EHD Pump Preliminary Design Review University of Nebraska–Lincoln NASA Goddard Space Flight Center
EHD Pump Preliminary Design Review
University of Nebraska–Lincoln
NASA Goddard Space Flight Center
Mission Overview
Mission Overview
• Mission Overview
• 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
Expected Results
System Overview
System Overview
• Subsystem Definitions
• System-Level Block Diagram
• Critical Interfaces
• System Concept of Operations
• System/Project Level Requirement
Verification Plan
• User Guide Compliance
Subsystem Definitions
• Power
– Provides power for canister’s systems
– Power supply for EHD pump
• Controls
– Switches on and off power to systems
• EHD pump power supply
• Platinum resistive heater
– Receives all sensor data, saves to storage
– Canister/EHD sensors: temperature, pressure,
acceleration
Subsystem Definitions
• Experiment
– EHD pump
– Resistive heater
– Sensors
• 20 temperature probes
• Pressure
• Flow meter
• Structure
– Canister
– Three tiered layout
System-Level Block Diagram
Critical Interfaces
Interface Description Potential Solution
Power/Sensors
The platinum resistors, which
measure various temperatures
on the EHD pump, require a
constant current.
Wheatstone bridges will be used
for each resistor. The temperature
reading will be determined from
the resistor voltage.
Power/Experiment
The EHD pump uses high-
voltage, low-current power of
2000V at <1mA.
NASA GFSC will provide a
custom power supply unit with
coronal covering for the EHD
pump experiment that meets its
requirements.
Experiment/Contr
ols
The experiment will output 23
channels of data to the controls,
each to be logged at 60 Hz or
higher.
Since the Arduino lacks enough
sensor inputs, a multiplexor will
be used to accommodate all
inputs. Data will be sent to an
OpenLog.
Critical Interfaces
Interface Description Potential Solution
EHD/Damping
The EHD pump must be able to
withstand ≥ 25 Gs and impulses
of ≥50Gs during flight
A Sorbothane pad inside of a
piston assembly will provide the
necessary dampening force which
allows the EHD pump to
withstand the 30G’s plus impulse.
The Sorbothane piston, located on
the top and bottom of the EHD
experiment, will act as a buffer
between the rocket and the
experiment.
System Concept of Operations
• Inputs from EHD pump
– 20 temperature sensors
– 2 pressure sensors
– 1 flow meter
• Inputs from general canister sensors
– Accelerometer, pressure, temperature
• Data aggregated at multiplexor
– Not enough inputs on Arduino
– Arduino can select arbitrary sensors
System Concept of Operations
• Arduino collects data from mux
– Collect at least 60 samples/sec from every sensor
– Stored on OpenLog
System Concept of Operations
Flow of data from sensor to storage
System Design
Requirement Verification
Requirement Verification
Method Description
No parts should be allowed to
move freely in the canister. Demonstration
Attempt to physically move the
components. Orient the canister
in various ways and with various
forces.
EHD pump power supply should
receive power only during the
designated times during flight.
Testing
Simulated flights will be carried
out to ensure proper power
delivery timings.
Batteries should provide sufficient
power to components for the flight.
Analysis,
Testing
Estimates will be calculated to
ensure the battery capacities.
Simulated flights will verify the
estimates.
Subsystem Design Power
Power Design
• Payload will be initialized in compliance with
1.SYS.1 activation system.
