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Thermal Vacuum Chamber Design

ANSYSCATIAHeat Transfer

We constructed a quadcopter using an Arduino Uno microcontroller and off-the-shelf components for demonstration at MechTRIX-X. We implemented PID control algorithms for roll and pitch stabilization and systematically tuned the control parameters to achieve a stable hover. The quadcopter was successfully demonstrated at MechTRIX-X, showcasing the integration of embedded programming, control theory, and mechanical design principles.

Thermal Vacuum Chamber Design

Thermal Vacuum Chamber (TVC) Design

As part of capacity-building efforts for satellite testing infrastructure in Nepal, I contributed to the preliminary design of a Thermal Vacuum Chamber (TVC) intended for environmental qualification testing of CubeSats up to 6U configuration.

A thermal vacuum chamber replicates the extreme vacuum and thermal conditions encountered in low Earth orbit. The objective of this project was to design a structurally sound, thermally capable, and economically feasible chamber suitable for small satellite validation within Nepal.

Project Objective

The primary goal was to develop a compact TVC capable of performing:

  • Thermal Vacuum Test (TVT)
  • Thermal Cycling Test
  • Thermal Balance Test

The system was designed to simulate:

  • Internal pressure: ~10⁻⁴ torr
  • Temperature range: −100°F to 220°F
  • External atmospheric pressure loading under vacuum conditions

System Architecture

The TVC was subdivided into three major subsystems:

  1. External Pressure Vessel
  2. Heating and Cooling System (Cryoshroud)
  3. Vacuum System

External Pressure Vessel Design

The chamber was designed as a cylindrical pressure vessel subjected to external atmospheric pressure, following ASME Boiler and Pressure Vessel Code (Section VIII).

Design Specifications:

  • Length: 900 mm
  • Diameter: 900 mm
  • Material: 304 Stainless Steel
  • Modulus of Elasticity: 193 GPa
  • Compressive Strength: 205–310 MPa

Thickness calculations were performed iteratively under three configurations:

  • Without reinforcement
  • With one reinforcement
  • With two reinforcements

A thickness of 2 mm was determined to safely withstand the design pressure.

Pressure Vessel CAD Model

Fig: CAD model of cylindrical pressure vessel subjected to external atmospheric pressure.

Head Selection and Structural Validation

Three head configurations were analyzed:

  • Flat head
  • Spherical head
  • Tori-spherical head

Finite Element Analysis (FEA) was conducted in ANSYS Mechanical.

Results showed:

  • Flat and spherical heads failed at shell intersection
  • Tori-spherical head exhibited maximum Von Mises stress of 143.98 MPa
  • Maximum deformation: 0.448 mm
  • Full assembly deformation (with cutouts): 0.536 mm

The tori-spherical head was selected due to its superior structural integrity under external pressure loading.

FEA Analysis of Pressure Vessel

Fig: Finite Element Analysis showing stress distribution under external pressure.

Heating and Cooling System (Cryoshroud Design)

To simulate orbital thermal conditions, an internal cryoshroud system was developed.

Heating System

  • Conductive heating selected for simplicity
  • Three 475 W strip heaters (240V)
  • Copper platen for uniform heat distribution
  • K-type thermocouples for feedback control

A closed-loop temperature control strategy was proposed for automated regulation.

Cooling System

Radiative cooling was implemented using liquid nitrogen circulation.

Two design concepts were evaluated:

  • Helical pipe configuration
  • Multi-circular loop configuration

The circular pipe design was selected for ease of manufacturability and integration.

Final Cryoshroud Parameters:

  • Radius: 350 mm
  • Length: 850 mm
  • Aluminum alloy thermal shroud
Cryoshroud CAD Model

Fig: CAD model of cryoshroud assembly for heating and radiative cooling simulation.

Thermal Analysis

Steady-state thermal analysis was conducted in ANSYS.

Modeling included:

  • Conductive heat transfer (heater to satellite)
  • Radiative cooling (shroud to satellite)
  • Thermal emission between components

Simulation results demonstrated achievable surface temperatures up to 46°C on the satellite model, validating heating system feasibility.

Vacuum System Design

The vacuum system was designed to achieve required low-pressure conditions using:

  • Roughing pump
  • Turbo pump
  • Vacuum gauges
  • Isolation valves
  • Residual Gas Analyzer (RGA)

Engineering Contributions

This project demonstrates:

  • Pressure vessel design under external loading (ASME methodology)
  • Head configuration comparison and FEA validation
  • Integrated thermal system design (heating + LN2 cooling)
  • Cryoshroud structural and thermal modeling
  • Vacuum system architecture planning
  • CAD modeling in CATIA
  • Structural and thermal simulation in ANSYS

The proposed TVC design represents an important step toward establishing indigenous satellite environmental testing capability within Nepal.