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

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

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

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

Previous DesignsPrevious DesignsDesign #1

(Milled)Design # 2

(Milled and welded 2 parts)

Design #3(Milled and welded)

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

Structural DesignStructural Design

• Basic parts: – Base Plate, Shelf Assembly, Tube and

Cap

• 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

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

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

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

• 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

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

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

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

• Vishay rosette strain gauge

• Mounted outside of ELM on ESPA or Secondary Payload

Strain Gauges - Flight ELMStrain Gauges - Flight ELM

• Vishay single strain gauges• Mounted on two cantilevered

beams: 20 and 50 Hz

Strain Gauges - Prototype Strain Gauges - Prototype ELMELM

Temperature TransducerTemperature TransducerTemperature TransducerTemperature Transducer

• Analog Devices AD590MF

• 2-Terminal Integrated Circuit Temperature Transducer

• Mounted on Computer for Prototype

Condenser MicrophonesCondenser Microphones

Condenser MicrophonePCB 377B10

Pre-AmplifierPCB 426B03

• Optional device for the final ELM

• Requires vibration isolation

ElectronicsElectronicsElectronicsElectronics• Electronic

Components:– Power Supply– Interface Board– Data Acquisition

and Storage

• Collaboration with Santa Clara University to develop electronics

• Telemetry system is mission specific

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

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

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

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

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

Vibration TestingVibration Testing• 3 NTS Accelerometers

– Between ELM Accelerometers– On Battery Bracket– Near the Computer

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.

Vibration Testing- ELM Vibration Testing- ELM ResultsResults

• Acceleration data verified

• Resonance location match / magnitude incorrect

• Sample rate 900 Hz

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

Questions?Questions?