Transcript Pre-CDR Presentation

Speed of Sound
Experiment Pre-CDR
Team 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
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BASIC Stamp
RTC
EEPROM
Transmitter
Receiver
Test Circuit
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•
Driver
Op-amp
Comparator
Flip-Flop
Oscillator
2 Stage Counters
I/O Expander
• Power Supply
Test Circuit
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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
BalloonSat
Comparator
Flipflop
Clock
Counter 1
Counter 2
I/O Expander
Total Needed
Current (mA)
100
6
100
25
70
70
125
496
Charge (mA-hours)
400
24
400
100
280
280
500
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
Flight Program
Read the address from the
EEPROM on the BASIC Stamp
Is EEPOM
ADDR>=max
EEPROM Address
Yes
End Program
No
Write_To_EEPROM SubRoutine
Get_Time Sub-Routine
Switch the set pin on the FlipFlop from high to low and then
back to high
Send a 40kHz pulse
Counter Sub-Routine
Comparator_Status Sub-Routine
Write_To_EEPROM SubRoutine
Reset the counters
Pause in order to maintain
consistent data acquisition of
every fifteen seconds
Write address to the EEPROM
on the BASIC Stamp
Flight Program-Subroutines
Get_Time:
Turn RTC and
SCLK pins low
Comparator_Status:
Enter DO loop
Bring RTC pin
high
Transmit to
Stamp
Turn RTC pin
back to low
Comp=1
No
Loop
Return
Return
Counter:
Write_To_EEPROM:
I2COUT
command
I2COUT
command
I2CIN command
Pause
Pause
Return
Yes
Return
Run the term232 program to
save data into a file
Post-Flight Program
Is EEPOM
ADDR>=max
EEPROM Address
No
Use the I2CIN command to
retrieve the data for the
EEPROM
Display the data showing the
address as well as the values
Pause
Yes
End Program
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 Approximation
Payload Structure
130g
BalloonSat Circuit Board
70g
Testing Circuit Board
70g
Batteries
115g
Supports
30g
Total
415g
Risk Management