ELM: ESPA Launch Load Module Department of Mechanical & Industrial Engineering Northeastern University Boston, MA 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 University Santa Clara, CA

ESPA: EELV Secondary Payload Adapter 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: ESPA 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 Requirements To 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 Designs Design #1 (Milled) Design # 2 (Milled and welded 2 parts) Design #3 (Milled and welded)

Structural 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 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 Structural Design: Base Plate & Cap Base Plate Cap

Structural Design: Shelf Assembly 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 ShelfShelf Assembly

Structural Design: 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 Bracket Clamps battery with thermal conductive vibration insulation foam to shelf assembly Bent from 5051 Aluminum Wire pass at one end 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 and Strain Beam Brackets Corner Bracket Strain Beam Bracket

Environmental Variable Measuring 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 Requirements 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 Shock(Max) Peak Accel. (g) Sinusoidal Vibrations Axial (Hz)100 Axial (g)1.271 Lateral (Hz)100 Lateral (g) Temp (Max) (˚C)100 SPL (Max) 1/3 Octave Band (dB) Freq. (Hz)131200

Tri-Axial Accelerometers Large Range Measures up to 500g Measures any sudden peaks Low 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 ELM

Vishay single strain gauges Mounted on two cantilevered beams: 20 and 50 Hz Strain Gauges - Prototype ELM

Temperature Transducer Analog Devices AD590MF 2-Terminal Integrated Circuit Temperature Transducer Mounted on Computer for Prototype Analog Devices AD590MF 2-Terminal Integrated Circuit Temperature Transducer Mounted on Computer for Prototype

Condenser Microphones Condenser Microphone PCB 377B10 Pre-Amplifier PCB 426B03 Optional device for the final ELM Requires vibration isolation

ElectronicsElectronics Electronic Components: – Power Supply – Interface Board – Data Acquisition and Storage Collaboration with Santa Clara University to develop electronics Telemetry system is mission specific 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 Hydride 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 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 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: Natural 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 Analysis Shear of the bolt – F=0.577πd 2 S ut (n b /4) 20 bolts / 30lbs total weight / 14.1 vectored sum g level/ FOS 158 Maintain stiffness

Vibration 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 Testing 3 NTS Accelerometers – Between ELM Accelerometers – On Battery Bracket – Near the Computer 3 NTS Accelerometers – Between ELM Accelerometers – On Battery Bracket – Near the Computer

Vibration Testing-NTS Results 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 Results Acceleration data verified Resonance location match / magnitude incorrect Sample rate 900 Hz Acceleration data verified Resonance location match / magnitude incorrect Sample rate 900 Hz

Recommended Improvements 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?