Skillz That Killz
Critical Design Review
Jocelyn Mulkey, Jess Davidoff, Kaitlyn
Zimmitti, Taylor Smith, Travis Dowdy,
October 8, 2009
To investigate both the benefits and cost s of generating energy with solar at
Solar cells use photons as light energy to create electricity
We would like to determine if encapsulated monocrystalline solar cells
generate more electricity at higher altitudes as a result of clearer and more
Purpose of Our Experiment:
Answer the question: Could solar cells replace batteries in future
If this is true, future BalloonSat missions may not be constrained by battery
life, weight and volume
Our results may also increase knowledge about solar energy
Could help answer the question: Is installing solar panels to airplanes to
power them a feasible solution to reducing their carbon footprints?
• Goal (G1)
– Our BalloonSat shall rise to an altitude of roughly 30 kilometers in order
to perform a scientific experiment that will measure the energy output of
solar cells at altitudes higher than ground level so as to better
understand the ability of these cells to generate more electricity at
higher altitudes as a result of clearer and more intense light.
• O1 (comes from G1)
– Assemble BalloonSat in order to advance our understanding of solar
energy at an altitude of 30 kilometers for under $100 by 11/07/2009.
• O2 (comes from G1)
– Determine altitude by measuring tilt in one axis.
• O3 (comes from G1)
– Establish a function of altitude to find the correlation between altitude
and solar energy.
Level 0 Require ments
0.Obj1 The team shall construct the BalloonSat and complete testing by O1
10/29/09. Testing shall occur in appropriate locations as the BalloonSat is
being built to ensure each system is in working order, and construction of
the BalloonSat shall cost under $100. Testing and construction shall last
for approximately 24 days.
0.Obj2 After flight, altitude shall be determined using the data from the
0.Obj2 After flight, altitude shall be determined using the data from the O2
accelerometer. The data retrieval and analysis shall take 20 days
maximum and shall occur in the Discovery Learning Center.
0.Obj3 After flight, solar energy shall be measured as a function of altitude using O3
the data from the accelerometer (0.Obj2) and the data from the solar cells.
This analysis shall take less than 20 days and will also occur in the
Discovery Learning Center.
Level 1 Require ments
1.Sys1 All aspects of the BalloonSat system shall be compatible and have the O1
capability to function correctly with each other.
1.Sys2 The BalloonSat system shall establish the tilt from 10 to -10 degrees with O2
a precision 0.5 degrees, with a goal of 0.1 degrees.
1.Sys3 The BalloonSat system shall determine the voltage from each solar cell O3
and record the data on the AVR Microcontroller in volts.
17 centimeter cube
Double-layer foam core, secured with hot glue, aluminum tape, and Velcro, if necessary
We will have a small Plexiglas window on one side to protect the camera's lens during flight.
We will have a solar cell on each side of the cube placed into an inset in the foam core
The solar cells are monocrystalline and encapsulated (no further protection needed from
Six solar cells will be connected to an 8-input multiplexer inside the cube, which will direct the
analog input from each cell to one input on the AVR Microcontroller board.
The multiplexer is necessary because we only have four available inputs on the AVR, but six
solar cells from which to collect data.
The AVR will record the voltage from each solar cell. Because the AVR records data in volts,
and the solar cells output in volts, there will be no need to convert the data after retrieval
other than with the Data Parser Utility. When we are retrieving our data, we will use the
utility to convert the data from binary to voltages.
Other hardware pieces
AVR Microcontroller board (to record data from temperature, altitude, air pressure, and voltage
from solar cells)
Heater system (temperature control to protect hardware)
Digital camera (to record pictures from the flight)
Multiplexer (to take the voltage inputs from all 6 solar panels and channel them into one input
on the AVR)
Four 9V batteries, foam core, Velcro, hot glue, insulation, a non-metal flight string tube, extra
wire, MUX, test batteries, and dry ice.
(All of these materials are provided or are in the SpaceGrant inventory except for the solar cells
and the MUX, which will be purchased from Sundance Solar and West Florida Components,
and the test batteries and dry ice, which will be paid for by our team and purchased from
The reason for placing a solar cell on the four sides of the cube is to ensure there is always light
reaching at least one cell.
The bottom cell
– May collect photons reflected from the ground (especially if snow is present), and, when
high enough, reflected from the clouds
– We will draw conclusions from our data if this is true.
Cube – 17 × 17 × 17 cm
9V Batteries (4) – 19.2 × 10 × 6 cm
AVR Microcontroller – 2 × 8 × 11 cm
Canon Digital Camera – 4.5 × 7.5 × 9 cm
Heater System – 1× 5 × 5 cm
HOBO – 6.8 × 4.8 × 1.9 cm
Functional Block Diagram
Item Where to get it Cost Wight
AVR Microcontroller and Provided $0 150 g
Heater system and Provided $0 100 g
Foam Core Provided $0 108 g
Insulation Provided $0 TBD
Switches Provided $0 20g
Flight String Tube Provided $0 TBD
Canon Digital Camera Provided $0 220 g
Monocrystalline Solar Cells Sundance Solar $69.40 42 g (6 cells)
8-Input Multiplexer West Florida Components $26.78 TBD
Plexiglas (9x7.5 cm) Space Grant Inventory $0 64 g
Resistors (if needed) SGI $0 Not required at this time
Velcro SGI $0 Not required at this time
Aluminum Tape SGI $0 <1 g
Hot Glue SGI $0 16 g
Extra Wire SGI $0 Not required at this time
Test Batteries and Dry Ice Safeway Approx $35 (cost covered N/A
TOTAL $96.18 (not including cost Total of Known: 721 g
covered by team) Weight allowed for
unknowns: 129 g
Team Meetings: All Tuesdays at 2:00 p.m.
