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 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 ComponentCurrent (mA)Charge (mA-hours) BalloonSat Comparator624 Flipflop Clock25100 Counter Counter I/O Expander Total Needed

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 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-Subroutines Get_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 I 2 COUT command Return I 2 CIN command Enter DO loop Pause Return Pause I 2 COUT 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 I 2 CIN 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 ComponentsWeight Approximation Payload Structure130g BalloonSat Circuit Board70g Testing Circuit Board70g Batteries115g Supports30g Total 415g

Risk Management