Transcript CDR

Harding Flying Bison RockSat-C 2012 Team
Critical Design Review
Harding University
Bonnie Enix, Joshua Griffith, Will Waldron,
Edmond Wilson, David Stair
28 November 2011
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Mission Overview
Bonnie Enix
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Mission Overview – Mission Statement
Design, build, test and fly a spectrometer that will measure
visible and near-infrared spectra of gases in Earth’s
atmosphere at lower altitudes and the Sun’s irradiance at
high altitudes
Tabulate and interpret spectra and create a technical report
summarizing the results obtained and conclusions reached
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Mission Overview – Mission Requirements
Requirements
1. An optical port is mandatory
2. An adequate, stable and reliable power supply
3. A robust, responsive G-Switch
4. A sensitive, rugged spectrometer operating in the 200 – 1000 nm
wavelength range
5. A photodiode sensitive to the same wavelengths as the
spectrometer
6. A microprocessor with two programmable clocks, high speed
analog to digital converters, and memory to store the acquired
spectra
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Mission Overview – Mission Requirements
Requirements - continued
7. Power distribution board to allocate the correct voltages and
currents to each device requiring power
8. Signal conditioning board to insure the electrical inputs and
outputs between the sensors and the microprocessor match in
terms of voltage ranges, currents and impedances
9. Software program to operate the payload
10. Mounting hardware for the payload that will withstand the g-forces
imposed during testing and flight and will not interfere with the
Frostburg State University payload
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Mission Overview – Science Questions
Science questions to be answered:
1. What atoms and molecules can be identified in the spectra
acquired by our spectrometer during the flight?
2. What are the concentrations of these substances?
3. Can the lineshapes of the oxygen and water spectra be used to
reveal the altitude, temperature and number density of each gas?
4. Is this spectrometer system accurate, sensitive, useful and robust
enough to be deployed on future Solar System missions?
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Mission Overview – Benefits and Use of Results
This project fits into a larger program to build a suite of spectrometers
to be deployed on a mobile robotic vehicle on the surface of Mars
The spectrometers will be used to detect, measure, and pinpoint the
location of biomarker gases on Mars (if they exist) and to gain new
information about the atmosphere of Mars to evaluate regions of
habitability for human exploration
Successful completion of this mission will provide a heritage for the
spectrometer as we move up the TRL ladder seeking approval for
inclusion of this instrument on a future Solar System mission
A comprehensive technical report will be created and an oral summary
prepared for presentation at a technical meeting
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Mission Overview – Concepts
With the spectrometer located inside the Earth’s atmosphere,
the Sun’s light can be used as the optical light source in obtaining
transmission spectra of Earth’s atmosphere
I0
I
Computer with
Data Storage
Spectrometer
Atmospheric Gases
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Mission Overview – Concepts
Once above Earth’s atmosphere, the spectrum of the Sun’s surface
can be measured without interference.
I0
Computer with
Data Storage
Spectrometer
Sun
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Mission Overview – Concepts
The spectrometer measures atmospheric spectrum through optical port
in rocket airframe using Sunlight as the source. Any gases that absorb
radiation in the 200 to 1100 nm range will contribute to the acquired spectra.
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Mission Overview – Concepts
Percent of atmosphere below rocket as a function of flight time.
The flight will be above the atmosphere for about half the flight.
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Mission Overview -- Concepts
We can definitely measure
water and oxygen!
Spectrum of Earth’s atmosphere at sea level over a 10 km path. Water (green) and oxygen
(blue) dominate the atmospheric spectrum in the region of 200 to 1080 nm -- the range of
our instrument. Spectrum created from HITRAN 2008 Database and HITRAN-PC software.