• Two discrete power systems for:
– Controls and sensors
• NiMH 10.8V, ~2000 mAh
– Arduino requires 7-12V
– Low power for sensor operations
– Platinum RTDs require power for temperature sensing
Power Design
• Two discrete power systems for:
– EHD pump experiment
• NiMH 28V, ~ 2000 mAh
– Safer than LiPo
– Independent power supply
• Activated by Controls – data not important until later in
flight (T+1.6 min)
• Powers EHD pump (high voltage, low current) and
Platinum Resistive Heater (low voltage, high current)
Power Block Diagram
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
Co
nse
qu
ence
Subsystem Design Controls
Controls Design
• Powers on when RBF and G Switch are
thrown
• Activates subsystem power during flight
– EHD power supply
• Reads sensor values
– EHD sensors
– Canister sensors
• Logs sensor data to storage
Controls Block Diagram
Controls Overview
• Arduino Mega 2560 R3
– ATmega2560 @ 16MHz
– Input: ~10 V
– 54 Digital I/O
– 16 Analog Inputs
– Shield expandability
• Use multiplexor shield to add more analog inputs
– Programmable using C
Controls Design
• OpenLog
– Simple data logger
• Serial connection up to 115 Kbps
• “Dumb sink” for text data
– microSD storage
• 1GB card
• FAT16, FAT32
– 3.3V @ ~4mA
Controls Design
• Canister/System Sensors
– Models TBD
– Analog: Pressure, Temperature
– Digital: XYZ - accelerometer
– Logged at ≥ 60Hz
Microcontroller Trade Study
Arduino Mega ZTEK USB FPGA
Cost 9 3
Availability 10 6
Community 10 5
Speed 7 10
Programmability 9 5
I/O Count 8 10
Power Usage 10 6
Average 9 6.4
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 Risk 3
Risk 5
Risk 4
Risk 2
Possibility
Co
nse
qu
ence
Subsystem Design Experiment
Experiment Design
• Made out of silicon
– Diameter of 6 inches
– Thickness is 0.1 inch
• EHD components are etched
onto the silicon disc
– 20 platinum RTDs
• Designed, fabricated at GSFC
Advanced Manufacturing
Branch
– Approx. fab time of 3
months
Experiment Container
Experiment Container • Machined from aluminum
• Outer diameter: 6.5 in
• Inner diameter: 6 in
• Base thickness: 0.25 in
• Height: 1.25 in
• Sorbothane pad under Si wafer
– Thickness: 0.5 in
• Fluid ports
– Diameter: 0.125 in
– One input, one output
• One 4-pin power connector for EHD components and resistive heaters
• One 24-pin data connector for sensors
Experiment Working Fluid
• 100 grams total working fluid
• Used for thin-film evaporation
• Pressurized to 1 atm (14.7 psi)
• Possibilities:
HCFC-123 HFE-7100
Density at 25°C 1.463 g/cm3 1.5 g/cm3
Boiling point at 1 atm 27.85°C 61°C
Thermal conductivity at 25°C 0.081 W/m·K 0.061 W/m·K
Autoignition temperature 770°C 405°C
Working Fluid Reservoir
• Total volume: 148 mL
• Height: 2 in
• Radius: 1.2 in
• One input, one output fluid port
• Fabricated at GSFC Advanced Manufacturing Branch
• Aluminum plumbing system
– Inner diameter: 0.125 in
– Outer diameter: 0.25 in
– Total length: 1.5 ft
• Double containment considered, but is not necessary
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
– Risk 4: Loss of working fluid due to reservoir integrity failure
– Risk 5: Loss of working fluid due to seal failures
Risk 1
Risk 3 Risk 2, 4, 5
Possibility
Co
nse
qu
ence
Subsystem Design Structure
Structure Design
• Piston Cylinder Shock Absorber
– A Sorbothane buffer absorbs more G-force than
most standard buffer materials, as well as transmits
less frequency effects.
– Mounted on 4 all threads traveling through
canister. This was chosen over a single mount in
the center for stability and strength.
– Aluminum was chosen for its light weight and high
strength.
Piston Cylinder
• Aluminum Plate attached to spacer
bolts
• High strength Sorbothane compatible
glue attaches a 1 inch Sorbothane sheet
to piston plate.
• Experiment sits on top of Sorbothane
sheet with aluminum piston cylinder
extending down covering the
Sorbothane sheet
• The bottom piston plate is
dimensioned to allow clearance in all
directions from piston cylinder of
experiment.
Piston Cylinder
• Assembly is repeated for top and bottom of experiment
• The EHD silicon plate, which is the experiment, will be
glued directly to this inner Sorbothane sheet.
• To close the experiment there is an aluminum cap.
• Glued to this cap is another 1-inch sheet of Sorbothane
• On top of this Sorbothane sheet, is another aluminum plate,
attached using glue.
• This top aluminum plate is exactly the same as the bottom
plate.
• This is mounted to the space bolts in the same fashion.
Structure Trade Study Sorbothane comparison
Structure Risk Matrix
– Risk 1: Experiment fails if structure platforms fail to support
components
– Risk 2: Experiment canister collapses downwards if steel rods
experience excessive vibration
– Risk 3: Uneven distribution of load and potential shear stress,
fracture if inconsistencies in Sorbothane manufacture exist
Risk 1, 3
Risk 2
Possibility
Co
nse
qu
ence
Prototyping Plan
Prototyping Plan
Subsystem Risk/Concern Action
Power Supply
Terminal leads in battery pack
may fail under load.
Test batteries and terminals under
various physical loads.
Internal battery failure causes a
lack of necessary voltage and
current.
Sufficiently test chosen batteries to
verify their ability to consistently
operate under load.
Controls
The Arduino may not have
enough processing power to
sample the sensors at 60 Hz or
greater.
Test the Arduino with 20
thermocouple sensors to verify its
abilities. If it cannot meet the
requirements, then investigate the
faster Arduino Due.
Structure and
Experiment Support
Support system does not meet
dampening requirements for the
experiment and silicon disk.
Simulate launch and flight loads with
a disk similar in properties to the
silicon disk.
