1 microbial detection arrays october 23 rd, 2006 aerospace senior projects university of colorado -...
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1
Microbial Detection Arrays
October 23rd, 2006
Aerospace Senior Projects
University of Colorado - Boulder
2
Team Members
• Elizabeth Newton – Project Manager• Shayla Stewart – Systems Engineer• Steven To – Chief Financial Officer• Dave Miller – Fabrication Engineer• Ted Schumacher – Lead Thermal Engineer• Jeff Childers – Lead Structural Engineer• Charles Vaughan – Lead Electrical Engineer• Sameera Wijesinghe - Webmaster
3
Briefing Overview
• Overall Objectives
• System Design Alternatives
• Design-To Specifications
• Thermal Design Options
• Structural Design Options
• Electrical Design Options
• Project Feasibility and Risk
• Project Plan
• Appendices
Jump to
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4
Overall Objectives
Picture from www.physics.byu.edu
5
Objectives Overview• Objective: To design and build a field-ready unit capable of
providing a testing environment for electrochemical sensors to detect microbial life by soil analysis
• Deliverables:– Field-ready unit– Test data verifying requirements– Operational manual for use
Electrochemical sensors
• Sensors developed by Tufts University and BioServe – Sensors analyze soil for metabolic indicators such as pH and chemical
composition and convert them to electronic signals– Assumes that life only needs water and nutrients found in native soil to
metabolize
6
Functional Diagram
Geological Sample
Soil Sterilization
Temperature Control
Temperature Control
Test Chamber
Temperature Control
Control Chamber
Inoculation Sample
Reagent Water
Sensors
Data Acquisition and Control
Power
Mixer Mixer
• Accept soil• Sterilize soil using
an autoclave• Add reagent water• Move soil to
reaction chambers• Add non-sterile
inoculation sample to test chamber
• Mix soil and water while starting temperature control
• Testing lasts for two weeks
7
Functional Requirements
• Must be capable of performing in extreme Earth conditions– McMurdo Bay, Antarctica
-10°C to 2°C (during summer)
– Atacama Valley, Chile-6°C to 38°C
• Must provide and function with power comparable to next-generation Mars science rovers (30 Watts)
• Must be portable (30 kg)Pictures from Wikipedia.org
8
Assessment of System Design Alternatives
• Quantitative analysis of cost, mass, and volume based on rough estimates
• Ultimately, complexity became primary consideration
Environmental Controls
Separate
Shared
Separate
Shared
Sterilization Chamber
Overall Architecture:
•Shared Environment
•Separate Sterilization Chambers
Pro-Reaction chambers at same temperature-No need to heat/cool each chamber individuallyCon-No way to correct if one chamber is warmer than the other-More volume to heat/coolPro
-No need for extra environmental chamber
Con
-Each reaction chamber must be heated/insulatedPro-Only one chamber must be fabricated-Only needs one heaterCon
-Soil must be separated into test/control chambers after sterilizationPro
-No need for soil separation: reduced complexityCon
-Two chambers and two heaters
9
System Design Alternatives
End Result
• Separate Autoclaves
• Shared Environment
10
• Thermal Subsystem– Mass: 16.3 kg– Volume: 0.096 m3
– Cost: $660• Structural Subsystem
(excluding chassis)– Mass: 11.3 kg– Volume: 0.00293 m3
– Cost: $280• Electrical Subsystem
(excluding power supply)– Mass:0.30 kg– Volume:0.00045 m3
– Cost:$1340• Overall System
– Mass:27.9 kg– Volume:0.09938 m3
– Cost:$2280• Total Funds: $8000
Design-To Specifications
11
Overall System Architecture
Autoclaves
Water Chamber
Pump
DAQ/Power TEC
Inoculation Chamber
Test Chambers
12
Work Breakdown Structure
MiDAs
Thermal SubsystemStructural Subsystem
Electrical Subsystem
Thermal Control
Insulation
Materials
Soil/Water Transport
Mixing
Power
Data Acquisition
Sensors
13
Thermal Design Options
Pictures from melcor.com, minco.com, wikipedia.org, energysolutionscenter.org
14
Insulation Options
• Insulation applications– Autoclave chambers – Environmental chambers – Reagent water chamber– Inoculation sample chamber
