Colorado Space Grant Consortium, The University of Colorado at
Boulder Department of Aerospace Engineering Sciences, and the
Edge of Space Sciences
BalloonSat Missions to the
Edge of Space
Team Solkraft Revision D
Thomas Buck, Kyle Garner, Alexandra Jung, Quinn McGehan,
Mark Sakaguchi, and Scott Taylor
Fall 2010
BalloonSat Mission to the Edge of Space
Design Document Revision D
1.0 Mission Overview .............................................................................................................. 3
2.0 Requirements Flow Down ................................................Error! Bookmark not defined.
3.0 Design ................................................................................................................................ 5










3.1 Strucutre
3.2 Thermal
3.3 Electronics and Data Collection
3.4 How Team Solkraft Will Achieve Their Mission
3.5 Data Retrieval
3.6 Features
3.7 Illustrations
3.8 Block Diagram
3.9 Parts List
3.10 RFP Requirements
4.0 Management ..................................................................................................................... 13

4.1 Schedule
5.0 Budget .............................................................................................................................. 15

5.1 Budget Management
6.0 Test Plan and Results ....................................................................................................... 16

6.1 Safety
7.0 Expected Results .............................................................................................................. 20
8.0 Launch and Recovery ...................................................................................................... 20
9.0 Results, Analysis, and Conclusions ................................................................................. 22



9.1 Flight Data
9.2 Ground Tests
9.3 Summary
10.0 Ready for Flight ............................................................................................................. 28
11.0 Conclusions and Lessons Learned ................................................................................. 29
12.0 Message to Next Semester ............................................................................................. 29
References ............................................................................................................................... 29
Bios ......................................................................................................................................... 30
2
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
1.0 MISSION STATEMENT
The mission of team Solkraft is to test the effectiveness of monocrystalline and polycrystalline
solar panels under near space conditions up to approximately 30 km. This will test the solar cells
under varying light intensities, temperatures and altitudes. Team Solkraft shall analyze the
electrical output of the solar panels to see which type is more effective in a near space
environment.
1.1 OVERVIEW
With a planet on the verge of destruction from global warming, the research into alternative
energy sources is more important than ever before. One of the most prominent developments
made over the past decade is innovative ways to capture energy from the Sun. The use of solar
panels on households and businesses has become a popular way to offset energy costs and their
potential for the future is even more optimistic. Solar cells are becoming more and more
efficient. The National Renewable Energy Lab (NREL) set the record for the world’s most
efficient solar cell in 2008 at 40.8%1. Because it is the belief of Team Solkraft that solar cells
will become the main source of energy for generations to come, our mission strives to pinpoint
the variables that effect solar cell output, specifically in a near-space environment.
The near space environment will provide insights into solar cells being used for stratospheric
platforms. Stratospheric platforms are vehicles that operate very high in the atmosphere. These
are most commonly thought of for communication relays and access points to provide large areas
with wireless broadband. Current stratospheric platforms are run off of fuels or batteries and can
only operate for short periods of time. Team Solkraft hopes to explore the possibility of whether
using solar panels on stratospheric platforms is a viable option to keep it flying for a longer
period of time or even indefinitely.
There is lots of testing of solar cells on the ground and data on how normal ground temperatures
affect solar cells. It seems to be agreed upon that under conditions on the ground solar cells
decrease in efficiency with an increase in temperature.1 However, there is much less exploration
of how solar cells operate under the more extreme conditions of a near space environment.
Team Solkraft shall test how well two different types of solar cells (monocrystalline and
polycrystalline) function at different altitudes with varying light intensities and under different
temperatures. As a control for the experiment the solar cells will be tested under different
temperatures on the ground at a constant altitude before the launch day. The solar panels will be
tested on similar weather days with different temperatures and similar temperature with different
cloud cover that will provide different light intensities.
From this initial testing of the solar cells Team Solkraft will compare this data to the data we
receive on launch day to see which factor, light intensity or temperature, affects the solar cells.
3
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
To plot the effectiveness of the solar cells versus altitude we will use data from the GPS attached
to the weather balloon after getting approval from EOSS. Light intensity shall also be measured
using photodiodes to see how that affects the functionality of the solar cells. Team Solkraft is
doing this to analyze the effects of near space on monocrystalline and polycrystalline solar cells.
From the information acquired Team Solkraft will decide which type of solar cell is more
efficient in a near space environment.
2.0 MISSION REQUIREMENTS
To give the mission the best possible prerequisites to succeed certain requirements need to be
fulfilled. Below is the Mission Objective, the Level 0 requirements which come off the Mission
Objective and at last the Level 1 requirements which come off the Level 0 requirements. The
Level 1 requirements state the actions necessary to complete/fulfill the Level 0 requirements.
The relationship between a requirement and its parent requirement (or Mission Objective) is
stated in the last column of our table.
OBJECTIVE
The mission of Team Solkraft is to test the effectiveness of different types of solar panels
(monocrystalline and polycrystalline) under conditions on the ground and up to near-space
conditions of approximately 30 km.
