Preliminary Critical Design Review Jason Mueller Jeff Weinell Brittany Dupre TEAM TOTAL RESISTANCE 1

 Mission Goal  Science Objectives  Science Background  Science Requirements  Technical Objectives  Technical Background  Technical Requirements  Principle of Operation  System Design  Sensors  Sensor Interface CONTENTS 2  Control Electronics  Power Budget  Flight Software  Reading and Writing Sensors  Thermal Design  Mechanical Design  Weight Budget  Risk Management  References  Questions

 Team Total Resistance will build a payload to measure Earth’s gravity field as a function of altitude for heights of up to 100,000 feet (30,480 meters), and compare our findings to theoretical and experimental high altitude gravity models. MISSION GOAL 3

 The payload shall take measurements in order to calculate relative gravitational acceleration changes to a minimum accuracy of meters per second- squared.  Team Total Resistance shall calculate relative gravitational acceleration for at least 100 points every 72 seconds (1.2 minutes) from ground level to 30,480 meters. SCIENCE REQUIREMENTS 4

PRINCIPLE OF OPERATION Figure 3. Spherical coordinates showing phi 5

SYSTEM DESIGN Figure 4. A diagram showing the functional groups and the interfaces that connect each functional group 6

SENSORS (LSM303DLM) Figure 5. LSM303DLM interface 7

PCA9515  Temperature (-40 to 85 degrees Celsius)  Supply voltage (+3 V) SENSOR INTERFACE Figure 6. PCA9515 interface 8

CONTROL ELECTRONICS Figure 7. Flight schematic 9

Table 1. BalloonSat power budget DeviceCurrentVoltage (V)mA/hr BalloonSat (microcontroller) 80 mA Total80 mA POWER BUDGET Table 2. Sensor power budget DeviceCurrentVoltage (V)mA/hr Accelerometer/ Magnetometer 360 µA+31.5 I 2 C-bus regulator2.3 mA+39.5 Total2.66 mA

Table 3. Data recorded per point ContentRequired BytesDescription three accelerometer axes 2 bytes per axiseach axis of the 3-axis accelerometer three magnetometer axes 2 bytes per axiseach axis of the 3-axis magnetometer RTC hour1 bytethe hour according to the RTC for each measurement RTC minute1 bytethe minute according to the RTC for each measurement RTC second1 bytethe second according to the RTC for each measurement Total15 bytes FLIGHT SOFTWARE 11

FLIGHT SOFTWARE Figure 8. Functional Flight Software 12

FLIGHT SOFTWARE Figure 8. Functional Flight Software 13

FLIGHT SOFTWARE Figure 8. Functional Flight Software 14

 Digital sensors connected to Pin 8 and Pin 9 of BalloonSat.  I2CIN and I2COUT commands to read and write data READING AND WRITING SENSORS 15 Figure 9. Reading and writing process

 The payload will be constructed of polystyrene foam of 1.9 cm thickness.  Polystyrene foam has a low heat transfer coefficient and is commonly used to insulate houses.  The payload will be constructed using polyethylene glue (Gorilla Glue ®).  As the glue dries, it expands to fill any gaps that may be present at polystyrene interfaces. THERMAL DESIGN 16

MECHANICAL DESIGN 17 Figure 10: Exploded view of the payload structure.

18 MECHANICAL DESIGN Figure 11. Foam shell (Assembly I) schematic

19 MECHANICAL DESIGN Figure 12. Foam Insert (Assembly II) schematic

20 MECHANICAL DESIGN Figure 13. Lid (Assembly III) schematic

MECHANICAL DESIGN Figure 14. Shows a section view of the payload structure with the foam insert supported within the foam shell.  A removable foam insert interfaces with the foam shell and the two foam supports.  The BalloonSat interfaces with face one.  The power unit interfaces with face two.  The sensing unit interfaces with face three. 21

Table 4. Weight Budget. ComponentWeight Approximation (grams) Payload structure150 Threading holes4 Plastic straws2 Screws12 Wires8 BalloonSat62 Sensing Unit10 Power Unit200 Total448 WEIGHT BUDGET 22

QUESTIONS? 23