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Mission Overview – Concepts
oxygen
water
Spectrum of Earth’s atmosphere at 297 ft. above sea level measured with flight
spectrometer. Water and oxygen peaks are clearly visible. Blue trace made with
spectrometer pointed to bright clear sky away from Sun. Red trace made with instrument
pointed directly at the Sun
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Mission Overview – Theory
Transmittance of light through a sample obeys the Beer-Lambert Law
I0(ν)
I0(ν)
I (ν)
I (ν)
Sample
Spectrometer
Intensity of radiation incident on the sample
Intensity of radiation of frequency,
, after passing through sample
Absorption Cross Section at frequency,
N
L
, cm2/molecule
Number of absorbing molecules per volume
Sample path length
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Mission Overview – Concept of Operations
Altitude
t ≈ 1.7 min
Apogee
Altitude: 95 km
t ≈ 2.8 min
t ≈ 4.0 min
Altitude: 95 km
Altitude: ≈115 km
t ≈ 1.3 min
t ≈ 4.5 min
Altitude: 75 km
Altitude: 75 km
t ≈ 0.6 min
t ≈ 4.8 min
Altitude: 52 km
End of Orion Burn
Rocket re-enters
Rocket above atmosphere
atmosphere
When G-switch activates payload, spectra will be measured at a
frequency of 2.0 Hz producing 1200 spectra in 10 minutes
0 min
Altitude: 52 km
t ≈ 5.5 min
Chute Deploys
t ≈ 15 min
Time
Splash Down
G switch triggered -- All systems on -- Begin data collection
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Mission Overview – Expected Results
G-Switch will function properly to turn on electronics
Batteries will be sufficient to power the payload for 20 minutes
Instrument will perform well and at least 100 useable spectra will be
recorded, 50 in the atmosphere and 50 above the atmosphere
Concentrations of water vapor and oxygen will be measured as a
function of altitude
Ozone will be measured at higher altitudes
Other atmospheric pollutant gases may be detected
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Design Description
Will Waldron
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Mechanical Design Elements
Microcomputer
G- Switch
Electronics board
Spectrometer
Photodiode on top
Light gathering lens on bottom
SolidWorks rendering of spectrometer payload mounted in top
half of canister using optical port to right of wire-way as viewed
from top or bottom of rocket.
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Mechanical Design -- Spectrometer
Light enters spectrometer through fiber optic cable in the front of the instrument,
goes through a slit and strikes the round mirror facing front. From there the light is
directed to the diffraction grating (mounted on hemi-cylinder) which diffracts the
light onto the collimating mirror on the left of the instrument and then to a CCD
array detector. A plastic filter in front of the CCD array removes unwanted
spectral orders
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Mechanical Design Elements
Cut away portion of payload diagram showing spectrometer mounted on main
mounting plate and with cover removed from spectrometer. Fiber optic cable also
removed. Spectrometer has no moving parts and is mounted in a sturdy aluminum
optical bench.
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Mechanical Design Elements
Spectrometer payload occupies exactly half the vertical space of the canister.
In order to mount all the components, two aluminum mounting plates are required.
One-half inch stainless steel standoffs are used to secure the payload to the top
of the canister using 8-32 stainless steel socket head cap screws.
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Mechanical Design Elements
TERN Model EL Microprocessor with
2 gigabyte compact flash memory
G-Switch
Battery compartment
holding five 9-volt alkaline batteries
View of 1/8 inch thick top mounting plate with components.
Electronics board is mounted under the microprocessor board.
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Mechanical Design Elements
Side view of payload showing positioning of spectrometer with attached fiber
optic cable. Fiber optic cable is terminated with light collecting lens aimed at
rocket viewport. Photodiode is mounted above light collecting lens. Batteries,
G-switch, microprocessor and electronics board mounted on secondary plate.
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Mechanical Design Elements
Changes since PDR:
The only change since PDR is the decision to leave off the
accelerometers from the payload.
The purpose of the accelerometers was to provide accurate
knowledge of the rocket view port direction at each instance
of the rocket flight.
It was realized that obtaining this information would require time
and effort beyond our time budget.
The same information can be obtained from the flight data
WFF will record during flight.
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Electrical Design – Overall Schematic
We have not completed our detailed schematic at this time.
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Electrical Design – G-Switch Circuit
We have decided to use the RockOn workshop G-switch
circuit. We have studied the schematic for it and are making
inroads into exactly how it works.