MISSION REQUIREMENTS LEVEL 0
Requirement Requirement
Number
M 0.1
The solar panels on the BalloonSat shall be exposed to nearspace conditions
M 0.2
Team Solkraft shall measure the internal and external
temperature with varying altitude
M 0.3
Team Solkraft shall measure the light intensity with varying
altitude
M 0.4
Team Solkraft shall test for variations in solar cell output
under varying climate conditions
M 0.5
Team Solkraft shall meet the requirements for the request for
proposal
M 0.6
Team Solkraft shall make sure no one is hurt during
construction and testing
Where it comes
from
Mission
Objective
Mission
Objective
Mission
Objective
Mission
Objective
MISSION REQUIREMENTS LEVEL 1
4
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
Requirement Requirement
Number
M 1.1
The solar panels shall be attached to the angled sides of the
BalloonSat
M 1.2
Team Solkraft shall be able to record the altitude of the
BalloonSat using data from EOSS GPS
M 1.3
Team Solkraft shall be able to record and save data during the
flight
M 1.4
Team Solkraft shall maintain a minimum internal temperature of
-10 degrees Celsius.
M 1.5
Team Solkraft shall program the Arduino microcontroller to
record solar cell output data to a micro SD card
M 1.6
Team Solkraft shall take in-flight pictures using a Canon
A5701S camera and save them to the camera’s 2 GB memory
card.
M 1.7
Team Solkraft shall record science data to the Arduino
Microcontroller
M 1.8
Team Solkraft shall build a structure for the BalloonSat capable
of withstanding near space conditions
Where it
comes from
M 0.1 M 0.4
M 0.2, M 0.3
M 0.2, M 0.3,
M 0.4
M 0.5
M 0.2, M 0.3,
M 0.4
M 0.5
M 0.2, M 0.3
M 0.4
M 0.1, M 0.5
3.0 DESIGN
3.1 STRUCTURE
To achieve our goal of measuring the functionality of solar panels in a near space environment
we will mount eight solar panels on the exterior of a BalloonSat. Four of these cells will be
monocrystalline and four will be polycrystalline. The frame of the BalloonSat will be a square
pyramid with the top cut off so that the 3D structure is formed using four trapezoidal pieces of
equal size, one larger square as the base, and one smaller square as the top. This structure will be
made out of foam core cut from a single piece in order to help the structural integrity. We will
use hot glue and aluminum tape to secure the structure. The structure of the BalloonSat will be
attached to a weather balloon using 2.4mm Dacron line by running the line vertically through a
non-metal tube at the center. The structure of the BalloonSat will be set in one place along the
cord by tying a figure-eight knot in the line at the top and bottom of the BalloonSat. We will also
put an American Flag on the BalloonSat to identify it.
3.2 THERMAL
5
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
In order to keep our experiment warm during the flight the satellite will be insulated with foam.
In addition to this we will use a heater on the inside of BalloonSat powered by three 9V batteries
to help keep the internal temperature of the BalloonSat above -10oC.
3.3 ELECTRONICS/DATA COLLECTION
Data from the solar panels will be recorded using an Arduino Microcontroller hooked up in a
circuit with the eight solar panels. We will be able to record all of the solar panels through two
analog inputs by using a sixteen channel multiplexer. The multiplexer will alternate from which
solar panel the Arduino is taking data. It will do this every half second however, so we do not
need to worry about the time difference as a factor in our data. The voltage will also be recorded
with a load on the circuit created by a resistor that is not very affected by temperature to make
sure that is not affecting the results of our experiment. Through doing this we can find the power
output on the resistor.
The measurements for the temperature will be taken by a HOBO data logger with the internal
temperature sensor and an external temperature. This will allow the data to be easily taken off of
the data logger and onto a computer for easy evaluation. We will also use four thermistors
connected to the Arduino Microcontroller through a multiplexer to record temperature on each
side of the BalloonSat. To measure the light intensity we will use a photodiode on each face of
the BalloonSat that the solar cells will be on. The data for which will be recorded by our Arduino
Microcontroller again using the multiplexer and then going to an analog input. In addition to the
data we collect using sensors on our satellite we will also collect altitude data from the GPS
attached to the weather balloon at the end of the flight string after getting permission from
EOSS.
3.4 HOW TEAM SOLKRAFT WILL ACHIEVE OUR MISSION
First we will look at the structure of our satellite. Team Solkraft will design the sides of our
pyramid structure to fit four of the solar cells which are 76mm x 83mm x 6mm, one on each side.
Team Solkraft will then cut out a template of the satellite out of foam core and assemble the
structure using hot glue and aluminum tape. Before integration of the solar panels into the
structure Team Solkraft shall first test each one by connecting them to a voltmeter and testing
each one under different amounts of light to be sure that they are working. The next step is to
integrate our solar cells by soldering the positive side to a resistor and then attaching a lead to
that resistor going to the multiplexer input. The negative side will be connected to the ground of
the microcontroller. The microcontroller will turn the analog signals into digital and give a
voltage reading of the solar cells. Also along the outside of the satellite we will mount a
photodiode on each side to measure light intensity positioned between the two solar cells. This
will help us determine which solar cell is facing the sun based on the intensity and we will use
that specific panel’s voltage reading. We will then start mounting the components on the inside
of the satellite such as the heater, HOBO, and camera. After learning how to solder in class,
6
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
Team Solkraft will assemble the heater and place it in the satellite ensuring that when the
BalloonSat passes through the tropopause that the circuits remain at an operable temperature.
Next the camera will be mounted to the BalloonSat. The camera is programmed to take pictures
approximately every 20 seconds. Team Solkraft will cut out a hole for the lens in one of the
sides; this will ensure ventilation to the satellite to help prevent any condensation build up.
Insulation will also surround the lens from the side back to the camera so that the rest of the
satellite is still insulated keeping the heat in. Our HOBO will have its external temperature
sensor mounted through another hole in one of the sides of the satellite so we will have a
comparable internal and external temperature reading.
