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MEP
(Martian Environmental Pod)
Critical Design Review
Fall 2003
Aerospace Engineering Department
University of Colorado-Boulder
Presentation Overview
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Descoping the Project
Request for Action (RFA’s)
System Architecture
Mechanical Design Elements
Electrical Design Elements
Integration Plan
Verification and Test Plan
Project Management Plan
Descoping the Project
• Thermal System
– 1 DOF instead of 2 DOF
– “Flower configuration” not necessary due to
no requirement of light concentration
– No phase change materials (paraffin) due to
complexity
• Actuation System
– Paraffin actuator to mechanical system
Request for Action
RFA
Author Solution
Define petal actuation system
Peterson
N/A due to descope
Compute amount of phase
change material
Maute
N/A due to descope
Constructing greenhouse:
Avoid molding, consider flat
sphere gores
Peterson
Addressed in greenhouse
construction
Test and verification plan
Argrow
Addressed in Test & Verification
Section
Project Objective
The overall objective of the proposed project
is to conceive, design, fabricate, integrate,
test and verify a deployable greenhouse for
a robotic Mars Lander.
Project Requirements
• Inflatable and deployable structure
• Capable of housing one Arabidopsis plant
but dimensionally not exceed 25’’ x 25” x10’’
• Mass must not exceed 3.5 kg (7.72 lbs)
• Power consumption must not exceed:
– 16 W-hrs. at night
– 30 W-hrs during the day
• Maintain delta pressure at 10 – 50 kPa
• Monitor temperature inside greenhouse and
reduce heat loss
System Architecture
• Greenhouse
– Greenhouse structure
– Mounting hardware
– Pressure system
• Thermal Shield and Structure
– Platform
– Petals with gear and axle
• Electrical System
–
–
–
–
Power supply
Software
Sensors
Thermal Actuation
System Design
(Stowed)
Stored System
• Dimensions: 21.75’’ x 8.3’’ x 4.3’’
– Under initial condtions
• Configuration for flight
– Greenhouse structure is deflated
• Configuration for daytime
– Greenhouse structure is inflated
– Allows for photosynthetic light
System Design
Fully Deployed
System Design
• Configuration for night
– Retards heat loss
– Protects greenhouse from dust storms
Greenhouse Design
Elements
James Ball
Manufacturing Enclosure
Material:
– Kapton HN (Type 100)
Manufacturing:
– Shell made out of rectangular
piece of Kapton and fastened
with solvent.
– Circular top will be attached
to one end with solvent
Stress on Greenhouse
• Stress
Pr
 15 MPa
2t
Pr
 t   30 MPa
t
l 
• Tensile Stress of
Kapton = 165 MPa
Mounting Greenhouse
• Cylinder will be
sealed around ring
using solvent
• The ring will be
secured to the top
box using screws and
a rubber o-ring
Ring
O-ring
Pressure System
• Single gauge regulator
- Output: 0 - 6080 kPa
- 60 psi safety relief valve
- Feed the control valve gas at 50 kPa
• 5 lb CO2 Tank
Control Valve
• Latching-type, high density, interface 3-way
solenoid valve
- 5 Volts
- 1100 Lohm ( 1.5 minutes to inflate)
- 5.5 mW per switch
- Dimensions: 1.12" long x 0.28" in. diameter
- Mount in electronics package with tubes
running into greenhouse
Control Valve Mounting
• Mounted on the
platform next to the
gear slot
• Will be underneath the
top box
• A small tube through
top of box to enclosure
Check Valve
• CCPI55100695 check valve
- Cracks at 69 kPa
- Flow rate = 250 Lohm
- Passive
- 5.5 mm diameter and 7.5 mm length
- Mounted in the top box with one end
inside of the enclosure
Check valve Mounting
•Will mount at the top
of box with one end
in the greenhouse
•Solvent to hold it
in place
Pressure System
Tank
Regulator
Control
Valve
Greenhouse
Check Valve
Test Plans
• Verify that the valve inflates enclosure to 50 kPa
and then turns off
• Fulfill the requirement that the enclosure is
inflatable
• Interpret the data to analyze how well it
maintains proper pressure levels
• Basic set up will include a CO2 tank, and a
regulator to send CO2 to the control valve
• This test will also be done in a wind tunnel and
outside in the cold to verify that it operates in
various conditions
Thermal Shield and
Assembly
Sara Stemler
Material
Aluminum
– densityal = 2700 kg/m3
– k = 237 W/m*K
Acrylic
– densityacrylic = 1400 kg/m3
– k = 0.27 W/m*K
 Acrylic reduces the weight and has a lower
thermal conductivity by a magnitude of 10
Thermal Analysis
Thermal Conductivity
– kKapton = 0.12 W/m*K
– kacrylic = 0.2 W/m*K
Thickness of Material
– tKapton = 5 mil
– tacrylic = 0.1’’
Heat Transfer Rate
T1  T 2

Q
Rtotal
Torsion Analysis
Shear stress:
Tr
 x 
J
Polar Moment of Inertia:
d 4
J
32
Torque:
T = F*d
Torque Analysis
•
•
•
•
Torque produced by petals = 367 oz-in.