Project Management Plan
User’s Guide Compliance
• Rough Order of Magnitude Mass Estimate
– Roughly 11 kg total
– Won’t know specific component masses until their
receipt
• Center of Gravity
– The experiment and battery arrangement will have a
horizontal center of mass in center o the canister.
– Arranging the computers and fluid reservoir correctly on
the middle plate to achieve the same center of mass
horizontally should not be too difficult once we get
designs for everything.
User’s Guide Compliance
• Center of Gravity
– Vertically, the plates can be arranged the proper height and
distance from each other to achieve a center of mass in the
middle of the canister.
– Having the batteries on top, and the experiment on the
bottom will make the design much more balanced and
easier to arrange properly.
• High voltage used by EHD experiment
– From EHD power supply
– Handled by GSFC
– Using coronal coating
• Not using any ports
Organizational Chart
Organizational Chart
• Power
– Electrical
• Controls
– Electrical, Software
• Experiment
– Mechanical, Structural, Thermal, Electrical,
Software
• Structural
– Mechanical, Structural, Thermal
Schedule
Date Event
8/12/12 Stage 1 Funding proposal submitted to NASA NE
9/17/12 IFF due to COSGC
9/20/12 Project proposal submitted to GSFC
9/22/12 GSFC-UNL collaboration established
10/5/12 Conceptual Design Review Due
10/12/12 CoDR Presentation
10/17/12 Online Progress Report 1 Due
10/17/12 $1000 Earnest Deposit Due
10/26/12 Preliminary Design Review Due
11/2/12 PDR Presentation
11/1-14/2012 EHD Silicon Wafer Design Finalized
11/6/12 Component Trade Studies
11/8/12 Finalized Component Selection
11/9/12 Online Progress Report 2 Due
11/12/12 Begin Controls Subsystem Testing
11/16-30/2012 Critical Design Review Due
11/30/12 CDR Presentation
1/18/13 Final Down Select - Flights Awarded
1/18/13 Stage 2 Funding Proposal submitted to NASA NE
1/23/13 Order Components and Construction Materials
1/25/13 Begin Payload Subsystem Construction
1/25/13 Online Progress Report 3 Due
2/15/13 Individual Subsystems Testing Reports Due
2/25/13 Start Subsystems Integration
Legend
Project Milestones
COSGC Expectations
Schedule
Date Event
3/12/13 Online Progress Report 4 Due
3/29/13 Payload Subsystem Integration and Testing Report Due
4/2/13 Begin Full Payload Structural Test (Vibration, Vacuum, etc)
4/15/13 RockSat Payload Canister sent to customers
4/26/13 First Full Mission Simulation Test Report Due
6/3/13 Launch Readiness Review Presentations
6/12/13 Travel to Wallops Flight Facility, 1st Group
6/18/13 Travel to Wallops Flight Facility, 2nd Group
6/14-18/2013 Integration/Vibration at Wallops
6/20/13 Launch Day
Legend
Project Milestones
COSGC Expectations
WBS
Power Control Experiment Structure
• Choose and order
specific batteries
• Assemble battery array
• Verify proper voltage
and current output
• Test battery array under
load: duration, output
• Choose sensor models
• Order components
• Assemble and wire
Arduino controller
• Test data acquisition
• Program control and
sensor capabilities
• Work with GSFC to
ensure design work
proceeds as planned
• Integrate experiment
with structure
• Build/receive canister
• Build support structures
into the canister
• Test under simulated
flight stresses, relaying
results to GSFC
Budget
Category Item Cost Category Item Cost
Controls Arduino Mega $58.95 Launch Travel Hotel 1st Group $960.00
Mux shield $24.95 Hotel 2nd Group $360.00
OpenLog $24.95 Plane 1st Group $1,430.40
MicroSD $30.00 Plane 2nd Group $1,437.00
Thermocouples $50.00 Food 1st Group $1,080.00
Total: $188.85 Food 2nd Group $480.00
Vehicle Rental, 1st Group $250.00
Support Structure Hardware $20.00 Vehicle Rental, 2nd Group $100.00
Aluminum tubing $80.00 Total: $6,097.40
Sorbothane $150.00
Aluminum Plate $60.00 Goddard Travel Plane $1,430.40
Fluid Tubing $40.00 Rental $35.00
Valves for fluid $40.00 Trips (x2) $1,465.40
Total: $390.00 Total: $2,930.80
Other Prototyping $500.00 EHD PUMP Goddard $$$ (Provided)
EHD Cylinder mount $1,750.00
Total: $2,250.00
Experiment Expenses $2,828.85
Travel Costs $9,028.20
Total Expenses $11,857.05
Total with 25% Margin $14,821.31
Conclusion
• Action items
– Order components
– Build and test
• Control subsystem
• EHD support system
– Maintain constant communication with GSFC
• Concerns?
– Dispersal of funds: working hard on this!