3.5 DATA RETRIEVAL
Team Solkraft BalloonSat will have an Arduino microcontroller to record the voltage output of
the solar cells. This data will then be transformed from an analog to digital signal to be logged
and stored for later collection on either the flash memory of the microcontroller or an external
memory card hooked up to the USB port of the microcontroller. Therefore, the means of data
retrieval will involve transferring the data from the microcontroller to a computer for processing
after the BalloonSat has returned to the ground.
The photodiode sensors will also produce a voltage based on the light intensity and the amount
of voltage from those sensors will correspond to the light intensity. Team Solkraft will record
this in the Arduino microcontroller.
The data will then be analyzed as voltage output as a function of altitude, and also temperature
recorded by the thermistors because they are closest to the solar panels for the most accurate
reading. The altitude data will be retrieved from the GPS attached to the flight string, and the
external temperature will be taken from the HOBO logger onboard our BalloonSat. It will then
be possible to determine the efficiency of the cells as a function of altitude and temperature. The
data analysis will be done using Excel.
3.6 FEATURES
Photodiodes
Photodiodes will measure the light intensity from the sun and convert it into voltage that will be
read by the microcontroller. Team Solkraft will use this to determine specific measurements for
the light intensity as it changes throughout the flight.
Solar Panels
7
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
The solar panels are our experiment. With them Team Solkraft will determine what affects their
functionality in a near space environment. We will also see which type is more effective.
Structure
The structure will allow Team Solkraft to use the solar cells more efficiently because they will be
more directly angled towards the sun. The trapezoidal shape will also help the structural integrity
when the BalloonSats land because all of the parts inside the BalloonSat will give it a lower
center of gravity making it more stable and less likely to land on a side damaging a solar cell.
3.7 PICTURES
8
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
This is the original layout of the Balloon Satellite. Some changes were made to the layout.
Changes




The Arduino microcontroller was moved to the sidewall instead of on the bottom
Only one battery was required for the Arduino so there are now only 4 batteries total
The heater was moved more toward the center of the satellite. It was placed on the
bottom of the satellite near the flight tube
The batteries were laid flat against the bottom of the BalloonSat
Camera
Heater
220 mm
Batteries
128 mm
220 mm
90 mm
HOBO
Arduino
110 mm
9
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
3.8 BLOCK DIAGRAM
3 9V
Batteries
Batteries
Switch
Switch
Heater
2 GB Memory
Card
Camera
HOBO
Power
Photodiodes
Switch
Polycrystalline
Solar Cells
Provided
Hardware
Sensors
Thermisters
Multiplexer
Solar Cells
Battery
Switch
Arduino
328
Monocrystalline
Solar Cells
2GB Micro
SD Card
10
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
3.9 FINAL PARTS LIST
Part and where it is from
Six Monocrystalline solar panels from
Edmund’s Scientific
Fourteen Polycrystalline solar panels
from The Electronic Goldmine
Six Photodiodes from West Florida
components
Arduino Duemilanove Microcontroller
Starter Kit from Sparkfun Electronics
9V to barrel jack adapter from Sparkfun
Electronics
5 Thermistors from Sparkfun Electronics
Micro SD Shield from Sparkfun
Electronics
Multiplexer breakout board from
Sparkfun Electronics
Foam core from Colorado Space Grant
Insulation from Colorado Space Grant
Canon A5701S from Colorado Space
Grant
HOBO Datalogger from Colorado Space
Grant
Heater from Colorado Space Grant
9V Batteries from Colorado Space Grant
Reference
http://www.scientificsonline.com/lowcost-high-output-encapsulated-solarcells.html
http://www.goldmine-elecproducts.com/prodinfo.asp?number=G1
6397
http://www.westfloridacomponents.com
/mm5/merchant.mvc?Screen=PROD&St
ore_Code=wfc&Product_Code=LED06
0&Category_Code=
http://www.sparkfun.com/commerce/pro
duct_info.php?products_id=9952
http://www.sparkfun.com/commerce/pro
duct_info.php?products_id=9518
http://www.sparkfun.com/commerce/pro
duct_info.php?products_id=250
http://www.sparkfun.com/commerce/pro
duct_info.php?products_id=9802
http://www.sparkfun.com/commerce/pro
duct_info.php?products_id=9056
Part #
3039808GRP
G16397
LED060
DEV-09952
PRT-09518
NTCLE100
E3103JB0
DEV-09802
BOB-09056
3.10 HOW TEAM SOLKRAFT WILL MEET THE RFP REQUIREMENTS
1. Design shall have additional experiment(s) that collects science data and teams must
analyze this data.
Team Solkraft additional experiment will collect data as voltage readings from solar
panels that Team Solkraft are testing. See 1.0 Mission Overview and 3.0 Design
2. After flight, BalloonSat shall be turned in working and ready to fly again.
Team Solkraft will make sure the BalloonSat is able to withstand the rigors of flight
through testing. See 6.0 Testing
3. Flight string interface tube shall be a non-metal tube through the center of the
BalloonSat and shall be secured to the box so it will not pull through the BalloonSat
or interfere with the flight string. (See flight string attachment diagram at the end of
this document.)
11
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
See 3.1 under Design
4. Internal temperature of the BalloonSat shall remain above -10˚C during the flight.
Team Solkraft will use a heater and insulation to keep the BalloonSat above -10oC. See
3.2 under Design.
5. Total weight shall not exceed 850 grams.
Team Solkraft will budget our weight and plan so that our experiment shall not exceed
850 grams. See 3.0 Design and 5.0 Budget.
6. Each team shall acquire (not necessarily measure) ascent and descent rates of the
flight string.
