Wireless Thermal Protection Sensors
Presented By:Jesse Pentzer and Lucas Wells
Brandy Holmes John Sochacki Chris Johnson
• Introduction• Motivation• Prototype• Prototype Specs• Software• X-Jet Testing
Outline
• X-Jet Results• VAST Flight• VAST Results• Challenges• Conclusion
Project Goal: Design and build a wireless system to gather data from sensors embedded in the thermal protection system of re-entry probes.
• Project began in 2006 with team ThermaSense• ThermaSense developed proof of concept• Thermal Exposure developed the ThermaSense
system further, moving toward flight testing
Introduction
• Multi-nodal system• Multiple sensor types• Gather data during NASA Ames X-Jet tests
from multiple nodes• Integrate with VAST to log data on successful
high altitude balloon flight
Project Goals
Sensor Node:• PIC Microcontroller• Wireless ZigBee RF Transceiver (UART)• Absolute Pressure Sensor (I2C)• Cold Junction Correction Chips (SPI)
– converts thermocouple voltage to a digital temperature value
Data Storage Node:– Rabbit RCM3365 with 128 MB Flash Card
• Expandable architecture
Prototype
Multi-nodal 3 sensor nodesData Refresh Rate 1 HzNode Size 2” x 1.6 “ x 0.75 “Sensor Temp. Range -60 to 1000 °CBoard Temp. Range -40 to 125 °CPressure Range 0 to 15 psiComm. Frequency 2.4 GHz
Prototype Specs
Software
• Wireless Star Network Topology
• Master-Slave Polling Scheme
• Multiple-Point Data Check
• Real-Time Data Monitoring
• Data Download – TCP/IP Interface
Central Data Storage Node
(Master)
Sensor Node
(Slave)
Sensor Node
(Slave)
Sensor Node
(Slave)
Computer
X-Jet Testing
•Test multiple sensor types•Test multiple transmitting nodes•Collect pressure data inside chamber•Measure temperature gradient in TPS
X-Jet Results•Data matched control data from Ames data acquisition system•Received data from multiple nodes during testing•Obtained pressure data during X-Jet operation
• Next step towards flight readiness• Test of system functionality• Collect pressure data for VAST
VAST Flight
»Sensor Nodes
• No data has been retrieved from flash memory due to data corruption– Balloon rose slower than expected,
causing it to land in a remote area– Battery power died in the middle of a flash
write cycle leading to data corruption
• Solution: Next flight needs to have a timer implemented to stop writing data to memory before the power dissipates
VAST Results
• Programming complexity– Creating software libraries from scratch– No debugging equipment– Controlling the advanced ZigBee options– Integrating code from other sources
• Integration with VAST• Scope was too broad in initial problem
statement
Challenges
• Expanded upon previous year– Multi-nodal system– Multiple sensor types– Stand alone data storage
• Successful initial system testing in X-Jet• VAST flight provided valuable lessons learned• Next Step: Design and integration with re-
entry platform
Conclusion