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EHD Pump Critical Design Review
University of Nebraska–Lincoln
NASA Goddard Space Flight Center
December 7, 2012
Mission Overview
Mission Overview
• Mission Overview
• Organizational Chart
• Theory and Concepts
• Concept of Operations
• Expected Results
Mission Overview
• Goal statement: The total mission goal is to implement known
and experimental EHD technology in thin-film evaporation
techniques for the purposes of two-phase flow in microgravity.
To verify success of the experiment, we will require data on
fluid flow and temperature from multiple sources.
• We expect high values of thermal transfer coefficients derived
from total heat fluxes on the payload target.
• Results will be used in designs of a similar long-term
experiment that will be held on the ISS. Future applications
include EHD pumps for onboard circuits and microprocessor
integration.
Mission Overview
• Multidiscipline Engineering Collaboration
– GSFC: Experiment Design and Fabrication
– University of Nebraska–Lincoln Aerospace Club:
Experiment Operations/Structure/Subsystems:
• Data Acquisition
• Power Distribution
• Flight Operations
• Structure
• Program Objectives
– EHD Thin Film Evaporation micro-gravity data in
support of ISS Microgravity Experiment Science Review
Micro-Scale EHD • Science Goals: ISS Experiment Preliminary
– Effects of gravity of interaction of flow
fields and electrical fields with and without
phase change
– Effects of gravity of electrical charge
generation in meso- and micro-scale
– Effects of gravity on electrically driven film
boiling
• Applications:
– EHD pumps for on-board processors
– EHD pumps for micro- and nano-scales
– High heat flux thermal control
– Multi-functional Plates
Micro-Scale EHD
• The effects of gravity on the
interaction of electric fields and
flow fields in the presence of
phase change in small and large
scales.
• The effects of gravity on the net
electrically generated two-phase
flow rate in small and large
scales.
• The effects of gravity on
electrically driven film boiling
(includes extreme heat fluxes).
• Convective boiling heat transfer
coefficient in low mass flux
levels in the absence of gravity.
Theories of Operation
• Electrophoretic: charge generation by electro-chemical reaction
• Liquid Pumping
• Function of electric field, temperature & fluid quality
• Di-electrophoretic: take advantage of permittivity gradients (e.g,
two phase flow)
• Phase & Fluid Management
• Thin Film Evaporation
• Electro-striction: Compressible Flow
EHD Force Components
EHD Electrophoretic Force Generation
Asymmetric Geometry leads to higher pressure head: configuration is
impractical for spacecraft applications
EHD Electrophoretic Force
• Coulomb (electrophoretic) force generated by:
• Apply discrete electric field to dielectric fluid using
asymmetric electrode geometry
• Electrolytes in fluid subject to dissociation-recombination
reaction that favors dissociation in presence of electric field
• Attraction of hetero-charges to electrode generates flow
• Electrodes in wall; less asymmetry - lower pressure head
generated
FLOW
L1
L3 L2 L4
Concept of Operations
t ≈ 15 min
Splash Down
t ≈ 1.6 min
Altitude: 91 km
Power on EHD Pump
-G switch triggered
-All systems on
-Begin data collection
t = 0 min
Apogee
t ≈ 2.8 min
Altitude: ≈115 km
End of Orion Burn
t ≈ 0.6 min
Altitude: 52 km
Power to resistors
t ≈ 5 min
End Experiment
Altitude
t ≈ 5.5 min
Chute Deploys
Concept of Operations
Event Action
Launch G switch triggered → Arduino powers on
End of Orion Burn • Send power to platinum resistors
• Data logger and sensors active, collecting data
Time ≈ 1.6 min Power to EHD Pump experiment
End Experiment
• EHD Pump and resistors powered off
• Data logging stopped and sensors inactive
• Arduino in idle state
High-Range Accelerometer Data
High-Range Radial and Tangential Acceleration
Expected Results
• For each of the RTDs in the experiment, the
voltage will be stored and used to calculate the
heat transfer coefficient of the experiment.