Team Solkraft shall get permission from EOSS to use the data from the attached GPS.
7. Design shall allow for a HOBO H08-004-02 (provided)
See 3.0 Design
8. Design shall allow for external temperature cable (provided)
See 3.0 Design
9. Design shall allow for an Canon A570IS Digital Camera (provided)
See 3.0 Design
10. Design shall allow for an active heater system weighing 100 grams with batteries and
id 10x50x50mm (provided). Dimensions do not include 2 x 9 volt batteries.
See 3.0 Design
11. BalloonSat shall be made of foam core (provided).
See 3.0 Design
12. Parts list and budget shall include spare parts.
See 5.0 Budget.
13. All BalloonSats shall have contact information written on the outside along with a
US Flag (provided).
Team Solkraft will put US Flag and contact information on bottom of satellite.
14. Proposal, design, and other documentation units shall be in metric.
Yes
15. Launch is in November 6, 2010. Time and location: 6:50 AM in Windsor, CO.
Launch schedule will be given later. Everyone is expected to show up for launch.
Only one team member is required to participate on the recovery. Launch and
recovery should be completed by 3:00 PM.
Team Solkraft will all plan ahead to be at launch.
16. No one shall get hurt.
See 6.1 Safety under Testing
17. All hardware is the property of the Gateway to Space program and must be returned
in working order end of the semester.
Team Solkraft shall make sure the BalloonSat is able to withstand the rigors of flight
through testing. See 6.0 Testing
18. All parts shall be ordered and paid by Chris Koehler’s CU Mastercard by
appointment to minimize reimbursement paperwork. All teams shall keep detailed
budgets on every purchase and receipts shall be turned in within 48 hours of
purchase with team name written on the receipt along with a copy of the Gateway
order form (HW 04).
See 5.0 Budget
12
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
19. All purchases made by team individuals shall have receipts and must be submitted
within 60 days of purchase or reimbursement will be subject to income taxes.
See 5.0 Budget
20. Have fun and be creative.
Will do.
21. Absolutely nothing alive will be permitted as payloads, with the exception of yellow
jackets, mosquitoes, fire ants, earwigs, roaches, or anything you would squish if you
found it in your bed.
Nothing on our satellite will be alive.
22. Completion of final report (extra credit if team video is included)
4.0 MANAGMENT
Scott Taylor
Team Lead
Structure Lead
Science Assist
Kyle Garner
Power Lead
Internal Testing
Data Analysis
Thomas Buck
Science Lead
Science Testing
Structure Assist
Quinn
Mcgehan
Electrical Lead
Internal Testing
Programming
Assist
Alexandra Jung
Budget/Planning
Lead
Structure Testing
Electrical Assist
Mark
Sakaguchi
Programming
Lead
Science Testing
Data Analysis
4.1 SCHEDULE
Team Solkraft will have a team meeting every Tuesday and Thursday at 6:00 PM. Extra
meetings will be organized or rescheduled as needed. The meetings will always take place in the
ITLL building in a reserved study room.
Date
9/20/10
9/21/10
Tasks
All Hardware needed addressed
Hardware Order Form processed
10/1/10
10/5/10
10/6/10
10/8/10
Design complete
Revision A/B Due
Start Construction finish prototype
Start Testing (Whip Test, Drop Test,
Kick Test)
Was this met
Yes
Yes, but needed to order extra
multiplexer when original one broke
Yes
Yes
Yes
Yes
13
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
10/09/10
10/11/10
10/12/10
10/14/10
10/19/10
10/21/10
10/25/10
Acquire all hardware and materials
Finished with all structure testing
Initial Programming of Arduino
Start Construction of Electrical systems
Start Interfacing of systems
Test Electronics
BalloonSat. Built
10/26/10
10/29/10
10/29/10
Final Critique
Simulation Test
All testing complete
11/1/10
11/2/10
11/5/10
11/6/10
11/8/10
11/30/10
12/4/10
12/7/10
Troubleshooting complete
Revision C due
BalloonSat Weigh-in and Turn in
Launch Day
Post-launch Data Review Complete
Final Presentations
Revision D due
BalloonSat Hardware Turn In
Yes
Yes
Yes
Yes
Yes
Yes
Not finished this day, but almost
completely finished during this week
Done later in the week
Yes
Did some ground tests after finishing
completion during the following week
Yes
Yes
Yes
Yes
Yes
Yes
Yes
5.0 BUDGET
Name
Purpose
Canon A5701S
Camera
HOBO Datalogger
Take Pictures
Mass
(g)
220
Cost
Measure/record
68x48x19
temperature and humidity
30
Provided Space Grant
Monocrystalline
Solar Panels (6: 4
used, 2 extra)
Polycrystalline Solar
Panels (6)
Photodiodes (6)
Experiment
42x41x6
6
$4.95
(each) (each)
Experiment
57x29x6
5
Heater
Maintain internal
temperature
Provide Power
10x50x50
100
48x25x15
Amazon.com
Record voltage readings
from solar cells and light
intensity readings from
photodiodes
Power Microcontroller
69x53
34
~ $3
(each) (each)
40
$59.95
10
Sparkfun
9V Batteries (4+extra
for tests)
Arduino
Duemilanove
Microcontroller
9V to barrel jack
Dimensions
(mm)
45x75x90
Measure light intensity
4
Where We get
it
Provided Space Grant
Edmund’s
Scientific
$1.49
(each)
$.40
The Electronic
Goldmine
West Florida
Components
Provided Space Grant
$2.95
Sparkfun
electronics
14
Team Solkraft
BalloonSat Mission to the Edge of Space
adapter
Switches
Connecting Wires
Resistors
Thermistor (5 one
comes with Arduino)
Micro SD Shield
16 Channel
Multiplexer (1)
Multiplexer breakout
board (1)
Foamcore
Shipping
Totals
Design Document Revision D
Turn on/off electronics
Provided Spacegrant/with
Arduino
Provided With Arduino
Provided With Arduino
Integrate electronics
Set up circuit for solar
panels
Record Temperature
Can put micro SD card
into Arduino for extra
memory
Make additional readings
with analog inputs on
Arduino
Structure of satellite
5
$1.95
Sparkfun
10
$16.95
Sparkfun
8x9
$.95
Sparkfun
40x18
$4.95
Sparkfun
53x52
(see diagrams)
163
793
Provided Space Grant
~$20
$176.54
**For those which dimensions and mass are blank, are not sure yet how much/many it will be,
but Team Solkraft believe it will not put us over the weight limit.