Diameter of rod > 0.083 in.
Shear modulus (G) of acrylic = 167,000 psi
Polar moment of inertias (r = 0.25 in.)
– Solid rod = 3.8*10-4 m4
– Hollow rod = 3.6*10-4 m4
 JH > Js meaning lower stresses and less
weight
Gearing System
• 4:1 gear ratio will quarter the torque
necessary to operate the petals
• 0.5’’ diameter gear mounted on motor
shaft
• 2’’ diameter gear mounted on axle
Petal Assembly
• Varies in length from
7.5’’ – 14.25’’
• Varies in width from
6.5’’ – 8.3’’
• Tabs are placed along
each petal to “catch”
the subsequent petal
during deployment
Cost and Mass Analysis
Cost
Kapton HN
$45.00
Pressure Valve $50.00
Check Valve
$3.50
Thermal Shield $10.87
Platform/Axle
$3.15
Boxes
$0.20
Total:
$112.72
Mass
0.01 lbs
------3.003 lbs
0.870 lbs
0.971 lbs
4.854 lbs
Electrical Design Elements
Tod Sullivan
Electronics Overview
• Objectives
– Measure pressure and temperature
– Control pressure with Lee Co. Micro-Valve
– Open/close thermal shield
– Plot pressure vs. time & temperature vs. time
Valve
Plot
Temp vs. Time
Temp
Read Voltage Input
Calculate Temp
Store to file
Solar Panel
+ 5 V daylight
0 V night
NC
Limit
Switch
+
If P >= 50 kPa,
then output 0 V
If P < 50 kPa,
then output 5 V
5V
Power
Supply
Read Voltage Input
Calculate Pressure
Store to file
Relay
Motor
+
Plot
Pressure vs. Time
NC
Limit
Switch
Pressure
Electronic Subsystems
• Power Supply
• Software
• Sensors
• Thermal Actuation
Electronic Subsystems
• Power Supply
– 5 V fixed
– 3 A max current
– Tektronix PS280
Electronic Subsystems
• Software
– LabView Tacklebox Station
• LabView
• BNC Terminal Block
– DIO Channel
– Analog Input (Pressure Sensor)
– Analog Input (Temperature Sensor)
• 12 bit DAQ Card
Plot
Temp vs. Time
Read Voltage Input
Calculate Temp
Store to file
If P >= 50 kPa,
then output 0 V
If P < 50 kPa,
then output 5 V
Read Voltage Input
Calculate Pressure
Store to file
Plot
Pressure vs. Time
ACH 1
DIO 1
ACH 0
Electronic Subsystems
• Thermistor
– Omega 44000 series
• 2252 Ω
• R1 = 1000 Ω
• Resolution: 0.1 °C
5V
R1
V
Electronic Subsystems
• Pressure Sensor
– Omega PX139 Differential Pressure
– 4 V span of 30 psi
5V
– Vres = 0.9 mV
– Resolution: 0.5 kPa
V
Electronic Subsystems
• Thermal Actuation
– DC motor open/close the thermal shield
• 5 V power supply
• Theoretical torque of 367 oz-in
– Faulhaber 2342-006CR
• Torque rating = 12.35 oz-in
• 5 rpm
• 0.1944 lb
– Faulhaber 23/1 planetary gearbox
• 989:1 ratio
• 0.2425 lb
DC Motor
Solar Panel
+ 5 V daylight
0 V night
NC
Limit
Switch
+
5V
Power
Supply
Relay
Motor
+
NC
Limit
Switch
DC Motor
• Limit Switch
– 3 A rated limit switch
• NC
• Relay
–
–
–
–
Potter & Brumfield
R10E1Y2S200 DPDT
2A
5 V coil
• Solar Panel
– 5V
– 100 mA
– SC-1 Solar World
Power Analysis
• Power consumption
– Valve
• 5.5 mW-s
– Initial fill time = 1.02 min.