• We are measuring the two phase heat transfer
coefficients for thin film liquid boiling using
EHD conduction technique. We expect to see
heat transfer coefficients above 150 W/cm2 · K
Design Description
Changes Since PDR
• Battery Container
– PDR: Batteries lay on their sides, arrayed around the
center
– CDR: Batteries stand up, arrayed circularly
Changes Since PDR
• Dampening
– PDR: Piston-Cylinder
with internal secondary
dampening
– CDR: Piston-Cylinder
with external vibration
dampening, alternative
material
Changes Since PDR
• Double Containment for
Fluids
– To counter the possibility of the
dielectric fluid leaking, the hose
connecting the experiment and
fluid reservoir will have a
secondary containment
implemented.
Changes Since PDR
• Si Wafer Support
– PDR: 0.5 inch Sorbothane
pad for vibrational
dampening
– CDR: Rapid prototyped
plate with access for RTDs
De-Scopes and Off-Ramps
• Scope has not changed since PDR
• No off-ramps
– No “high risk” components–thorough testing with
GSFC to verify
Mechanical Design Overview
Physical Models
Battery Array
Electronics and Fluids System
Experiment System
Battery Array
• 24 NiMH batteries
• Two 9-volt batteries
• Custom-made battery housing
– Rapid prototyped
• Connects NiMH batteries in
series
Electronics and Fluids Systems
Fluid Reservoir
Power Supply
Arduino, Sensors, OpenLog
Z-axis accelerometer
Experiment Sensors Power
Supply
G-Switch
Experiment System
• Two stages of dampening
– Piston-Cylinder System
– Internal Vibration System
• Experiment housing
Stage 1 Dampening
• Experiment system is
constrained on both sides
by the Piston-Cylinder
system
• The pistons remains static,
allowing the experiment
system to move axially
• Dampening materials
absorb most of the
impulses in all directions
Stage 2 Dampening
• Primary purpose is to absorb
vibrations
– Absorbs most of the
vibrations
• Constrains the experiment
housing in all directions
with dampening material
• Side tabs keep experiment
aligned axially
Experiment Housing
• Contains the EHD pump and
sensors
• Two electronic ports
– 25-pin connector for thermal
resistors located underneath
the EHD
– Power connector for EHD
• Two fluid ports for inflow
and outflow
• Vacuum-sealed
Electrical Design Elements
• Control subsystem
– Power
– Controls
– Canister sensors
• Experiment subsystem
– Power
– Heater
– EHD pump
– Sensors
Changes Since PDR
• Finalized canister sensor models
• Changed activation method to 1SYS.1
• Addition of external ADC
• Replace multiplexor with protoshield
Controls
• Power: rechargeable batteries
– Tenergy 9V NiMH 250mAh
• x2, in parallel
• Three PCB assemblies
– Arduino, sensors, data
– Z-axis accelerometer
– G-Switch
Controls Block Diagram
Arduino Assembly
• Arduino Mega 2560 R3
– Manages power distribution to experiment
– Interface to all sensors
– Logs data to storage
– Powered on before flight: 1SYS.1
• Protoshield
– “Breadboard” stacked on top of Arduino
– Canister sensors, OpenLog are soldered on
Protoshield
• OpenLog
– Connected to Arduino
• Serial connection @ 57.6 Kbps
– Flash storage: 1GB microSD
– Logs any data received from serial
• G-switch
– Signals launch
– Determines when timed events begin
Protoshield
• XY-axis accelerometers
– Analog Devices Inc.
– High-range model: AD22284-A-R2
• ± 37g
– Low-range model: ADXL203CE
• ± 1.7g
– Both sensors on one PCB
– Six lines
• High/low X analog outputs
• High/low Y analog outputs
• VCC (+5V), GND
Protoshield
• Pressure sensor
– Honeywell Sensing and Control
– ASDX015A24R
– 0 to 15 psi range
– Three lines
• Analog output
• VCC (+5V), GND
Protoshield
• Temperature sensor
– National Semiconductor
– LM50CIM3/NOPB
– Range of -40° to 120°C
– Three lines
• Analog output
• VCC (+5V), GND
Z-Accelerometer Assembly
• Analog Devices Inc.