5.1 BUDGET MANAGEMENT
The budget will be managed by Alexandra Jung. Team Solkraft will keep an up to date account
of spending and plan for what the experiment will need so that Team Solkraft does not go over
budget. Right now Team Solkraft has a large surplus in the budget and we will try to keep a
surplus in case there is anything the experiment need to order at the last minute such as a
replacement part of something that has been forgotten.
6.0 TESTING
Team Solkraft will make testing a priority to insure that every component will successfully
contribute to the overall mission. Team Solkraft will start by making sure that the structure is
capable to handle the stresses exposed during takeoff, burst, and landing. Team Solkraft shall do
this by performing several structural tests on a similarly massed dummy satellite. The dummy
satellite will have rocks inside of the structure of similar mass to the components but will not
necessarily be in the exact position the components will be in.
1. Kick Test-The dummy was kicked down a flight of stairs to test overall strength.
15
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
Structure held well during test with only minor damages to the corners of the BalloonSat.
2. Drop Test-The dummy was dropped two stories from the ITLL second story balcony to
insure the structure is capable of handing the stresses related to various landing scenarios.
The BalloonSat remained intact except from minor damages to the foamcore because the
structure landed on the flight tube. Team Solkraft anticipates that this will not be a
problem because there will be other satellites above and below on the flight string so
there will be no direct impacts as seen in the test.
3. Whip Test-The dummy was swung about a string to test the strength of vulnerable points
on the spacecraft, such as the flight string tube, corners/joints, and access points. This
also tested whether our system to keep the BalloonSat attached to the flight string was
strong enough. This will simulate the forces exerted on the satellite during burst.
This test was successful with the flight tube withstanding the forces.
16
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
Secondly, Team Solkraft will perform various tests on the internal components of the spacecraft.
The tests to be performed include:
1. Freeze test- This test will simulate the radical temperature changes Team Solkraft’s
payload will go through on its journey to near-space. In this test, Team Solkraft will put
our fully functional satellite into a cooler with dry ice. To correctly simulate mission
conditions, the payload will be left in the cooler for a little over an hour. The data taken
during the cold test will only be temperature data due to the fact that there will be no light
in the cooler.
2. Data tests- Team Solkraft will perform tests to verify that all systems are functioning
correctly and the spacecraft is capable of taking data. To simulate this, Team Solkraft
shall power up the payload as if it were launch day, and expose it to various
environmental conditions to insure the HOBO is collecting and logging data correctly. If
any issues arise, we will test individual components to make sure they are working
properly.
17
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
Voltage Readings of Solar Cells by Arduino
0.12
0.1
Voltage
0.08
0.06
Monocrystalline
0.04
Polycrystalline
0.02
0
0
-0.02
5
10
15
20
25
Time (s)
Data from a general systems test in low light. Readings are from one side of the BalloonSat. At
Time~12 seconds the BalloonSat was moved into the shade. A corresponding drop was seen so
we know both solar cells are giving correct readings. Also from this test we can see that the
monocrystalline cells have a consistently higher voltage at a constant temperature on the ground.
3. Camera/imaging tests- These tests insured that our camera was working properly and is
ready for launch day. This was accomplished by setting the programming to trigger the
camera to start at certain intervals, and making sure those intervals are consistent
throughout the picture taking process.
We tested the camera outside and inside the satellite to ensure that the lens of the camera
was not obstructed inside. The final position of the camera gives us a clear picture
outside the satellite.
18
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
In addition, Team Solkraft will initiate tests on the experiment portion of their mission, to ensure
that the experiment is capable of operation throughout the flight. These tests include:
1. Control tests- Team Solkraft will perform different ground tests to serve as a control for
the experiment. For instance, because we are testing the variation of solar cell efficiency
in near-space conditions, one of our control experiments will be to expose the solar cells
to various temperature differences on the ground. This will enable us to possibly rule out
temperature as a variable in the efficiency in solar cell output, and move us toward
investigating other possible variables such as altitude.
Team Solkraft will also order extra parts to ensure that the payload is capable of flying on launch
day, regardless of the possible misfortunes our testing process may have on it.
6.1 SAFETY
Team Solkraft will do its best at maintaining the safety of its team members and all bystanders.
We will be sure to follow the safety instructions given to us when Team Solkraft starts soldering.
Through all of the testing Team Solkraft will use common sense. Also, for all tests at least two
team members will be present. For the drop test we make sure the drop zone is clear and give
the person dropping the correct signal to proceed. We will make sure the rope/wire is very
secure before starting the whip test and we will clear a safe radius from the person ‘whipping.’
