Speed of Sound Experiment CDR Team BalloonWorks March 29 th, 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

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 Design Units 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) Supports60g +/- 5g (Approximated) Total470g 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

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 5Fresh batteries installation and perform voltage checks 5Load preflight and flight software 5Secure test circuit and BalloonSat slider to the payload 10Close 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 QuantityDescription or Part NumberPriceExpected Arrival 1CD4011UBE$ CD4049UBE$ SR12M-ROX$ and 10Precision resistor Z201 and capacitor E4941 $41.744/2 1AD822ANZ$ LM311N$ MXO45T-3C-10M0000$ MCP23017-E/SP$ SN74HC590AN$ Energizer Ultimate Lithium AAA Batteries$80.14/2 1Test Circuit PCB Board$ /2 Total $309.49