• Insulation Requirements– Minimize power needed to heat chambers– Protect electrochemical sensors from heaters
• Criteria (order of importance)1. Volume (thermal conductivity, k)2. Complexity 3. Cost
15
Insulation Option Pros and Cons
Pros Cons
Silica Aerogel-Very low thermal conductivity
-Expensive
Thermal Coat - Ceramic
-Moisture resistant-Adds almost no volume because it is painted on
-Complicated application
Fiber Board (Sindayno) -350
-Very low density-Thermal conductivity is higher than that of air
Additional Options for Heating and Cooling
16
Structural Design Options
Pictures from trendir.com, polypenco.co.jp, sonozap.com, sciencelab.com, parker.com
17
Material Options
• Material applications– Autoclave chambers
• Must be able to withstand high temperatures and pressures
• Must be corrosion-resistant– Environmental, inoculation, and reagent water
chambers • Need to be lightweight
– Reaction chamber• Must be able to be sterilized • Must be inert
• Criteria (order of importance)1. Mass2. Complexity (machineability)3. Cost
18
Material Pros and Cons
Pros Cons
Polysulfone
-Low density
-High yield strength
-Easy to machine
-Could not withstand contact with heating elements
-Somewhat expensive
316 Stainless Steel
-High strength
-Very high melting temperature
-Relatively inexpensive
-High density
Ultem 1000
-Low density
-High yield strength
-Easy to machine
-Relatively inexpensive
-Could not withstand contact with heating elements
Additional Options for Soil/Water Transportation and Mixing
19
Electrical Design Options
Pictures from spectrolab.com, fuelcellstore.com, dpie.com, weedinstrument.com
20
Power Supply Options
• Power supply requirements– Power supply must provide 30 W of
power– Must power the MiDAs instrument for
duration of experiment (17 days)• Criteria (order of importance)
– Cost– Mass– Volume
21
Power Supply Pros and Cons
Pros Cons
Fuel Cell -Very high energy density
-Safety and logistic issues
-Switching out tanks
-Expensive
Sealed Lead Acid Battery
-High energy density
-Less complex
-Very large and heavy
-Requires a recharge system
Lithium Ion Battery
-Very high energy density
-High demand
-Requires a recharge system
-Problems holding charge with age
Dual Junction Solar Cells
-Safe, relatively simple
-Can be used to recharge batteries
-Requires sunshine
Additional Options for Data Acquisition and Pressure/Temperature Sensors
22
Feasibility and Risk
Picture from http://www4.macnn.com/games/gamecenter/risk2/s_01_lrg.jpg
23
Project Risk Assessment
Subsystem
Mitigation Factors Risk Factors
Lots of Options
Inexpensive
Easy to O
btain
Sim
ple
Easy to M
achine
Lack of E
xpertise
Expensive
Difficult A
nalysis
Hard to O
btain
High P
ower U
se
Thermal Control X X X
Insulation X X X
Material X X X X X
Soil Handling X X X
Mixing X X X X
Power Supply X X X
Data Acquisition X X X
Sensors X X XGreen Subsystems= Low Risk Yellow Subsystems = Medium Risk Red Subsystems= High Risk
24
Autoclave Feasibility Assumptions
– Fluid inside is only water (high specific heat of water will give maximum boundary)
– Insulation radius = 10 cm of material (thermal conductance of k = 0.012 W/m °C)
– Internal and external losses and safety margin = 2.4W (20% of heating/cooling capacity)
– Specific heat (Cp) for 316 steel = 452 J/kg K– Specific heat (Cp) for water = 4230 J/kg K – Heater uses 12 W per chamber– Standard autoclave techniques implies
• 121°C, hold for 15 min• Cool to 20°C, hold for 24 hours• Repeat 3 times
25
Autoclave Feasibility Analysis
• Time to heat from -10°C to 121°C = 3.9 hours
• Time to cool to 20°C = 117 min with active cooling
• Power:– 3.9 amp hours to heat– 0.04 amp hours to hold
for 15 minutes– 1.95 amp hours to cool– 3.36 amp hours to hold
for 24 hours
Cm
Wh
22 25
WCRRR convectionconductiontotal 82.79
WR
TTQ
total
gssurroundininside 64.1
QUUU watersteelsys
waterpsteelp TTcmTTcmQ )])()([()])()([( 1212
WC
AhR
outsideconvection 427.0
1
2
Rconduction = kA
Thickness= 79.8 C/W
26
Autoclave Solution and Verification
• Solution:– Sterilization chamber mock-ups will be
made and tested with various heaters and insulation to verify that it is possible to achieve 121°C
