Download - ELM: ESPA Launch Load Module
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ELM: ELM: ESPA Launch Load ModuleESPA Launch Load ModuleDepartment of Mechanical & Industrial Engineering
Northeastern UniversityBoston, MA 02115
April 17, 2007
Ben Kneppers, Matthew Krenek, Nate Matcheson,Rachelle Parsons, and Rylan Summit
Advisor:Dr. Sinan Muftu
In Conjunction with : :
CSA Engineering, Inc.
Mountain View, CA
NASA Ames Research Center
Moffett Field, CA
Santa Clara UniversitySanta Clara, CA
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ESPA: ESPA: EELV Secondary Payload EELV Secondary Payload
AdapterAdapter•Located between the primary payload and EELV
•Holds up to 6 additional payloads
•Actual loads unknown
•Estimated 10 g’s simultaneously in lateral/axial
•Probably over engineered
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ELM:ELM:ESPA Launch Load ModuleESPA Launch Load Module
•Secondary Payloads are cantilevered from the ESPA ports; no other payloads are mounted this way
•Measure flight environment loads experienced by ESPA and secondary payloads
•Provide data for more accurate and less expensive engineering
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Goals and RequirementsGoals and RequirementsTo develop an ESPA Launch Load Module (ELM) capable
of measuring various environment conditions experienced by the 62 inch ESPA during the launch and
flight of Delta IV and Atlas V spacecrafts.
To fulfill this Goal, the following requirements must be met:
• Maintain minimum stiffness of 500 Hz • Maintain functionality throughout launch and
flight• Self powered• Measuring Devices
– Accelerometers – Low and Large Scale– Strain Gauges– Temperature Transducer– Condenser Microphone
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Previous DesignsPrevious DesignsDesign #1
(Milled)Design # 2
(Milled and welded 2 parts)
Design #3(Milled and welded)
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Structural DesignStructural Design• Located in ESPA
port opposite a satellite
• Module enclosed• Assembly
Dimensions:– L = 10 in– t wall/shelf = 0.25 in– OD = 13.5 in
• Weight:– ELM = 30.7 lbs
• Battery ≈ 1.23 lbs• Computer < 1 lbs
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Structural DesignStructural Design
• Basic parts: – Base Plate, Shelf Assembly, Tube and
Cap
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• Al 6061 plate 0.25” thick• Base Plate: Dia. = 16.5”• Cap: Dia. = 13.5”• Bolts to Tube and Shelf Assembly
StructuralStructural Design: Base Plate Design: Base Plate & Cap& Cap
Base Plate Cap
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Structural Design: Shelf Structural Design: Shelf AssemblyAssembly
• Holds computer, battery, and accelerometers• Al 6061 sheets 0.25” thick• 12 Corner brackets, #8-32 socket head cap screw, nuts• Milled to achieve accuracy in shape, wire pass
through, bolt holes
Shelf Shelf Assembly
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StructuralStructural Design: TubeDesign: Tube
• Al 6061 Extruded Tube
• Turned to 13.5” OD, 12.5” and 13” ID
• 20X #10-32 tapped holes for helicoil inserts on 13” B.C.