The stair well and sides and bottoms of it will be clear of people before we start the stair test just
in case the satellite goes over the side. The hot glue gun will be operated very carefully and with
finesse. The glue will be given time to cool. The exacto blade will be handled with one hand
and with the other a good distance to the side. We will never operate it with rapid motions, just
slow careful cuts.
7.0 EXPECTED RESULTS
The monocrystalline cells will outperform the polycrystalline cells, while both cells will perform
better in a near space environment than on the ground. Monocrystalline cells are more expensive
to manufacture than polycrystalline, but monocrystalline cells are known to be more efficient
than polycrystalline when used on the ground.3
Team Solkraft expects that the solar cells will perform more efficiently in the near space
environment for a multitude of reasons. First, team Solkraft expects that the atmosphere
interferes with the light from the sun that hits Earth and causes the intensity of the light to
decrease as it goes through the atmosphere. Therefore, at higher altitudes the solar cells will
produce a higher voltage output because there is a higher light intensity. This was the case with
the control tests on the ground. This can be seen in the graph of voltage readings in section 6.0
under Data Tests.
Second, team Solkraft expects that the solar cells will function more efficiently at the colder
temperatures of near space because of the increase in the Carnot efficiency of the cell. This
19
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
happens because the temperature difference of the source of light, the sun, and the solar cell are
greater as the temperature of the solar cell and its surroundings decrease.3 More control test are
needed to determine how much temperature affects the voltage output of the solar cells. Team
Solkraft will perform more control tests in the days leading up to launch.
Team Solkraft expects that the lower temperatures and higher light intensities of the upper
atmosphere will affect the voltage output of the solar cells. If Team Solkraft’s assumptions are
correct that the lower temperatures will increase solar cell output the data will show a peak in
voltage as the BalloonSat goes through its coldest point, the tropopause. However, light intensity
is also a factor and from the data it can be determined whether the light intensity or temperature
affect it more based on whether the peak voltage is at the tropopause or at the maximum altitude.
8.0 LAUNCH AND RECOVERY
Launch Procedure
1. BalloonSat will be attached to flight string before launch day by Chris Koehler
2. HOBO will start recording automatically for 6:45 AM on November 6
3. Team Member A will flip switches to start the camera, heater and Arduino. (Camera
switch will be flipped back to “off” position after the wires have been short circuited to
start the camera and will therefore not be a drain on the battery)
4. Team Member B will hold Team Solkraft’s BalloonSat awaiting release of weather
balloon
5. As weather balloon is released Team Member B will move forward so a smooth launch
will be achieved
Recovery
1. Quinn McGehan will drive Team Solkraft to the recovery site
2. After recovering the BalloonSat the heater and Arduino switches will be turned off.
Data Retrieval
The science data will be recorded to a microSD card connected to the Arduino microcontroller.
The data will be in the form of a .txt file. In the data will be the time that has passed since the
microcontroller was turned on, the input of the multiplexer that the Arduino is currently taking
data, and a voltage reading. This file will then be opened in Excel. The programming of the
Arduino allows for tabs between each data value and a return after each line of data so that when
the file is imported into Excel it will be in three columns: time, input number, voltage. The data
can then be split up into each of the 16 inputs based on the input number in the second column.
The voltage will be given on a scale from 0-1023 which corresponds to 0-5V DC. The relative
voltage coming through the thermistors will change because the resistance changes based on the
temperature. The voltage from the photodiodes corresponds to relative light intensity. The
20
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
voltage output from the solar panels can be used to find their power output based on the
resistance of the circuit which we will know based on the resistor we connect.
The HOBO data will be stored on the HOBO’s internal memory and can be analyzed by using
Boxcar.
The pictures from the camera will be stored on the camera’s SD card.
LAUNCH DAY
Launch and recovery went well. We were able to retrieve most all of our data; one thermistor did
not work correctly, but other than that we were able to get data. At the launch site our satellite
sustained minimal damage. The structure was intact and there was only one polycrystalline solar
cell that a corner broke off.
9.0 RESULTS, ANALYSIS, AND CONCLUSIONS
Our hypotheses that the monocrystalline cells will outperform the polycrystalline, and that both
cells will perform better in near space than on the ground were both proven true by the data from
our experiment.
9.1 FLIGHT DATA
Below are graphs of the BalloonSat flight. They show voltage data from the two different types
of solar panels recorded by the Arduino. The voltage from all four sides of the BalloonSat were
averaged and plotted. The temperature data is an average from the three working thermistors on
the BalloonSat. The altitude data was obtained from the EOSS GPS.
From the graphs we can see that temperature corresponds very closely to voltage output. The
values on the axis for temperature are reversed to better show the correlation between a decrease
in temperature and an increase in voltage.
21
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
22
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
From the first two graphs we see that the temperature data and the voltage data points follow a
similar curve. As the temperature decreases, the voltage output from both the monocrystalline
and the polycrystalline solar cells increases. This correlation is best seen as the BalloonSat
travels through the tropopause on assent and descent. On ascent the BalloonSat travels through
the tropopause during the time 50-90 minutes and on descent passes through it again during time
160-170 minutes. This is the coldest point of the flight with the temperature reading -69.16
degrees Celsius. During these two time intervals the solar cells experienced the highest voltages
with the monocrystalline having a maximum of .675 V and the polycrystalline having a
maximum of .646 V. We concluded that temperature has a greater effect on the solar cells than
altitude because both types of cells follow the plot of the temperature data rather than the altitude
data. After plotting the voltage data from both the monocrystalline and polycrystalline we can
see that while both data plots follow similar curves, the monocrystalline solar cells had a higher
voltage output throughout the entire flight. This confirmed our hypothesis that the
monocrystalline solar cells would have a higher voltage output than the polycrystalline cells.