• High-range model: AD22279-A-R2
– ± 35g
• Low-range model: ADXL103CE
– ± 1.7g
• Both sensors on one PCB
• Four lines
– High/low Z analog outputs
– VCC (+5V), GND
Experiment Subsystem
• Power
• Heater
• EHD Pump
• Sensors
• External ADC
Experiment Block Diagram
Experiment Subsystem
• Power
– Batteries
• Tenergy 1V NiMh 10C High Drain
• Rechargeable 2/3A 1600mAh
• x24, in series
– Experiment power supply
• Pico Electronics Series VV, part 48VV3
• Input: 15 to 48V
• Output: 450 to 3000V, max 2.667mA
– Wheatstone power supply: TBD
• Must provide highly stable, constant voltage
Experiment Subsystem
• Resistive heater
– Platinum resistors
– Heat silicon wafer
• EHD Pump
– Provided by GSFC
– 2000V at < 1mA
• Sensors
– Provided by GSFC – models TBA
– Pressure sensor
– Flow meter
Experiment Subsystem
• Sensors
– Temperature
• x20 RTD sensors
– Very accurate nominal resistance
• Individual Wheatstone bridge circuit per sensor
Experiment Subsystem
• External ADC
– Recent development: Arduino ADC is undesirable
• Questionable noise levels
– Simple on-chip ADC
– Additionally from multiplexor?
– Long signal wire travel
• Low resolution: 8-bit
– 1024 values
– 1V reference: ~ 1mV steps
Experiment Subsystem
• External ADC
– Proposed model: Texas Instruments ADS1258-EP
• 48-pin IC
• 24-bit resolution
– 1.68 million values
– 5V reference: 298 nV steps
• 16-channel
– Eliminates the need for external multiplexor
– 23.7 kSPS per channel
– All channels sampled in 700 μs – theoretical 1.4kHz sample rate
• Low-noise emphasis
• Digital communication with Arduino via SPI
Experiment Subsystem
• External ADC
– Implementation
• Noise minimization
– Converting on-PCB with Wheatstone bridges
– Physically relocate near experiment
» Only digital signals to Arduino travel significant distances
• May use multiple chips depending on sensor quantity
– Compact size: 7.2 mm square
– Still less space compared to mux
Software Design Elements
• Written in C for Arduino
– Augmented using open-source libraries
• TimeAlarm: event scheduling
• Serial communication
• Major tasks
– Time-based power distribution
• Output power-on and -off signals at certain flight times
• Controls experiment, heater
Software Design Elements
• Major tasks
– Read sensor data
• From experiment, canister
– Log data to storage
• Output to OpenLog over Serial
Software Flowchart
Time-Based Events
• Using TimeAlarm library
– Pseudo-realtime event scheduling
– One-second precision
• Events at certain times
– Power on resistive heater
– Power on experiment
– Power off experiment and resistive heater
Prototyping/Analysis
Battery Case FEA
• Solidworks Finite
Element Analysis
on Battery Case
• Material: ABS
(acrylonitrile
butadiene styrene)
Property Value Units
Young’s Modulus 2000 MPa
Poisson’s Ratio 0.394 N/A
Shear Modulus 318.9 MPa
Tensile Strength 30 MPa
Density 1020 kg/m3
Fluid/Electronics Base FEA
• Solidworks Finite
Element Analysis
on load carrying
support
• Material: High
Viscosity
Polycarbonate
Plastic
Property Value Units
Young’s Modulus 2320 MPa
Poisson’s Ratio 0.3912 N/A
Shear Modulus 829.1 MPa
Tensile Strength 62.7 MPa
Density 1190 kg/m3
Piston FEA
• Solidworks FEA
on primary load
carrying element
in dampening
system
• Material:
Aluminum 6061
Alloy
Property Value Units
Young’s Modulus 69 GPa
Poisson’s Ratio 0.33 N/A
Shear Modulus 26 GPa
Tensile Strength 124.1 MPa
Density 2700 kg/m3
Manufacturing Plan
Mechanical Elements
• Battery Canister
– 3D printed here at the University of Nebraska
• Experiment
– GSFC has designed, and plans to manufacture the
actual experiment
– Dampening System and Canister
• Discussions are in progress for GSFC to manufacture the
experiment canister, as well as the dampening system
Mechanical Elements
• Experiment
– Fluid Reservoir
• GSFC plans to manufacture this
• Materials
– 3D printed parts will be printed out of industry
standard ABS plastic
– All custom manufactured metal components will
be made of industry standard 6061 aluminum
Mechanical Elements
• Materials
