Speed of Sound Experiment Pre-CDRTeam BalloonWorks
Table of Contents
• Introduction• Mission Goal• Expected Outcomes• Mission Requirements
• Payload Design• Electrical, Software, and Mechanical Design
• Risk Management
Introduction
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.
Mission Requirements
• Team BalloonWorks and the payload shall comply with all LaACES requirements.• The payload shall measure the speed of sound in
ambient atmospheric conditions in order to construct a profile of the speed of sound versus altitude.• The payload shall obtain temperature, pressure
and humidity to verify the data gathered on the speed of sound.• Team BalloonWorks shall retrieve and analyze data
post flight.
Payload Design
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• Main Components• BASIC Stamp• RTC• EEPROM• Transmitter• Receiver• Test Circuit
• Driver• Op-amp• Comparator• Flip-Flop• Oscillator• 2 Stage Counters• I/O Expander
• Power Supply
Test Circuit• Driver• Op-amp• Comparator• Flip-Flop• Oscillator• 2 Stage
Counters• I/O Expander
Power Budget• 5 V input to all components after regulation• Maximum supply currents• 4 hours time
Component Current (mA) Charge (mA-hours)BalloonSat 100 400Comparator 6 24Flipflop 100 400Clock 25 100Counter 1 70 280Counter 2 70 280I/O Expander 125 500Total Needed 496 1984
Power Supply• 8 Energizer Ultimate Lithium AA Batteries in series to output
12 V to the BalloonSat and test circuit.• Both BalloonSat and test circuit require 5 V. BalloonSat has a
voltage regulator (U3). Test circuit will have a voltage regulator.• U3 and test circuit’s voltage regulator will need to be in
parallel with the batteries.• Every component in the test circuit will need to be in parallel
with the test circuit’s voltage regulator but not with the batteries.
Power Supply• Per Battery: 500 mA, 2000 mA-hrs
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
Write_To_EEPROM Sub-Routine
Write_To_EEPROM Sub-Routine Get_Time Sub-Routine
Switch the set pin on the Flip-Flop from high to low and then
back to high
Is EEPOM ADDR>=max
EEPROM Address
Send a 40kHz pulse
Comparator_Status Sub-RoutineCounter Sub-Routine
Reset the counters
Pause in order to maintain consistent data acquisition of
every fifteen seconds
End Program
Yes
No
Flight Program
Write address to the EEPROM on the BASIC Stamp
Flight Program-SubroutinesGet_Time: Counter:
Transmit to Stamp
Bring RTC pin high
Turn RTC and SCLK pins low
Write_To_EEPROM:Comparator_Status:
Turn RTC pin back to low
I2COUT command
Return
I2CIN command
Enter DO loop
Pause
Return
Pause
I2COUT command
Return
Loop
Return
Yes
No
Comp=1
Post-Flight Program
Run the term232 program to save data into a file
Display the data showing the address as well as the values
Use the I2CIN command to retrieve the data for the
EEPROM
Pause
Is EEPOM ADDR>=max
EEPROM Address
End Program
Yes
No
Mechanical Design• Purpose of Mechanical Design• Hexagonal Design• Extruded polystyrene rigid foam
insulation material
Experiment Chamber and Circuitry Chamber Design
Circuitry Embracement and Battery Holder Design
Top Cover
Weight Budget
Components Weight ApproximationPayload Structure 130gBalloonSat Circuit Board 70g
Testing Circuit Board 70gBatteries 115gSupports 30g
Total 415g
Risk Management