Design complete 9/20/09
Complete Proposal 9/15/09
Proposal Due 9/17/09 6 p.m.
Conceptual design review 9/ 22/09 8 a.m.
Program AVR 9/27/09
Order all hardware 9/29/09
Foam Core Structure Built 0/05/09
Critical design review 10/06/09 8 a.m.
DD Rev A/B due 10/06/09
Structure Testing – Drop/Whip Tests 10/06/09 2 p.m.
Prototyping design complete 10/13/09
Experiment Testing 10/14/09
Subsystem Testing (Heater/Solar Cells) 10/14/09
Testing final design complete 10/20/09
Cold Test 10/20/09
Functional Test – Heater, Camera 10/20/09
Camera/Imaging Test 10/20/09
Subsystem Test 10/20/09
Pre-Launch Inspection (Bring hardware) 10/27/09
Mission simulation tests (bring B.Sat) 10/29/09
Launch Readiness Review 11/03/09 8 a.m.
DD Rev C due 11/03/09 8 a.m.
BalloonSat Weigh-in and Turn in 11/06/09 2 p.m.
DLC 270 A and FRR Cards Due 11/06/09
Launch Day!!! 11/07/09 4:45 a.m.
Experimental Testing •Place BalloonSat in sun for same amount of time as
•Rotate B.Sat to simulate spin during flight
•Record voltage input from solar cells and temperature
Test Plans (to test temp effects on cells)
•Retrieve and analyze data from cells and temp sensor
•Make sure input from solar cells does not exceed 5V
limit and install resistors if needed
Structural Testing • Whip test (determine force of flight will not destroy
or weaken structure)
• Drop test (determine burst/landing will not destroy
• 4-story drop + kick down stairs
• Cold Test (placed in a cooler of dry ice for ~2 hours
to simulate temperatures during flight)
Functional/Subsystem Testing •Test correctness of software codes
•Test camera’s ability to turn on
•Test heater’s ability to keep B.Sat above (-10°c) for ~2
•Test all subsystems work together and that power
input/output does not exceed 5V
Mission Simulation Testing In class mission simulation
Camera/Imaging Testing Test camera to ensure
•Images/videos are being recorded
•Images/videos are clear
•Determine if Plexiglas obstructs images
Test Completion Date
Experiment Testing 10/14/2009
Structural Testing 10/6/2009
Functional/Subsystem Testing 10/20/2009
Mission Simulation Testing 10/29/2009
Camera/Imaging Testing 10/20/2009
The purpose of our mission is to determine the advantages of generating energy
with solar cells at altitudes other than ground level. We hope to discover if solar
cells are more beneficial when at higher altitudes.
Expected Results: To either show increased energy as altitude increases or
show negligible difference in energy input.
To retrieve data: Connect AVR board with data to computer and use Data
Retrieval Utility to retrieve data from board.
To read data: Use Data Parser Uttility to transform data from binary to
voltages which we can use to analyze data
To organize data: Use Excel where we can then interpret and draw conclusions.
These graphs indicate what our data for the four side cells should look like, whether the payload is
spinning, if it is stationary, or a combination of the two circumstances. The data from the top and
bottom cells will not be affected by spin so they are not included in the graphs.
If the payload rotates, each reading should provide about the same average voltage reading over the
course of the flight:
If the payload starts rotating and ends in a static condition, we should see several of the cell's data
drop-off and only one or two cells producing current:
If there is no or minimal rotation we should only see in the data two cells providing current:
The data of the voltages of each solar cell will allow us to determine which solar cell was facing the sun
(or snow, for the bottom cell) at what time. The voltage data of the cell facing the sun will be higher
than the others. This will help us to visualize the attitude of the satellite throughout the flight.
In order to determine altitude from the air pressure data, we will use the equation
p =101325 (1 - 2.25577 10-5 h) 5.25588 where p = air pressure (Pa) and h = height above
sea level (m).
Team Member Title Secondary Title Additional Responsibilities
Jocelyn Mulkey Programming/ Science Functional Testing
Schedule Mission Simulation Testing
Jess Davidoff Power/ Budget/Reporting Camera Testing
Team Leader Presentations
Kaitlyn Zimmitti Budget Software Mission Simulation Testing
Taylor Smith Structure Design/ Power Functional Testing
Testing Leader Satellite Recovery
Travis Dowdy Science Programming Experiment Testing
Hunter Hoopes Software Structure Design Functional Testing
Flight weather conditions
Voltage input from cells
Effects of temperature on