– Tubing Material has yet to be decided on
– Sorbothane will be used as a dampening material
in our system
• Construction
– All parts put together in final assembly in-house at
the University of Nebraska
Mechanical Manufacturing Plan
Date Event
1/23/2013 Purchase materials and components
1/23/2013 3D print necessary parts
1/27/2013 Begin component machining
1/30/2013 Begin experiment section construction
2/10/2013 Begin experiment subsystem testing
Electrical Elements
• Yet to be manufactured
– Sensor PCB
• Solder sensor boards to single PCB
• Fairly simple: one revision expected
– Wheatstone bridge, ADC circuit
• May require 2 or 3 revisions
• Yet to be procured
– Batteries for controls and experiment
– Experiment, Wheatstone power supply
Electrical Manufacturing Plan
Date Event
1/25/2013 Purchase remaining components
1/30/2013 Print finalized circuit boards
2/5/2013 Begin Tier 2 construction
2/10/2013 Begin experiment subsystem testing
Software Elements
• Simple proof-of-concept completed
– Log 20 thermistors to storage
• To be completed:
– Logging of additional sensors
– Time-based events
• No inter-block dependencies
Software Manufacturing Plan
Date Event
12/21/2012 Complete first code iteration
1/4/2013 Test functionality with all sensors
2/8/2013 Verify reliable event timing
2/10/2013 Begin experiment subsystem testing
2/17/2013 Finalize code
Testing Plan
Mechanical Testing
• Whole assembly will be manufactured and
assembled, including the canister
• Will be tested at GSFC when put together
• Impact testing to simulate rocket launch forces
and axial force on EHD experiment
• Vibration simulation testing will test energy
transfer to EHD experiment
Sorbothane Test Procedure
• Ran In House tests on Sorbothane’s ability to absorb force
• Track angled at 0.5 degrees from table surface
• Frictionless cart (mass: 0.251 kg) released 33.5 cm up
ramp
• Force sensor at bottom of ramp
• Control experiment done without sorbothane, then a
sorbothane pad was placed as a buffer in front of the force
sensor
Sorbothane Test Results
Run # Time (s) Max force (N) Mean Force (N) Impulse (N*s)
1 0.00515 46.21 24.21 0.13
2 0.00495 44.62 21.91 0.12
3 0.00510 42.60 24.10 0.13
4 0.00520 40.68 23.14 0.12
5 0.00530 40.25 22.91 0.12
Run # Time (s) Max force (N) Mean Force (N) Impulse (N*s)
1 0.01020 17.58 9.57 0.10
2 0.01020 16.82 9.47 0.10
3 0.01090 16.72 9.01 0.10
4 0.01069 17.21 9.18 0.10
5 0.01140 14.62 7.92 0.09
With Sorbothane
Without Sorbothane
• Test ran with 1 kg mass added to cart with Sorbothane
buffer in place
– Force: 35.35 N
Without Sorbothane
With Sorbothane
Electrical Testing
• Ensure no current without WFF
• Verify experiment PSU signaling
– Interaction with software
• Verify sufficient battery life for experiment
and controls
– Much higher than time of flight and pre-, post-
flight buffer
• Verify sensor operation and data validity
• Testing planned for winter break
Software Testing
• Ensure time-based events fire at correct time
– Especially Arduino-to-experiment PSU signaling
• Test G-switch polling
• Verify that minimum sampling rate is
maintained
– Prototype software: ~600 Hz
• Testing planned for winter break
Risks
Power Risk Matrix
• EHD pump does not operate if –
– Risk 1: EHD power supply fails
– Risk 2: EHD battery is discharged before launch
Risk 1, 2
Possibility
Conse
quen
ce
Controls Risk Matrix
– Risk 1: Experiment failure if Arduino does not signal EHD PSU at appropriate time
– Risk 2: Loss of data precision if the Arduino cannot sample sensors rapidly enough
– Risk 3: Unable to log all data if multiplexor introduces compatibility issues with
sensors
– Risk 4: Inaccurate data if vibrations cause loose connections
– Risk 5: Erroneous data if programming faults exist
Risk 1, 3
Risk 5
Risk 4
Risk 2
Possibility
Conse
quen
ce
Experiment Risk Matrix
– Risk 1: Entire experiment fails because silicon wafer fractures
– Risk 2: Working fluid leakage
– Risk 3: Loss of working fluid due to container integrity failure,
reservoir integrity failure, or seal failure.