• Verification:– Temperature and pressure sensors will be
used to verify that a sand/water solution can reach 121°C on 30 W of power
27
Autoclave Power SummaryPower Summary (Sterilization Phase)
0
5
10
15
20
25
30
35
030
060
090
012
0015
0018
00
Operation Time (min)
Po
wer
Co
nsu
mp
tio
n (
W)
Autoclave Heater/Cooler 1
Autoclave Heater/Cooler 2
DAq
Temp/Pressure Sensors
Total Power
28
Mixing Feasibility Analysis• Requirement:
– Soil and water must be mixed within the reaction chambers
• Reduces boundary layer so electrochemical sensors can read correctly
• Prevents soil sedimentation
• Problem:– Difficult to find mixers small enough to fit in
reaction chambers– Flow pattern difficult to analyze without testing– Unknown if ultrasonic mixers can be used at
appropriate frequency– Magnetic stirrers may affect electrochemical
sensors
29
Mixing Solution and Verification• Solution:
– Mock-ups of reaction chambers will be prototyped and tested with various mixers
– Different soil granularities will be tested– Various mixing regimes will be tested
• Continuous mixing• Pulsed mixing
• Verification:– Flow patterns and soil sedimentation will be visually
analyzed to show that various types of mixing regimes and mixers provide adequate stirring
30
Project Plan
Picture from http://www.connectedconcepts.net/clip%20art/Project%20Plan.gif
31
Organizational Chart
Project ManagerElizabeth Newton
Chief Financial OfficerSteven To
Systems EngineerShayla Stewart
Safety EngineerChuck Vaughan
Fabrication EngineerDave Miller
Thermal Subsystem Electrical Subsystem Structural Subsystem
Thermal LeadTed Schumacher
Dave Miller
Jeff Childers
Shayla Stewart
Electrical LeadChuck Vaughan
Steven To
Structures LeadJeff Childers
Elizabeth Newton
Sameera WijesingheSameera Wijesinghe
32
Schedule Through CDR
33
Schedule Through CDR
34
Schedule Past CDR
• Machining:– Assume one chamber machined per week – Last Machining Day – March 16, 2007
• Testing:– Subsystem testing can begin as soon as each
chamber is constructed– Overall testing: March 16, 2007 – April 17, 2007
• Final Review – April 17, 2007• ITLL Expo – April 28, 2007• Final Report – May 3, 2007
35
Conclusions
• Project is feasible– Budget is one-quarter of funds – Mass is 34 kg, which is portable– Initial calculations and research indicate that high risk
subsystems (mixing and autoclaving) are challenging but possible
• Further analysis through prototyping will be performed before CDR
– System is capable of performing in specified environments
– System is capable of performing with 30 W of power– Many options are available to meet each requirement
• This allows off-ramps in case some options are dismissed during design
36
Questions/Comments?
Picture from http://content.answers.com/main/content/wp/en/thumb/5/5b/250px-Nasa_mer_marvin.jpg
37
References
1. Cengel, Yunus. Introduction to Thermodynamics and Heat Transfer.
McGraw-Hill. University of Nevada, Reno. 1997
2. Gilmore, David. Spacecraft Thermal Control Handbook. Aerospace press. El Segundo, California. 2002
3. www.aerogel.com
4. www.dimondsystems.com
5. www.matweb.com
6. www.mcmaster.com
7. www.melcor.com
8. www.minco.com
9. www.omega.com
38
Appendix Table of Contents
• System Architecture Options
• Chamber Geometries
• Verification Methods
• Power Model and Budgets
• Operational Environment
• Subsystem Options, Trade Studies, and Pros and Cons
39
Appendix A: System Parameter Estimates
Mass (g) Volume (mL) Cost
Reaction Chamber 127 100 $11
Large Autoclave Chamber 4013.5 500 $125
Small Autoclave Chamber 2006.75 250 $63
Soil Transport 88 100 $2.60
Motor 150 200 $20
Moving Sensor Package 254 200 $22
Environmental Sensors 10 50 $200
40
Assessment of System Design Alternatives
Quantitative Analysis of Options
Mass
(g)
Volume
(mL)
Cost
Shared Environment, Shared Sterilization
900 4444 $150
Separate Environment, Shared Sterilization
1200 4504 $1,350
Separate Environment, Separate Sterilization
1400 4612 $1,750
Shared Sterilization, Separate Environment
1300 4592 $1,350
Mass, volume, and cost figures do not include components that all options need the same number of, such as a reagent water tank and mixers.
