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

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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

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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

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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

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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!