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Software Design
The program starts with a power-on reset on
microprocessor.
The initial real time clock reading is taken and
stored to determine the length of time for the
data collection.
Begin iterations by storing the real time clock,
photodiode reading and 2048 pixels of the
CCD Linear Array.
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Software Design – Major Inputs and Outputs
Timing diagram for spectrometer operation. Top two traces show timing relations
for the two clocks that clock the data out of the spectrometer. Bottom trace is the
2048 pixel data output for one complete spectrum. Two DACs are need for clocking
and two ADCs are required to read the spectrometer and photodiode sensors for
each clock cycle.
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Prototyping/Analysis
Joshua Griffith
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Prototyping Results
Our prototyping is being carried out by exhaustive SolidWorks modeling of our
payload.
The spectrometer has been operated and spectra of the sky have been recorded
successfully
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Prototyping Results -- Mass
Mass Budget
Subsystem
Total Mass (lbf)
Main Al Plate
1.57
Secondary Al
Plate
0.37
Spectrometer
2.37
Batteries
0.50
Battery holder
0.34
Microprocessor
0.15
Electronics Board
0.20
Fiber Optic Cable
0.13
Standoffs
0.34
Total
Over/Under
5.97
Under 0.68
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Prototyping Results -- Power Budget
Power Budget
Subsystem
Microprocessor
CCD Array
Photodiode
Voltage (V)
9
5
0
Current (A)
0.250
0.010
0
Time On (min)
Total (A*hr):
Over/Under
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Amp-Hours
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0.063
15
0.003
15
0.00
0.063
Under 0.937
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Prototyping Results
Mass, volume and power analysis
The total allowed mass for a canister including its payload is 20.0 lbf.
The canister has a mass of about 6.7 lbf.
If the remaining mass is divided equally between two teams, each team
will have 6.65 lbf.
Our payload has a mass of 5.97 lbf.
We have ample room for mounting our instrument and power supply in the
volume allocated (1/2 canister)
Our energy requirements can be amply met with several 9 VDC batteries.
Our current consumption is 260 mA. One 9 VDC battery would last 1.25 h
at this drain rate
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Manufacturing Plan
Will Waldron
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Manufacturing Plan
Items to be constructed:
9 in. x 0.25 inch circular aluminum plate
9 in x 0.125 inch circular aluminum plate
G-switch brackett
Battery holder for 5 9-volt batteries
All other items have already been acquired
Manufacturing of the above four items will be done in January/February
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Electrical Elements
Items to be manufactured
Cable to connect spectrometer CCD array electronics to power and to
Microprocessor
Connections between battery stack, G-switch, WFF RBF wires,
Microprocessor and spectrometer
G-switch circuit
All items to needed for electrical circuits are in place
Manufacturing of these items will take place in January/February
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Software Elements
No computer code has been written at this time
We are working on learning to use the TERN Development System software
to carry out analog to digital and digital to analog conversion and data
storage and retrieval.
It is estimated that most of January – April 2012 will be needed to perfect the
software.
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Testing Plan
Will Waldron
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System Level Testing
Tests have already been successfully carried out with the spectrometer
And these tests will continue until we have completed a successful flight
simulation test.
The G-switch circuitry will be tested many times once the electronics
board is fabricated.
After the software becomes somewhat operational, testing of the
Instrument under a variety of sunlight/cloudy conditions will proceed until
the instrument can respond satisfactorily to a wide range of sky conditions.
Power supply testing will be carried out to insure the instrument has an
adequate amount of current/voltage capability plus a reserve.
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Software Testing
Testing of the system to produce the two clock timing pulse trains required
will be carried out by feeding the output pins of the two DACs to a two-channel
oscilloscope to evaluate the frequencies, voltages and synchronous behavior
desired.
Testing of the system to acquire the voltages produced by the two sensors,
the photodiode and the CCD array, will be carried out by first feeding the
outputs of these two transducers to an oscilloscope to make sure the signals
to be measured are actually being produced as well as what the voltage
and frequency ranges are.