41
Option A• Sterilization and
testing occur in same chamber
• Requires:– 1 large
autoclave– 2 moving sensor
packages– 2 motors– 2 environmental
sensors• High complexity
from moving sensor packages
Mass: 1000 g Volume: 4842 mL Cost: $600
42
Option B
• Shared sterilization, separate environment
• Requires:– 1 large
autoclave– 2 reaction
chambers– 2 soil transport
tubes
Mass: 900 g Volume: 4444 mL Cost: $150
43
Option C
• Shared sterilization, separate environment
• Requires:– 1 large autoclave– 2 reaction
chambers– 2 soil transport
tubes– 6 environmental
sensors
Mass: 1200 g Volume: 4504 mL Cost: $1350
44
Option D
• Separate sterilization, separate environment
• Requires:– 2 small
autoclaves– 2 reaction
chambers– 3 soil transport
tubes– 8 environmental
sensorsMass: 1400 g Volume: 4612 mL Cost: $1750
45
Option E
• Separate sterilization, shared environment
• Requires:– 2 small
autoclaves– 2 reaction
chambers– 3 soil transport
tubes– 6 environmental
sensors
Mass: 1300 g Volume: 4592 mL Cost: $1350
46
Autoclave Chamber Geometry
• Assumptions of a possible design: – Chamber is made of 316 stainless steel – 5 mL water added to chamber for use in autoclaving – 15 mL space provided so sample is not tightly packed– Chamber is a cylinder
• Dimensions:– Total internal volume of chamber = 45 mL– Internal diameter = 2.54 cm– External diameter = 3.04 cm– Wall thickness = 0.25 cm – Length = 9.38 cm – Mass = 0.19 km
47
Reaction Chamber Geometry
• Assume: – Chamber is made of Ultem 1000– Chamber wall thickness of 0.5 cm– Inside chamber geometry is a
cylinder– 20 mL additional space for mixing
(70 mL total volume)• Dimensions:
– Walls: 0.5 cm thick – Outside diameter = 3.95 cm– Height = 11.28 cm – Mass = 0.0866 kg
Drawings by Jake Freeman
48
Environmental Chamber Geometry
• Assume:– Chamber is a cube
containing both reaction chambers
– Buffer around chambers is 3 cm with 2 cm between them
• Dimensions:– Height: 17.28 cm– Depth: 9.95 cm– Width: 11.95 cm– Volume: 2054.635 cm3
Top View
Side View
49
Reagent Water Chamber Geometry
• Assume:– Chamber is a cylinder– Water expands upon
freezing• Dimensions:
– Height: 2.1 cm– Radius: 3.0 cm – Volume: 60 cm3Side view
50
Verification MethodsRequirement
#Title
VerificationMethod
Verification
PDD 4.1Reaction Chamber
VolumeI, D Verification will be through simple volume measurement.
PDD 4.2Reaction Chamber
TemperatureA, T
Verification will be through thermal analysis of the reaction chamber geometry and test by means of simple temperature sensors.
PDD 4.3Reaction Chamber
PressureA, T
Verification will be through thermal analysis of the reaction chamber geometry and test by means of simple pressure sensors.
PDD 4.4Reaction Chamber
Sensor CapabilityA, I
Verification will be through analysis of the chamber geometry and by visual means.
PDD 4.5Reaction Chamber Mixing
CapabilityA, I
Verification will be through analysis of the flow pattern generated during mixing and basic prototype inspection testing.
PDD 4.6Reaction Chamber Multi-
Use PortA, I
Verification will be through analysis of the chamber geometry and by visual means.
PDD 4.7Reaction Chamber
MaterialA
Verification will be through structural and thermal analysis of the reaction chambers.
PDD 4.8Geological Sample
VolumeT
Verification will be through measuring soil before it is added to the autoclave chambers
PDD 4.9Inoculation Sample
VolumeT
Verification will be through measuring inoculation sample before it is added to the inoculation sample chamber
PDD 4.10Inoculation Sample
Reception A, D
Verification will be through analysis of soil transport and demonstration to show sample delivery.
51
Verification MethodsRequirement
#Title
VerificationMethod
Verification
PDD 4.11Reaction Sample
HandlingA, T
Verification will be through thermal analysis of the autoclave chambers and testing by means of temperature and pressure sensors.
PDD 4.12 Inoculation Sample
HandlingA, T
Verification will be through thermal analysis and testing by means of temperature sensors.
PDD 4.13Reaction Sample
DeliveryA, D
Verification will be through analysis of soil transport and demonstration to show sample delivery.
PDD 4.14 Inoculation Sample
SterilityA, D
Verification will be through analysis of soil transport and demonstration to show sample delivery.
PDD 4.15Reagent Water Containment
A, T Verification will be through thermal analysis and test by means of temperature sensors.
PDD 4.16 Reagent Water Delivery A, DVerification will be through analysis of soil transport and demonstration to show sample delivery.
PDD 4.17Reagent Water Temperature
A, TVerification will be through thermal analysis and test by means of temperature sensors.
PDD 4.18 Sensor Integration A, IVerification will be through analysis of the reaction chamber geometry and simple volume measurement.
PDD 4.19Sensor Data Collection
RateA, T
Verification will be through analysis and testing of the command software.
PDD 4.20 Sensor Data Acquisition A, TVerification will be through analysis and testing of the command software.
52
Verification Methods
Requirement #
TitleVerification
MethodVerification
PDD 4.21Sensor Data Accessibility
D Verification will be through demonstration of data transfer.
PDD 4.22MiDAs Status
WarningsA, T
Verification will be through analysis and testing of the command software.
PDD 4.23 MiDAs Command A, T Verification will be through analysis and testing of the command software.
PDD 4.24 Field Power A, T Verification will be through analysis of the power supply and testing through standard electronics lab equipment.
PDD 4.25 Laboratory Power D Verification will be through a demonstration of the instrument with the external laboratory power supply.
PDD 4.26Nominal Power Consumption
A, TVerification will be through analysis of the power consumption of each component and testing.
PDD 4.27Peak Power Consumption
A, T Verification will be through analysis of the power consumption of each component and testing.