– Risk 4: Experiment loses power due to electrical connection
malfunctions.
Risk 1
Risk 4 Risk 2
Risk 3
Possibility
Conse
quen
ce
Structure Risk Matrix
– Risk 1: Experiment fails if structure platforms fail to support
components
– Risk 2: Excessive vibration along with dampening failure causes
experiment to lose structural integrity.
– Risk 3: Dampening material acts unpredictably, causing greater
impulses to translate through.
Risk 1
Risk 2, 3
Possibility
Conse
quen
ce
User Guide Compliance
User Guide Compliance
• Mass
– Payload mass: 10.09 lbs
– Total mass: 17 lbs
• Center of Gravity
– X = -0.016 in
– Y = -0.027 in
– Z = 4.93 in
User Guide Compliance
• Rechargeable NiHM batteries
– Tenergy 2/3 A, 1600 mAh (x24)
– Tenergy 9V, 250 mAh (x2)
User Guide Compliance
• 1.SYS.1 activations
system by WFF
– Arduino powered on by
WFF at T-2 min
– WFF will have full control
over control power
– Once controls are powered
off, so will the entire
experiment
Project Management Plan
Schedule Date Event
1/18/2013 Final Down Select - Flights Awarded Legend
1/18/2013 Stage 2 Funding Proposal submitted to NASA NE Project Milestones
1/23/2013 Order Components and Construction Materials COSGC Expectations
1/25/2013 Begin Payload Subsystem Construction
1/25/2013 Online Progress Report 3 Due
2/15/2013 Individual Subsystems Testing Reports Due
2/25/2013 Start Subsystems Integration
3/12/2013 Online Progress Report 4 Due
3/29/2013 Payload Subsystem Integration and Testing Report Due
4/2/2013 Begin Full Payload Sctructural Test (Vibration, Vacuum, etc)
4/15/2013 RockSat Payload Canister sent to customers
4/26/2013 First Full Mission Simulation Test Report Due
6/3/2013 Launch Readiness Review Presentations
6/12/2013 Travel to Wallops Flight Facility, 1st Group
6/18/2013 Travel to Wallops Flight Facility, 2nd Group
6/14-18/2013 Integration/Vibration at Wallops
6/20/2013 Launch Day
Monetary Budget Section Part Material Material Subtotal (USD)
Manufacturing Subtotal
(USD)
Experiment 2x Dampening base plate Aluminum 33.26 150
2x Inner dampening plate Aluminum 52.26 275
Experiment housing shell Aluminum 45.68 350
2x Experiment housing plate Aluminum 66.52 240
Computer/resivior mounting plate Makrolon 27.89 65
2x Stage 1 Dampening pads Sorbothane 91.26 0
2x stage 2 dampening pads Sorbothane 68.17 0
Miscellaneoud Dampening pads Sorbothane 52.78 0
2x Pipe elbows Aluminium 35.46 0
Hardware
16x Nuts Steel 11.36 0
4x Threaded rod Steel 6.74 0
30x SHCS Steel 28.71 0
2x Copper O-Ring Copper 30.42 0
Printed Parts
2x Piston Wall ABS Plastic 56.92 210
Lower Battery Plate ABS Plastic 42.13 250
Upper Battery Plate ABS Plastic 38.75 250
Subtotal 688.31 1790
Total Cost 2478.31