Then the software will be tested to see if this same data can be read in via
the two ADCs to the memory on board the microprocessor and then read out
into a spreadsheet file.
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Risks
Josh Griffith
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Risk Walk-Down
Consequence
Entire mission fails
Entire mission fails
Partial Mission failure
G-Switch doesn’t
activate electronics
Batteries drain before
end of flight
Little to no data
collected
Once above clouds,
measurements will be
successful
Microcontroller has Sunlight too low due
malfunction
to cloud cover
Possibility
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Risk Walk-Down
Risks:
•
•
•
•
•
G-switch malfunction
Batteries drain early
Microprocessor not started
Cloud cover to thick
Sun too low on horizon
Mitigation:
•
Testing the system with many
trials is the only reasonable
way to minimize failure
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User Guide Compliance
Bonnie Enix
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User Guide Compliance
•
Mass of payload plus canister is 13.4 lbf
•
CG within 1”x1”x1” envelope? – Information not available yet
•
Batteries? 5 9-Volt Alkaline, non rechargeable batteries
•
One optical port required
•
G-switch activation at time of launch is the method chosen
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Sharing Logistics
•
We are sharing our canister with Frostburg State University
•
Plan for collaboration
We communicate by e-mail and RockSat-C website
We will send a copy of our CDR to Frostburg and request a copy of
their CDR
•
We plan to joining our payload to Frostburg’s with stainless steel standoffs.
grandpmr.com
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Project Management Plan
Bonnie Enix
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Project Management – Organizational Chart
Bonnie Enix
Software &
Testing
Joshua Griffith
Software &
Testing
Edmond Wilson
Mentor &
Logistics
David Stair
Technician &
Graphic Artist
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Will Waldron
Hardware &
Electronics
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Project Management Plan
Task – February 2012
Week 1 Week 2 Week 3 Week 4
◊
G-Switch Implementation
◊
Compression Testing of Plates
& Standoffs
Power Distribution System
◊
Constructing 2 Aluminum Plates
◊
Interfacing Controller to
Spectrometer
◊
Making and Producing Reports
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Project Management Plan
Task – March 2012
Week
1
Construction of Brackets &
Fixtures to go on mounting
plates
Week
2
Week
3
◊
Spring
Break
Week
4
Week
5
◊
Assembling Payload
Mechanical
Spring
Break
Interfacing Controller to
Spectrometer
Spring
Break
◊
Reporting and Making
Reports
Spring
Break
◊
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Project Management Plan
Task – April 2012
Week
1
Week
2
Week
3
Week
4
◊
Testing Fully Integrated
System In Laboratory
◊
Using Atmosphere Models
To Predict Results
Carry Out Vacuum Tests
◊
Carry Out Temperature
Tests
◊
◊
Outside Testing
Mass & Center of Gravity
Week
5
◊
◊
Making And Producing
Reports
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◊
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Project Management Plan
Task – May 2012
Day in the Life Testing #1
Week
1
Week
2
Week
3
Week
4
◊
◊
Day in the Life Testing #2
◊
Outside Testing of Payload
◊
Final Testing of Electrical
Shorts
◊
Final Testing of Center of
Gravity and Mass
Making And Producing
Reports
Week
5
◊
◊
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◊
◊
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Project Management Plan
Task – June 2012
Week
1
Final Inspections,
Integration and Testing
◊
Making And Producing
Reports
◊
Travel to Wallops Island
◊
Week
2
Week
3
Week
4
Week
5
◊
Visual Inspections at
Wallops Island
◊
Vibration Tests and
Integration at Wallops
Island
◊
◊◊◊◊◊
Launch Day!
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Project Management – Budget
Item
Amount
Canister & Fees
7000
7000
Travel & lodging for launch week
1800/person
7200
Student Fellowship
8 weeks at 40 hr/wk
4000/student
12000
Materials & Components
1500
Total
Total
1500
$27,700
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Conclusion
We believe we have a good workable plan.
Our mentor has two years of experience in this program.
We are looking forward to progressing rapidly starting at the beginning of
the spring semester.
We will be working on software familiarization and construction over the
Holiday break.
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