PDD 4.28 Unit Disassembly DVerification will be through a demonstration of the instrument disassembly.
PDD 4.29 Operational Cycle DVerification will be through a demonstration of a complete operational cycle.
PDD 4.30Operational Environment
AVerification will be through thermal analysis of the surrounding environment.
53
Power Model
Power Summary (Experiment)
0
5
10
15
20
25
012
024
036
048
060
072
084
096
010
8012
0013
2014
4015
6016
8018
0019
20
Operation Time (min)
Po
wer
Co
nsu
mp
tio
n (
W)
Thermal
Structures
Electronics
Total
54
Mass Budget
Autoclave (316 Steel) x 2 9 kg
Test/control/water chamber (Ultem1000) x 3 2.13 kg
Inoculation chamber (Ultem1000) 0.19 kg
Autoclave Insulation (Aerogel) 13.4 kg
Test/control Insulation (Aerogel) 2.9 kg
DAQ 0.285 kg
Sensors 0.125 kg
Extra (Ultem1000 Chassis) 6 kg
Power supply 4 to 30 kg
Total (excluding power supply) 34 kg
55
Cost Budget
Heaters x 4 $160
Autoclave (316 Steel) x 2 $240
Test/control/water chamber (Ultem1000) x 3
$40
Inoculation chamber (Ultem1000)
Included above
Autoclave Insulation (Aerogel)
$500 (min purchase)
Test/control Insulation (Aerogel)
Included above
DAQ $995
Sensors $345
Total $2280
Total Funds:
$4000 from Senior Projects
$4000 from BioServe
Total: $8000
56
Operational Environment
Laboratory
McMurdo Bay,
Antarctica(summer)
Atacama Valley, Chile(Altitude =
2000 m)
Temperature (max)
30°C 2°C 38°C
Temperature (min)
20°C -10°C -6°C
Pressure (avg)
1 atm 1 atm 0.802 atm
57
Thermal Control Design-To Requirements
Requirement #
Title Requirement Importance
PDD 4.2Reaction Chamber Temperature
Each reaction chamber shall be controllable within a range of 4°C to 37°C with an accuracy of ±1°C.
This environment is acceptable for the possible life to metabolize and reproduce.
PDD 4.11 Reaction Sample Handling
The reaction samples shall be sterilized in accordance with standard Autoclave techniques.
This is the best method of sterilization for killing the known forms of life.
PDD 4.15Reagent Water Containment
The sterile reagent water shall be completely contained in both solid and liquid form.
This prevents the reagent water container from bursting if the water freezes.
PDD 4.17Reagent Water Temperature
The reagent water shall be delivered to the reaction chambers at a temperature not to exceed 60°C.
The electrochemical sensors can't withstand temperatures above 60°C.
PDD 4.30 Operational Environment
MiDAs shall be able to operate in environments ranging from Antarctica to Atacama Valley in Chile.
These are the likely test sites for the MiDAs instrument.
58
Heating/Cooling Options
• Heating applications– Autoclave chambers: must reach 121°C and hold
for 15 minutes– Environmental chambers: must maintain
temperatures from 4°C to 37°C for 14 days
• Cooling applications– Autoclave chambers – must be cooled from 121°C
to 20°C– Environmental chambers – must maintain
temperatures from 4°C to 37°C for 14 days
• Criteria1. Volume 4. Complexity2. Power consumption 5. Mass3. Risk 6. Cost
59
Heating Option Pros and Cons
Pros Cons
Strip -Strong sheath -Difficult to find small sizes
Tubular -Good at heating air-Custom length and resistance
needed
Tape or flexible-Cheap-Easy to custom-order-Kapton coating
-Clamping system required-Best used for conduction
heating
Immersion-Direct heating for
substance -Heating element may get in
the way of mixer
Cartridge -High watt density-Requires tight tolerances for
placement
Band -Strong sheath-Small sizes don’t have high
wattages
60
Cooling Option Pros and Cons
Pros Cons
Passive-Does not require power-Simple
-Geometry of chambers may limit effectiveness-Longest cooling time
Heat Switch-Allows most sides of chamber to be insulated while still allowing cooling
-Complex implementation-Difficult to find data
Thermoelectric Cooler
-Concentrated cooling power-Allows most sides of chamber to be insulated while still allowing cooling
-Requires power
61
Heating Options
Heating application
Typical off the shelf example
Power of example
Overall Size of example (inches)
Weight of example
(lbs)
Price of example
Strip Gases or solid surfaces
Omega PT-512/120
2.5W at 12V 5.5 x 1 x 1.5 0.4 $30
Tubular Gases Omega TRI-1212/120
3.3W at 12V 0.246 O.D.x 12 long
0.2 $28
Tape or flexible Solid surfaces or possibly gases
Minco HK5464R4.9L1
2A
29.39W at 12V
3 x 3 0.01 $33.80
Immersion Liquids Omega RI-100/120
2W at 12V Internal heating component =
tube 1.5 long x 0.625 O.D.