This is caused by monocrystalline cells, although more expensive, being made from a single
homogenous silicon crystal while polycrystalline cells are made from many smaller silicon
crystals. Because the single silicon crystal has no grain boundaries it becomes a more efficient
cell.
23
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
Temperature Data of The Balloonsat
40
20
0
Temperature (°C)
-100.00
0.00
100.00
200.00
300.00
400.00
500.00
HOBO Internal
-20
HOBO External
Thermistor
-40
-60
-80
Time (in minutes, time 0 is when thermistors were turned on)
Above is the temperature data from the flight. It shows the data from the HOBO’s internal (blue)
and external sensors (red). It also shows the average temperature data from our three working
thermistors (green). The thermistors were attached to the outer side of the BalloonSat so the
temperature stays generally between the temperature of the outer and internal temperature. In
general the internal temperature lags behind the thermistor temperature which lags behind the
external temp. This makes sense because it takes time to equilibrate from the outside temperature
to the internal.
24
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
Photodiode Voltage Output
10 per. Mov. Avg. (Series1)
0.8
0.7
Voltage Reading
0.6
0.5
0.4
0.3
0.2
0.1
0
0
50
100
150
200
250
Time (Minutes)
The photodiode voltage output was to be used to determine light intensity. However, it was
found that the photodiodes used on the balloonsat were too affected by temperature to get
accurate light intensity data.
25
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
9.2 GROUND TESTING
Monocrystalline Ground
Moved Solar Cells
out of direct
sunlight
Monocrystalline
Temperature
0.6
0
Output (V)
10
0.4
15
0.3
20
25
0.2
30
0.1
Temperature (celsius)
5
0.5
35
0
40
0
20
40
60
80
100
120
140
160
180
200
Time (min)
Polycrystalline Ground
Moved Solar Cells
out of direct
sunlight
Temperature
Monocrystalline
Polycrystalline
0.6
0
Output (V)
10
0.4
15
0.3
20
25
0.2
30
0.1
Temperature (celsius)
5
0.5
35
0
40
0
20
40
60
80
100
120
140
160
180
200
Time (min)
26
Team Solkraft
BalloonSat Mission to the Edge of Space
Moved Solar Cells
out of direct
sunlight
Design Document Revision D
Ground Comparison
Monocrystalline
Polycrystalline
0.6
0.5
Output (V)
0.4
0.3
0.2
0.1
0
0
20
40
60
80
100
120
140
160
180
200
Time (min)
Control Experiment-Ground Voltage Output (One
Solar Panel)
0.6
0.5
Voltage
0.4
0.3
0.2
Upper line is when side was directly in the sun. Lower
line is when this side was away from the sun.
0.1
0
10
15
20
25
30
35
40
Temperature (Degrees C)
From the ground tests it can be seen that temperature is directly relatable to voltage output. The
slope of the points in the graph directly above shows a very linear relationship between
27
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
temperature and voltage. The ground testing also shows that the monocrystalline cells
outperformed the polycrystalline during the ground tests as well as during flight.
9.3 SUMMARY
Our hypothesis that the solar cells would perform better in a near space environment than on the
ground was confirmed. The maximum voltages reached during ground testing were .567 and
.537 for the monocrystalline and polycrystalline cells respectively. These maximums are lower
than the maximums reached during flight which were discussed previously. While the conclusion
can be drawn that the cells are more effective at lower temperatures, it can not necessarily be
said that they are more effective at higher altitudes. The extremely low temperature experienced
in the tropopause is what led to the cells producing more voltage in near space than on the
ground. It is possible that the same voltages reached in near space could be reproduced on the
ground at similar temperatures.
10.0 READY FOR FLIGHT
Our main problems during the flight consisted of an internal temperature dropping below minus
ten degrees Celsius and one of our thermistors on the outside panel did not record proper
temperature readings. The internal temperature failure that the HOBO recorded was due to the
camera hole letting cold air inside the satellite. Although we put insulation surrounding the
camera lens to partition that inside section separate, this insulation did not prevent the inside
temperature reading from dropping below minus ten degrees Celsius. To correct this problem
for next flight we added additional insulation around the camera lens to keep the interior of the
satellite separated and protected from the camera hole that lets in cold air. To verify that this
corrected the problem, Team Solkraft conducted another cold test by placing the satellite in a
cooler filled with dry ice. When the HOBO internal temperature reading was recorded again the
internal temperature did not fall below minus ten degrees Celsius. The other failure in our
satellite was a faulty thermistor that did not record the external temperature during the flight.
We tested the thermistor with the multimeter and the sensor worked under different temperatures
by giving out different voltages. When then tested the connections of the thermistor to the
multiplexor that fed into our Arduino microcontroller and found there wasn’t a closed circuit.
After taking off the electrical tape that covered each junction of the wires we found that one
junction had come loose which caused our thermistor to not report any temperature data to
Arduino. Once this joint was fixed by re-soldering it we found the thermistor was working.
Team Solkraft’s BalloonSat should be stored in a dry, room temperature environment, in
a case that prevents the satellite from moving around. Any movement or collision to the sides of
the satellite could damage the sensors, especially the polycrystalline solar panel.
In order to activate the BalloonSat first both the micro SD and the SD card for the
Arduino and camera need to be wiped of all pre-launch data and pictures. Second, the HOBO
28
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
needs to be set and turned on to start recording at a specific time. Once all the components are
in, the satellite needs to be sealed by taping up the seams with aluminum tape. Right before
launch the switches for the camera, heater, and Arduino need to be turned to the on position and
then the satellite is ready for flight. Our payload will last if it is not launched within 6 months;
the only parts that might need to be changed would be the batteries for the camera, heater, and
microcontroller.
