Null Space Labs

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=====  Project Description  =====

In order to simulate the conditions of high altitude flight we must either buy or build our own thermal-vac chamber. Since commercial ones cost more than $10k, we will be designing, and building our own low cost thermal-vac chamber.


=====  Design  =====



====  Concept Overview  ====

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**Step 1**
{{:concept_1.jpg}}
  * Place electronic parts into the chamber, minimize thermal conduction (possibly hang parts with fishing strings)
  * Close the chamber
  * Purge the chamber with dry nitrogen, allow air inside to exit
  * Allow the chamber to consist of mostly dry nitrogen


**Step 2**
{{:concept_2.jpg}}
  * Close off all values to the chamber
  * Place dry ice around the chamber to cool the dry nitrogen and electronic parts through thermal convection
  * Measure temperature inside the chamber and the temperature of the electronic parts
  * Allow it to achieve -60C



**Step 3**
{{:concept_3.jpg}}
  * Open the value leading to the refrigerator pump
  * Pump the -60C dry nitrogen until the pressure is at 1010 Pa (pascals)  or 0.01atm (1% of pressure at sea level)  (estimate pressure at 100,000ft)
  * The chamber is now simulating the environment of 100,000 ft  (-60C and 1010 Pa)




====  Mechanical Overview  ====

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The Thermal Vacuum Chamber concept consists of single 1/4" thick aluminum tube with a 7.5" ID and 8.0" OD. We then place a 1/4" aluminum plate on one end and 1/2" acrylic on the other end. We will also add a hole on the bottom aluminum plate to allow wires to pass. All joints are sealed with low temperature liquid gasket.

Tubes available here: [[https://www.speedymetals.com/pc-4661-8371-8-od-x-250-wall-tube-6061-t6-aluminum.aspx|https://www.speedymetals.com/pc-4661-8371-8-od-x-250-wall-tube-6061-t6-aluminum.aspx]]


Conceptual drawings of the environmental test chamber:

{{:assm cyl.png?800}}






====  Mechanical Stress Analysis  ====

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The following is a stress analysis of one of the walls. It's fixed by the corners and a 14psi pressure load is applied to the wall (at room temperature). Results conclude that deflection is minimal, however more materials should be looked into. 

**Full analysis report:** 
Cylinder:  {{:cylinder-simulationxpress study-1.docx}}

Bottom Plate:  {{:bottom-simulationxpress study-1.docx}}


{{:displacement cylinder.png?800}}





=====  Electronics  =====

  * 6 Low Temperature Thermocouples
  * Pump Controller
  * Pressure Sensor



=====  Software  =====

  * None