– Pressure Sensor
• 5V * 2 mA = 0.01 W
– Thermistor
• 5V * 1.5 mA = 0.0077 W
– DC motor
• 5V * 1 A = 5
Power Analysis
Power Consumption 24 hrs
30
25
Power (W)
20
Power Valve
Power Limit
Power Motor
Power Press
15
Power Temp
Power Total
Power Limit
10
Initial
Gas Fill
5
Motor On
0
0
200
400
600
800
Time (min)
1000
1200
1400
Power Analysis
Power Consumption 24 hrs
1
0.9
0.8
0.7
Power Valve
Power (W)
0.6
Power Motor
0.4
Power Press
Total
Power
Valve
Power
0.5
Power Temp
Power Total
Power Limit
0.3
0.2
Sensor
Power
0.1
0
0
0.2
0.4
0.6
0.8
1
Time (min)
1.2
1.4
1.6
1.8
2
Power Analysis
Power Consumption 24 hrs
30
Power Limit
Day
25
Power Limit
Night
20
Power (W)
Power Valve
Power Motor
Power Press
15
Power Temp
Power Total
Motor
Operation
10
Power Limit
5
0
715
716
717
718
719
720
Time (min)
721
722
723
724
725
Electronic Noise Analysis
• Noise
– Usual noise from lab stations
• 0.02 mV
– Signal Resolution
• 0.01 v
– Signal to Noise Ratio
• Noise at 0.02 mV
– S/N = 50
• Noise at 1 mV
– S/N = 10
Electronic System
• Mass & Cost Distribution
Cost
Mass
Motor
$219.30
0.4369 lb
Pressure Sensor
$85.00
0.07 lb
Thermistor
$15.00
0.0013 lb
Resistor
$1.00
0.00066 lb
Solar Panel
$20.00
0.2 lb
Relay
$4.10
0.024 lb
Limit Switches
$6.00
0.10 lb
Total
$350.40
0.633 lb
Integration
Sub-Assemblies
• Thermal Shield
– Petals
– Platform
– Axle/Axle Mount
• Mounting Box
– Greenhouse
– Ring
• Electronics Box
– Circuit
– Motor
Greenhouse
x 10
Mounting Box
Thermal Petals
Electronics Package
Platform
Thermal Shield Sub-Assembly
Verification Needs
•
•
•
•
•
•
•
Deployable and inflatable
Maintain delta pressure of 10 – 50 kPa
Thermal shield actuation
Reduction of heat loss
Power consumption ≤ 16 W-hrs
Motor Circuit
Temperature and pressure sensor outputs
Testing and Verification
Thermal Shield
• Ability of thermal shield to open and close
– Examination
• Torque produced by petals
– Analysis of current draw of motor
• Rate of heat transfer at varying temperature
– Testing in different temperature conditions
Structural Operation
• Hypothesis: The thermal shield will open and
close in approximately 10 secs
• Test
– Through examination, verify that the thermal shield
operates
– Time the 180° rotation of the petals
• Purpose: To ensure the thermal shield can open
and close based on structural design
Torque Analysis
• Objective: Measure the torque required by
the motor to operate the petals
• Current draw (A) → km → Torque
• km = 0.817 oz-in/A
– Property of motor
• Measure current draw using ammeter to
derive the torque produced by the motor
• Need? – Drives torque of motor necessary
Rate of Heat Transfer
• Objective: Calculate the rate of heat loss when
the temperature drops at night
• Using the temperature sensor readings for
internal temperature, set up a thermistor outside
of the structure to record temperature.
