Speed of Sound Experiment CDRTeam BalloonWorksMarch 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

Write counter data to EEPROM

Write RTC data to EEPROM Get hour, minute, and second from RTC

Start the counter to count until the arrival of the pulse

Is EEPOM ADDR>=max

EEPROM Address

Send a 40kHz pulse

Check comparator statusGet counter data

Reset the counters

Pause in order to maintain consistent data acquisition of

every fifteen seconds

End Program 

Yes

No

Write address to the EEPROM on the BASIC Stamp

Run the term232 program to save data into a file

Display the data showing the address as well as the values

Retrieve the data for the EEPROM

Pause

Is EEPOM ADDR>=max

EEPROM Address

End Program 

Yes

No

Post-Flight Program

Mechanical Design• Hexagonal Design• Extruded polystyrene rigid foam

insulation material

Mechanical DesignUnits in mm

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

Weight Budget

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 BudgetQuantity Description or Part Number Price Expected

Arrival

1 CD4011UBE $0.38 01 CD4049UBE $0.52 02 255-400SR12M-ROX $5.24 0

2 and 10 Precision resistor Z201 and capacitor E4941

$41.74 4/2

1 AD822ANZ $6.54 01 LM311N $0.56 01 MXO45T-3C-10M0000 $2.31 01 MCP23017-E/SP $1.44 02 SN74HC590AN $0.66 036 Energizer Ultimate Lithium AAA Batteries $80.1 4/2

1  Test Circuit PCB Board $170.00 4/2Total $309.49