8T2 1.8 8.4T3 0.9 10.7T1 3.2 9.2T2 2.2 7.9T3 1.1 11.5T1 2.3 9.9T2 0.5 4.7T3 1.2 8.9T1 6.6 28.0T2 7.0 32.4T3 1.2 8.9T1 4.3 25.2T2 3.2 23.1T3 0.8 10.7
Component NID DOF
1302073
1600139
1700001
2292001
2330105
4100013
CCA Inner Cone
RDE Mass
ICE Mass
RBA RDD
RBA Elbow
IFA Radome
Instrument componentsSpacecraft components
Solar Array struts
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SMAP Observatory Actual Transportation Data
(from JPL to Vandenberg)
During the actual transportation of the Observatory numerous accelerometers were mounted on the Van’s floor (A5-A7) as well as the base of the Observatory on the fixture plate (A1-A4)
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OBS Transportation – A1-A6 Vertical T-H Data
• Max A1-A4 : 1.90 g’s (Base of FSR)• Max A5-A6 : 2.5 g’s (Van’s Floor)
• Base Isolation has been very effective in reducing acceleration for the vertical direction
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OBS Transportation – A1-A6 Lateral T-H Data
• Max A1-A4 : 0.47 g’s (Base of FSR)• Max A5-A6 : 0.63 g’s (Van’s Floor)
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OBS Transportation – A1-A4 Axial T-H Data
• Max A1-A4 : 0.33 g’s (Base of FSR)• Max A5-A6 : 0.82 g’s (Van’s Floor)
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OBS Transportation – A1-A4 PDS Curves
• Base Isolation system has successfully reduced all responses beyond 14 -18 Hz range
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• The actual transportation test data clearly showed the isolation system had been very effective particularly, in the critical vertical direction reducing the input level from 2.50 g’s to 1.90 g’s– All responses beyond 15 Hz were significantly reduced due to the Isolation system
• The transient dynamic analytical approach adapted by JPL in conjunction with the Mockup road test input data yielded results which closely correlated with the actual transportation acceleration test data
A1-A4 OBS Base Acceleration (g's)Predicated Actual
Vertical 2.06 1.90Lateral 0.18 0.47Axial 0.42 0.33
Conclusion