thermal investigation for accurate temperature measurement

Thermal Investigation for Accurate Temperature Measurement

Team TCTJTruc Le

Cedric ToguemJonathan Newman

Overview•Mission Goal•Objectives•Science Background•Technical Background •Payload Design

• Electrical• Software

• Mechanical•Payload Development

Mission GoalThe goal is to determine why previous LaACES payloads failed to correctly measure temperature in comparison to NOAA.

ObjectivesMeasure the temperature inside and outside the boundary layerMeasure the temperature with different color coated temperature sensors.Measure the temperature on the inside and on the outside surfaces of the payload.Have the payload returns intact.

Temperature change in the Atmosphere

• Troposphere (0 to 12km) : lowermost atmosphere where temperature decreases from 30 to -80°C• Stratosphere (12 to 48km): second lowermost part of the atmosphere where temperature increases from -80 to 0°C

http://apollo.lsc.vsc.edu/classes/met130/notes/chapter1/vert_temp_all.html

Boundary LayerThin layer of fluid in contact with a solid

body that flows more slowly than the rest of the fluid

As the payload gains altitude in fluid air, the boundary layer around it will be affected by heat transfer processes

http://apollo.lsc.vsc.edu/classes/met130/notes/chapter1/vert_temp_all.html

Heat Transfer ModesHeat can be transferred in three

different ways:- Conduction- Convection- Radiation

http://blogs.saschina.org/morena01pd2016/files/2009/10/ccr.jpg

ConductionTransfer of thermal energy between

molecules due to temperature gradient

The energy flows from a region of higher temperature to a region of lower temperature

Convection

Movement of molecules within fluid

A shallow layer of air in contact with a hotter surface warms by conduction, acquires buoyancy and then rises

RadiationElectromagnetic radiation emitted from the

surface of an object in the form of heat due to the objects temperature

If an object is warmer than its surrounding environment, it will emit more radiation in the form of heat into the surrounding environment than it will absorb in order to attain thermal equilibrium

http://www.tsc.com/irgen/Image7.gif

Test 1: Radiation Test 1Radiation test:

Sun →Electromagnetic radiation → Space →Sensors

The test will consist of different color shielding to reflect the electromagnetic radiation from the sun

http://image.tutorvista.com/content/dispersion

Test 2: Radiation Test 2Radiation Test:The payload circuitry will emit radiation

to the sensor.Distance from the radiation source will

determine the amount of heat dissipated

http://images.google.com/imgres?imgurl=http://www.uos.harvard.edu/images/ehs/radiation

Test 3: Boundary Layer Test

Sensors are placed at different distance from the exterior surface of the payload

Determine how much effect the boundary layer has on the measured temperature

http://www.google.com/imgres?imgurl=http://www.engineering.leeds

Thermal Boundary Layer

Payload DesignPower Source

TemperatureSensorsOp AmpBalloonSat

CPU

Electrical Design

Power Supply

Sensors BallonSat

Electrical Design (lowest level)

Sensors

Sensor Interfacing

Power Supply

Sensors BalloonSat(ADC)Op-Amp0~800mV 2.5~3Vtemperature

5V DC

Sensor Interfacing

Flight Power Supply

12V battery

5V battery

Sensors Op - Amp BalloonSat

Flight power supply

Power BudgetComponent

Current (mA)

Duration (hrs.)

Capacity (mA-h)

BalloonSat 51 (measured)

4 275

RTDs (x7) 1 each (estimated)

4 28

Total 58 4 303

Flight SoftwarePre-Flight and During Flight

Sensor Data

Read

ADC

BalloonSat

Real Time Clock

Write

Read

Memory

Flight SoftwarePost-Flight:

Memory BalloonSat

Read Basic Stamp Editor

Excel

Flight SoftwareOnboard Flight Program:

LoopPause

Read

WriteEnd If/Then

Flight SoftwarePost Flight Program:

AnalyzeRead Transfer to Excel

Exterior Mechanical Design

Interior Mechanical Design

Weight BudgetComponent Weight (g)BalloonSat 66 (measured)Styrofoam Structure 150 (estimated)BalloonSat Styrofoam Attachments

25 (estimated)

Wiring 7.5 (estimated)Booms (if balsa) 3 (estimated)Booms (if plastic) 10 (estimated)Boom attachments 25 (estimated)Sensors 10(estimated)Total 289.5-296.5 +/- 25%

Payload Development PlanMechanical

◦Boom prototyping◦Attachment prototyping◦Impact test to find best design to

store components◦Maintain payload within regulation

Payload Development PlanElectrical

◦Determine best temperature sensor to use

◦Determine best batteries to use and its configuration

◦Design the circuitry of the system◦Determine how well the components

will function in flight climate◦Determine methods of calibration of

the sensors

Payload Development PlanSoftware

◦Determine best way to consume less power

◦Determine if extra memory will be needed and how to access it

◦Determine the timing sequence ◦Determine methods of calibration

Reference1. Clavius: Environment - heat transfer.

http://www.xmission.com/~jwindley/heatxfer.html. November 24, 2009

2. Anne E. Egger "Earth's Atmosphere: Composition and Structure," Visionlearning Vol. EAS 2003. http://www.visionlearning.com/library/module_viewer.php?mid=107

3. Sad Dr Rodrigue – Introduction to physical Geaography. http://www.csulb.edu/~rodrigue/geog140/lectures/thermalstructure.html

4. BASIC Stamp 2p 24-Pin Module. http://www.parallax.com/Store/Microcontrollers/BASICStampModules/tabid/134/ProductID/7/List/1/Default.aspx?SortField=UnitCost,ProductName. November 25, 2009

Questions?