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Speed of Sound
Experiment CDR
Team BalloonWorks
March 29th, 2012
Table of Contents
• Introduction
• Mission Goal
• Expected Outcomes
• Payload Design
• Electrical, Software, and Mechanical Design
• System Testing
• Pre Flight Checklist
• Data Analysis Plan
• Master Budget
Mission Goal
To measure the speed of sound in Earth’s
atmosphere in order to establish a relationship
between speed of sound and altitude up to 30,480
meters and to consider the effects of atmospheric
properties on the speed of sound.
Expected Outcomes
• Speed of sound is primarily dependent on
temperature.
• Speed of sound will decrease until the balloon
reaches the tropopause.
• Speed of sound remain constant in the
tropopause.
• Speed of sound will increase in the stratosphere.
• Humidity is expected to play a minor role in
determining the speed of sound when compared
to temperature changes.
Principle of Operation
• Ultrasonic transmitter will emit an ultrasonic pulse.
• Receiver will detect the pulse after it travels through ambient
air.
• Test circuit will determine the time it takes for the pulse to
travel the fixed distance between transmitter and receiver.
• Payload will have both an experiment and circuitry chamber.
• Experiment chamber will allow temperature inside to be equal to
ambient temperature and will contain the transmitter and
receiver.
• Circuitry chamber will be closed to the environment and will hold
the power supply, test circuit, and BalloonSat.
System Design
Electrical Design
Electrical Design
Electrical Design
Electrical Design
Software Design
• Pre-Flight Program
• Sets all hardware pins and variables
• Sets EEPROM address
• Sets RTC
Initialize all hardware
pins and declare all
variables
Initiate EEPROM address
to 0
Set RTC to desired
HH:MM:SS
Display
Read the address from the
EEPROM on the BASIC Stamp
Is EEPOM
ADDR>=max
EEPROM Address
Yes
End Program
No
Write RTC data to EEPROM
Get hour, minute, and second
from RTC
Start the counter to count until
the arrival of the pulse
Send a 40kHz pulse
Get counter data
Check comparator status
Write counter data to EEPROM
Reset the counters
Pause in order to maintain
consistent data acquisition of
every fifteen seconds
Write address to the EEPROM
on the BASIC Stamp
Post-Flight Program
Run the term232 program to
save data into a file
Is EEPOM
ADDR>=max
EEPROM Address
No
Retrieve the data for the
EEPROM
Display the data showing the
address as well as the values
Pause
Yes
End Program
Mechanical Design
• Hexagonal Design
• Extruded polystyrene rigid foam
insulation material
Mechanical Design
Units in mm
Weight Budget
Components
Weight
Payload Structure
165g +/- 5g (Measured)
BalloonSat Circuit Board
70g +/- 0.5g (Measured)
Testing Circuit Board
60g +/- 5g (Measured&Apptoximated)
Batteries
115g +/- 0.5g (Calculated)
Supports
60g +/- 5g (Approximated)
Total
470g
System Testing
• Wind Test
• Determine whether the mechanical design would effectively
block the wind effects on speed of sound
• Air Blower, Oscilloscope, Test Circuit, Prototype Box
• Successful
• Vacuum Test
• Determine the maximum altitude the receiver can detect the
ultrasonic pulse
• Vacuum Chamber, Oscilloscope, Test Circuit
• Successful to 29,410 m
System Testing
System Testing
• Temperature Test
• Determine whether the experiment chamber maintains
a thermal equilibrium with the surroundings.
• Two HOBOS with temperature probes and prototype box
• Successful
• Electronics Test
• Prove that the test circuit can store the counts to the
EEPROM and that the post flight software can retrieve
the counts.
• Test Circuit, Pre/Flight/Post software, PC.
• In progress
System Testing
Pre Flight Checklist
• Calibration: Sync RTC time with the LaACES GPS beacon time
the morning of the launch.
Time (min)
Procedure
5
Fresh batteries installation and perform
voltage checks
5
Load preflight and flight software
5
Secure test circuit and BalloonSat slider to
the payload
10
Close top cover and secure payload to
strings
Total=25
Data Analysis Plan
• Post Flight Software will retrieve the data stored during flight.
• Excel will:
• Convert the counts to decimal numbers.
• Multiply by 1/f of the timing oscillator (10 MHz) to obtain the
time the sound pulse took to get from the Tx to the Rx
• Divide 0.19 m by the above time to get speed of sound.
• Obtain temperature, pressure, and relative humidity data from
Team Flyboys.
• Obtain altitude vs. time data from LaACES.
• Construct graphs of speed of sound vs. altitude.
• Construct graph of measured speed of sound vs. theoretical
speed of sound.
Master Budget
Quantity
1
1
2
2 and 10
1
1
1
1
2
36
1
Total
Price
Expected
Arrival
CD4011UBE
CD4049UBE
255-400SR12M-ROX
Precision resistor Z201 and capacitor
E4941
$0.38
$0.52
$5.24
$41.74
0
0
0
4/2
AD822ANZ
LM311N
MXO45T-3C-10M0000
MCP23017-E/SP
SN74HC590AN
Energizer Ultimate Lithium AAA Batteries
$6.54
$0.56
$2.31
$1.44
$0.66
$80.1
0
0
0
0
0
4/2
$170.00
$309.49
4/2
Description or Part Number
Test Circuit PCB Board