11.0 CONCLUSIONS AND LESSONS LEARNED
From the flight and resulting data, team Solkraft observed that the voltage output of solar
cells depends more on the temperature of the cell than the altitude that the cell is at. This
information points to the conclusion that solar cells would produce maximum voltage if placed in
low temperature environments such as the tropopause. An object (such as a stratospheric
platform) placed in the tropopause would be able to produce the maximum amount of power
from its solar cells. This means it could use more instruments simultaneously because of the
added power from the low temperature, allowing it to be more useful when placed at that
altitude.
Team Solkraft also learned the importance of organization. Due to the number of sensors
we had, wiring became a problem. Instead of taking our time to come up with an organized
method of wiring our instruments, we tried to get it down as fast as possible. The end result was
a mass of wire that made a lot of the space in our BalloonSat useless, and would have made any
repairs very difficult because of the difficulty following the wires. We have also learned a lesson
about teamwork. Working in a team is a very important skill to have, if the team cannot function
well then the whole project is put in jeopardy. The lesson that we learned about team work was
that not all team members are as dedicated as others, this left uneven amounts of work to be done
by each member, and a lack of trust between the members who were always at the meetings and
the ones who were not.
12.0 MESSAGE TO NEXT SEMESTER
This class will be one of the most rewarding and unique experiences of your education. Gateway
will give you an inside look into the life of an engineer through hands on experience. That being
said, this class is very difficult and very time consuming. Be prepared to learn entire new
concepts with little guidance in a very short amount of time. If you have the dedication then you
will get through it, but it will be challenging. Start early, work hard, and you will have the time
of your life.
REFERENCES
1. NREL http://www.nrel.gov/news/press/2008/625.html
2. Solar Server http://www.solarserver.com/knowledge/basic-knowledge/photovoltaics.html
29
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
3. Projects at the Solar Energy Group
http://www.physics.usyd.edu.au/app/solar/about/projects.html
BIOS
Scott Taylor
Scott is a freshman in Aerospace Engineering at University of Colorado at Boulder. He was
born August 29, 1992 in Boulder, CO. He likes to kayak and mountain bike in his free time. In
the future Scott hopes to work for NASA or a private space company with human spaceflight and
spacecraft propulsion.
Phone: 303-945-1488
Address: 9016 Crosman Hall. Boulder, CO 80310-0010
Email: scott.f.taylor@colorado.edu
Kyle Garner
Kyle is a freshman in Aerospace Engineering at the University of Colorado at Boulder. Born in
Longmont, CO, he enjoys the outdoors and playing video games when he has some extra time.
Kyle was actively involved in debate in high school, and enjoys judging at meets and helping out
the team however he can. In the future, Kyle dreams of working with NASA on human
spaceflight projects.
Phone: 720-210-8615
Address: 9012 Aden Hall. Boulder, CO 80310-0002
Email: kyle.garner@colorado.edu
Mark Sakaguchi
Mark was born on July 23, 1992 in Denver Colorado. He is a freshman at the University of
Colorado at Boulder and is studying Aerospace Engineering. Mark likes to play golf and is an
active member in the Japanese drumming group, Denver Taiko. In the future Mark wants to be
working for Lockheed Martin or working for NASA as an aerospace engineer.
Phone: 720-281-3545
Address: 9008 Andrews Hall. Boulder, CO 80310
Email: mark.sakaguchi@colorado.edu
Quinn McGehan
Quinn is a jovial fellow, who was born in Fairfield, California on April 25th 1992. He has been
raised almost completely in Boulder and attended Fairview High School. He currently attends
CU- Boulder, majoring in Aerospace engineering. He greatly enjoys ping-pong, sports, and
movies. Quinn wants to one day go to space himself, and in the future hopes to work for NASA.
30
Team Solkraft
BalloonSat Mission to the Edge of Space
Design Document Revision D
Phone: 303-877-7962
Address: 9057 Aden Hall. Boulder, CO 80310
Email: Quinn.mcgehan@colorado.edu
Anna Alexandra Jung
Alexandra is an international student from Copenhagen, Denmark from where she also has a
B.Sc. in astrophysics. She plans on doing her masters in aerospace engineering, which is why she
came to Boulder to get as much experience as possible within this field.
Born in Dragør just outside of Copenhagen on December 6th 1986, she has always aimed for the
stars and wanted to become an astronaut. The dream is still alive, but all she knows for sure is
that she wants to work with human spaceflight in one way or another.
Being a former elite athlete she enjoys swimming, skiing and athletics in general. Besides that,
music and socializing takes up a lot of her time. And she loves to travel, meeting new people and
learn about different cultures.
Address: 1024 Adams Cir Apt. F-224.Boulder, CO 80303
Phone: 720-278-4973
Email: anna.jung@colorado.edu
Thomas Buck
Thomas was born in San Antonio, Texas, but moved to Colorado when he was three. Thomas
went to Thomas Jefferson High School and decided to go to CU Boulder, because of the
Aerospace program, the campus and the people. He is a fun guy to hang around with and has a
good sense of humor. In his free time Thomas enjoys snowboarding, playing the guitar, shooting
some hoops and adventuring through Colorado’s vast and beautiful landscape.
Phone: 303-517-7760
Address: 9055 Aden Hall. Boulder, CO 80310.
Email: Thomas.buck@colorado.edu
31
Team Solkraft