Monetary Budget Section Part Quantity Unit Price (USD) Subtotal (USD)
Electrical/Controls Arduino Mega2560 Rev3 1 50.69 50.69
Mux Shield 1 24.95 24.95
Payload Pressure Sensor 1 62.09 62.09
Payload Temperature Sensor 1 1.06 1.06
Payload Low Range Z-Axis Accelerometer 1 18.04 18.04
Payload High Range Z-Axis Accelerometer 1 12.83 12.83
Payload Low Range X&Y-Axis Accelerometer 1 21.71 21.71
Payload High Range X&Y-Axis Accelerometer 1 18.03 18.03
Nickel Tabs 30 0.1 3
Flow meter (donated) 1 0 0
Subtotal 161.71
Tier 2 Reservoir 1 donated 0
Tubes 2 20 40
PCBs 3 10 30
Subtotal 70.00
Power Systems 24x Tenergy 2/3A 1600mAh 24 1.68 40.32
2x Tenergy 9V 250mAh 2 4.19 8.38
Power Supply 1 136.24 136.24
Subtotal 184.94
Grand Total 2894.96
Mass Budget
System Item Mass (g) Quantity Total Item Mass
kg pounds Total Payload Mass
Battery pack 1.2V battery 23 24 0.55 1.22 kg pounds
9V battery 50 2 0.10 0.22 4.58 10.09
Base Plate 116.7 1 0.12 0.26
Top Plate 75.53 1 0.08 0.17
Nickel Tabs 0.22 47 0.01 0.02
Total 0.85 1.88 Center of Gravity
Required
Level 2 Base Plate 150 1 0.15 0.33 cm inches
Reservoir 600 1 0.60 1.32 X 0 ±0.5 0 ±0.5
Power Supply 50 1 0.05 0.11 Y 0 ±0.5 0 ±0.5
Wheatstone 20 1 0.02 0.04 Z 12.688 ±0.5 4.75 ±0.5
Arduino 36 1 0.04 0.08 Current
Mux Shield 36 1 0.04 0.08 X -0.04 -0.016
Accelerometer 20 2 0.04 0.09 Y -0.07 -0.027
Wiring 70 1 0.07 0.15 Z 12.53 4.93
Total 1.00 2.21
Mass Budget
Experiment Item Mass (g) Quantity Total (kg) Total (lbs)
Stage 1 Piston 109.89 2 0.22 0.48
Cylinder 53.07 2 0.11 0.23
Bolt 2.04 8 0.02 0.04
Nut 0.54 8 0.00 0.01
Sorbothane 291.64 2 0.58 1.29
Plate 43.04 2 0.09 0.19
Total 1.02 2.24
Stage 2 Plates 74.64 2 0.15 0.33
Sorbothane 134.71 2 0.27 0.59
Sorbothane Tabs 1.06 4 0.00 0.01
Bolt 10.13 4 0.04 0.09
Nut 2.07 8 0.02 0.04
Total 0.48 1.06
Mass Budget
Experiment Housing Cap 187.84 1 0.19 0.41
Brace 250.8 1 0.25 0.55
Base 231.38 1 0.23 0.51
EHD 120.24 1 0.12 0.27
Thermal sheet 180.73 1 0.18 0.40
Hex screw 0.67 8 0.01 0.01
elbow joint 1.52 2 0.00 0.01
power port 0.56 1 0.00 0.00
pin connector 47.76 1 0.05 0.11
Total 1.03 2.27
Misc Hose 4.57 2 0.01 0.02
nut 1.62 34 0.06 0.12
All-thread 31.73 4 0.13 0.28
middle AT 6.35 1 0.01 0.01
Total 0.20 0.44
Power Budget Device Voltage (V) Current Draw (mA) Time Running (min) mAh
Arduino 9 10 15 2.5
XYZ Accelerometer 5 10 15 2.5
Pressure Sensor 5 5 15 1.25
Temp sensor 5 5 15 1.25
OpenLog 5-3.3 10 15 2.5
MUX Shield 5-3.3 5 15 1.25
Subtotal 11.25
Total Available 500
Device Voltage (V) Current Draw (mA) Time Running (min) mAh
WheatStone Bridge Circuit 5 300 5 25.00
Power Supply 28 3 5 0.25
EHD Components 2000 3 5 0.25
Thermal heaters 28 500 7 58.33
Flow meter 5 10 5 0.83
Subtotal 84.67
Total Available 1600
Questions?