• Notched to allow shelf assembly to insert
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Structural Design: Battery Structural Design: Battery BracketBracketStructural Design: Battery Structural Design: Battery BracketBracket
• Clamps battery with thermal conductive vibration insulation foam to shelf assembly
• Bent from 5051 Aluminum• Wire pass at one end
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• 2” x 2” 90˚ 6061 Al extrusion
• Bracket Dimensions– 2” x 1.5” x 0.5”– Thickness =
0.25”– #8-32 through
holes
Structural Design: Corner Structural Design: Corner and Strain Beam Bracketsand Strain Beam Brackets
Corner Bracket Strain Beam Bracket
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Environmental Variable Environmental Variable Measuring DevicesMeasuring Devices
Prototype• Accelerometer – Low and Large Scale• Single Strain Gauge • Temperature Transducer
Options on Final – Decided By Customer• Accelerometer – Low and Large Scale• Condenser Microphone• Rosette Strain Gauge• Temperature Transducer
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Measurement Device Measurement Device RequirementsRequirements
• ESPA can be used on the Delta IV- Medium and the Atlas V 400
• Flight Environment data from these launch vehicles were used to establish requirements for the ELM measurement devices
Delta IV-M
Atlas V 400
Sh
ock
(Max)
Peak Accel. (g) 5000 4500
Sin
usoid
al V
ibration
s
Axial (Hz) 100 100
Axial (g) 1.27 1
Lateral (Hz) 100 100
Lateral (g) 0.7 0.8
Tem
p
(Max)
(˚C) 100 100
SP
L
(Max)
1/3 Octave Band (dB) 130 125
Freq. (Hz) 131 200
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Tri-Axial AccelerometersTri-Axial Accelerometers
Large RangeLarge Range• Measures up to 500g• Measures any sudden
peaks
Low RangeLow Range• Measures up to 50g• Resolution is much
higher for subtle events
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• Vishay rosette strain gauge
• Mounted outside of ELM on ESPA or Secondary Payload
Strain Gauges - Flight ELMStrain Gauges - Flight ELM
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• Vishay single strain gauges• Mounted on two cantilevered
beams: 20 and 50 Hz
Strain Gauges - Prototype Strain Gauges - Prototype ELMELM
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Temperature TransducerTemperature TransducerTemperature TransducerTemperature Transducer
• Analog Devices AD590MF
• 2-Terminal Integrated Circuit Temperature Transducer
• Mounted on Computer for Prototype
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Condenser MicrophonesCondenser Microphones
Condenser MicrophonePCB 377B10
Pre-AmplifierPCB 426B03
• Optional device for the final ELM
• Requires vibration isolation
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ElectronicsElectronicsElectronicsElectronics• Electronic
Components:– Power Supply– Interface Board– Data Acquisition
and Storage
• Collaboration with Santa Clara University to develop electronics
• Telemetry system is mission specific
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Battery: Nickel Metal Battery: Nickel Metal HydrideHydride
Battery: Nickel Metal Battery: Nickel Metal HydrideHydride
• Chosen due to its strong aerospace history
• Li-ion known to be unstable • Battery Specs:
– 10.8 V and 4200 mAh
• Mounted to shelving with aluminum bracket and thermal conductive foam
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Structural IntegrityStructural Integrity
• ELM must maintain a natural frequency above 500 Hz
• ELM must remain functional under predicted loads:– 20 Hz to 2 kHz– 10 g’s lateral/axial– 14.1 g’s vectored
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Finite Element Analysis:Finite Element Analysis:Natural FrequencyNatural Frequency
• Finite Element Analysis used to estimate the natural frequency
• First mode of empty housing was approximately 1100 Hz
• Actual natural frequency expected to be lower
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Bolt AnalysisBolt Analysis
• Shear of the bolt – F=0.577πd2Sut(nb/4)
• 20 bolts / 30lbs total weight / 14.1
vectored sum g level/ FOS 158• Maintain stiffness
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Vibration TestingVibration Testing
• Vibration tests were completed to verify structural integrity
• Random vibrations of 20 Hz to 2 kHz were applied to 3 axes
• Sine sweeps were performed before and after each random test as a diagnostic
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Vibration TestingVibration Testing• 3 NTS Accelerometers
– Between ELM Accelerometers– On Battery Bracket– Near the Computer
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Vibration Testing-NTS Vibration Testing-NTS ResultsResults
• Majority of natural frequencies above 700 Hz
• No significant changes in natural frequency between pre and post sine sweeps
• Battery bracket saw natural frequencies below 500 Hz.– Not a concern because better material and
different manufacturing will be used for flight.
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Vibration Testing- ELM Vibration Testing- ELM ResultsResults
• Acceleration data verified
• Resonance location match / magnitude incorrect
• Sample rate 900 Hz
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Recommended Recommended ImprovementsImprovements
• Increased sample rate to twice expected frequency
• Permanent fasteners• Vibration isolation mount for
microphone• Consider upgrading structural material
to 7050 Aluminum• Decrease overall size• Machine from one part:
– Base plate and tube– Shelf assembly
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Questions?Questions?