3 $115
Cartridge Solids Omega CSS-01235/120
0.7W at 12V 0.124 O.D. x 2 long
0.06 $26
Band Solids in cylindrical form
Omega MBH-1215200A /120
4W at 12V 1.25 I.D. x1.5 width
0.87 $32
62
Cooling Options
Typical off the shelf example
Power of example
Overall Size of example
(inches)
Weight of example
(lbs)
Price of example
Passive Cooling
NA 0 0 0 $0
Heat Switch Starsys Research
Diaphragm Thin Plate
Switch
May not be available at this time
Thermoelectric Cooling
Melcor CP1.0-127-05L-1-W5
16 W 30 mm x 30 mm x 3.2 mm
0.024 $15.54
63
Insulation Options
Density (kg/m^3) Cost K (W/m-K)
Silica Aerogel 5-200$325 for 50 g + $30
shipping0.016-0.03
TC- Ceramic Unknown Unknown 0.097
Fiber Board (Sindayno) -350 1900 Unknown 0.63
Air 1.168 NA 0.025
64
Material Design-To Requirements
Requirement #
Title Requirement Importance
PDD 4.7Reaction Chamber Material
Each reaction chamber shall be manufactured out of a list of materials provided by BioServe. This list includes, but is not yet limited to, Polysulfone, Pharmed, 316 stainless steel, and Ultem 1000.
All of these materials are able to be autoclaved, have high resistance to corrosion, and are FDA approved for food service or medical use.
PDD 4.11Reaction Sample Handling
The reaction samples shall be sterilized in accordance with standard Autoclave techniques.
This is the best method of sterilization for killing the known forms of life.
65
Material Options
Density
(g/cm3)
Yield Strength
(MPa)
Maximum Temperature
(°C)
Cost per kg Machineability
Polysulfone 1.24 74.9 149-180 $5.93 Very good
316 Stainless
Steel
8.027 205 899 $2.32 Fair
Ultem 1000 1.27 110 170 $3.84 Very good
66
Soil Handling Design-To RequirementsRequirement # Title Requirement Importance
PDD 4.8 Geological Sample VolumeEach reaction chamber shall receive no less than 5 mL and no more than 25 mL of geological sample.
5 mL is the about the minimum amount of soil to obtain good results. 25 mL is still small enough amount to keep the experiment light and portable.
PDD 4.9 Inoculation Sample VolumeThe test chamber shall receive a maximum of 1 mL of inoculation sample.
The nonsterile inoculation sample is what could contain life.
PDD 4.10 Inoculation Sample Reception
The test chamber shall receive the inoculation sample through established aseptic techniques.
The user needs to know that any detected life forms were already present in the soil, not transferred to the soil through the transportation method.
PDD 4.13 Reaction Sample Delivery
One pre-measured reaction sample shall be delivered to the test chamber and one pre-measured reaction sample shall be delivered to the control chamber. Both samples shall maintain sterility throughout delivery.
Having equal amounts of soil in each reaction chamber helps maintain uniformity between the test and control. Once the soil is sterilized, it has to remain sterile so that no life forms are introduced.
PDD 4.14 Inoculation Sample SterilityThe inoculation sample shall be aseptically delivered to the test chamber.
The inoculation sample can't pick up any living organisms from the MiDAs instrument. If life is detected, one needs to know that it was originally in the soil or the experiment is useless.
PDD 4.16 Reagent Water Delivery
The MiDAs shall aseptically deliver no more than 50 mL (within ± 5% accuracy) of sterile reagent water to each reaction chamber.
The delivery must be aseptic, so that no living organisms are transferred to the reagent water.
PDD 4.28 Unit DisassemblyMiDAs shall be able to be taken apart so that it may be sterilized and reassembled for multiple Earth tests.
The instrument needs to be reusable.
67
Soil/Water Transportation Options
• Soil and water transportation includes pumps, tubing, and valves
• Soil/water handling applications– Reagent water transferred to sterilization and
inoculation chambers to flush soil– Soil and water mixture transferred from
sterilization and inoculation chambers to reaction chambers
• Criteria1. Complexity (autonomy)
68
Soil/Water Transportation Pros and Cons
ProsCons
Push/Pull Solenoids
-Simple -Low cost
-High reliability -Small-Not variable
Electromagnets-Simple -Med cost
-High reliability -Small-High power usage
Motor-Compatibility -Low cost
-Small
-Complexity
-Low reliability
Pressure Sealing
-High reliability
-Two way-Complex setup
Magnetic Sealing
-Less parts
-Low reliability -Complex setup
-One way
-May have interference with sensors
Gat
esS
eali
ng
69
Soil Transportation Options
Gate Options Voltage Power Complexity Reliability Size
Push/Pull Solenoids 3VDC 3W low high d = 25.5mm h = 28.9mm
Electromagnets 12VDC ? low high d = 35mm h=~45mm
Motor System
Motor 12VDC 58 RPM low high d =6.3 mm
Belt System N/A N/A high med custom
Sealing Options for Autoclave
Pressure Sealing
Pressure Plug N/A N/A low high custom
Push/Pull Solenoid 3VDC 3W low high d = 25.5mm h = 28.9mm
High Torque Motor TBD TBD low high d = 127mm h = 127mm
Belt System N/A N/A high med custom
Magnetic Sealing
Electromagnets 12VDC ? high high very large
High Compression Spring N/A N/A high low custom
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Mixing Design-To Requirements
Requirement #
Title Requirement Importance
PDD 4.5
Reaction Chamber Mixing Capability
Each reaction chamber shall have mixing capability such that each geological sample is evenly distributed within the fluid while movement is present at each sensor location.
