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