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 100 400

Comparator 6 24

Flipflop 100 400

Clock 25 100

Counter 1 70 280

Counter 2 70 280

I/O Expander 125 500

Total 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-Routine

Counter 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 Approximation

Payload Structure 130g

BalloonSat Circuit Board 70g

Testing Circuit Board 70g

Batteries 115g

Supports 30g

Total 415g

Risk Management