• Calculate and plot Q, rate of heat transfer
T1  T 2

Q
Rtotal
Testing and Verification
Pressure System
• Verify that the valve inflates enclosure to 50 kPa
and then turns off
• Fulfill the requirement that the enclosure is
inflatable
• Interpret the data to analyze how well it
maintains proper pressure levels
• Basic set up will include a CO2 tank, and a
regulator to send CO2 to the control valve
• This test will also be done in a wind tunnel and
outside in the cold to verify that it operates in
various conditions
Testing and Verification
Pressure System
• Increase pressure above 69 kPa to verify
that check valve functions properly
• Meet the requirement that it maintains an
internal pressure below 69 kPa
• Analyze data to be sure that proper
pressure levels are maintained
• Basic set up:
– Tank and pressure valve sending gas to the
control valve
Testing and Verification
Pressure System
• For a leak rate of 5 g/m2/day we predict to lose
0.14 L/day which will reduce pressure by 5.5
kPa
• This should require that the valve should open
each day for 3 seconds
• Monitor pressure data
• Determine the leakage rate and compare to
prediction
• Determine how often to open valve (and for how
long) in order to maintain pressure
• Basic setup includes previous setup and the
LabView Tackle Box
Testing & Verification
Electronics
• Electronics Subsystems Testing
– Analytical Testing
• Power Consumption Test
– Verification Testing
• Motor Circuit
– Relay Operation
– Motor Reversal
– Motor Direction
• Pressure Sensor
• Thermistor
Power Consumption
• Measure the power consumption of
system
– Use ammeter to measure current draw
• P = IV
– Compare to Theoretical Calculations
• Power Consumption Success
– Does not exceed limits
• 30 W-hr Day
• 16 W-hr Night
Motor Circuit
• Verify Relay Operation
– Use Lab Station to Toggle 5 V coil
– Measure Voltage at motor connection
– Results: Input 5V = Output 5V
Input 0V = Output -5V
• Motor Direction
– Use Lab Station to Toggle = +/- 5V motor connection
– Results: +5V = CW -5V = CCW
• Motor Reversal
– Use Lab Station to Toggle 5 V coil
– Verify integration of relay & motor
– Results: Relay Input 5 V = Motor Output of CW
Relay Input 5 V = Motor Output of CCW
Pressure Sensor
• Verify Pressure Sensor Operation
– Apply 5 V to sensor at Lab Station
– Measure voltage output
– Apply pressure to sensor
– Results: Vout = 2.25 V no pressure
Vout = 2.25 + V pressure
Thermistor
• Verify Temperature Sensor
– Apply 5 V to thermistor at lab station
– Measure voltage output
– Record Vout & ambient temperature
– Place thermistor is ice bath
– Measure voltage output
– Record Vout & ambient temperature
– Verify results with conversion values
Org. Chart
Martian Environmental Pod
Project Manager
Advisors
Project
Advisory Board
Sara Stemler
Prof. Jean Koster
Prof. Jim Maslanik
CFO
Webmaster
Safety Engineer
Tod Sullivan
Tod Sullivan
James Ball
Structure
Manufacturing
Data Acquistion
Materials
Sara Stemler
James Ball
Tod Sullivan
Sara Stemler
Work Breakdown Structure
MEP
1.0 Proj. Mgmt.
2.0 Sys. Eng.
3.0 Design
4.0 Fabricate
5.0 Test & Verify
6.0 Tech. Report
1.1 Planning
2.1 Objectives
3.1 Greenhouse
4.1 Greenhouse
5.1 Inflation
6.1 Reviews
1.2 Task Mgmt.
2.2 Specs
4.2 Thermal Controls
5.2 Deployment
1.3 Financial
1.4 Website
2.3 Trade Studies
3.2 Thermal Controls
3.3 Electronics
3.4 Interface
4.3 Electronics
5.3 Thermal Shield
5.4 Actuation System
5.5 Pressure System
6.2 Reports
References
1.)
2.)
3.)
4.)
5.)
Drost, MK et al. MicroHeater. Pacific Northwest National
Laboratory, 1999.
Kedl, RJ. Wallboard with latent heat storage for passive
solar applications. Oak Ridge National Laboratory, May 1991.
Mattingly, Jack. Elements of Gas Turbine Propulsion: McGrawHill,1996.
Vable, Madhukar. Mechanics of Materials: Oxford University
Press, 2002.
Consolmagno/Schaefer. Worlds Apart: Prentice Hall, 1994.
Questions?