The fluid must be mixed so that the sensor readings are as accurate as possible. The fluid must also move at each sensor so that the boundary layer around the sensors is broken down, which is necessary to get a reading.
PDD 4.28Unit Disassembly
MiDAs shall be able to be taken apart so that it may be sterilized and reassembled for multiple Earth tests.
The instrument needs to be reusable.
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Mixing Options
• Mixing applications– Soil in reaction chambers must be stirred
• Electrochemical sensors need fluid movement to function
• Prevents sedimentation to soil
• Criteria (order of importance)1. Volume2. Power usage3. Risk4. Cost
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Mixing Option Pros and Cons
ProsCons
Ultrasonic-BioServe may provide
-Does not disrupt ISE’s
-Ruptures cell membranes above 18 kHz
-Expensive
-Lack of prior experience
Magnetic
-No known machining required
-Does not require probe through top or bottom of reaction chambers
-ISE interference pending test
-Magnetic Martian soil
Mechanical
-Known flow-pattern
-Does not disrupt ISE’s
-Common use / more experience
-Soil could clog mechanism
-Most COTS mixers are too large
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Mixing Options
Volume Cost Power
Ultrasonics PCB: 5" x 2 3/4" x 1" $1295* variable
Probe: 0.850" diam, 4 1/2" long
Probe tip: 1/8" diam x 2" long Ti
alloy
Magnetic 4.8” x 4.8” x 1.8” Unknown
Mechanical 0.8 mm diameter impeller Unknown
74
Power Supply Design-To Requirements
Requirement #
Title Requirement Importance
PDD 4.24 Field PowerMiDAs shall provide its own power (between 10 W and 30 W) in a field setting.
MiDAs shall provide its own power (between 10 W and 30 W) in a field setting.
PDD 4.25Laboratory Power
MiDAs shall be capable of receiving between 10 W and 30 W from an external power supply in a laboratory setting.
The instrument needs to be capable of running in a lab, as well as the field.
PDD 4.26Nominal Power Consumption
Nominal power consumption shall not exceed 30 W.
This is based on estimates of the Mars astrobiology rover
PDD 4.27Peak Power Consumption
Peak power consumption shall not exceed 30 W for more than 30 seconds.
This is based on estimates of the Mars astrobiology rover
PDD 4.29Operational Cycle
One operational testing cycle shall be 14 standard Earth days, not including power-up, sterilization, and power-down.
This is the time given for the potential life to reproduce and metabolize.
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Power Supply Options
Mass (kg) Volume (cm3)
Cost Power Provided
Time for Delivery
Fuel Cell 1.133 637 $1769 30W @ 12V
3-4 Weeks
Sealed Lead Acid Battery
30 10577 $165 40 hrs, 30W @ 12
V
2-3 Weeks
Lithium Ion Battery
8 4800 $40 30 W @ 12V
2-3 Weeks
Dual Junction Solar Cells
0.118 kg (does not include
backing)
Area = 30 cm2
$940 (to charge)
30 W @ 12 V
2 Weeks
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Data Acquisition Design-To Requirements
Requirement # Title Requirement Importance
PDD 4.4 Reaction Chamber Sensor Capability
Each reaction chamber shall be capable of supporting no fewer than 6 and no more than 18 electrochemical sensors.
This is the number of electrochemical sensors that will be provided by the customer.
PDD 4.19 Sensor Data Collection RateThe electrochemical sensors shall have a data collection rate of 1 measurement per minute per sensor.
Since the experiment takes place over 14 days, a reading each minute from each sensor is sufficient to characterize the experiment results.
PDD 4.20 Sensor Data AcquisitionAll data taken through the sensors shall be collected and stored for analysis.
The data will be analyzed after the experiment is completed.
PDD 4.21 Sensor Data AccessibilityThe scientific and engineering status data shall be accessible to users throughout the experiment.
The customer would like to be able to look at the status of the experiment while it is in progress.
PDD 4.22 MiDAs Status WarningsMiDAs shall provide caution, warning, and instrument status to external ground support equipment.
This is necessary to be able to observe the status of the instrument, as well as detect errors.
PDD 4.23 MiDAs CommandMiDAs shall receive commands from external ground support equipment.
The duration of the experiment is such that it is not reasonable to have the user initiate each step of the process.
PDD 4.29 Operational Cycle
One operational testing cycle shall be 14 standard Earth days, not including power-up, sterilization, and power-down.
This is the time given for the potential life to reproduce and metabolize.
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Data Acquisition Options
• Data acquisition applications:– Must be able to give commands to
sensors, heaters, and soil transport– Must be able to store data with a
collection rate of one sample per sensor per minute
• Criteria:– Power usage– Cost
78
Data Acquisition Options
DAQ Cards
model power price Weight Width Length Height Resolution Memory Time
LabJack UE95 V or by
USB cable$429 --- 75mm 185mm 30mm 16 bit ---
2 week shipping
LabJack U3by USB cable
$99 --- 75mm 115mm 30mm 12 bit ---2 week shipping
Embedded CPU with DAQ
Athena 10 W $825 150 g 4.175" 4.45" --- 16 bit 128 MB2 week shipping
Poseidon 3.5 W $995 --- 4.528" 6.496" --- 16 bit 256 MB2 week shipping
Elektra 5.5 W $750 108 g 3.55" 3.775" --- 16 bit 128 MB2 week shipping
Hercules 12 W $500 285 g 8" 5.75" --- 16 bit 128 MB2 week shipping
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Data Acquisition Pros and Cons
Pros Cons
Data Acquisition Card
-Self powered (draws power from computer)
-Requires additional hardware
Embedded CPU w/ Data Acquisition
-Embedded system
-Can provided variety of data transfer options
-Can be used to store data until testing complete
-Can provide accessibility to autonomous control
-Requires additional power consumption
-Expensive
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Pressure and Temperature Sensor Options
• Pressure and temperature sensor applications:– One of each sensor in the sterilization chambers
capable of withstanding high temperature– One of each sensor in the each reaction
chamber– One temperature sensor in the reagent water
chamber• Criteria:
– Cost– Power usage– Temperature range
81
Temperature Sensor Pros and Cons
Pros Cons
Thermocouples
-Variety of types and configurations
-Low cost, wide availability
-Reliable
-Self-powered
-Can handle autoclave temperatures
-Requires a cold junction compensator for calibration
-Sensor accuracy can reach 1°C at temperatures between 10°C and 40°C
Thermistors-Better accuracy than thermocouples and RTDs
-Loss of linearity
-Requires shielding from high temperatures
-Requires current
Resistance Temperature
Detectors (RTD)
-High accuracy
-Excellent stability and reusability
-Can be immune to electrical noise
-Requires shielding from high temperatures
-Requires current to take measurements
82
Temperature Sensor Options
Thermocouples Volume
Model Cost Weight Diameter Length Temp Range
Operation Range
Accuracy (1-40 °C)
Time
5SRTC-TT (mini connector)
$54 (5 pack)
--- 0.51mm 1m T --- ±1 °C2 day shipping available
TJ36 (autoclave probe)
$92 --- 1.6mm 1m JKTE --- ---2 day shipping available
Thermistor
44005 $15 --- 2.8mm 60mm-80 to 250 °C
--- ±1 °C2 day shipping available
RTD Height Length Width
SA1-RTD $50 --- 25mm 2m 19mm-73 to 260 °C
--- ±0.5 °C2 day shipping available
CJC Height Length Width
MCJ-T (battery included)
$99 57 g 13mm 75mm 25mm T 10-45 °C ---2 day shipping available
CJ-T (battery included)
$170 75 g 12mm 75mm 49mm T 10-50 °C ---2 day shipping available
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Pressure Sensor Pros and Cons
Pros Cons
Gauge-Widely available
-Relatively cheap
-Measures pressure relative to standard atmosphere
Absolute
-Measures pressure relative to vacuum
-Widely available
-Relatively cheap
-Requires additional sensors to measure local conditions
Differential-Measures difference between two locations
-Slightly more expensive than gauge and absolute
84
Pressure Sensor Options
Pressure Sensors Volume
Model Cost Weight Height Length WidthTemp Range
PowerAccuracy ***
Time
PX138 * $85 --- 26.2mm 28.1mm 27.9mm0 to 50
°C8VDC
0.1% 0.5%
1 week shipping
PX139 * $85 --- 26.2mm 28.1mm 27.9mm0 to 50
°C5VDC @2 mA
0.1% 0.5%
1 week shipping
PX140 * $120 --- 26.2mm 28.1mm 27.9mm-18 to 63 °C
8VDC0.75 % 0.15%
1 week shipping
Diameter Length
PX209 ** $195 --- 12mm 57.9mm -54 to 121 °C
24VDC @ 15 mA
0.25% 0.25%
1 week shipping